michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "ThreadStackHelper.h"
michael@0: #include "MainThreadUtils.h"
michael@0: 
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/Move.h"
michael@0: 
michael@0: #ifdef XP_LINUX
michael@0: #include <unistd.h>
michael@0: #include <sys/syscall.h>
michael@0: #endif
michael@0: 
michael@0: #ifdef ANDROID
michael@0: #ifndef SYS_gettid
michael@0: #define SYS_gettid __NR_gettid
michael@0: #endif
michael@0: #ifndef SYS_tgkill
michael@0: #define SYS_tgkill __NR_tgkill
michael@0: #endif
michael@0: #endif
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: void
michael@0: ThreadStackHelper::Startup()
michael@0: {
michael@0: #if defined(XP_LINUX)
michael@0:   MOZ_ASSERT(NS_IsMainThread());
michael@0:   if (!sInitialized) {
michael@0:     MOZ_ALWAYS_TRUE(!::sem_init(&sSem, 0, 0));
michael@0:   }
michael@0:   sInitialized++;
michael@0: #endif
michael@0: }
michael@0: 
michael@0: void
michael@0: ThreadStackHelper::Shutdown()
michael@0: {
michael@0: #if defined(XP_LINUX)
michael@0:   MOZ_ASSERT(NS_IsMainThread());
michael@0:   if (sInitialized == 1) {
michael@0:     MOZ_ALWAYS_TRUE(!::sem_destroy(&sSem));
michael@0:   }
michael@0:   sInitialized--;
michael@0: #endif
michael@0: }
michael@0: 
michael@0: ThreadStackHelper::ThreadStackHelper()
michael@0:   :
michael@0: #ifdef MOZ_ENABLE_PROFILER_SPS
michael@0:     mPseudoStack(mozilla_get_pseudo_stack()),
michael@0: #endif
michael@0:     mStackBuffer()
michael@0:   , mMaxStackSize(mStackBuffer.capacity())
michael@0: {
michael@0: #if defined(XP_LINUX)
michael@0:   mThreadID = ::syscall(SYS_gettid);
michael@0: #elif defined(XP_WIN)
michael@0:   mInitialized = !!::DuplicateHandle(
michael@0:     ::GetCurrentProcess(), ::GetCurrentThread(),
michael@0:     ::GetCurrentProcess(), &mThreadID,
michael@0:     THREAD_SUSPEND_RESUME, FALSE, 0);
michael@0:   MOZ_ASSERT(mInitialized);
michael@0: #elif defined(XP_MACOSX)
michael@0:   mThreadID = mach_thread_self();
michael@0: #endif
michael@0: }
michael@0: 
michael@0: ThreadStackHelper::~ThreadStackHelper()
michael@0: {
michael@0: #if defined(XP_WIN)
michael@0:   if (mInitialized) {
michael@0:     MOZ_ALWAYS_TRUE(!!::CloseHandle(mThreadID));
michael@0:   }
michael@0: #endif
michael@0: }
michael@0: 
michael@0: #if defined(XP_LINUX) && defined(__arm__)
michael@0: // Some (old) Linux kernels on ARM have a bug where a signal handler
michael@0: // can be called without clearing the IT bits in CPSR first. The result
michael@0: // is that the first few instructions of the handler could be skipped,
michael@0: // ultimately resulting in crashes. To workaround this bug, the handler
michael@0: // on ARM is a trampoline that starts with enough NOP instructions, so
michael@0: // that even if the IT bits are not cleared, only the NOP instructions
michael@0: // will be skipped over.
michael@0: 
michael@0: template <void (*H)(int, siginfo_t*, void*)>
michael@0: __attribute__((naked)) void
michael@0: SignalTrampoline(int aSignal, siginfo_t* aInfo, void* aContext)
michael@0: {
michael@0:   asm volatile (
michael@0:     "nop; nop; nop; nop"
michael@0:     : : : "memory");
michael@0: 
michael@0:   // Because the assembler may generate additional insturctions below, we
michael@0:   // need to ensure NOPs are inserted first by separating them out above.
