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cobalt / cobalt / 6c50c1c49c8a70d13dcb47674d70da002e02256c / . / base / debug / stack_trace_posix.cc
blob: 72144e56678b68876bb49e0171bf884f51b93ec2 [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/debug/stack_trace.h"
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <algorithm>
#include <map>
#include <memory>
#include <ostream>
#include <string>
#include <vector>
#if !defined(USE_SYMBOLIZE)
#include <cxxabi.h>
#endif
#if !defined(__UCLIBC__) && !defined(_AIX)
#include <execinfo.h>
#endif
#if defined(OS_MACOSX)
#include <AvailabilityMacros.h>
#endif
#if defined(OS_LINUX)
#include "base/debug/proc_maps_linux.h"
#endif
#include "base/cfi_buildflags.h"
#include "base/debug/debugger.h"
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/memory/free_deleter.h"
#include "base/memory/singleton.h"
#include "base/numerics/safe_conversions.h"
#include "base/posix/eintr_wrapper.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "build/build_config.h"
#if defined(USE_SYMBOLIZE)
#include "base/third_party/symbolize/symbolize.h"
#include "starboard/common/string.h"
#include "starboard/memory.h"
#include "starboard/types.h"
#endif
namespace base {
namespace debug {
namespace {
volatile sig_atomic_t in_signal_handler = 0;
bool (*try_handle_signal)(int, void*, void*) = nullptr;
#if !defined(USE_SYMBOLIZE)
// The prefix used for mangled symbols, per the Itanium C++ ABI:
// http://www.codesourcery.com/cxx-abi/abi.html#mangling
const char kMangledSymbolPrefix[] = "_Z";
// Characters that can be used for symbols, generated by Ruby:
// (('a'..'z').to_a+('A'..'Z').to_a+('0'..'9').to_a + ['_']).join
const char kSymbolCharacters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";
#endif // !defined(USE_SYMBOLIZE)
#if !defined(USE_SYMBOLIZE)
// Demangles C++ symbols in the given text. Example:
//
// "out/Debug/base_unittests(_ZN10StackTraceC1Ev+0x20) [0x817778c]"
// =>
// "out/Debug/base_unittests(StackTrace::StackTrace()+0x20) [0x817778c]"
void DemangleSymbols(std::string* text) {
// Note: code in this function is NOT async-signal safe (std::string uses
// malloc internally).
#if !defined(__UCLIBC__) && !defined(_AIX)
std::string::size_type search_from = 0;
while (search_from < text->size()) {
// Look for the start of a mangled symbol, from search_from.
std::string::size_type mangled_start =
text->find(kMangledSymbolPrefix, search_from);
if (mangled_start == std::string::npos) {
break; // Mangled symbol not found.
}
// Look for the end of the mangled symbol.
std::string::size_type mangled_end =
text->find_first_not_of(kSymbolCharacters, mangled_start);
if (mangled_end == std::string::npos) {
mangled_end = text->size();
}
std::string mangled_symbol =
text->substr(mangled_start, mangled_end - mangled_start);
// Try to demangle the mangled symbol candidate.
int status = 0;
std::unique_ptr<char, base::FreeDeleter> demangled_symbol(
abi::__cxa_demangle(mangled_symbol.c_str(), nullptr, 0, &status));
if (status == 0) { // Demangling is successful.
// Remove the mangled symbol.
text->erase(mangled_start, mangled_end - mangled_start);
// Insert the demangled symbol.
text->insert(mangled_start, demangled_symbol.get());
// Next time, we'll start right after the demangled symbol we inserted.
search_from = mangled_start + strlen(demangled_symbol.get());
} else {
// Failed to demangle. Retry after the "_Z" we just found.
search_from = mangled_start + 2;
}
}
#endif // !defined(__UCLIBC__) && !defined(_AIX)
}
#endif // !defined(USE_SYMBOLIZE)
class BacktraceOutputHandler {
public:
virtual void HandleOutput(const char* output) = 0;
protected:
virtual ~BacktraceOutputHandler() = default;
};
#if !defined(__UCLIBC__) && !defined(_AIX)
void OutputPointer(void* pointer, BacktraceOutputHandler* handler) {
// This should be more than enough to store a 64-bit number in hex:
// 16 hex digits + 1 for null-terminator.
char buf[17] = { '\0' };
handler->HandleOutput("0x");
internal::itoa_r(reinterpret_cast<intptr_t>(pointer),
buf, sizeof(buf), 16, 12);
handler->HandleOutput(buf);
}
#if defined(USE_SYMBOLIZE)
void OutputFrameId(intptr_t frame_id, BacktraceOutputHandler* handler) {
// Max unsigned 64-bit number in decimal has 20 digits (18446744073709551615).
