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Diffstat (limited to 'mozglue/baseprofiler/core/platform-linux-android.cpp')
| -rw-r--r-- | mozglue/baseprofiler/core/platform-linux-android.cpp | 507 |
1 files changed, 507 insertions, 0 deletions
diff --git a/mozglue/baseprofiler/core/platform-linux-android.cpp b/mozglue/baseprofiler/core/platform-linux-android.cpp new file mode 100644 index 0000000000..7921d9f4fd --- /dev/null +++ b/mozglue/baseprofiler/core/platform-linux-android.cpp @@ -0,0 +1,507 @@ +/* -*- 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 The Chromium Authors. 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 used for both Linux and Android. + +#include <stdio.h> +#include <math.h> + +#include <pthread.h> +#if defined(GP_OS_freebsd) +# include <sys/thr.h> +#endif +#include <semaphore.h> +#include <signal.h> +#include <sys/time.h> +#include <sys/resource.h> +#include <sys/syscall.h> +#include <sys/types.h> +#include <stdlib.h> +#include <sched.h> +#include <ucontext.h> +// Ubuntu Dapper requires memory pages to be marked as +// executable. Otherwise, OS raises an exception when executing code +// in that page. +#include <sys/types.h> // mmap & munmap +#include <sys/mman.h> // mmap & munmap +#include <sys/stat.h> // open +#include <fcntl.h> // open +#include <unistd.h> // sysconf +#include <semaphore.h> +#ifdef __GLIBC__ +# include <execinfo.h> // backtrace, backtrace_symbols +#endif // def __GLIBC__ +#include <strings.h> // index +#include <errno.h> +#include <stdarg.h> + +#include "prenv.h" +#include "mozilla/PodOperations.h" +#include "mozilla/DebugOnly.h" + +#include <string.h> +#include <list> + +using namespace mozilla; + +namespace mozilla { +namespace baseprofiler { + +static int64_t MicrosecondsSince1970() { + struct timeval tv; + gettimeofday(&tv, NULL); + return int64_t(tv.tv_sec) * 1000000 + int64_t(tv.tv_usec); +} + +void* GetStackTop(void* aGuess) { return aGuess; } + +static void PopulateRegsFromContext(Registers& aRegs, ucontext_t* aContext) { + aRegs.mContext = aContext; + mcontext_t& mcontext = aContext->uc_mcontext; + + // Extracting the sample from the context is extremely machine dependent. +#if defined(GP_PLAT_x86_linux) || defined(GP_PLAT_x86_android) + aRegs.mPC = reinterpret_cast<Address>(mcontext.gregs[REG_EIP]); + aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[REG_ESP]); + aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[REG_EBP]); + aRegs.mLR = 0; +#elif defined(GP_PLAT_amd64_linux) || defined(GP_PLAT_amd64_android) + aRegs.mPC = reinterpret_cast<Address>(mcontext.gregs[REG_RIP]); + aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[REG_RSP]); + aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[REG_RBP]); + aRegs.mLR = 0; +#elif defined(GP_PLAT_amd64_freebsd) + aRegs.mPC = reinterpret_cast<Address>(mcontext.mc_rip); + aRegs.mSP = reinterpret_cast<Address>(mcontext.mc_rsp); + aRegs.mFP = reinterpret_cast<Address>(mcontext.mc_rbp); + aRegs.mLR = 0; +#elif defined(GP_PLAT_arm_linux) || defined(GP_PLAT_arm_android) + aRegs.mPC = reinterpret_cast<Address>(mcontext.arm_pc); + aRegs.mSP = reinterpret_cast<Address>(mcontext.arm_sp); + aRegs.mFP = reinterpret_cast<Address>(mcontext.arm_fp); + aRegs.mLR = reinterpret_cast<Address>(mcontext.arm_lr); +#elif defined(GP_PLAT_arm64_linux) || defined(GP_PLAT_arm64_android) + aRegs.mPC = reinterpret_cast<Address>(mcontext.pc); + aRegs.mSP = reinterpret_cast<Address>(mcontext.sp); + aRegs.mFP = reinterpret_cast<Address>(mcontext.regs[29]); + aRegs.mLR = reinterpret_cast<Address>(mcontext.regs[30]); +#elif defined(GP_PLAT_arm64_freebsd) + aRegs.mPC = reinterpret_cast<Address>(mcontext.mc_gpregs.gp_elr); + aRegs.mSP = reinterpret_cast<Address>(mcontext.mc_gpregs.gp_sp); + aRegs.mFP = reinterpret_cast<Address>(mcontext.mc_gpregs.gp_x[29]); + aRegs.mLR = reinterpret_cast<Address>(mcontext.mc_gpregs.gp_lr); +#elif defined(GP_PLAT_mips64_linux) || defined(GP_PLAT_mips64_android) + aRegs.mPC = reinterpret_cast<Address>(mcontext.pc); + aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[29]); + aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[30]); + +#else +# error "bad platform" +#endif +} + +#if defined(GP_OS_android) +# define SYS_tgkill __NR_tgkill +#endif + +#if defined(GP_OS_linux) || defined(GP_OS_android) +int tgkill(pid_t tgid, pid_t tid, int signalno) { + return syscall(SYS_tgkill, tgid, tid, signalno); +} +#endif + +#if defined(GP_OS_freebsd) +# define tgkill thr_kill2 +#endif + +class PlatformData { + public: + explicit PlatformData(BaseProfilerThreadId aThreadId) {} + + ~PlatformData() {} +}; + +//////////////////////////////////////////////////////////////////////// +// BEGIN Sampler target specifics + +// The only way to reliably interrupt a Linux thread and inspect its register +// and stack state is by sending a signal to it, and doing the work inside the +// signal handler. But we don't want to run much code inside the signal +// handler, since POSIX severely restricts what we can do in signal handlers. +// So we use a system of semaphores to suspend the thread and allow the +// sampler thread to do all the work of unwinding and copying out whatever +// data it wants. +// +// A four-message protocol is used to reliably suspend and later resume the +// thread to be sampled (the samplee): +// +// Sampler (signal sender) thread Samplee (thread to be sampled) +// +// Prepare the SigHandlerCoordinator +// and point sSigHandlerCoordinator at it +// +// send SIGPROF to samplee ------- MSG 1 ----> (enter signal handler) +// wait(mMessage2) Copy register state +// into sSigHandlerCoordinator +// <------ MSG 2 ----- post(mMessage2) +// Samplee is now suspended. wait(mMessage3) +// Examine its stack/register +// state at leisure +// +// Release samplee: +// post(mMessage3) ------- MSG 3 -----> +// wait(mMessage4) Samplee now resumes. Tell +// the sampler that we are done. +// <------ MSG 4 ------ post(mMessage4) +// Now we know the samplee's signal (leave signal handler) +// handler has finished using +// sSigHandlerCoordinator. We can +// safely reuse it for some other thread. +// + +// A type used to coordinate between the sampler (signal sending) thread and +// the thread currently being sampled (the samplee, which receives the +// signals). +// +// The first message is sent using a SIGPROF signal delivery. The subsequent +// three are sent using sem_wait/sem_post pairs. They are named accordingly +// in the following struct. +struct SigHandlerCoordinator { + SigHandlerCoordinator() { + PodZero(&mUContext); + int r = sem_init(&mMessage2, /* pshared */ 0, 0); + r |= sem_init(&mMessage3, /* pshared */ 0, 0); + r |= sem_init(&mMessage4, /* pshared */ 0, 0); + MOZ_ASSERT(r == 0); + (void)r; + } + + ~SigHandlerCoordinator() { + int r = sem_destroy(&mMessage2); + r |= sem_destroy(&mMessage3); + r |= sem_destroy(&mMessage4); + MOZ_ASSERT(r == 0); + (void)r; + } + + sem_t mMessage2; // To sampler: "context is in sSigHandlerCoordinator" + sem_t mMessage3; // To samplee: "resume" + sem_t mMessage4; // To sampler: "finished with sSigHandlerCoordinator" + ucontext_t mUContext; // Context at signal +}; + +struct SigHandlerCoordinator* Sampler::sSigHandlerCoordinator = nullptr; + +static void SigprofHandler(int aSignal, siginfo_t* aInfo, void* aContext) { + // Avoid TSan warning about clobbering errno. + int savedErrno = errno; + + MOZ_ASSERT(aSignal == SIGPROF); + MOZ_ASSERT(Sampler::sSigHandlerCoordinator); + + // By sending us this signal, the sampler thread has sent us message 1 in + // the comment above, with the meaning "|sSigHandlerCoordinator| is ready + // for use, please copy your register context into it." + Sampler::sSigHandlerCoordinator->mUContext = + *static_cast<ucontext_t*>(aContext); + + // Send message 2: tell the sampler thread that the context has been copied + // into |sSigHandlerCoordinator->mUContext|. sem_post can never fail by + // being interrupted by a signal, so there's no loop around this call. + int r = sem_post(&Sampler::sSigHandlerCoordinator->mMessage2); + MOZ_ASSERT(r == 0); + + // At this point, the sampler thread assumes we are suspended, so we must + // not touch any global state here. + + // Wait for message 3: the sampler thread tells us to resume. + while (true) { + r = sem_wait(&Sampler::sSigHandlerCoordinator->mMessage3); + if (r == -1 && errno == EINTR) { + // Interrupted by a signal. Try again. + continue; + } + // We don't expect any other kind of failure + MOZ_ASSERT(r == 0); + break; + } + + // Send message 4: tell the sampler thread that we are finished accessing + // |sSigHandlerCoordinator|. After this point it is not safe to touch + // |sSigHandlerCoordinator|. + r = sem_post(&Sampler::sSigHandlerCoordinator->mMessage4); + MOZ_ASSERT(r == 0); + + errno = savedErrno; +} + +Sampler::Sampler(PSLockRef aLock) : mMyPid(profiler_current_process_id()) { +#if defined(USE_EHABI_STACKWALK) + EHABIStackWalkInit(); +#endif + + // NOTE: We don't initialize LUL here, instead initializing it in + // SamplerThread's constructor. This is because with the + // profiler_suspend_and_sample_thread entry point, we want to be able to + // sample without waiting for LUL to be initialized. + + // Request profiling signals. + struct sigaction sa; + sa.sa_sigaction = SigprofHandler; + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART | SA_SIGINFO; + if (sigaction(SIGPROF, &sa, &mOldSigprofHandler) != 0) { + MOZ_CRASH("Error installing SIGPROF handler in the profiler"); + } +} + +void Sampler::Disable(PSLockRef aLock) { + // Restore old signal handler. This is global state so it's important that + // we do it now, while gPSMutex is locked. + sigaction(SIGPROF, &mOldSigprofHandler, 0); +} + +template <typename Func> +void Sampler::SuspendAndSampleAndResumeThread( + PSLockRef aLock, const RegisteredThread& aRegisteredThread, + const TimeStamp& aNow, const Func& aProcessRegs) { + // Only one sampler thread can be sampling at once. So we expect to have + // complete control over |sSigHandlerCoordinator|. + MOZ_ASSERT(!sSigHandlerCoordinator); + + if (!mSamplerTid.IsSpecified()) { + mSamplerTid = profiler_current_thread_id(); + } + BaseProfilerThreadId sampleeTid = aRegisteredThread.Info()->ThreadId(); + MOZ_RELEASE_ASSERT(sampleeTid != mSamplerTid); + + //----------------------------------------------------------------// + // Suspend the samplee thread and get its context. + + SigHandlerCoordinator coord; // on sampler thread's stack + sSigHandlerCoordinator = &coord; + + // Send message 1 to the samplee (the thread to be sampled), by + // signalling at it. + // This could fail if the thread doesn't exist anymore. + int r = tgkill(mMyPid.ToNumber(), sampleeTid.ToNumber(), SIGPROF); + if (r == 0) { + // Wait for message 2 from the samplee, indicating that the context + // is available and that the thread is suspended. + while (true) { + r = sem_wait(&sSigHandlerCoordinator->mMessage2); + if (r == -1 && errno == EINTR) { + // Interrupted by a signal. Try again. + continue; + } + // We don't expect any other kind of failure. + MOZ_ASSERT(r == 0); + break; + } + + //----------------------------------------------------------------// + // Sample the target thread. + + // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING + // + // The profiler's "critical section" begins here. In the critical section, + // we must not do any dynamic memory allocation, nor try to acquire any lock + // or any other unshareable resource. This is because the thread to be + // sampled has been suspended at some entirely arbitrary point, and we have + // no idea which unsharable resources (locks, essentially) it holds. So any + // attempt to acquire any lock, including the implied locks used by the + // malloc implementation, risks deadlock. This includes TimeStamp::Now(), + // which gets a lock on Windows. + + // The samplee thread is now frozen and sSigHandlerCoordinator->mUContext is + // valid. We can poke around in it and unwind its stack as we like. + + // Extract the current register values. + Registers regs; + PopulateRegsFromContext(regs, &sSigHandlerCoordinator->mUContext); + aProcessRegs(regs, aNow); + + //----------------------------------------------------------------// + // Resume the target thread. + + // Send message 3 to the samplee, which tells it to resume. + r = sem_post(&sSigHandlerCoordinator->mMessage3); + MOZ_ASSERT(r == 0); + + // Wait for message 4 from the samplee, which tells us that it has + // finished with |sSigHandlerCoordinator|. + while (true) { + r = sem_wait(&sSigHandlerCoordinator->mMessage4); + if (r == -1 && errno == EINTR) { + continue; + } + MOZ_ASSERT(r == 0); + break; + } + + // The profiler's critical section ends here. After this point, none of the + // critical section limitations documented above apply. + // + // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING + } + + // This isn't strictly necessary, but doing so does help pick up anomalies + // in which the signal handler is running when it shouldn't be. + sSigHandlerCoordinator = nullptr; +} + +// END Sampler target specifics +//////////////////////////////////////////////////////////////////////// + +//////////////////////////////////////////////////////////////////////// +// BEGIN