Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 438 insertions, 0 deletions

diff --git a/js/src/wasm/WasmProcess.cpp b/js/src/wasm/WasmProcess.cpp
new file mode 100644
index 0000000000..9b8121ceec
--- /dev/null
+++ b/js/src/wasm/WasmProcess.cpp
@@ -0,0 +1,438 @@
+/* -*- 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 2017 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "wasm/WasmProcess.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/BinarySearch.h"
+#include "mozilla/ScopeExit.h"
+
+#include "gc/Memory.h"
+#include "threading/ExclusiveData.h"
+#include "vm/MutexIDs.h"
+#include "vm/Runtime.h"
+#include "wasm/WasmBuiltins.h"
+#include "wasm/WasmCode.h"
+#include "wasm/WasmInstance.h"
+
+using namespace js;
+using namespace wasm;
+
+using mozilla::BinarySearchIf;
+
+// Per-process map from values of program-counter (pc) to CodeSegments.
+//
+// Whenever a new CodeSegment is ready to use, it has to be registered so that
+// we can have fast lookups from pc to CodeSegments in numerous places. Since
+// wasm compilation may be tiered, and the second tier doesn't have access to
+// any JSContext/JS::Compartment/etc lying around, we have to use a process-wide
+// map instead.
+
+using CodeSegmentVector = Vector<const CodeSegment*, 0, SystemAllocPolicy>;
+
+Atomic<bool> wasm::CodeExists(false);
+
+// Because of profiling, the thread running wasm might need to know to which
+// CodeSegment the current PC belongs, during a call to lookup(). A lookup
+// is a read-only operation, and we don't want to take a lock then
+// (otherwise, we could have a deadlock situation if an async lookup
+// happened on a given thread that was holding mutatorsMutex_ while getting
+// sampled). Since the writer could be modifying the data that is getting
+// looked up, the writer functions use spin-locks to know if there are any
+// observers (i.e. calls to lookup()) of the atomic data.
+
+static Atomic<size_t> sNumActiveLookups(0);
+
+class ProcessCodeSegmentMap {
+  // Since writes (insertions or removals) can happen on any background
+  // thread at the same time, we need a lock here.
+
+  Mutex mutatorsMutex_ MOZ_UNANNOTATED;
+
+  CodeSegmentVector segments1_;
+  CodeSegmentVector segments2_;
+
+  // Except during swapAndWait(), there are no lookup() observers of the
+  // vector pointed to by mutableCodeSegments_
+
+  CodeSegmentVector* mutableCodeSegments_;
+  Atomic<const CodeSegmentVector*> readonlyCodeSegments_;
+
+  struct CodeSegmentPC {
+    const void* pc;
+    explicit CodeSegmentPC(const void* pc) : pc(pc) {}
+    int operator()(const CodeSegment* cs) const {
+      if (cs->containsCodePC(pc)) {
+        return 0;
+      }
+      if (pc < cs->base()) {
+        return -1;
+      }
+      return 1;
+    }
+  };
+
+  void swapAndWait() {
+    // Both vectors are consistent for lookup at this point although their
+    // contents are different: there is no way for the looked up PC to be
+    // in the code segment that is getting registered, because the code
+    // segment is not even fully created yet.
+
+    // If a lookup happens before this instruction, then the
+    // soon-to-become-former read-only pointer is used during the lookup,
+    // which is valid.
+
+    mutableCodeSegments_ = const_cast<CodeSegmentVector*>(
+        readonlyCodeSegments_.exchange(mutableCodeSegments_));
+
+    // If a lookup happens after this instruction, then the updated vector
+    // is used, which is valid:
+    // - in case of insertion, it means the new vector contains more data,
+    // but it's fine since the code segment is getting registered and thus
+    // isn't even fully created yet, so the code can't be running.
+    // - in case of removal, it means the new vector contains one less
+    // entry, but it's fine since unregistering means the code segment
+    // isn't used by any live instance anymore, thus PC can't be in the
+    // to-be-removed code segment's range.