michael@0: 
michael@0:   asm volatile (
michael@0:     "bx %0"
michael@0:     :
michael@0:     : "r"(H), "l"(aSignal), "l"(aInfo), "l"(aContext)
michael@0:     : "memory");
michael@0: }
michael@0: #endif // XP_LINUX && __arm__
michael@0: 
michael@0: void
michael@0: ThreadStackHelper::GetStack(Stack& aStack)
michael@0: {
michael@0:   // Always run PrepareStackBuffer first to clear aStack
michael@0:   if (!PrepareStackBuffer(aStack)) {
michael@0:     // Skip and return empty aStack
michael@0:     return;
michael@0:   }
michael@0: 
michael@0: #if defined(XP_LINUX)
michael@0:   if (profiler_is_active()) {
michael@0:     // Profiler can interfere with our Linux signal handling
michael@0:     return;
michael@0:   }
michael@0:   if (!sInitialized) {
michael@0:     MOZ_ASSERT(false);
michael@0:     return;
michael@0:   }
michael@0:   sCurrent = this;
michael@0:   struct sigaction sigact = {};
michael@0: #ifdef __arm__
michael@0:   sigact.sa_sigaction = SignalTrampoline<SigAction>;
michael@0: #else
michael@0:   sigact.sa_sigaction = SigAction;
michael@0: #endif
michael@0:   sigemptyset(&sigact.sa_mask);
michael@0:   sigact.sa_flags = SA_SIGINFO | SA_RESTART;
michael@0:   if (::sigaction(SIGPROF, &sigact, &sOldSigAction)) {
michael@0:     MOZ_ASSERT(false);
michael@0:     return;
michael@0:   }
michael@0:   MOZ_ALWAYS_TRUE(!::syscall(SYS_tgkill, getpid(), mThreadID, SIGPROF));
michael@0:   MOZ_ALWAYS_TRUE(!::sem_wait(&sSem));
michael@0: 
michael@0: #elif defined(XP_WIN)
michael@0:   if (!mInitialized) {
michael@0:     MOZ_ASSERT(false);
michael@0:     return;
michael@0:   }
michael@0:   if (::SuspendThread(mThreadID) == DWORD(-1)) {
michael@0:     MOZ_ASSERT(false);
michael@0:     return;
michael@0:   }
michael@0:   FillStackBuffer();
michael@0:   MOZ_ALWAYS_TRUE(::ResumeThread(mThreadID) != DWORD(-1));
michael@0: 
michael@0: #elif defined(XP_MACOSX)
michael@0:   if (::thread_suspend(mThreadID) != KERN_SUCCESS) {
michael@0:     MOZ_ASSERT(false);
michael@0:     return;
michael@0:   }
michael@0:   FillStackBuffer();
michael@0:   MOZ_ALWAYS_TRUE(::thread_resume(mThreadID) == KERN_SUCCESS);
michael@0: 
michael@0: #endif
michael@0:   aStack = Move(mStackBuffer);
michael@0: }
michael@0: 
michael@0: #ifdef XP_LINUX
michael@0: 
michael@0: int ThreadStackHelper::sInitialized;
michael@0: sem_t ThreadStackHelper::sSem;
michael@0: struct sigaction ThreadStackHelper::sOldSigAction;
michael@0: ThreadStackHelper* ThreadStackHelper::sCurrent;
michael@0: 
michael@0: void
michael@0: ThreadStackHelper::SigAction(int aSignal, siginfo_t* aInfo, void* aContext)
michael@0: {
michael@0:   ::sigaction(SIGPROF, &sOldSigAction, nullptr);
michael@0:   sCurrent->FillStackBuffer();
michael@0:   sCurrent = nullptr;
michael@0:   ::sem_post(&sSem);
michael@0: }
michael@0: 
michael@0: #endif // XP_LINUX
michael@0: 
michael@0: bool
michael@0: ThreadStackHelper::PrepareStackBuffer(Stack& aStack) {
michael@0:   // Return false to skip getting the stack and return an empty stack
michael@0:   aStack.clear();
michael@0: #ifdef MOZ_ENABLE_PROFILER_SPS
michael@0:   /* Normally, provided the profiler is enabled, it would be an error if we
michael@0:      don't have a pseudostack here (the thread probably forgot to call
michael@0:      profiler_register_thread). However, on B2G, profiling secondary threads
michael@0:      may be disabled despite profiler being enabled. This is by-design and
michael@0:      is not an error. */
michael@0: #ifdef MOZ_WIDGET_GONK
michael@0:   if (!mPseudoStack) {
michael@0:     return false;
michael@0:   }
michael@0: #endif
michael@0:   MOZ_ASSERT(mPseudoStack);
michael@0:   mStackBuffer.clear();
michael@0:   MOZ_ALWAYS_TRUE(mStackBuffer.reserve(mMaxStackSize));
michael@0:   return true;
michael@0: #else
michael@0:   return false;
michael@0: #endif
michael@0: }
michael@0: 
michael@0: void
michael@0: ThreadStackHelper::FillStackBuffer() {
michael@0: #ifdef MOZ_ENABLE_PROFILER_SPS
michael@0:   size_t reservedSize = mMaxStackSize;
michael@0: 
michael@0:   // Go from front to back
michael@0:   const volatile StackEntry* entry = mPseudoStack->mStack;
michael@0:   const volatile StackEntry* end = entry + mPseudoStack->stackSize();
michael@0:   // Deduplicate identical, consecutive frames
michael@0:   const char* prevLabel = nullptr;
michael@0:   for (; reservedSize-- && entry != end; entry++) {
michael@0:     /* We only accept non-copy labels, because
michael@0:        we are unable to actually copy labels here */
michael@0:     if (entry->isCopyLabel()) {
michael@0:       continue;
michael@0:     }
michael@0:     const char* const label = entry->label();
michael@0:     if (label == prevLabel) {
michael@0:       continue;
michael@0:     }
michael@0:     mStackBuffer.infallibleAppend(label);
michael@0:     prevLabel = label;
michael@0:   }
michael@0:   // If we exited early due to buffer size, expand the buffer for next time
michael@0:   mMaxStackSize += (end - entry);
michael@0: #endif
michael@0: }
michael@0: 
michael@0: } // namespace mozilla