// Hence, 30 digits should be more than enough to represent it in decimal
// (including the null-terminator).
char buf[30] = { '\0' };
handler->HandleOutput("#");
internal::itoa_r(frame_id, buf, sizeof(buf), 10, 1);
handler->HandleOutput(buf);
}
#endif // defined(USE_SYMBOLIZE)
void ProcessBacktrace(void* const* trace,
size_t size,
const char* prefix_string,
BacktraceOutputHandler* handler) {
// NOTE: This code MUST be async-signal safe (it's used by in-process
// stack dumping signal handler). NO malloc or stdio is allowed here.
#if defined(USE_SYMBOLIZE)
for (size_t i = 0; i < size; ++i) {
if (prefix_string)
handler->HandleOutput(prefix_string);
OutputFrameId(i, handler);
handler->HandleOutput(" ");
OutputPointer(trace[i], handler);
handler->HandleOutput(" ");
char buf[1024] = { '\0' };
// Subtract by one as return address of function may be in the next
// function when a function is annotated as noreturn.
void* address = static_cast<char*>(trace[i]) - 1;
if (google::Symbolize(address, buf, sizeof(buf)))
handler->HandleOutput(buf);
else
handler->HandleOutput("<unknown>");
handler->HandleOutput("\n");
}
#else
bool printed = false;
// Below part is async-signal unsafe (uses malloc), so execute it only
// when we are not executing the signal handler.
if (in_signal_handler == 0) {
std::unique_ptr<char*, FreeDeleter> trace_symbols(
backtrace_symbols(trace, size));
if (trace_symbols.get()) {
for (size_t i = 0; i < size; ++i) {
std::string trace_symbol = trace_symbols.get()[i];
DemangleSymbols(&trace_symbol);
if (prefix_string)
handler->HandleOutput(prefix_string);
handler->HandleOutput(trace_symbol.c_str());
handler->HandleOutput("\n");
}
printed = true;
}
}
if (!printed) {
for (size_t i = 0; i < size; ++i) {
handler->HandleOutput(" [");
OutputPointer(trace[i], handler);
handler->HandleOutput("]\n");
}
}
#endif // defined(USE_SYMBOLIZE)
}
#endif // !defined(__UCLIBC__) && !defined(_AIX)
void PrintToStderr(const char* output) {
// NOTE: This code MUST be async-signal safe (it's used by in-process
// stack dumping signal handler). NO malloc or stdio is allowed here.
ignore_result(
HANDLE_EINTR(write(STDERR_FILENO, output, strlen(output))));
}
void StackDumpSignalHandler(int signal, siginfo_t* info, void* void_context) {
// NOTE: This code MUST be async-signal safe.
// NO malloc or stdio is allowed here.
// Give a registered callback a chance to recover from this signal
//
// 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 (try_handle_signal != nullptr &&
try_handle_signal(signal, info, void_context)) {
// The first chance handler took care of this. The SA_RESETHAND flag
// replaced this signal handler upon entry, but we want to stay
// installed. Thus, we reinstall ourselves before returning.
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_flags = SA_RESETHAND | SA_SIGINFO;
action.sa_sigaction = &StackDumpSignalHandler;
sigemptyset(&action.sa_mask);
sigaction(signal, &action, nullptr);
return;
}
// Do not take the "in signal handler" code path on Mac in a DCHECK-enabled
// build, as this prevents seeing a useful (symbolized) stack trace on a crash
// or DCHECK() failure. While it may not be fully safe to run the stack symbol
// printing code, in practice it's better to provide meaningful stack traces -
// and the risk is low given we're likely crashing already.
