Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

17 files changed, 9119 insertions, 0 deletions

diff --git a/mozglue/baseprofiler/lul/AutoObjectMapper.cpp b/mozglue/baseprofiler/lul/AutoObjectMapper.cpp
new file mode 100644
index 0000000000..0037c943aa
--- /dev/null
+++ b/mozglue/baseprofiler/lul/AutoObjectMapper.cpp
@@ -0,0 +1,80 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <sys/mman.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Sprintf.h"
+
+#include "BaseProfiler.h"
+#include "PlatformMacros.h"
+#include "AutoObjectMapper.h"
+
+// A helper function for creating failure error messages in
+// AutoObjectMapper*::Map.
+static void failedToMessage(void (*aLog)(const char*), const char* aHowFailed,
+                            std::string aFileName) {
+  char buf[300];
+  SprintfLiteral(buf, "AutoObjectMapper::Map: Failed to %s \'%s\'", aHowFailed,
+                 aFileName.c_str());
+  buf[sizeof(buf) - 1] = 0;
+  aLog(buf);
+}
+
+AutoObjectMapperPOSIX::AutoObjectMapperPOSIX(void (*aLog)(const char*))
+    : mImage(nullptr), mSize(0), mLog(aLog), mIsMapped(false) {}
+
+AutoObjectMapperPOSIX::~AutoObjectMapperPOSIX() {
+  if (!mIsMapped) {
+    // There's nothing to do.
+    MOZ_ASSERT(!mImage);
+    MOZ_ASSERT(mSize == 0);
+    return;
+  }
+  MOZ_ASSERT(mSize > 0);
+  // The following assertion doesn't necessarily have to be true,
+  // but we assume (reasonably enough) that no mmap facility would
+  // be crazy enough to map anything at page zero.
+  MOZ_ASSERT(mImage);
+  munmap(mImage, mSize);
+}
+
+bool AutoObjectMapperPOSIX::Map(/*OUT*/ void** start, /*OUT*/ size_t* length,
+                                std::string fileName) {
+  MOZ_ASSERT(!mIsMapped);
+
+  int fd = open(fileName.c_str(), O_RDONLY);
+  if (fd == -1) {
+    failedToMessage(mLog, "open", fileName);
+    return false;
+  }
+
+  struct stat st;
+  int err = fstat(fd, &st);
+  size_t sz = (err == 0) ? st.st_size : 0;
+  if (err != 0 || sz == 0) {
+    failedToMessage(mLog, "fstat", fileName);
+    close(fd);
+    return false;
+  }
+
+  void* image = mmap(nullptr, sz, PROT_READ, MAP_SHARED, fd, 0);
+  if (image == MAP_FAILED) {
+    failedToMessage(mLog, "mmap", fileName);
+    close(fd);
+    return false;
+  }
+
+  close(fd);
+  mIsMapped = true;
+  mImage = *start = image;
+  mSize = *length = sz;
+  return true;
+}
diff --git a/mozglue/baseprofiler/lul/AutoObjectMapper.h b/mozglue/baseprofiler/lul/AutoObjectMapper.h
new file mode 100644
index 0000000000..f63aa43e0e
--- /dev/null
+++ b/mozglue/baseprofiler/lul/AutoObjectMapper.h
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef AutoObjectMapper_h
+#define AutoObjectMapper_h
+
+#include <string>
+
+#include "mozilla/Attributes.h"
+#include "PlatformMacros.h"
+
+// A (nearly-) RAII class that maps an object in and then unmaps it on
+// destruction.  This base class version uses the "normal" POSIX
+// functions: open, fstat, close, mmap, munmap.
+
+class MOZ_STACK_CLASS AutoObjectMapperPOSIX {
+ public:
+  // The constructor does not attempt to map the file, because that
+  // might fail.  Instead, once the object has been constructed,
+  // call Map() to attempt the mapping.  There is no corresponding
+  // Unmap() since the unmapping is done in the destructor.  Failure
+  // messages are sent to |aLog|.
+  explicit AutoObjectMapperPOSIX(void (*aLog)(const char*));
+
+  // Unmap the file on destruction of this object.
+  ~AutoObjectMapperPOSIX();
+
+  // Map |fileName| into the address space and return the mapping
+  // extents.  If the file is zero sized this will fail.  The file is
+  // mapped read-only and private.  Returns true iff the mapping
+  // succeeded, in which case *start and *length hold its extent.
+  // Once a call to Map succeeds, all subsequent calls to it will
+  // fail.
+  bool Map(/*OUT*/ void** start, /*OUT*/ size_t* length, std::string fileName);
+
+ protected:
+  // If we are currently holding a mapped object, these record the
+  // mapped address range.
+  void* mImage;
+  size_t mSize;
+
+  // A logging sink, for complaining about mapping failures.
+  void (*mLog)(const char*);
+
+ private:
+  // Are we currently holding a mapped object?  This is private to
+  // the base class.  Derived classes need to have their own way to
+  // track whether they are holding a mapped object.
+  bool mIsMapped;
+
+  // Disable copying and assignment.
+  AutoObjectMapperPOSIX(const AutoObjectMapperPOSIX&);
+  AutoObjectMapperPOSIX& operator=(const AutoObjectMapperPOSIX&);
+  // Disable heap allocation of this class.
+  void* operator new(size_t);
+  void* operator new[](size_t);
+  void operator delete(void*);
+  void operator delete[](void*);
+};
+
+#endif  // AutoObjectMapper_h
diff --git a/mozglue/baseprofiler/lul/LulCommon.cpp b/mozglue/baseprofiler/lul/LulCommon.cpp
new file mode 100644
index 0000000000..f014892a57
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulCommon.cpp
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2011, 2013 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/module.cc
+//   src/common/unique_string.cc
+
+// There's no internal-only interface for LulCommon.  Hence include
+// the external interface directly.
+#include "LulCommonExt.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <string>
+#include <map>
+
+#include "BaseProfiler.h"
+
+namespace lul {
+
+using std::string;
+
+////////////////////////////////////////////////////////////////
+// Module
+//
+Module::Module(const string& name, const string& os, const string& architecture,
+               const string& id)
+    : name_(name), os_(os), architecture_(architecture), id_(id) {}
+
+Module::~Module() {}
+
+////////////////////////////////////////////////////////////////
+// UniqueString
+//
+class UniqueString {
+ public:
+  explicit UniqueString(string str) { str_ = strdup(str.c_str()); }
+  ~UniqueString() { free(reinterpret_cast<void*>(const_cast<char*>(str_))); }
+  const char* str_;
+};
+
+const char* FromUniqueString(const UniqueString* ustr) { return ustr->str_; }
+
+bool IsEmptyUniqueString(const UniqueString* ustr) {
+  return (ustr->str_)[0] == '\0';
+}
+
+////////////////////////////////////////////////////////////////
+// UniqueStringUniverse
+//
+UniqueStringUniverse::~UniqueStringUniverse() {
+  for (std::map<string, UniqueString*>::iterator it = map_.begin();
+       it != map_.end(); it++) {
+    delete it->second;
+  }
+}
+
+const UniqueString* UniqueStringUniverse::ToUniqueString(string str) {
+  std::map<string, UniqueString*>::iterator it = map_.find(str);
+  if (it == map_.end()) {
+    UniqueString* ustr = new UniqueString(str);
+    map_[str] = ustr;
+    return ustr;
+  } else {
+    return it->second;
+  }
+}
+
+}  // namespace lul
diff --git a/mozglue/baseprofiler/lul/LulCommonExt.h b/mozglue/baseprofiler/lul/LulCommonExt.h
new file mode 100644
index 0000000000..b20a7321ff
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulCommonExt.h
@@ -0,0 +1,509 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2006, 2010, 2012, 2013 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// module.h: Define google_breakpad::Module. A Module holds debugging
+// information, and can write that information out as a Breakpad
+// symbol file.
+
+//  (C) Copyright Greg Colvin and Beman Dawes 1998, 1999.
+//  Copyright (c) 2001, 2002 Peter Dimov
+//
+//  Permission to copy, use, modify, sell and distribute this software
+//  is granted provided this copyright notice appears in all copies.
+//  This software is provided "as is" without express or implied
+//  warranty, and with no claim as to its suitability for any purpose.
+//
+//  See http://www.boost.org/libs/smart_ptr/scoped_ptr.htm for documentation.
+//
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/unique_string.h
+//   src/common/scoped_ptr.h
+//   src/common/module.h
+
+// External interface for the "Common" component of LUL.
+
+#ifndef LulCommonExt_h
+#define LulCommonExt_h
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include <string>
+#include <map>
+#include <vector>
+#include <cstddef>  // for std::ptrdiff_t
+
+#include "mozilla/Assertions.h"
+
+namespace lul {
+
+using std::map;
+using std::string;
+
+////////////////////////////////////////////////////////////////
+// UniqueString
+//
+
+// Abstract type
+class UniqueString;
+
+// Get the contained C string (debugging only)
+const char* FromUniqueString(const UniqueString*);
+
+// Is the given string empty (that is, "") ?
+bool IsEmptyUniqueString(const UniqueString*);
+
+////////////////////////////////////////////////////////////////
+// UniqueStringUniverse
+//
+
+// All UniqueStrings live in some specific UniqueStringUniverse.
+class UniqueStringUniverse {
+ public:
+  UniqueStringUniverse() {}
+  ~UniqueStringUniverse();
+  // Convert a |string| to a UniqueString, that lives in this universe.
+  const UniqueString* ToUniqueString(string str);
+
+ private:
+  map<string, UniqueString*> map_;
+};
+
+////////////////////////////////////////////////////////////////
+// GUID
+//
+
+typedef struct {
+  uint32_t data1;
+  uint16_t data2;
+  uint16_t data3;
+  uint8_t data4[8];
+} MDGUID;  // GUID
+
+typedef MDGUID GUID;
+
+////////////////////////////////////////////////////////////////
+// scoped_ptr
+//
+
+//  scoped_ptr mimics a built-in pointer except that it guarantees deletion
+//  of the object pointed to, either on destruction of the scoped_ptr or via
+//  an explicit reset(). scoped_ptr is a simple solution for simple needs;
+//  use shared_ptr or std::auto_ptr if your needs are more complex.
+
+//  *** NOTE ***
+//  If your scoped_ptr is a class member of class FOO pointing to a
+//  forward declared type BAR (as shown below), then you MUST use a non-inlined
+//  version of the destructor.  The destructor of a scoped_ptr (called from
+//  FOO's destructor) must have a complete definition of BAR in order to
+//  destroy it.  Example:
+//
+//  -- foo.h --
+//  class BAR;
+//
+//  class FOO {
+//   public:
+//    FOO();
+//    ~FOO();  // Required for sources that instantiate class FOO to compile!
+//
+//   private:
+//    scoped_ptr<BAR> bar_;
+//  };
+//
+//  -- foo.cc --
+//  #include "foo.h"
+//  FOO::~FOO() {} // Empty, but must be non-inlined to FOO's class definition.
+
+//  scoped_ptr_malloc added by Google
+//  When one of these goes out of scope, instead of doing a delete or
+//  delete[], it calls free().  scoped_ptr_malloc<char> is likely to see
+//  much more use than any other specializations.
+
+//  release() added by Google
+//  Use this to conditionally transfer ownership of a heap-allocated object
+//  to the caller, usually on method success.
+
+template <typename T>
+class scoped_ptr {
+ private:
+  T* ptr;
+
+  scoped_ptr(scoped_ptr const&);
+  scoped_ptr& operator=(scoped_ptr const&);
+
+ public:
+  typedef T element_type;
+
+  explicit scoped_ptr(T* p = 0) : ptr(p) {}
+
+  ~scoped_ptr() { delete ptr; }
+
+  void reset(T* p = 0) {
+    if (ptr != p) {
+      delete ptr;
+      ptr = p;
+    }
+  }
+
+  T& operator*() const {
+    MOZ_ASSERT(ptr != 0);
+    return *ptr;
+  }
+
+  T* operator->() const {
+    MOZ_ASSERT(ptr != 0);
+    return ptr;
+  }
+
+  bool operator==(T* p) const { return ptr == p; }
+
+  bool operator!=(T* p) const { return ptr != p; }
+
+  T* get() const { return ptr; }
+
+  void swap(scoped_ptr& b) {
+    T* tmp = b.ptr;
+    b.ptr = ptr;
+    ptr = tmp;
+  }
+
+  T* release() {
+    T* tmp = ptr;
+    ptr = 0;
+    return tmp;
+  }
+
+ private:
+  // no reason to use these: each scoped_ptr should have its own object
+  template <typename U>
+  bool operator==(scoped_ptr<U> const& p) const;
+  template <typename U>
+  bool operator!=(scoped_ptr<U> const& p) const;
+};
+
+template <typename T>
+inline void swap(scoped_ptr<T>& a, scoped_ptr<T>& b) {
+  a.swap(b);
+}
+
+template <typename T>
+inline bool operator==(T* p, const scoped_ptr<T>& b) {
+  return p == b.get();
+}
+
+template <typename T>
+inline bool operator!=(T* p, const scoped_ptr<T>& b) {
+  return p != b.get();
+}
+
+//  scoped_array extends scoped_ptr to arrays. Deletion of the array pointed to
+//  is guaranteed, either on destruction of the scoped_array or via an explicit
+//  reset(). Use shared_array or std::vector if your needs are more complex.
+
+template <typename T>
+class scoped_array {
+ private:
+  T* ptr;
+
+  scoped_array(scoped_array const&);
+  scoped_array& operator=(scoped_array const&);
+
+ public:
+  typedef T element_type;
+
+  explicit scoped_array(T* p = 0) : ptr(p) {}
+
+  ~scoped_array() { delete[] ptr; }
+
+  void reset(T* p = 0) {
+    if (ptr != p) {
+      delete[] ptr;
+      ptr = p;
+    }
+  }
+
+  T& operator[](std::ptrdiff_t i) const {
+    MOZ_ASSERT(ptr != 0);
+    MOZ_ASSERT(i >= 0);
+    return ptr[i];
+  }
+
+  bool operator==(T* p) const { return ptr == p; }
+
+  bool operator!=(T* p) const { return ptr != p; }
+
+  T* get() const { return ptr; }
+
+  void swap(scoped_array& b) {
+    T* tmp = b.ptr;
+    b.ptr = ptr;
+    ptr = tmp;
+  }
+
+  T* release() {
+    T* tmp = ptr;
+    ptr = 0;
+    return tmp;
+  }
+
+ private:
+  // no reason to use these: each scoped_array should have its own object
+  template <typename U>
+  bool operator==(scoped_array<U> const& p) const;
+  template <typename U>
+  bool operator!=(scoped_array<U> const& p) const;
+};
+
+template <class T>
+inline void swap(scoped_array<T>& a, scoped_array<T>& b) {
+  a.swap(b);
+}
+
+template <typename T>
+inline bool operator==(T* p, const scoped_array<T>& b) {
+  return p == b.get();
+}
+
+template <typename T>
+inline bool operator!=(T* p, const scoped_array<T>& b) {
+  return p != b.get();
+}
+
+// This class wraps the c library function free() in a class that can be
+// passed as a template argument to scoped_ptr_malloc below.
+class ScopedPtrMallocFree {
+ public:
+  inline void operator()(void* x) const { free(x); }
+};
+
+// scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
+// second template argument, the functor used to free the object.
+
+template <typename T, typename FreeProc = ScopedPtrMallocFree>
+class scoped_ptr_malloc {
+ private:
+  T* ptr;
+
+  scoped_ptr_malloc(scoped_ptr_malloc const&);
+  scoped_ptr_malloc& operator=(scoped_ptr_malloc const&);
+
+ public:
+  typedef T element_type;
+
+  explicit scoped_ptr_malloc(T* p = 0) : ptr(p) {}
+
+  ~scoped_ptr_malloc() { free_((void*)ptr); }
+
+  void reset(T* p = 0) {
+    if (ptr != p) {
+      free_((void*)ptr);
+      ptr = p;
+    }
+  }
+
+  T& operator*() const {
+    MOZ_ASSERT(ptr != 0);
+    return *ptr;
+  }
+
+  T* operator->() const {
+    MOZ_ASSERT(ptr != 0);
+    return ptr;
+  }
+
+  bool operator==(T* p) const { return ptr == p; }
+
+  bool operator!=(T* p) const { return ptr != p; }
+
+  T* get() const { return ptr; }
+
+  void swap(scoped_ptr_malloc& b) {
+    T* tmp = b.ptr;
+    b.ptr = ptr;
+    ptr = tmp;
+  }
+
+  T* release() {
+    T* tmp = ptr;
+    ptr = 0;
+    return tmp;
+  }
+
+ private:
+  // no reason to use these: each scoped_ptr_malloc should have its own object
+  template <typename U, typename GP>
+  bool operator==(scoped_ptr_malloc<U, GP> const& p) const;
+  template <typename U, typename GP>
+  bool operator!=(scoped_ptr_malloc<U, GP> const& p) const;
+
+  static FreeProc const free_;
+};
+
+template <typename T, typename FP>
+FP const scoped_ptr_malloc<T, FP>::free_ = FP();
+
+template <typename T, typename FP>
+inline void swap(scoped_ptr_malloc<T, FP>& a, scoped_ptr_malloc<T, FP>& b) {
+  a.swap(b);
+}
+
+template <typename T, typename FP>
+inline bool operator==(T* p, const scoped_ptr_malloc<T, FP>& b) {
+  return p == b.get();
+}
+
+template <typename T, typename FP>
+inline bool operator!=(T* p, const scoped_ptr_malloc<T, FP>& b) {
+  return p != b.get();
+}
+
+////////////////////////////////////////////////////////////////
+// Module
+//
+
+// A Module represents the contents of a module, and supports methods
+// for adding information produced by parsing STABS or DWARF data
+// --- possibly both from the same file --- and then writing out the
+// unified contents as a Breakpad-format symbol file.
+class Module {
+ public:
+  // The type of addresses and sizes in a symbol table.
+  typedef uint64_t Address;
+
+  // Representation of an expression.  This can either be a postfix
+  // expression, in which case it is stored as a string, or a simple
+  // expression of the form (identifier + imm) or *(identifier + imm).
+  // It can also be invalid (denoting "no value").
+  enum ExprHow { kExprInvalid = 1, kExprPostfix, kExprSimple, kExprSimpleMem };
+
+  struct Expr {
+    // Construct a simple-form expression
+    Expr(const UniqueString* ident, long offset, bool deref) {
+      if (IsEmptyUniqueString(ident)) {
+        Expr();
+      } else {
+        postfix_ = "";
+        ident_ = ident;
+        offset_ = offset;
+        how_ = deref ? kExprSimpleMem : kExprSimple;
+      }
+    }
+
+    // Construct an invalid expression
+    Expr() {
+      postfix_ = "";
+      ident_ = nullptr;
+      offset_ = 0;
+      how_ = kExprInvalid;
+    }
+
+    // Return the postfix expression string, either directly,
+    // if this is a postfix expression, or by synthesising it
+    // for a simple expression.
+    std::string getExprPostfix() const {
+      switch (how_) {
+        case kExprPostfix:
+          return postfix_;
+        case kExprSimple:
+        case kExprSimpleMem: {
+          char buf[40];
+          sprintf(buf, " %ld %c%s", labs(offset_), offset_ < 0 ? '-' : '+',
+                  how_ == kExprSimple ? "" : " ^");
+          return std::string(FromUniqueString(ident_)) + std::string(buf);
+        }
+        case kExprInvalid:
+        default:
+          MOZ_ASSERT(0 && "getExprPostfix: invalid Module::Expr type");
+          return "Expr::genExprPostfix: kExprInvalid";
+      }
+    }
+
+    // The identifier that gives the starting value for simple expressions.
+    const UniqueString* ident_;
+    // The offset to add for simple expressions.
+    long offset_;
+    // The Postfix expression string to evaluate for non-simple expressions.
+    std::string postfix_;
+    // The operation expressed by this expression.
+    ExprHow how_;
+  };
+
+  // A map from register names to expressions that recover
+  // their values. This can represent a complete set of rules to
+  // follow at some address, or a set of changes to be applied to an
+  // extant set of rules.
+  // NOTE! there are two completely different types called RuleMap.  This
+  // is one of them.
+  typedef std::map<const UniqueString*, Expr> RuleMap;
+
+  // A map from addresses to RuleMaps, representing changes that take
+  // effect at given addresses.
+  typedef std::map<Address, RuleMap> RuleChangeMap;
+
+  // A range of 'STACK CFI' stack walking information. An instance of
+  // this structure corresponds to a 'STACK CFI INIT' record and the
+  // subsequent 'STACK CFI' records that fall within its range.
+  struct StackFrameEntry {
+    // The starting address and number of bytes of machine code this
+    // entry covers.
+    Address address, size;
+
+    // The initial register recovery rules, in force at the starting
+    // address.
+    RuleMap initial_rules;
+
+    // A map from addresses to rule changes. To find the rules in
+    // force at a given address, start with initial_rules, and then
+    // apply the changes given in this map for all addresses up to and
+    // including the address you're interested in.
+    RuleChangeMap rule_changes;
+  };
+
+  // Create a new module with the given name, operating system,
+  // architecture, and ID string.
+  Module(const std::string& name, const std::string& os,
+         const std::string& architecture, const std::string& id);
+  ~Module();
+
+ private:
+  // Module header entries.
+  std::string name_, os_, architecture_, id_;
+};
+
+}  // namespace lul
+
+#endif  // LulCommonExt_h
diff --git a/mozglue/baseprofiler/lul/LulDwarf.cpp b/mozglue/baseprofiler/lul/LulDwarf.cpp
new file mode 100644
index 0000000000..c83296fc62
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulDwarf.cpp
@@ -0,0 +1,2252 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2010 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// CFI reader author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// Implementation of dwarf2reader::LineInfo, dwarf2reader::CompilationUnit,
+// and dwarf2reader::CallFrameInfo. See dwarf2reader.h for details.
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/dwarf/bytereader.cc
+//   src/common/dwarf/dwarf2reader.cc
+//   src/common/dwarf_cfi_to_module.cc
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <map>
+#include <stack>
+#include <string>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Sprintf.h"
+
+#include "LulCommonExt.h"
+#include "LulDwarfInt.h"
+
+// Set this to 1 for verbose logging
+#define DEBUG_DWARF 0
+
+namespace lul {
+
+using std::string;
+
+ByteReader::ByteReader(enum Endianness endian)
+    : offset_reader_(NULL),
+      address_reader_(NULL),
+      endian_(endian),
+      address_size_(0),
+      offset_size_(0),
+      have_section_base_(),
+      have_text_base_(),
+      have_data_base_(),
+      have_function_base_() {}
+
+ByteReader::~ByteReader() {}
+
+void ByteReader::SetOffsetSize(uint8 size) {
+  offset_size_ = size;
+  MOZ_ASSERT(size == 4 || size == 8);
+  if (size == 4) {
+    this->offset_reader_ = &ByteReader::ReadFourBytes;
+  } else {
+    this->offset_reader_ = &ByteReader::ReadEightBytes;
+  }
+}
+
+void ByteReader::SetAddressSize(uint8 size) {
+  address_size_ = size;
+  MOZ_ASSERT(size == 4 || size == 8);
+  if (size == 4) {
+    this->address_reader_ = &ByteReader::ReadFourBytes;
+  } else {
+    this->address_reader_ = &ByteReader::ReadEightBytes;
+  }
+}
+
+uint64 ByteReader::ReadInitialLength(const char* start, size_t* len) {
+  const uint64 initial_length = ReadFourBytes(start);
+  start += 4;
+
+  // In DWARF2/3, if the initial length is all 1 bits, then the offset
+  // size is 8 and we need to read the next 8 bytes for the real length.
+  if (initial_length == 0xffffffff) {
+    SetOffsetSize(8);
+    *len = 12;
+    return ReadOffset(start);
+  } else {
+    SetOffsetSize(4);
+    *len = 4;
+  }
+  return initial_length;
+}
+
+bool ByteReader::ValidEncoding(DwarfPointerEncoding encoding) const {
+  if (encoding == DW_EH_PE_omit) return true;
+  if (encoding == DW_EH_PE_aligned) return true;
+  if ((encoding & 0x7) > DW_EH_PE_udata8) return false;
+  if ((encoding & 0x70) > DW_EH_PE_funcrel) return false;
+  return true;
+}
+
+bool ByteReader::UsableEncoding(DwarfPointerEncoding encoding) const {
+  switch (encoding & 0x70) {
+    case DW_EH_PE_absptr:
+      return true;
+    case DW_EH_PE_pcrel:
+      return have_section_base_;
+    case DW_EH_PE_textrel:
+      return have_text_base_;
+    case DW_EH_PE_datarel:
+      return have_data_base_;
+    case DW_EH_PE_funcrel:
+      return have_function_base_;
+    default:
+      return false;
+  }
+}
+
+uint64 ByteReader::ReadEncodedPointer(const char* buffer,
+                                      DwarfPointerEncoding encoding,
+                                      size_t* len) const {
+  // UsableEncoding doesn't approve of DW_EH_PE_omit, so we shouldn't
+  // see it here.
+  MOZ_ASSERT(encoding != DW_EH_PE_omit);
+
+  // The Linux Standards Base 4.0 does not make this clear, but the
+  // GNU tools (gcc/unwind-pe.h; readelf/dwarf.c; gdb/dwarf2-frame.c)
+  // agree that aligned pointers are always absolute, machine-sized,
+  // machine-signed pointers.
+  if (encoding == DW_EH_PE_aligned) {
+    MOZ_ASSERT(have_section_base_);
+
+    // We don't need to align BUFFER in *our* address space. Rather, we
+    // need to find the next position in our buffer that would be aligned
+    // when the .eh_frame section the buffer contains is loaded into the
+    // program's memory. So align assuming that buffer_base_ gets loaded at
+    // address section_base_, where section_base_ itself may or may not be
+    // aligned.
+
+    // First, find the offset to START from the closest prior aligned
+    // address.
+    uint64 skew = section_base_ & (AddressSize() - 1);
+    // Now find the offset from that aligned address to buffer.
+    uint64 offset = skew + (buffer - buffer_base_);
+    // Round up to the next boundary.
+    uint64 aligned = (offset + AddressSize() - 1) & -AddressSize();
+    // Convert back to a pointer.
+    const char* aligned_buffer = buffer_base_ + (aligned - skew);
+    // Finally, store the length and actually fetch the pointer.
+    *len = aligned_buffer - buffer + AddressSize();
+    return ReadAddress(aligned_buffer);
+  }
+
+  // Extract the value first, ignoring whether it's a pointer or an
+  // offset relative to some base.
+  uint64 offset;
+  switch (encoding & 0x0f) {
+    case DW_EH_PE_absptr:
+      // DW_EH_PE_absptr is weird, as it is used as a meaningful value for
+      // both the high and low nybble of encoding bytes. When it appears in
+      // the high nybble, it means that the pointer is absolute, not an
+      // offset from some base address. When it appears in the low nybble,
+      // as here, it means that the pointer is stored as a normal
+      // machine-sized and machine-signed address. A low nybble of
+      // DW_EH_PE_absptr does not imply that the pointer is absolute; it is
+      // correct for us to treat the value as an offset from a base address
+      // if the upper nybble is not DW_EH_PE_absptr.
+      offset = ReadAddress(buffer);
+      *len = AddressSize();
+      break;
+
+    case DW_EH_PE_uleb128:
+      offset = ReadUnsignedLEB128(buffer, len);
+      break;
+
+    case DW_EH_PE_udata2:
+      offset = ReadTwoBytes(buffer);
+      *len = 2;
+      break;
+
+    case DW_EH_PE_udata4:
+      offset = ReadFourBytes(buffer);
+      *len = 4;
+      break;
+
+    case DW_EH_PE_udata8:
+      offset = ReadEightBytes(buffer);
+      *len = 8;
+      break;
+
+    case DW_EH_PE_sleb128:
+      offset = ReadSignedLEB128(buffer, len);
+      break;
+
+    case DW_EH_PE_sdata2:
+      offset = ReadTwoBytes(buffer);
+      // Sign-extend from 16 bits.
+      offset = (offset ^ 0x8000) - 0x8000;
+      *len = 2;
+      break;
+
+    case DW_EH_PE_sdata4:
+      offset = ReadFourBytes(buffer);
+      // Sign-extend from 32 bits.
+      offset = (offset ^ 0x80000000ULL) - 0x80000000ULL;
+      *len = 4;
+      break;
+
+    case DW_EH_PE_sdata8:
+      // No need to sign-extend; this is the full width of our type.
+      offset = ReadEightBytes(buffer);
+      *len = 8;
+      break;
+
+    default:
+      abort();
+  }
+
+  // Find the appropriate base address.
+  uint64 base;
+  switch (encoding & 0x70) {
+    case DW_EH_PE_absptr:
+      base = 0;
+      break;
+
+    case DW_EH_PE_pcrel:
+      MOZ_ASSERT(have_section_base_);
+      base = section_base_ + (buffer - buffer_base_);
+      break;
+
+    case DW_EH_PE_textrel:
+      MOZ_ASSERT(have_text_base_);
+      base = text_base_;
+      break;
+
+    case DW_EH_PE_datarel:
+      MOZ_ASSERT(have_data_base_);
+      base = data_base_;
+      break;
+
+    case DW_EH_PE_funcrel:
+      MOZ_ASSERT(have_function_base_);
+      base = function_base_;
+      break;
+
+    default:
+      abort();
+  }
+
+  uint64 pointer = base + offset;
+
+  // Remove inappropriate upper bits.
+  if (AddressSize() == 4)
+    pointer = pointer & 0xffffffff;
+  else
+    MOZ_ASSERT(AddressSize() == sizeof(uint64));
+
+  return pointer;
+}
+
+// A DWARF rule for recovering the address or value of a register, or
+// computing the canonical frame address. There is one subclass of this for
+// each '*Rule' member function in CallFrameInfo::Handler.
+//
+// It's annoying that we have to handle Rules using pointers (because
+// the concrete instances can have an arbitrary size). They're small,
+// so it would be much nicer if we could just handle them by value
+// instead of fretting about ownership and destruction.
+//
+// It seems like all these could simply be instances of std::tr1::bind,
+// except that we need instances to be EqualityComparable, too.
+//
+// This could logically be nested within State, but then the qualified names
+// get horrendous.
+class CallFrameInfo::Rule {
+ public:
+  virtual ~Rule() {}
+
+  // Tell HANDLER that, at ADDRESS in the program, REG can be
+  // recovered using this rule. If REG is kCFARegister, then this rule
+  // describes how to compute the canonical frame address. Return what the
+  // HANDLER member function returned.
+  virtual bool Handle(Handler* handler, uint64 address, int reg) const = 0;
+
+  // Equality on rules. We use these to decide which rules we need
+  // to report after a DW_CFA_restore_state instruction.
+  virtual bool operator==(const Rule& rhs) const = 0;
+
+  bool operator!=(const Rule& rhs) const { return !(*this == rhs); }
+
+  // Return a pointer to a copy of this rule.
+  virtual Rule* Copy() const = 0;
+
+  // If this is a base+offset rule, change its base register to REG.
+  // Otherwise, do nothing. (Ugly, but required for DW_CFA_def_cfa_register.)
+  virtual void SetBaseRegister(unsigned reg) {}
+
+  // If this is a base+offset rule, change its offset to OFFSET. Otherwise,
+  // do nothing. (Ugly, but required for DW_CFA_def_cfa_offset.)
+  virtual void SetOffset(long long offset) {}
+
+  // A RTTI workaround, to make it possible to implement equality
+  // comparisons on classes derived from this one.
+  enum CFIRTag {
+    CFIR_UNDEFINED_RULE,
+    CFIR_SAME_VALUE_RULE,
+    CFIR_OFFSET_RULE,
+    CFIR_VAL_OFFSET_RULE,
+    CFIR_REGISTER_RULE,
+    CFIR_EXPRESSION_RULE,
+    CFIR_VAL_EXPRESSION_RULE
+  };
+
+  // Produce the tag that identifies the child class of this object.
+  virtual CFIRTag getTag() const = 0;
+};
+
+// Rule: the value the register had in the caller cannot be recovered.
+class CallFrameInfo::UndefinedRule : public CallFrameInfo::Rule {
+ public:
+  UndefinedRule() {}
+  ~UndefinedRule() {}
+  CFIRTag getTag() const override { return CFIR_UNDEFINED_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->UndefinedRule(address, reg);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_UNDEFINED_RULE) return false;
+    return true;
+  }
+  Rule* Copy() const override { return new UndefinedRule(*this); }
+};
+
+// Rule: the register's value is the same as that it had in the caller.
+class CallFrameInfo::SameValueRule : public CallFrameInfo::Rule {
+ public:
+  SameValueRule() {}
+  ~SameValueRule() {}
+  CFIRTag getTag() const override { return CFIR_SAME_VALUE_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->SameValueRule(address, reg);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_SAME_VALUE_RULE) return false;
+    return true;
+  }
+  Rule* Copy() const override { return new SameValueRule(*this); }
+};
+
+// Rule: the register is saved at OFFSET from BASE_REGISTER.  BASE_REGISTER
+// may be CallFrameInfo::Handler::kCFARegister.
+class CallFrameInfo::OffsetRule : public CallFrameInfo::Rule {
+ public:
+  OffsetRule(int base_register, long offset)
+      : base_register_(base_register), offset_(offset) {}
+  ~OffsetRule() {}
+  CFIRTag getTag() const override { return CFIR_OFFSET_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->OffsetRule(address, reg, base_register_, offset_);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_OFFSET_RULE) return false;
+    const OffsetRule* our_rhs = static_cast<const OffsetRule*>(&rhs);
+    return (base_register_ == our_rhs->base_register_ &&
+            offset_ == our_rhs->offset_);
+  }
+  Rule* Copy() const override { return new OffsetRule(*this); }
+  // We don't actually need SetBaseRegister or SetOffset here, since they
+  // are only ever applied to CFA rules, for DW_CFA_def_cfa_offset, and it
+  // doesn't make sense to use OffsetRule for computing the CFA: it
+  // computes the address at which a register is saved, not a value.
+ private:
+  int base_register_;
+  long offset_;
+};
+
+// Rule: the value the register had in the caller is the value of
+// BASE_REGISTER plus offset. BASE_REGISTER may be
+// CallFrameInfo::Handler::kCFARegister.
+class CallFrameInfo::ValOffsetRule : public CallFrameInfo::Rule {
+ public:
+  ValOffsetRule(int base_register, long offset)
+      : base_register_(base_register), offset_(offset) {}
+  ~ValOffsetRule() {}
+  CFIRTag getTag() const override { return CFIR_VAL_OFFSET_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->ValOffsetRule(address, reg, base_register_, offset_);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_VAL_OFFSET_RULE) return false;
+    const ValOffsetRule* our_rhs = static_cast<const ValOffsetRule*>(&rhs);
+    return (base_register_ == our_rhs->base_register_ &&
+            offset_ == our_rhs->offset_);
+  }
+  Rule* Copy() const override { return new ValOffsetRule(*this); }
+  void SetBaseRegister(unsigned reg) override { base_register_ = reg; }
+  void SetOffset(long long offset) override { offset_ = offset; }
+
+ private:
+  int base_register_;
+  long offset_;
+};
+
+// Rule: the register has been saved in another register REGISTER_NUMBER_.
+class CallFrameInfo::RegisterRule : public CallFrameInfo::Rule {
+ public:
+  explicit RegisterRule(int register_number)
+      : register_number_(register_number) {}
+  ~RegisterRule() {}
+  CFIRTag getTag() const override { return CFIR_REGISTER_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->RegisterRule(address, reg, register_number_);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_REGISTER_RULE) return false;
+    const RegisterRule* our_rhs = static_cast<const RegisterRule*>(&rhs);
+    return (register_number_ == our_rhs->register_number_);
+  }
+  Rule* Copy() const override { return new RegisterRule(*this); }
+
+ private:
+  int register_number_;
+};
+
+// Rule: EXPRESSION evaluates to the address at which the register is saved.
+class CallFrameInfo::ExpressionRule : public CallFrameInfo::Rule {
+ public:
+  explicit ExpressionRule(const string& expression) : expression_(expression) {}
+  ~ExpressionRule() {}
+  CFIRTag getTag() const override { return CFIR_EXPRESSION_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->ExpressionRule(address, reg, expression_);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_EXPRESSION_RULE) return false;
+    const ExpressionRule* our_rhs = static_cast<const ExpressionRule*>(&rhs);
+    return (expression_ == our_rhs->expression_);
+  }
+  Rule* Copy() const override { return new ExpressionRule(*this); }
+
+ private:
+  string expression_;
+};
+
+// Rule: EXPRESSION evaluates to the previous value of the register.
+class CallFrameInfo::ValExpressionRule : public CallFrameInfo::Rule {
+ public:
+  explicit ValExpressionRule(const string& expression)
+      : expression_(expression) {}
+  ~ValExpressionRule() {}
+  CFIRTag getTag() const override { return CFIR_VAL_EXPRESSION_RULE; }
+  bool Handle(Handler* handler, uint64 address, int reg) const override {
+    return handler->ValExpressionRule(address, reg, expression_);
+  }
+  bool operator==(const Rule& rhs) const override {
+    if (rhs.getTag() != CFIR_VAL_EXPRESSION_RULE) return false;
+    const ValExpressionRule* our_rhs =
+        static_cast<const ValExpressionRule*>(&rhs);
+    return (expression_ == our_rhs->expression_);
+  }
+  Rule* Copy() const override { return new ValExpressionRule(*this); }
+
+ private:
+  string expression_;
+};
+
+// A map from register numbers to rules.
+class CallFrameInfo::RuleMap {
+ public:
+  RuleMap() : cfa_rule_(NULL) {}
+  RuleMap(const RuleMap& rhs) : cfa_rule_(NULL) { *this = rhs; }
+  ~RuleMap() { Clear(); }
+
+  RuleMap& operator=(const RuleMap& rhs);
+
+  // Set the rule for computing the CFA to RULE. Take ownership of RULE.
+  void SetCFARule(Rule* rule) {
+    delete cfa_rule_;
+    cfa_rule_ = rule;
+  }
+
+  // Return the current CFA rule. Unlike RegisterRule, this RuleMap retains
+  // ownership of the rule. We use this for DW_CFA_def_cfa_offset and
+  // DW_CFA_def_cfa_register, and for detecting references to the CFA before
+  // a rule for it has been established.
+  Rule* CFARule() const { return cfa_rule_; }
+
+  // Return the rule for REG, or NULL if there is none. The caller takes
+  // ownership of the result.
+  Rule* RegisterRule(int reg) const;
+
+  // Set the rule for computing REG to RULE. Take ownership of RULE.
+  void SetRegisterRule(int reg, Rule* rule);
+
+  // Make all the appropriate calls to HANDLER as if we were changing from
+  // this RuleMap to NEW_RULES at ADDRESS. We use this to implement
+  // DW_CFA_restore_state, where lots of rules can change simultaneously.
+  // Return true if all handlers returned true; otherwise, return false.
+  bool HandleTransitionTo(Handler* handler, uint64 address,
+                          const RuleMap& new_rules) const;
+
+ private:
+  // A map from register numbers to Rules.
+  typedef std::map<int, Rule*> RuleByNumber;
+
+  // Remove all register rules and clear cfa_rule_.
+  void Clear();
+
+  // The rule for computing the canonical frame address. This RuleMap owns
+  // this rule.
+  Rule* cfa_rule_;
+
+  // A map from register numbers to postfix expressions to recover
+  // their values. This RuleMap owns the Rules the map refers to.
+  RuleByNumber registers_;
+};
+
+CallFrameInfo::RuleMap& CallFrameInfo::RuleMap::operator=(const RuleMap& rhs) {
+  Clear();
+  // Since each map owns the rules it refers to, assignment must copy them.
+  if (rhs.cfa_rule_) cfa_rule_ = rhs.cfa_rule_->Copy();
+  for (RuleByNumber::const_iterator it = rhs.registers_.begin();
+       it != rhs.registers_.end(); it++)
+    registers_[it->first] = it->second->Copy();
+  return *this;
+}
+
+CallFrameInfo::Rule* CallFrameInfo::RuleMap::RegisterRule(int reg) const {
+  MOZ_ASSERT(reg != Handler::kCFARegister);
+  RuleByNumber::const_iterator it = registers_.find(reg);
+  if (it != registers_.end())
+    return it->second->Copy();
+  else
+    return NULL;
+}
+
+void CallFrameInfo::RuleMap::SetRegisterRule(int reg, Rule* rule) {
+  MOZ_ASSERT(reg != Handler::kCFARegister);
+  MOZ_ASSERT(rule);
+  Rule** slot = &registers_[reg];
+  delete *slot;
+  *slot = rule;
+}
+
+bool CallFrameInfo::RuleMap::HandleTransitionTo(
+    Handler* handler, uint64 address, const RuleMap& new_rules) const {
+  // Transition from cfa_rule_ to new_rules.cfa_rule_.
+  if (cfa_rule_ && new_rules.cfa_rule_) {
+    if (*cfa_rule_ != *new_rules.cfa_rule_ &&
+        !new_rules.cfa_rule_->Handle(handler, address, Handler::kCFARegister))
+      return false;
+  } else if (cfa_rule_) {
+    // this RuleMap has a CFA rule but new_rules doesn't.
+    // CallFrameInfo::Handler has no way to handle this --- and shouldn't;
+    // it's garbage input. The instruction interpreter should have
+    // detected this and warned, so take no action here.
+  } else if (new_rules.cfa_rule_) {
+    // This shouldn't be possible: NEW_RULES is some prior state, and
+    // there's no way to remove entries.
+    MOZ_ASSERT(0);
+  } else {
+    // Both CFA rules are empty.  No action needed.
+  }
+
+  // Traverse the two maps in order by register number, and report
+  // whatever differences we find.
+  RuleByNumber::const_iterator old_it = registers_.begin();
+  RuleByNumber::const_iterator new_it = new_rules.registers_.begin();
+  while (old_it != registers_.end() && new_it != new_rules.registers_.end()) {
+    if (old_it->first < new_it->first) {
+      // This RuleMap has an entry for old_it->first, but NEW_RULES
+      // doesn't.
