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// Copyright (c) 2010 Google 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:
//
// * 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.
// The ExceptionHandler object installs signal handlers for a number of
// signals. We rely on the signal handler running on the thread which crashed
// in order to identify it. This is true of the synchronous signals (SEGV etc),
// but not true of ABRT. Thus, if you send ABRT to yourself in a program which
// uses ExceptionHandler, you need to use tgkill to direct it to the current
// thread.
//
// The signal flow looks like this:
//
// SignalHandler (uses a global stack of ExceptionHandler objects to find
// | one to handle the signal. If the first rejects it, try
// | the second etc...)
// V
// HandleSignal ----------------------------| (clones a new process which
// | | shares an address space with
// (wait for cloned | the crashed process. This
// process) | allows us to ptrace the crashed
// | | process)
// V V
// (set signal handler to ThreadEntry (static function to bounce
// SIG_DFL and rethrow, | back into the object)
// killing the crashed |
// process) V
// DoDump (writes minidump)
// |
// V
// sys_exit
//
// This code is a little fragmented. Different functions of the ExceptionHandler
// class run in a number of different contexts. Some of them run in a normal
// context and are easy to code, others run in a compromised context and the
// restrictions at the top of minidump_writer.cc apply: no libc and use the
// alternative malloc. Each function should have comment above it detailing the
// context which it runs in.
#include "linux/handler/exception_handler.h"
#include <errno.h>
#include <fcntl.h>
#include <linux/limits.h>
#include <pthread.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/ucontext.h>
#include <sys/user.h>
#include <ucontext.h>
#include <algorithm>
#include <utility>
#include <vector>
#include "common/basictypes.h"
#include "common/linux/breakpad_getcontext.h"
#include "common/linux/linux_libc_support.h"
#include "common/memory_allocator.h"
#include "linux/log/log.h"
#include "linux/microdump_writer/microdump_writer.h"
#include "linux/minidump_writer/linux_dumper.h"
#include "linux/minidump_writer/minidump_writer.h"
#include "common/linux/eintr_wrapper.h"
#include "third_party/lss/linux_syscall_support.h"
#if defined(MOZ_OXIDIZED_BREAKPAD)
#include "mozilla/toolkit/crashreporter/rust_minidump_writer_linux_ffi_generated.h"
#endif
#ifdef MOZ_PHC
#include "PHC.h"
#endif
#if defined(__ANDROID__)
#include "linux/sched.h"
#endif
#ifndef PR_SET_PTRACER
#define PR_SET_PTRACER 0x59616d61
#endif
#define SKIP_SIGILL(sig) if (g_skip_sigill_ && (sig == SIGILL)) continue;
namespace google_breakpad {
namespace {
// The list of signals which we consider to be crashes. The default action for
// all these signals must be Core (see man 7 signal) because we rethrow the
// signal after handling it and expect that it'll be fatal.
const int kExceptionSignals[] = {
SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS, SIGTRAP
};
const int kNumHandledSignals =
sizeof(kExceptionSignals) / sizeof(kExceptionSignals[0]);
struct sigaction old_handlers[kNumHandledSignals];
bool handlers_installed = false;
// InstallAlternateStackLocked will store the newly installed stack in new_stack
// and (if it exists) the previously installed stack in old_stack.
stack_t old_stack;
stack_t new_stack;
bool stack_installed = false;
// Create an alternative stack to run the signal handlers on. This is done since
// the signal might have been caused by a stack overflow.