#if !defined(OS_MACOSX) || !DCHECK_IS_ON()
// Record the fact that we are in the signal handler now, so that the rest
// of StackTrace can behave in an async-signal-safe manner.
in_signal_handler = 1;
#endif
if (BeingDebugged())
BreakDebugger();
PrintToStderr("Received signal ");
char buf[1024] = { 0 };
internal::itoa_r(signal, buf, sizeof(buf), 10, 0);
PrintToStderr(buf);
if (signal == SIGBUS) {
if (info->si_code == BUS_ADRALN)
PrintToStderr(" BUS_ADRALN ");
else if (info->si_code == BUS_ADRERR)
PrintToStderr(" BUS_ADRERR ");
else if (info->si_code == BUS_OBJERR)
PrintToStderr(" BUS_OBJERR ");
else
PrintToStderr(" <unknown> ");
} else if (signal == SIGFPE) {
if (info->si_code == FPE_FLTDIV)
PrintToStderr(" FPE_FLTDIV ");
else if (info->si_code == FPE_FLTINV)
PrintToStderr(" FPE_FLTINV ");
else if (info->si_code == FPE_FLTOVF)
PrintToStderr(" FPE_FLTOVF ");
else if (info->si_code == FPE_FLTRES)
PrintToStderr(" FPE_FLTRES ");
else if (info->si_code == FPE_FLTSUB)
PrintToStderr(" FPE_FLTSUB ");
else if (info->si_code == FPE_FLTUND)
PrintToStderr(" FPE_FLTUND ");
else if (info->si_code == FPE_INTDIV)
PrintToStderr(" FPE_INTDIV ");
else if (info->si_code == FPE_INTOVF)
PrintToStderr(" FPE_INTOVF ");
else
PrintToStderr(" <unknown> ");
} else if (signal == SIGILL) {
if (info->si_code == ILL_BADSTK)
PrintToStderr(" ILL_BADSTK ");
else if (info->si_code == ILL_COPROC)
PrintToStderr(" ILL_COPROC ");
else if (info->si_code == ILL_ILLOPN)
PrintToStderr(" ILL_ILLOPN ");
else if (info->si_code == ILL_ILLADR)
PrintToStderr(" ILL_ILLADR ");
else if (info->si_code == ILL_ILLTRP)
PrintToStderr(" ILL_ILLTRP ");
else if (info->si_code == ILL_PRVOPC)
PrintToStderr(" ILL_PRVOPC ");
else if (info->si_code == ILL_PRVREG)
PrintToStderr(" ILL_PRVREG ");
else
PrintToStderr(" <unknown> ");
} else if (signal == SIGSEGV) {
if (info->si_code == SEGV_MAPERR)
PrintToStderr(" SEGV_MAPERR ");
else if (info->si_code == SEGV_ACCERR)
PrintToStderr(" SEGV_ACCERR ");
else
PrintToStderr(" <unknown> ");
}
if (signal == SIGBUS || signal == SIGFPE ||
signal == SIGILL || signal == SIGSEGV) {
internal::itoa_r(reinterpret_cast<intptr_t>(info->si_addr),
buf, sizeof(buf), 16, 12);
PrintToStderr(buf);
}
PrintToStderr("\n");
#if BUILDFLAG(CFI_ENFORCEMENT_TRAP)
if (signal == SIGILL && info->si_code == ILL_ILLOPN) {
PrintToStderr(
"CFI: Most likely a control flow integrity violation; for more "
"information see:\n");
PrintToStderr(
"https://www.chromium.org/developers/testing/control-flow-integrity\n");
}
#endif // BUILDFLAG(CFI_ENFORCEMENT_TRAP)
debug::StackTrace().Print();
#if defined(OS_LINUX)
#if ARCH_CPU_X86_FAMILY
ucontext_t* context = reinterpret_cast<ucontext_t*>(void_context);
const struct {
const char* label;
greg_t value;
} registers[] = {
#if ARCH_CPU_32_BITS
{ " gs: ", context->uc_mcontext.gregs[REG_GS] },
{ " fs: ", context->uc_mcontext.gregs[REG_FS] },
{ " es: ", context->uc_mcontext.gregs[REG_ES] },
{ " ds: ", context->uc_mcontext.gregs[REG_DS] },
{ " edi: ", context->uc_mcontext.gregs[REG_EDI] },
{ " esi: ", context->uc_mcontext.gregs[REG_ESI] },
{ " ebp: ", context->uc_mcontext.gregs[REG_EBP] },
{ " esp: ", context->uc_mcontext.gregs[REG_ESP] },
{ " ebx: ", context->uc_mcontext.gregs[REG_EBX] },
{ " edx: ", context->uc_mcontext.gregs[REG_EDX] },
{ " ecx: ", context->uc_mcontext.gregs[REG_ECX] },
{ " eax: ", context->uc_mcontext.gregs[REG_EAX] },
