Adding upstream version 110.0.1.upstream/110.0.1upstream

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

1 files changed, 597 insertions, 0 deletions

diff --git a/tools/profiler/core/EHABIStackWalk.cpp b/tools/profiler/core/EHABIStackWalk.cpp
new file mode 100644
index 0000000000..e3099b89ec
--- /dev/null
+++ b/tools/profiler/core/EHABIStackWalk.cpp
@@ -0,0 +1,597 @@
+/* -*- 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/. */
+
+/*
+ * This is an implementation of stack unwinding according to a subset
+ * of the ARM Exception Handling ABI, as described in:
+ *   http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
+ *
+ * This handles only the ARM-defined "personality routines" (chapter
+ * 9), and don't track the value of FP registers, because profiling
+ * needs only chain of PC/SP values.
+ *
+ * Because the exception handling info may not be accurate for all
+ * possible places where an async signal could occur (e.g., in a
+ * prologue or epilogue), this bounds-checks all stack accesses.
+ *
+ * This file uses "struct" for structures in the exception tables and
+ * "class" otherwise.  We should avoid violating the C++11
+ * standard-layout rules in the former.
+ */
+
+#include "EHABIStackWalk.h"
+
+#include "shared-libraries.h"
+#include "platform.h"
+
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/EndianUtils.h"
+
+#include <algorithm>
+#include <elf.h>
+#include <stdint.h>
+#include <vector>
+#include <string>
+
+#ifndef PT_ARM_EXIDX
+#  define PT_ARM_EXIDX 0x70000001
+#endif
+
+namespace mozilla {
+
+struct PRel31 {
+  uint32_t mBits;
+  bool topBit() const { return mBits & 0x80000000; }
+  uint32_t value() const { return mBits & 0x7fffffff; }
+  int32_t offset() const { return (static_cast<int32_t>(mBits) << 1) >> 1; }
+  const void* compute() const {
+    return reinterpret_cast<const char*>(this) + offset();
+  }
+
+ private:
+  PRel31(const PRel31& copied) = delete;
+  PRel31() = delete;
+};
+
+struct EHEntry {
+  PRel31 startPC;
+  PRel31 exidx;
+
+ private:
+  EHEntry(const EHEntry& copied) = delete;
+  EHEntry() = delete;
+};
+
+class EHState {
+  // Note that any core register can be used as a "frame pointer" to
+  // influence the unwinding process, so this must track all of them.
+  uint32_t mRegs[16];
+
+ public:
+  bool unwind(const EHEntry* aEntry, const void* stackBase);
+  uint32_t& operator[](int i) { return mRegs[i]; }
+  const uint32_t& operator[](int i) const { return mRegs[i]; }
+  explicit EHState(const mcontext_t&);
+};
+
+enum { R_SP = 13, R_LR = 14, R_PC = 15 };
+
+class EHTable {
+  uint32_t mStartPC;
+  uint32_t mEndPC;
+  uint32_t mBaseAddress;
+  const EHEntry* mEntriesBegin;
+  const EHEntry* mEntriesEnd;
+  std::string mName;
+
+ public:
+  EHTable(const void* aELF, size_t aSize, const std::string& aName);
+  const EHEntry* lookup(uint32_t aPC) const;
+  bool isValid() const { return mEntriesEnd != mEntriesBegin; }
+  const std::string& name() const { return mName; }
+  uint32_t startPC() const { return mStartPC; }
+  uint32_t endPC() const { return mEndPC; }
+  uint32_t baseAddress() const { return mBaseAddress; }
+};
+
+class EHAddrSpace {
+  std::vector<uint32_t> mStarts;
+  std::vector<EHTable> mTables;
+  static mozilla::Atomic<const EHAddrSpace*> sCurrent;
+
+ public:
+  explicit EHAddrSpace(const std::vector<EHTable>& aTables);
+  const EHTable* lookup(uint32_t aPC) const;
+  static void Update();
+  static const EHAddrSpace* Get();
+};
+
+void EHABIStackWalkInit() { EHAddrSpace::Update(); }
+
+size_t EHABIStackWalk(const mcontext_t& aContext, void* stackBase, void** aSPs,
+                      void** aPCs, const size_t aNumFrames) {
+  const EHAddrSpace* space = EHAddrSpace::Get();
+  EHState state(aContext);
+  size_t count = 0;
+
+  while (count < aNumFrames) {
+    uint32_t pc = state[R_PC], sp = state[R_SP];
+
+    // ARM instructions are always aligned to 2 or 4 bytes.