SamplerThread target specifics + +static void* ThreadEntry(void* aArg) { + auto thread = static_cast<SamplerThread*>(aArg); + thread->Run(); + return nullptr; +} + +SamplerThread::SamplerThread(PSLockRef aLock, uint32_t aActivityGeneration, + double aIntervalMilliseconds, uint32_t aFeatures) + : mSampler(aLock), + mActivityGeneration(aActivityGeneration), + mIntervalMicroseconds( + std::max(1, int(floor(aIntervalMilliseconds * 1000 + 0.5)))) { +#if defined(USE_LUL_STACKWALK) + lul::LUL* lul = CorePS::Lul(aLock); + if (!lul && ProfilerFeature::HasStackWalkEnabled(aFeatures)) { + CorePS::SetLul(aLock, MakeUnique<lul::LUL>(logging_sink_for_LUL)); + // Read all the unwind info currently available. + lul = CorePS::Lul(aLock); + read_procmaps(lul); + + // Switch into unwind mode. After this point, we can't add or remove any + // unwind info to/from this LUL instance. The only thing we can do with + // it is Unwind() calls. + lul->EnableUnwinding(); + + // Has a test been requested? + if (getenv("MOZ_PROFILER_LUL_TEST")) { + int nTests = 0, nTestsPassed = 0; + RunLulUnitTests(&nTests, &nTestsPassed, lul); + } + } +#endif + + // Start the sampling thread. It repeatedly sends a SIGPROF signal. Sending + // the signal ourselves instead of relying on itimer provides much better + // accuracy. + if (pthread_create(&mThread, nullptr, ThreadEntry, this) != 0) { + MOZ_CRASH("pthread_create failed"); + } +} + +SamplerThread::~SamplerThread() { pthread_join(mThread, nullptr); } + +void SamplerThread::SleepMicro(uint32_t aMicroseconds) { + if (aMicroseconds >= 1000000) { + // Use usleep for larger intervals, because the nanosleep + // code below only supports intervals < 1 second. + MOZ_ALWAYS_TRUE(!::usleep(aMicroseconds)); + return; + } + + struct timespec ts; + ts.tv_sec = 0; + ts.tv_nsec = aMicroseconds * 1000UL; + + int rv = ::nanosleep(&ts, &ts); + + while (rv != 0 && errno == EINTR) { + // Keep waiting in case of interrupt. + // nanosleep puts the remaining time back into ts. + rv = ::nanosleep(&ts, &ts); + } + + MOZ_ASSERT(!rv, "nanosleep call failed"); +} + +void SamplerThread::Stop(PSLockRef aLock) { + // Restore old signal handler. This is global state so it's important that + // we do it now, while gPSMutex is locked. It's safe to do this now even + // though this SamplerThread is still alive, because the next time the main + // loop of Run() iterates it won't get past the mActivityGeneration check, + // and so won't send any signals. + mSampler.Disable(aLock); +} + +// END SamplerThread target specifics +//////////////////////////////////////////////////////////////////////// + +#if defined(GP_OS_linux) || defined(GP_OS_freebsd) + +// We use pthread_atfork() to temporarily disable signal delivery during any +// fork() call. Without that, fork() can be repeatedly interrupted by signal +// delivery, requiring it to be repeatedly restarted, which can lead to *long* +// delays. See bug 837390. +// +// We provide no paf_child() function to run in the child after forking. This +// is fine because we always immediately exec() after fork(), and exec() +// clobbers all process state. Also, we don't want the sampler to resume in the +// child process between fork() and exec(), it would be wasteful. +// +// Unfortunately all this is only doable on non-Android because Bionic doesn't +// have pthread_atfork. + +// In the parent, before the fork, increase gSkipSampling to ensure that +// profiler sampling loops will be skipped. There could be one in progress now, +// causing a small delay, but further sampling will be skipped, allowing `fork` +// to complete. +static void paf_prepare() { ++gSkipSampling; } + +// In the parent, after the fork, decrease gSkipSampling to let the sampler +// resume sampling (unless other places have made it non-zero as well). +static void paf_parent() { --gSkipSampling; } + +static void PlatformInit(PSLockRef aLock) { + // Set up the fork handlers. + pthread_atfork(paf_prepare, paf_parent, nullptr); +} + +#else + +static void PlatformInit(PSLockRef aLock) {} + +#endif + +#if defined(HAVE_NATIVE_UNWIND) +// TODO port getcontext from breakpad, if profiler_get_backtrace is needed. +# define REGISTERS_SYNC_POPULATE(regs) \ + MOZ_CRASH("profiler_get_backtrace() unsupported"); +#endif + +} // namespace baseprofiler +} // namespace mozilla |