+      //
+      // This isn't really the right thing to do, but since CFI generally
+      // only mentions callee-saves registers, and GCC's convention for
+      // callee-saves registers is that they are unchanged, it's a good
+      // approximation.
+      if (!handler->SameValueRule(address, old_it->first)) return false;
+      old_it++;
+    } else if (old_it->first > new_it->first) {
+      // NEW_RULES has entry for new_it->first, but this RuleMap
+      // doesn't. This shouldn't be possible: NEW_RULES is some prior
+      // state, and there's no way to remove entries.
+      MOZ_ASSERT(0);
+    } else {
+      // Both maps have an entry for this register. Report the new
+      // rule if it is different.
+      if (*old_it->second != *new_it->second &&
+          !new_it->second->Handle(handler, address, new_it->first))
+        return false;
+      new_it++;
+      old_it++;
+    }
+  }
+  // Finish off entries from this RuleMap with no counterparts in new_rules.
+  while (old_it != registers_.end()) {
+    if (!handler->SameValueRule(address, old_it->first)) return false;
+    old_it++;
+  }
+  // Since we only make transitions from a rule set to some previously
+  // saved rule set, and we can only add rules to the map, NEW_RULES
+  // must have fewer rules than *this.
+  MOZ_ASSERT(new_it == new_rules.registers_.end());
+
+  return true;
+}
+
+// Remove all register rules and clear cfa_rule_.
+void CallFrameInfo::RuleMap::Clear() {
+  delete cfa_rule_;
+  cfa_rule_ = NULL;
+  for (RuleByNumber::iterator it = registers_.begin(); it != registers_.end();
+       it++)
+    delete it->second;
+  registers_.clear();
+}
+
+// The state of the call frame information interpreter as it processes
+// instructions from a CIE and FDE.
+class CallFrameInfo::State {
+ public:
+  // Create a call frame information interpreter state with the given
+  // reporter, reader, handler, and initial call frame info address.
+  State(ByteReader* reader, Handler* handler, Reporter* reporter,
+        uint64 address)
+      : reader_(reader),
+        handler_(handler),
+        reporter_(reporter),
+        address_(address),
+        entry_(NULL),
+        cursor_(NULL),
+        saved_rules_(NULL) {}
+
+  ~State() {
+    if (saved_rules_) delete saved_rules_;
+  }
+
+  // Interpret instructions from CIE, save the resulting rule set for
+  // DW_CFA_restore instructions, and return true. On error, report
+  // the problem to reporter_ and return false.
+  bool InterpretCIE(const CIE& cie);
+
+  // Interpret instructions from FDE, and return true. On error,
+  // report the problem to reporter_ and return false.
+  bool InterpretFDE(const FDE& fde);
+
+ private:
+  // The operands of a CFI instruction, for ParseOperands.
+  struct Operands {
+    unsigned register_number;  // A register number.
+    uint64 offset;             // An offset or address.
+    long signed_offset;        // A signed offset.
+    string expression;         // A DWARF expression.
+  };
+
+  // Parse CFI instruction operands from STATE's instruction stream as
+  // described by FORMAT. On success, populate OPERANDS with the
+  // results, and return true. On failure, report the problem and
+  // return false.
+  //
+  // Each character of FORMAT should be one of the following:
+  //
+  //   'r'  unsigned LEB128 register number (OPERANDS->register_number)
+  //   'o'  unsigned LEB128 offset          (OPERANDS->offset)
+  //   's'  signed LEB128 offset            (OPERANDS->signed_offset)
+  //   'a'  machine-size address            (OPERANDS->offset)
+  //        (If the CIE has a 'z' augmentation string, 'a' uses the
+  //        encoding specified by the 'R' argument.)
+  //   '1'  a one-byte offset               (OPERANDS->offset)
+  //   '2'  a two-byte offset               (OPERANDS->offset)
+  //   '4'  a four-byte offset              (OPERANDS->offset)
+  //   '8'  an eight-byte offset            (OPERANDS->offset)
+  //   'e'  a DW_FORM_block holding a       (OPERANDS->expression)
+  //        DWARF expression
+  bool ParseOperands(const char* format, Operands* operands);
+
+  // Interpret one CFI instruction from STATE's instruction stream, update
+  // STATE, report any rule changes to handler_, and return true. On
+  // failure, report the problem and return false.
+  bool DoInstruction();
+
+  // The following Do* member functions are subroutines of DoInstruction,
+  // factoring out the actual work of operations that have several
+  // different encodings.
+
+  // Set the CFA rule to be the value of BASE_REGISTER plus OFFSET, and
+  // return true. On failure, report and return false. (Used for
+  // DW_CFA_def_cfa and DW_CFA_def_cfa_sf.)
+  bool DoDefCFA(unsigned base_register, long offset);
+
+  // Change the offset of the CFA rule to OFFSET, and return true. On
+  // failure, report and return false. (Subroutine for
+  // DW_CFA_def_cfa_offset and DW_CFA_def_cfa_offset_sf.)
+  bool DoDefCFAOffset(long offset);
+
+  // Specify that REG can be recovered using RULE, and return true. On
+  // failure, report and return false.
+  bool DoRule(unsigned reg, Rule* rule);
+
+  // Specify that REG can be found at OFFSET from the CFA, and return true.
+  // On failure, report and return false. (Subroutine for DW_CFA_offset,
+  // DW_CFA_offset_extended, and DW_CFA_offset_extended_sf.)
+  bool DoOffset(unsigned reg, long offset);
+
+  // Specify that the caller's value for REG is the CFA plus OFFSET,
+  // and return true. On failure, report and return false. (Subroutine
+  // for DW_CFA_val_offset and DW_CFA_val_offset_sf.)
+  bool DoValOffset(unsigned reg, long offset);
+
+  // Restore REG to the rule established in the CIE, and return true. On
+  // failure, report and return false. (Subroutine for DW_CFA_restore and
+  // DW_CFA_restore_extended.)
+  bool DoRestore(unsigned reg);
+
+  // Return the section offset of the instruction at cursor. For use
+  // in error messages.
+  uint64 CursorOffset() { return entry_->offset + (cursor_ - entry_->start); }
+
+  // Report that entry_ is incomplete, and return false. For brevity.
+  bool ReportIncomplete() {
+    reporter_->Incomplete(entry_->offset, entry_->kind);
+    return false;
+  }
+
+  // For reading multi-byte values with the appropriate endianness.
+  ByteReader* reader_;
+
+  // The handler to which we should report the data we find.
+  Handler* handler_;
+
+  // For reporting problems in the info we're parsing.
+  Reporter* reporter_;
+
+  // The code address to which the next instruction in the stream applies.
+  uint64 address_;
+
+  // The entry whose instructions we are currently processing. This is
+  // first a CIE, and then an FDE.
+  const Entry* entry_;
+
+  // The next instruction to process.
+  const char* cursor_;
+
+  // The current set of rules.
+  RuleMap rules_;
+
+  // The set of rules established by the CIE, used by DW_CFA_restore
+  // and DW_CFA_restore_extended. We set this after interpreting the
+  // CIE's instructions.
+  RuleMap cie_rules_;
+
+  // A stack of saved states, for DW_CFA_remember_state and
+  // DW_CFA_restore_state.
+  std::stack<RuleMap>* saved_rules_;
+};
+
+bool CallFrameInfo::State::InterpretCIE(const CIE& cie) {
+  entry_ = &cie;
+  cursor_ = entry_->instructions;
+  while (cursor_ < entry_->end)
+    if (!DoInstruction()) return false;
+  // Note the rules established by the CIE, for use by DW_CFA_restore
+  // and DW_CFA_restore_extended.
+  cie_rules_ = rules_;
+  return true;
+}
+
+bool CallFrameInfo::State::InterpretFDE(const FDE& fde) {
+  entry_ = &fde;
+  cursor_ = entry_->instructions;
+  while (cursor_ < entry_->end)
+    if (!DoInstruction()) return false;
+  return true;
+}
+
+bool CallFrameInfo::State::ParseOperands(const char* format,
+                                         Operands* operands) {
+  size_t len;
+  const char* operand;
+
+  for (operand = format; *operand; operand++) {
+    size_t bytes_left = entry_->end - cursor_;
+    switch (*operand) {
+      case 'r':
+        operands->register_number = reader_->ReadUnsignedLEB128(cursor_, &len);
+        if (len > bytes_left) return ReportIncomplete();
+        cursor_ += len;
+        break;
+
+      case 'o':
+        operands->offset = reader_->ReadUnsignedLEB128(cursor_, &len);
+        if (len > bytes_left) return ReportIncomplete();
+        cursor_ += len;
+        break;
+
+      case 's':
+        operands->signed_offset = reader_->ReadSignedLEB128(cursor_, &len);
+        if (len > bytes_left) return ReportIncomplete();
+        cursor_ += len;
+        break;
+
+      case 'a':
+        operands->offset = reader_->ReadEncodedPointer(
+            cursor_, entry_->cie->pointer_encoding, &len);
+        if (len > bytes_left) return ReportIncomplete();
+        cursor_ += len;
+        break;
+
+      case '1':
+        if (1 > bytes_left) return ReportIncomplete();
+        operands->offset = static_cast<unsigned char>(*cursor_++);
+        break;
+
+      case '2':
+        if (2 > bytes_left) return ReportIncomplete();
+        operands->offset = reader_->ReadTwoBytes(cursor_);
+        cursor_ += 2;
+        break;
+
+      case '4':
+        if (4 > bytes_left) return ReportIncomplete();
+        operands->offset = reader_->ReadFourBytes(cursor_);
+        cursor_ += 4;
+        break;
+
+      case '8':
+        if (8 > bytes_left) return ReportIncomplete();
+        operands->offset = reader_->ReadEightBytes(cursor_);
+        cursor_ += 8;
+        break;
+
+      case 'e': {
+        size_t expression_length = reader_->ReadUnsignedLEB128(cursor_, &len);
+        if (len > bytes_left || expression_length > bytes_left - len)
+          return ReportIncomplete();
+        cursor_ += len;
+        operands->expression = string(cursor_, expression_length);
+        cursor_ += expression_length;
+        break;
+      }
+
+      default:
+        MOZ_ASSERT(0);
+    }
+  }
+
+  return true;
+}
+
+bool CallFrameInfo::State::DoInstruction() {
+  CIE* cie = entry_->cie;
+  Operands ops;
+
+  // Our entry's kind should have been set by now.
+  MOZ_ASSERT(entry_->kind != kUnknown);
+
+  // We shouldn't have been invoked unless there were more
+  // instructions to parse.
+  MOZ_ASSERT(cursor_ < entry_->end);
+
+  unsigned opcode = *cursor_++;
+  if ((opcode & 0xc0) != 0) {
+    switch (opcode & 0xc0) {
+      // Advance the address.
+      case DW_CFA_advance_loc: {
+        size_t code_offset = opcode & 0x3f;
+        address_ += code_offset * cie->code_alignment_factor;
+        break;
+      }
+
+      // Find a register at an offset from the CFA.
+      case DW_CFA_offset:
+        if (!ParseOperands("o", &ops) ||
+            !DoOffset(opcode & 0x3f, ops.offset * cie->data_alignment_factor))
+          return false;
+        break;
+
+      // Restore the rule established for a register by the CIE.
+      case DW_CFA_restore:
+        if (!DoRestore(opcode & 0x3f)) return false;
+        break;
+
+      // The 'if' above should have excluded this possibility.
+      default:
+        MOZ_ASSERT(0);
+    }
+
+    // Return here, so the big switch below won't be indented.
+    return true;
+  }
+
+  switch (opcode) {
+    // Set the address.
+    case DW_CFA_set_loc:
+      if (!ParseOperands("a", &ops)) return false;
+      address_ = ops.offset;
+      break;
+
+    // Advance the address.
+    case DW_CFA_advance_loc1:
+      if (!ParseOperands("1", &ops)) return false;
+      address_ += ops.offset * cie->code_alignment_factor;
+      break;
+
+    // Advance the address.
+    case DW_CFA_advance_loc2:
+      if (!ParseOperands("2", &ops)) return false;
+      address_ += ops.offset * cie->code_alignment_factor;
+      break;
+
+    // Advance the address.
+    case DW_CFA_advance_loc4:
+      if (!ParseOperands("4", &ops)) return false;
+      address_ += ops.offset * cie->code_alignment_factor;
+      break;
+
+    // Advance the address.
+    case DW_CFA_MIPS_advance_loc8:
+      if (!ParseOperands("8", &ops)) return false;
+      address_ += ops.offset * cie->code_alignment_factor;
+      break;
+
+    // Compute the CFA by adding an offset to a register.
+    case DW_CFA_def_cfa:
+      if (!ParseOperands("ro", &ops) ||
+          !DoDefCFA(ops.register_number, ops.offset))
+        return false;
+      break;
+
+    // Compute the CFA by adding an offset to a register.
+    case DW_CFA_def_cfa_sf:
+      if (!ParseOperands("rs", &ops) ||
+          !DoDefCFA(ops.register_number,
+                    ops.signed_offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // Change the base register used to compute the CFA.
+    case DW_CFA_def_cfa_register: {
+      Rule* cfa_rule = rules_.CFARule();
+      if (!cfa_rule) {
+        reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
+        return false;
+      }
+      if (!ParseOperands("r", &ops)) return false;
+      cfa_rule->SetBaseRegister(ops.register_number);
+      if (!cfa_rule->Handle(handler_, address_, Handler::kCFARegister))
+        return false;
+      break;
+    }
+
+    // Change the offset used to compute the CFA.
+    case DW_CFA_def_cfa_offset:
+      if (!ParseOperands("o", &ops) || !DoDefCFAOffset(ops.offset))
+        return false;
+      break;
+
+    // Change the offset used to compute the CFA.
+    case DW_CFA_def_cfa_offset_sf:
+      if (!ParseOperands("s", &ops) ||
+          !DoDefCFAOffset(ops.signed_offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // Specify an expression whose value is the CFA.
+    case DW_CFA_def_cfa_expression: {
+      if (!ParseOperands("e", &ops)) return false;
+      Rule* rule = new ValExpressionRule(ops.expression);
+      rules_.SetCFARule(rule);
+      if (!rule->Handle(handler_, address_, Handler::kCFARegister))
+        return false;
+      break;
+    }
+
+    // The register's value cannot be recovered.
+    case DW_CFA_undefined: {
+      if (!ParseOperands("r", &ops) ||
+          !DoRule(ops.register_number, new UndefinedRule()))
+        return false;
+      break;
+    }
+
+    // The register's value is unchanged from its value in the caller.
+    case DW_CFA_same_value: {
+      if (!ParseOperands("r", &ops) ||
+          !DoRule(ops.register_number, new SameValueRule()))
+        return false;
+      break;
+    }
+
+    // Find a register at an offset from the CFA.
+    case DW_CFA_offset_extended:
+      if (!ParseOperands("ro", &ops) ||
+          !DoOffset(ops.register_number,
+                    ops.offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // The register is saved at an offset from the CFA.
+    case DW_CFA_offset_extended_sf:
+      if (!ParseOperands("rs", &ops) ||
+          !DoOffset(ops.register_number,
+                    ops.signed_offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // The register is saved at an offset from the CFA.
+    case DW_CFA_GNU_negative_offset_extended:
+      if (!ParseOperands("ro", &ops) ||
+          !DoOffset(ops.register_number,
+                    -ops.offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // The register's value is the sum of the CFA plus an offset.
+    case DW_CFA_val_offset:
+      if (!ParseOperands("ro", &ops) ||
+          !DoValOffset(ops.register_number,
+                       ops.offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // The register's value is the sum of the CFA plus an offset.
+    case DW_CFA_val_offset_sf:
+      if (!ParseOperands("rs", &ops) ||
+          !DoValOffset(ops.register_number,
+                       ops.signed_offset * cie->data_alignment_factor))
+        return false;
+      break;
+
+    // The register has been saved in another register.
+    case DW_CFA_register: {
+      if (!ParseOperands("ro", &ops) ||
+          !DoRule(ops.register_number, new RegisterRule(ops.offset)))
+        return false;
+      break;
+    }
+
+    // An expression yields the address at which the register is saved.
+    case DW_CFA_expression: {
+      if (!ParseOperands("re", &ops) ||
+          !DoRule(ops.register_number, new ExpressionRule(ops.expression)))
+        return false;
+      break;
+    }
+
+    // An expression yields the caller's value for the register.
+    case DW_CFA_val_expression: {
+      if (!ParseOperands("re", &ops) ||
+          !DoRule(ops.register_number, new ValExpressionRule(ops.expression)))
+        return false;
+      break;
+    }
+
+    // Restore the rule established for a register by the CIE.
+    case DW_CFA_restore_extended:
+      if (!ParseOperands("r", &ops) || !DoRestore(ops.register_number))
+        return false;
+      break;
+
+    // Save the current set of rules on a stack.
+    case DW_CFA_remember_state:
+      if (!saved_rules_) {
+        saved_rules_ = new std::stack<RuleMap>();
+      }
+      saved_rules_->push(rules_);
+      break;
+
+    // Pop the current set of rules off the stack.
+    case DW_CFA_restore_state: {
+      if (!saved_rules_ || saved_rules_->empty()) {
+        reporter_->EmptyStateStack(entry_->offset, entry_->kind,
+                                   CursorOffset());
+        return false;
+      }
+      const RuleMap& new_rules = saved_rules_->top();
+      if (rules_.CFARule() && !new_rules.CFARule()) {
+        reporter_->ClearingCFARule(entry_->offset, entry_->kind,
+                                   CursorOffset());
+        return false;
+      }
+      rules_.HandleTransitionTo(handler_, address_, new_rules);
+      rules_ = new_rules;
+      saved_rules_->pop();
+      break;
+    }
+
+    // No operation.  (Padding instruction.)
+    case DW_CFA_nop:
+      break;
+
+    // A SPARC register window save: Registers 8 through 15 (%o0-%o7)
+    // are saved in registers 24 through 31 (%i0-%i7), and registers
+    // 16 through 31 (%l0-%l7 and %i0-%i7) are saved at CFA offsets
+    // (0-15 * the register size). The register numbers must be
+    // hard-coded. A GNU extension, and not a pretty one.
+    case DW_CFA_GNU_window_save: {
+      // Save %o0-%o7 in %i0-%i7.
+      for (int i = 8; i < 16; i++)
+        if (!DoRule(i, new RegisterRule(i + 16))) return false;
+      // Save %l0-%l7 and %i0-%i7 at the CFA.
+      for (int i = 16; i < 32; i++)
+        // Assume that the byte reader's address size is the same as
+        // the architecture's register size. !@#%*^ hilarious.
+        if (!DoRule(i, new OffsetRule(Handler::kCFARegister,
+                                      (i - 16) * reader_->AddressSize())))
+          return false;
+      break;
+    }
+
+    // I'm not sure what this is. GDB doesn't use it for unwinding.
+    case DW_CFA_GNU_args_size:
+      if (!ParseOperands("o", &ops)) return false;
+      break;
+
+    // An opcode we don't recognize.
+    default: {
+      reporter_->BadInstruction(entry_->offset, entry_->kind, CursorOffset());
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool CallFrameInfo::State::DoDefCFA(unsigned base_register, long offset) {
+  Rule* rule = new ValOffsetRule(base_register, offset);
+  rules_.SetCFARule(rule);
+  return rule->Handle(handler_, address_, Handler::kCFARegister);
+}
+
+bool CallFrameInfo::State::DoDefCFAOffset(long offset) {
+  Rule* cfa_rule = rules_.CFARule();
+  if (!cfa_rule) {
+    reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
+    return false;
+  }
+  cfa_rule->SetOffset(offset);
+  return cfa_rule->Handle(handler_, address_, Handler::kCFARegister);
+}
+
+bool CallFrameInfo::State::DoRule(unsigned reg, Rule* rule) {
+  rules_.SetRegisterRule(reg, rule);
+  return rule->Handle(handler_, address_, reg);
+}
+
+bool CallFrameInfo::State::DoOffset(unsigned reg, long offset) {
+  if (!rules_.CFARule()) {
+    reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
+    return false;
+  }
+  return DoRule(reg, new OffsetRule(Handler::kCFARegister, offset));
+}
+
+bool CallFrameInfo::State::DoValOffset(unsigned reg, long offset) {
+  if (!rules_.CFARule()) {
+    reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
+    return false;
+  }
+  return DoRule(reg, new ValOffsetRule(Handler::kCFARegister, offset));
+}
+
+bool CallFrameInfo::State::DoRestore(unsigned reg) {
+  // DW_CFA_restore and DW_CFA_restore_extended don't make sense in a CIE.
+  if (entry_->kind == kCIE) {
+    reporter_->RestoreInCIE(entry_->offset, CursorOffset());
+    return false;
+  }
+  Rule* rule = cie_rules_.RegisterRule(reg);
+  if (!rule) {
+    // This isn't really the right thing to do, but since CFI generally
+    // only mentions callee-saves registers, and GCC's convention for
+    // callee-saves registers is that they are unchanged, it's a good
+    // approximation.
+    rule = new SameValueRule();
+  }
+  return DoRule(reg, rule);
+}
+
+bool CallFrameInfo::ReadEntryPrologue(const char* cursor, Entry* entry) {
+  const char* buffer_end = buffer_ + buffer_length_;
+
+  // Initialize enough of ENTRY for use in error reporting.
+  entry->offset = cursor - buffer_;
+  entry->start = cursor;
+  entry->kind = kUnknown;
+  entry->end = NULL;
+
+  // Read the initial length. This sets reader_'s offset size.
+  size_t length_size;
+  uint64 length = reader_->ReadInitialLength(cursor, &length_size);
+  if (length_size > size_t(buffer_end - cursor)) return ReportIncomplete(entry);
+  cursor += length_size;
+
+  // In a .eh_frame section, a length of zero marks the end of the series
+  // of entries.
+  if (length == 0 && eh_frame_) {
+    entry->kind = kTerminator;
+    entry->end = cursor;
+    return true;
+  }
+
+  // Validate the length.
+  if (length > size_t(buffer_end - cursor)) return ReportIncomplete(entry);
+
+  // The length is the number of bytes after the initial length field;
+  // we have that position handy at this point, so compute the end
+  // now. (If we're parsing 64-bit-offset DWARF on a 32-bit machine,
+  // and the length didn't fit in a size_t, we would have rejected it
+  // above.)
+  entry->end = cursor + length;
+
+  // Parse the next field: either the offset of a CIE or a CIE id.
+  size_t offset_size = reader_->OffsetSize();
+  if (offset_size > size_t(entry->end - cursor)) return ReportIncomplete(entry);
+  entry->id = reader_->ReadOffset(cursor);
+
+  // Don't advance cursor past id field yet; in .eh_frame data we need
+  // the id's position to compute the section offset of an FDE's CIE.
+
+  // Now we can decide what kind of entry this is.
+  if (eh_frame_) {
+    // In .eh_frame data, an ID of zero marks the entry as a CIE, and
+    // anything else is an offset from the id field of the FDE to the start
+    // of the CIE.
+    if (entry->id == 0) {
+      entry->kind = kCIE;
+    } else {
+      entry->kind = kFDE;
+      // Turn the offset from the id into an offset from the buffer's start.
+      entry->id = (cursor - buffer_) - entry->id;
+    }
+  } else {
+    // In DWARF CFI data, an ID of ~0 (of the appropriate width, given the
+    // offset size for the entry) marks the entry as a CIE, and anything
+    // else is the offset of the CIE from the beginning of the section.
+    if (offset_size == 4)
+      entry->kind = (entry->id == 0xffffffff) ? kCIE : kFDE;
+    else {
+      MOZ_ASSERT(offset_size == 8);
+      entry->kind = (entry->id == 0xffffffffffffffffULL) ? kCIE : kFDE;
+    }
+  }
+
+  // Now advance cursor past the id.
+  cursor += offset_size;
+
+  // The fields specific to this kind of entry start here.
+  entry->fields = cursor;
+
+  entry->cie = NULL;
+
+  return true;
+}
+
+bool CallFrameInfo::ReadCIEFields(CIE* cie) {
+  const char* cursor = cie->fields;
+  size_t len;
+
+  MOZ_ASSERT(cie->kind == kCIE);
+
+  // Prepare for early exit.
+  cie->version = 0;
+  cie->augmentation.clear();
+  cie->code_alignment_factor = 0;
+  cie->data_alignment_factor = 0;
+  cie->return_address_register = 0;
+  cie->has_z_augmentation = false;
+  cie->pointer_encoding = DW_EH_PE_absptr;
+  cie->instructions = 0;
+
+  // Parse the version number.
+  if (cie->end - cursor < 1) return ReportIncomplete(cie);
+  cie->version = reader_->ReadOneByte(cursor);
+  cursor++;
+
+  // If we don't recognize the version, we can't parse any more fields of the
+  // CIE. For DWARF CFI, we handle versions 1 through 4 (there was never a
+  // version 2 of CFI data). For .eh_frame, we handle versions 1 and 4 as well;
+  // the difference between those versions seems to be the same as for
+  // .debug_frame.
+  if (cie->version < 1 || cie->version > 4) {
+    reporter_->UnrecognizedVersion(cie->offset, cie->version);
+    return false;
+  }
+
+  const char* augmentation_start = cursor;
+  const void* augmentation_end =
+      memchr(augmentation_start, '\0', cie->end - augmentation_start);
+  if (!augmentation_end) return ReportIncomplete(cie);
+  cursor = static_cast<const char*>(augmentation_end);
+  cie->augmentation = string(augmentation_start, cursor - augmentation_start);
+  // Skip the terminating '\0'.
+  cursor++;
+
+  // Is this CFI augmented?
+  if (!cie->augmentation.empty()) {
+    // Is it an augmentation we recognize?
+    if (cie->augmentation[0] == DW_Z_augmentation_start) {
+      // Linux C++ ABI 'z' augmentation, used for exception handling data.
+      cie->has_z_augmentation = true;
+    } else {
+      // Not an augmentation we recognize. Augmentations can have arbitrary
+      // effects on the form of rest of the content, so we have to give up.
+      reporter_->UnrecognizedAugmentation(cie->offset, cie->augmentation);
+      return false;
+    }
+  }
+
+  if (cie->version >= 4) {
+    // Check that the address_size and segment_size fields are plausible.
+    if (cie->end - cursor < 2) {
+      return ReportIncomplete(cie);
+    }
+    uint8_t address_size = reader_->ReadOneByte(cursor);
+    cursor++;
+    if (address_size != sizeof(void*)) {
+      // This is not per-se invalid CFI.  But we can reasonably expect to
+      // be running on a target of the same word size as the CFI is for,
+      // so we reject this case.
+      reporter_->InvalidDwarf4Artefact(cie->offset, "Invalid address_size");
+      return false;
+    }
+    uint8_t segment_size = reader_->ReadOneByte(cursor);
+    cursor++;
+    if (segment_size != 0) {
+      // This is also not per-se invalid CFI, but we don't currently handle
+      // the case of non-zero |segment_size|.
+      reporter_->InvalidDwarf4Artefact(cie->offset, "Invalid segment_size");
+      return false;
+    }
+    // We only continue parsing if |segment_size| is zero.  If this routine
+    // is ever changed to allow non-zero |segment_size|, then
+    // ReadFDEFields() below will have to be changed to match, per comments
+    // there.
+  }
+
+  // Parse the code alignment factor.
+  cie->code_alignment_factor = reader_->ReadUnsignedLEB128(cursor, &len);
+  if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
+  cursor += len;
+
+  // Parse the data alignment factor.
+  cie->data_alignment_factor = reader_->ReadSignedLEB128(cursor, &len);
+  if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
+  cursor += len;
+
+  // Parse the return address register. This is a ubyte in version 1, and
+  // a ULEB128 in version 3.
+  if (cie->version == 1) {
+    if (cursor >= cie->end) return ReportIncomplete(cie);
+    cie->return_address_register = uint8(*cursor++);
+  } else {
+    cie->return_address_register = reader_->ReadUnsignedLEB128(cursor, &len);
+    if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
+    cursor += len;
+  }
+
+  // If we have a 'z' augmentation string, find the augmentation data and
+  // use the augmentation string to parse it.
+  if (cie->has_z_augmentation) {
+    uint64_t data_size = reader_->ReadUnsignedLEB128(cursor, &len);
+    if (size_t(cie->end - cursor) < len + data_size)
+      return ReportIncomplete(cie);
+    cursor += len;
+    const char* data = cursor;
+    cursor += data_size;
+    const char* data_end = cursor;
+
+    cie->has_z_lsda = false;
+    cie->has_z_personality = false;
+    cie->has_z_signal_frame = false;
+
+    // Walk the augmentation string, and extract values from the
+    // augmentation data as the string directs.
+    for (size_t i = 1; i < cie->augmentation.size(); i++) {
+      switch (cie->augmentation[i]) {
+        case DW_Z_has_LSDA:
+          // The CIE's augmentation data holds the language-specific data
+          // area pointer's encoding, and the FDE's augmentation data holds
+          // the pointer itself.
+          cie->has_z_lsda = true;
+          // Fetch the LSDA encoding from the augmentation data.
+          if (data >= data_end) return ReportIncomplete(cie);
+          cie->lsda_encoding = DwarfPointerEncoding(*data++);
+          if (!reader_->ValidEncoding(cie->lsda_encoding)) {
+            reporter_->InvalidPointerEncoding(cie->offset, cie->lsda_encoding);
+            return false;
+          }
+          // Don't check if the encoding is usable here --- we haven't
+          // read the FDE's fields yet, so we're not prepared for
+          // DW_EH_PE_funcrel, although that's a fine encoding for the
+          // LSDA to use, since it appears in the FDE.
+          break;
+
+        case DW_Z_has_personality_routine:
+          // The CIE's augmentation data holds the personality routine
+          // pointer's encoding, followed by the pointer itself.
+          cie->has_z_personality = true;
+          // Fetch the personality routine pointer's encoding from the
+          // augmentation data.
+          if (data >= data_end) return ReportIncomplete(cie);
+          cie->personality_encoding = DwarfPointerEncoding(*data++);
+          if (!reader_->ValidEncoding(cie->personality_encoding)) {
+            reporter_->InvalidPointerEncoding(cie->offset,
+                                              cie->personality_encoding);
+            return false;
+          }
+          if (!reader_->UsableEncoding(cie->personality_encoding)) {
+            reporter_->UnusablePointerEncoding(cie->offset,
+                                               cie->personality_encoding);
+            return false;
+          }
+          // Fetch the personality routine's pointer itself from the data.
+          cie->personality_address = reader_->ReadEncodedPointer(
+              data, cie->personality_encoding, &len);
+          if (len > size_t(data_end - data)) return ReportIncomplete(cie);
+          data += len;
+          break;
+
+        case DW_Z_has_FDE_address_encoding:
+          // The CIE's augmentation data holds the pointer encoding to use
+          // for addresses in the FDE.
+          if (data >= data_end) return ReportIncomplete(cie);
+          cie->pointer_encoding = DwarfPointerEncoding(*data++);
+          if (!reader_->ValidEncoding(cie->pointer_encoding)) {
+            reporter_->InvalidPointerEncoding(cie->offset,
+                                              cie->pointer_encoding);
+            return false;
+          }
+          if (!reader_->UsableEncoding(cie->pointer_encoding)) {
+            reporter_->UnusablePointerEncoding(cie->offset,
+                                               cie->pointer_encoding);
+            return false;
+          }
+          break;
+
+        case DW_Z_is_signal_trampoline:
+          // Frames using this CIE are signal delivery frames.
+          cie->has_z_signal_frame = true;
+          break;
+
+        default:
+          // An augmentation we don't recognize.
+          reporter_->UnrecognizedAugmentation(cie->offset, cie->augmentation);
+          return false;
+      }
+    }
+  }
+
+  // The CIE's instructions start here.
+  cie->instructions = cursor;
+
+  return true;
+}
+
+bool CallFrameInfo::ReadFDEFields(FDE* fde) {
+  const char* cursor = fde->fields;
+  size_t size;
+
+  // At this point, for Dwarf 4 and above, we are assuming that the
+  // associated CIE has its |segment_size| field equal to zero.  This is
+  // checked for in ReadCIEFields() above.  If ReadCIEFields() is ever
+  // changed to allow non-zero |segment_size| CIEs then we will have to read
+  // the segment_selector value at this point.
+
+  fde->address =
+      reader_->ReadEncodedPointer(cursor, fde->cie->pointer_encoding, &size);
+  if (size > size_t(fde->end - cursor)) return ReportIncomplete(fde);
+  cursor += size;
+  reader_->SetFunctionBase(fde->address);
+
+  // For the length, we strip off the upper nybble of the encoding used for
+  // the starting address.
+  DwarfPointerEncoding length_encoding =
+      DwarfPointerEncoding(fde->cie->pointer_encoding & 0x0f);
+  fde->size = reader_->ReadEncodedPointer(cursor, length_encoding, &size);
+  if (size > size_t(fde->end - cursor)) return ReportIncomplete(fde);
+  cursor += size;
+
+  // If the CIE has a 'z' augmentation string, then augmentation data
+  // appears here.
+  if (fde->cie->has_z_augmentation) {
+    uint64_t data_size = reader_->ReadUnsignedLEB128(cursor, &size);
+    if (size_t(fde->end - cursor) < size + data_size)
+      return ReportIncomplete(fde);
+    cursor += size;
+
+    // In the abstract, we should walk the augmentation string, and extract
+    // items from the FDE's augmentation data as we encounter augmentation
+    // string characters that specify their presence: the ordering of items
+    // in the augmentation string determines the arrangement of values in
+    // the augmentation data.
+    //
+    // In practice, there's only ever one value in FDE augmentation data
+    // that we support --- the LSDA pointer --- and we have to bail if we
+    // see any unrecognized augmentation string characters. So if there is
+    // anything here at all, we know what it is, and where it starts.
+    if (fde->cie->has_z_lsda) {
+      // Check whether the LSDA's pointer encoding is usable now: only once
+      // we've parsed the FDE's starting address do we call reader_->
+      // SetFunctionBase, so that the DW_EH_PE_funcrel encoding becomes
+      // usable.
+      if (!reader_->UsableEncoding(fde->cie->lsda_encoding)) {
+        reporter_->UnusablePointerEncoding(fde->cie->offset,
+                                           fde->cie->lsda_encoding);
+        return false;
+      }
+
+      fde->lsda_address =
+          reader_->ReadEncodedPointer(cursor, fde->cie->lsda_encoding, &size);
+      if (size > data_size) return ReportIncomplete(fde);
+      // Ideally, we would also complain here if there were unconsumed
+      // augmentation data.
+    }
+
+    cursor += data_size;
+  }
+
+  // The FDE's instructions start after those.
+  fde->instructions = cursor;
+
+  return true;
+}
+
+bool CallFrameInfo::Start() {
+  const char* buffer_end = buffer_ + buffer_length_;
+  const char* cursor;
+  bool all_ok = true;
+  const char* entry_end;
+  bool ok;
+
+  // Traverse all the entries in buffer_, skipping CIEs and offering
+  // FDEs to the handler.
+  for (cursor = buffer_; cursor < buffer_end;
+       cursor = entry_end, all_ok = all_ok && ok) {
+    FDE fde;
+
+    // Make it easy to skip this entry with 'continue': assume that
+    // things are not okay until we've checked all the data, and
+    // prepare the address of the next entry.
+    ok = false;
+
+    // Read the entry's prologue.
+    if (!ReadEntryPrologue(cursor, &fde)) {
+      if (!fde.end) {
+        // If we couldn't even figure out this entry's extent, then we
+        // must stop processing entries altogether.
+        all_ok = false;
+        break;
+      }
+      entry_end = fde.end;
+      continue;
+    }
+
+    // The next iteration picks up after this entry.
+    entry_end = fde.end;
+
+    // Did we see an .eh_frame terminating mark?
+    if (fde.kind == kTerminator) {
+      // If there appears to be more data left in the section after the
+      // terminating mark, warn the user. But this is just a warning;
+      // we leave all_ok true.
+      if (fde.end < buffer_end) reporter_->EarlyEHTerminator(fde.offset);
+      break;
+    }
+
+    // In this loop, we skip CIEs. We only parse them fully when we
+    // parse an FDE that refers to them. This limits our memory
+    // consumption (beyond the buffer itself) to that needed to
+    // process the largest single entry.
+    if (fde.kind != kFDE) {
+      ok = true;
+      continue;
+    }
+
+    // Validate the CIE pointer.
+    if (fde.id > buffer_length_) {
+      reporter_->CIEPointerOutOfRange(fde.offset, fde.id);
+      continue;
+    }
+
+    CIE cie;
+
+    // Parse this FDE's CIE header.
+    if (!ReadEntryPrologue(buffer_ + fde.id, &cie)) continue;
+    // This had better be an actual CIE.
+    if (cie.kind != kCIE) {
+      reporter_->BadCIEId(fde.offset, fde.id);
+      continue;
+    }
+    if (!ReadCIEFields(&cie)) continue;
+
+    // We now have the values that govern both the CIE and the FDE.
+    cie.cie = &cie;
+    fde.cie = &cie;
+
+    // Parse the FDE's header.
+    if (!ReadFDEFields(&fde)) continue;
+
+    // Call Entry to ask the consumer if they're interested.
+    if (!handler_->Entry(fde.offset, fde.address, fde.size, cie.version,
+                         cie.augmentation, cie.return_address_register)) {
+      // The handler isn't interested in this entry. That's not an error.
+      ok = true;
+      continue;
+    }
+
+    if (cie.has_z_augmentation) {
+      // Report the personality routine address, if we have one.
+      if (cie.has_z_personality) {
+        if (!handler_->PersonalityRoutine(
+                cie.personality_address,
+                IsIndirectEncoding(cie.personality_encoding)))
+          continue;
+      }
+
+      // Report the language-specific data area address, if we have one.
+      if (cie.has_z_lsda) {
+        if (!handler_->LanguageSpecificDataArea(
+                fde.lsda_address, IsIndirectEncoding(cie.lsda_encoding)))
+          continue;
+      }
+
+      // If this is a signal-handling frame, report that.
+      if (cie.has_z_signal_frame) {
+        if (!handler_->SignalHandler()) continue;
+      }
+    }
+
+    // Interpret the CIE's instructions, and then the FDE's instructions.
+    State state(reader_, handler_, reporter_, fde.address);
+    ok = state.InterpretCIE(cie) && state.InterpretFDE(fde);
+
+    // Tell the ByteReader that the function start address from the
+    // FDE header is no longer valid.
+    reader_->ClearFunctionBase();
+
+    // Report the end of the entry.