+    // The last bit of the pc / lr indicates ARM or Thumb mode.
+    // We're only interested in the instruction address, so we mask off that
+    // bit.
+    constexpr uint32_t instrAddrMask = ~1;
+    uint32_t instrAddress = pc & instrAddrMask;
+
+    aPCs[count] = reinterpret_cast<void*>(instrAddress);
+    aSPs[count] = reinterpret_cast<void*>(sp);
+    count++;
+
+    if (!space) break;
+    // TODO: cache these lookups.  Binary-searching libxul is
+    // expensive (possibly more expensive than doing the actual
+    // unwind), and even a small cache should help.
+    const EHTable* table = space->lookup(pc);
+    if (!table) break;
+    const EHEntry* entry = table->lookup(pc);
+    if (!entry) break;
+    if (!state.unwind(entry, stackBase)) break;
+  }
+
+  return count;
+}
+
+class EHInterp {
+ public:
+  // Note that stackLimit is exclusive and stackBase is inclusive
+  // (i.e, stackLimit < SP <= stackBase), following the convention
+  // set by the AAPCS spec.
+  EHInterp(EHState& aState, const EHEntry* aEntry, uint32_t aStackLimit,
+           uint32_t aStackBase)
+      : mState(aState),
+        mStackLimit(aStackLimit),
+        mStackBase(aStackBase),
+        mNextWord(0),
+        mWordsLeft(0),
+        mFailed(false) {
+    const PRel31& exidx = aEntry->exidx;
+    uint32_t firstWord;
+
+    if (exidx.mBits == 1) {  // EXIDX_CANTUNWIND
+      mFailed = true;
+      return;
+    }
+    if (exidx.topBit()) {
+      firstWord = exidx.mBits;
+    } else {
+      mNextWord = reinterpret_cast<const uint32_t*>(exidx.compute());
+      firstWord = *mNextWord++;
+    }
+
+    switch (firstWord >> 24) {
+      case 0x80:  // short
+        mWord = firstWord << 8;
+        mBytesLeft = 3;
+        break;
+      case 0x81:
+      case 0x82:  // long; catch descriptor size ignored
+        mWord = firstWord << 16;
+        mBytesLeft = 2;
+        mWordsLeft = (firstWord >> 16) & 0xff;
+        break;
+      default:
+        // unknown personality
+        mFailed = true;
+    }
+  }
+
+  bool unwind();
+
+ private:
+  // TODO: GCC has been observed not CSEing repeated reads of
+  // mState[R_SP] with writes to mFailed between them, suggesting that
+  // it hasn't determined that they can't alias and is thus missing
+  // optimization opportunities.  So, we may want to flatten EHState
+  // into this class; this may also make the code simpler.
+  EHState& mState;
+  uint32_t mStackLimit;
+  uint32_t mStackBase;
+  const uint32_t* mNextWord;
+  uint32_t mWord;
+  uint8_t mWordsLeft;
+  uint8_t mBytesLeft;
+  bool mFailed;
+
+  enum {
+    I_ADDSP = 0x00,  // 0sxxxxxx (subtract if s)
+    M_ADDSP = 0x80,
+    I_POPMASK = 0x80,  // 1000iiii iiiiiiii (if any i set)
+    M_POPMASK = 0xf0,
+    I_MOVSP = 0x90,  // 1001nnnn
+    M_MOVSP = 0xf0,
+    I_POPN = 0xa0,  // 1010lnnn
+    M_POPN = 0xf0,
+    I_FINISH = 0xb0,    // 10110000
+    I_POPLO = 0xb1,     // 10110001 0000iiii (if any i set)
+    I_ADDSPBIG = 0xb2,  // 10110010 uleb128
+    I_POPFDX = 0xb3,    // 10110011 sssscccc
+    I_POPFDX8 = 0xb8,   // 10111nnn
+    M_POPFDX8 = 0xf8,
+    // "Intel Wireless MMX" extensions omitted.