// Runs before crashing: normal context.
void InstallAlternateStackLocked() {
if (stack_installed)
return;
memset(&old_stack, 0, sizeof(old_stack));
memset(&new_stack, 0, sizeof(new_stack));
// SIGSTKSZ may be too small to prevent the signal handlers from overrunning
// the alternative stack. Ensure that the size of the alternative stack is
// large enough.
static const size_t kSigStackSize = std::max(size_t(16384), size_t(SIGSTKSZ));
// Only set an alternative stack if there isn't already one, or if the current
// one is too small.
if (sys_sigaltstack(NULL, &old_stack) == -1 || !old_stack.ss_sp ||
old_stack.ss_size < kSigStackSize) {
new_stack.ss_sp = calloc(1, kSigStackSize);
new_stack.ss_size = kSigStackSize;
if (sys_sigaltstack(&new_stack, NULL) == -1) {
free(new_stack.ss_sp);
return;
}
stack_installed = true;
}
}
// Runs before crashing: normal context.
void RestoreAlternateStackLocked() {
if (!stack_installed)
return;
stack_t current_stack;
if (sys_sigaltstack(NULL, ¤t_stack) == -1)
return;
// Only restore the old_stack if the current alternative stack is the one
// installed by the call to InstallAlternateStackLocked.
if (current_stack.ss_sp == new_stack.ss_sp) {
if (old_stack.ss_sp) {
if (sys_sigaltstack(&old_stack, NULL) == -1)
return;
} else {
stack_t disable_stack;
disable_stack.ss_flags = SS_DISABLE;
if (sys_sigaltstack(&disable_stack, NULL) == -1)
return;
}
}
free(new_stack.ss_sp);
stack_installed = false;
}
void InstallDefaultHandler(int sig) {
#if defined(__ANDROID__)
// Android L+ expose signal and sigaction symbols that override the system
// ones. There is a bug in these functions where a request to set the handler
// to SIG_DFL is ignored. In that case, an infinite loop is entered as the
// signal is repeatedly sent to breakpad's signal handler.
// To work around this, directly call the system's sigaction.
struct kernel_sigaction sa;
memset(&sa, 0, sizeof(sa));
sys_sigemptyset(&sa.sa_mask);
sa.sa_handler_ = SIG_DFL;
sa.sa_flags = SA_RESTART;
sys_rt_sigaction(sig, &sa, NULL, sizeof(kernel_sigset_t));
#else
signal(sig, SIG_DFL);
#endif
}
// The global exception handler stack. This is needed because there may exist
// multiple ExceptionHandler instances in a process. Each will have itself
// registered in this stack.
std::vector<ExceptionHandler*>* g_handler_stack_ = NULL;
pthread_mutex_t g_handler_stack_mutex_ = PTHREAD_MUTEX_INITIALIZER;
// sizeof(CrashContext) can be too big w.r.t the size of alternatate stack
// for SignalHandler(). Keep the crash context as a .bss field. Exception
// handlers are serialized by the |g_handler_stack_mutex_| and at most one at a
// time can use |g_crash_context_|.
ExceptionHandler::CrashContext g_crash_context_;
FirstChanceHandler g_first_chance_handler_ = nullptr;
bool g_skip_sigill_ = false;
} // namespace
// Runs before crashing: normal context.
ExceptionHandler::ExceptionHandler(const MinidumpDescriptor& descriptor,
FilterCallback filter,
MinidumpCallback callback,
void* callback_context,
bool install_handler,
const int server_fd)
: filter_(filter),
callback_(callback),
callback_context_(callback_context),
minidump_descriptor_(descriptor),
crash_handler_(NULL) {
g_skip_sigill_ = getenv("MOZ_DISABLE_EXCEPTION_HANDLER_SIGILL") ? true : false;
if (server_fd >= 0)
crash_generation_client_.reset(CrashGenerationClient::TryCreate(server_fd));
if (!IsOutOfProcess() && !minidump_descriptor_.IsFD() &&
!minidump_descriptor_.IsMicrodumpOnConsole())
minidump_descriptor_.UpdatePath();
#if defined(__ANDROID__)
if (minidump_descriptor_.IsMicrodumpOnConsole())
logger::initializeCrashLogWriter();
#endif
pthread_mutex_lock(&g_handler_stack_mutex_);
// Pre-fault the crash context struct. This is to avoid failing due to OOM
// if handling an exception when the process ran out of virtual memory.
memset(&g_crash_context_, 0, sizeof(g_crash_context_));
if (!g_handler_stack_)
g_handler_stack_ = new std::vector<ExceptionHandler*>;
if (install_handler) {
InstallAlternateStackLocked();
InstallHandlersLocked();
}
g_handler_stack_->push_back(this);
pthread_mutex_unlock(&g_handler_stack_mutex_);
}
// Runs before crashing: normal context.