+
+    // A lookup could have happened on any of the two vectors. Wait for
+    // observers to be done using any vector before mutating.
+
+    while (sNumActiveLookups > 0) {
+    }
+  }
+
+ public:
+  ProcessCodeSegmentMap()
+      : mutatorsMutex_(mutexid::WasmCodeSegmentMap),
+        mutableCodeSegments_(&segments1_),
+        readonlyCodeSegments_(&segments2_) {}
+
+  ~ProcessCodeSegmentMap() {
+    MOZ_RELEASE_ASSERT(sNumActiveLookups == 0);
+    MOZ_ASSERT(segments1_.empty());
+    MOZ_ASSERT(segments2_.empty());
+    segments1_.clearAndFree();
+    segments2_.clearAndFree();
+  }
+
+  bool insert(const CodeSegment* cs) {
+    LockGuard<Mutex> lock(mutatorsMutex_);
+
+    size_t index;
+    MOZ_ALWAYS_FALSE(BinarySearchIf(*mutableCodeSegments_, 0,
+                                    mutableCodeSegments_->length(),
+                                    CodeSegmentPC(cs->base()), &index));
+
+    if (!mutableCodeSegments_->insert(mutableCodeSegments_->begin() + index,
+                                      cs)) {
+      return false;
+    }
+
+    CodeExists = true;
+
+    swapAndWait();
+
+#ifdef DEBUG
+    size_t otherIndex;
+    MOZ_ALWAYS_FALSE(BinarySearchIf(*mutableCodeSegments_, 0,
+                                    mutableCodeSegments_->length(),
+                                    CodeSegmentPC(cs->base()), &otherIndex));
+    MOZ_ASSERT(index == otherIndex);
+#endif
+
+    // Although we could simply revert the insertion in the read-only
+    // vector, it is simpler to just crash and given that each CodeSegment
+    // consumes multiple pages, it is unlikely this insert() would OOM in
+    // practice
+    AutoEnterOOMUnsafeRegion oom;
+    if (!mutableCodeSegments_->insert(mutableCodeSegments_->begin() + index,
+                                      cs)) {
+      oom.crash("when inserting a CodeSegment in the process-wide map");
+    }
+
+    return true;
+  }
+
+  void remove(const CodeSegment* cs) {
+    LockGuard<Mutex> lock(mutatorsMutex_);
+
+    size_t index;
+    MOZ_ALWAYS_TRUE(BinarySearchIf(*mutableCodeSegments_, 0,
+                                   mutableCodeSegments_->length(),
+                                   CodeSegmentPC(cs->base()), &index));
+
+    mutableCodeSegments_->erase(mutableCodeSegments_->begin() + index);
+
+    if (!mutableCodeSegments_->length()) {
+      CodeExists = false;
+    }
+
+    swapAndWait();
+
+#ifdef DEBUG
+    size_t otherIndex;
+    MOZ_ALWAYS_TRUE(BinarySearchIf(*mutableCodeSegments_, 0,
+                                   mutableCodeSegments_->length(),
+                                   CodeSegmentPC(cs->base()), &otherIndex));
+    MOZ_ASSERT(index == otherIndex);
+#endif
+
+    mutableCodeSegments_->erase(mutableCodeSegments_->begin() + index);
+  }
+
+  const CodeSegment* lookup(const void* pc) {
+    const CodeSegmentVector* readonly = readonlyCodeSegments_;
+
+    size_t index;
+    if (!BinarySearchIf(*readonly, 0, readonly->length(), CodeSegmentPC(pc),
+                        &index)) {
+      return nullptr;
+    }
+
+    // It is fine returning a raw CodeSegment*, because we assume we are
+    // looking up a live PC in code which is on the stack, keeping the
+    // CodeSegment alive.
+
+    return (*readonly)[index];
+  }
+};
+
+// This field is only atomic to handle buggy scenarios where we crash during
+// startup or shutdown and thus racily perform wasm::LookupCodeSegment() from
+// the crashing thread.