+    handler_->End();
+  }
+
+  return all_ok;
+}
+
+const char* CallFrameInfo::KindName(EntryKind kind) {
+  if (kind == CallFrameInfo::kUnknown)
+    return "entry";
+  else if (kind == CallFrameInfo::kCIE)
+    return "common information entry";
+  else if (kind == CallFrameInfo::kFDE)
+    return "frame description entry";
+  else {
+    MOZ_ASSERT(kind == CallFrameInfo::kTerminator);
+    return ".eh_frame sequence terminator";
+  }
+}
+
+bool CallFrameInfo::ReportIncomplete(Entry* entry) {
+  reporter_->Incomplete(entry->offset, entry->kind);
+  return false;
+}
+
+void CallFrameInfo::Reporter::Incomplete(uint64 offset,
+                                         CallFrameInfo::EntryKind kind) {
+  char buf[300];
+  SprintfLiteral(buf, "%s: CFI %s at offset 0x%llx in '%s': entry ends early\n",
+                 filename_.c_str(), CallFrameInfo::KindName(kind), offset,
+                 section_.c_str());
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::EarlyEHTerminator(uint64 offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI at offset 0x%llx in '%s': saw end-of-data marker"
+                 " before end of section contents\n",
+                 filename_.c_str(), offset, section_.c_str());
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::CIEPointerOutOfRange(uint64 offset,
+                                                   uint64 cie_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI frame description entry at offset 0x%llx in '%s':"
+                 " CIE pointer is out of range: 0x%llx\n",
+                 filename_.c_str(), offset, section_.c_str(), cie_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::BadCIEId(uint64 offset, uint64 cie_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI frame description entry at offset 0x%llx in '%s':"
+                 " CIE pointer does not point to a CIE: 0x%llx\n",
+                 filename_.c_str(), offset, section_.c_str(), cie_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::UnrecognizedVersion(uint64 offset, int version) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI frame description entry at offset 0x%llx in '%s':"
+                 " CIE specifies unrecognized version: %d\n",
+                 filename_.c_str(), offset, section_.c_str(), version);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::UnrecognizedAugmentation(uint64 offset,
+                                                       const string& aug) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI frame description entry at offset 0x%llx in '%s':"
+                 " CIE specifies unrecognized augmentation: '%s'\n",
+                 filename_.c_str(), offset, section_.c_str(), aug.c_str());
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::InvalidDwarf4Artefact(uint64 offset,
+                                                    const char* what) {
+  char* what_safe = strndup(what, 100);
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI frame description entry at offset 0x%llx in '%s':"
+                 " CIE specifies invalid Dwarf4 artefact: %s\n",
+                 filename_.c_str(), offset, section_.c_str(), what_safe);
+  log_(buf);
+  free(what_safe);
+}
+
+void CallFrameInfo::Reporter::InvalidPointerEncoding(uint64 offset,
+                                                     uint8 encoding) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI common information entry at offset 0x%llx in '%s':"
+                 " 'z' augmentation specifies invalid pointer encoding: "
+                 "0x%02x\n",
+                 filename_.c_str(), offset, section_.c_str(), encoding);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::UnusablePointerEncoding(uint64 offset,
+                                                      uint8 encoding) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI common information entry at offset 0x%llx in '%s':"
+                 " 'z' augmentation specifies a pointer encoding for which"
+                 " we have no base address: 0x%02x\n",
+                 filename_.c_str(), offset, section_.c_str(), encoding);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::RestoreInCIE(uint64 offset, uint64 insn_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI common information entry at offset 0x%llx in '%s':"
+                 " the DW_CFA_restore instruction at offset 0x%llx"
+                 " cannot be used in a common information entry\n",
+                 filename_.c_str(), offset, section_.c_str(), insn_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::BadInstruction(uint64 offset,
+                                             CallFrameInfo::EntryKind kind,
+                                             uint64 insn_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI %s at offset 0x%llx in section '%s':"
+                 " the instruction at offset 0x%llx is unrecognized\n",
+                 filename_.c_str(), CallFrameInfo::KindName(kind), offset,
+                 section_.c_str(), insn_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::NoCFARule(uint64 offset,
+                                        CallFrameInfo::EntryKind kind,
+                                        uint64 insn_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI %s at offset 0x%llx in section '%s':"
+                 " the instruction at offset 0x%llx assumes that a CFA rule "
+                 "has been set, but none has been set\n",
+                 filename_.c_str(), CallFrameInfo::KindName(kind), offset,
+                 section_.c_str(), insn_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::EmptyStateStack(uint64 offset,
+                                              CallFrameInfo::EntryKind kind,
+                                              uint64 insn_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI %s at offset 0x%llx in section '%s':"
+                 " the DW_CFA_restore_state instruction at offset 0x%llx"
+                 " should pop a saved state from the stack, but the stack "
+                 "is empty\n",
+                 filename_.c_str(), CallFrameInfo::KindName(kind), offset,
+                 section_.c_str(), insn_offset);
+  log_(buf);
+}
+
+void CallFrameInfo::Reporter::ClearingCFARule(uint64 offset,
+                                              CallFrameInfo::EntryKind kind,
+                                              uint64 insn_offset) {
+  char buf[300];
+  SprintfLiteral(buf,
+                 "%s: CFI %s at offset 0x%llx in section '%s':"
+                 " the DW_CFA_restore_state instruction at offset 0x%llx"
+                 " would clear the CFA rule in effect\n",
+                 filename_.c_str(), CallFrameInfo::KindName(kind), offset,
+                 section_.c_str(), insn_offset);
+  log_(buf);
+}
+
+unsigned int DwarfCFIToModule::RegisterNames::I386() {
+  /*
+   8 "$eax", "$ecx", "$edx", "$ebx", "$esp", "$ebp", "$esi", "$edi",
+   3 "$eip", "$eflags", "$unused1",
+   8 "$st0", "$st1", "$st2", "$st3", "$st4", "$st5", "$st6", "$st7",
+   2 "$unused2", "$unused3",
+   8 "$xmm0", "$xmm1", "$xmm2", "$xmm3", "$xmm4", "$xmm5", "$xmm6", "$xmm7",
+   8 "$mm0", "$mm1", "$mm2", "$mm3", "$mm4", "$mm5", "$mm6", "$mm7",
+   3 "$fcw", "$fsw", "$mxcsr",
+   8 "$es", "$cs", "$ss", "$ds", "$fs", "$gs", "$unused4", "$unused5",
+   2 "$tr", "$ldtr"
+  */
+  return 8 + 3 + 8 + 2 + 8 + 8 + 3 + 8 + 2;
+}
+
+unsigned int DwarfCFIToModule::RegisterNames::X86_64() {
+  /*
+   8 "$rax", "$rdx", "$rcx", "$rbx", "$rsi", "$rdi", "$rbp", "$rsp",
+   8 "$r8",  "$r9",  "$r10", "$r11", "$r12", "$r13", "$r14", "$r15",
+   1 "$rip",
+   8 "$xmm0","$xmm1","$xmm2", "$xmm3", "$xmm4", "$xmm5", "$xmm6", "$xmm7",
+   8 "$xmm8","$xmm9","$xmm10","$xmm11","$xmm12","$xmm13","$xmm14","$xmm15",
+   8 "$st0", "$st1", "$st2", "$st3", "$st4", "$st5", "$st6", "$st7",
+   8 "$mm0", "$mm1", "$mm2", "$mm3", "$mm4", "$mm5", "$mm6", "$mm7",
+   1 "$rflags",
+   8 "$es", "$cs", "$ss", "$ds", "$fs", "$gs", "$unused1", "$unused2",
+   4 "$fs.base", "$gs.base", "$unused3", "$unused4",
+   2 "$tr", "$ldtr",
+   3 "$mxcsr", "$fcw", "$fsw"
+  */
+  return 8 + 8 + 1 + 8 + 8 + 8 + 8 + 1 + 8 + 4 + 2 + 3;
+}
+
+// Per ARM IHI 0040A, section 3.1
+unsigned int DwarfCFIToModule::RegisterNames::ARM() {
+  /*
+   8 "r0",  "r1",  "r2",  "r3",  "r4",  "r5",  "r6",  "r7",
+   8 "r8",  "r9",  "r10", "r11", "r12", "sp",  "lr",  "pc",
+   8 "f0",  "f1",  "f2",  "f3",  "f4",  "f5",  "f6",  "f7",
+   8 "fps", "cpsr", "",   "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "s0",  "s1",  "s2",  "s3",  "s4",  "s5",  "s6",  "s7",
+   8 "s8",  "s9",  "s10", "s11", "s12", "s13", "s14", "s15",
+   8 "s16", "s17", "s18", "s19", "s20", "s21", "s22", "s23",
+   8 "s24", "s25", "s26", "s27", "s28", "s29", "s30", "s31",
+   8 "f0",  "f1",  "f2",  "f3",  "f4",  "f5",  "f6",  "f7"
+  */
+  return 13 * 8;
+}
+
+// Per ARM IHI 0057A, section 3.1
+unsigned int DwarfCFIToModule::RegisterNames::ARM64() {
+  /*
+   8 "x0",  "x1",  "x2",  "x3",  "x4",  "x5",  "x6",  "x7",
+   8 "x8",  "x9",  "x10", "x11", "x12", "x13", "x14", "x15",
+   8 "x16"  "x17", "x18", "x19", "x20", "x21", "x22", "x23",
+   8 "x24", "x25", "x26", "x27", "x28", "x29",  "x30","sp",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "",    "",    "",    "",    "",    "",    "",    "",
+   8 "v0",  "v1",  "v2",  "v3",  "v4",  "v5",  "v6",  "v7",
+   8 "v8",  "v9",  "v10", "v11", "v12", "v13", "v14", "v15",
+   8 "v16", "v17", "v18", "v19", "v20", "v21", "v22,  "v23",
+   8 "v24", "x25", "x26,  "x27", "v28", "v29", "v30", "v31",
+  */
+  return 12 * 8;
+}
+
+unsigned int DwarfCFIToModule::RegisterNames::MIPS() {
+  /*
+   8 "$zero", "$at",  "$v0",  "$v1",  "$a0",   "$a1",  "$a2",  "$a3",
+   8 "$t0",   "$t1",  "$t2",  "$t3",  "$t4",   "$t5",  "$t6",  "$t7",
+   8 "$s0",   "$s1",  "$s2",  "$s3",  "$s4",   "$s5",  "$s6",  "$s7",
+   8 "$t8",   "$t9",  "$k0",  "$k1",  "$gp",   "$sp",  "$fp",  "$ra",
+   9 "$lo",   "$hi",  "$pc",  "$f0",  "$f1",   "$f2",  "$f3",  "$f4",  "$f5",
+   8 "$f6",   "$f7",  "$f8",  "$f9",  "$f10",  "$f11", "$f12", "$f13",
+   7 "$f14",  "$f15", "$f16", "$f17", "$f18",  "$f19", "$f20",
+   7 "$f21",  "$f22", "$f23", "$f24", "$f25",  "$f26", "$f27",
+   6 "$f28",  "$f29", "$f30", "$f31", "$fcsr", "$fir"
+  */
+  return 8 + 8 + 8 + 8 + 9 + 8 + 7 + 7 + 6;
+}
+
+// See prototype for comments.
+int32_t parseDwarfExpr(Summariser* summ, const ByteReader* reader, string expr,
+                       bool debug, bool pushCfaAtStart, bool derefAtEnd) {
+  const char* cursor = expr.c_str();
+  const char* end1 = cursor + expr.length();
+
+  char buf[100];
+  if (debug) {
+    SprintfLiteral(buf, "LUL.DW  << DwarfExpr, len is %d\n",
+                   (int)(end1 - cursor));
+    summ->Log(buf);
+  }
+
+  // Add a marker for the start of this expression.  In it, indicate
+  // whether or not the CFA should be pushed onto the stack prior to
+  // evaluation.
+  int32_t start_ix =
+      summ->AddPfxInstr(PfxInstr(PX_Start, pushCfaAtStart ? 1 : 0));
+  MOZ_ASSERT(start_ix >= 0);
+
+  while (cursor < end1) {
+    uint8 opc = reader->ReadOneByte(cursor);
+    cursor++;
+
+    const char* nm = nullptr;
+    PfxExprOp pxop = PX_End;
+
+    switch (opc) {
+      case DW_OP_lit0 ... DW_OP_lit31: {
+        int32_t simm32 = (int32_t)(opc - DW_OP_lit0);
+        if (debug) {
+          SprintfLiteral(buf, "LUL.DW   DW_OP_lit%d\n", (int)simm32);
+          summ->Log(buf);
+        }
+        (void)summ->AddPfxInstr(PfxInstr(PX_SImm32, simm32));
+        break;
+      }
+
+      case DW_OP_breg0 ... DW_OP_breg31: {
+        size_t len;
+        int64_t n = reader->ReadSignedLEB128(cursor, &len);
+        cursor += len;
+        DW_REG_NUMBER reg = (DW_REG_NUMBER)(opc - DW_OP_breg0);
+        if (debug) {
+          SprintfLiteral(buf, "LUL.DW   DW_OP_breg%d %lld\n", (int)reg,
+                         (long long int)n);
+          summ->Log(buf);
+        }
+        // PfxInstr only allows a 32 bit signed offset.  So we
+        // must fail if the immediate is out of range.
+        if (n < INT32_MIN || INT32_MAX < n) goto fail;
+        (void)summ->AddPfxInstr(PfxInstr(PX_DwReg, reg));
+        (void)summ->AddPfxInstr(PfxInstr(PX_SImm32, (int32_t)n));
+        (void)summ->AddPfxInstr(PfxInstr(PX_Add));
+        break;
+      }
+
+      case DW_OP_const4s: {
+        uint64_t u64 = reader->ReadFourBytes(cursor);
+        cursor += 4;
+        // u64 is guaranteed by |ReadFourBytes| to be in the
+        // range 0 .. FFFFFFFF inclusive.  But to be safe:
+        uint32_t u32 = (uint32_t)(u64 & 0xFFFFFFFF);
+        int32_t s32 = (int32_t)u32;
+        if (debug) {
+          SprintfLiteral(buf, "LUL.DW   DW_OP_const4s %d\n", (int)s32);
+          summ->Log(buf);
+        }
+        (void)summ->AddPfxInstr(PfxInstr(PX_SImm32, s32));
+        break;
+      }
+
+      case DW_OP_deref:
+        nm = "deref";
+        pxop = PX_Deref;
+        goto no_operands;
+      case DW_OP_and:
+        nm = "and";
+        pxop = PX_And;
+        goto no_operands;
+      case DW_OP_plus:
+        nm = "plus";
+        pxop = PX_Add;
+        goto no_operands;
+      case DW_OP_minus:
+        nm = "minus";
+        pxop = PX_Sub;
+        goto no_operands;
+      case DW_OP_shl:
+        nm = "shl";
+        pxop = PX_Shl;
+        goto no_operands;
+      case DW_OP_ge:
+        nm = "ge";
+        pxop = PX_CmpGES;
+        goto no_operands;
+      no_operands:
+        MOZ_ASSERT(nm && pxop != PX_End);
+        if (debug) {
+          SprintfLiteral(buf, "LUL.DW   DW_OP_%s\n", nm);
+          summ->Log(buf);
+        }
+        (void)summ->AddPfxInstr(PfxInstr(pxop));
+        break;
+
+      default:
+        if (debug) {
+          SprintfLiteral(buf, "LUL.DW   unknown opc %d\n", (int)opc);
+          summ->Log(buf);
+        }
+        goto fail;
+
+    }  // switch (opc)
+
+  }  // while (cursor < end1)
+
+  MOZ_ASSERT(cursor >= end1);
+
+  if (cursor > end1) {
+    // We overran the Dwarf expression.  Give up.
+    goto fail;
+  }
+
+  // For DW_CFA_expression, what the expression denotes is the address
+  // of where the previous value is located.  The caller of this routine
+  // may therefore request one last dereference before the end marker is
+  // inserted.
+  if (derefAtEnd) {
+    (void)summ->AddPfxInstr(PfxInstr(PX_Deref));
+  }
+
+  // Insert an end marker, and declare success.
+  (void)summ->AddPfxInstr(PfxInstr(PX_End));
+  if (debug) {
+    SprintfLiteral(buf,
+                   "LUL.DW   conversion of dwarf expression succeeded, "
+                   "ix = %d\n",
+                   (int)start_ix);
+    summ->Log(buf);
+    summ->Log("LUL.DW  >>\n");
+  }
+  return start_ix;
+
+fail:
+  if (debug) {
+    summ->Log("LUL.DW   conversion of dwarf expression failed\n");
+    summ->Log("LUL.DW  >>\n");
+  }
+  return -1;
+}
+
+bool DwarfCFIToModule::Entry(size_t offset, uint64 address, uint64 length,
+                             uint8 version, const string& augmentation,
+                             unsigned return_address) {
+  if (DEBUG_DWARF) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL.DW DwarfCFIToModule::Entry 0x%llx,+%lld\n",
+                   address, length);
+    summ_->Log(buf);
+  }
+
+  summ_->Entry(address, length);
+
+  // If dwarf2reader::CallFrameInfo can handle this version and
+  // augmentation, then we should be okay with that, so there's no
+  // need to check them here.
+
+  // Get ready to collect entries.
+  return_address_ = return_address;
+
+  // Breakpad STACK CFI records must provide a .ra rule, but DWARF CFI
+  // may not establish any rule for .ra if the return address column
+  // is an ordinary register, and that register holds the return
+  // address on entry to the function. So establish an initial .ra
+  // rule citing the return address register.
+  if (return_address_ < num_dw_regs_) {
+    summ_->Rule(address, return_address_, NODEREF, return_address, 0);
+  }
+
+  return true;
+}
+
+const UniqueString* DwarfCFIToModule::RegisterName(int i) {
+  if (i < 0) {
+    MOZ_ASSERT(i == kCFARegister);
+    return usu_->ToUniqueString(".cfa");
+  }
+  unsigned reg = i;
+  if (reg == return_address_) return usu_->ToUniqueString(".ra");
+
+  char buf[30];
+  SprintfLiteral(buf, "dwarf_reg_%u", reg);
+  return usu_->ToUniqueString(buf);
+}
+
+bool DwarfCFIToModule::UndefinedRule(uint64 address, int reg) {
+  reporter_->UndefinedNotSupported(entry_offset_, RegisterName(reg));
+  // Treat this as a non-fatal error.
+  return true;
+}
+
+bool DwarfCFIToModule::SameValueRule(uint64 address, int reg) {
+  if (DEBUG_DWARF) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL.DW  0x%llx: old r%d = Same\n", address, reg);
+    summ_->Log(buf);
+  }
+  // reg + 0
+  summ_->Rule(address, reg, NODEREF, reg, 0);
+  return true;
+}
+
+bool DwarfCFIToModule::OffsetRule(uint64 address, int reg, int base_register,
+                                  long offset) {
+  if (DEBUG_DWARF) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL.DW  0x%llx: old r%d = *(r%d + %ld)\n", address,
+                   reg, base_register, offset);
+    summ_->Log(buf);
+  }
+  // *(base_register + offset)
+  summ_->Rule(address, reg, DEREF, base_register, offset);
+  return true;
+}
+
+bool DwarfCFIToModule::ValOffsetRule(uint64 address, int reg, int base_register,
+                                     long offset) {
+  if (DEBUG_DWARF) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL.DW  0x%llx: old r%d = r%d + %ld\n", address, reg,
+                   base_register, offset);
+    summ_->Log(buf);
+  }
+  // base_register + offset
+  summ_->Rule(address, reg, NODEREF, base_register, offset);
+  return true;
+}
+
+bool DwarfCFIToModule::RegisterRule(uint64 address, int reg,
+                                    int base_register) {
+  if (DEBUG_DWARF) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL.DW  0x%llx: old r%d = r%d\n", address, reg,
+                   base_register);
+    summ_->Log(buf);
+  }
+  // base_register + 0
+  summ_->Rule(address, reg, NODEREF, base_register, 0);
+  return true;
+}
+
+bool DwarfCFIToModule::ExpressionRule(uint64 address, int reg,
+                                      const string& expression) {
+  bool debug = !!DEBUG_DWARF;
+  int32_t start_ix =
+      parseDwarfExpr(summ_, reader_, expression, debug, true /*pushCfaAtStart*/,
+                     true /*derefAtEnd*/);
+  if (start_ix >= 0) {
+    summ_->Rule(address, reg, PFXEXPR, 0, start_ix);
+  } else {
+    // Parsing of the Dwarf expression failed.  Treat this as a
+    // non-fatal error, hence return |true| even on this path.
+    reporter_->ExpressionCouldNotBeSummarised(entry_offset_, RegisterName(reg));
+  }
+  return true;
+}
+
+bool DwarfCFIToModule::ValExpressionRule(uint64 address, int reg,
+                                         const string& expression) {
+  bool debug = !!DEBUG_DWARF;
+  int32_t start_ix =
+      parseDwarfExpr(summ_, reader_, expression, debug, true /*pushCfaAtStart*/,
+                     false /*!derefAtEnd*/);
+  if (start_ix >= 0) {
+    summ_->Rule(address, reg, PFXEXPR, 0, start_ix);
+  } else {
+    // Parsing of the Dwarf expression failed.  Treat this as a
+    // non-fatal error, hence return |true| even on this path.
+    reporter_->ExpressionCouldNotBeSummarised(entry_offset_, RegisterName(reg));
+  }
+  return true;
+}
+
+bool DwarfCFIToModule::End() {
+  // module_->AddStackFrameEntry(entry_);
+  if (DEBUG_DWARF) {
+    summ_->Log("LUL.DW DwarfCFIToModule::End()\n");
+  }
+  summ_->End();
+  return true;
+}
+
+void DwarfCFIToModule::Reporter::UndefinedNotSupported(
+    size_t offset, const UniqueString* reg) {
+  char buf[300];
+  SprintfLiteral(buf, "DwarfCFIToModule::Reporter::UndefinedNotSupported()\n");
+  log_(buf);
+  // BPLOG(INFO) << file_ << ", section '" << section_
+  //  << "': the call frame entry at offset 0x"
+  //  << std::setbase(16) << offset << std::setbase(10)
+  //  << " sets the rule for register '" << FromUniqueString(reg)
+  //  << "' to 'undefined', but the Breakpad symbol file format cannot "
+  //  << " express this";
+}
+
+// FIXME: move this somewhere sensible
+static bool is_power_of_2(uint64_t n) {
+  int i, nSetBits = 0;
+  for (i = 0; i < 8 * (int)sizeof(n); i++) {
+    if ((n & ((uint64_t)1) << i) != 0) nSetBits++;
+  }
+  return nSetBits <= 1;
+}
+
+void DwarfCFIToModule::Reporter::ExpressionCouldNotBeSummarised(
+    size_t offset, const UniqueString* reg) {
+  static uint64_t n_complaints = 0;  // This isn't threadsafe
+  n_complaints++;
+  if (!is_power_of_2(n_complaints)) return;
+  char buf[300];
+  SprintfLiteral(buf,
+                 "DwarfCFIToModule::Reporter::"
+                 "ExpressionCouldNotBeSummarised(shown %llu times)\n",
+                 (unsigned long long int)n_complaints);
+  log_(buf);
+}
+
+}  // namespace lul
diff --git a/mozglue/baseprofiler/lul/LulDwarfExt.h b/mozglue/baseprofiler/lul/LulDwarfExt.h
new file mode 100644
index 0000000000..dcd2500e5a
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulDwarfExt.h
@@ -0,0 +1,1289 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright 2006, 2010 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/dwarf/types.h
+//   src/common/dwarf/dwarf2enums.h
+//   src/common/dwarf/bytereader.h
+//   src/common/dwarf_cfi_to_module.h
+//   src/common/dwarf/dwarf2reader.h
+
+#ifndef LulDwarfExt_h
+#define LulDwarfExt_h
+
+#include "LulDwarfSummariser.h"
+
+#include "mozilla/Assertions.h"
+
+#include <stdint.h>
+#include <string>
+
+typedef signed char int8;
+typedef short int16;
+typedef int int32;
+typedef long long int64;
+
+typedef unsigned char uint8;
+typedef unsigned short uint16;
+typedef unsigned int uint32;
+typedef unsigned long long uint64;
+
+#ifdef __PTRDIFF_TYPE__
+typedef __PTRDIFF_TYPE__ intptr;
+typedef unsigned __PTRDIFF_TYPE__ uintptr;
+#else
+#  error "Can't find pointer-sized integral types."
+#endif
+
+namespace lul {
+
+class UniqueString;
+
+// Exception handling frame description pointer formats, as described
+// by the Linux Standard Base Core Specification 4.0, section 11.5,
+// DWARF Extensions.
+enum DwarfPointerEncoding {
+  DW_EH_PE_absptr = 0x00,
+  DW_EH_PE_omit = 0xff,
+  DW_EH_PE_uleb128 = 0x01,
+  DW_EH_PE_udata2 = 0x02,
+  DW_EH_PE_udata4 = 0x03,
+  DW_EH_PE_udata8 = 0x04,
+  DW_EH_PE_sleb128 = 0x09,
+  DW_EH_PE_sdata2 = 0x0A,
+  DW_EH_PE_sdata4 = 0x0B,
+  DW_EH_PE_sdata8 = 0x0C,
+  DW_EH_PE_pcrel = 0x10,
+  DW_EH_PE_textrel = 0x20,
+  DW_EH_PE_datarel = 0x30,
+  DW_EH_PE_funcrel = 0x40,
+  DW_EH_PE_aligned = 0x50,
+
+  // The GNU toolchain sources define this enum value as well,
+  // simply to help classify the lower nybble values into signed and
+  // unsigned groups.
+  DW_EH_PE_signed = 0x08,
+
+  // This is not documented in LSB 4.0, but it is used in both the
+  // Linux and OS X toolchains. It can be added to any other
+  // encoding (except DW_EH_PE_aligned), and indicates that the
+  // encoded value represents the address at which the true address
+  // is stored, not the true address itself.
+  DW_EH_PE_indirect = 0x80
+};
+
+// We can't use the obvious name of LITTLE_ENDIAN and BIG_ENDIAN
+// because it conflicts with a macro
+enum Endianness { ENDIANNESS_BIG, ENDIANNESS_LITTLE };
+
+// A ByteReader knows how to read single- and multi-byte values of
+// various endiannesses, sizes, and encodings, as used in DWARF
+// debugging information and Linux C++ exception handling data.
+class ByteReader {
+ public:
+  // Construct a ByteReader capable of reading one-, two-, four-, and
+  // eight-byte values according to ENDIANNESS, absolute machine-sized
+  // addresses, DWARF-style "initial length" values, signed and
+  // unsigned LEB128 numbers, and Linux C++ exception handling data's
+  // encoded pointers.
+  explicit ByteReader(enum Endianness endianness);
+  virtual ~ByteReader();
+
+  // Read a single byte from BUFFER and return it as an unsigned 8 bit
+  // number.
+  uint8 ReadOneByte(const char* buffer) const;
+
+  // Read two bytes from BUFFER and return them as an unsigned 16 bit
+  // number, using this ByteReader's endianness.
+  uint16 ReadTwoBytes(const char* buffer) const;
+
+  // Read four bytes from BUFFER and return them as an unsigned 32 bit
+  // number, using this ByteReader's endianness. This function returns
+  // a uint64 so that it is compatible with ReadAddress and
+  // ReadOffset. The number it returns will never be outside the range
+  // of an unsigned 32 bit integer.
+  uint64 ReadFourBytes(const char* buffer) const;
+
+  // Read eight bytes from BUFFER and return them as an unsigned 64
+  // bit number, using this ByteReader's endianness.
+  uint64 ReadEightBytes(const char* buffer) const;
+
+  // Read an unsigned LEB128 (Little Endian Base 128) number from
+  // BUFFER and return it as an unsigned 64 bit integer. Set LEN to
+  // the number of bytes read.
+  //
+  // The unsigned LEB128 representation of an integer N is a variable
+  // number of bytes:
+  //
+  // - If N is between 0 and 0x7f, then its unsigned LEB128
+  //   representation is a single byte whose value is N.
+  //
+  // - Otherwise, its unsigned LEB128 representation is (N & 0x7f) |
+  //   0x80, followed by the unsigned LEB128 representation of N /
+  //   128, rounded towards negative infinity.
+  //
+  // In other words, we break VALUE into groups of seven bits, put
+  // them in little-endian order, and then write them as eight-bit
+  // bytes with the high bit on all but the last.
+  uint64 ReadUnsignedLEB128(const char* buffer, size_t* len) const;
+
+  // Read a signed LEB128 number from BUFFER and return it as an
+  // signed 64 bit integer. Set LEN to the number of bytes read.
+  //
+  // The signed LEB128 representation of an integer N is a variable
+  // number of bytes:
+  //
+  // - If N is between -0x40 and 0x3f, then its signed LEB128
+  //   representation is a single byte whose value is N in two's
+  //   complement.
+  //
+  // - Otherwise, its signed LEB128 representation is (N & 0x7f) |
+  //   0x80, followed by the signed LEB128 representation of N / 128,
+  //   rounded towards negative infinity.
+  //
+  // In other words, we break VALUE into groups of seven bits, put
+  // them in little-endian order, and then write them as eight-bit
+  // bytes with the high bit on all but the last.
+  int64 ReadSignedLEB128(const char* buffer, size_t* len) const;
+
+  // Indicate that addresses on this architecture are SIZE bytes long. SIZE
+  // must be either 4 or 8. (DWARF allows addresses to be any number of
+  // bytes in length from 1 to 255, but we only support 32- and 64-bit
+  // addresses at the moment.) You must call this before using the
+  // ReadAddress member function.
+  //
+  // For data in a .debug_info section, or something that .debug_info
+  // refers to like line number or macro data, the compilation unit
+  // header's address_size field indicates the address size to use. Call
+  // frame information doesn't indicate its address size (a shortcoming of
+  // the spec); you must supply the appropriate size based on the
+  // architecture of the target machine.
+  void SetAddressSize(uint8 size);
+
+  // Return the current address size, in bytes. This is either 4,
+  // indicating 32-bit addresses, or 8, indicating 64-bit addresses.
+  uint8 AddressSize() const { return address_size_; }
+
+  // Read an address from BUFFER and return it as an unsigned 64 bit
+  // integer, respecting this ByteReader's endianness and address size. You
+  // must call SetAddressSize before calling this function.
+  uint64 ReadAddress(const char* buffer) const;
+
+  // DWARF actually defines two slightly different formats: 32-bit DWARF
+  // and 64-bit DWARF. This is *not* related to the size of registers or
+  // addresses on the target machine; it refers only to the size of section
+  // offsets and data lengths appearing in the DWARF data. One only needs
+  // 64-bit DWARF when the debugging data itself is larger than 4GiB.
+  // 32-bit DWARF can handle x86_64 or PPC64 code just fine, unless the
+  // debugging data itself is very large.
+  //
+  // DWARF information identifies itself as 32-bit or 64-bit DWARF: each
+  // compilation unit and call frame information entry begins with an
+  // "initial length" field, which, in addition to giving the length of the
+  // data, also indicates the size of section offsets and lengths appearing
+  // in that data. The ReadInitialLength member function, below, reads an
+  // initial length and sets the ByteReader's offset size as a side effect.
+  // Thus, in the normal process of reading DWARF data, the appropriate
+  // offset size is set automatically. So, you should only need to call
+  // SetOffsetSize if you are using the same ByteReader to jump from the
+  // midst of one block of DWARF data into another.
+
+  // Read a DWARF "initial length" field from START, and return it as
+  // an unsigned 64 bit integer, respecting this ByteReader's
+  // endianness. Set *LEN to the length of the initial length in
+  // bytes, either four or twelve. As a side effect, set this
+  // ByteReader's offset size to either 4 (if we see a 32-bit DWARF
+  // initial length) or 8 (if we see a 64-bit DWARF initial length).
+  //
+  // A DWARF initial length is either:
+  //
+  // - a byte count stored as an unsigned 32-bit value less than
+  //   0xffffff00, indicating that the data whose length is being
+  //   measured uses the 32-bit DWARF format, or
+  //
+  // - The 32-bit value 0xffffffff, followed by a 64-bit byte count,
+  //   indicating that the data whose length is being measured uses
+  //   the 64-bit DWARF format.
+  uint64 ReadInitialLength(const char* start, size_t* len);
+
+  // Read an offset from BUFFER and return it as an unsigned 64 bit
+  // integer, respecting the ByteReader's endianness. In 32-bit DWARF, the
+  // offset is 4 bytes long; in 64-bit DWARF, the offset is eight bytes
+  // long. You must call ReadInitialLength or SetOffsetSize before calling
+  // this function; see the comments above for details.
+  uint64 ReadOffset(const char* buffer) const;
+
+  // Return the current offset size, in bytes.
+  // A return value of 4 indicates that we are reading 32-bit DWARF.
+  // A return value of 8 indicates that we are reading 64-bit DWARF.
+  uint8 OffsetSize() const { return offset_size_; }
+
+  // Indicate that section offsets and lengths are SIZE bytes long. SIZE
+  // must be either 4 (meaning 32-bit DWARF) or 8 (meaning 64-bit DWARF).
+  // Usually, you should not call this function yourself; instead, let a
+  // call to ReadInitialLength establish the data's offset size
+  // automatically.
+  void SetOffsetSize(uint8 size);
+
+  // The Linux C++ ABI uses a variant of DWARF call frame information
+  // for exception handling. This data is included in the program's
+  // address space as the ".eh_frame" section, and intepreted at
+  // runtime to walk the stack, find exception handlers, and run
+  // cleanup code. The format is mostly the same as DWARF CFI, with
+  // some adjustments made to provide the additional
+  // exception-handling data, and to make the data easier to work with
+  // in memory --- for example, to allow it to be placed in read-only
+  // memory even when describing position-independent code.
+  //
+  // In particular, exception handling data can select a number of
+  // different encodings for pointers that appear in the data, as
+  // described by the DwarfPointerEncoding enum. There are actually
+  // four axes(!) to the encoding:
+  //
+  // - The pointer size: pointers can be 2, 4, or 8 bytes long, or use
+  //   the DWARF LEB128 encoding.
+  //
+  // - The pointer's signedness: pointers can be signed or unsigned.
+  //
+  // - The pointer's base address: the data stored in the exception
+  //   handling data can be the actual address (that is, an absolute
+  //   pointer), or relative to one of a number of different base
+  //   addreses --- including that of the encoded pointer itself, for
+  //   a form of "pc-relative" addressing.
+  //
+  // - The pointer may be indirect: it may be the address where the
+  //   true pointer is stored. (This is used to refer to things via
+  //   global offset table entries, program linkage table entries, or
+  //   other tricks used in position-independent code.)
+  //
+  // There are also two options that fall outside that matrix
+  // altogether: the pointer may be omitted, or it may have padding to
+  // align it on an appropriate address boundary. (That last option
+  // may seem like it should be just another axis, but it is not.)
+
+  // Indicate that the exception handling data is loaded starting at
+  // SECTION_BASE, and that the start of its buffer in our own memory
+  // is BUFFER_BASE. This allows us to find the address that a given
+  // byte in our buffer would have when loaded into the program the
+  // data describes. We need this to resolve DW_EH_PE_pcrel pointers.
+  void SetCFIDataBase(uint64 section_base, const char* buffer_base);
+
+  // Indicate that the base address of the program's ".text" section
+  // is TEXT_BASE. We need this to resolve DW_EH_PE_textrel pointers.
+  void SetTextBase(uint64 text_base);
+
+  // Indicate that the base address for DW_EH_PE_datarel pointers is
+  // DATA_BASE. The proper value depends on the ABI; it is usually the
+  // address of the global offset table, held in a designated register in
+  // position-independent code. You will need to look at the startup code
+  // for the target system to be sure. I tried; my eyes bled.
+  void SetDataBase(uint64 data_base);
+
+  // Indicate that the base address for the FDE we are processing is
+  // FUNCTION_BASE. This is the start address of DW_EH_PE_funcrel
+  // pointers. (This encoding does not seem to be used by the GNU
+  // toolchain.)
+  void SetFunctionBase(uint64 function_base);
+
+  // Indicate that we are no longer processing any FDE, so any use of
+  // a DW_EH_PE_funcrel encoding is an error.
+  void ClearFunctionBase();
+
+  // Return true if ENCODING is a valid pointer encoding.
+  bool ValidEncoding(DwarfPointerEncoding encoding) const;
+
+  // Return true if we have all the information we need to read a
+  // pointer that uses ENCODING. This checks that the appropriate
+  // SetFooBase function for ENCODING has been called.
+  bool UsableEncoding(DwarfPointerEncoding encoding) const;
+
+  // Read an encoded pointer from BUFFER using ENCODING; return the
+  // absolute address it represents, and set *LEN to the pointer's
+  // length in bytes, including any padding for aligned pointers.
+  //
+  // This function calls 'abort' if ENCODING is invalid or refers to a
+  // base address this reader hasn't been given, so you should check
+  // with ValidEncoding and UsableEncoding first if you would rather
+  // die in a more helpful way.
+  uint64 ReadEncodedPointer(const char* buffer, DwarfPointerEncoding encoding,
+                            size_t* len) const;
+
+ private:
+  // Function pointer type for our address and offset readers.
+  typedef uint64 (ByteReader::*AddressReader)(const char*) const;
+
+  // Read an offset from BUFFER and return it as an unsigned 64 bit
+  // integer.  DWARF2/3 define offsets as either 4 or 8 bytes,
+  // generally depending on the amount of DWARF2/3 info present.
+  // This function pointer gets set by SetOffsetSize.
+  AddressReader offset_reader_;
+
+  // Read an address from BUFFER and return it as an unsigned 64 bit
+  // integer.  DWARF2/3 allow addresses to be any size from 0-255
+  // bytes currently.  Internally we support 4 and 8 byte addresses,
+  // and will CHECK on anything else.
+  // This function pointer gets set by SetAddressSize.
+  AddressReader address_reader_;
+
+  Endianness endian_;
+  uint8 address_size_;
+  uint8 offset_size_;
+
+  // Base addresses for Linux C++ exception handling data's encoded pointers.
+  bool have_section_base_, have_text_base_, have_data_base_;
+  bool have_function_base_;
+  uint64 section_base_;
+  uint64 text_base_, data_base_, function_base_;
+  const char* buffer_base_;
+};
+
+inline uint8 ByteReader::ReadOneByte(const char* buffer) const {
+  return buffer[0];
+}
+
+inline uint16 ByteReader::ReadTwoBytes(const char* signed_buffer) const {
+  const unsigned char* buffer =
+      reinterpret_cast<const unsigned char*>(signed_buffer);
+  const uint16 buffer0 = buffer[0];
+  const uint16 buffer1 = buffer[1];
+  if (endian_ == ENDIANNESS_LITTLE) {
+    return buffer0 | buffer1 << 8;
+  } else {
+    return buffer1 | buffer0 << 8;
+  }
+}
+
+inline uint64 ByteReader::ReadFourBytes(const char* signed_buffer) const {
+  const unsigned char* buffer =
+      reinterpret_cast<const unsigned char*>(signed_buffer);
+  const uint32 buffer0 = buffer[0];
+  const uint32 buffer1 = buffer[1];
+  const uint32 buffer2 = buffer[2];
+  const uint32 buffer3 = buffer[3];
+  if (endian_ == ENDIANNESS_LITTLE) {
+    return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24;
+  } else {
+    return buffer3 | buffer2 << 8 | buffer1 << 16 | buffer0 << 24;
+  }
+}
+
+inline uint64 ByteReader::ReadEightBytes(const char* signed_buffer) const {
+  const unsigned char* buffer =
+      reinterpret_cast<const unsigned char*>(signed_buffer);
+  const uint64 buffer0 = buffer[0];
+  const uint64 buffer1 = buffer[1];
+  const uint64 buffer2 = buffer[2];
+  const uint64 buffer3 = buffer[3];
+  const uint64 buffer4 = buffer[4];
+  const uint64 buffer5 = buffer[5];
+  const uint64 buffer6 = buffer[6];
+  const uint64 buffer7 = buffer[7];
+  if (endian_ == ENDIANNESS_LITTLE) {
+    return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24 |
+           buffer4 << 32 | buffer5 << 40 | buffer6 << 48 | buffer7 << 56;
+  } else {
+    return buffer7 | buffer6 << 8 | buffer5 << 16 | buffer4 << 24 |
+           buffer3 << 32 | buffer2 << 40 | buffer1 << 48 | buffer0 << 56;
+  }
+}
+
+// Read an unsigned LEB128 number.  Each byte contains 7 bits of
+// information, plus one bit saying whether the number continues or
+// not.
+
+inline uint64 ByteReader::ReadUnsignedLEB128(const char* buffer,
+                                             size_t* len) const {
+  uint64 result = 0;
+  size_t num_read = 0;
+  unsigned int shift = 0;
+  unsigned char byte;
+
+  do {
+    byte = *buffer++;
+    num_read++;
+
+    result |= (static_cast<uint64>(byte & 0x7f)) << shift;
+
+    shift += 7;
+
+  } while (byte & 0x80);
+
+  *len = num_read;
+
+  return result;
+}
+
+// Read a signed LEB128 number.  These are like regular LEB128
+// numbers, except the last byte may have a sign bit set.
+
+inline int64 ByteReader::ReadSignedLEB128(const char* buffer,
+                                          size_t* len) const {
+  int64 result = 0;
+  unsigned int shift = 0;
+  size_t num_read = 0;
+  unsigned char byte;
+
+  do {
+    byte = *buffer++;
+    num_read++;
+    result |= (static_cast<uint64>(byte & 0x7f) << shift);
+    shift += 7;
+  } while (byte & 0x80);
+
+  if ((shift < 8 * sizeof(result)) && (byte & 0x40))
+    result |= -((static_cast<int64>(1)) << shift);
+  *len = num_read;
+  return result;
+}
+
+inline uint64 ByteReader::ReadOffset(const char* buffer) const {
+  MOZ_ASSERT(this->offset_reader_);
+  return (this->*offset_reader_)(buffer);
+}
+
+inline uint64 ByteReader::ReadAddress(const char* buffer) const {
+  MOZ_ASSERT(this->address_reader_);
+  return (this->*address_reader_)(buffer);
+}
+
+inline void ByteReader::SetCFIDataBase(uint64 section_base,
+                                       const char* buffer_base) {
+  section_base_ = section_base;
+  buffer_base_ = buffer_base;
+  have_section_base_ = true;
+}
+
+inline void ByteReader::SetTextBase(uint64 text_base) {
+  text_base_ = text_base;
+  have_text_base_ = true;
+}
+
+inline void ByteReader::SetDataBase(uint64 data_base) {
+  data_base_ = data_base;
+  have_data_base_ = true;
+}
+
+inline void ByteReader::SetFunctionBase(uint64 function_base) {
+  function_base_ = function_base;
+  have_function_base_ = true;
+}
+
+inline void ByteReader::ClearFunctionBase() { have_function_base_ = false; }
+
+// (derived from)
+// dwarf_cfi_to_module.h: Define the DwarfCFIToModule class, which
+// accepts parsed DWARF call frame info and adds it to a Summariser object.
+
+// This class is a reader for DWARF's Call Frame Information.  CFI
+// describes how to unwind stack frames --- even for functions that do
+// not follow fixed conventions for saving registers, whose frame size
+// varies as they execute, etc.
+//
+// CFI describes, at each machine instruction, how to compute the
+// stack frame's base address, how to find the return address, and
+// where to find the saved values of the caller's registers (if the
+// callee has stashed them somewhere to free up the registers for its
+// own use).
+//
+// For example, suppose we have a function whose machine code looks
+// like this (imagine an assembly language that looks like C, for a
+// machine with 32-bit registers, and a stack that grows towards lower
+// addresses):
+//
+// func:                                ; entry point; return address at sp
+// func+0:      sp = sp - 16            ; allocate space for stack frame
+// func+1:      sp[12] = r0             ; save r0 at sp+12
+// ...                                  ; other code, not frame-related
+// func+10:     sp -= 4; *sp = x        ; push some x on the stack
+// ...                                  ; other code, not frame-related
+// func+20:     r0 = sp[16]             ; restore saved r0
+// func+21:     sp += 20                ; pop whole stack frame
+// func+22:     pc = *sp; sp += 4       ; pop return address and jump to it
+//
+// DWARF CFI is (a very compressed representation of) a table with a
+// row for each machine instruction address and a column for each
+// register showing how to restore it, if possible.
+//
+// A special column named "CFA", for "Canonical Frame Address", tells how
+// to compute the base address of the frame; registers' entries may
+// refer to the CFA in describing where the registers are saved.
+//
+// Another special column, named "RA", represents the return address.
+//
+// For example, here is a complete (uncompressed) table describing the
+// function above:
+//
+//     insn      cfa    r0      r1 ...  ra
+//     =======================================
+//     func+0:   sp                     cfa[0]
+//     func+1:   sp+16                  cfa[0]
+//     func+2:   sp+16  cfa[-4]         cfa[0]
+//     func+11:  sp+20  cfa[-4]         cfa[0]
+//     func+21:  sp+20                  cfa[0]
+//     func+22:  sp                     cfa[0]
+//
+// Some things to note here:
+//
+// - Each row describes the state of affairs *before* executing the
+//   instruction at the given address.  Thus, the row for func+0
+//   describes the state before we allocate the stack frame.  In the
+//   next row, the formula for computing the CFA has changed,
+//   reflecting that allocation.
+//
+// - The other entries are written in terms of the CFA; this allows
+//   them to remain unchanged as the stack pointer gets bumped around.