ExceptionHandler::~ExceptionHandler() {
pthread_mutex_lock(&g_handler_stack_mutex_);
std::vector<ExceptionHandler*>::iterator handler =
std::find(g_handler_stack_->begin(), g_handler_stack_->end(), this);
g_handler_stack_->erase(handler);
if (g_handler_stack_->empty()) {
delete g_handler_stack_;
g_handler_stack_ = NULL;
RestoreAlternateStackLocked();
RestoreHandlersLocked();
}
pthread_mutex_unlock(&g_handler_stack_mutex_);
}
// Runs before crashing: normal context.
// static
bool ExceptionHandler::InstallHandlersLocked() {
if (handlers_installed)
return false;
// Fail if unable to store all the old handlers.
for (int i = 0; i < kNumHandledSignals; ++i) {
SKIP_SIGILL(kExceptionSignals[i]);
if (sigaction(kExceptionSignals[i], NULL, &old_handlers[i]) == -1)
return false;
}
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
// Mask all exception signals when we're handling one of them.
for (int i = 0; i < kNumHandledSignals; ++i) {
SKIP_SIGILL(kExceptionSignals[i]);
sigaddset(&sa.sa_mask, kExceptionSignals[i]);
}
sa.sa_sigaction = SignalHandler;
sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
for (int i = 0; i < kNumHandledSignals; ++i) {
SKIP_SIGILL(kExceptionSignals[i]);
if (sigaction(kExceptionSignals[i], &sa, NULL) == -1) {
// At this point it is impractical to back out changes, and so failure to
// install a signal is intentionally ignored.
}
}
handlers_installed = true;
return true;
}
// This function runs in a compromised context: see the top of the file.
// Runs on the crashing thread.
// static
void ExceptionHandler::RestoreHandlersLocked() {
if (!handlers_installed)
return;
for (int i = 0; i < kNumHandledSignals; ++i) {
SKIP_SIGILL(kExceptionSignals[i]);
if (sigaction(kExceptionSignals[i], &old_handlers[i], NULL) == -1) {
InstallDefaultHandler(kExceptionSignals[i]);
}
}
handlers_installed = false;
}
// void ExceptionHandler::set_crash_handler(HandlerCallback callback) {
// crash_handler_ = callback;
// }
// This function runs in a compromised context: see the top of the file.
// Runs on the crashing thread.
// static
void ExceptionHandler::SignalHandler(int sig, siginfo_t* info, void* uc) {
// Give the first chance handler a chance to recover from this signal
//
// This is primarily used by V8. V8 uses guard regions to guarantee memory
// safety in WebAssembly. This means some signals might be expected if they
// originate from Wasm code while accessing the guard region. We give V8 the
// chance to handle and recover from these signals first.
if (g_first_chance_handler_ != nullptr &&
g_first_chance_handler_(sig, info, uc)) {
return;
}
// All the exception signals are blocked at this point.
pthread_mutex_lock(&g_handler_stack_mutex_);
// Sometimes, Breakpad runs inside a process where some other buggy code
// saves and restores signal handlers temporarily with 'signal'
// instead of 'sigaction'. This loses the SA_SIGINFO flag associated
// with this function. As a consequence, the values of 'info' and 'uc'
// become totally bogus, generally inducing a crash.
//
// The following code tries to detect this case. When it does, it
// resets the signal handlers with sigaction + SA_SIGINFO and returns.