+    I_POPFDD = 0xc8,  // 1100100h sssscccc
+    M_POPFDD = 0xfe,
+    I_POPFDD8 = 0xd0,  // 11010nnn
+    M_POPFDD8 = 0xf8
+  };
+
+  uint8_t next() {
+    if (mBytesLeft == 0) {
+      if (mWordsLeft == 0) {
+        return I_FINISH;
+      }
+      mWordsLeft--;
+      mWord = *mNextWord++;
+      mBytesLeft = 4;
+    }
+    mBytesLeft--;
+    mWord = (mWord << 8) | (mWord >> 24);  // rotate
+    return mWord;
+  }
+
+  uint32_t& vSP() { return mState[R_SP]; }
+  uint32_t* ptrSP() { return reinterpret_cast<uint32_t*>(vSP()); }
+
+  void checkStackBase() {
+    if (vSP() > mStackBase) mFailed = true;
+  }
+  void checkStackLimit() {
+    if (vSP() <= mStackLimit) mFailed = true;
+  }
+  void checkStackAlign() {
+    if ((vSP() & 3) != 0) mFailed = true;
+  }
+  void checkStack() {
+    checkStackBase();
+    checkStackLimit();
+    checkStackAlign();
+  }
+
+  void popRange(uint8_t first, uint8_t last, uint16_t mask) {
+    bool hasSP = false;
+    uint32_t tmpSP;
+    if (mask == 0) mFailed = true;
+    for (uint8_t r = first; r <= last; ++r) {
+      if (mask & 1) {
+        if (r == R_SP) {
+          hasSP = true;
+          tmpSP = *ptrSP();
+        } else
+          mState[r] = *ptrSP();
+        vSP() += 4;
+        checkStackBase();
+        if (mFailed) return;
+      }
+      mask >>= 1;
+    }
+    if (hasSP) {
+      vSP() = tmpSP;
+      checkStack();
+    }
+  }
+};
+
+bool EHState::unwind(const EHEntry* aEntry, const void* stackBasePtr) {
+  // The unwinding program cannot set SP to less than the initial value.
+  uint32_t stackLimit = mRegs[R_SP] - 4;
+  uint32_t stackBase = reinterpret_cast<uint32_t>(stackBasePtr);
+  EHInterp interp(*this, aEntry, stackLimit, stackBase);
+  return interp.unwind();
+}
+
+bool EHInterp::unwind() {
+  mState[R_PC] = 0;
+  checkStack();
+  while (!mFailed) {
+    uint8_t insn = next();
+#if DEBUG_EHABI_UNWIND
+    LOG("unwind insn = %02x", (unsigned)insn);
+#endif
+    // Try to put the common cases first.