+//   For example, the rule for recovering the return address (the "ra"
+//   column) remains unchanged throughout the function, even as the
+//   stack pointer takes on three different offsets from the return
+//   address.
+//
+// - Although we haven't shown it, most calling conventions designate
+//   "callee-saves" and "caller-saves" registers. The callee must
+//   preserve the values of callee-saves registers; if it uses them,
+//   it must save their original values somewhere, and restore them
+//   before it returns. In contrast, the callee is free to trash
+//   caller-saves registers; if the callee uses these, it will
+//   probably not bother to save them anywhere, and the CFI will
+//   probably mark their values as "unrecoverable".
+//
+//   (However, since the caller cannot assume the callee was going to
+//   save them, caller-saves registers are probably dead in the caller
+//   anyway, so compilers usually don't generate CFA for caller-saves
+//   registers.)
+//
+// - Exactly where the CFA points is a matter of convention that
+//   depends on the architecture and ABI in use. In the example, the
+//   CFA is the value the stack pointer had upon entry to the
+//   function, pointing at the saved return address. But on the x86,
+//   the call frame information generated by GCC follows the
+//   convention that the CFA is the address *after* the saved return
+//   address.
+//
+//   But by definition, the CFA remains constant throughout the
+//   lifetime of the frame. This makes it a useful value for other
+//   columns to refer to. It is also gives debuggers a useful handle
+//   for identifying a frame.
+//
+// If you look at the table above, you'll notice that a given entry is
+// often the same as the one immediately above it: most instructions
+// change only one or two aspects of the stack frame, if they affect
+// it at all. The DWARF format takes advantage of this fact, and
+// reduces the size of the data by mentioning only the addresses and
+// columns at which changes take place. So for the above, DWARF CFI
+// data would only actually mention the following:
+//
+//     insn      cfa    r0      r1 ...  ra
+//     =======================================
+//     func+0:   sp                     cfa[0]
+//     func+1:   sp+16
+//     func+2:          cfa[-4]
+//     func+11:  sp+20
+//     func+21:         r0
+//     func+22:  sp
+//
+// In fact, this is the way the parser reports CFI to the consumer: as
+// a series of statements of the form, "At address X, column Y changed
+// to Z," and related conventions for describing the initial state.
+//
+// Naturally, it would be impractical to have to scan the entire
+// program's CFI, noting changes as we go, just to recover the
+// unwinding rules in effect at one particular instruction. To avoid
+// this, CFI data is grouped into "entries", each of which covers a
+// specified range of addresses and begins with a complete statement
+// of the rules for all recoverable registers at that starting
+// address. Each entry typically covers a single function.
+//
+// Thus, to compute the contents of a given row of the table --- that
+// is, rules for recovering the CFA, RA, and registers at a given
+// instruction --- the consumer should find the entry that covers that
+// instruction's address, start with the initial state supplied at the
+// beginning of the entry, and work forward until it has processed all
+// the changes up to and including those for the present instruction.
+//
+// There are seven kinds of rules that can appear in an entry of the
+// table:
+//
+// - "undefined": The given register is not preserved by the callee;
+//   its value cannot be recovered.
+//
+// - "same value": This register has the same value it did in the callee.
+//
+// - offset(N): The register is saved at offset N from the CFA.
+//
+// - val_offset(N): The value the register had in the caller is the
+//   CFA plus offset N. (This is usually only useful for describing
+//   the stack pointer.)
+//
+// - register(R): The register's value was saved in another register R.
+//
+// - expression(E): Evaluating the DWARF expression E using the
+//   current frame's registers' values yields the address at which the
+//   register was saved.
+//
+// - val_expression(E): Evaluating the DWARF expression E using the
+//   current frame's registers' values yields the value the register
+//   had in the caller.
+
+class CallFrameInfo {
+ public:
+  // The different kinds of entries one finds in CFI. Used internally,
+  // and for error reporting.
+  enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
+
+  // The handler class to which the parser hands the parsed call frame
+  // information.  Defined below.
+  class Handler;
+
+  // A reporter class, which CallFrameInfo uses to report errors
+  // encountered while parsing call frame information.  Defined below.
+  class Reporter;
+
+  // Create a DWARF CFI parser. BUFFER points to the contents of the
+  // .debug_frame section to parse; BUFFER_LENGTH is its length in bytes.
+  // REPORTER is an error reporter the parser should use to report
+  // problems. READER is a ByteReader instance that has the endianness and
+  // address size set properly. Report the data we find to HANDLER.
+  //
+  // This class can also parse Linux C++ exception handling data, as found
+  // in '.eh_frame' sections. This data is a variant of DWARF CFI that is
+  // placed in loadable segments so that it is present in the program's
+  // address space, and is interpreted by the C++ runtime to search the
+  // call stack for a handler interested in the exception being thrown,
+  // actually pop the frames, and find cleanup code to run.
+  //
+  // There are two differences between the call frame information described
+  // in the DWARF standard and the exception handling data Linux places in
+  // the .eh_frame section:
+  //
+  // - Exception handling data uses uses a different format for call frame
+  //   information entry headers. The distinguished CIE id, the way FDEs
+  //   refer to their CIEs, and the way the end of the series of entries is
+  //   determined are all slightly different.
+  //
+  //   If the constructor's EH_FRAME argument is true, then the
+  //   CallFrameInfo parses the entry headers as Linux C++ exception
+  //   handling data. If EH_FRAME is false or omitted, the CallFrameInfo
+  //   parses standard DWARF call frame information.
+  //
+  // - Linux C++ exception handling data uses CIE augmentation strings
+  //   beginning with 'z' to specify the presence of additional data after
+  //   the CIE and FDE headers and special encodings used for addresses in
+  //   frame description entries.
+  //
+  //   CallFrameInfo can handle 'z' augmentations in either DWARF CFI or
+  //   exception handling data if you have supplied READER with the base
+  //   addresses needed to interpret the pointer encodings that 'z'
+  //   augmentations can specify. See the ByteReader interface for details
+  //   about the base addresses. See the CallFrameInfo::Handler interface
+  //   for details about the additional information one might find in
+  //   'z'-augmented data.
+  //
+  // Thus:
+  //
+  // - If you are parsing standard DWARF CFI, as found in a .debug_frame
+  //   section, you should pass false for the EH_FRAME argument, or omit
+  //   it, and you need not worry about providing READER with the
+  //   additional base addresses.
+  //
+  // - If you want to parse Linux C++ exception handling data from a
+  //   .eh_frame section, you should pass EH_FRAME as true, and call
+  //   READER's Set*Base member functions before calling our Start method.
+  //
+  // - If you want to parse DWARF CFI that uses the 'z' augmentations
+  //   (although I don't think any toolchain ever emits such data), you
+  //   could pass false for EH_FRAME, but call READER's Set*Base members.
+  //
+  // The extensions the Linux C++ ABI makes to DWARF for exception
+  // handling are described here, rather poorly:
+  // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html
+  // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
+  //
+  // The mechanics of C++ exception handling, personality routines,
+  // and language-specific data areas are described here, rather nicely:
+  // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
+
+  CallFrameInfo(const char* buffer, size_t buffer_length, ByteReader* reader,
+                Handler* handler, Reporter* reporter, bool eh_frame = false)
+      : buffer_(buffer),
+        buffer_length_(buffer_length),
+        reader_(reader),
+        handler_(handler),
+        reporter_(reporter),
+        eh_frame_(eh_frame) {}
+
+  ~CallFrameInfo() {}
+
+  // Parse the entries in BUFFER, reporting what we find to HANDLER.
+  // Return true if we reach the end of the section successfully, or
+  // false if we encounter an error.
+  bool Start();
+
+  // Return the textual name of KIND. For error reporting.
+  static const char* KindName(EntryKind kind);
+
+ private:
+  struct CIE;
+
+  // A CFI entry, either an FDE or a CIE.
+  struct Entry {
+    // The starting offset of the entry in the section, for error
+    // reporting.
+    size_t offset;
+
+    // The start of this entry in the buffer.
+    const char* start;
+
+    // Which kind of entry this is.
+    //
+    // We want to be able to use this for error reporting even while we're
+    // in the midst of parsing. Error reporting code may assume that kind,
+    // offset, and start fields are valid, although kind may be kUnknown.
+    EntryKind kind;
+
+    // The end of this entry's common prologue (initial length and id), and
+    // the start of this entry's kind-specific fields.
+    const char* fields;
+
+    // The start of this entry's instructions.
+    const char* instructions;
+
+    // The address past the entry's last byte in the buffer. (Note that
+    // since offset points to the entry's initial length field, and the
+    // length field is the number of bytes after that field, this is not
+    // simply buffer_ + offset + length.)
+    const char* end;
+
+    // For both DWARF CFI and .eh_frame sections, this is the CIE id in a
+    // CIE, and the offset of the associated CIE in an FDE.
+    uint64 id;
+
+    // The CIE that applies to this entry, if we've parsed it. If this is a
+    // CIE, then this field points to this structure.
+    CIE* cie;
+  };
+
+  // A common information entry (CIE).
+  struct CIE : public Entry {
+    uint8 version;                     // CFI data version number
+    std::string augmentation;          // vendor format extension markers
+    uint64 code_alignment_factor;      // scale for code address adjustments
+    int data_alignment_factor;         // scale for stack pointer adjustments
+    unsigned return_address_register;  // which register holds the return addr
+
+    // True if this CIE includes Linux C++ ABI 'z' augmentation data.
+    bool has_z_augmentation;
+
+    // Parsed 'z' augmentation data. These are meaningful only if
+    // has_z_augmentation is true.
+    bool has_z_lsda;          // The 'z' augmentation included 'L'.
+    bool has_z_personality;   // The 'z' augmentation included 'P'.
+    bool has_z_signal_frame;  // The 'z' augmentation included 'S'.
+
+    // If has_z_lsda is true, this is the encoding to be used for language-
+    // specific data area pointers in FDEs.
+    DwarfPointerEncoding lsda_encoding;
+
+    // If has_z_personality is true, this is the encoding used for the
+    // personality routine pointer in the augmentation data.
+    DwarfPointerEncoding personality_encoding;
+
+    // If has_z_personality is true, this is the address of the personality
+    // routine --- or, if personality_encoding & DW_EH_PE_indirect, the
+    // address where the personality routine's address is stored.
+    uint64 personality_address;
+
+    // This is the encoding used for addresses in the FDE header and
+    // in DW_CFA_set_loc instructions. This is always valid, whether
+    // or not we saw a 'z' augmentation string; its default value is
+    // DW_EH_PE_absptr, which is what normal DWARF CFI uses.
+    DwarfPointerEncoding pointer_encoding;
+  };
+
+  // A frame description entry (FDE).
+  struct FDE : public Entry {
+    uint64 address;  // start address of described code
+    uint64 size;     // size of described code, in bytes
+
+    // If cie->has_z_lsda is true, then this is the language-specific data
+    // area's address --- or its address's address, if cie->lsda_encoding
+    // has the DW_EH_PE_indirect bit set.
+    uint64 lsda_address;
+  };
+
+  // Internal use.
+  class Rule;
+  class UndefinedRule;
+  class SameValueRule;
+  class OffsetRule;
+  class ValOffsetRule;
+  class RegisterRule;
+  class ExpressionRule;
+  class ValExpressionRule;
+  class RuleMap;
+  class State;
+
+  // Parse the initial length and id of a CFI entry, either a CIE, an FDE,
+  // or a .eh_frame end-of-data mark. CURSOR points to the beginning of the
+  // data to parse. On success, populate ENTRY as appropriate, and return
+  // true. On failure, report the problem, and return false. Even if we
+  // return false, set ENTRY->end to the first byte after the entry if we
+  // were able to figure that out, or NULL if we weren't.
+  bool ReadEntryPrologue(const char* cursor, Entry* entry);
+
+  // Parse the fields of a CIE after the entry prologue, including any 'z'
+  // augmentation data. Assume that the 'Entry' fields of CIE are
+  // populated; use CIE->fields and CIE->end as the start and limit for
+  // parsing. On success, populate the rest of *CIE, and return true; on
+  // failure, report the problem and return false.
+  bool ReadCIEFields(CIE* cie);
+
+  // Parse the fields of an FDE after the entry prologue, including any 'z'
+  // augmentation data. Assume that the 'Entry' fields of *FDE are
+  // initialized; use FDE->fields and FDE->end as the start and limit for
+  // parsing. Assume that FDE->cie is fully initialized. On success,
+  // populate the rest of *FDE, and return true; on failure, report the
+  // problem and return false.
+  bool ReadFDEFields(FDE* fde);
+
+  // Report that ENTRY is incomplete, and return false. This is just a
+  // trivial wrapper for invoking reporter_->Incomplete; it provides a
+  // little brevity.
+  bool ReportIncomplete(Entry* entry);
+
+  // Return true if ENCODING has the DW_EH_PE_indirect bit set.
+  static bool IsIndirectEncoding(DwarfPointerEncoding encoding) {
+    return encoding & DW_EH_PE_indirect;
+  }
+
+  // The contents of the DWARF .debug_info section we're parsing.
+  const char* buffer_;
+  size_t buffer_length_;
+
+  // For reading multi-byte values with the appropriate endianness.
+  ByteReader* reader_;
+
+  // The handler to which we should report the data we find.
+  Handler* handler_;
+
+  // For reporting problems in the info we're parsing.
+  Reporter* reporter_;
+
+  // True if we are processing .eh_frame-format data.
+  bool eh_frame_;
+};
+
+// The handler class for CallFrameInfo.  The a CFI parser calls the
+// member functions of a handler object to report the data it finds.
+class CallFrameInfo::Handler {
+ public:
+  // The pseudo-register number for the canonical frame address.
+  enum { kCFARegister = DW_REG_CFA };
+
+  Handler() {}
+  virtual ~Handler() {}
+
+  // The parser has found CFI for the machine code at ADDRESS,
+  // extending for LENGTH bytes. OFFSET is the offset of the frame
+  // description entry in the section, for use in error messages.
+  // VERSION is the version number of the CFI format. AUGMENTATION is
+  // a string describing any producer-specific extensions present in
+  // the data. RETURN_ADDRESS is the number of the register that holds
+  // the address to which the function should return.
+  //
+  // Entry should return true to process this CFI, or false to skip to
+  // the next entry.
+  //
+  // The parser invokes Entry for each Frame Description Entry (FDE)
+  // it finds.  The parser doesn't report Common Information Entries
+  // to the handler explicitly; instead, if the handler elects to
+  // process a given FDE, the parser reiterates the appropriate CIE's
+  // contents at the beginning of the FDE's rules.
+  virtual bool Entry(size_t offset, uint64 address, uint64 length,
+                     uint8 version, const std::string& augmentation,
+                     unsigned return_address) = 0;
+
+  // When the Entry function returns true, the parser calls these
+  // handler functions repeatedly to describe the rules for recovering
+  // registers at each instruction in the given range of machine code.
+  // Immediately after a call to Entry, the handler should assume that
+  // the rule for each callee-saves register is "unchanged" --- that
+  // is, that the register still has the value it had in the caller.
+  //
+  // If a *Rule function returns true, we continue processing this entry's
+  // instructions. If a *Rule function returns false, we stop evaluating
+  // instructions, and skip to the next entry. Either way, we call End
+  // before going on to the next entry.
+  //
+  // In all of these functions, if the REG parameter is kCFARegister, then
+  // the rule describes how to find the canonical frame address.
+  // kCFARegister may be passed as a BASE_REGISTER argument, meaning that
+  // the canonical frame address should be used as the base address for the
+  // computation. All other REG values will be positive.
+
+  // At ADDRESS, register REG's value is not recoverable.
+  virtual bool UndefinedRule(uint64 address, int reg) = 0;
+
+  // At ADDRESS, register REG's value is the same as that it had in
+  // the caller.
+  virtual bool SameValueRule(uint64 address, int reg) = 0;
+
+  // At ADDRESS, register REG has been saved at offset OFFSET from
+  // BASE_REGISTER.
+  virtual bool OffsetRule(uint64 address, int reg, int base_register,
+                          long offset) = 0;
+
+  // At ADDRESS, the caller's value of register REG is the current
+  // value of BASE_REGISTER plus OFFSET. (This rule doesn't provide an
+  // address at which the register's value is saved.)
+  virtual bool ValOffsetRule(uint64 address, int reg, int base_register,
+                             long offset) = 0;
+
+  // At ADDRESS, register REG has been saved in BASE_REGISTER. This differs
+  // from ValOffsetRule(ADDRESS, REG, BASE_REGISTER, 0), in that
+  // BASE_REGISTER is the "home" for REG's saved value: if you want to
+  // assign to a variable whose home is REG in the calling frame, you
+  // should put the value in BASE_REGISTER.
+  virtual bool RegisterRule(uint64 address, int reg, int base_register) = 0;
+
+  // At ADDRESS, the DWARF expression EXPRESSION yields the address at
+  // which REG was saved.
+  virtual bool ExpressionRule(uint64 address, int reg,
+                              const std::string& expression) = 0;
+
+  // At ADDRESS, the DWARF expression EXPRESSION yields the caller's
+  // value for REG. (This rule doesn't provide an address at which the
+  // register's value is saved.)
+  virtual bool ValExpressionRule(uint64 address, int reg,
+                                 const std::string& expression) = 0;
+
+  // Indicate that the rules for the address range reported by the
+  // last call to Entry are complete.  End should return true if
+  // everything is okay, or false if an error has occurred and parsing
+  // should stop.
+  virtual bool End() = 0;
+
+  // Handler functions for Linux C++ exception handling data. These are
+  // only called if the data includes 'z' augmentation strings.
+
+  // The Linux C++ ABI uses an extension of the DWARF CFI format to
+  // walk the stack to propagate exceptions from the throw to the
+  // appropriate catch, and do the appropriate cleanups along the way.
+  // CFI entries used for exception handling have two additional data
+  // associated with them:
+  //
+  // - The "language-specific data area" describes which exception
+  //   types the function has 'catch' clauses for, and indicates how
+  //   to go about re-entering the function at the appropriate catch
+  //   clause. If the exception is not caught, it describes the
+  //   destructors that must run before the frame is popped.
+  //
+  // - The "personality routine" is responsible for interpreting the
+  //   language-specific data area's contents, and deciding whether
+  //   the exception should continue to propagate down the stack,
+  //   perhaps after doing some cleanup for this frame, or whether the
+  //   exception will be caught here.
+  //
+  // In principle, the language-specific data area is opaque to
+  // everybody but the personality routine. In practice, these values
+  // may be useful or interesting to readers with extra context, and
+  // we have to at least skip them anyway, so we might as well report
+  // them to the handler.
+
+  // This entry's exception handling personality routine's address is
+  // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
+  // which the routine's address is stored. The default definition for
+  // this handler function simply returns true, allowing parsing of
+  // the entry to continue.
+  virtual bool PersonalityRoutine(uint64 address, bool indirect) {
+    return true;
+  }
+
+  // This entry's language-specific data area (LSDA) is located at
+  // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
+  // which the area's address is stored. The default definition for
+  // this handler function simply returns true, allowing parsing of
+  // the entry to continue.
+  virtual bool LanguageSpecificDataArea(uint64 address, bool indirect) {
+    return true;
+  }
+
+  // This entry describes a signal trampoline --- this frame is the
+  // caller of a signal handler. The default definition for this
+  // handler function simply returns true, allowing parsing of the
+  // entry to continue.
+  //
+  // The best description of the rationale for and meaning of signal
+  // trampoline CFI entries seems to be in the GCC bug database:
+  // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
+  virtual bool SignalHandler() { return true; }
+};
+
+// The CallFrameInfo class makes calls on an instance of this class to
+// report errors or warn about problems in the data it is parsing.
+// These messages are sent to the message sink |aLog| provided to the
+// constructor.
+class CallFrameInfo::Reporter {
+ public:
+  // Create an error reporter which attributes troubles to the section
+  // named SECTION in FILENAME.
+  //
+  // Normally SECTION would be .debug_frame, but the Mac puts CFI data
+  // in a Mach-O section named __debug_frame. If we support
+  // Linux-style exception handling data, we could be reading an
+  // .eh_frame section.
+  Reporter(void (*aLog)(const char*), const std::string& filename,
+           const std::string& section = ".debug_frame")
+      : log_(aLog), filename_(filename), section_(section) {}
+  virtual ~Reporter() {}
+
+  // The CFI entry at OFFSET ends too early to be well-formed. KIND
+  // indicates what kind of entry it is; KIND can be kUnknown if we
+  // haven't parsed enough of the entry to tell yet.
+  virtual void Incomplete(uint64 offset, CallFrameInfo::EntryKind kind);
+
+  // The .eh_frame data has a four-byte zero at OFFSET where the next
+  // entry's length would be; this is a terminator. However, the buffer
+  // length as given to the CallFrameInfo constructor says there should be
+  // more data.
+  virtual void EarlyEHTerminator(uint64 offset);
+
+  // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the
+  // section is not that large.
+  virtual void CIEPointerOutOfRange(uint64 offset, uint64 cie_offset);
+
+  // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the entry
+  // there is not a CIE.
+  virtual void BadCIEId(uint64 offset, uint64 cie_offset);
+
+  // The FDE at OFFSET refers to a CIE with version number VERSION,
+  // which we don't recognize. We cannot parse DWARF CFI if it uses
+  // a version number we don't recognize.
+  virtual void UnrecognizedVersion(uint64 offset, int version);
+
+  // The FDE at OFFSET refers to a CIE with augmentation AUGMENTATION,
+  // which we don't recognize. We cannot parse DWARF CFI if it uses
+  // augmentations we don't recognize.
+  virtual void UnrecognizedAugmentation(uint64 offset,
+                                        const std::string& augmentation);
+
+  // The FDE at OFFSET contains an invalid or otherwise unusable Dwarf4
+  // specific field (currently, only "address_size" or "segment_size").
+  // Parsing DWARF CFI with unexpected values here seems dubious at best,
+  // so we stop.  WHAT gives a little more information about what is wrong.
+  virtual void InvalidDwarf4Artefact(uint64 offset, const char* what);
+
+  // The pointer encoding ENCODING, specified by the CIE at OFFSET, is not
+  // a valid encoding.
+  virtual void InvalidPointerEncoding(uint64 offset, uint8 encoding);
+
+  // The pointer encoding ENCODING, specified by the CIE at OFFSET, depends
+  // on a base address which has not been supplied.
+  virtual void UnusablePointerEncoding(uint64 offset, uint8 encoding);
+
+  // The CIE at OFFSET contains a DW_CFA_restore instruction at
+  // INSN_OFFSET, which may not appear in a CIE.
+  virtual void RestoreInCIE(uint64 offset, uint64 insn_offset);
+
+  // The entry at OFFSET, of kind KIND, has an unrecognized
+  // instruction at INSN_OFFSET.
+  virtual void BadInstruction(uint64 offset, CallFrameInfo::EntryKind kind,
+                              uint64 insn_offset);
+
+  // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
+  // KIND, establishes a rule that cites the CFA, but we have not
+  // established a CFA rule yet.
+  virtual void NoCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
+                         uint64 insn_offset);
+
+  // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
+  // KIND, is a DW_CFA_restore_state instruction, but the stack of
+  // saved states is empty.
+  virtual void EmptyStateStack(uint64 offset, CallFrameInfo::EntryKind kind,
+                               uint64 insn_offset);
+
+  // The DW_CFA_remember_state instruction at INSN_OFFSET in the entry
+  // at OFFSET, of kind KIND, would restore a state that has no CFA
+  // rule, whereas the current state does have a CFA rule. This is
+  // bogus input, which the CallFrameInfo::Handler interface doesn't
+  // (and shouldn't) have any way to report.
+  virtual void ClearingCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
+                               uint64 insn_offset);
+
+ private:
+  // A logging sink function, as supplied by LUL's user.
+  void (*log_)(const char*);
+
+ protected:
+  // The name of the file whose CFI we're reading.
+  std::string filename_;
+
+  // The name of the CFI section in that file.
+  std::string section_;
+};
+
+using lul::CallFrameInfo;
+using lul::Summariser;
+
+// A class that accepts parsed call frame information from the DWARF
+// CFI parser and populates a google_breakpad::Module object with the
+// contents.
+class DwarfCFIToModule : public CallFrameInfo::Handler {
+ public:
+  // DwarfCFIToModule uses an instance of this class to report errors
+  // detected while converting DWARF CFI to Breakpad STACK CFI records.
+  class Reporter {
+   public:
+    // Create a reporter that writes messages to the message sink
+    // |aLog|. FILE is the name of the file we're processing, and
+    // SECTION is the name of the section within that file that we're
+    // looking at (.debug_frame, .eh_frame, etc.).
+    Reporter(void (*aLog)(const char*), const std::string& file,
+             const std::string& section)
+        : log_(aLog), file_(file), section_(section) {}
+    virtual ~Reporter() {}
+
+    // The DWARF CFI entry at OFFSET says that REG is undefined, but the
+    // Breakpad symbol file format cannot express this.
+    virtual void UndefinedNotSupported(size_t offset, const UniqueString* reg);
+
+    // The DWARF CFI entry at OFFSET says that REG uses a DWARF
+    // expression to find its value, but parseDwarfExpr could not
+    // convert it to a sequence of PfxInstrs.
+    virtual void ExpressionCouldNotBeSummarised(size_t offset,
+                                                const UniqueString* reg);
+
+   private:
+    // A logging sink function, as supplied by LUL's user.
+    void (*log_)(const char*);
+
+   protected:
+    std::string file_, section_;
+  };
+
+  // Register name tables. If TABLE is a vector returned by one of these
+  // functions, then TABLE[R] is the name of the register numbered R in
+  // DWARF call frame information.
+  class RegisterNames {
+   public:
+    // Intel's "x86" or IA-32.
+    static unsigned int I386();
+
+    // AMD x86_64, AMD64, Intel EM64T, or Intel 64
+    static unsigned int X86_64();
+
+    // ARM.
+    static unsigned int ARM();
+
+    // AARCH64.
+    static unsigned int ARM64();
+
+    // MIPS.
+    static unsigned int MIPS();
+  };
+
+  // Create a handler for the dwarf2reader::CallFrameInfo parser that
+  // records the stack unwinding information it receives in SUMM.
+  //
+  // Use REGISTER_NAMES[I] as the name of register number I; *this
+  // keeps a reference to the vector, so the vector should remain
+  // alive for as long as the DwarfCFIToModule does.
+  //
+  // Use REPORTER for reporting problems encountered in the conversion
+  // process.
+  DwarfCFIToModule(const unsigned int num_dw_regs, Reporter* reporter,
+                   ByteReader* reader,
+                   /*MOD*/ UniqueStringUniverse* usu,
+                   /*OUT*/ Summariser* summ)
+      : summ_(summ),
+        usu_(usu),
+        num_dw_regs_(num_dw_regs),
+        reporter_(reporter),
+        reader_(reader),
+        return_address_(-1) {}
+  virtual ~DwarfCFIToModule() {}
+
+  virtual bool Entry(size_t offset, uint64 address, uint64 length,
+                     uint8 version, const std::string& augmentation,
+                     unsigned return_address) override;
+  virtual bool UndefinedRule(uint64 address, int reg) override;
+  virtual bool SameValueRule(uint64 address, int reg) override;
+  virtual bool OffsetRule(uint64 address, int reg, int base_register,
+                          long offset) override;
+  virtual bool ValOffsetRule(uint64 address, int reg, int base_register,
+                             long offset) override;
+  virtual bool RegisterRule(uint64 address, int reg,
+                            int base_register) override;
+  virtual bool ExpressionRule(uint64 address, int reg,
+                              const std::string& expression) override;
+  virtual bool ValExpressionRule(uint64 address, int reg,
+                                 const std::string& expression) override;
+  virtual bool End() override;
+
+ private:
+  // Return the name to use for register I.
+  const UniqueString* RegisterName(int i);
+
+  // The Summariser to which we should give entries
+  Summariser* summ_;
+
+  // Universe for creating UniqueStrings in, should that be necessary.
+  UniqueStringUniverse* usu_;
+
+  // The number of Dwarf-defined register names for this architecture.
+  const unsigned int num_dw_regs_;
+
+  // The reporter to use to report problems.
+  Reporter* reporter_;
+
+  // The ByteReader to use for parsing Dwarf expressions.
+  ByteReader* reader_;
+
+  // The section offset of the current frame description entry, for
+  // use in error messages.
+  size_t entry_offset_;
+
+  // The return address column for that entry.
+  unsigned return_address_;
+};
+
+// Convert the Dwarf expression in |expr| into PfxInstrs stored in the
+// SecMap referred to by |summ|, and return the index of the starting
+// PfxInstr added, which must be >= 0.  In case of failure return -1.
+int32_t parseDwarfExpr(Summariser* summ, const ByteReader* reader,
+                       std::string expr, bool debug, bool pushCfaAtStart,
+                       bool derefAtEnd);
+
+}  // namespace lul
+
+#endif  // LulDwarfExt_h
diff --git a/mozglue/baseprofiler/lul/LulDwarfInt.h b/mozglue/baseprofiler/lul/LulDwarfInt.h
new file mode 100644
index 0000000000..b72c6e08e3
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulDwarfInt.h
@@ -0,0 +1,193 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2008, 2010 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// CFI reader author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// This file is derived from the following file in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/dwarf/dwarf2enums.h
+
+#ifndef LulDwarfInt_h
+#define LulDwarfInt_h
+
+#include "LulCommonExt.h"
+#include "LulDwarfExt.h"
+
+namespace lul {
+
+// These enums do not follow the google3 style only because they are
+// known universally (specs, other implementations) by the names in
+// exactly this capitalization.
+// Tag names and codes.
+
+// Call Frame Info instructions.
+enum DwarfCFI {
+  DW_CFA_advance_loc = 0x40,
+  DW_CFA_offset = 0x80,
+  DW_CFA_restore = 0xc0,
+  DW_CFA_nop = 0x00,
+  DW_CFA_set_loc = 0x01,
+  DW_CFA_advance_loc1 = 0x02,
+  DW_CFA_advance_loc2 = 0x03,
+  DW_CFA_advance_loc4 = 0x04,
+  DW_CFA_offset_extended = 0x05,
+  DW_CFA_restore_extended = 0x06,
+  DW_CFA_undefined = 0x07,
+  DW_CFA_same_value = 0x08,
+  DW_CFA_register = 0x09,
+  DW_CFA_remember_state = 0x0a,
+  DW_CFA_restore_state = 0x0b,
+  DW_CFA_def_cfa = 0x0c,
+  DW_CFA_def_cfa_register = 0x0d,
+  DW_CFA_def_cfa_offset = 0x0e,
+  DW_CFA_def_cfa_expression = 0x0f,
+  DW_CFA_expression = 0x10,
+  DW_CFA_offset_extended_sf = 0x11,
+  DW_CFA_def_cfa_sf = 0x12,
+  DW_CFA_def_cfa_offset_sf = 0x13,
+  DW_CFA_val_offset = 0x14,
+  DW_CFA_val_offset_sf = 0x15,
+  DW_CFA_val_expression = 0x16,
+
+  // Opcodes in this range are reserved for user extensions.
+  DW_CFA_lo_user = 0x1c,
+  DW_CFA_hi_user = 0x3f,
+
+  // SGI/MIPS specific.
+  DW_CFA_MIPS_advance_loc8 = 0x1d,
+
+  // GNU extensions.
+  DW_CFA_GNU_window_save = 0x2d,
+  DW_CFA_GNU_args_size = 0x2e,
+  DW_CFA_GNU_negative_offset_extended = 0x2f
+};
+
+// Exception handling 'z' augmentation letters.
+enum DwarfZAugmentationCodes {
+  // If the CFI augmentation string begins with 'z', then the CIE and FDE
+  // have an augmentation data area just before the instructions, whose
+  // contents are determined by the subsequent augmentation letters.
+  DW_Z_augmentation_start = 'z',
+
+  // If this letter is present in a 'z' augmentation string, the CIE
+  // augmentation data includes a pointer encoding, and the FDE
+  // augmentation data includes a language-specific data area pointer,
+  // represented using that encoding.
+  DW_Z_has_LSDA = 'L',
+
+  // If this letter is present in a 'z' augmentation string, the CIE
+  // augmentation data includes a pointer encoding, followed by a pointer
+  // to a personality routine, represented using that encoding.
+  DW_Z_has_personality_routine = 'P',
+
+  // If this letter is present in a 'z' augmentation string, the CIE
+  // augmentation data includes a pointer encoding describing how the FDE's
+  // initial location, address range, and DW_CFA_set_loc operands are
+  // encoded.
+  DW_Z_has_FDE_address_encoding = 'R',
+
+  // If this letter is present in a 'z' augmentation string, then code
+  // addresses covered by FDEs that cite this CIE are signal delivery
+  // trampolines. Return addresses of frames in trampolines should not be
+  // adjusted as described in section 6.4.4 of the DWARF 3 spec.
+  DW_Z_is_signal_trampoline = 'S'
+};
+
+// Expression opcodes
+enum DwarfExpressionOpcodes {
+  DW_OP_addr = 0x03,
+  DW_OP_deref = 0x06,
+  DW_OP_const1s = 0x09,
+  DW_OP_const2u = 0x0a,
+  DW_OP_const2s = 0x0b,
+  DW_OP_const4u = 0x0c,
+  DW_OP_const4s = 0x0d,
+  DW_OP_const8u = 0x0e,
+  DW_OP_const8s = 0x0f,
+  DW_OP_constu = 0x10,
+  DW_OP_consts = 0x11,
+  DW_OP_dup = 0x12,
+  DW_OP_drop = 0x13,
+  DW_OP_over = 0x14,
+  DW_OP_pick = 0x15,
+  DW_OP_swap = 0x16,
+  DW_OP_rot = 0x17,
+  DW_OP_xderef = 0x18,
+  DW_OP_abs = 0x19,
+  DW_OP_and = 0x1a,
+  DW_OP_div = 0x1b,
+  DW_OP_minus = 0x1c,
+  DW_OP_mod = 0x1d,
+  DW_OP_mul = 0x1e,
+  DW_OP_neg = 0x1f,
+  DW_OP_not = 0x20,
+  DW_OP_or = 0x21,
+  DW_OP_plus = 0x22,
+  DW_OP_plus_uconst = 0x23,
+  DW_OP_shl = 0x24,
+  DW_OP_shr = 0x25,
+  DW_OP_shra = 0x26,
+  DW_OP_xor = 0x27,
+  DW_OP_skip = 0x2f,
+  DW_OP_bra = 0x28,
+  DW_OP_eq = 0x29,
+  DW_OP_ge = 0x2a,
+  DW_OP_gt = 0x2b,
+  DW_OP_le = 0x2c,
+  DW_OP_lt = 0x2d,
+  DW_OP_ne = 0x2e,
+  DW_OP_lit0 = 0x30,
+  DW_OP_lit31 = 0x4f,
+  DW_OP_reg0 = 0x50,
+  DW_OP_reg31 = 0x6f,
+  DW_OP_breg0 = 0x70,
+  DW_OP_breg31 = 0x8f,
+  DW_OP_regx = 0x90,
+  DW_OP_fbreg = 0x91,
+  DW_OP_bregx = 0x92,
+  DW_OP_piece = 0x93,
+  DW_OP_deref_size = 0x94,
+  DW_OP_xderef_size = 0x95,
+  DW_OP_nop = 0x96,
+  DW_OP_push_object_address = 0x97,
+  DW_OP_call2 = 0x98,
+  DW_OP_call4 = 0x99,
+  DW_OP_call_ref = 0x9a,
+  DW_OP_form_tls_address = 0x9b,
+  DW_OP_call_frame_cfa = 0x9c,
+  DW_OP_bit_piece = 0x9d,
+  DW_OP_lo_user = 0xe0,
+  DW_OP_hi_user = 0xff
+};
+
+}  // namespace lul
+
+#endif  // LulDwarfInt_h
diff --git a/mozglue/baseprofiler/lul/LulDwarfSummariser.cpp b/mozglue/baseprofiler/lul/LulDwarfSummariser.cpp
new file mode 100644
index 0000000000..ff0f212f6c
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulDwarfSummariser.cpp
@@ -0,0 +1,553 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LulDwarfSummariser.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Sprintf.h"
+
+#include "LulDwarfExt.h"
+
+// Set this to 1 for verbose logging
+#define DEBUG_SUMMARISER 0
+
+namespace lul {
+
+// Do |s64|'s lowest 32 bits sign extend back to |s64| itself?
+static inline bool fitsIn32Bits(int64 s64) {
+  return s64 == ((s64 & 0xffffffff) ^ 0x80000000) - 0x80000000;
+}
+
+// Check a LExpr prefix expression, starting at pfxInstrs[start] up to
+// the next PX_End instruction, to ensure that:
+// * It only mentions registers that are tracked on this target
+// * The start point is sane
+// If the expression is ok, return NULL.  Else return a pointer
+// a const char* holding a bit of text describing the problem.
+static const char* checkPfxExpr(const vector<PfxInstr>* pfxInstrs,
+                                int64_t start) {
+  size_t nInstrs = pfxInstrs->size();
+  if (start < 0 || start >= (ssize_t)nInstrs) {
+    return "bogus start point";
+  }
+  size_t i;
+  for (i = start; i < nInstrs; i++) {
+    PfxInstr pxi = (*pfxInstrs)[i];
+    if (pxi.mOpcode == PX_End) break;
+    if (pxi.mOpcode == PX_DwReg &&
+        !registerIsTracked((DW_REG_NUMBER)pxi.mOperand)) {
+      return "uses untracked reg";
+    }
+  }
+  return nullptr;  // success
+}
+
+Summariser::Summariser(SecMap* aSecMap, uintptr_t aTextBias,
+                       void (*aLog)(const char*))
+    : mSecMap(aSecMap), mTextBias(aTextBias), mLog(aLog) {
+  mCurrAddr = 0;
+  mMax1Addr = 0;  // Gives an empty range.
+
+  // Initialise the running RuleSet to "haven't got a clue" status.
+  new (&mCurrRules) RuleSet();
+}
+
+void Summariser::Entry(uintptr_t aAddress, uintptr_t aLength) {
+  aAddress += mTextBias;
+  if (DEBUG_SUMMARISER) {
+    char buf[100];
+    SprintfLiteral(buf, "LUL Entry(%llx, %llu)\n",
+                   (unsigned long long int)aAddress,
+                   (unsigned long long int)aLength);
+    mLog(buf);
+  }
+  // This throws away any previous summary, that is, assumes
+  // that the previous summary, if any, has been properly finished
+  // by a call to End().
+  mCurrAddr = aAddress;
+  mMax1Addr = aAddress + aLength;
+  new (&mCurrRules) RuleSet();
+}
+
+void Summariser::Rule(uintptr_t aAddress, int aNewReg, LExprHow how,
+                      int16_t oldReg, int64_t offset) {
+  aAddress += mTextBias;
+  if (DEBUG_SUMMARISER) {
+    char buf[100];
+    if (how == NODEREF || how == DEREF) {
+      bool deref = how == DEREF;
+      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = %sr%d + %lld%s\n",
+                     (unsigned long long int)aAddress, aNewReg,
+                     deref ? "*(" : "", (int)oldReg, (long long int)offset,
+                     deref ? ")" : "");
+    } else if (how == PFXEXPR) {
+      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = pfx-expr-at %lld\n",
+                     (unsigned long long int)aAddress, aNewReg,
+                     (long long int)offset);
+    } else {
+      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = (invalid LExpr!)\n",
+                     (unsigned long long int)aAddress, aNewReg);
+    }
+    mLog(buf);
+  }
+
+  if (mCurrAddr < aAddress) {
+    // Flush the existing summary first.
+    mCurrRules.mAddr = mCurrAddr;
+    mCurrRules.mLen = aAddress - mCurrAddr;
+    mSecMap->AddRuleSet(&mCurrRules);
+    if (DEBUG_SUMMARISER) {
+      mLog("LUL  ");
+      mCurrRules.Print(mLog);
+      mLog("\n");
+    }
+    mCurrAddr = aAddress;
+  }
+
+  // If for some reason summarisation fails, either or both of these
+  // become non-null and point at constant text describing the
+  // problem.  Using two rather than just one avoids complications of
+  // having to concatenate two strings to produce a complete error message.
+  const char* reason1 = nullptr;
+  const char* reason2 = nullptr;
+
+  // |offset| needs to be a 32 bit value that sign extends to 64 bits
+  // on a 64 bit target.  We will need to incorporate |offset| into
+  // any LExpr made here.  So we may as well check it right now.
+  if (!fitsIn32Bits(offset)) {
+    reason1 = "offset not in signed 32-bit range";
+    goto cant_summarise;
+  }
+
+  // FIXME: factor out common parts of the arch-dependent summarisers.
+
+#if defined(GP_ARCH_arm)
+
+  // ----------------- arm ----------------- //
+
+  // Now, can we add the rule to our summary?  This depends on whether
+  // the registers and the overall expression are representable.  This
+  // is the heart of the summarisation process.
+  switch (aNewReg) {
+    case DW_REG_CFA:
+      // This is a rule that defines the CFA.  The only forms we
+      // choose to represent are: r7/11/12/13 + offset.  The offset
+      // must fit into 32 bits since 'uintptr_t' is 32 bit on ARM,
+      // hence there is no need to check it for overflow.
+      if (how != NODEREF) {
+        reason1 = "rule for DW_REG_CFA: invalid |how|";
+        goto cant_summarise;
+      }
+      switch (oldReg) {
+        case DW_REG_ARM_R7:
+        case DW_REG_ARM_R11:
+        case DW_REG_ARM_R12:
+        case DW_REG_ARM_R13:
+          break;
+        default:
+          reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
+          goto cant_summarise;
+      }
+      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
+      break;
+
+    case DW_REG_ARM_R7:
+    case DW_REG_ARM_R11:
+    case DW_REG_ARM_R12:
+    case DW_REG_ARM_R13:
+    case DW_REG_ARM_R14:
+    case DW_REG_ARM_R15: {
+      // This is a new rule for R7, R11, R12, R13 (SP), R14 (LR) or
+      // R15 (the return address).