// This forces the signal to be thrown again, but this time the kernel
// will call the function with the right arguments.
struct sigaction cur_handler;
if (sigaction(sig, NULL, &cur_handler) == 0 &&
cur_handler.sa_sigaction == SignalHandler &&
(cur_handler.sa_flags & SA_SIGINFO) == 0) {
// Reset signal handler with the right flags.
sigemptyset(&cur_handler.sa_mask);
sigaddset(&cur_handler.sa_mask, sig);
cur_handler.sa_sigaction = SignalHandler;
cur_handler.sa_flags = SA_ONSTACK | SA_SIGINFO;
if (sigaction(sig, &cur_handler, NULL) == -1) {
// When resetting the handler fails, try to reset the
// default one to avoid an infinite loop here.
InstallDefaultHandler(sig);
}
pthread_mutex_unlock(&g_handler_stack_mutex_);
return;
}
bool handled = false;
for (int i = g_handler_stack_->size() - 1; !handled && i >= 0; --i) {
handled = (*g_handler_stack_)[i]->HandleSignal(sig, info, uc);
}
// Upon returning from this signal handler, sig will become unmasked and then
// it will be retriggered. If one of the ExceptionHandlers handled it
// successfully, restore the default handler. Otherwise, restore the
// previously installed handler. Then, when the signal is retriggered, it will
// be delivered to the appropriate handler.
if (handled) {
InstallDefaultHandler(sig);
} else {
RestoreHandlersLocked();
}
pthread_mutex_unlock(&g_handler_stack_mutex_);
// info->si_code <= 0 iff SI_FROMUSER (SI_FROMKERNEL otherwise).
if (info->si_code <= 0 || sig == SIGABRT) {
// This signal was triggered by somebody sending us the signal with kill().
// In order to retrigger it, we have to queue a new signal by calling
// kill() ourselves. The special case (si_pid == 0 && sig == SIGABRT) is
// due to the kernel sending a SIGABRT from a user request via SysRQ.
if (sys_tgkill(getpid(), syscall(__NR_gettid), sig) < 0) {
// If we failed to kill ourselves (e.g. because a sandbox disallows us
// to do so), we instead resort to terminating our process. This will
// result in an incorrect exit code.
_exit(1);
}
} else {
// This was a synchronous signal triggered by a hard fault (e.g. SIGSEGV).
// No need to reissue the signal. It will automatically trigger again,
// when we return from the signal handler.
}
}
struct ThreadArgument {
pid_t pid; // the crashing process
const MinidumpDescriptor* minidump_descriptor;
ExceptionHandler* handler;
const void* context; // a CrashContext structure
size_t context_size;
};
// This is the entry function for the cloned process. We are in a compromised
// context here: see the top of the file.
// static
int ExceptionHandler::ThreadEntry(void *arg) {
const ThreadArgument *thread_arg = reinterpret_cast<ThreadArgument*>(arg);
// Close the write end of the pipe. This allows us to fail if the parent dies
// while waiting for the continue signal.
sys_close(thread_arg->handler->fdes[1]);
// Block here until the crashing process unblocks us when
// we're allowed to use ptrace
thread_arg->handler->WaitForContinueSignal();
sys_close(thread_arg->handler->fdes[0]);
return thread_arg->handler->DoDump(thread_arg->pid, thread_arg->context,
thread_arg->context_size) == false;
}
#ifdef MOZ_PHC
static void GetPHCAddrInfo(siginfo_t* siginfo,
mozilla::phc::AddrInfo* addr_info) {
// Is this a crash involving a PHC allocation?
if (siginfo->si_signo == SIGSEGV || siginfo->si_signo == SIGBUS) {
mozilla::phc::IsPHCAllocation(siginfo->si_addr, addr_info);
}
}
#endif
// This function runs in a compromised context: see the top of the file.