{ " trp: ", context->uc_mcontext.gregs[REG_TRAPNO] },
{ " err: ", context->uc_mcontext.gregs[REG_ERR] },
{ " ip: ", context->uc_mcontext.gregs[REG_EIP] },
{ " cs: ", context->uc_mcontext.gregs[REG_CS] },
{ " efl: ", context->uc_mcontext.gregs[REG_EFL] },
{ " usp: ", context->uc_mcontext.gregs[REG_UESP] },
{ " ss: ", context->uc_mcontext.gregs[REG_SS] },
#elif ARCH_CPU_64_BITS
{ " r8: ", context->uc_mcontext.gregs[REG_R8] },
{ " r9: ", context->uc_mcontext.gregs[REG_R9] },
{ " r10: ", context->uc_mcontext.gregs[REG_R10] },
{ " r11: ", context->uc_mcontext.gregs[REG_R11] },
{ " r12: ", context->uc_mcontext.gregs[REG_R12] },
{ " r13: ", context->uc_mcontext.gregs[REG_R13] },
{ " r14: ", context->uc_mcontext.gregs[REG_R14] },
{ " r15: ", context->uc_mcontext.gregs[REG_R15] },
{ " di: ", context->uc_mcontext.gregs[REG_RDI] },
{ " si: ", context->uc_mcontext.gregs[REG_RSI] },
{ " bp: ", context->uc_mcontext.gregs[REG_RBP] },
{ " bx: ", context->uc_mcontext.gregs[REG_RBX] },
{ " dx: ", context->uc_mcontext.gregs[REG_RDX] },
{ " ax: ", context->uc_mcontext.gregs[REG_RAX] },
{ " cx: ", context->uc_mcontext.gregs[REG_RCX] },
{ " sp: ", context->uc_mcontext.gregs[REG_RSP] },
{ " ip: ", context->uc_mcontext.gregs[REG_RIP] },
{ " efl: ", context->uc_mcontext.gregs[REG_EFL] },
{ " cgf: ", context->uc_mcontext.gregs[REG_CSGSFS] },
{ " erf: ", context->uc_mcontext.gregs[REG_ERR] },
{ " trp: ", context->uc_mcontext.gregs[REG_TRAPNO] },
{ " msk: ", context->uc_mcontext.gregs[REG_OLDMASK] },
{ " cr2: ", context->uc_mcontext.gregs[REG_CR2] },
#endif // ARCH_CPU_32_BITS
};
#if ARCH_CPU_32_BITS
const int kRegisterPadding = 8;
#elif ARCH_CPU_64_BITS
const int kRegisterPadding = 16;
#endif
for (size_t i = 0; i < arraysize(registers); i++) {
PrintToStderr(registers[i].label);
internal::itoa_r(registers[i].value, buf, sizeof(buf),
16, kRegisterPadding);
PrintToStderr(buf);
if ((i + 1) % 4 == 0)
PrintToStderr("\n");
}
PrintToStderr("\n");
#endif // ARCH_CPU_X86_FAMILY
#endif // defined(OS_LINUX)
PrintToStderr("[end of stack trace]\n");
#if defined(OS_MACOSX) && !defined(OS_IOS)
if (::signal(signal, SIG_DFL) == SIG_ERR)
_exit(1);
#else
// Non-Mac OSes should probably reraise the signal as well, but the Linux
// sandbox tests break on CrOS devices.
// https://code.google.com/p/chromium/issues/detail?id=551681
PrintToStderr("Calling _exit(1). Core file will not be generated.\n");
_exit(1);
#endif // defined(OS_MACOSX) && !defined(OS_IOS)
}
class PrintBacktraceOutputHandler : public BacktraceOutputHandler {
public:
PrintBacktraceOutputHandler() = default;
void HandleOutput(const char* output) override {
// NOTE: This code MUST be async-signal safe (it's used by in-process
// stack dumping signal handler). NO malloc or stdio is allowed here.
PrintToStderr(output);
}
private:
DISALLOW_COPY_AND_ASSIGN(PrintBacktraceOutputHandler);
};
class StreamBacktraceOutputHandler : public BacktraceOutputHandler {
public:
explicit StreamBacktraceOutputHandler(std::ostream* os) : os_(os) {
}
void HandleOutput(const char* output) override { (*os_) << output; }
private:
std::ostream* os_;
DISALLOW_COPY_AND_ASSIGN(StreamBacktraceOutputHandler);
};
void WarmUpBacktrace() {
// Warm up stack trace infrastructure. It turns out that on the first
// call glibc initializes some internal data structures using pthread_once,
// and even backtrace() can call malloc(), leading to hangs.
