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/*
* Copyright (C) 2017 Apple 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:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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.
*/
#include "config.h"
#include "VMInspector.h"
#include "CodeBlock.h"
#include "CodeBlockSet.h"
#include "HeapInlines.h"
#include <mutex>
#include <wtf/Expected.h>
#if !OS(WINDOWS)
#include <unistd.h>
#endif
namespace JSC {
VMInspector& VMInspector::instance()
{
static VMInspector* manager;
static std::once_flag once;
std::call_once(once, [] {
manager = new VMInspector();
});
return *manager;
}
void VMInspector::add(VM* vm)
{
auto locker = holdLock(m_lock);
m_list.append(vm);
}
void VMInspector::remove(VM* vm)
{
auto locker = holdLock(m_lock);
m_list.remove(vm);
}
auto VMInspector::lock(Seconds timeout) -> Expected<Locker, Error>
{
// This function may be called from a signal handler (e.g. via visit()). Hence,
// it should only use APIs that are safe to call from signal handlers. This is
// why we use unistd.h's sleep() instead of its alternatives.
// We'll be doing sleep(1) between tries below. Hence, sleepPerRetry is 1.
unsigned maxRetries = (timeout < Seconds::infinity()) ? timeout.value() : UINT_MAX;
Expected<Locker, Error> locker = Locker::tryLock(m_lock);
unsigned tryCount = 0;
while (!locker && tryCount < maxRetries) {
// We want the version of sleep from unistd.h. Cast to disambiguate.
#if !OS(WINDOWS)
(static_cast<unsigned (*)(unsigned)>(sleep))(1);
#endif
locker = Locker::tryLock(m_lock);
}
if (!locker)
return makeUnexpected(Error::TimedOut);
return locker;
}
#if ENABLE(JIT)
static bool ensureIsSafeToLock(Lock& lock)
{
unsigned maxRetries = 2;
unsigned tryCount = 0;
while (tryCount <= maxRetries) {
bool success = lock.tryLock();
if (success) {
lock.unlock();
return true;
}
tryCount++;
}
return false;
};
#endif // ENABLE(JIT)
auto VMInspector::isValidExecutableMemory(const VMInspector::Locker&, void* machinePC) -> Expected<bool, Error>
{
#if ENABLE(JIT)
bool found = false;
bool hasTimeout = false;
iterate([&] (VM& vm) -> FunctorStatus {
auto allocator = vm.executableAllocator;
auto& lock = allocator.getLock();
bool isSafeToLock = ensureIsSafeToLock(lock);
if (!isSafeToLock) {
hasTimeout = true;
return FunctorStatus::Continue; // Skip this VM.
}
LockHolder executableAllocatorLocker(lock);
if (allocator.isValidExecutableMemory(executableAllocatorLocker, machinePC)) {
found = true;
return FunctorStatus::Done;
}
return FunctorStatus::Continue;
});
if (!found && hasTimeout)
return makeUnexpected(Error::TimedOut);
return found;
#else
UNUSED_PARAM(machinePC);
return false;
#endif
}
auto VMInspector::codeBlockForMachinePC(const VMInspector::Locker&, void* machinePC) -> Expected<CodeBlock*, Error>
{
#if ENABLE(JIT)
CodeBlock* codeBlock = nullptr;
bool hasTimeout = false;
iterate([&] (VM& vm) {
if (!vm.apiLock().currentThreadIsHoldingLock())
return FunctorStatus::Continue;
// It is safe to call Heap::forEachCodeBlockIgnoringJITPlans here because:
// 1. CodeBlocks are added to the CodeBlockSet from the main thread before
// they are handed to the JIT plans. Those codeBlocks will have a null jitCode,
// but we check for that in our lambda functor.
// 2. CodeBlockSet::iterate() will acquire the CodeBlockSet lock before iterating.
// This ensures that a CodeBlock won't be GCed while we're iterating.
// 3. We do a tryLock on the CodeBlockSet's lock first to ensure that it is
// safe for the current thread to lock it before calling
// Heap::forEachCodeBlockIgnoringJITPlans(). Hence, there's no risk of
// re-entering the lock and deadlocking on it.
auto& lock = vm.heap.codeBlockSet().getLock();
bool isSafeToLock = ensureIsSafeToLock(lock);
if (!isSafeToLock) {
hasTimeout = true;
return FunctorStatus::Continue; // Skip this VM.
}
vm.heap.forEachCodeBlockIgnoringJITPlans([&] (CodeBlock* cb) {
JITCode* jitCode = cb->jitCode().get();
if (!jitCode) {
// If the codeBlock is a replacement codeBlock which is in the process of being
// compiled, its jitCode will be null, and we can disregard it as a match for
// the machinePC we're searching for.
return false;
}
if (!JITCode::isJIT(jitCode->jitType()))
return false;
if (jitCode->contains(machinePC)) {
codeBlock = cb;
return true;
}
return false;
});
if (codeBlock)
return FunctorStatus::Done;
return FunctorStatus::Continue;
});
if (!codeBlock && hasTimeout)
return makeUnexpected(Error::TimedOut);
return codeBlock;
#else
UNUSED_PARAM(machinePC);
return nullptr;
#endif
}
} // namespace JSC
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