// Runs on the crashing thread.
bool ExceptionHandler::HandleSignal(int /*sig*/, siginfo_t* info, void* uc) {
mozilla::phc::AddrInfo* addr_info = nullptr;
#ifdef MOZ_PHC
addr_info = &mozilla::phc::gAddrInfo;
GetPHCAddrInfo(info, addr_info);
#endif
if (filter_ && !filter_(callback_context_))
return false;
// Allow ourselves to be dumped if the signal is trusted.
bool signal_trusted = info->si_code > 0;
bool signal_pid_trusted = info->si_code == SI_USER ||
info->si_code == SI_TKILL;
if (signal_trusted || (signal_pid_trusted && info->si_pid == getpid())) {
sys_prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
}
// Fill in all the holes in the struct to make Valgrind happy.
memset(&g_crash_context_, 0, sizeof(g_crash_context_));
memcpy(&g_crash_context_.siginfo, info, sizeof(siginfo_t));
memcpy(&g_crash_context_.context, uc, sizeof(ucontext_t));
#if defined(__aarch64__)
ucontext_t* uc_ptr = (ucontext_t*)uc;
struct fpsimd_context* fp_ptr =
(struct fpsimd_context*)&uc_ptr->uc_mcontext.__reserved;
if (fp_ptr->head.magic == FPSIMD_MAGIC) {
memcpy(&g_crash_context_.float_state, fp_ptr,
sizeof(g_crash_context_.float_state));
}
#elif !defined(__ARM_EABI__) && !defined(__mips__)
// FP state is not part of user ABI on ARM Linux.
// In case of MIPS Linux FP state is already part of ucontext_t
// and 'float_state' is not a member of CrashContext.
ucontext_t* uc_ptr = (ucontext_t*)uc;
if (uc_ptr->uc_mcontext.fpregs) {
memcpy(&g_crash_context_.float_state, uc_ptr->uc_mcontext.fpregs,
sizeof(g_crash_context_.float_state));
}
#endif
g_crash_context_.tid = syscall(__NR_gettid);
if (crash_handler_ != NULL) {
if (crash_handler_(&g_crash_context_, sizeof(g_crash_context_),
callback_context_)) {
return true;
}
}
return GenerateDump(&g_crash_context_, addr_info);
}
// This is a public interface to HandleSignal that allows the client to
// generate a crash dump. This function may run in a compromised context.
bool ExceptionHandler::SimulateSignalDelivery(int sig) {
siginfo_t siginfo = {};
// Mimic a trusted signal to allow tracing the process (see
// ExceptionHandler::HandleSignal().
siginfo.si_code = SI_USER;
siginfo.si_pid = getpid();
ucontext_t context;
getcontext(&context);
return HandleSignal(sig, &siginfo, &context);
}
// This function may run in a compromised context: see the top of the file.
bool ExceptionHandler::GenerateDump(
CrashContext *context, const mozilla::phc::AddrInfo* addr_info) {
if (IsOutOfProcess()) {
bool success =
crash_generation_client_->RequestDump(context, sizeof(*context));
if (callback_) {
success =
callback_(minidump_descriptor_, callback_context_, addr_info, success);
}
return success;
}
// Allocating too much stack isn't a problem, and better to err on the side
// of caution than smash it into random locations.
static const unsigned kChildStackSize = 16000;
PageAllocator allocator;
uint8_t* stack = reinterpret_cast<uint8_t*>(allocator.Alloc(kChildStackSize));
if (!stack)
return false;
// clone() needs the top-most address. (scrub just to be safe)
stack += kChildStackSize;
my_memset(stack - 16, 0, 16);
ThreadArgument thread_arg;
thread_arg.handler = this;
thread_arg.minidump_descriptor = &minidump_descriptor_;
thread_arg.pid = getpid();
thread_arg.context = context;
thread_arg.context_size = sizeof(*context);
// We need to explicitly enable ptrace of parent processes on some
// kernels, but we need to know the PID of the cloned process before we
// can do this. Create a pipe here which we can use to block the
// cloned process after creating it, until we have explicitly enabled ptrace
if (sys_pipe(fdes) == -1) {
// Creating the pipe failed. We'll log an error but carry on anyway,
// as we'll probably still get a useful crash report. All that will happen
// is the write() and read() calls will fail with EBADF
static const char no_pipe_msg[] = "ExceptionHandler::GenerateDump "
"sys_pipe failed:";
logger::write(no_pipe_msg, sizeof(no_pipe_msg) - 1);
logger::write(strerror(errno), strlen(strerror(errno)));
logger::write("\n", 1);
// Ensure fdes[0] and fdes[1] are invalid file descriptors.