//
// Example stack trace snippet (with tcmalloc):
//
// #8 0x0000000000a173b5 in tc_malloc
// at ./third_party/tcmalloc/chromium/src/debugallocation.cc:1161
// #9 0x00007ffff7de7900 in _dl_map_object_deps at dl-deps.c:517
// #10 0x00007ffff7ded8a9 in dl_open_worker at dl-open.c:262
// #11 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
// #12 0x00007ffff7ded31a in _dl_open (file=0x7ffff625e298 "libgcc_s.so.1")
// at dl-open.c:639
// #13 0x00007ffff6215602 in do_dlopen at dl-libc.c:89
// #14 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
// #15 0x00007ffff62156c4 in dlerror_run at dl-libc.c:48
// #16 __GI___libc_dlopen_mode at dl-libc.c:165
// #17 0x00007ffff61ef8f5 in init
// at ../sysdeps/x86_64/../ia64/backtrace.c:53
// #18 0x00007ffff6aad400 in pthread_once
// at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_once.S:104
// #19 0x00007ffff61efa14 in __GI___backtrace
// at ../sysdeps/x86_64/../ia64/backtrace.c:104
// #20 0x0000000000752a54 in base::debug::StackTrace::StackTrace
// at base/debug/stack_trace_posix.cc:175
// #21 0x00000000007a4ae5 in
// base::(anonymous namespace)::StackDumpSignalHandler
// at base/process_util_posix.cc:172
// #22 <signal handler called>
StackTrace stack_trace;
}
#if defined(USE_SYMBOLIZE)
// class SandboxSymbolizeHelper.
//
// The purpose of this class is to prepare and install a "file open" callback
// needed by the stack trace symbolization code
// (base/third_party/symbolize/symbolize.h) so that it can function properly
// in a sandboxed process. The caveat is that this class must be instantiated
// before the sandboxing is enabled so that it can get the chance to open all
// the object files that are loaded in the virtual address space of the current
// process.
class SandboxSymbolizeHelper {
public:
// Returns the singleton instance.
static SandboxSymbolizeHelper* GetInstance() {
return Singleton<SandboxSymbolizeHelper,
LeakySingletonTraits<SandboxSymbolizeHelper>>::get();
}
private:
friend struct DefaultSingletonTraits<SandboxSymbolizeHelper>;
SandboxSymbolizeHelper()
: is_initialized_(false) {
Init();
}
~SandboxSymbolizeHelper() {
UnregisterCallback();
CloseObjectFiles();
}
// Returns a O_RDONLY file descriptor for |file_path| if it was opened
// successfully during the initialization. The file is repositioned at
// offset 0.
// IMPORTANT: This function must be async-signal-safe because it can be
// called from a signal handler (symbolizing stack frames for a crash).
int GetFileDescriptor(const char* file_path) {
int fd = -1;
#if !defined(OFFICIAL_BUILD)
if (file_path) {
// The assumption here is that iterating over std::map<std::string, int>
// using a const_iterator does not allocate dynamic memory, hense it is
// async-signal-safe.
std::map<std::string, int>::const_iterator it;
for (it = modules_.begin(); it != modules_.end(); ++it) {
if (strcmp((it->first).c_str(), file_path) == 0) {
// POSIX.1-2004 requires an implementation to guarantee that dup()
// is async-signal-safe.
fd = HANDLE_EINTR(dup(it->second));
break;
}
}
// POSIX.1-2004 requires an implementation to guarantee that lseek()
// is async-signal-safe.
if (fd >= 0 && lseek(fd, 0, SEEK_SET) < 0) {
// Failed to seek.
fd = -1;
}
}
#endif // !defined(OFFICIAL_BUILD)
return fd;
}
// Searches for the object file (from /proc/self/maps) that contains
// the specified pc. If found, sets |start_address| to the start address
// of where this object file is mapped in memory, sets the module base
// address into |base_address|, copies the object file name into
// |out_file_name|, and attempts to open the object file. If the object
// file is opened successfully, returns the file descriptor. Otherwise,
// returns -1. |out_file_name_size| is the size of the file name buffer
// (including the null terminator).