+
+static Atomic<ProcessCodeSegmentMap*> sProcessCodeSegmentMap(nullptr);
+
+bool wasm::RegisterCodeSegment(const CodeSegment* cs) {
+  MOZ_ASSERT(cs->codeTier().code().initialized());
+
+  // This function cannot race with startup/shutdown.
+  ProcessCodeSegmentMap* map = sProcessCodeSegmentMap;
+  MOZ_RELEASE_ASSERT(map);
+  return map->insert(cs);
+}
+
+void wasm::UnregisterCodeSegment(const CodeSegment* cs) {
+  // This function cannot race with startup/shutdown.
+  ProcessCodeSegmentMap* map = sProcessCodeSegmentMap;
+  MOZ_RELEASE_ASSERT(map);
+  map->remove(cs);
+}
+
+const CodeSegment* wasm::LookupCodeSegment(
+    const void* pc, const CodeRange** codeRange /*= nullptr */) {
+  // Since wasm::LookupCodeSegment() can race with wasm::ShutDown(), we must
+  // additionally keep sNumActiveLookups above zero for the duration we're
+  // using the ProcessCodeSegmentMap. wasm::ShutDown() spin-waits on
+  // sNumActiveLookups getting to zero.
+
+  auto decObserver = mozilla::MakeScopeExit([&] {
+    MOZ_ASSERT(sNumActiveLookups > 0);
+    sNumActiveLookups--;
+  });
+  sNumActiveLookups++;
+
+  ProcessCodeSegmentMap* map = sProcessCodeSegmentMap;
+  if (!map) {
+    return nullptr;
+  }
+
+  if (const CodeSegment* found = map->lookup(pc)) {
+    if (codeRange) {
+      *codeRange = found->isModule() ? found->asModule()->lookupRange(pc)
+                                     : found->asLazyStub()->lookupRange(pc);
+    }
+    return found;
+  }
+
+  if (codeRange) {
+    *codeRange = nullptr;
+  }
+
+  return nullptr;
+}
+
+const Code* wasm::LookupCode(const void* pc,
+                             const CodeRange** codeRange /* = nullptr */) {
+  const CodeSegment* found = LookupCodeSegment(pc, codeRange);
+  MOZ_ASSERT_IF(!found && codeRange, !*codeRange);
+  return found ? &found->code() : nullptr;
+}
+
+bool wasm::InCompiledCode(void* pc) {
+  if (LookupCodeSegment(pc)) {
+    return true;
+  }
+
+  const CodeRange* codeRange;
+  uint8_t* codeBase;
+  return LookupBuiltinThunk(pc, &codeRange, &codeBase);
+}
+
+/**
+ * ReadLockFlag maintains a flag that can be mutated multiple times before it
+ * is read, at which point it maintains the same value.
+ */
+class ReadLockFlag {
+ private:
+  bool enabled_;
+  bool read_;
+
+ public:
+  ReadLockFlag() : enabled_(false), read_(false) {}
+
+  bool get() {
+    read_ = true;
+    return enabled_;
+  }
+
+  bool set(bool enabled) {
+    if (read_) {
+      return false;
+    }
+    enabled_ = enabled;
+    return true;
+  }
+};
+
+#ifdef WASM_SUPPORTS_HUGE_MEMORY
+/*
+ * Some 64 bit systems greatly limit the range of available virtual memory. We
+ * require about 6GiB for each wasm huge memory, which can exhaust the address
+ * spaces of these systems quickly. In order to avoid this, we only enable huge
+ * memory if we observe a large enough address space.
+ *
+ * This number is conservatively chosen to continue using huge memory on our
+ * smallest address space system, Android on ARM64 (39 bits), along with a bit
+ * for error in detecting the address space limit.
+ */
+static const size_t MinAddressBitsForHugeMemory = 38;
+
+/*
+ * In addition to the above, some systems impose an independent limit on the
+ * amount of virtual memory that may be used.