fdes[0] = fdes[1] = -1;
}
static const char attempt_msg[] = "ExceptionHandler::GenerateDump attempting "
"to generate:";
logger::write(attempt_msg, sizeof(attempt_msg));
logger::write(minidump_descriptor_.path(),
my_strlen(minidump_descriptor_.path()));
logger::write("\n", 1);
const pid_t child = sys_clone(
ThreadEntry, stack, CLONE_FS | CLONE_UNTRACED, &thread_arg, NULL, NULL,
NULL);
if (child == -1) {
sys_close(fdes[0]);
sys_close(fdes[1]);
return false;
}
if (child != 0) {
static const char clonedMsg[] =
"ExceptionHandler::GenerateDump cloned child ";
char pidMsg[32] = {};
unsigned int pidLen = my_uint_len(child);
my_uitos(pidMsg, child, pidLen);
logger::write(clonedMsg, my_strlen(clonedMsg));
logger::write(pidMsg, pidLen);
logger::write("\n", 1);
} else {
static const char childMsg[] =
"ExceptionHandler::GenerateDump I'm the child\n";
logger::write(childMsg, my_strlen(childMsg));
}
// Close the read end of the pipe.
sys_close(fdes[0]);
// Allow the child to ptrace us
sys_prctl(PR_SET_PTRACER, child, 0, 0, 0);
SendContinueSignalToChild();
int status = 0;
const int r = HANDLE_EINTR(sys_waitpid(child, &status, __WALL));
sys_close(fdes[1]);
if (r == -1) {
static const char msg[] = "ExceptionHandler::GenerateDump waitpid failed:";
logger::write(msg, sizeof(msg) - 1);
logger::write(strerror(errno), strlen(strerror(errno)));
logger::write("\n", 1);
}
bool success = r != -1 && WIFEXITED(status) && WEXITSTATUS(status) == 0;
static const char generate_msg[] = "ExceptionHandler::GenerateDump minidump "
"generation ";
static const char success_msg[] = "succeeded\n";
static const char fail_msg[] = "succeeded\n";
logger::write(generate_msg, sizeof(generate_msg));
if (success) {
logger::write(success_msg, sizeof(success_msg));
} else {
logger::write(fail_msg, sizeof(fail_msg));
}
if (callback_)
success =
callback_(minidump_descriptor_, callback_context_, addr_info, success);
return success;
}
// This function runs in a compromised context: see the top of the file.
void ExceptionHandler::SendContinueSignalToChild() {
static const char okToContinueMessage = 'a';
int r;
r = HANDLE_EINTR(sys_write(fdes[1], &okToContinueMessage, sizeof(char)));
if (r == -1) {
static const char msg[] = "ExceptionHandler::SendContinueSignalToChild "
"sys_write failed:";
logger::write(msg, sizeof(msg) - 1);
logger::write(strerror(errno), strlen(strerror(errno)));
logger::write("\n", 1);
}
const char* msg = "ExceptionHandler::SendContinueSignalToChild sent continue signal to child\n";
logger::write(msg, my_strlen(msg));
}
// This function runs in a compromised context: see the top of the file.
// Runs on the cloned process.
void ExceptionHandler::WaitForContinueSignal() {
int r;
char receivedMessage;
const char* waitMsg = "ExceptionHandler::WaitForContinueSignal waiting for continue signal...\n";
logger::write(waitMsg, my_strlen(waitMsg));
r = HANDLE_EINTR(sys_read(fdes[0], &receivedMessage, sizeof(char)));
if (r == -1) {
static const char msg[] = "ExceptionHandler::WaitForContinueSignal "
"sys_read failed:";
logger::write(msg, sizeof(msg) - 1);
logger::write(strerror(errno), strlen(strerror(errno)));
logger::write("\n", 1);
}
}
// This function runs in a compromised context: see the top of the file.