// IMPORTANT: This function must be async-signal-safe because it can be
// called from a signal handler (symbolizing stack frames for a crash).
static int OpenObjectFileContainingPc(uint64_t pc, uint64_t& start_address,
uint64_t& base_address, char* file_path,
int file_path_size) {
// This method can only be called after the singleton is instantiated.
// This is ensured by the following facts:
// * This is the only static method in this class, it is private, and
// the class has no friends (except for the DefaultSingletonTraits).
// The compiler guarantees that it can only be called after the
// singleton is instantiated.
// * This method is used as a callback for the stack tracing code and
// the callback registration is done in the constructor, so logically
// it cannot be called before the singleton is created.
SandboxSymbolizeHelper* instance = GetInstance();
// The assumption here is that iterating over
// std::vector<MappedMemoryRegion> using a const_iterator does not allocate
// dynamic memory, hence it is async-signal-safe.
for (const MappedMemoryRegion& region : instance->regions_) {
if (region.start <= pc && pc < region.end) {
start_address = region.start;
base_address = region.base;
if (file_path && file_path_size > 0) {
strncpy(file_path, region.path.c_str(), file_path_size);
// Ensure null termination.
file_path[file_path_size - 1] = '\0';
}
return instance->GetFileDescriptor(region.path.c_str());
}
}
return -1;
}
// Set the base address for each memory region by reading ELF headers in
// process memory.
void SetBaseAddressesForMemoryRegions() {
base::ScopedFD mem_fd(
HANDLE_EINTR(open("/proc/self/mem", O_RDONLY | O_CLOEXEC)));
if (!mem_fd.is_valid())
return;
auto safe_memcpy = [&mem_fd](void* dst, uintptr_t src, size_t size) {
return HANDLE_EINTR(pread(mem_fd.get(), dst, size, src)) == ssize_t(size);
};
uintptr_t cur_base = 0;
for (auto& r : regions_) {
ElfW(Ehdr) ehdr;
static_assert(SELFMAG <= sizeof(ElfW(Ehdr)), "SELFMAG too large");
if ((r.permissions & MappedMemoryRegion::READ) &&
safe_memcpy(&ehdr, r.start, sizeof(ElfW(Ehdr))) &&
memcmp(ehdr.e_ident, ELFMAG, SELFMAG) == 0) {
switch (ehdr.e_type) {
case ET_EXEC:
cur_base = 0;
break;
case ET_DYN:
// Find the segment containing file offset 0. This will correspond
// to the ELF header that we just read. Normally this will have
// virtual address 0, but this is not guaranteed. We must subtract
// the virtual address from the address where the ELF header was
// mapped to get the base address.
//
// If we fail to find a segment for file offset 0, use the address
// of the ELF header as the base address.
cur_base = r.start;
for (unsigned i = 0; i != ehdr.e_phnum; ++i) {
ElfW(Phdr) phdr;
if (safe_memcpy(&phdr, r.start + ehdr.e_phoff + i * sizeof(phdr),
sizeof(phdr)) &&
phdr.p_type == PT_LOAD && phdr.p_offset == 0) {
cur_base = r.start - phdr.p_vaddr;
break;
}
}
break;
default:
// ET_REL or ET_CORE. These aren't directly executable, so they
// don't affect the base address.
break;
}
}
r.base = cur_base;
}
}
// Parses /proc/self/maps in order to compile a list of all object file names
// for the modules that are loaded in the current process.
// Returns true on success.
bool CacheMemoryRegions() {
// Reads /proc/self/maps.
std::string contents;
if (!ReadProcMaps(&contents)) {
LOG(ERROR) << "Failed to read /proc/self/maps";
return false;
}
// Parses /proc/self/maps.
if (!ParseProcMaps(contents, &regions_)) {
LOG(ERROR) << "Failed to parse the contents of /proc/self/maps";
return false;
}
SetBaseAddressesForMemoryRegions();
is_initialized_ = true;
return true;
}
// Opens all object files and caches their file descriptors.
void OpenSymbolFiles() {
// Pre-opening and caching the file descriptors of all loaded modules is
// not safe for production builds. Hence it is only done in non-official
// builds. For more details, take a look at: http://crbug.com/341966.