+      switch (how) {
+        case NODEREF:
+        case DEREF:
+          // Check the old register is one we're tracking.
+          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
+              oldReg != DW_REG_CFA) {
+            reason1 = "rule for R7/11/12/13/14/15: uses untracked reg";
+            goto cant_summarise;
+          }
+          break;
+        case PFXEXPR: {
+          // Check that the prefix expression only mentions tracked registers.
+          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
+          reason2 = checkPfxExpr(pfxInstrs, offset);
+          if (reason2) {
+            reason1 = "rule for R7/11/12/13/14/15: ";
+            goto cant_summarise;
+          }
+          break;
+        }
+        default:
+          goto cant_summarise;
+      }
+      LExpr expr = LExpr(how, oldReg, offset);
+      switch (aNewReg) {
+        case DW_REG_ARM_R7:
+          mCurrRules.mR7expr = expr;
+          break;
+        case DW_REG_ARM_R11:
+          mCurrRules.mR11expr = expr;
+          break;
+        case DW_REG_ARM_R12:
+          mCurrRules.mR12expr = expr;
+          break;
+        case DW_REG_ARM_R13:
+          mCurrRules.mR13expr = expr;
+          break;
+        case DW_REG_ARM_R14:
+          mCurrRules.mR14expr = expr;
+          break;
+        case DW_REG_ARM_R15:
+          mCurrRules.mR15expr = expr;
+          break;
+        default:
+          MOZ_ASSERT(0);
+      }
+      break;
+    }
+
+    default:
+      // Leave |reason1| and |reason2| unset here.  This program point
+      // is reached so often that it causes a flood of "Can't
+      // summarise" messages.  In any case, we don't really care about
+      // the fact that this summary would produce a new value for a
+      // register that we're not tracking.  We do on the other hand
+      // care if the summary's expression *uses* a register that we're
+      // not tracking.  But in that case one of the above failures
+      // should tell us which.
+      goto cant_summarise;
+  }
+
+  // Mark callee-saved registers (r4 .. r11) as unchanged, if there is
+  // no other information about them.  FIXME: do this just once, at
+  // the point where the ruleset is committed.
+  if (mCurrRules.mR7expr.mHow == UNKNOWN) {
+    mCurrRules.mR7expr = LExpr(NODEREF, DW_REG_ARM_R7, 0);
+  }
+  if (mCurrRules.mR11expr.mHow == UNKNOWN) {
+    mCurrRules.mR11expr = LExpr(NODEREF, DW_REG_ARM_R11, 0);
+  }
+  if (mCurrRules.mR12expr.mHow == UNKNOWN) {
+    mCurrRules.mR12expr = LExpr(NODEREF, DW_REG_ARM_R12, 0);
+  }
+
+  // The old r13 (SP) value before the call is always the same as the
+  // CFA.
+  mCurrRules.mR13expr = LExpr(NODEREF, DW_REG_CFA, 0);
+
+  // If there's no information about R15 (the return address), say
+  // it's a copy of R14 (the link register).
+  if (mCurrRules.mR15expr.mHow == UNKNOWN) {
+    mCurrRules.mR15expr = LExpr(NODEREF, DW_REG_ARM_R14, 0);
+  }
+
+#elif defined(GP_ARCH_arm64)
+
+  // ----------------- arm64 ----------------- //
+
+  switch (aNewReg) {
+    case DW_REG_CFA:
+      if (how != NODEREF) {
+        reason1 = "rule for DW_REG_CFA: invalid |how|";
+        goto cant_summarise;
+      }
+      switch (oldReg) {
+        case DW_REG_AARCH64_X29:
+        case DW_REG_AARCH64_SP:
+          break;
+        default:
+          reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
+          goto cant_summarise;
+      }
+      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
+      break;
+
+    case DW_REG_AARCH64_X29:
+    case DW_REG_AARCH64_X30:
+    case DW_REG_AARCH64_SP: {
+      switch (how) {
+        case NODEREF:
+        case DEREF:
+          // Check the old register is one we're tracking.
+          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
+              oldReg != DW_REG_CFA) {
+            reason1 = "rule for X29/X30/SP: uses untracked reg";
+            goto cant_summarise;
+          }
+          break;
+        case PFXEXPR: {
+          // Check that the prefix expression only mentions tracked registers.
+          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
+          reason2 = checkPfxExpr(pfxInstrs, offset);
+          if (reason2) {
+            reason1 = "rule for X29/X30/SP: ";
+            goto cant_summarise;
+          }
+          break;
+        }
+        default:
+          goto cant_summarise;
+      }
+      LExpr expr = LExpr(how, oldReg, offset);
+      switch (aNewReg) {
+        case DW_REG_AARCH64_X29:
+          mCurrRules.mX29expr = expr;
+          break;
+        case DW_REG_AARCH64_X30:
+          mCurrRules.mX30expr = expr;
+          break;
+        case DW_REG_AARCH64_SP:
+          mCurrRules.mSPexpr = expr;
+          break;
+        default:
+          MOZ_ASSERT(0);
+      }
+      break;
+    }
+    default:
+      // Leave |reason1| and |reason2| unset here, for the reasons explained
+      // in the analogous point
+      goto cant_summarise;
+  }
+
+  if (mCurrRules.mX29expr.mHow == UNKNOWN) {
+    mCurrRules.mX29expr = LExpr(NODEREF, DW_REG_AARCH64_X29, 0);
+  }
+  if (mCurrRules.mX30expr.mHow == UNKNOWN) {
+    mCurrRules.mX30expr = LExpr(NODEREF, DW_REG_AARCH64_X30, 0);
+  }
+  // On aarch64, it seems the old SP value before the call is always the
+  // same as the CFA.  Therefore, in the absence of any other way to
+  // recover the SP, specify that the CFA should be copied.
+  if (mCurrRules.mSPexpr.mHow == UNKNOWN) {
+    mCurrRules.mSPexpr = LExpr(NODEREF, DW_REG_CFA, 0);
+  }
+#elif defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+
+  // ---------------- x64/x86 ---------------- //
+
+  // Now, can we add the rule to our summary?  This depends on whether
+  // the registers and the overall expression are representable.  This
+  // is the heart of the summarisation process.
+  switch (aNewReg) {
+    case DW_REG_CFA: {
+      // This is a rule that defines the CFA.  The only forms we choose to
+      // represent are: = SP+offset, = FP+offset, or =prefix-expr.
+      switch (how) {
+        case NODEREF:
+          if (oldReg != DW_REG_INTEL_XSP && oldReg != DW_REG_INTEL_XBP) {
+            reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
+            goto cant_summarise;
+          }
+          break;
+        case DEREF:
+          reason1 = "rule for DW_REG_CFA: invalid |how|";
+          goto cant_summarise;
+        case PFXEXPR: {
+          // Check that the prefix expression only mentions tracked registers.
+          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
+          reason2 = checkPfxExpr(pfxInstrs, offset);
+          if (reason2) {
+            reason1 = "rule for CFA: ";
+            goto cant_summarise;
+          }
+          break;
+        }
+        default:
+          goto cant_summarise;
+      }
+      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
+      break;
+    }
+
+    case DW_REG_INTEL_XSP:
+    case DW_REG_INTEL_XBP:
+    case DW_REG_INTEL_XIP: {
+      // This is a new rule for XSP, XBP or XIP (the return address).
+      switch (how) {
+        case NODEREF:
+        case DEREF:
+          // Check the old register is one we're tracking.
+          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
+              oldReg != DW_REG_CFA) {
+            reason1 = "rule for XSP/XBP/XIP: uses untracked reg";
+            goto cant_summarise;
+          }
+          break;
+        case PFXEXPR: {
+          // Check that the prefix expression only mentions tracked registers.
+          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
+          reason2 = checkPfxExpr(pfxInstrs, offset);
+          if (reason2) {
+            reason1 = "rule for XSP/XBP/XIP: ";
+            goto cant_summarise;
+          }
+          break;
+        }
+        default:
+          goto cant_summarise;
+      }
+      LExpr expr = LExpr(how, oldReg, offset);
+      switch (aNewReg) {
+        case DW_REG_INTEL_XBP:
+          mCurrRules.mXbpExpr = expr;
+          break;
+        case DW_REG_INTEL_XSP:
+          mCurrRules.mXspExpr = expr;
+          break;
+        case DW_REG_INTEL_XIP:
+          mCurrRules.mXipExpr = expr;
+          break;
+        default:
+          MOZ_CRASH("impossible value for aNewReg");
+      }
+      break;
+    }
+
+    default:
+      // Leave |reason1| and |reason2| unset here, for the reasons
+      // explained in the analogous point in the ARM case just above.
+      goto cant_summarise;
+  }
+
+  // On Intel, it seems the old SP value before the call is always the
+  // same as the CFA.  Therefore, in the absence of any other way to
+  // recover the SP, specify that the CFA should be copied.
+  if (mCurrRules.mXspExpr.mHow == UNKNOWN) {
+    mCurrRules.mXspExpr = LExpr(NODEREF, DW_REG_CFA, 0);
+  }
+
+  // Also, gcc says "Undef" for BP when it is unchanged.
+  if (mCurrRules.mXbpExpr.mHow == UNKNOWN) {
+    mCurrRules.mXbpExpr = LExpr(NODEREF, DW_REG_INTEL_XBP, 0);
+  }
+
+#elif defined(GP_ARCH_mips64)
+  // ---------------- mips ---------------- //
+  //
+  // Now, can we add the rule to our summary?  This depends on whether
+  // the registers and the overall expression are representable.  This
+  // is the heart of the summarisation process.
+  switch (aNewReg) {
+    case DW_REG_CFA:
+      // This is a rule that defines the CFA.  The only forms we can
+      // represent are: = SP+offset or = FP+offset.
+      if (how != NODEREF) {
+        reason1 = "rule for DW_REG_CFA: invalid |how|";
+        goto cant_summarise;
+      }
+      if (oldReg != DW_REG_MIPS_SP && oldReg != DW_REG_MIPS_FP) {
+        reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
+        goto cant_summarise;
+      }
+      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
+      break;
+
+    case DW_REG_MIPS_SP:
+    case DW_REG_MIPS_FP:
+    case DW_REG_MIPS_PC: {
+      // This is a new rule for SP, FP or PC (the return address).
+      switch (how) {
+        case NODEREF:
+        case DEREF:
+          // Check the old register is one we're tracking.
+          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
+              oldReg != DW_REG_CFA) {
+            reason1 = "rule for SP/FP/PC: uses untracked reg";
+            goto cant_summarise;
+          }
+          break;
+        case PFXEXPR: {
+          // Check that the prefix expression only mentions tracked registers.
+          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
+          reason2 = checkPfxExpr(pfxInstrs, offset);
+          if (reason2) {
+            reason1 = "rule for SP/FP/PC: ";
+            goto cant_summarise;
+          }
+          break;
+        }
+        default:
+          goto cant_summarise;
+      }
+      LExpr expr = LExpr(how, oldReg, offset);
+      switch (aNewReg) {
+        case DW_REG_MIPS_FP:
+          mCurrRules.mFPexpr = expr;
+          break;
+        case DW_REG_MIPS_SP:
+          mCurrRules.mSPexpr = expr;
+          break;
+        case DW_REG_MIPS_PC:
+          mCurrRules.mPCexpr = expr;
+          break;
+        default:
+          MOZ_CRASH("impossible value for aNewReg");
+      }
+      break;
+    }
+    default:
+      // Leave |reason1| and |reason2| unset here, for the reasons
+      // explained in the analogous point in the ARM case just above.
+      goto cant_summarise;
+  }
+
+  // On MIPS, it seems the old SP value before the call is always the
+  // same as the CFA.  Therefore, in the absence of any other way to
+  // recover the SP, specify that the CFA should be copied.
+  if (mCurrRules.mSPexpr.mHow == UNKNOWN) {
+    mCurrRules.mSPexpr = LExpr(NODEREF, DW_REG_CFA, 0);
+  }
+
+  // Also, gcc says "Undef" for FP when it is unchanged.
+  if (mCurrRules.mFPexpr.mHow == UNKNOWN) {
+    mCurrRules.mFPexpr = LExpr(NODEREF, DW_REG_MIPS_FP, 0);
+  }
+
+#else
+
+#  error "Unsupported arch"
+#endif
+
+  return;
+
+cant_summarise:
+  if (reason1 || reason2) {
+    char buf[200];
+    SprintfLiteral(buf,
+                   "LUL  can't summarise: "
+                   "SVMA=0x%llx: %s%s, expr=LExpr(%s,%u,%lld)\n",
+                   (unsigned long long int)(aAddress - mTextBias),
+                   reason1 ? reason1 : "", reason2 ? reason2 : "",
+                   NameOf_LExprHow(how), (unsigned int)oldReg,
+                   (long long int)offset);
+    mLog(buf);
+  }
+}
+
+uint32_t Summariser::AddPfxInstr(PfxInstr pfxi) {
+  return mSecMap->AddPfxInstr(pfxi);
+}
+
+void Summariser::End() {
+  if (DEBUG_SUMMARISER) {
+    mLog("LUL End\n");
+  }
+  if (mCurrAddr < mMax1Addr) {
+    mCurrRules.mAddr = mCurrAddr;
+    mCurrRules.mLen = mMax1Addr - mCurrAddr;
+    mSecMap->AddRuleSet(&mCurrRules);
+    if (DEBUG_SUMMARISER) {
+      mLog("LUL  ");
+      mCurrRules.Print(mLog);
+      mLog("\n");
+    }
+  }
+}
+
+}  // namespace lul
diff --git a/mozglue/baseprofiler/lul/LulDwarfSummariser.h b/mozglue/baseprofiler/lul/LulDwarfSummariser.h
new file mode 100644
index 0000000000..30f1ba23c1
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulDwarfSummariser.h
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LulDwarfSummariser_h
+#define LulDwarfSummariser_h
+
+#include "LulMainInt.h"
+
+namespace lul {
+
+class Summariser {
+ public:
+  Summariser(SecMap* aSecMap, uintptr_t aTextBias, void (*aLog)(const char*));
+
+  virtual void Entry(uintptr_t aAddress, uintptr_t aLength);
+  virtual void End();
+
+  // Tell the summariser that the value for |aNewReg| at |aAddress| is
+  // recovered using the LExpr that can be constructed using the
+  // components |how|, |oldReg| and |offset|.  The summariser will
+  // inspect the components and may reject them for various reasons,
+  // but the hope is that it will find them acceptable and record this
+  // rule permanently.
+  virtual void Rule(uintptr_t aAddress, int aNewReg, LExprHow how,
+                    int16_t oldReg, int64_t offset);
+
+  virtual uint32_t AddPfxInstr(PfxInstr pfxi);
+
+  // Send output to the logging sink, for debugging.
+  virtual void Log(const char* str) { mLog(str); }
+
+ private:
+  // The SecMap in which we park the finished summaries (RuleSets) and
+  // also any PfxInstrs derived from Dwarf expressions.
+  SecMap* mSecMap;
+
+  // Running state for the current summary (RuleSet) under construction.
+  RuleSet mCurrRules;
+
+  // The start of the address range to which the RuleSet under
+  // construction applies.
+  uintptr_t mCurrAddr;
+
+  // The highest address, plus one, for which the RuleSet under
+  // construction could possibly apply.  If there are no further
+  // incoming events then mCurrRules will eventually be emitted
+  // as-is, for the range mCurrAddr.. mMax1Addr - 1, if that is
+  // nonempty.
+  uintptr_t mMax1Addr;
+
+  // The bias value (to add to the SVMAs, to get AVMAs) to be used
+  // when adding entries into mSecMap.
+  uintptr_t mTextBias;
+
+  // A logging sink, for debugging.
+  void (*mLog)(const char* aFmt);
+};
+
+}  // namespace lul
+
+#endif  // LulDwarfSummariser_h
diff --git a/mozglue/baseprofiler/lul/LulElf.cpp b/mozglue/baseprofiler/lul/LulElf.cpp
new file mode 100644
index 0000000000..b5d5e772be
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulElf.cpp
@@ -0,0 +1,873 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2006, 2011, 2012 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Restructured in 2009 by: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// (derived from)
+// dump_symbols.cc: implement google_breakpad::WriteSymbolFile:
+// Find all the debugging info in a file and dump it as a Breakpad symbol file.
+//
+// dump_symbols.h: Read debugging information from an ELF file, and write
+// it out as a Breakpad symbol file.
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/linux/dump_symbols.cc
+//   src/common/linux/elfutils.cc
+//   src/common/linux/file_id.cc
+
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+
+#include <cstdlib>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Sprintf.h"
+
+#include "PlatformMacros.h"
+#include "LulCommonExt.h"
+#include "LulDwarfExt.h"
+#include "LulElfInt.h"
+#include "LulMainInt.h"
+
+#if defined(GP_PLAT_arm_android) && !defined(SHT_ARM_EXIDX)
+// bionic and older glibsc don't define it
+#  define SHT_ARM_EXIDX (SHT_LOPROC + 1)
+#endif
+
+// Old Linux header doesn't define EM_AARCH64
+#ifndef EM_AARCH64
+#  define EM_AARCH64 183
+#endif
+
+// This namespace contains helper functions.
+namespace {
+
+using lul::DwarfCFIToModule;
+using lul::FindElfSectionByName;
+using lul::GetOffset;
+using lul::IsValidElf;
+using lul::Module;
+using lul::scoped_ptr;
+using lul::Summariser;
+using lul::UniqueStringUniverse;
+using std::set;
+using std::string;
+using std::vector;
+
+//
+// FDWrapper
+//
+// Wrapper class to make sure opened file is closed.
+//
+class FDWrapper {
+ public:
+  explicit FDWrapper(int fd) : fd_(fd) {}
+  ~FDWrapper() {
+    if (fd_ != -1) close(fd_);
+  }
+  int get() { return fd_; }
+  int release() {
+    int fd = fd_;
+    fd_ = -1;
+    return fd;
+  }
+
+ private:
+  int fd_;
+};
+
+//
+// MmapWrapper
+//
+// Wrapper class to make sure mapped regions are unmapped.
+//
+class MmapWrapper {
+ public:
+  MmapWrapper() : is_set_(false), base_(NULL), size_(0) {}
+  ~MmapWrapper() {
+    if (is_set_ && base_ != NULL) {
+      MOZ_ASSERT(size_ > 0);
+      munmap(base_, size_);
+    }
+  }
+  void set(void* mapped_address, size_t mapped_size) {
+    is_set_ = true;
+    base_ = mapped_address;
+    size_ = mapped_size;
+  }
+  void release() {
+    MOZ_ASSERT(is_set_);
+    is_set_ = false;
+    base_ = NULL;
+    size_ = 0;
+  }
+
+ private:
+  bool is_set_;
+  void* base_;
+  size_t size_;
+};
+
+// Set NUM_DW_REGNAMES to be the number of Dwarf register names
+// appropriate to the machine architecture given in HEADER.  Return
+// true on success, or false if HEADER's machine architecture is not
+// supported.
+template <typename ElfClass>
+bool DwarfCFIRegisterNames(const typename ElfClass::Ehdr* elf_header,
+                           unsigned int* num_dw_regnames) {
+  switch (elf_header->e_machine) {
+    case EM_386:
+      *num_dw_regnames = DwarfCFIToModule::RegisterNames::I386();
+      return true;
+    case EM_ARM:
+      *num_dw_regnames = DwarfCFIToModule::RegisterNames::ARM();
+      return true;
+    case EM_X86_64:
+      *num_dw_regnames = DwarfCFIToModule::RegisterNames::X86_64();
+      return true;
+    case EM_MIPS:
+      *num_dw_regnames = DwarfCFIToModule::RegisterNames::MIPS();
+      return true;
+    case EM_AARCH64:
+      *num_dw_regnames = DwarfCFIToModule::RegisterNames::ARM64();
+      return true;
+    default:
+      MOZ_ASSERT(0);
+      return false;
+  }
+}
+
+template <typename ElfClass>
+bool LoadDwarfCFI(const string& dwarf_filename,
+                  const typename ElfClass::Ehdr* elf_header,
+                  const char* section_name,
+                  const typename ElfClass::Shdr* section, const bool eh_frame,
+                  const typename ElfClass::Shdr* got_section,
+                  const typename ElfClass::Shdr* text_section,
+                  const bool big_endian, SecMap* smap, uintptr_t text_bias,
+                  UniqueStringUniverse* usu, void (*log)(const char*)) {
+  // Find the appropriate set of register names for this file's
+  // architecture.
+  unsigned int num_dw_regs = 0;
+  if (!DwarfCFIRegisterNames<ElfClass>(elf_header, &num_dw_regs)) {
+    fprintf(stderr,
+            "%s: unrecognized ELF machine architecture '%d';"
+            " cannot convert DWARF call frame information\n",
+            dwarf_filename.c_str(), elf_header->e_machine);
+    return false;
+  }
+
+  const lul::Endianness endianness =
+      big_endian ? lul::ENDIANNESS_BIG : lul::ENDIANNESS_LITTLE;
+
+  // Find the call frame information and its size.
+  const char* cfi = GetOffset<ElfClass, char>(elf_header, section->sh_offset);
+  size_t cfi_size = section->sh_size;
+
+  // Plug together the parser, handler, and their entourages.
+
+  // Here's a summariser, which will receive the output of the
+  // parser, create summaries, and add them to |smap|.
+  Summariser summ(smap, text_bias, log);
+
+  lul::ByteReader reader(endianness);
+  reader.SetAddressSize(ElfClass::kAddrSize);
+
+  DwarfCFIToModule::Reporter module_reporter(log, dwarf_filename, section_name);
+  DwarfCFIToModule handler(num_dw_regs, &module_reporter, &reader, usu, &summ);
+
+  // Provide the base addresses for .eh_frame encoded pointers, if
+  // possible.
+  reader.SetCFIDataBase(section->sh_addr, cfi);
+  if (got_section) reader.SetDataBase(got_section->sh_addr);
+  if (text_section) reader.SetTextBase(text_section->sh_addr);
+
+  lul::CallFrameInfo::Reporter dwarf_reporter(log, dwarf_filename,
+                                              section_name);
+  lul::CallFrameInfo parser(cfi, cfi_size, &reader, &handler, &dwarf_reporter,
+                            eh_frame);
+  parser.Start();
+
+  return true;
+}
+
+bool LoadELF(const string& obj_file, MmapWrapper* map_wrapper,
+             void** elf_header) {
+  int obj_fd = open(obj_file.c_str(), O_RDONLY);
+  if (obj_fd < 0) {
+    fprintf(stderr, "Failed to open ELF file '%s': %s\n", obj_file.c_str(),
+            strerror(errno));
+    return false;
+  }
+  FDWrapper obj_fd_wrapper(obj_fd);
+  struct stat st;
+  if (fstat(obj_fd, &st) != 0 && st.st_size <= 0) {
+    fprintf(stderr, "Unable to fstat ELF file '%s': %s\n", obj_file.c_str(),
+            strerror(errno));
+    return false;
+  }
+  // Mapping it read-only is good enough.  In any case, mapping it
+  // read-write confuses Valgrind's debuginfo acquire/discard
+  // heuristics, making it hard to profile the profiler.
+  void* obj_base = mmap(nullptr, st.st_size, PROT_READ, MAP_PRIVATE, obj_fd, 0);
+  if (obj_base == MAP_FAILED) {
+    fprintf(stderr, "Failed to mmap ELF file '%s': %s\n", obj_file.c_str(),
+            strerror(errno));
+    return false;
+  }
+  map_wrapper->set(obj_base, st.st_size);
+  *elf_header = obj_base;
+  if (!IsValidElf(*elf_header)) {
+    fprintf(stderr, "Not a valid ELF file: %s\n", obj_file.c_str());
+    return false;
+  }
+  return true;
+}
+
+// Get the endianness of ELF_HEADER. If it's invalid, return false.
+template <typename ElfClass>
+bool ElfEndianness(const typename ElfClass::Ehdr* elf_header,
+                   bool* big_endian) {
+  if (elf_header->e_ident[EI_DATA] == ELFDATA2LSB) {
+    *big_endian = false;
+    return true;
+  }
+  if (elf_header->e_ident[EI_DATA] == ELFDATA2MSB) {
+    *big_endian = true;
+    return true;
+  }
+
+  fprintf(stderr, "bad data encoding in ELF header: %d\n",
+          elf_header->e_ident[EI_DATA]);
+  return false;
+}
+
+//
+// LoadSymbolsInfo
+//
+// Holds the state between the two calls to LoadSymbols() in case it's necessary
+// to follow the .gnu_debuglink section and load debug information from a
+// different file.
+//
+template <typename ElfClass>
+class LoadSymbolsInfo {
+ public:
+  typedef typename ElfClass::Addr Addr;
+
+  explicit LoadSymbolsInfo(const vector<string>& dbg_dirs)
+      : debug_dirs_(dbg_dirs), has_loading_addr_(false) {}
+
+  // Keeps track of which sections have been loaded so sections don't
+  // accidentally get loaded twice from two different files.
+  void LoadedSection(const string& section) {
+    if (loaded_sections_.count(section) == 0) {
+      loaded_sections_.insert(section);
+    } else {
+      fprintf(stderr, "Section %s has already been loaded.\n", section.c_str());
+    }
+  }
+
+  string debuglink_file() const { return debuglink_file_; }
+
+ private:
+  const vector<string>& debug_dirs_;  // Directories in which to
+                                      // search for the debug ELF file.
+
+  string debuglink_file_;  // Full path to the debug ELF file.
+
+  bool has_loading_addr_;  // Indicate if LOADING_ADDR_ is valid.
+
+  set<string> loaded_sections_;  // Tracks the Loaded ELF sections
+                                 // between calls to LoadSymbols().
+};
+
+// Find the preferred loading address of the binary.
+template <typename ElfClass>
+typename ElfClass::Addr GetLoadingAddress(
+    const typename ElfClass::Phdr* program_headers, int nheader) {
+  typedef typename ElfClass::Phdr Phdr;
+
+  // For non-PIC executables (e_type == ET_EXEC), the load address is
+  // the start address of the first PT_LOAD segment.  (ELF requires
+  // the segments to be sorted by load address.)  For PIC executables
+  // and dynamic libraries (e_type == ET_DYN), this address will
+  // normally be zero.
+  for (int i = 0; i < nheader; ++i) {
+    const Phdr& header = program_headers[i];
+    if (header.p_type == PT_LOAD) return header.p_vaddr;
+  }
+  return 0;
+}
+
+template <typename ElfClass>
+bool LoadSymbols(const string& obj_file, const bool big_endian,
+                 const typename ElfClass::Ehdr* elf_header,
+                 const bool read_gnu_debug_link,
+                 LoadSymbolsInfo<ElfClass>* info, SecMap* smap, void* rx_avma,
+                 size_t rx_size, UniqueStringUniverse* usu,
+                 void (*log)(const char*)) {
+  typedef typename ElfClass::Phdr Phdr;
+  typedef typename ElfClass::Shdr Shdr;
+
+  char buf[500];
+  SprintfLiteral(buf, "LoadSymbols: BEGIN   %s\n", obj_file.c_str());
+  buf[sizeof(buf) - 1] = 0;
+  log(buf);
+
+  // This is how the text bias is calculated.
+  // BEGIN CALCULATE BIAS
+  uintptr_t loading_addr = GetLoadingAddress<ElfClass>(
+      GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff),
+      elf_header->e_phnum);
+  uintptr_t text_bias = ((uintptr_t)rx_avma) - loading_addr;
+  SprintfLiteral(buf, "LoadSymbols:   rx_avma=%llx, text_bias=%llx",
+                 (unsigned long long int)(uintptr_t)rx_avma,
+                 (unsigned long long int)text_bias);
+  buf[sizeof(buf) - 1] = 0;
+  log(buf);
+  // END CALCULATE BIAS
+
+  const Shdr* sections =
+      GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);
+  const Shdr* section_names = sections + elf_header->e_shstrndx;
+  const char* names =
+      GetOffset<ElfClass, char>(elf_header, section_names->sh_offset);
+  const char* names_end = names + section_names->sh_size;
+  bool found_usable_info = false;
+
+  // Dwarf Call Frame Information (CFI) is actually independent from
+  // the other DWARF debugging information, and can be used alone.
+  const Shdr* dwarf_cfi_section =
+      FindElfSectionByName<ElfClass>(".debug_frame", SHT_PROGBITS, sections,
+                                     names, names_end, elf_header->e_shnum);
+  if (dwarf_cfi_section) {
+    // Ignore the return value of this function; even without call frame
+    // information, the other debugging information could be perfectly
+    // useful.
+    info->LoadedSection(".debug_frame");
+    bool result = LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".debug_frame",
+                                         dwarf_cfi_section, false, 0, 0,
+                                         big_endian, smap, text_bias, usu, log);
+    found_usable_info = found_usable_info || result;
+    if (result) log("LoadSymbols:   read CFI from .debug_frame");
+  }
+
+  // Linux C++ exception handling information can also provide
+  // unwinding data.
+  const Shdr* eh_frame_section =
+      FindElfSectionByName<ElfClass>(".eh_frame", SHT_PROGBITS, sections, names,
+                                     names_end, elf_header->e_shnum);
+  if (eh_frame_section) {
+    // Pointers in .eh_frame data may be relative to the base addresses of
+    // certain sections. Provide those sections if present.
+    const Shdr* got_section = FindElfSectionByName<ElfClass>(
+        ".got", SHT_PROGBITS, sections, names, names_end, elf_header->e_shnum);
+    const Shdr* text_section = FindElfSectionByName<ElfClass>(
+        ".text", SHT_PROGBITS, sections, names, names_end, elf_header->e_shnum);
+    info->LoadedSection(".eh_frame");
+    // As above, ignore the return value of this function.
+    bool result = LoadDwarfCFI<ElfClass>(
+        obj_file, elf_header, ".eh_frame", eh_frame_section, true, got_section,
+        text_section, big_endian, smap, text_bias, usu, log);
+    found_usable_info = found_usable_info || result;
+    if (result) log("LoadSymbols:   read CFI from .eh_frame");
+  }
+
+  SprintfLiteral(buf, "LoadSymbols: END     %s\n", obj_file.c_str());
+  buf[sizeof(buf) - 1] = 0;
+  log(buf);
+
+  return found_usable_info;
+}
+
+// Return the breakpad symbol file identifier for the architecture of
+// ELF_HEADER.
+template <typename ElfClass>
+const char* ElfArchitecture(const typename ElfClass::Ehdr* elf_header) {
+  typedef typename ElfClass::Half Half;
+  Half arch = elf_header->e_machine;
+  switch (arch) {
+    case EM_386:
+      return "x86";
+    case EM_ARM:
+      return "arm";
+    case EM_AARCH64:
+      return "arm64";
+    case EM_MIPS:
+      return "mips";
+    case EM_PPC64:
+      return "ppc64";
+    case EM_PPC:
+      return "ppc";
+    case EM_S390:
+      return "s390";
+    case EM_SPARC:
+      return "sparc";
+    case EM_SPARCV9:
+      return "sparcv9";
+    case EM_X86_64:
+      return "x86_64";
+    default:
+      return NULL;
+  }
+}
+
+// Format the Elf file identifier in IDENTIFIER as a UUID with the
+// dashes removed.
+string FormatIdentifier(unsigned char identifier[16]) {
+  char identifier_str[40];
+  lul::FileID::ConvertIdentifierToString(identifier, identifier_str,
+                                         sizeof(identifier_str));
+  string id_no_dash;
+  for (int i = 0; identifier_str[i] != '\0'; ++i)
+    if (identifier_str[i] != '-') id_no_dash += identifier_str[i];
+  // Add an extra "0" by the end.  PDB files on Windows have an 'age'
+  // number appended to the end of the file identifier; this isn't
+  // really used or necessary on other platforms, but be consistent.
+  id_no_dash += '0';
+  return id_no_dash;
+}
+
+// Return the non-directory portion of FILENAME: the portion after the
+// last slash, or the whole filename if there are no slashes.
+string BaseFileName(const string& filename) {
+  // Lots of copies!  basename's behavior is less than ideal.
+  char* c_filename = strdup(filename.c_str());
+  string base = basename(c_filename);
+  free(c_filename);
+  return base;
+}
+
+template <typename ElfClass>
+bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,
+                            const string& obj_filename,
+                            const vector<string>& debug_dirs, SecMap* smap,
+                            void* rx_avma, size_t rx_size,
+                            UniqueStringUniverse* usu,
+                            void (*log)(const char*)) {
+  typedef typename ElfClass::Ehdr Ehdr;
+
+  unsigned char identifier[16];
+  if (!lul ::FileID::ElfFileIdentifierFromMappedFile(elf_header, identifier)) {
+    fprintf(stderr, "%s: unable to generate file identifier\n",
+            obj_filename.c_str());
+    return false;
+  }
+
+  const char* architecture = ElfArchitecture<ElfClass>(elf_header);
+  if (!architecture) {
+    fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",
+            obj_filename.c_str(), elf_header->e_machine);
+    return false;
+  }
+
+  // Figure out what endianness this file is.
+  bool big_endian;
+  if (!ElfEndianness<ElfClass>(elf_header, &big_endian)) return false;
+
+  string name = BaseFileName(obj_filename);
+  string os = "Linux";
+  string id = FormatIdentifier(identifier);
+
+  LoadSymbolsInfo<ElfClass> info(debug_dirs);
+  if (!LoadSymbols<ElfClass>(obj_filename, big_endian, elf_header,
+                             !debug_dirs.empty(), &info, smap, rx_avma, rx_size,
+                             usu, log)) {
+    const string debuglink_file = info.debuglink_file();
+    if (debuglink_file.empty()) return false;
+
+    // Load debuglink ELF file.
+    fprintf(stderr, "Found debugging info in %s\n", debuglink_file.c_str());
+    MmapWrapper debug_map_wrapper;
+    Ehdr* debug_elf_header = NULL;
+    if (!LoadELF(debuglink_file, &debug_map_wrapper,
+                 reinterpret_cast<void**>(&debug_elf_header)))
+      return false;
+    // Sanity checks to make sure everything matches up.
+    const char* debug_architecture =
+        ElfArchitecture<ElfClass>(debug_elf_header);
+    if (!debug_architecture) {
+      fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",
+              debuglink_file.c_str(), debug_elf_header->e_machine);
+      return false;
+    }
+    if (strcmp(architecture, debug_architecture)) {
+      fprintf(stderr,
+              "%s with ELF machine architecture %s does not match "
+              "%s with ELF architecture %s\n",
+              debuglink_file.c_str(), debug_architecture, obj_filename.c_str(),
+              architecture);
+      return false;
+    }
+
+    bool debug_big_endian;
+    if (!ElfEndianness<ElfClass>(debug_elf_header, &debug_big_endian))
+      return false;
+    if (debug_big_endian != big_endian) {
+      fprintf(stderr, "%s and %s does not match in endianness\n",
+              obj_filename.c_str(), debuglink_file.c_str());
+      return false;
+    }
+
+    if (!LoadSymbols<ElfClass>(debuglink_file, debug_big_endian,
+                               debug_elf_header, false, &info, smap, rx_avma,
+                               rx_size, usu, log)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+}  // namespace
+
+namespace lul {
+
+bool ReadSymbolDataInternal(const uint8_t* obj_file, const string& obj_filename,
+                            const vector<string>& debug_dirs, SecMap* smap,
+                            void* rx_avma, size_t rx_size,
+                            UniqueStringUniverse* usu,
+                            void (*log)(const char*)) {
+  if (!IsValidElf(obj_file)) {
+    fprintf(stderr, "Not a valid ELF file: %s\n", obj_filename.c_str());
+    return false;
+  }
+
+  int elfclass = ElfClass(obj_file);
+  if (elfclass == ELFCLASS32) {
+    return ReadSymbolDataElfClass<ElfClass32>(
+        reinterpret_cast<const Elf32_Ehdr*>(obj_file), obj_filename, debug_dirs,
+        smap, rx_avma, rx_size, usu, log);
+  }
+  if (elfclass == ELFCLASS64) {
+    return ReadSymbolDataElfClass<ElfClass64>(
+        reinterpret_cast<const Elf64_Ehdr*>(obj_file), obj_filename, debug_dirs,
+        smap, rx_avma, rx_size, usu, log);
+  }
+
+  return false;
+}
+
+bool ReadSymbolData(const string& obj_file, const vector<string>& debug_dirs,
+                    SecMap* smap, void* rx_avma, size_t rx_size,
+                    UniqueStringUniverse* usu, void (*log)(const char*)) {
+  MmapWrapper map_wrapper;
+  void* elf_header = NULL;
+  if (!LoadELF(obj_file, &map_wrapper, &elf_header)) return false;
+
+  return ReadSymbolDataInternal(reinterpret_cast<uint8_t*>(elf_header),
+                                obj_file, debug_dirs, smap, rx_avma, rx_size,
+                                usu, log);
+}
+
+namespace {
+
+template <typename ElfClass>
+void FindElfClassSection(const char* elf_base, const char* section_name,
+                         typename ElfClass::Word section_type,
+                         const void** section_start, int* section_size) {
+  typedef typename ElfClass::Ehdr Ehdr;
+  typedef typename ElfClass::Shdr Shdr;
+
+  MOZ_ASSERT(elf_base);
+  MOZ_ASSERT(section_start);
+  MOZ_ASSERT(section_size);
+
+  MOZ_ASSERT(strncmp(elf_base, ELFMAG, SELFMAG) == 0);
+
+  const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
+  MOZ_ASSERT(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
+
+  const Shdr* sections =
+      GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);
+  const Shdr* section_names = sections + elf_header->e_shstrndx;
+  const char* names =
+      GetOffset<ElfClass, char>(elf_header, section_names->sh_offset);
+  const char* names_end = names + section_names->sh_size;
+
+  const Shdr* section =
+      FindElfSectionByName<ElfClass>(section_name, section_type, sections,
+                                     names, names_end, elf_header->e_shnum);
+
+  if (section != NULL && section->sh_size > 0) {
+    *section_start = elf_base + section->sh_offset;
+    *section_size = section->sh_size;
+  }
+}
+
+template <typename ElfClass>
+void FindElfClassSegment(const char* elf_base,
+                         typename ElfClass::Word segment_type,
+                         const void** segment_start, int* segment_size) {
+  typedef typename ElfClass::Ehdr Ehdr;
+  typedef typename ElfClass::Phdr Phdr;
+
+  MOZ_ASSERT(elf_base);
+  MOZ_ASSERT(segment_start);
+  MOZ_ASSERT(segment_size);
+
+  MOZ_ASSERT(strncmp(elf_base, ELFMAG, SELFMAG) == 0);
+
+  const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
+  MOZ_ASSERT(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
+
+  const Phdr* phdrs =
+      GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff);
+
+  for (int i = 0; i < elf_header->e_phnum; ++i) {
+    if (phdrs[i].p_type == segment_type) {
+      *segment_start = elf_base + phdrs[i].p_offset;
+      *segment_size = phdrs[i].p_filesz;
+      return;
+    }
+  }
+}
+
+}  // namespace
+
+bool IsValidElf(const void* elf_base) {
+  return strncmp(reinterpret_cast<const char*>(elf_base), ELFMAG, SELFMAG) == 0;
+}
+
+int ElfClass(const void* elf_base) {
+  const ElfW(Ehdr)* elf_header = reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
+
+  return elf_header->e_ident[EI_CLASS];
+}
+
+bool FindElfSection(const void* elf_mapped_base, const char* section_name,
+                    uint32_t section_type, const void** section_start,
+                    int* section_size, int* elfclass) {
+  MOZ_ASSERT(elf_mapped_base);
+  MOZ_ASSERT(section_start);
+  MOZ_ASSERT(section_size);
+
+  *section_start = NULL;
+  *section_size = 0;
+
+  if (!IsValidElf(elf_mapped_base)) return false;
+
+  int cls = ElfClass(elf_mapped_base);
+  if (elfclass) {
+    *elfclass = cls;
+  }
+
+  const char* elf_base = static_cast<const char*>(elf_mapped_base);
+
+  if (cls == ELFCLASS32) {
+    FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
+                                    section_start, section_size);
+    return *section_start != NULL;
+  } else if (cls == ELFCLASS64) {
+    FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
+                                    section_start, section_size);
+    return *section_start != NULL;
+  }
+
+  return false;
+}
+
+bool FindElfSegment(const void* elf_mapped_base, uint32_t segment_type,
+                    const void** segment_start, int* segment_size,
+                    int* elfclass) {
+  MOZ_ASSERT(elf_mapped_base);
+  MOZ_ASSERT(segment_start);
+  MOZ_ASSERT(segment_size);
+
+  *segment_start = NULL;
+  *segment_size = 0;
+
+  if (!IsValidElf(elf_mapped_base)) return false;
+
+  int cls = ElfClass(elf_mapped_base);
+  if (elfclass) {
+    *elfclass = cls;
+  }
+
+  const char* elf_base = static_cast<const char*>(elf_mapped_base);
+
+  if (cls == ELFCLASS32) {
+    FindElfClassSegment<ElfClass32>(elf_base, segment_type, segment_start,
+                                    segment_size);
+    return *segment_start != NULL;
+  } else if (cls == ELFCLASS64) {
+    FindElfClassSegment<ElfClass64>(elf_base, segment_type, segment_start,
+                                    segment_size);
+    return *segment_start != NULL;
+  }
+
+  return false;
+}
+
+// (derived from)
+// file_id.cc: Return a unique identifier for a file
+//
+// See file_id.h for documentation
+//
+
+// ELF note name and desc are 32-bits word padded.
+#define NOTE_PADDING(a) ((a + 3) & ~3)
+
+// These functions are also used inside the crashed process, so be safe
+// and use the syscall/libc wrappers instead of direct syscalls or libc.