+
+    // 00xxxxxx: vsp = vsp + (xxxxxx << 2) + 4
+    // 01xxxxxx: vsp = vsp - (xxxxxx << 2) - 4
+    if ((insn & M_ADDSP) == I_ADDSP) {
+      uint32_t offset = ((insn & 0x3f) << 2) + 4;
+      if (insn & 0x40) {
+        vSP() -= offset;
+        checkStackLimit();
+      } else {
+        vSP() += offset;
+        checkStackBase();
+      }
+      continue;
+    }
+
+    // 10100nnn: Pop r4-r[4+nnn]
+    // 10101nnn: Pop r4-r[4+nnn], r14
+    if ((insn & M_POPN) == I_POPN) {
+      uint8_t n = (insn & 0x07) + 1;
+      bool lr = insn & 0x08;
+      uint32_t* ptr = ptrSP();
+      vSP() += (n + (lr ? 1 : 0)) * 4;
+      checkStackBase();
+      for (uint8_t r = 4; r < 4 + n; ++r) mState[r] = *ptr++;
+      if (lr) mState[R_LR] = *ptr++;
+      continue;
+    }
+
+    // 1011000: Finish
+    if (insn == I_FINISH) {
+      if (mState[R_PC] == 0) {
+        mState[R_PC] = mState[R_LR];
+        // Non-standard change (bug 916106): Prevent the caller from
+        // re-using LR.  Since the caller is by definition not a leaf
+        // routine, it will have to restore LR from somewhere to
+        // return to its own caller, so we can safely zero it here.
+        // This makes a difference only if an error in unwinding
+        // (e.g., caused by starting from within a prologue/epilogue)
+        // causes us to load a pointer to a leaf routine as LR; if we
+        // don't do something, we'll go into an infinite loop of
+        // "returning" to that same function.
+        mState[R_LR] = 0;
+      }
+      return true;
+    }
+
+    // 1001nnnn: Set vsp = r[nnnn]
+    if ((insn & M_MOVSP) == I_MOVSP) {
+      vSP() = mState[insn & 0x0f];
+      checkStack();
+      continue;
+    }
+
+    // 11001000 sssscccc: Pop VFP regs D[16+ssss]-D[16+ssss+cccc] (as FLDMFDD)
+    // 11001001 sssscccc: Pop VFP regs D[ssss]-D[ssss+cccc] (as FLDMFDD)
+    if ((insn & M_POPFDD) == I_POPFDD) {
+      uint8_t n = (next() & 0x0f) + 1;
+      // Note: if the 16+ssss+cccc > 31, the encoding is reserved.
+      // As the space is currently unused, we don't try to check.
+      vSP() += 8 * n;
+      checkStackBase();
+      continue;
+    }
+
+    // 11010nnn: Pop VFP regs D[8]-D[8+nnn] (as FLDMFDD)
+    if ((insn & M_POPFDD8) == I_POPFDD8) {
+      uint8_t n = (insn & 0x07) + 1;
+      vSP() += 8 * n;
+      checkStackBase();
+      continue;
+    }
+
+    // 10110010 uleb128: vsp = vsp + 0x204 + (uleb128 << 2)
+    if (insn == I_ADDSPBIG) {
+      uint32_t acc = 0;
+      uint8_t shift = 0;
+      uint8_t byte;
+      do {
+        if (shift >= 32) return false;
+        byte = next();
+        acc |= (byte & 0x7f) << shift;
+        shift += 7;
+      } while (byte & 0x80);
+      uint32_t offset = 0x204 + (acc << 2);
+      // The calculations above could have overflowed.
+      // But the one we care about is this:
+      if (vSP() + offset < vSP()) mFailed = true;
+      vSP() += offset;
+      // ...so that this is the only other check needed:
+      checkStackBase();
+      continue;
+    }
+
+    // 1000iiii iiiiiiii (i not all 0): Pop under masks {r15-r12}, {r11-r4}
+    if ((insn & M_POPMASK) == I_POPMASK) {
+      popRange(4, 15, ((insn & 0x0f) << 8) | next());
+      continue;
+    }
+
+    // 1011001 0000iiii (i not all 0): Pop under mask {r3-r0}
+    if (insn == I_POPLO) {
+      popRange(0, 3, next() & 0x0f);
+      continue;
+    }
+
+    // 10110011 sssscccc: Pop VFP regs D[ssss]-D[ssss+cccc] (as FLDMFDX)
+    if (insn == I_POPFDX) {
+      uint8_t n = (next() & 0x0f) + 1;
+      vSP() += 8 * n + 4;
+      checkStackBase();
+      continue;
+    }
+
+    // 10111nnn: Pop VFP regs D[8]-D[8+nnn] (as FLDMFDX)
+    if ((insn & M_POPFDX8) == I_POPFDX8) {
+      uint8_t n = (insn & 0x07) + 1;
+      vSP() += 8 * n + 4;
+      checkStackBase();
+      continue;
+    }
+
+    // unhandled instruction
+#ifdef DEBUG_EHABI_UNWIND
+    LOG("Unhandled EHABI instruction 0x%02x", insn);
+#endif
+    mFailed = true;
+  }
+  return false;
+}
+
+bool operator<(const EHTable& lhs, const EHTable& rhs) {
+  return lhs.startPC() < rhs.startPC();
+}
+
+// Async signal unsafe.
