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/* -*- 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 {
BaseProfilerProcessId profiler_current_process_id() {
return BaseProfilerProcessId::FromNumber(getpid());
}
BaseProfilerThreadId profiler_current_thread_id() {
#if defined(GP_OS_linux)
// glibc doesn't provide a wrapper for gettid() until 2.30
return BaseProfilerThreadId::FromNumber(
static_cast<BaseProfilerThreadId::NumberType>(syscall(SYS_gettid)));
#elif defined(GP_OS_android)
return BaseProfilerThreadId::FromNumber(
static_cast<BaseProfilerThreadId::NumberType>(gettid()));
#elif defined(GP_OS_freebsd)
long id;
(void)thr_self(&id);
return BaseProfilerThreadId::FromNumber(
static_cast<BaseProfilerThreadId::NumberType>(id));
#else
# error "bad platform"
#endif
}
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);
}
~SigHandlerCoordinator() {
int r = sem_destroy(&mMessage2);
r |= sem_destroy(&mMessage3);
r |= sem_destroy(&mMessage4);
MOZ_ASSERT(r == 0);
}
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,
bool aStackWalkEnabled,
bool aNoTimerResolutionChange)
: 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 && aStackWalkEnabled) {
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. (At one point we did have a paf_child()
// function, but it caused problems related to locking gPSMutex. See bug
// 1348374.)
//
// Unfortunately all this is only doable on non-Android because Bionic doesn't
// have pthread_atfork.
// In the parent, before the fork, record IsSamplingPaused, and then pause.
static void paf_prepare() {
MOZ_RELEASE_ASSERT(CorePS::Exists());
PSAutoLock lock;
if (ActivePS::Exists(lock)) {
ActivePS::SetWasSamplingPaused(lock, ActivePS::IsSamplingPaused(lock));
ActivePS::SetIsSamplingPaused(lock, true);
}
}
// In the parent, after the fork, return IsSamplingPaused to the pre-fork state.
static void paf_parent() {
MOZ_RELEASE_ASSERT(CorePS::Exists());
PSAutoLock lock;
if (ActivePS::Exists(lock)) {
ActivePS::SetIsSamplingPaused(lock, ActivePS::WasSamplingPaused(lock));
ActivePS::SetWasSamplingPaused(lock, false);
}
}
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)
// Context used by synchronous samples. It's safe to have a single one because
// only one synchronous sample can be taken at a time (due to
// profiler_get_backtrace()'s PSAutoLock).
// ucontext_t sSyncUContext;
void Registers::SyncPopulate() {
// TODO port getcontext from breakpad, if profiler_get_backtrace is needed.
MOZ_CRASH("profiler_get_backtrace() unsupported");
// if (!getcontext(&sSyncUContext)) {
// PopulateRegsFromContext(*this, &sSyncUContext);
// }
}
#endif
} // namespace baseprofiler
} // namespace mozilla