+ */
+static const size_t MinVirtualMemoryLimitForHugeMemory =
+    size_t(1) << MinAddressBitsForHugeMemory;
+#endif
+
+ExclusiveData<ReadLockFlag> sHugeMemoryEnabled32(
+    mutexid::WasmHugeMemoryEnabled);
+ExclusiveData<ReadLockFlag> sHugeMemoryEnabled64(
+    mutexid::WasmHugeMemoryEnabled);
+
+static MOZ_NEVER_INLINE bool IsHugeMemoryEnabledHelper32() {
+  auto state = sHugeMemoryEnabled32.lock();
+  return state->get();
+}
+
+static MOZ_NEVER_INLINE bool IsHugeMemoryEnabledHelper64() {
+  auto state = sHugeMemoryEnabled64.lock();
+  return state->get();
+}
+
+bool wasm::IsHugeMemoryEnabled(wasm::IndexType t) {
+  if (t == IndexType::I32) {
+    static bool enabled32 = IsHugeMemoryEnabledHelper32();
+    return enabled32;
+  }
+  static bool enabled64 = IsHugeMemoryEnabledHelper64();
+  return enabled64;
+}
+
+bool wasm::DisableHugeMemory() {
+  bool ok = true;
+  {
+    auto state = sHugeMemoryEnabled64.lock();
+    ok = ok && state->set(false);
+  }
+  {
+    auto state = sHugeMemoryEnabled32.lock();
+    ok = ok && state->set(false);
+  }
+  return ok;
+}
+
+void ConfigureHugeMemory() {
+#ifdef WASM_SUPPORTS_HUGE_MEMORY
+  bool ok = true;
+
+  {
+    // Currently no huge memory for IndexType::I64, so always set to false.
+    auto state = sHugeMemoryEnabled64.lock();
+    ok = ok && state->set(false);
+  }
+
+  if (gc::SystemAddressBits() < MinAddressBitsForHugeMemory) {
+    return;
+  }
+
+  if (gc::VirtualMemoryLimit() != size_t(-1) &&
+      gc::VirtualMemoryLimit() < MinVirtualMemoryLimitForHugeMemory) {
+    return;
+  }
+
+  {
+    auto state = sHugeMemoryEnabled32.lock();
+    ok = ok && state->set(true);
+  }
+
+  MOZ_RELEASE_ASSERT(ok);
+#endif
+}
+
+bool wasm::Init() {
+  MOZ_RELEASE_ASSERT(!sProcessCodeSegmentMap);
+
+  uintptr_t pageSize = gc::SystemPageSize();
+  MOZ_RELEASE_ASSERT(wasm::NullPtrGuardSize <= pageSize);
+
+  ConfigureHugeMemory();
+
+  AutoEnterOOMUnsafeRegion oomUnsafe;
+  ProcessCodeSegmentMap* map = js_new<ProcessCodeSegmentMap>();
+  if (!map) {
+    oomUnsafe.crash("js::wasm::Init");
+  }
+
+  sProcessCodeSegmentMap = map;
+  return true;
+}
+
+void wasm::ShutDown() {
+  // If there are live runtimes then we are already pretty much leaking the
+  // world, so to avoid spurious assertions (which are valid and valuable when
+  // there are not live JSRuntimes), don't bother releasing anything here.
+  if (JSRuntime::hasLiveRuntimes()) {
+    return;
+  }
+
+  PurgeCanonicalTypes();
+
+  // After signalling shutdown by clearing sProcessCodeSegmentMap, wait for
+  // concurrent wasm::LookupCodeSegment()s to finish.
+  ProcessCodeSegmentMap* map = sProcessCodeSegmentMap;
+  MOZ_RELEASE_ASSERT(map);
+  sProcessCodeSegmentMap = nullptr;
+  while (sNumActiveLookups > 0) {
+  }
+
+  ReleaseBuiltinThunks();
+  js_delete(map);
+}