+EHAddrSpace::EHAddrSpace(const std::vector<EHTable>& aTables)
+    : mTables(aTables) {
+  std::sort(mTables.begin(), mTables.end());
+  DebugOnly<uint32_t> lastEnd = 0;
+  for (std::vector<EHTable>::iterator i = mTables.begin(); i != mTables.end();
+       ++i) {
+    MOZ_ASSERT(i->startPC() >= lastEnd);
+    mStarts.push_back(i->startPC());
+    lastEnd = i->endPC();
+  }
+}
+
+const EHTable* EHAddrSpace::lookup(uint32_t aPC) const {
+  ptrdiff_t i = (std::upper_bound(mStarts.begin(), mStarts.end(), aPC) -
+                 mStarts.begin()) -
+                1;
+
+  if (i < 0 || aPC >= mTables[i].endPC()) return 0;
+  return &mTables[i];
+}
+
+const EHEntry* EHTable::lookup(uint32_t aPC) const {
+  MOZ_ASSERT(aPC >= mStartPC);
+  if (aPC >= mEndPC) return nullptr;
+
+  const EHEntry* begin = mEntriesBegin;
+  const EHEntry* end = mEntriesEnd;
+  MOZ_ASSERT(begin < end);
+  if (aPC < reinterpret_cast<uint32_t>(begin->startPC.compute()))
+    return nullptr;
+
+  while (end - begin > 1) {
+#ifdef EHABI_UNWIND_MORE_ASSERTS
+    if ((end - 1)->startPC.compute() < begin->startPC.compute()) {
+      MOZ_CRASH("unsorted exidx");
+    }
+#endif
+    const EHEntry* mid = begin + (end - begin) / 2;
+    if (aPC < reinterpret_cast<uint32_t>(mid->startPC.compute()))
+      end = mid;
+    else
+      begin = mid;
+  }
+  return begin;
+}
+
+#if MOZ_LITTLE_ENDIAN()
+static const unsigned char hostEndian = ELFDATA2LSB;
+#elif MOZ_BIG_ENDIAN()
+static const unsigned char hostEndian = ELFDATA2MSB;
+#else
+#  error "No endian?"
+#endif
+
+// Async signal unsafe: std::vector::reserve, std::string copy ctor.
+EHTable::EHTable(const void* aELF, size_t aSize, const std::string& aName)
+    : mStartPC(~0),  // largest uint32_t
+      mEndPC(0),
+      mEntriesBegin(nullptr),
+      mEntriesEnd(nullptr),
+      mName(aName) {
+  const uint32_t fileHeaderAddr = reinterpret_cast<uint32_t>(aELF);
+
+  if (aSize < sizeof(Elf32_Ehdr)) return;
+
+  const Elf32_Ehdr& file = *(reinterpret_cast<Elf32_Ehdr*>(fileHeaderAddr));
+  if (memcmp(&file.e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||
+      file.e_ident[EI_CLASS] != ELFCLASS32 ||
+      file.e_ident[EI_DATA] != hostEndian ||
+      file.e_ident[EI_VERSION] != EV_CURRENT || file.e_machine != EM_ARM ||
+      file.e_version != EV_CURRENT)
+    // e_flags?