// Runs on the cloned process.
bool ExceptionHandler::DoDump(pid_t crashing_process, const void* context,
size_t context_size) {
const bool may_skip_dump =
minidump_descriptor_.skip_dump_if_principal_mapping_not_referenced();
const uintptr_t principal_mapping_address =
minidump_descriptor_.address_within_principal_mapping();
const bool sanitize_stacks = minidump_descriptor_.sanitize_stacks();
if (minidump_descriptor_.IsMicrodumpOnConsole()) {
return google_breakpad::WriteMicrodump(
crashing_process,
context,
context_size,
mapping_list_,
may_skip_dump,
principal_mapping_address,
sanitize_stacks,
*minidump_descriptor_.microdump_extra_info());
}
if (minidump_descriptor_.IsFD()) {
return google_breakpad::WriteMinidump(minidump_descriptor_.fd(),
minidump_descriptor_.size_limit(),
crashing_process,
context,
context_size,
mapping_list_,
app_memory_list_,
may_skip_dump,
principal_mapping_address,
sanitize_stacks);
}
return google_breakpad::WriteMinidump(minidump_descriptor_.path(),
minidump_descriptor_.size_limit(),
crashing_process,
context,
context_size,
mapping_list_,
app_memory_list_,
may_skip_dump,
principal_mapping_address,
sanitize_stacks);
}
// static
bool ExceptionHandler::WriteMinidump(const string& dump_path,
MinidumpCallback callback,
void* callback_context) {
MinidumpDescriptor descriptor(dump_path);
ExceptionHandler eh(descriptor, NULL, callback, callback_context, false, -1);
return eh.WriteMinidump();
}
// In order to making using EBP to calculate the desired value for ESP
// a valid operation, ensure that this function is compiled with a
// frame pointer using the following attribute. This attribute
// is supported on GCC but not on clang.
#if defined(__i386__) && defined(__GNUC__) && !defined(__clang__)
__attribute__((optimize("no-omit-frame-pointer")))
#endif
bool ExceptionHandler::WriteMinidump() {
if (!IsOutOfProcess() && !minidump_descriptor_.IsFD() &&
!minidump_descriptor_.IsMicrodumpOnConsole()) {
// Update the path of the minidump so that this can be called multiple times
// and new files are created for each minidump. This is done before the
// generation happens, as clients may want to access the MinidumpDescriptor
// after this call to find the exact path to the minidump file.
minidump_descriptor_.UpdatePath();
} else if (minidump_descriptor_.IsFD()) {
// Reposition the FD to its beginning and resize it to get rid of the
// previous minidump info.
lseek(minidump_descriptor_.fd(), 0, SEEK_SET);
ignore_result(ftruncate(minidump_descriptor_.fd(), 0));
}
// Allow this process to be dumped.
sys_prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
CrashContext context;
int getcontext_result = getcontext(&context.context);
if (getcontext_result)
return false;
#if defined(__i386__)
// In CPUFillFromUContext in minidumpwriter.cc the stack pointer is retrieved
// from REG_UESP instead of from REG_ESP. REG_UESP is the user stack pointer
// and it only makes sense when running in kernel mode with a different stack
// pointer. When WriteMiniDump is called during normal processing REG_UESP is
// zero which leads to bad minidump files.
if (!context.context.uc_mcontext.gregs[REG_UESP]) {
// If REG_UESP is set to REG_ESP then that includes the stack space for the
// CrashContext object in this function, which is about 128 KB. Since the
// Linux dumper only records 32 KB of stack this would mean that nothing
// useful would be recorded. A better option is to set REG_UESP to REG_EBP,
// perhaps with a small negative offset in case there is any code that
// objects to them being equal.
context.context.uc_mcontext.gregs[REG_UESP] =
context.context.uc_mcontext.gregs[REG_EBP] - 16;
// The stack saving is based off of REG_ESP so it must be set to match the
// new REG_UESP.