+
+template <typename ElfClass>
+static bool ElfClassBuildIDNoteIdentifier(const void* section, int length,
+                                          uint8_t identifier[kMDGUIDSize]) {
+  typedef typename ElfClass::Nhdr Nhdr;
+
+  const void* section_end = reinterpret_cast<const char*>(section) + length;
+  const Nhdr* note_header = reinterpret_cast<const Nhdr*>(section);
+  while (reinterpret_cast<const void*>(note_header) < section_end) {
+    if (note_header->n_type == NT_GNU_BUILD_ID) break;
+    note_header = reinterpret_cast<const Nhdr*>(
+        reinterpret_cast<const char*>(note_header) + sizeof(Nhdr) +
+        NOTE_PADDING(note_header->n_namesz) +
+        NOTE_PADDING(note_header->n_descsz));
+  }
+  if (reinterpret_cast<const void*>(note_header) >= section_end ||
+      note_header->n_descsz == 0) {
+    return false;
+  }
+
+  const char* build_id = reinterpret_cast<const char*>(note_header) +
+                         sizeof(Nhdr) + NOTE_PADDING(note_header->n_namesz);
+  // Copy as many bits of the build ID as will fit
+  // into the GUID space.
+  memset(identifier, 0, kMDGUIDSize);
+  memcpy(identifier, build_id,
+         std::min(kMDGUIDSize, (size_t)note_header->n_descsz));
+
+  return true;
+}
+
+// Attempt to locate a .note.gnu.build-id section in an ELF binary
+// and copy as many bytes of it as will fit into |identifier|.
+static bool FindElfBuildIDNote(const void* elf_mapped_base,
+                               uint8_t identifier[kMDGUIDSize]) {
+  void* note_section;
+  int note_size, elfclass;
+  if ((!FindElfSegment(elf_mapped_base, PT_NOTE, (const void**)&note_section,
+                       &note_size, &elfclass) ||
+       note_size == 0) &&
+      (!FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
+                       (const void**)&note_section, &note_size, &elfclass) ||
+       note_size == 0)) {
+    return false;
+  }
+
+  if (elfclass == ELFCLASS32) {
+    return ElfClassBuildIDNoteIdentifier<ElfClass32>(note_section, note_size,
+                                                     identifier);
+  } else if (elfclass == ELFCLASS64) {
+    return ElfClassBuildIDNoteIdentifier<ElfClass64>(note_section, note_size,
+                                                     identifier);
+  }
+
+  return false;
+}
+
+// Attempt to locate the .text section of an ELF binary and generate
+// a simple hash by XORing the first page worth of bytes into |identifier|.
+static bool HashElfTextSection(const void* elf_mapped_base,
+                               uint8_t identifier[kMDGUIDSize]) {
+  void* text_section;
+  int text_size;
+  if (!FindElfSection(elf_mapped_base, ".text", SHT_PROGBITS,
+                      (const void**)&text_section, &text_size, NULL) ||
+      text_size == 0) {
+    return false;
+  }
+
+  memset(identifier, 0, kMDGUIDSize);
+  const uint8_t* ptr = reinterpret_cast<const uint8_t*>(text_section);
+  const uint8_t* ptr_end = ptr + std::min(text_size, 4096);
+  while (ptr < ptr_end) {
+    for (unsigned i = 0; i < kMDGUIDSize; i++) identifier[i] ^= ptr[i];
+    ptr += kMDGUIDSize;
+  }
+  return true;
+}
+
+// static
+bool FileID::ElfFileIdentifierFromMappedFile(const void* base,
+                                             uint8_t identifier[kMDGUIDSize]) {
+  // Look for a build id note first.
+  if (FindElfBuildIDNote(base, identifier)) return true;
+
+  // Fall back on hashing the first page of the text section.
+  return HashElfTextSection(base, identifier);
+}
+
+// static
+void FileID::ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
+                                       char* buffer, int buffer_length) {
+  uint8_t identifier_swapped[kMDGUIDSize];
+
+  // Endian-ness swap to match dump processor expectation.
+  memcpy(identifier_swapped, identifier, kMDGUIDSize);
+  uint32_t* data1 = reinterpret_cast<uint32_t*>(identifier_swapped);
+  *data1 = htonl(*data1);
+  uint16_t* data2 = reinterpret_cast<uint16_t*>(identifier_swapped + 4);
+  *data2 = htons(*data2);
+  uint16_t* data3 = reinterpret_cast<uint16_t*>(identifier_swapped + 6);
+  *data3 = htons(*data3);
+
+  int buffer_idx = 0;
+  for (unsigned int idx = 0;
+       (buffer_idx < buffer_length) && (idx < kMDGUIDSize); ++idx) {
+    int hi = (identifier_swapped[idx] >> 4) & 0x0F;
+    int lo = (identifier_swapped[idx]) & 0x0F;
+
+    if (idx == 4 || idx == 6 || idx == 8 || idx == 10)
+      buffer[buffer_idx++] = '-';
+
+    buffer[buffer_idx++] = (hi >= 10) ? 'A' + hi - 10 : '0' + hi;
+    buffer[buffer_idx++] = (lo >= 10) ? 'A' + lo - 10 : '0' + lo;
+  }
+
+  // NULL terminate
+  buffer[(buffer_idx < buffer_length) ? buffer_idx : buffer_idx - 1] = 0;
+}
+
+}  // namespace lul
diff --git a/mozglue/baseprofiler/lul/LulElfExt.h b/mozglue/baseprofiler/lul/LulElfExt.h
new file mode 100644
index 0000000000..73d9ff7f15
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulElfExt.h
@@ -0,0 +1,69 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2006, 2011, 2012 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/linux/dump_symbols.h
+
+#ifndef LulElfExt_h
+#define LulElfExt_h
+
+// These two functions are the external interface to the
+// ELF/Dwarf/EXIDX reader.
+
+#include "LulMainInt.h"
+
+using lul::SecMap;
+
+namespace lul {
+
+class UniqueStringUniverse;
+
+// Find all the unwind information in OBJ_FILE, an ELF executable
+// or shared library, and add it to SMAP.
+bool ReadSymbolData(const std::string& obj_file,
+                    const std::vector<std::string>& debug_dirs, SecMap* smap,
+                    void* rx_avma, size_t rx_size, UniqueStringUniverse* usu,
+                    void (*log)(const char*));
+
+// The same as ReadSymbolData, except that OBJ_FILE is assumed to
+// point to a mapped-in image of OBJ_FILENAME.
+bool ReadSymbolDataInternal(const uint8_t* obj_file,
+                            const std::string& obj_filename,
+                            const std::vector<std::string>& debug_dirs,
+                            SecMap* smap, void* rx_avma, size_t rx_size,
+                            UniqueStringUniverse* usu,
+                            void (*log)(const char*));
+
+}  // namespace lul
+
+#endif  // LulElfExt_h
diff --git a/mozglue/baseprofiler/lul/LulElfInt.h b/mozglue/baseprofiler/lul/LulElfInt.h
new file mode 100644
index 0000000000..31ffba8ff0
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulElfInt.h
@@ -0,0 +1,218 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+
+// Copyright (c) 2006, 2012, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is derived from the following files in
+// toolkit/crashreporter/google-breakpad:
+//   src/common/android/include/elf.h
+//   src/common/linux/elfutils.h
+//   src/common/linux/file_id.h
+//   src/common/linux/elfutils-inl.h
+
+#ifndef LulElfInt_h
+#define LulElfInt_h
+
+// This header defines functions etc internal to the ELF reader.  It
+// should not be included outside of LulElf.cpp.
+
+#include <elf.h>
+#include <stdlib.h>
+
+#include "mozilla/Assertions.h"
+
+#include "PlatformMacros.h"
+
+// (derived from)
+// elfutils.h: Utilities for dealing with ELF files.
+//
+#include <link.h>
+
+#if defined(GP_OS_android)
+
+// From toolkit/crashreporter/google-breakpad/src/common/android/include/elf.h
+// The Android headers don't always define this constant.
+#  ifndef EM_X86_64
+#    define EM_X86_64 62
+#  endif
+
+#  ifndef EM_PPC64
+#    define EM_PPC64 21
+#  endif
+
+#  ifndef EM_S390
+#    define EM_S390 22
+#  endif
+
+#  ifndef NT_GNU_BUILD_ID
+#    define NT_GNU_BUILD_ID 3
+#  endif
+
+#  ifndef ElfW
+#    define ElfW(type) _ElfW(Elf, ELFSIZE, type)
+#    define _ElfW(e, w, t) _ElfW_1(e, w, _##t)
+#    define _ElfW_1(e, w, t) e##w##t
+#  endif
+
+#endif
+
+#if defined(GP_OS_freebsd)
+
+#  ifndef ElfW
+#    define ElfW(type) Elf_##type
+#  endif
+
+#endif
+
+namespace lul {
+
+// Traits classes so consumers can write templatized code to deal
+// with specific ELF bits.
+struct ElfClass32 {
+  typedef Elf32_Addr Addr;
+  typedef Elf32_Ehdr Ehdr;
+  typedef Elf32_Nhdr Nhdr;
+  typedef Elf32_Phdr Phdr;
+  typedef Elf32_Shdr Shdr;
+  typedef Elf32_Half Half;
+  typedef Elf32_Off Off;
+  typedef Elf32_Word Word;
+  static const int kClass = ELFCLASS32;
+  static const size_t kAddrSize = sizeof(Elf32_Addr);
+};
+
+struct ElfClass64 {
+  typedef Elf64_Addr Addr;
+  typedef Elf64_Ehdr Ehdr;
+  typedef Elf64_Nhdr Nhdr;
+  typedef Elf64_Phdr Phdr;
+  typedef Elf64_Shdr Shdr;
+  typedef Elf64_Half Half;
+  typedef Elf64_Off Off;
+  typedef Elf64_Word Word;
+  static const int kClass = ELFCLASS64;
+  static const size_t kAddrSize = sizeof(Elf64_Addr);
+};
+
+bool IsValidElf(const void* elf_header);
+int ElfClass(const void* elf_base);
+
+// Attempt to find a section named |section_name| of type |section_type|
+// in the ELF binary data at |elf_mapped_base|. On success, returns true
+// and sets |*section_start| to point to the start of the section data,
+// and |*section_size| to the size of the section's data. If |elfclass|
+// is not NULL, set |*elfclass| to the ELF file class.
+bool FindElfSection(const void* elf_mapped_base, const char* section_name,
+                    uint32_t section_type, const void** section_start,
+                    int* section_size, int* elfclass);
+
+// Internal helper method, exposed for convenience for callers
+// that already have more info.
+template <typename ElfClass>
+const typename ElfClass::Shdr* FindElfSectionByName(
+    const char* name, typename ElfClass::Word section_type,
+    const typename ElfClass::Shdr* sections, const char* section_names,
+    const char* names_end, int nsection);
+
+// Attempt to find the first segment of type |segment_type| in the ELF
+// binary data at |elf_mapped_base|. On success, returns true and sets
+// |*segment_start| to point to the start of the segment data, and
+// and |*segment_size| to the size of the segment's data. If |elfclass|
+// is not NULL, set |*elfclass| to the ELF file class.
+bool FindElfSegment(const void* elf_mapped_base, uint32_t segment_type,
+                    const void** segment_start, int* segment_size,
+                    int* elfclass);
+
+// Convert an offset from an Elf header into a pointer to the mapped
+// address in the current process. Takes an extra template parameter
+// to specify the return type to avoid having to dynamic_cast the
+// result.
+template <typename ElfClass, typename T>
+const T* GetOffset(const typename ElfClass::Ehdr* elf_header,
+                   typename ElfClass::Off offset);
+
+// (derived from)
+// file_id.h: Return a unique identifier for a file
+//
+
+static const size_t kMDGUIDSize = sizeof(MDGUID);
+
+class FileID {
+ public:
+  // Load the identifier for the elf file mapped into memory at |base| into
+  // |identifier|.  Return false if the identifier could not be created for the
+  // file.
+  static bool ElfFileIdentifierFromMappedFile(const void* base,
+                                              uint8_t identifier[kMDGUIDSize]);
+
+  // Convert the |identifier| data to a NULL terminated string.  The string will
+  // be formatted as a UUID (e.g., 22F065BB-FC9C-49F7-80FE-26A7CEBD7BCE).
+  // The |buffer| should be at least 37 bytes long to receive all of the data
+  // and termination.  Shorter buffers will contain truncated data.
+  static void ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
+                                        char* buffer, int buffer_length);
+};
+
+template <typename ElfClass, typename T>
+const T* GetOffset(const typename ElfClass::Ehdr* elf_header,
+                   typename ElfClass::Off offset) {
+  return reinterpret_cast<const T*>(reinterpret_cast<uintptr_t>(elf_header) +
+                                    offset);
+}
+
+template <typename ElfClass>
+const typename ElfClass::Shdr* FindElfSectionByName(
+    const char* name, typename ElfClass::Word section_type,
+    const typename ElfClass::Shdr* sections, const char* section_names,
+    const char* names_end, int nsection) {
+  MOZ_ASSERT(name != NULL);
+  MOZ_ASSERT(sections != NULL);
+  MOZ_ASSERT(nsection > 0);
+
+  int name_len = strlen(name);
+  if (name_len == 0) return NULL;
+
+  for (int i = 0; i < nsection; ++i) {
+    const char* section_name = section_names + sections[i].sh_name;
+    if (sections[i].sh_type == section_type &&
+        names_end - section_name >= name_len + 1 &&
+        strcmp(name, section_name) == 0) {
+      return sections + i;
+    }
+  }
+  return NULL;
+}
+
+}  // namespace lul
+
+// And finally, the external interface, offered to LulMain.cpp
+#include "LulElfExt.h"
+
+#endif  // LulElfInt_h
diff --git a/mozglue/baseprofiler/lul/LulMain.cpp b/mozglue/baseprofiler/lul/LulMain.cpp
new file mode 100644
index 0000000000..75f205ac3a
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulMain.cpp
@@ -0,0 +1,1958 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LulMain.h"
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>  // write(), only for testing LUL
+
+#include <algorithm>  // std::sort
+#include <string>
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MemoryChecking.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+
+#include "BaseProfiler.h"
+#include "LulCommonExt.h"
+#include "LulElfExt.h"
+#include "LulMainInt.h"
+
+using mozilla::baseprofiler::profiler_current_process_id;
+using mozilla::baseprofiler::profiler_current_thread_id;
+
+// Set this to 1 for verbose logging
+#define DEBUG_MAIN 0
+
+namespace lul {
+
+using mozilla::CheckedInt;
+using mozilla::DebugOnly;
+using mozilla::MallocSizeOf;
+using mozilla::Unused;
+using std::pair;
+using std::string;
+using std::vector;
+
+// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+//
+// Some functions in this file are marked RUNS IN NO-MALLOC CONTEXT.
+// Any such function -- and, hence, the transitive closure of those
+// reachable from it -- must not do any dynamic memory allocation.
+// Doing so risks deadlock.  There is exactly one root function for
+// the transitive closure: Lul::Unwind.
+//
+// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+
+////////////////////////////////////////////////////////////////
+// RuleSet                                                    //
+////////////////////////////////////////////////////////////////
+
+static const char* NameOf_DW_REG(int16_t aReg) {
+  switch (aReg) {
+    case DW_REG_CFA:
+      return "cfa";
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+    case DW_REG_INTEL_XBP:
+      return "xbp";
+    case DW_REG_INTEL_XSP:
+      return "xsp";
+    case DW_REG_INTEL_XIP:
+      return "xip";
+#elif defined(GP_ARCH_arm)
+    case DW_REG_ARM_R7:
+      return "r7";
+    case DW_REG_ARM_R11:
+      return "r11";
+    case DW_REG_ARM_R12:
+      return "r12";
+    case DW_REG_ARM_R13:
+      return "r13";
+    case DW_REG_ARM_R14:
+      return "r14";
+    case DW_REG_ARM_R15:
+      return "r15";
+#elif defined(GP_ARCH_arm64)
+    case DW_REG_AARCH64_X29:
+      return "x29";
+    case DW_REG_AARCH64_X30:
+      return "x30";
+    case DW_REG_AARCH64_SP:
+      return "sp";
+#elif defined(GP_ARCH_mips64)
+    case DW_REG_MIPS_SP:
+      return "sp";
+    case DW_REG_MIPS_FP:
+      return "fp";
+    case DW_REG_MIPS_PC:
+      return "pc";
+#else
+#  error "Unsupported arch"
+#endif
+    default:
+      return "???";
+  }
+}
+
+string LExpr::ShowRule(const char* aNewReg) const {
+  char buf[64];
+  string res = string(aNewReg) + "=";
+  switch (mHow) {
+    case UNKNOWN:
+      res += "Unknown";
+      break;
+    case NODEREF:
+      SprintfLiteral(buf, "%s+%d", NameOf_DW_REG(mReg), (int)mOffset);
+      res += buf;
+      break;
+    case DEREF:
+      SprintfLiteral(buf, "*(%s+%d)", NameOf_DW_REG(mReg), (int)mOffset);
+      res += buf;
+      break;
+    case PFXEXPR:
+      SprintfLiteral(buf, "PfxExpr-at-%d", (int)mOffset);
+      res += buf;
+      break;
+    default:
+      res += "???";
+      break;
+  }
+  return res;
+}
+
+void RuleSet::Print(void (*aLog)(const char*)) const {
+  char buf[96];
+  SprintfLiteral(buf, "[%llx .. %llx]: let ", (unsigned long long int)mAddr,
+                 (unsigned long long int)(mAddr + mLen - 1));
+  string res = string(buf);
+  res += mCfaExpr.ShowRule("cfa");
+  res += " in";
+  // For each reg we care about, print the recovery expression.
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+  res += mXipExpr.ShowRule(" RA");
+  res += mXspExpr.ShowRule(" SP");
+  res += mXbpExpr.ShowRule(" BP");
+#elif defined(GP_ARCH_arm)
+  res += mR15expr.ShowRule(" R15");
+  res += mR7expr.ShowRule(" R7");
+  res += mR11expr.ShowRule(" R11");
+  res += mR12expr.ShowRule(" R12");
+  res += mR13expr.ShowRule(" R13");
+  res += mR14expr.ShowRule(" R14");
+#elif defined(GP_ARCH_arm64)
+  res += mX29expr.ShowRule(" X29");
+  res += mX30expr.ShowRule(" X30");
+  res += mSPexpr.ShowRule(" SP");
+#elif defined(GP_ARCH_mips64)
+  res += mPCexpr.ShowRule(" PC");
+  res += mSPexpr.ShowRule(" SP");
+  res += mFPexpr.ShowRule(" FP");
+#else
+#  error "Unsupported arch"
+#endif
+  aLog(res.c_str());
+}
+
+LExpr* RuleSet::ExprForRegno(DW_REG_NUMBER aRegno) {
+  switch (aRegno) {
+    case DW_REG_CFA:
+      return &mCfaExpr;
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+    case DW_REG_INTEL_XIP:
+      return &mXipExpr;
+    case DW_REG_INTEL_XSP:
+      return &mXspExpr;
+    case DW_REG_INTEL_XBP:
+      return &mXbpExpr;
+#elif defined(GP_ARCH_arm)
+    case DW_REG_ARM_R15:
+      return &mR15expr;
+    case DW_REG_ARM_R14:
+      return &mR14expr;
+    case DW_REG_ARM_R13:
+      return &mR13expr;
+    case DW_REG_ARM_R12:
+      return &mR12expr;
+    case DW_REG_ARM_R11:
+      return &mR11expr;
+    case DW_REG_ARM_R7:
+      return &mR7expr;
+#elif defined(GP_ARCH_arm64)
+    case DW_REG_AARCH64_X29:
+      return &mX29expr;
+    case DW_REG_AARCH64_X30:
+      return &mX30expr;
+    case DW_REG_AARCH64_SP:
+      return &mSPexpr;
+#elif defined(GP_ARCH_mips64)
+    case DW_REG_MIPS_SP:
+      return &mSPexpr;
+    case DW_REG_MIPS_FP:
+      return &mFPexpr;
+    case DW_REG_MIPS_PC:
+      return &mPCexpr;
+#else
+#  error "Unknown arch"
+#endif
+    default:
+      return nullptr;
+  }
+}
+
+RuleSet::RuleSet() {
+  mAddr = 0;
+  mLen = 0;
+  // The only other fields are of type LExpr and those are initialised
+  // by LExpr::LExpr().
+}
+
+////////////////////////////////////////////////////////////////
+// SecMap                                                     //
+////////////////////////////////////////////////////////////////
+
+// See header file LulMainInt.h for comments about invariants.
+
+SecMap::SecMap(void (*aLog)(const char*))
+    : mSummaryMinAddr(1), mSummaryMaxAddr(0), mUsable(true), mLog(aLog) {}
+
+SecMap::~SecMap() { mRuleSets.clear(); }
+
+// RUNS IN NO-MALLOC CONTEXT
+RuleSet* SecMap::FindRuleSet(uintptr_t ia) {
+  // Binary search mRuleSets to find one that brackets |ia|.
+  // lo and hi need to be signed, else the loop termination tests
+  // don't work properly.  Note that this works correctly even when
+  // mRuleSets.size() == 0.
+
+  // Can't do this until the array has been sorted and preened.
+  MOZ_ASSERT(mUsable);
+
+  long int lo = 0;
+  long int hi = (long int)mRuleSets.size() - 1;
+  while (true) {
+    // current unsearched space is from lo to hi, inclusive.
+    if (lo > hi) {
+      // not found
+      return nullptr;
+    }
+    long int mid = lo + ((hi - lo) / 2);
+    RuleSet* mid_ruleSet = &mRuleSets[mid];
+    uintptr_t mid_minAddr = mid_ruleSet->mAddr;
+    uintptr_t mid_maxAddr = mid_minAddr + mid_ruleSet->mLen - 1;
+    if (ia < mid_minAddr) {
+      hi = mid - 1;
+      continue;
+    }
+    if (ia > mid_maxAddr) {
+      lo = mid + 1;
+      continue;
+    }
+    MOZ_ASSERT(mid_minAddr <= ia && ia <= mid_maxAddr);
+    return mid_ruleSet;
+  }
+  // NOTREACHED
+}
+
+// Add a RuleSet to the collection.  The rule is copied in.  Calling
+// this makes the map non-searchable.
+void SecMap::AddRuleSet(const RuleSet* rs) {
+  mUsable = false;
+  mRuleSets.push_back(*rs);
+}
+
+// Add a PfxInstr to the vector of such instrs, and return the index
+// in the vector.  Calling this makes the map non-searchable.
+uint32_t SecMap::AddPfxInstr(PfxInstr pfxi) {
+  mUsable = false;
+  mPfxInstrs.push_back(pfxi);
+  return mPfxInstrs.size() - 1;
+}
+
+static bool CmpRuleSetsByAddrLE(const RuleSet& rs1, const RuleSet& rs2) {
+  return rs1.mAddr < rs2.mAddr;
+}
+
+// Prepare the map for searching.  Completely remove any which don't
+// fall inside the specified range [start, +len).
+void SecMap::PrepareRuleSets(uintptr_t aStart, size_t aLen) {
+  if (mRuleSets.empty()) {
+    return;
+  }
+
+  MOZ_ASSERT(aLen > 0);
+  if (aLen == 0) {
+    // This should never happen.
+    mRuleSets.clear();
+    return;
+  }
+
+  // Sort by start addresses.
+  std::sort(mRuleSets.begin(), mRuleSets.end(), CmpRuleSetsByAddrLE);
+
+  // Detect any entry not completely contained within [start, +len).
+  // Set its length to zero, so that the next pass will remove it.
+  for (size_t i = 0; i < mRuleSets.size(); ++i) {
+    RuleSet* rs = &mRuleSets[i];
+    if (rs->mLen > 0 &&
+        (rs->mAddr < aStart || rs->mAddr + rs->mLen > aStart + aLen)) {
+      rs->mLen = 0;
+    }
+  }
+
+  // Iteratively truncate any overlaps and remove any zero length
+  // entries that might result, or that may have been present
+  // initially.  Unless the input is seriously screwy, this is
+  // expected to iterate only once.
+  while (true) {
+    size_t i;
+    size_t n = mRuleSets.size();
+    size_t nZeroLen = 0;
+
+    if (n == 0) {
+      break;
+    }
+
+    for (i = 1; i < n; ++i) {
+      RuleSet* prev = &mRuleSets[i - 1];
+      RuleSet* here = &mRuleSets[i];
+      MOZ_ASSERT(prev->mAddr <= here->mAddr);
+      if (prev->mAddr + prev->mLen > here->mAddr) {
+        prev->mLen = here->mAddr - prev->mAddr;
+      }
+      if (prev->mLen == 0) nZeroLen++;
+    }
+
+    if (mRuleSets[n - 1].mLen == 0) {
+      nZeroLen++;
+    }
+
+    // At this point, the entries are in-order and non-overlapping.
+    // If none of them are zero-length, we are done.
+    if (nZeroLen == 0) {
+      break;
+    }
+
+    // Slide back the entries to remove the zero length ones.
+    size_t j = 0;  // The write-point.
+    for (i = 0; i < n; ++i) {
+      if (mRuleSets[i].mLen == 0) {
+        continue;
+      }
+      if (j != i) mRuleSets[j] = mRuleSets[i];
+      ++j;
+    }
+    MOZ_ASSERT(i == n);
+    MOZ_ASSERT(nZeroLen <= n);
+    MOZ_ASSERT(j == n - nZeroLen);
+    while (nZeroLen > 0) {
+      mRuleSets.pop_back();
+      nZeroLen--;
+    }
+
+    MOZ_ASSERT(mRuleSets.size() == j);
+  }
+
+  size_t n = mRuleSets.size();
+
+#ifdef DEBUG
+  // Do a final check on the rules: their address ranges must be
+  // ascending, non overlapping, non zero sized.
+  if (n > 0) {
+    MOZ_ASSERT(mRuleSets[0].mLen > 0);
+    for (size_t i = 1; i < n; ++i) {
+      RuleSet* prev = &mRuleSets[i - 1];
+      RuleSet* here = &mRuleSets[i];
+      MOZ_ASSERT(prev->mAddr < here->mAddr);
+      MOZ_ASSERT(here->mLen > 0);
+      MOZ_ASSERT(prev->mAddr + prev->mLen <= here->mAddr);
+    }
+  }
+#endif
+
+  // Set the summary min and max address values.
+  if (n == 0) {
+    // Use the values defined in comments in the class declaration.
+    mSummaryMinAddr = 1;
+    mSummaryMaxAddr = 0;
+  } else {
+    mSummaryMinAddr = mRuleSets[0].mAddr;
+    mSummaryMaxAddr = mRuleSets[n - 1].mAddr + mRuleSets[n - 1].mLen - 1;
+  }
+  char buf[150];
+  SprintfLiteral(buf, "PrepareRuleSets: %d entries, smin/smax 0x%llx, 0x%llx\n",
+                 (int)n, (unsigned long long int)mSummaryMinAddr,
+                 (unsigned long long int)mSummaryMaxAddr);
+  buf[sizeof(buf) - 1] = 0;
+  mLog(buf);
+
+  // Is now usable for binary search.
+  mUsable = true;
+
+#if 0
+  mLog("\nRulesets after preening\n");
+  for (size_t i = 0; i < mRuleSets.size(); ++i) {
+    mRuleSets[i].Print(mLog);
+    mLog("\n");
+  }
+  mLog("\n");
+#endif
+}
+
+bool SecMap::IsEmpty() { return mRuleSets.empty(); }
+
+size_t SecMap::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+  size_t n = aMallocSizeOf(this);
+
+  // It's conceivable that these calls would be unsafe with some
+  // implementations of std::vector, but it seems to be working for now...
+  n += aMallocSizeOf(mRuleSets.data());
+  n += aMallocSizeOf(mPfxInstrs.data());
+
+  return n;
+}
+
+////////////////////////////////////////////////////////////////
+// SegArray                                                   //
+////////////////////////////////////////////////////////////////
+
+// A SegArray holds a set of address ranges that together exactly
+// cover an address range, with no overlaps or holes.  Each range has
+// an associated value, which in this case has been specialised to be
+// a simple boolean.  The representation is kept to minimal canonical
+// form in which adjacent ranges with the same associated value are
+// merged together.  Each range is represented by a |struct Seg|.
+//
+// SegArrays are used to keep track of which parts of the address
+// space are known to contain instructions.
+class SegArray {
+ public:
+  void add(uintptr_t lo, uintptr_t hi, bool val) {
+    if (lo > hi) {
+      return;
+    }
+    split_at(lo);
+    if (hi < UINTPTR_MAX) {
+      split_at(hi + 1);
+    }
+    std::vector<Seg>::size_type iLo, iHi, i;
+    iLo = find(lo);
+    iHi = find(hi);
+    for (i = iLo; i <= iHi; ++i) {
+      mSegs[i].val = val;
+    }
+    preen();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  bool getBoundingCodeSegment(/*OUT*/ uintptr_t* rx_min,
+                              /*OUT*/ uintptr_t* rx_max, uintptr_t addr) {
+    std::vector<Seg>::size_type i = find(addr);
+    if (!mSegs[i].val) {
+      return false;
+    }
+    *rx_min = mSegs[i].lo;
+    *rx_max = mSegs[i].hi;
+    return true;
+  }
+
+  SegArray() {
+    Seg s(0, UINTPTR_MAX, false);
+    mSegs.push_back(s);
+  }
+
+ private:
+  struct Seg {
+    Seg(uintptr_t lo, uintptr_t hi, bool val) : lo(lo), hi(hi), val(val) {}
+    uintptr_t lo;
+    uintptr_t hi;
+    bool val;
+  };
+
+  void preen() {
+    for (std::vector<Seg>::iterator iter = mSegs.begin();
+         iter < mSegs.end() - 1; ++iter) {
+      if (iter[0].val != iter[1].val) {
+        continue;
+      }
+      iter[0].hi = iter[1].hi;
+      mSegs.erase(iter + 1);
+      // Back up one, so as not to miss an opportunity to merge
+      // with the entry after this one.
+      --iter;
+    }
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  std::vector<Seg>::size_type find(uintptr_t a) {
+    long int lo = 0;
+    long int hi = (long int)mSegs.size();
+    while (true) {
+      // The unsearched space is lo .. hi inclusive.
+      if (lo > hi) {
+        // Not found.  This can't happen.
+        return (std::vector<Seg>::size_type)(-1);
+      }
+      long int mid = lo + ((hi - lo) / 2);
+      uintptr_t mid_lo = mSegs[mid].lo;
+      uintptr_t mid_hi = mSegs[mid].hi;
+      if (a < mid_lo) {
+        hi = mid - 1;
+        continue;
+      }
+      if (a > mid_hi) {
+        lo = mid + 1;
+        continue;
+      }
+      return (std::vector<Seg>::size_type)mid;
+    }
+  }
+
+  void split_at(uintptr_t a) {
+    std::vector<Seg>::size_type i = find(a);
+    if (mSegs[i].lo == a) {
+      return;
+    }
+    mSegs.insert(mSegs.begin() + i + 1, mSegs[i]);
+    mSegs[i].hi = a - 1;
+    mSegs[i + 1].lo = a;
+  }
+
+  void show() {
+    printf("<< %d entries:\n", (int)mSegs.size());
+    for (std::vector<Seg>::iterator iter = mSegs.begin(); iter < mSegs.end();
+         ++iter) {
+      printf("  %016llx  %016llx  %s\n", (unsigned long long int)(*iter).lo,
+             (unsigned long long int)(*iter).hi,
+             (*iter).val ? "true" : "false");
+    }
+    printf(">>\n");
+  }
+
+  std::vector<Seg> mSegs;
+};
+
+////////////////////////////////////////////////////////////////
+// PriMap                                                     //
+////////////////////////////////////////////////////////////////
+
+class PriMap {
+ public:
+  explicit PriMap(void (*aLog)(const char*)) : mLog(aLog) {}
+
+  // RUNS IN NO-MALLOC CONTEXT
+  pair<const RuleSet*, const vector<PfxInstr>*> Lookup(uintptr_t ia) {
+    SecMap* sm = FindSecMap(ia);
+    return pair<const RuleSet*, const vector<PfxInstr>*>(
+        sm ? sm->FindRuleSet(ia) : nullptr, sm ? sm->GetPfxInstrs() : nullptr);
+  }
+
+  // Add a secondary map.  No overlaps allowed w.r.t. existing
+  // secondary maps.
+  void AddSecMap(mozilla::UniquePtr<SecMap>&& aSecMap) {
+    // We can't add an empty SecMap to the PriMap.  But that's OK
+    // since we'd never be able to find anything in it anyway.
+    if (aSecMap->IsEmpty()) {
+      return;
+    }
+
+    // Iterate through the SecMaps and find the right place for this
+    // one.  At the same time, ensure that the in-order
+    // non-overlapping invariant is preserved (and, generally, holds).
+    // FIXME: this gives a cost that is O(N^2) in the total number of
+    // shared objects in the system.  ToDo: better.
+    MOZ_ASSERT(aSecMap->mSummaryMinAddr <= aSecMap->mSummaryMaxAddr);
+
+    size_t num_secMaps = mSecMaps.size();
+    uintptr_t i;
+    for (i = 0; i < num_secMaps; ++i) {
+      mozilla::UniquePtr<SecMap>& sm_i = mSecMaps[i];
+      MOZ_ASSERT(sm_i->mSummaryMinAddr <= sm_i->mSummaryMaxAddr);
+      if (aSecMap->mSummaryMinAddr < sm_i->mSummaryMaxAddr) {
+        // |aSecMap| needs to be inserted immediately before mSecMaps[i].
+        break;
+      }
+    }
+    MOZ_ASSERT(i <= num_secMaps);
+    if (i == num_secMaps) {
+      // It goes at the end.
+      mSecMaps.push_back(std::move(aSecMap));
+    } else {
+      std::vector<mozilla::UniquePtr<SecMap>>::iterator iter =
+          mSecMaps.begin() + i;
+      mSecMaps.insert(iter, std::move(aSecMap));
+    }
+    char buf[100];
+    SprintfLiteral(buf, "AddSecMap: now have %d SecMaps\n",
+                   (int)mSecMaps.size());
+    buf[sizeof(buf) - 1] = 0;
+    mLog(buf);
+  }
+
+  // Remove and delete any SecMaps in the mapping, that intersect
+  // with the specified address range.
+  void RemoveSecMapsInRange(uintptr_t avma_min, uintptr_t avma_max) {
+    MOZ_ASSERT(avma_min <= avma_max);
+    size_t num_secMaps = mSecMaps.size();
+    if (num_secMaps > 0) {
+      intptr_t i;
+      // Iterate from end to start over the vector, so as to ensure
+      // that the special case where |avma_min| and |avma_max| denote
+      // the entire address space, can be completed in time proportional
+      // to the number of elements in the map.
+      for (i = (intptr_t)num_secMaps - 1; i >= 0; i--) {
+        mozilla::UniquePtr<SecMap>& sm_i = mSecMaps[i];
+        if (sm_i->mSummaryMaxAddr < avma_min ||
+            avma_max < sm_i->mSummaryMinAddr) {
+          // There's no overlap.  Move on.
+          continue;
+        }
+        // We need to remove mSecMaps[i] and slide all those above it
+        // downwards to cover the hole.
+        mSecMaps.erase(mSecMaps.begin() + i);
+      }
+    }
+  }
+
+  // Return the number of currently contained SecMaps.
+  size_t CountSecMaps() { return mSecMaps.size(); }
+
+  size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+    size_t n = aMallocSizeOf(this);
+
+    // It's conceivable that this call would be unsafe with some
+    // implementations of std::vector, but it seems to be working for now...
+    n += aMallocSizeOf(mSecMaps.data());
+
+    for (size_t i = 0; i < mSecMaps.size(); i++) {
+      n += mSecMaps[i]->SizeOfIncludingThis(aMallocSizeOf);
+    }
+
+    return n;
+  }
+
+ private:
+  // RUNS IN NO-MALLOC CONTEXT
+  SecMap* FindSecMap(uintptr_t ia) {
+    // Binary search mSecMaps to find one that brackets |ia|.
+    // lo and hi need to be signed, else the loop termination tests
+    // don't work properly.
+    long int lo = 0;
+    long int hi = (long int)mSecMaps.size() - 1;
+    while (true) {
+      // current unsearched space is from lo to hi, inclusive.
+      if (lo > hi) {
+        // not found
+        return nullptr;
+      }
+      long int mid = lo + ((hi - lo) / 2);
+      mozilla::UniquePtr<SecMap>& mid_secMap = mSecMaps[mid];
+      uintptr_t mid_minAddr = mid_secMap->mSummaryMinAddr;
+      uintptr_t mid_maxAddr = mid_secMap->mSummaryMaxAddr;
+      if (ia < mid_minAddr) {
+        hi = mid - 1;
+        continue;
+      }
+      if (ia > mid_maxAddr) {
+        lo = mid + 1;
+        continue;
+      }
+      MOZ_ASSERT(mid_minAddr <= ia && ia <= mid_maxAddr);
+      return mid_secMap.get();
+    }
+    // NOTREACHED
+  }
+
+ private:
+  // sorted array of per-object ranges, non overlapping, non empty
+  std::vector<mozilla::UniquePtr<SecMap>> mSecMaps;
+
+  // a logging sink, for debugging.
+  void (*mLog)(const char*);
+};
+
+////////////////////////////////////////////////////////////////
+// LUL                                                        //
+////////////////////////////////////////////////////////////////
+
+#define LUL_LOG(_str)                                                          \
+  do {                                                                         \
+    char buf[200];                                                             \
+    SprintfLiteral(buf, "LUL: pid %" PRIu64 " tid %" PRIu64 " lul-obj %p: %s", \
+                   uint64_t(profiler_current_process_id().ToNumber()),         \
+                   uint64_t(profiler_current_thread_id().ToNumber()), this,    \
+                   (_str));                                                    \
+    buf[sizeof(buf) - 1] = 0;                                                  \
+    mLog(buf);                                                                 \
+  } while (0)
+
+LUL::LUL(void (*aLog)(const char*))
+    : mLog(aLog),
+      mAdminMode(true),
+      mAdminThreadId(profiler_current_thread_id()),
+      mPriMap(new PriMap(aLog)),
+      mSegArray(new SegArray()),
+      mUSU(new UniqueStringUniverse()) {
+  LUL_LOG("LUL::LUL: Created object");
+}
+
+LUL::~LUL() {
+  LUL_LOG("LUL::~LUL: Destroyed object");
+  delete mPriMap;
+  delete mSegArray;
+  mLog = nullptr;
+  delete mUSU;
+}
+
+void LUL::MaybeShowStats() {
+  // This is racey in the sense that it can't guarantee that
+  //   n_new == n_new_Context + n_new_CFI + n_new_Scanned
+  // if it should happen that mStats is updated by some other thread
+  // in between computation of n_new and n_new_{Context,CFI,FP}.
+  // But it's just stats printing, so we don't really care.
+  uint32_t n_new = mStats - mStatsPrevious;
+  if (n_new >= 5000) {
+    uint32_t n_new_Context = mStats.mContext - mStatsPrevious.mContext;
+    uint32_t n_new_CFI = mStats.mCFI - mStatsPrevious.mCFI;
+    uint32_t n_new_FP = mStats.mFP - mStatsPrevious.mFP;
+    mStatsPrevious = mStats;
+    char buf[200];
+    SprintfLiteral(buf,
+                   "LUL frame stats: TOTAL %5u"
+                   "    CTX %4u    CFI %4u    FP %4u",
+                   n_new, n_new_Context, n_new_CFI, n_new_FP);
+    buf[sizeof(buf) - 1] = 0;
+    mLog(buf);
+  }
+}
+
+size_t LUL::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+  size_t n = aMallocSizeOf(this);
+  n += mPriMap->SizeOfIncludingThis(aMallocSizeOf);
+
+  // Measurement of the following members may be added later if DMD finds it
+  // is worthwhile:
+  // - mSegArray
+  // - mUSU
+
+  return n;
+}
+
+void LUL::EnableUnwinding() {
+  LUL_LOG("LUL::EnableUnwinding");
+  // Don't assert for Admin mode here.  That is, tolerate a call here
+  // if we are already in Unwinding mode.
+  MOZ_RELEASE_ASSERT(profiler_current_thread_id() == mAdminThreadId);
+
+  mAdminMode = false;
+}
+
+void LUL::NotifyAfterMap(uintptr_t aRXavma, size_t aSize, const char* aFileName,
+                         const void* aMappedImage) {
+  MOZ_RELEASE_ASSERT(mAdminMode);
+  MOZ_RELEASE_ASSERT(profiler_current_thread_id() == mAdminThreadId);
+
+  mLog(":\n");
+  char buf[200];
+  SprintfLiteral(buf, "NotifyMap %llx %llu %s\n",
+                 (unsigned long long int)aRXavma, (unsigned long long int)aSize,
+                 aFileName);
+  buf[sizeof(buf) - 1] = 0;
+  mLog(buf);
+
+  // Ignore obviously-stupid notifications.
+  if (aSize > 0) {
+    // Here's a new mapping, for this object.
+    mozilla::UniquePtr<SecMap> smap = mozilla::MakeUnique<SecMap>(mLog);
+
+    // Read CFI or EXIDX unwind data into |smap|.
+    if (!aMappedImage) {
+      (void)lul::ReadSymbolData(string(aFileName), std::vector<string>(),
+                                smap.get(), (void*)aRXavma, aSize, mUSU, mLog);
+    } else {
+      (void)lul::ReadSymbolDataInternal(
+          (const uint8_t*)aMappedImage, string(aFileName),
+          std::vector<string>(), smap.get(), (void*)aRXavma, aSize, mUSU, mLog);
+    }
+
+    mLog("NotifyMap .. preparing entries\n");
+
+    smap->PrepareRuleSets(aRXavma, aSize);
+
+    SprintfLiteral(buf, "NotifyMap got %lld entries\n",
+                   (long long int)smap->Size());
+    buf[sizeof(buf) - 1] = 0;
+    mLog(buf);
+
+    // Add it to the primary map (the top level set of mapped objects).
+    mPriMap->AddSecMap(std::move(smap));
+
+    // Tell the segment array about the mapping, so that the stack
+    // scan and __kernel_syscall mechanisms know where valid code is.