+    return;
+
+  MOZ_ASSERT(file.e_phoff + file.e_phnum * file.e_phentsize <= aSize);
+  const Elf32_Phdr *exidxHdr = 0, *zeroHdr = 0;
+  for (unsigned i = 0; i < file.e_phnum; ++i) {
+    const Elf32_Phdr& phdr = *(reinterpret_cast<Elf32_Phdr*>(
+        fileHeaderAddr + file.e_phoff + i * file.e_phentsize));
+    if (phdr.p_type == PT_ARM_EXIDX) {
+      exidxHdr = &phdr;
+    } else if (phdr.p_type == PT_LOAD) {
+      if (phdr.p_offset == 0) {
+        zeroHdr = &phdr;
+      }
+      if (phdr.p_flags & PF_X) {
+        mStartPC = std::min(mStartPC, phdr.p_vaddr);
+        mEndPC = std::max(mEndPC, phdr.p_vaddr + phdr.p_memsz);
+      }
+    }
+  }
+  if (!exidxHdr) return;
+  if (!zeroHdr) return;
+  mBaseAddress = fileHeaderAddr - zeroHdr->p_vaddr;
+  mStartPC += mBaseAddress;
+  mEndPC += mBaseAddress;
+  mEntriesBegin =
+      reinterpret_cast<const EHEntry*>(mBaseAddress + exidxHdr->p_vaddr);
+  mEntriesEnd = reinterpret_cast<const EHEntry*>(
+      mBaseAddress + exidxHdr->p_vaddr + exidxHdr->p_memsz);
+}
+
+mozilla::Atomic<const EHAddrSpace*> EHAddrSpace::sCurrent(nullptr);
+
+// Async signal safe; can fail if Update() hasn't returned yet.
+const EHAddrSpace* EHAddrSpace::Get() { return sCurrent; }
+
+// Collect unwinding information from loaded objects.  Calls after the
+// first have no effect.  Async signal unsafe.
+void EHAddrSpace::Update() {
+  const EHAddrSpace* space = sCurrent;
+  if (space) return;
+
+  SharedLibraryInfo info = SharedLibraryInfo::GetInfoForSelf();
+  std::vector<EHTable> tables;
+
+  for (size_t i = 0; i < info.GetSize(); ++i) {
+    const SharedLibrary& lib = info.GetEntry(i);
+    // FIXME: This isn't correct if the start address isn't p_offset 0, because
+    // the start address will not point at the file header. But this is worked
+    // around by magic number checks in the EHTable constructor.
+    EHTable tab(reinterpret_cast<const void*>(lib.GetStart()),
+                lib.GetEnd() - lib.GetStart(), lib.GetNativeDebugPath());
+    if (tab.isValid()) tables.push_back(tab);
+  }
+  space = new EHAddrSpace(tables);
+
+  if (!sCurrent.compareExchange(nullptr, space)) {
+    delete space;
+    space = sCurrent;
+  }
+}
+
+EHState::EHState(const mcontext_t& context) {
+#ifdef linux
+  mRegs[0] = context.arm_r0;
+  mRegs[1] = context.arm_r1;
+  mRegs[2] = context.arm_r2;
+  mRegs[3] = context.arm_r3;
+  mRegs[4] = context.arm_r4;
+  mRegs[5] = context.arm_r5;
+  mRegs[6] = context.arm_r6;
+  mRegs[7] = context.arm_r7;
+  mRegs[8] = context.arm_r8;
+  mRegs[9] = context.arm_r9;
+  mRegs[10] = context.arm_r10;
+  mRegs[11] = context.arm_fp;
+  mRegs[12] = context.arm_ip;
+  mRegs[13] = context.arm_sp;
+  mRegs[14] = context.arm_lr;
+  mRegs[15] = context.arm_pc;
+#else
+#  error "Unhandled OS for ARM EHABI unwinding"
+#endif
+}
+
+}  // namespace mozilla