context.context.uc_mcontext.gregs[REG_ESP] =
context.context.uc_mcontext.gregs[REG_UESP];
}
#endif
#if !defined(__ARM_EABI__) && !defined(__aarch64__) && !defined(__mips__)
// FPU state is not part of ARM EABI ucontext_t.
memcpy(&context.float_state, context.context.uc_mcontext.fpregs,
sizeof(context.float_state));
#endif
context.tid = sys_gettid();
// Add an exception stream to the minidump for better reporting.
memset(&context.siginfo, 0, sizeof(context.siginfo));
context.siginfo.si_signo = MD_EXCEPTION_CODE_LIN_DUMP_REQUESTED;
#if defined(__i386__)
context.siginfo.si_addr =
reinterpret_cast<void*>(context.context.uc_mcontext.gregs[REG_EIP]);
#elif defined(__x86_64__)
context.siginfo.si_addr =
reinterpret_cast<void*>(context.context.uc_mcontext.gregs[REG_RIP]);
#elif defined(__arm__)
context.siginfo.si_addr =
reinterpret_cast<void*>(context.context.uc_mcontext.arm_pc);
#elif defined(__aarch64__)
context.siginfo.si_addr =
reinterpret_cast<void*>(context.context.uc_mcontext.pc);
#elif defined(__mips__)
context.siginfo.si_addr =
reinterpret_cast<void*>(context.context.uc_mcontext.pc);
#else
#error "This code has not been ported to your platform yet."
#endif
// nullptr here for phc::AddrInfo* is ok because this is not a crash.
return GenerateDump(&context, nullptr);
}
void ExceptionHandler::AddMappingInfo(const string& name,
const wasteful_vector<uint8_t>& identifier,
uintptr_t start_address,
size_t mapping_size,
size_t file_offset) {
MappingInfo info;
info.start_addr = start_address;
info.size = mapping_size;
info.offset = file_offset;
strncpy(info.name, name.c_str(), sizeof(info.name) - 1);
info.name[sizeof(info.name) - 1] = '\0';
MappingEntry mapping;
mapping.first = info;
mapping.second.assign(identifier.begin(), identifier.end());
mapping_list_.push_back(mapping);
}
void ExceptionHandler::RegisterAppMemory(void* ptr, size_t length) {
AppMemoryList::iterator iter =
std::find(app_memory_list_.begin(), app_memory_list_.end(), ptr);
if (iter != app_memory_list_.end()) {
// Don't allow registering the same pointer twice.
return;
}
AppMemory app_memory;
app_memory.ptr = ptr;
app_memory.length = length;
app_memory_list_.push_back(app_memory);
}
void ExceptionHandler::UnregisterAppMemory(void* ptr) {
AppMemoryList::iterator iter =
std::find(app_memory_list_.begin(), app_memory_list_.end(), ptr);
if (iter != app_memory_list_.end()) {
app_memory_list_.erase(iter);
}
}
// static
bool ExceptionHandler::WriteMinidumpForChild(pid_t child,
pid_t child_blamed_thread,
const string& dump_path,
MinidumpCallback callback,
void* callback_context) {
// This function is not run in a compromised context.
MinidumpDescriptor descriptor(dump_path);
descriptor.UpdatePath();
#if defined(MOZ_OXIDIZED_BREAKPAD)
char* error_msg;
if (!write_minidump_linux(descriptor.path(), child, child_blamed_thread, &error_msg)) {
return false;
}
#else
if (!google_breakpad::WriteMinidump(descriptor.path(),
child,
child_blamed_thread))
return false;
#endif
// nullptr here for phc::AddrInfo* is ok because this is not a crash.
return callback ? callback(descriptor, callback_context, nullptr, true)
: true;
}
void SetFirstChanceExceptionHandler(FirstChanceHandler callback) {
g_first_chance_handler_ = callback;
}
} // namespace google_breakpad