+    mSegArray->add(aRXavma, aRXavma + aSize - 1, true);
+  }
+}
+
+void LUL::NotifyExecutableArea(uintptr_t aRXavma, size_t aSize) {
+  MOZ_RELEASE_ASSERT(mAdminMode);
+  MOZ_RELEASE_ASSERT(profiler_current_thread_id() == mAdminThreadId);
+
+  mLog(":\n");
+  char buf[200];
+  SprintfLiteral(buf, "NotifyExecutableArea %llx %llu\n",
+                 (unsigned long long int)aRXavma,
+                 (unsigned long long int)aSize);
+  buf[sizeof(buf) - 1] = 0;
+  mLog(buf);
+
+  // Ignore obviously-stupid notifications.
+  if (aSize > 0) {
+    // Tell the segment array about the mapping, so that the stack
+    // scan and __kernel_syscall mechanisms know where valid code is.
+    mSegArray->add(aRXavma, aRXavma + aSize - 1, true);
+  }
+}
+
+void LUL::NotifyBeforeUnmap(uintptr_t aRXavmaMin, uintptr_t aRXavmaMax) {
+  MOZ_RELEASE_ASSERT(mAdminMode);
+  MOZ_RELEASE_ASSERT(profiler_current_thread_id() == mAdminThreadId);
+
+  mLog(":\n");
+  char buf[100];
+  SprintfLiteral(buf, "NotifyUnmap %016llx-%016llx\n",
+                 (unsigned long long int)aRXavmaMin,
+                 (unsigned long long int)aRXavmaMax);
+  buf[sizeof(buf) - 1] = 0;
+  mLog(buf);
+
+  MOZ_ASSERT(aRXavmaMin <= aRXavmaMax);
+
+  // Remove from the primary map, any secondary maps that intersect
+  // with the address range.  Also delete the secondary maps.
+  mPriMap->RemoveSecMapsInRange(aRXavmaMin, aRXavmaMax);
+
+  // Tell the segment array that the address range no longer
+  // contains valid code.
+  mSegArray->add(aRXavmaMin, aRXavmaMax, false);
+
+  SprintfLiteral(buf, "NotifyUnmap: now have %d SecMaps\n",
+                 (int)mPriMap->CountSecMaps());
+  buf[sizeof(buf) - 1] = 0;
+  mLog(buf);
+}
+
+size_t LUL::CountMappings() {
+  MOZ_RELEASE_ASSERT(mAdminMode);
+  MOZ_RELEASE_ASSERT(profiler_current_thread_id() == mAdminThreadId);
+
+  return mPriMap->CountSecMaps();
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+static TaggedUWord DerefTUW(TaggedUWord aAddr, const StackImage* aStackImg) {
+  if (!aAddr.Valid()) {
+    return TaggedUWord();
+  }
+
+  // Lower limit check.  |aAddr.Value()| is the lowest requested address
+  // and |aStackImg->mStartAvma| is the lowest address we actually have,
+  // so the comparison is straightforward.
+  if (aAddr.Value() < aStackImg->mStartAvma) {
+    return TaggedUWord();
+  }
+
+  // Upper limit check.  We must compute the highest requested address
+  // and the highest address we actually have, but being careful to
+  // avoid overflow.  In particular if |aAddr| is 0xFFF...FFF or the
+  // 3/7 values below that, then we will get overflow.  See bug #1245477.
+  typedef CheckedInt<uintptr_t> CheckedUWord;
+  CheckedUWord highest_requested_plus_one =
+      CheckedUWord(aAddr.Value()) + CheckedUWord(sizeof(uintptr_t));
+  CheckedUWord highest_available_plus_one =
+      CheckedUWord(aStackImg->mStartAvma) + CheckedUWord(aStackImg->mLen);
+  if (!highest_requested_plus_one.isValid()     // overflow?
+      || !highest_available_plus_one.isValid()  // overflow?
+      || (highest_requested_plus_one.value() >
+          highest_available_plus_one.value())) {  // in range?
+    return TaggedUWord();
+  }
+
+  return TaggedUWord(
+      *(uintptr_t*)(&aStackImg
+                         ->mContents[aAddr.Value() - aStackImg->mStartAvma]));
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+static TaggedUWord EvaluateReg(int16_t aReg, const UnwindRegs* aOldRegs,
+                               TaggedUWord aCFA) {
+  switch (aReg) {
+    case DW_REG_CFA:
+      return aCFA;
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+    case DW_REG_INTEL_XBP:
+      return aOldRegs->xbp;
+    case DW_REG_INTEL_XSP:
+      return aOldRegs->xsp;
+    case DW_REG_INTEL_XIP:
+      return aOldRegs->xip;
+#elif defined(GP_ARCH_arm)
+    case DW_REG_ARM_R7:
+      return aOldRegs->r7;
+    case DW_REG_ARM_R11:
+      return aOldRegs->r11;
+    case DW_REG_ARM_R12:
+      return aOldRegs->r12;
+    case DW_REG_ARM_R13:
+      return aOldRegs->r13;
+    case DW_REG_ARM_R14:
+      return aOldRegs->r14;
+    case DW_REG_ARM_R15:
+      return aOldRegs->r15;
+#elif defined(GP_ARCH_arm64)
+    case DW_REG_AARCH64_X29:
+      return aOldRegs->x29;
+    case DW_REG_AARCH64_X30:
+      return aOldRegs->x30;
+    case DW_REG_AARCH64_SP:
+      return aOldRegs->sp;
+#elif defined(GP_ARCH_mips64)
+    case DW_REG_MIPS_SP:
+      return aOldRegs->sp;
+    case DW_REG_MIPS_FP:
+      return aOldRegs->fp;
+    case DW_REG_MIPS_PC:
+      return aOldRegs->pc;
+#else
+#  error "Unsupported arch"
+#endif
+    default:
+      MOZ_ASSERT(0);
+      return TaggedUWord();
+  }
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+// See prototype for comment.
+TaggedUWord EvaluatePfxExpr(int32_t start, const UnwindRegs* aOldRegs,
+                            TaggedUWord aCFA, const StackImage* aStackImg,
+                            const vector<PfxInstr>& aPfxInstrs) {
+  // A small evaluation stack, and a stack pointer, which points to
+  // the highest numbered in-use element.
+  const int N_STACK = 10;
+  TaggedUWord stack[N_STACK];
+  int stackPointer = -1;
+  for (int i = 0; i < N_STACK; i++) stack[i] = TaggedUWord();
+
+#define PUSH(_tuw)                                             \
+  do {                                                         \
+    if (stackPointer >= N_STACK - 1) goto fail; /* overflow */ \
+    stack[++stackPointer] = (_tuw);                            \
+  } while (0)
+
+#define POP(_lval)                                   \
+  do {                                               \
+    if (stackPointer < 0) goto fail; /* underflow */ \
+    _lval = stack[stackPointer--];                   \
+  } while (0)
+
+  // Cursor in the instruction sequence.
+  size_t curr = start + 1;
+
+  // Check the start point is sane.
+  size_t nInstrs = aPfxInstrs.size();
+  if (start < 0 || (size_t)start >= nInstrs) goto fail;
+
+  {
+    // The instruction sequence must start with PX_Start.  If not,
+    // something is seriously wrong.
+    PfxInstr first = aPfxInstrs[start];
+    if (first.mOpcode != PX_Start) goto fail;
+
+    // Push the CFA on the stack to start with (or not), as required by
+    // the original DW_OP_*expression* CFI.
+    if (first.mOperand != 0) PUSH(aCFA);
+  }
+
+  while (true) {
+    if (curr >= nInstrs) goto fail;  // ran off the end of the sequence
+
+    PfxInstr pfxi = aPfxInstrs[curr++];
+    if (pfxi.mOpcode == PX_End) break;  // we're done
+
+    switch (pfxi.mOpcode) {
+      case PX_Start:
+        // This should appear only at the start of the sequence.
+        goto fail;
+      case PX_End:
+        // We just took care of that, so we shouldn't see it again.
+        MOZ_ASSERT(0);
+        goto fail;
+      case PX_SImm32:
+        PUSH(TaggedUWord((intptr_t)pfxi.mOperand));
+        break;
+      case PX_DwReg: {
+        DW_REG_NUMBER reg = (DW_REG_NUMBER)pfxi.mOperand;
+        MOZ_ASSERT(reg != DW_REG_CFA);
+        PUSH(EvaluateReg(reg, aOldRegs, aCFA));
+        break;
+      }
+      case PX_Deref: {
+        TaggedUWord addr;
+        POP(addr);
+        PUSH(DerefTUW(addr, aStackImg));
+        break;
+      }
+      case PX_Add: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y + x);
+        break;
+      }
+      case PX_Sub: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y - x);
+        break;
+      }
+      case PX_And: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y & x);
+        break;
+      }
+      case PX_Or: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y | x);
+        break;
+      }
+      case PX_CmpGES: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y.CmpGEs(x));
+        break;
+      }
+      case PX_Shl: {
+        TaggedUWord x, y;
+        POP(x);
+        POP(y);
+        PUSH(y << x);
+        break;
+      }
+      default:
+        MOZ_ASSERT(0);
+        goto fail;
+    }
+  }  // while (true)
+
+  // Evaluation finished.  The top value on the stack is the result.
+  if (stackPointer >= 0) {
+    return stack[stackPointer];
+  }
+  // Else fall through
+
+fail:
+  return TaggedUWord();
+
+#undef PUSH
+#undef POP
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+TaggedUWord LExpr::EvaluateExpr(const UnwindRegs* aOldRegs, TaggedUWord aCFA,
+                                const StackImage* aStackImg,
+                                const vector<PfxInstr>* aPfxInstrs) const {
+  switch (mHow) {
+    case UNKNOWN:
+      return TaggedUWord();
+    case NODEREF: {
+      TaggedUWord tuw = EvaluateReg(mReg, aOldRegs, aCFA);
+      tuw = tuw + TaggedUWord((intptr_t)mOffset);
+      return tuw;
+    }
+    case DEREF: {
+      TaggedUWord tuw = EvaluateReg(mReg, aOldRegs, aCFA);
+      tuw = tuw + TaggedUWord((intptr_t)mOffset);
+      return DerefTUW(tuw, aStackImg);
+    }
+    case PFXEXPR: {
+      MOZ_ASSERT(aPfxInstrs);
+      if (!aPfxInstrs) {
+        return TaggedUWord();
+      }
+      return EvaluatePfxExpr(mOffset, aOldRegs, aCFA, aStackImg, *aPfxInstrs);
+    }
+    default:
+      MOZ_ASSERT(0);
+      return TaggedUWord();
+  }
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+static void UseRuleSet(/*MOD*/ UnwindRegs* aRegs, const StackImage* aStackImg,
+                       const RuleSet* aRS, const vector<PfxInstr>* aPfxInstrs) {
+  // Take a copy of regs, since we'll need to refer to the old values
+  // whilst computing the new ones.
+  UnwindRegs old_regs = *aRegs;
+
+  // Mark all the current register values as invalid, so that the
+  // caller can see, on our return, which ones have been computed
+  // anew.  If we don't even manage to compute a new PC value, then
+  // the caller will have to abandon the unwind.
+  // FIXME: Create and use instead: aRegs->SetAllInvalid();
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+  aRegs->xbp = TaggedUWord();
+  aRegs->xsp = TaggedUWord();
+  aRegs->xip = TaggedUWord();
+#elif defined(GP_ARCH_arm)
+  aRegs->r7 = TaggedUWord();
+  aRegs->r11 = TaggedUWord();
+  aRegs->r12 = TaggedUWord();
+  aRegs->r13 = TaggedUWord();
+  aRegs->r14 = TaggedUWord();
+  aRegs->r15 = TaggedUWord();
+#elif defined(GP_ARCH_arm64)
+  aRegs->x29 = TaggedUWord();
+  aRegs->x30 = TaggedUWord();
+  aRegs->sp = TaggedUWord();
+  aRegs->pc = TaggedUWord();
+#elif defined(GP_ARCH_mips64)
+  aRegs->sp = TaggedUWord();
+  aRegs->fp = TaggedUWord();
+  aRegs->pc = TaggedUWord();
+#else
+#  error "Unsupported arch"
+#endif
+
+  // This is generally useful.
+  const TaggedUWord inval = TaggedUWord();
+
+  // First, compute the CFA.
+  TaggedUWord cfa = aRS->mCfaExpr.EvaluateExpr(&old_regs, inval /*old cfa*/,
+                                               aStackImg, aPfxInstrs);
+
+  // If we didn't manage to compute the CFA, well .. that's ungood,
+  // but keep going anyway.  It'll be OK provided none of the register
+  // value rules mention the CFA.  In any case, compute the new values
+  // for each register that we're tracking.
+
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+  aRegs->xbp =
+      aRS->mXbpExpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->xsp =
+      aRS->mXspExpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->xip =
+      aRS->mXipExpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+#elif defined(GP_ARCH_arm)
+  aRegs->r7 = aRS->mR7expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->r11 =
+      aRS->mR11expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->r12 =
+      aRS->mR12expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->r13 =
+      aRS->mR13expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->r14 =
+      aRS->mR14expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->r15 =
+      aRS->mR15expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+#elif defined(GP_ARCH_arm64)
+  aRegs->x29 =
+      aRS->mX29expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->x30 =
+      aRS->mX30expr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->sp = aRS->mSPexpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+#elif defined(GP_ARCH_mips64)
+  aRegs->sp = aRS->mSPexpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->fp = aRS->mFPexpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+  aRegs->pc = aRS->mPCexpr.EvaluateExpr(&old_regs, cfa, aStackImg, aPfxInstrs);
+#else
+#  error "Unsupported arch"
+#endif
+
+  // We're done.  Any regs for which we didn't manage to compute a
+  // new value will now be marked as invalid.
+}
+
+// RUNS IN NO-MALLOC CONTEXT
+void LUL::Unwind(/*OUT*/ uintptr_t* aFramePCs,
+                 /*OUT*/ uintptr_t* aFrameSPs,
+                 /*OUT*/ size_t* aFramesUsed,
+                 /*OUT*/ size_t* aFramePointerFramesAcquired,
+                 size_t aFramesAvail, UnwindRegs* aStartRegs,
+                 StackImage* aStackImg) {
+  MOZ_RELEASE_ASSERT(!mAdminMode);
+
+  /////////////////////////////////////////////////////////
+  // BEGIN UNWIND
+
+  *aFramesUsed = 0;
+
+  UnwindRegs regs = *aStartRegs;
+  TaggedUWord last_valid_sp = TaggedUWord();
+
+  while (true) {
+    if (DEBUG_MAIN) {
+      char buf[300];
+      mLog("\n");
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+      SprintfLiteral(
+          buf, "LoopTop: rip %d/%llx  rsp %d/%llx  rbp %d/%llx\n",
+          (int)regs.xip.Valid(), (unsigned long long int)regs.xip.Value(),
+          (int)regs.xsp.Valid(), (unsigned long long int)regs.xsp.Value(),
+          (int)regs.xbp.Valid(), (unsigned long long int)regs.xbp.Value());
+      buf[sizeof(buf) - 1] = 0;
+      mLog(buf);
+#elif defined(GP_ARCH_arm)
+      SprintfLiteral(
+          buf,
+          "LoopTop: r15 %d/%llx  r7 %d/%llx  r11 %d/%llx"
+          "  r12 %d/%llx  r13 %d/%llx  r14 %d/%llx\n",
+          (int)regs.r15.Valid(), (unsigned long long int)regs.r15.Value(),
+          (int)regs.r7.Valid(), (unsigned long long int)regs.r7.Value(),
+          (int)regs.r11.Valid(), (unsigned long long int)regs.r11.Value(),
+          (int)regs.r12.Valid(), (unsigned long long int)regs.r12.Value(),
+          (int)regs.r13.Valid(), (unsigned long long int)regs.r13.Value(),
+          (int)regs.r14.Valid(), (unsigned long long int)regs.r14.Value());
+      buf[sizeof(buf) - 1] = 0;
+      mLog(buf);
+#elif defined(GP_ARCH_arm64)
+      SprintfLiteral(
+          buf,
+          "LoopTop: pc %d/%llx  x29 %d/%llx  x30 %d/%llx"
+          "  sp %d/%llx\n",
+          (int)regs.pc.Valid(), (unsigned long long int)regs.pc.Value(),
+          (int)regs.x29.Valid(), (unsigned long long int)regs.x29.Value(),
+          (int)regs.x30.Valid(), (unsigned long long int)regs.x30.Value(),
+          (int)regs.sp.Valid(), (unsigned long long int)regs.sp.Value());
+      buf[sizeof(buf) - 1] = 0;
+      mLog(buf);
+#elif defined(GP_ARCH_mips64)
+      SprintfLiteral(
+          buf, "LoopTop: pc %d/%llx  sp %d/%llx  fp %d/%llx\n",
+          (int)regs.pc.Valid(), (unsigned long long int)regs.pc.Value(),
+          (int)regs.sp.Valid(), (unsigned long long int)regs.sp.Value(),
+          (int)regs.fp.Valid(), (unsigned long long int)regs.fp.Value());
+      buf[sizeof(buf) - 1] = 0;
+      mLog(buf);
+#else
+#  error "Unsupported arch"
+#endif
+    }
+
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+    TaggedUWord ia = regs.xip;
+    TaggedUWord sp = regs.xsp;
+#elif defined(GP_ARCH_arm)
+    TaggedUWord ia = (*aFramesUsed == 0 ? regs.r15 : regs.r14);
+    TaggedUWord sp = regs.r13;
+#elif defined(GP_ARCH_arm64)
+    TaggedUWord ia = (*aFramesUsed == 0 ? regs.pc : regs.x30);
+    TaggedUWord sp = regs.sp;
+#elif defined(GP_ARCH_mips64)
+    TaggedUWord ia = regs.pc;
+    TaggedUWord sp = regs.sp;
+#else
+#  error "Unsupported arch"
+#endif
+
+    if (*aFramesUsed >= aFramesAvail) {
+      break;
+    }
+
+    // If we don't have a valid value for the PC, give up.
+    if (!ia.Valid()) {
+      break;
+    }
+
+    // If this is the innermost frame, record the SP value, which
+    // presumably is valid.  If this isn't the innermost frame, and we
+    // have a valid SP value, check that its SP value isn't less that
+    // the one we've seen so far, so as to catch potential SP value
+    // cycles.
+    if (*aFramesUsed == 0) {
+      last_valid_sp = sp;
+    } else {
+      MOZ_ASSERT(last_valid_sp.Valid());
+      if (sp.Valid()) {
+        if (sp.Value() < last_valid_sp.Value()) {
+          // Hmm, SP going in the wrong direction.  Let's stop.
+          break;
+        }
+        // Remember where we got to.
+        last_valid_sp = sp;
+      }
+    }
+
+    // For the innermost frame, the IA value is what we need.  For all
+    // other frames, it's actually the return address, so back up one
+    // byte so as to get it into the calling instruction.
+    aFramePCs[*aFramesUsed] = ia.Value() - (*aFramesUsed == 0 ? 0 : 1);
+    aFrameSPs[*aFramesUsed] = sp.Valid() ? sp.Value() : 0;
+    (*aFramesUsed)++;
+
+    // Find the RuleSet for the current IA, if any.  This will also
+    // query the backing (secondary) maps if it isn't found in the
+    // thread-local cache.
+
+    // If this isn't the innermost frame, back up into the calling insn.
+    if (*aFramesUsed > 1) {
+      ia = ia + TaggedUWord((uintptr_t)(-1));
+    }
+
+    pair<const RuleSet*, const vector<PfxInstr>*> ruleset_and_pfxinstrs =
+        mPriMap->Lookup(ia.Value());
+    const RuleSet* ruleset = ruleset_and_pfxinstrs.first;
+    const vector<PfxInstr>* pfxinstrs = ruleset_and_pfxinstrs.second;
+
+    if (DEBUG_MAIN) {
+      char buf[100];
+      SprintfLiteral(buf, "ruleset for 0x%llx = %p\n",
+                     (unsigned long long int)ia.Value(), ruleset);
+      buf[sizeof(buf) - 1] = 0;
+      mLog(buf);
+    }
+
+#if defined(GP_PLAT_x86_android) || defined(GP_PLAT_x86_linux)
+    /////////////////////////////////////////////
+    ////
+    // On 32 bit x86-linux, syscalls are often done via the VDSO
+    // function __kernel_vsyscall, which doesn't have a corresponding
+    // object that we can read debuginfo from.  That effectively kills
+    // off all stack traces for threads blocked in syscalls.  Hence
+    // special-case by looking at the code surrounding the program
+    // counter.
+    //
+    // 0xf7757420 <__kernel_vsyscall+0>:	push   %ecx
+    // 0xf7757421 <__kernel_vsyscall+1>:	push   %edx
+    // 0xf7757422 <__kernel_vsyscall+2>:	push   %ebp
+    // 0xf7757423 <__kernel_vsyscall+3>:	mov    %esp,%ebp
+    // 0xf7757425 <__kernel_vsyscall+5>:	sysenter
+    // 0xf7757427 <__kernel_vsyscall+7>:	nop
+    // 0xf7757428 <__kernel_vsyscall+8>:	nop
+    // 0xf7757429 <__kernel_vsyscall+9>:	nop
+    // 0xf775742a <__kernel_vsyscall+10>:	nop
+    // 0xf775742b <__kernel_vsyscall+11>:	nop
+    // 0xf775742c <__kernel_vsyscall+12>:	nop
+    // 0xf775742d <__kernel_vsyscall+13>:	nop
+    // 0xf775742e <__kernel_vsyscall+14>:	int    $0x80
+    // 0xf7757430 <__kernel_vsyscall+16>:	pop    %ebp
+    // 0xf7757431 <__kernel_vsyscall+17>:	pop    %edx
+    // 0xf7757432 <__kernel_vsyscall+18>:	pop    %ecx
+    // 0xf7757433 <__kernel_vsyscall+19>:	ret
+    //
+    // In cases where the sampled thread is blocked in a syscall, its
+    // program counter will point at "pop %ebp".  Hence we look for
+    // the sequence "int $0x80; pop %ebp; pop %edx; pop %ecx; ret", and
+    // the corresponding register-recovery actions are:
+    //    new_ebp = *(old_esp + 0)
+    //    new eip = *(old_esp + 12)
+    //    new_esp = old_esp + 16
+    //
+    // It may also be the case that the program counter points two
+    // nops before the "int $0x80", viz, is __kernel_vsyscall+12, in
+    // the case where the syscall has been restarted but the thread
+    // hasn't been rescheduled.  The code below doesn't handle that;
+    // it could easily be made to.
+    //
+    if (!ruleset && *aFramesUsed == 1 && ia.Valid() && sp.Valid()) {
+      uintptr_t insns_min, insns_max;
+      uintptr_t eip = ia.Value();
+      bool b = mSegArray->getBoundingCodeSegment(&insns_min, &insns_max, eip);
+      if (b && eip - 2 >= insns_min && eip + 3 <= insns_max) {
+        uint8_t* eipC = (uint8_t*)eip;
+        if (eipC[-2] == 0xCD && eipC[-1] == 0x80 && eipC[0] == 0x5D &&
+            eipC[1] == 0x5A && eipC[2] == 0x59 && eipC[3] == 0xC3) {
+          TaggedUWord sp_plus_0 = sp;
+          TaggedUWord sp_plus_12 = sp;
+          TaggedUWord sp_plus_16 = sp;
+          sp_plus_12 = sp_plus_12 + TaggedUWord(12);
+          sp_plus_16 = sp_plus_16 + TaggedUWord(16);
+          TaggedUWord new_ebp = DerefTUW(sp_plus_0, aStackImg);
+          TaggedUWord new_eip = DerefTUW(sp_plus_12, aStackImg);
+          TaggedUWord new_esp = sp_plus_16;
+          if (new_ebp.Valid() && new_eip.Valid() && new_esp.Valid()) {
+            regs.xbp = new_ebp;
+            regs.xip = new_eip;
+            regs.xsp = new_esp;
+            continue;
+          }
+        }
+      }
+    }
+    ////
+    /////////////////////////////////////////////
+#endif  // defined(GP_PLAT_x86_android) || defined(GP_PLAT_x86_linux)
+
+    // So, do we have a ruleset for this address?  If so, use it now.
+    if (ruleset) {
+      if (DEBUG_MAIN) {
+        ruleset->Print(mLog);
+        mLog("\n");
+      }
+      // Use the RuleSet to compute the registers for the previous
+      // frame.  |regs| is modified in-place.
+      UseRuleSet(&regs, aStackImg, ruleset, pfxinstrs);
+      continue;
+    }
+
+#if defined(GP_PLAT_amd64_linux) || defined(GP_PLAT_x86_linux) ||     \
+    defined(GP_PLAT_amd64_android) || defined(GP_PLAT_x86_android) || \
+    defined(GP_PLAT_amd64_freebsd)
+    // There's no RuleSet for the specified address.  On amd64/x86_linux, see if
+    // it's possible to recover the caller's frame by using the frame pointer.
+
+    // We seek to compute (new_IP, new_SP, new_BP) from (old_BP, stack image),
+    // and assume the following layout:
+    //
+    //                 <--- new_SP
+    //   +----------+
+    //   |  new_IP  |  (return address)
+    //   +----------+
+    //   |  new_BP  |  <--- old_BP
+    //   +----------+
+    //   |   ....   |
+    //   |   ....   |
+    //   |   ....   |
+    //   +----------+  <---- old_SP (arbitrary, but must be <= old_BP)
+
+    const size_t wordSzB = sizeof(uintptr_t);
+    TaggedUWord old_xsp = regs.xsp;
+
+    // points at new_BP ?
+    TaggedUWord old_xbp = regs.xbp;
+    // points at new_IP ?
+    TaggedUWord old_xbp_plus1 = regs.xbp + TaggedUWord(1 * wordSzB);
+    // is the new_SP ?
+    TaggedUWord old_xbp_plus2 = regs.xbp + TaggedUWord(2 * wordSzB);
+
+    if (old_xbp.Valid() && old_xbp.IsAligned() && old_xsp.Valid() &&
+        old_xsp.IsAligned() && old_xsp.Value() <= old_xbp.Value()) {
+      // We don't need to do any range, alignment or validity checks for
+      // addresses passed to DerefTUW, since that performs them itself, and
+      // returns an invalid value on failure.  Any such value will poison
+      // subsequent uses, and we do a final check for validity before putting
+      // the computed values into |regs|.
+      TaggedUWord new_xbp = DerefTUW(old_xbp, aStackImg);
+      if (new_xbp.Valid() && new_xbp.IsAligned() &&
+          old_xbp.Value() < new_xbp.Value()) {
+        TaggedUWord new_xip = DerefTUW(old_xbp_plus1, aStackImg);
+        TaggedUWord new_xsp = old_xbp_plus2;
+        if (new_xbp.Valid() && new_xip.Valid() && new_xsp.Valid()) {
+          regs.xbp = new_xbp;
+          regs.xip = new_xip;
+          regs.xsp = new_xsp;
+          (*aFramePointerFramesAcquired)++;
+          continue;
+        }
+      }
+    }
+#elif defined(GP_ARCH_arm64)
+    // Here is an example of generated code for prologue and epilogue..
+    //
+    // stp     x29, x30, [sp, #-16]!
+    // mov     x29, sp
+    // ...
+    // ldp     x29, x30, [sp], #16
+    // ret
+    //
+    // Next is another example of generated code.
+    //
+    // stp     x20, x19, [sp, #-32]!
+    // stp     x29, x30, [sp, #16]
+    // add     x29, sp, #0x10
+    // ...
+    // ldp     x29, x30, [sp, #16]
+    // ldp     x20, x19, [sp], #32
+    // ret
+    //
+    // Previous x29 and x30 register are stored in the address of x29 register.
+    // But since sp register value depends on local variables, we cannot compute
+    // previous sp register from current sp/fp/lr register and there is no
+    // regular rule for sp register in prologue. But since return address is lr
+    // register, if x29 is valid, we will get return address without sp
+    // register.
+    //
+    // So we assume the following layout that if no rule set. x29 is frame
+    // pointer, so we will be able to compute x29 and x30 .
+    //
+    //   +----------+  <--- new_sp (cannot compute)
+    //   |   ....   |
+    //   +----------+
+    //   |  new_lr  |  (return address)
+    //   +----------+
+    //   |  new_fp  |  <--- old_fp
+    //   +----------+
+    //   |   ....   |
+    //   |   ....   |
+    //   +----------+  <---- old_sp (arbitrary, but unused)
+
+    TaggedUWord old_fp = regs.x29;
+    if (old_fp.Valid() && old_fp.IsAligned() && last_valid_sp.Valid() &&
+        last_valid_sp.Value() <= old_fp.Value()) {
+      TaggedUWord new_fp = DerefTUW(old_fp, aStackImg);
+      if (new_fp.Valid() && new_fp.IsAligned() &&
+          old_fp.Value() < new_fp.Value()) {
+        TaggedUWord old_fp_plus1 = old_fp + TaggedUWord(8);
+        TaggedUWord new_lr = DerefTUW(old_fp_plus1, aStackImg);
+        if (new_lr.Valid()) {
+          regs.x29 = new_fp;
+          regs.x30 = new_lr;
+          // When using frame pointer to walk stack, we cannot compute sp
+          // register since we cannot compute sp register from fp/lr/sp
+          // register, and there is no regular rule to compute previous sp
+          // register. So mark as invalid.
+          regs.sp = TaggedUWord();
+          (*aFramePointerFramesAcquired)++;
+          continue;
+        }
+      }
+    }
+#endif  // defined(GP_PLAT_amd64_linux) || defined(GP_PLAT_x86_linux) ||
+        // defined(GP_PLAT_amd64_android) || defined(GP_PLAT_x86_android)
+
+    // We failed to recover a frame either using CFI or FP chasing, and we
+    // have no other ways to recover the frame.  So we have to give up.
+    break;
+
+  }  // top level unwind loop
+
+  // END UNWIND
+  /////////////////////////////////////////////////////////
+}
+
+////////////////////////////////////////////////////////////////
+// LUL Unit Testing                                           //
+////////////////////////////////////////////////////////////////
+
+static const int LUL_UNIT_TEST_STACK_SIZE = 32768;
+
+#if defined(GP_ARCH_mips64)
+static __attribute__((noinline)) unsigned long __getpc(void) {
+  unsigned long rtaddr;
+  __asm__ volatile("move %0, $31" : "=r"(rtaddr));
+  return rtaddr;
+}
+#endif
+
+// This function is innermost in the test call sequence.  It uses LUL
+// to unwind, and compares the result with the sequence specified in
+// the director string.  These need to agree in order for the test to
+// pass.  In order not to screw up the results, this function needs
+// to have a not-very big stack frame, since we're only presenting
+// the innermost LUL_UNIT_TEST_STACK_SIZE bytes of stack to LUL, and
+// that chunk unavoidably includes the frame for this function.
+//
+// This function must not be inlined into its callers.  Doing so will
+// cause the expected-vs-actual backtrace consistency checking to
+// fail.  Prints summary results to |aLUL|'s logging sink and also
+// returns a boolean indicating whether or not the test failed.
+static __attribute__((noinline)) bool GetAndCheckStackTrace(
+    LUL* aLUL, const char* dstring) {
+  // Get hold of the current unwind-start registers.
+  UnwindRegs startRegs;
+  memset(&startRegs, 0, sizeof(startRegs));
+#if defined(GP_ARCH_amd64)
+  volatile uintptr_t block[3];
+  MOZ_ASSERT(sizeof(block) == 24);
+  __asm__ __volatile__(
+      "leaq 0(%%rip), %%r15"
+      "\n\t"
+      "movq %%r15, 0(%0)"
+      "\n\t"
+      "movq %%rsp, 8(%0)"
+      "\n\t"
+      "movq %%rbp, 16(%0)"
+      "\n"
+      :
+      : "r"(&block[0])
+      : "memory", "r15");
+  startRegs.xip = TaggedUWord(block[0]);
+  startRegs.xsp = TaggedUWord(block[1]);
+  startRegs.xbp = TaggedUWord(block[2]);
+  const uintptr_t REDZONE_SIZE = 128;
+  uintptr_t start = block[1] - REDZONE_SIZE;
+#elif defined(GP_PLAT_x86_linux) || defined(GP_PLAT_x86_android)
+  volatile uintptr_t block[3];
+  MOZ_ASSERT(sizeof(block) == 12);
+  __asm__ __volatile__(
+      ".byte 0xE8,0x00,0x00,0x00,0x00" /*call next insn*/
+      "\n\t"
+      "popl %%edi"
+      "\n\t"
+      "movl %%edi, 0(%0)"
+      "\n\t"
+      "movl %%esp, 4(%0)"
+      "\n\t"
+      "movl %%ebp, 8(%0)"
+      "\n"
+      :
+      : "r"(&block[0])
+      : "memory", "edi");
+  startRegs.xip = TaggedUWord(block[0]);
+  startRegs.xsp = TaggedUWord(block[1]);
+  startRegs.xbp = TaggedUWord(block[2]);
+  const uintptr_t REDZONE_SIZE = 0;
+  uintptr_t start = block[1] - REDZONE_SIZE;
+#elif defined(GP_PLAT_arm_linux) || defined(GP_PLAT_arm_android)
+  volatile uintptr_t block[6];
+  MOZ_ASSERT(sizeof(block) == 24);
+  __asm__ __volatile__(
+      "mov r0, r15"
+      "\n\t"
+      "str r0,  [%0, #0]"
+      "\n\t"
+      "str r14, [%0, #4]"
+      "\n\t"
+      "str r13, [%0, #8]"
+      "\n\t"
+      "str r12, [%0, #12]"
+      "\n\t"
+      "str r11, [%0, #16]"
+      "\n\t"
+      "str r7,  [%0, #20]"
+      "\n"
+      :
+      : "r"(&block[0])
+      : "memory", "r0");
+  startRegs.r15 = TaggedUWord(block[0]);
+  startRegs.r14 = TaggedUWord(block[1]);
+  startRegs.r13 = TaggedUWord(block[2]);
+  startRegs.r12 = TaggedUWord(block[3]);
+  startRegs.r11 = TaggedUWord(block[4]);
+  startRegs.r7 = TaggedUWord(block[5]);
+  const uintptr_t REDZONE_SIZE = 0;
+  uintptr_t start = block[1] - REDZONE_SIZE;
+#elif defined(GP_ARCH_arm64)
+  volatile uintptr_t block[4];
+  MOZ_ASSERT(sizeof(block) == 32);
+  __asm__ __volatile__(
+      "adr x0, . \n\t"
+      "str x0, [%0, #0] \n\t"
+      "str x29, [%0, #8] \n\t"
+      "str x30, [%0, #16] \n\t"
+      "mov x0, sp \n\t"
+      "str x0, [%0, #24] \n\t"
+      :
+      : "r"(&block[0])
+      : "memory", "x0");
+  startRegs.pc = TaggedUWord(block[0]);
+  startRegs.x29 = TaggedUWord(block[1]);
+  startRegs.x30 = TaggedUWord(block[2]);
+  startRegs.sp = TaggedUWord(block[3]);
+  const uintptr_t REDZONE_SIZE = 0;
+  uintptr_t start = block[1] - REDZONE_SIZE;
+#elif defined(GP_ARCH_mips64)
+  volatile uintptr_t block[3];
+  MOZ_ASSERT(sizeof(block) == 24);
+  __asm__ __volatile__(
+      "sd $29, 8(%0)     \n"
+      "sd $30, 16(%0)    \n"
+      :
+      : "r"(block)
+      : "memory");
+  block[0] = __getpc();
+  startRegs.pc = TaggedUWord(block[0]);
+  startRegs.sp = TaggedUWord(block[1]);
+  startRegs.fp = TaggedUWord(block[2]);
+  const uintptr_t REDZONE_SIZE = 0;
+  uintptr_t start = block[1] - REDZONE_SIZE;
+#else
+#  error "Unsupported platform"
+#endif
+
+  // Get hold of the innermost LUL_UNIT_TEST_STACK_SIZE bytes of the
+  // stack.
+  uintptr_t end = start + LUL_UNIT_TEST_STACK_SIZE;
+  uintptr_t ws = sizeof(void*);
+  start &= ~(ws - 1);
+  end &= ~(ws - 1);
+  uintptr_t nToCopy = end - start;
+  if (nToCopy > lul::N_STACK_BYTES) {
+    nToCopy = lul::N_STACK_BYTES;
+  }
+  MOZ_ASSERT(nToCopy <= lul::N_STACK_BYTES);
+  StackImage* stackImg = new StackImage();
+  stackImg->mLen = nToCopy;
+  stackImg->mStartAvma = start;
+  if (nToCopy > 0) {
+    MOZ_MAKE_MEM_DEFINED((void*)start, nToCopy);
+    memcpy(&stackImg->mContents[0], (void*)start, nToCopy);
+  }
+
+  // Unwind it.
+  const int MAX_TEST_FRAMES = 64;
+  uintptr_t framePCs[MAX_TEST_FRAMES];
+  uintptr_t frameSPs[MAX_TEST_FRAMES];
+  size_t framesAvail = mozilla::ArrayLength(framePCs);
+  size_t framesUsed = 0;
+  size_t framePointerFramesAcquired = 0;
+  aLUL->Unwind(&framePCs[0], &frameSPs[0], &framesUsed,
+               &framePointerFramesAcquired, framesAvail, &startRegs, stackImg);
+
+  delete stackImg;
+
+  // if (0) {
+  //  // Show what we have.
+  //  fprintf(stderr, "Got %d frames:\n", (int)framesUsed);
+  //  for (size_t i = 0; i < framesUsed; i++) {
+  //    fprintf(stderr, "  [%2d]   SP %p   PC %p\n",
+  //            (int)i, (void*)frameSPs[i], (void*)framePCs[i]);
+  //  }
+  //  fprintf(stderr, "\n");
+  //}
+
+  // Check to see if there's a consistent binding between digits in
+  // the director string ('1' .. '8') and the PC values acquired by
+  // the unwind.  If there isn't, the unwinding has failed somehow.
+  uintptr_t binding[8];  // binding for '1' .. binding for '8'
+  memset((void*)binding, 0, sizeof(binding));
+
+  // The general plan is to work backwards along the director string
+  // and forwards along the framePCs array.  Doing so corresponds to
+  // working outwards from the innermost frame of the recursive test set.
+  const char* cursor = dstring;
+
+  // Find the end.  This leaves |cursor| two bytes past the first
+  // character we want to look at -- see comment below.
+  while (*cursor) cursor++;
+
+  // Counts the number of consistent frames.
+  size_t nConsistent = 0;
+
+  // Iterate back to the start of the director string.  The starting
+  // points are a bit complex.  We can't use framePCs[0] because that
+  // contains the PC in this frame (above).  We can't use framePCs[1]
+  // because that will contain the PC at return point in the recursive
+  // test group (TestFn[1-8]) for their call "out" to this function,
+  // GetAndCheckStackTrace.  Although LUL will compute a correct
+  // return address, that will not be the same return address as for a
+  // recursive call out of the the function to another function in the
+  // group.  Hence we can only start consistency checking at
+  // framePCs[2].
+  //
+  // To be consistent, then, we must ignore the last element in the
+  // director string as that corresponds to framePCs[1].  Hence the
+  // start points are: framePCs[2] and the director string 2 bytes
+  // before the terminating zero.
+  //
+  // Also as a result of this, the number of consistent frames counted
+  // will always be one less than the length of the director string
+  // (not including its terminating zero).
+  size_t frameIx;
+  for (cursor = cursor - 2, frameIx = 2;
+       cursor >= dstring && frameIx < framesUsed; cursor--, frameIx++) {
+    char c = *cursor;
+    uintptr_t pc = framePCs[frameIx];
+    // If this doesn't hold, the director string is ill-formed.
+    MOZ_ASSERT(c >= '1' && c <= '8');
+    int n = ((int)c) - ((int)'1');
+    if (binding[n] == 0) {
+      // There's no binding for |c| yet, so install |pc| and carry on.
+      binding[n] = pc;
+      nConsistent++;
+      continue;
+    }
+    // There's a pre-existing binding for |c|.  Check it's consistent.
+    if (binding[n] != pc) {
+      // Not consistent.  Give up now.
+      break;
+    }
+    // Consistent.  Keep going.
+    nConsistent++;
+  }
+
+  // So, did we succeed?
+  bool passed = nConsistent + 1 == strlen(dstring);
+
+  // Show the results.
+  char buf[200];
+  SprintfLiteral(buf, "LULUnitTest:   dstring = %s\n", dstring);
+  buf[sizeof(buf) - 1] = 0;
+  aLUL->mLog(buf);
+  SprintfLiteral(buf, "LULUnitTest:     %d consistent, %d in dstring: %s\n",
+                 (int)nConsistent, (int)strlen(dstring),
+                 passed ? "PASS" : "FAIL");
+  buf[sizeof(buf) - 1] = 0;
+  aLUL->mLog(buf);
+
+  return !passed;
+}
+
+// Macro magic to create a set of 8 mutually recursive functions with
+// varying frame sizes.  These will recurse amongst themselves as
+// specified by |strP|, the directory string, and call
+// GetAndCheckStackTrace when the string becomes empty, passing it the
+// original value of the string.  This checks the result, printing
+// results on |aLUL|'s logging sink, and also returns a boolean
+// indicating whether or not the results are acceptable (correct).
+
+#define DECL_TEST_FN(NAME) \
+  bool NAME(LUL* aLUL, const char* strPorig, const char* strP);
+
+#define GEN_TEST_FN(NAME, FRAMESIZE)                                          \
+  bool NAME(LUL* aLUL, const char* strPorig, const char* strP) {              \
+    /* Create a frame of size (at least) FRAMESIZE, so that the */            \
+    /* 8 functions created by this macro offer some variation in frame */     \
+    /* sizes.  This isn't as simple as it might seem, since a clever */       \
+    /* optimizing compiler (eg, clang-5) detects that the array is unused */  \
+    /* and removes it.  We try to defeat this by passing it to a function */  \
+    /* in a different compilation unit, and hoping that clang does not */     \
+    /* notice that the call is a no-op. */                                    \
+    char space[FRAMESIZE];                                                    \
+    Unused << write(1, space, 0); /* write zero bytes of |space| to stdout */ \
+                                                                              \
+    if (*strP == '\0') {                                                      \
+      /* We've come to the end of the director string. */                     \
+      /* Take a stack snapshot. */                                            \
+      /* We purposefully use a negation to avoid tail-call optimization */    \
+      return !GetAndCheckStackTrace(aLUL, strPorig);                          \
+    } else {                                                                  \
+      /* Recurse onwards.  This is a bit subtle.  The obvious */              \
+      /* thing to do here is call onwards directly, from within the */        \
+      /* arms of the case statement.  That gives a problem in that */         \
+      /* there will be multiple return points inside each function when */    \
+      /* unwinding, so it will be difficult to check for consistency */       \
+      /* against the director string.  Instead, we make an indirect */        \
+      /* call, so as to guarantee that there is only one call site */         \
+      /* within each function.  This does assume that the compiler */         \
+      /* won't transform it back to the simple direct-call form. */           \
+      /* To discourage it from doing so, the call is bracketed with */        \
+      /* __asm__ __volatile__ sections so as to make it not-movable. */       \
+      bool (*nextFn)(LUL*, const char*, const char*) = NULL;                  \
+      switch (*strP) {                                                        \
+        case '1':                                                             \
+          nextFn = TestFn1;                                                   \
+          break;                                                              \
+        case '2':                                                             \
+          nextFn = TestFn2;                                                   \
+          break;                                                              \
+        case '3':                                                             \
+          nextFn = TestFn3;                                                   \
+          break;                                                              \
+        case '4':                                                             \
+          nextFn = TestFn4;                                                   \
+          break;                                                              \
+        case '5':                                                             \
+          nextFn = TestFn5;                                                   \
+          break;                                                              \
+        case '6':                                                             \
+          nextFn = TestFn6;                                                   \
+          break;                                                              \
+        case '7':                                                             \
+          nextFn = TestFn7;                                                   \
+          break;                                                              \
+        case '8':                                                             \
+          nextFn = TestFn8;                                                   \
+          break;                                                              \
+        default:                                                              \
+          nextFn = TestFn8;                                                   \
+          break;                                                              \
+      }                                                                       \
+      /* "use" |space| immediately after the recursive call, */               \
+      /* so as to dissuade clang from deallocating the space while */         \
+      /* the call is active, or otherwise messing with the stack frame. */    \
+      __asm__ __volatile__("" ::: "cc", "memory");                            \
+      bool passed = nextFn(aLUL, strPorig, strP + 1);                         \
+      Unused << write(1, space, 0);                                           \
+      __asm__ __volatile__("" ::: "cc", "memory");                            \
+      return passed;                                                          \
+    }                                                                         \
+  }
+
+// The test functions are mutually recursive, so it is necessary to
+// declare them before defining them.
+DECL_TEST_FN(TestFn1)
+DECL_TEST_FN(TestFn2)
+DECL_TEST_FN(TestFn3)
+DECL_TEST_FN(TestFn4)
+DECL_TEST_FN(TestFn5)
+DECL_TEST_FN(TestFn6)
+DECL_TEST_FN(TestFn7)
+DECL_TEST_FN(TestFn8)
+
+GEN_TEST_FN(TestFn1, 123)
+GEN_TEST_FN(TestFn2, 456)
+GEN_TEST_FN(TestFn3, 789)
+GEN_TEST_FN(TestFn4, 23)
+GEN_TEST_FN(TestFn5, 47)
+GEN_TEST_FN(TestFn6, 117)
+GEN_TEST_FN(TestFn7, 1)
+GEN_TEST_FN(TestFn8, 99)
+
+// This starts the test sequence going.  Call here to generate a
+// sequence of calls as directed by the string |dstring|.  The call
+// sequence will, from its innermost frame, finish by calling
+// GetAndCheckStackTrace() and passing it |dstring|.
+// GetAndCheckStackTrace() will unwind the stack, check consistency
+// of those results against |dstring|, and print a pass/fail message
+// to aLUL's logging sink.  It also updates the counters in *aNTests
+// and aNTestsPassed.
+__attribute__((noinline)) void TestUnw(/*OUT*/ int* aNTests,
+                                       /*OUT*/ int* aNTestsPassed, LUL* aLUL,
+                                       const char* dstring) {
+  // Ensure that the stack has at least this much space on it.  This
+  // makes it safe to saw off the top LUL_UNIT_TEST_STACK_SIZE bytes
+  // and hand it to LUL.  Safe in the sense that no segfault can
+  // happen because the stack is at least this big.  This is all
+  // somewhat dubious in the sense that a sufficiently clever compiler
+  // (clang, for one) can figure out that space[] is unused and delete
+  // it from the frame.  Hence the somewhat elaborate hoop jumping to
+  // fill it up before the call and to at least appear to use the
+  // value afterwards.
+  int i;
+  volatile char space[LUL_UNIT_TEST_STACK_SIZE];
+  for (i = 0; i < LUL_UNIT_TEST_STACK_SIZE; i++) {
+    space[i] = (char)(i & 0x7F);
+  }
+
+  // Really run the test.
+  bool passed = TestFn1(aLUL, dstring, dstring);
+
+  // Appear to use space[], by visiting the value to compute some kind
+  // of checksum, and then (apparently) using the checksum.
+  int sum = 0;
+  for (i = 0; i < LUL_UNIT_TEST_STACK_SIZE; i++) {
+    // If this doesn't fool LLVM, I don't know what will.
+    sum += space[i] - 3 * i;
+  }
+  __asm__ __volatile__("" : : "r"(sum));
+
+  // Update the counters.
+  (*aNTests)++;
+  if (passed) {
+    (*aNTestsPassed)++;
+  }
+}
+
+void RunLulUnitTests(/*OUT*/ int* aNTests, /*OUT*/ int* aNTestsPassed,
+                     LUL* aLUL) {
+  aLUL->mLog(":\n");
+  aLUL->mLog("LULUnitTest: BEGIN\n");
+  *aNTests = *aNTestsPassed = 0;
+  TestUnw(aNTests, aNTestsPassed, aLUL, "11111111");
+  TestUnw(aNTests, aNTestsPassed, aLUL, "11222211");
+  TestUnw(aNTests, aNTestsPassed, aLUL, "111222333");
+  TestUnw(aNTests, aNTestsPassed, aLUL, "1212121231212331212121212121212");
+  TestUnw(aNTests, aNTestsPassed, aLUL, "31415827271828325332173258");
+  TestUnw(aNTests, aNTestsPassed, aLUL,
+          "123456781122334455667788777777777777777777777");
+  aLUL->mLog("LULUnitTest: END\n");
+  aLUL->mLog(":\n");
+}
+
+}  // namespace lul
diff --git a/mozglue/baseprofiler/lul/LulMain.h b/mozglue/baseprofiler/lul/LulMain.h
new file mode 100644
index 0000000000..987a878c90
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulMain.h
@@ -0,0 +1,378 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LulMain_h
+#define LulMain_h
+
+#include "PlatformMacros.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/BaseProfilerUtils.h"
+
+// LUL: A Lightweight Unwind Library.
+// This file provides the end-user (external) interface for LUL.
+
+// Some comments about naming in the implementation.  These are safe
+// to ignore if you are merely using LUL, but are important if you
+// hack on its internals.
+//
+// Debuginfo readers in general have tended to use the word "address"
+// to mean several different things.  This sometimes makes them
+// difficult to understand and maintain.  LUL tries hard to avoid
+// using the word "address" and instead uses the following more
+// precise terms:
+//
+// * SVMA ("Stated Virtual Memory Address"): this is an address of a
+//   symbol (etc) as it is stated in the symbol table, or other
+//   metadata, of an object.  Such values are typically small and
+//   start from zero or thereabouts, unless the object has been
+//   prelinked.
+//
+// * AVMA ("Actual Virtual Memory Address"): this is the address of a
+//   symbol (etc) in a running process, that is, once the associated
+//   object has been mapped into a process.  Such values are typically
+//   much larger than SVMAs, since objects can get mapped arbitrarily
+//   far along the address space.
+//
+// * "Bias": the difference between AVMA and SVMA for a given symbol
+//   (specifically, AVMA - SVMA).  The bias is always an integral
+//   number of pages.  Once we know the bias for a given object's
+//   text section (for example), we can compute the AVMAs of all of
+//   its text symbols by adding the bias to their SVMAs.
+//
+// * "Image address": typically, to read debuginfo from an object we
+//   will temporarily mmap in the file so as to read symbol tables
+//   etc.  Addresses in this temporary mapping are called "Image
+//   addresses".  Note that the temporary mapping is entirely
+//   unrelated to the mappings of the file that the dynamic linker
+//   must perform merely in order to get the program to run.  Hence
+//   image addresses are unrelated to either SVMAs or AVMAs.
+
+namespace lul {
+
+// A machine word plus validity tag.
+class TaggedUWord {
+ public:
+  // RUNS IN NO-MALLOC CONTEXT
+  // Construct a valid one.
+  explicit TaggedUWord(uintptr_t w) : mValue(w), mValid(true) {}
+
+  // RUNS IN NO-MALLOC CONTEXT
+  // Construct an invalid one.
+  TaggedUWord() : mValue(0), mValid(false) {}
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord operator+(TaggedUWord rhs) const {
+    return (Valid() && rhs.Valid()) ? TaggedUWord(Value() + rhs.Value())
+                                    : TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord operator-(TaggedUWord rhs) const {
+    return (Valid() && rhs.Valid()) ? TaggedUWord(Value() - rhs.Value())
+                                    : TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord operator&(TaggedUWord rhs) const {
+    return (Valid() && rhs.Valid()) ? TaggedUWord(Value() & rhs.Value())
+                                    : TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord operator|(TaggedUWord rhs) const {
+    return (Valid() && rhs.Valid()) ? TaggedUWord(Value() | rhs.Value())
+                                    : TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord CmpGEs(TaggedUWord rhs) const {
+    if (Valid() && rhs.Valid()) {
+      intptr_t s1 = (intptr_t)Value();
+      intptr_t s2 = (intptr_t)rhs.Value();
+      return TaggedUWord(s1 >= s2 ? 1 : 0);
+    }
+    return TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord operator<<(TaggedUWord rhs) const {
+    if (Valid() && rhs.Valid()) {
+      uintptr_t shift = rhs.Value();
+      if (shift < 8 * sizeof(uintptr_t)) return TaggedUWord(Value() << shift);
+    }
+    return TaggedUWord();
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  // Is equal?  Note: non-validity on either side gives non-equality.
+  bool operator==(TaggedUWord other) const {
+    return (mValid && other.Valid()) ? (mValue == other.Value()) : false;
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  // Is it word-aligned?
+  bool IsAligned() const {
+    return mValid && (mValue & (sizeof(uintptr_t) - 1)) == 0;
+  }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  uintptr_t Value() const { return mValue; }
+
+  // RUNS IN NO-MALLOC CONTEXT
+  bool Valid() const { return mValid; }
+
+ private:
+  uintptr_t mValue;
+  bool mValid;
+};
+
+// The registers, with validity tags, that will be unwound.
+
+struct UnwindRegs {
+#if defined(GP_ARCH_arm)
+  TaggedUWord r7;
+  TaggedUWord r11;
+  TaggedUWord r12;
+  TaggedUWord r13;
+  TaggedUWord r14;
+  TaggedUWord r15;
+#elif defined(GP_ARCH_arm64)
+  TaggedUWord x29;
+  TaggedUWord x30;
+  TaggedUWord sp;
+  TaggedUWord pc;
+#elif defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+  TaggedUWord xbp;
+  TaggedUWord xsp;
+  TaggedUWord xip;
+#elif defined(GP_ARCH_mips64)
+  TaggedUWord sp;
+  TaggedUWord fp;
+  TaggedUWord pc;
+#else
+#  error "Unknown plat"
+#endif
+};
+
+// The maximum number of bytes in a stack snapshot.  This value can be increased
+// if necessary, but testing showed that 160k is enough to obtain good
+// backtraces on x86_64 Linux.  Most backtraces fit comfortably into 4-8k of
+// stack space, but we do have some very deep stacks occasionally.  Please see
+// the comments in DoNativeBacktrace as to why it's OK to have this value be so
+// large.
+static const size_t N_STACK_BYTES = 160 * 1024;
+
+// The stack chunk image that will be unwound.
+struct StackImage {
+  // [start_avma, +len) specify the address range in the buffer.
+  // Obviously we require 0 <= len <= N_STACK_BYTES.
+  uintptr_t mStartAvma;
+  size_t mLen;
+  uint8_t mContents[N_STACK_BYTES];
+};
+
+// Statistics collection for the unwinder.
+template <typename T>
+class LULStats {
+ public:
+  LULStats() : mContext(0), mCFI(0), mFP(0) {}
+
+  template <typename S>
+  explicit LULStats(const LULStats<S>& aOther)
+      : mContext(aOther.mContext), mCFI(aOther.mCFI), mFP(aOther.mFP) {}
+
+  template <typename S>
+  LULStats<T>& operator=(const LULStats<S>& aOther) {
+    mContext = aOther.mContext;
+    mCFI = aOther.mCFI;
+    mFP = aOther.mFP;
+    return *this;
+  }
+
+  template <typename S>
+  uint32_t operator-(const LULStats<S>& aOther) {
+    return (mContext - aOther.mContext) + (mCFI - aOther.mCFI) +
+           (mFP - aOther.mFP);
+  }
+
+  T mContext;  // Number of context frames
+  T mCFI;      // Number of CFI/EXIDX frames
+  T mFP;       // Number of frame-pointer recovered frames
+};
+
+// The core unwinder library class.  Just one of these is needed, and
+// it can be shared by multiple unwinder threads.
+//
+// The library operates in one of two modes.
+//
+// * Admin mode.  The library is this state after creation.  In Admin
+//   mode, no unwinding may be performed.  It is however allowable to
+//   perform administrative tasks -- primarily, loading of unwind info
+//   -- in this mode.  In particular, it is safe for the library to
+//   perform dynamic memory allocation in this mode.  Safe in the
+//   sense that there is no risk of deadlock against unwinding threads
+//   that might -- because of where they have been sampled -- hold the
+//   system's malloc lock.
+//
+// * Unwind mode.  In this mode, calls to ::Unwind may be made, but
+//   nothing else.  ::Unwind guarantees not to make any dynamic memory
+//   requests, so as to guarantee that the calling thread won't
+//   deadlock in the case where it already holds the system's malloc lock.
+//
+// The library is created in Admin mode.  After debuginfo is loaded,
+// the caller must switch it into Unwind mode by calling
+// ::EnableUnwinding.  There is no way to switch it back to Admin mode
+// after that.  To safely switch back to Admin mode would require the
+// caller (or other external agent) to guarantee that there are no
+// pending ::Unwind calls.
+
+class PriMap;
+class SegArray;
+class UniqueStringUniverse;
+
+class LUL {
+ public:
+  // Create; supply a logging sink.  Sets the object in Admin mode.
+  explicit LUL(void (*aLog)(const char*));
+
+  // Destroy.  Caller is responsible for ensuring that no other
+  // threads are in Unwind calls.  All resources are freed and all
+  // registered unwinder threads are deregistered.  Can be called
+  // either in Admin or Unwind mode.
+  ~LUL();
+
+  // Notify the library that unwinding is now allowed and so
+  // admin-mode calls are no longer allowed.  The object is initially
+  // created in admin mode.  The only possible transition is
+  // admin->unwinding, therefore.
+  void EnableUnwinding();
+
+  // Notify of a new r-x mapping, and load the associated unwind info.
+  // The filename is strdup'd and used for debug printing.  If
+  // aMappedImage is NULL, this function will mmap/munmap the file
+  // itself, so as to be able to read the unwind info.  If
+  // aMappedImage is non-NULL then it is assumed to point to a
+  // called-supplied and caller-managed mapped image of the file.
+  // May only be called in Admin mode.
+  void NotifyAfterMap(uintptr_t aRXavma, size_t aSize, const char* aFileName,
+                      const void* aMappedImage);
+
+  // In rare cases we know an executable area exists but don't know
+  // what the associated file is.  This call notifies LUL of such
+  // areas.  This is important for correct functioning of stack
+  // scanning and of the x86-{linux,android} special-case
+  // __kernel_syscall function handling.
+  // This must be called only after the code area in
+  // question really has been mapped.
+  // May only be called in Admin mode.
+  void NotifyExecutableArea(uintptr_t aRXavma, size_t aSize);
+
+  // Notify that a mapped area has been unmapped; discard any
+  // associated unwind info.  Acquires mRWlock for writing.  Note that
+  // to avoid segfaulting the stack-scan unwinder, which inspects code
+  // areas, this must be called before the code area in question is
+  // really unmapped.  Note that, unlike NotifyAfterMap(), this
+  // function takes the start and end addresses of the range to be
+  // unmapped, rather than a start and a length parameter.  This is so
+  // as to make it possible to notify an unmap for the entire address
+  // space using a single call.
+  // May only be called in Admin mode.
+  void NotifyBeforeUnmap(uintptr_t aAvmaMin, uintptr_t aAvmaMax);
+
+  // Apply NotifyBeforeUnmap to the entire address space.  This causes
+  // LUL to discard all unwind and executable-area information for the
+  // entire address space.
+  // May only be called in Admin mode.
+  void NotifyBeforeUnmapAll() { NotifyBeforeUnmap(0, UINTPTR_MAX); }
+
+  // Returns the number of mappings currently registered.
+  // May only be called in Admin mode.
+  size_t CountMappings();
+
+  // Unwind |aStackImg| starting with the context in |aStartRegs|.
+  // Write the number of frames recovered in *aFramesUsed.  Put
+  // the PC values in aFramePCs[0 .. *aFramesUsed-1] and
+  // the SP values in aFrameSPs[0 .. *aFramesUsed-1].
+  // |aFramesAvail| is the size of the two output arrays and hence the
+  // largest possible value of *aFramesUsed.  PC values are always
+  // valid, and the unwind will stop when the PC becomes invalid, but
+  // the SP values might be invalid, in which case the value zero will
+  // be written in the relevant frameSPs[] slot.
+  //
+  // This function assumes that the SP values increase as it unwinds
+  // away from the innermost frame -- that is, that the stack grows
+  // down.  It monitors SP values as it unwinds to check they
+  // decrease, so as to avoid looping on corrupted stacks.
+  //
+  // May only be called in Unwind mode.  Multiple threads may unwind
+  // at once.  LUL user is responsible for ensuring that no thread makes
+  // any Admin calls whilst in Unwind mode.
+  // MOZ_CRASHes if the calling thread is not registered for unwinding.
+  //
+  // The calling thread must previously have been registered via a call to
+  // RegisterSampledThread.
+  void Unwind(/*OUT*/ uintptr_t* aFramePCs,
+              /*OUT*/ uintptr_t* aFrameSPs,
+              /*OUT*/ size_t* aFramesUsed,
+              /*OUT*/ size_t* aFramePointerFramesAcquired, size_t aFramesAvail,
+              UnwindRegs* aStartRegs, StackImage* aStackImg);
+
+  // The logging sink.  Call to send debug strings to the caller-
+  // specified destination.  Can only be called by the Admin thread.
+  void (*mLog)(const char*);
+
+  // Statistics relating to unwinding.  These have to be atomic since
+  // unwinding can occur on different threads simultaneously.
+  LULStats<mozilla::Atomic<uint32_t>> mStats;
+
+  // Possibly show the statistics.  This may not be called from any
+  // registered sampling thread, since it involves I/O.
+  void MaybeShowStats();
+
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf) const;
+
+ private:
+  // The statistics counters at the point where they were last printed.
+  LULStats<uint32_t> mStatsPrevious;
+
+  // Are we in admin mode?  Initially |true| but changes to |false|
+  // once unwinding begins.
+  bool mAdminMode;
+
+  // The thread ID associated with admin mode.  This is the only thread
+  // that is allowed do perform non-Unwind calls on this object.  Conversely,
+  // no registered Unwinding thread may be the admin thread.  This is so
+  // as to clearly partition the one thread that may do dynamic memory
+  // allocation from the threads that are being sampled, since the latter
+  // absolutely may not do dynamic memory allocation.
+  mozilla::baseprofiler::BaseProfilerThreadId mAdminThreadId;
+
+  // The top level mapping from code address ranges to postprocessed
+  // unwind info.  Basically a sorted array of (addr, len, info)
+  // records.  This field is updated by NotifyAfterMap and NotifyBeforeUnmap.
+  PriMap* mPriMap;
+
+  // An auxiliary structure that records which address ranges are
+  // mapped r-x, for the benefit of the stack scanner.
+  SegArray* mSegArray;
+
+  // A UniqueStringUniverse that holds all the strdup'd strings created
+  // whilst reading unwind information.  This is included so as to make
+  // it possible to free them in ~LUL.
+  UniqueStringUniverse* mUSU;
+};
+
+// Run unit tests on an initialised, loaded-up LUL instance, and print
+// summary results on |aLUL|'s logging sink.  Also return the number
+// of tests run in *aNTests and the number that passed in
+// *aNTestsPassed.
+void RunLulUnitTests(/*OUT*/ int* aNTests, /*OUT*/ int* aNTestsPassed,
+                     LUL* aLUL);
+
+}  // namespace lul
+
+#endif  // LulMain_h
diff --git a/mozglue/baseprofiler/lul/LulMainInt.h b/mozglue/baseprofiler/lul/LulMainInt.h
new file mode 100644
index 0000000000..c2ee45d73d
--- /dev/null
+++ b/mozglue/baseprofiler/lul/LulMainInt.h
@@ -0,0 +1,420 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LulMainInt_h
+#define LulMainInt_h
+
+#include "PlatformMacros.h"
+#include "LulMain.h"  // for TaggedUWord
+
+#include "mozilla/Assertions.h"
+
+#include <string>
+#include <vector>
+
+// This file is provides internal interface inside LUL.  If you are an
+// end-user of LUL, do not include it in your code.  The end-user
+// interface is in LulMain.h.
+
+namespace lul {
+
+using std::vector;
+
+////////////////////////////////////////////////////////////////
+// DW_REG_ constants                                          //
+////////////////////////////////////////////////////////////////
+
+// These are the Dwarf CFI register numbers, as (presumably) defined
+// in the ELF ABI supplements for each architecture.
+
+enum DW_REG_NUMBER {
+  // No real register has this number.  It's convenient to be able to
+  // treat the CFA (Canonical Frame Address) as "just another
+  // register", though.
+  DW_REG_CFA = -1,
+#if defined(GP_ARCH_arm)
+  // ARM registers
+  DW_REG_ARM_R7 = 7,
+  DW_REG_ARM_R11 = 11,
+  DW_REG_ARM_R12 = 12,
+  DW_REG_ARM_R13 = 13,
+  DW_REG_ARM_R14 = 14,
+  DW_REG_ARM_R15 = 15,
+#elif defined(GP_ARCH_arm64)
+  // aarch64 registers
+  DW_REG_AARCH64_X29 = 29,
+  DW_REG_AARCH64_X30 = 30,
+  DW_REG_AARCH64_SP = 31,
+#elif defined(GP_ARCH_amd64)
+  // Because the X86 (32 bit) and AMD64 (64 bit) summarisers are
+  // combined, a merged set of register constants is needed.
+  DW_REG_INTEL_XBP = 6,
+  DW_REG_INTEL_XSP = 7,
+  DW_REG_INTEL_XIP = 16,
+#elif defined(GP_ARCH_x86)
+  DW_REG_INTEL_XBP = 5,
+  DW_REG_INTEL_XSP = 4,
+  DW_REG_INTEL_XIP = 8,
+#elif defined(GP_ARCH_mips64)
+  DW_REG_MIPS_SP = 29,
+  DW_REG_MIPS_FP = 30,
+  DW_REG_MIPS_PC = 34,
+#else
+#  error "Unknown arch"
+#endif
+};
+
+////////////////////////////////////////////////////////////////
+// PfxExpr                                                    //
+////////////////////////////////////////////////////////////////
+
+enum PfxExprOp {
+  //             meaning of mOperand     effect on stack
+  PX_Start,   // bool start-with-CFA?    start, with CFA on stack, or not
+  PX_End,     // none                    stop; result is at top of stack
+  PX_SImm32,  // int32                   push signed int32
+  PX_DwReg,   // DW_REG_NUMBER           push value of the specified reg
+  PX_Deref,   // none                    pop X ; push *X
+  PX_Add,     // none                    pop X ; pop Y ; push Y + X
+  PX_Sub,     // none                    pop X ; pop Y ; push Y - X
+  PX_And,     // none                    pop X ; pop Y ; push Y & X
+  PX_Or,      // none                    pop X ; pop Y ; push Y | X
+  PX_CmpGES,  // none                    pop X ; pop Y ; push (Y >=s X) ? 1 : 0
+  PX_Shl      // none                    pop X ; pop Y ; push Y << X
+};
+
+struct PfxInstr {
+  PfxInstr(PfxExprOp opcode, int32_t operand)
+      : mOpcode(opcode), mOperand(operand) {}
+  explicit PfxInstr(PfxExprOp opcode) : mOpcode(opcode), mOperand(0) {}
+  bool operator==(const PfxInstr& other) const {
+    return mOpcode == other.mOpcode && mOperand == other.mOperand;
+  }
+  PfxExprOp mOpcode;
+  int32_t mOperand;
+};
+
+static_assert(sizeof(PfxInstr) <= 8, "PfxInstr size changed unexpectedly");
+
+// Evaluate the prefix expression whose PfxInstrs start at aPfxInstrs[start].
+// In the case of any mishap (stack over/underflow, running off the end of
+// the instruction vector, obviously malformed sequences),
+// return an invalid TaggedUWord.
+// RUNS IN NO-MALLOC CONTEXT
+TaggedUWord EvaluatePfxExpr(int32_t start, const UnwindRegs* aOldRegs,
+                            TaggedUWord aCFA, const StackImage* aStackImg,
+                            const vector<PfxInstr>& aPfxInstrs);
+
+////////////////////////////////////////////////////////////////
+// LExpr                                                      //
+////////////////////////////////////////////////////////////////
+
+// An expression -- very primitive.  Denotes either "register +
+// offset", a dereferenced version of the same, or a reference to a
+// prefix expression stored elsewhere.  So as to allow convenient
+// handling of Dwarf-derived unwind info, the register may also denote
+// the CFA.  A large number of these need to be stored, so we ensure
+// it fits into 8 bytes.  See comment below on RuleSet to see how
+// expressions fit into the bigger picture.
+
+enum LExprHow {
+  UNKNOWN = 0,  // This LExpr denotes no value.
+  NODEREF,      // Value is  (mReg + mOffset).
+  DEREF,        // Value is *(mReg + mOffset).
+  PFXEXPR       // Value is EvaluatePfxExpr(secMap->mPfxInstrs[mOffset])
+};
+
+inline static const char* NameOf_LExprHow(LExprHow how) {
+  switch (how) {
+    case UNKNOWN:
+      return "UNKNOWN";
+    case NODEREF:
+      return "NODEREF";
+    case DEREF:
+      return "DEREF";
+    case PFXEXPR:
+      return "PFXEXPR";
+    default:
+      return "LExpr-??";
+  }
+}
+
+struct LExpr {
+  // Denotes an expression with no value.
+  LExpr() : mHow(UNKNOWN), mReg(0), mOffset(0) {}
+
+  // Denotes any expressible expression.
+  LExpr(LExprHow how, int16_t reg, int32_t offset)
+      : mHow(how), mReg(reg), mOffset(offset) {
+    switch (how) {
+      case UNKNOWN:
+        MOZ_ASSERT(reg == 0 && offset == 0);
+        break;
+      case NODEREF:
+        break;
+      case DEREF:
+        break;
+      case PFXEXPR:
+        MOZ_ASSERT(reg == 0 && offset >= 0);
+        break;
+      default:
+        MOZ_ASSERT(0, "LExpr::LExpr: invalid how");
+    }
+  }
+
+  // Change the offset for an expression that references memory.
+  LExpr add_delta(long delta) {
+    MOZ_ASSERT(mHow == NODEREF);
+    // If this is a non-debug build and the above assertion would have
+    // failed, at least return LExpr() so that the machinery that uses
+    // the resulting expression fails in a repeatable way.
+    return (mHow == NODEREF) ? LExpr(mHow, mReg, mOffset + delta)
+                             : LExpr();  // Gone bad
+  }
+
+  // Dereference an expression that denotes a memory address.
+  LExpr deref() {
+    MOZ_ASSERT(mHow == NODEREF);
+    // Same rationale as for add_delta().
+    return (mHow == NODEREF) ? LExpr(DEREF, mReg, mOffset)
+                             : LExpr();  // Gone bad
+  }
+
+  // Print a rule for recovery of |aNewReg| whose recovered value
+  // is this LExpr.
+  std::string ShowRule(const char* aNewReg) const;
+
+  // Evaluate this expression, producing a TaggedUWord.  |aOldRegs|
+  // holds register values that may be referred to by the expression.
+  // |aCFA| holds the CFA value, if any, that applies.  |aStackImg|
+  // contains a chuck of stack that will be consulted if the expression
+  // references memory.  |aPfxInstrs| holds the vector of PfxInstrs
+  // that will be consulted if this is a PFXEXPR.
+  // RUNS IN NO-MALLOC CONTEXT
+  TaggedUWord EvaluateExpr(const UnwindRegs* aOldRegs, TaggedUWord aCFA,
+                           const StackImage* aStackImg,
+                           const vector<PfxInstr>* aPfxInstrs) const;
+
+  // Representation of expressions.  If |mReg| is DW_REG_CFA (-1) then
+  // it denotes the CFA.  All other allowed values for |mReg| are
+  // nonnegative and are DW_REG_ values.
+  LExprHow mHow : 8;
+  int16_t mReg;     // A DW_REG_ value
+  int32_t mOffset;  // 32-bit signed offset should be more than enough.
+};
+
+static_assert(sizeof(LExpr) <= 8, "LExpr size changed unexpectedly");
+
+////////////////////////////////////////////////////////////////
+// RuleSet                                                    //
+////////////////////////////////////////////////////////////////
+
+// This is platform-dependent.  For some address range, describes how
+// to recover the CFA and then how to recover the registers for the
+// previous frame.
+//
+// The set of LExprs contained in a given RuleSet describe a DAG which
+// says how to compute the caller's registers ("new registers") from
+// the callee's registers ("old registers").  The DAG can contain a
+// single internal node, which is the value of the CFA for the callee.
+// It would be possible to construct a DAG that omits the CFA, but
+// including it makes the summarisers simpler, and the Dwarf CFI spec
+// has the CFA as a central concept.
+//
+// For this to make sense, |mCfaExpr| can't have
+// |mReg| == DW_REG_CFA since we have no previous value for the CFA.
+// All of the other |Expr| fields can -- and usually do -- specify
+// |mReg| == DW_REG_CFA.
+//
+// With that in place, the unwind algorithm proceeds as follows.
+//
+// (0) Initially: we have values for the old registers, and a memory
+//     image.
+//
+// (1) Compute the CFA by evaluating |mCfaExpr|.  Add the computed
+//     value to the set of "old registers".
+//
+// (2) Compute values for the registers by evaluating all of the other
+//     |Expr| fields in the RuleSet.  These can depend on both the old
+//     register values and the just-computed CFA.
+//
+// If we are unwinding without computing a CFA, perhaps because the
+// RuleSets are derived from EXIDX instead of Dwarf, then
+// |mCfaExpr.mHow| will be LExpr::UNKNOWN, so the computed value will
+// be invalid -- that is, TaggedUWord() -- and so any attempt to use
+// that will result in the same value.  But that's OK because the
+// RuleSet would make no sense if depended on the CFA but specified no
+// way to compute it.
+//
+// A RuleSet is not allowed to cover zero address range.  Having zero
+// length would break binary searching in SecMaps and PriMaps.
+
+class RuleSet {
+ public:
+  RuleSet();
+  void Print(void (*aLog)(const char*)) const;
+
+  // Find the LExpr* for a given DW_REG_ value in this class.
+  LExpr* ExprForRegno(DW_REG_NUMBER aRegno);
+
+  uintptr_t mAddr;
+  uintptr_t mLen;
+  // How to compute the CFA.
+  LExpr mCfaExpr;
+  // How to compute caller register values.  These may reference the
+  // value defined by |mCfaExpr|.
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+  LExpr mXipExpr;  // return address
+  LExpr mXspExpr;
+  LExpr mXbpExpr;
+#elif defined(GP_ARCH_arm)
+  LExpr mR15expr;  // return address
+  LExpr mR14expr;
+  LExpr mR13expr;
+  LExpr mR12expr;
+  LExpr mR11expr;
+  LExpr mR7expr;
+#elif defined(GP_ARCH_arm64)
+  LExpr mX29expr;  // frame pointer register
+  LExpr mX30expr;  // link register
+  LExpr mSPexpr;
+#elif defined(GP_ARCH_mips64)
+  LExpr mPCexpr;
+  LExpr mFPexpr;
+  LExpr mSPexpr;
+#else
+#  error "Unknown arch"
+#endif
+};
+
+// Returns |true| for Dwarf register numbers which are members
+// of the set of registers that LUL unwinds on this target.
+static inline bool registerIsTracked(DW_REG_NUMBER reg) {
+  switch (reg) {
+#if defined(GP_ARCH_amd64) || defined(GP_ARCH_x86)
+    case DW_REG_INTEL_XBP:
+    case DW_REG_INTEL_XSP:
+    case DW_REG_INTEL_XIP:
+      return true;
+#elif defined(GP_ARCH_arm)
+    case DW_REG_ARM_R7:
+    case DW_REG_ARM_R11:
+    case DW_REG_ARM_R12:
+    case DW_REG_ARM_R13:
+    case DW_REG_ARM_R14:
+    case DW_REG_ARM_R15:
+      return true;
+#elif defined(GP_ARCH_arm64)
+    case DW_REG_AARCH64_X29:
+    case DW_REG_AARCH64_X30:
+    case DW_REG_AARCH64_SP:
+      return true;
+#elif defined(GP_ARCH_mips64)
+    case DW_REG_MIPS_FP:
+    case DW_REG_MIPS_SP:
+    case DW_REG_MIPS_PC:
+      return true;
+#else
+#  error "Unknown arch"
+#endif
+    default:
+      return false;
+  }
+}
+
+////////////////////////////////////////////////////////////////
+// SecMap                                                     //
+////////////////////////////////////////////////////////////////
+
+// A SecMap may have zero address range, temporarily, whilst RuleSets
+// are being added to it.  But adding a zero-range SecMap to a PriMap
+// will make it impossible to maintain the total order of the PriMap
+// entries, and so that can't be allowed to happen.
+
+class SecMap {
+ public:
+  // These summarise the contained mRuleSets, in that they give
+  // exactly the lowest and highest addresses that any of the entries
+  // in this SecMap cover.  Hence invariants:
+  //
+  // mRuleSets is nonempty
+  //    <=> mSummaryMinAddr <= mSummaryMaxAddr
+  //        && mSummaryMinAddr == mRuleSets[0].mAddr
+  //        && mSummaryMaxAddr == mRuleSets[#rulesets-1].mAddr
+  //                              + mRuleSets[#rulesets-1].mLen - 1;
+  //
+  // This requires that no RuleSet has zero length.
+  //
+  // mRuleSets is empty
+  //    <=> mSummaryMinAddr > mSummaryMaxAddr
+  //
+  // This doesn't constrain mSummaryMinAddr and mSummaryMaxAddr uniquely,
+  // so let's use mSummaryMinAddr == 1 and mSummaryMaxAddr == 0 to denote
+  // this case.
+
+  explicit SecMap(void (*aLog)(const char*));
+  ~SecMap();
+
+  // Binary search mRuleSets to find one that brackets |ia|, or nullptr
+  // if none is found.  It's not allowable to do this until PrepareRuleSets
+  // has been called first.
+  RuleSet* FindRuleSet(uintptr_t ia);
+
+  // Add a RuleSet to the collection.  The rule is copied in.  Calling
+  // this makes the map non-searchable.
+  void AddRuleSet(const RuleSet* rs);
+
+  // Add a PfxInstr to the vector of such instrs, and return the index
+  // in the vector.  Calling this makes the map non-searchable.
+  uint32_t AddPfxInstr(PfxInstr pfxi);
+
+  // Returns the entire vector of PfxInstrs.
+  const vector<PfxInstr>* GetPfxInstrs() { return &mPfxInstrs; }
+
+  // Prepare the map for searching.  Also, remove any rules for code
+  // address ranges which don't fall inside [start, +len).  |len| may
+  // not be zero.
+  void PrepareRuleSets(uintptr_t start, size_t len);
+
+  bool IsEmpty();
+
+  size_t Size() { return mRuleSets.size(); }
+
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+  // The min and max addresses of the addresses in the contained
+  // RuleSets.  See comment above for invariants.
+  uintptr_t mSummaryMinAddr;
+  uintptr_t mSummaryMaxAddr;
+
+ private:
+  // False whilst adding entries; true once it is safe to call FindRuleSet.
+  // Transition (false->true) is caused by calling PrepareRuleSets().
+  bool mUsable;
+
+  // A vector of RuleSets, sorted, nonoverlapping (post Prepare()).
+  vector<RuleSet> mRuleSets;
+
+  // A vector of PfxInstrs, which are referred to by the RuleSets.
+  // These are provided as a representation of Dwarf expressions
+  // (DW_CFA_val_expression, DW_CFA_expression, DW_CFA_def_cfa_expression),
+  // are relatively expensive to evaluate, and and are therefore
+  // expected to be used only occasionally.
+  //
+  // The vector holds a bunch of separate PfxInstr programs, each one
+  // starting with a PX_Start and terminated by a PX_End, all
+  // concatenated together.  When a RuleSet can't recover a value
+  // using a self-contained LExpr, it uses a PFXEXPR whose mOffset is
+  // the index in this vector of start of the necessary PfxInstr program.
+  vector<PfxInstr> mPfxInstrs;
+
+  // A logging sink, for debugging.
+  void (*mLog)(const char*);
+};
+
+}  // namespace lul
+
+#endif  // ndef LulMainInt_h
diff --git a/mozglue/baseprofiler/lul/platform-linux-lul.cpp b/mozglue/baseprofiler/lul/platform-linux-lul.cpp
new file mode 100644
index 0000000000..a9ee65858d
--- /dev/null
+++ b/mozglue/baseprofiler/lul/platform-linux-lul.cpp
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdio.h>
+#include <signal.h>
+#include <string.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "AutoObjectMapper.h"
+#include "BaseProfiler.h"
+#include "BaseProfilerSharedLibraries.h"
+#include "platform.h"
+#include "PlatformMacros.h"
+#include "LulMain.h"
+
+// Contains miscellaneous helpers that are used to connect the Gecko Profiler
+// and LUL.
+
+// Find out, in a platform-dependent way, where the code modules got
+// mapped in the process' virtual address space, and get |aLUL| to
+// load unwind info for them.
+void read_procmaps(lul::LUL* aLUL) {
+  MOZ_ASSERT(aLUL->CountMappings() == 0);
+
+#if defined(GP_OS_linux) || defined(GP_OS_android) || defined(GP_OS_freebsd)
+  SharedLibraryInfo info = SharedLibraryInfo::GetInfoForSelf();
+
+  for (size_t i = 0; i < info.GetSize(); i++) {
+    const SharedLibrary& lib = info.GetEntry(i);
+
+    std::string nativePath = lib.GetDebugPath();
+
+    // We can use the standard POSIX-based mapper.
+    AutoObjectMapperPOSIX mapper(aLUL->mLog);
+
+    // Ask |mapper| to map the object.  Then hand its mapped address
+    // to NotifyAfterMap().
+    void* image = nullptr;
+    size_t size = 0;
+    bool ok = mapper.Map(&image, &size, nativePath);
+    if (ok && image && size > 0) {
+      aLUL->NotifyAfterMap(lib.GetStart(), lib.GetEnd() - lib.GetStart(),
+                           nativePath.c_str(), image);
+    } else if (!ok && lib.GetDebugName().empty()) {
+      // The object has no name and (as a consequence) the mapper failed to map
+      // it.  This happens on Linux, where GetInfoForSelf() produces such a
+      // mapping for the VDSO.  This is a problem on x86-{linux,android} because
+      // lack of knowledge about the mapped area inhibits LUL's special
+      // __kernel_syscall handling.  Hence notify |aLUL| at least of the
+      // mapping, even though it can't read any unwind information for the area.
+      aLUL->NotifyExecutableArea(lib.GetStart(), lib.GetEnd() - lib.GetStart());
+    }
+
+    // |mapper| goes out of scope at this point and so its destructor
+    // unmaps the object.
+  }
+
+#else
+#  error "Unknown platform"
+#endif
+}
+
+// LUL needs a callback for its logging sink.
+void logging_sink_for_LUL(const char* str) {
+  // These are only printed when Verbose logging is enabled (e.g. with
+  // MOZ_BASE_PROFILER_VERBOSE_LOGGING=1). This is because LUL's logging is much
+  // more verbose than the rest of the profiler's logging, which occurs at the
+  // Info (3) and Debug (4) levels.
+  // FIXME: This causes a build failure in memory/replace/dmd/test/SmokeDMD (!)
+  // and other places, because it doesn't link the implementation in
+  // platform.cpp.
+  // VERBOSE_LOG("[%d] %s", profiler_current_process_id(), str);
+}
diff --git a/mozglue/baseprofiler/lul/platform-linux-lul.h b/mozglue/baseprofiler/lul/platform-linux-lul.h
new file mode 100644
index 0000000000..b54e80edcf
--- /dev/null
+++ b/mozglue/baseprofiler/lul/platform-linux-lul.h
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZ_PLATFORM_LINUX_LUL_H
+#define MOZ_PLATFORM_LINUX_LUL_H
+
+#include "platform.h"
+
+#include "BaseProfiler.h"
+
+// Find out, in a platform-dependent way, where the code modules got
+// mapped in the process' virtual address space, and get |aLUL| to
+// load unwind info for them.
+void read_procmaps(lul::LUL* aLUL);
+
+// LUL needs a callback for its logging sink.
+void logging_sink_for_LUL(const char* str);
+
+#endif /* ndef MOZ_PLATFORM_LINUX_LUL_H */