#if !defined(OFFICIAL_BUILD)
// Open the object files for all read-only executable regions and cache
// their file descriptors.
std::vector<MappedMemoryRegion>::const_iterator it;
for (it = regions_.begin(); it != regions_.end(); ++it) {
const MappedMemoryRegion& region = *it;
// Only interesed in read-only executable regions.
if ((region.permissions & MappedMemoryRegion::READ) ==
MappedMemoryRegion::READ &&
(region.permissions & MappedMemoryRegion::WRITE) == 0 &&
(region.permissions & MappedMemoryRegion::EXECUTE) ==
MappedMemoryRegion::EXECUTE) {
if (region.path.empty()) {
// Skip regions with empty file names.
continue;
}
if (region.path[0] == '[') {
// Skip pseudo-paths, like [stack], [vdso], [heap], etc ...
continue;
}
if (base::EndsWith(region.path, " (deleted)",
base::CompareCase::SENSITIVE)) {
// Skip deleted files.
continue;
}
// Avoid duplicates.
if (modules_.find(region.path) == modules_.end()) {
int fd = open(region.path.c_str(), O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
modules_.insert(std::make_pair(region.path, fd));
} else {
LOG(WARNING) << "Failed to open file: " << region.path
<< "\n Error: " << strerror(errno);
}
}
}
}
#endif // !defined(OFFICIAL_BUILD)
}
// Initializes and installs the symbolization callback.
void Init() {
if (CacheMemoryRegions()) {
OpenSymbolFiles();
google::InstallSymbolizeOpenObjectFileCallback(
&OpenObjectFileContainingPc);
}
}
// Unregister symbolization callback.
void UnregisterCallback() {
if (is_initialized_) {
google::InstallSymbolizeOpenObjectFileCallback(nullptr);
is_initialized_ = false;
}
}
// Closes all file descriptors owned by this instance.
void CloseObjectFiles() {
#if !defined(OFFICIAL_BUILD)
std::map<std::string, int>::iterator it;
for (it = modules_.begin(); it != modules_.end(); ++it) {
int ret = IGNORE_EINTR(close(it->second));
DCHECK(!ret);
it->second = -1;
}
modules_.clear();
#endif // !defined(OFFICIAL_BUILD)
}
// Set to true upon successful initialization.
bool is_initialized_;
#if !defined(OFFICIAL_BUILD)
// Mapping from file name to file descriptor. Includes file descriptors
// for all successfully opened object files and the file descriptor for
// /proc/self/maps. This code is not safe for production builds.
std::map<std::string, int> modules_;
#endif // !defined(OFFICIAL_BUILD)
// Cache for the process memory regions. Produced by parsing the contents
// of /proc/self/maps cache.
std::vector<MappedMemoryRegion> regions_;
DISALLOW_COPY_AND_ASSIGN(SandboxSymbolizeHelper);
};
#endif // USE_SYMBOLIZE
} // namespace
bool EnableInProcessStackDumping() {
#if defined(USE_SYMBOLIZE)
SandboxSymbolizeHelper::GetInstance();
#endif // USE_SYMBOLIZE
// When running in an application, our code typically expects SIGPIPE
// to be ignored. Therefore, when testing that same code, it should run
// with SIGPIPE ignored as well.
struct sigaction sigpipe_action;
memset(&sigpipe_action, 0, sizeof(sigpipe_action));
sigpipe_action.sa_handler = SIG_IGN;
sigemptyset(&sigpipe_action.sa_mask);
bool success = (sigaction(SIGPIPE, &sigpipe_action, nullptr) == 0);
// Avoid hangs during backtrace initialization, see above.
WarmUpBacktrace();
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_flags = SA_RESETHAND | SA_SIGINFO;
action.sa_sigaction = &StackDumpSignalHandler;
sigemptyset(&action.sa_mask);
success &= (sigaction(SIGILL, &action, nullptr) == 0);
success &= (sigaction(SIGABRT, &action, nullptr) == 0);
success &= (sigaction(SIGFPE, &action, nullptr) == 0);
success &= (sigaction(SIGBUS, &action, nullptr) == 0);
success &= (sigaction(SIGSEGV, &action, nullptr) == 0);
// On Linux, SIGSYS is reserved by the kernel for seccomp-bpf sandboxing.
#if !defined(OS_LINUX)
success &= (sigaction(SIGSYS, &action, nullptr) == 0);
#endif // !defined(OS_LINUX)
return success;
}
void SetStackDumpFirstChanceCallback(bool (*handler)(int, void*, void*)) {
DCHECK(try_handle_signal == nullptr || handler == nullptr);
try_handle_signal = handler;
}
StackTrace::StackTrace(size_t count) {
// NOTE: This code MUST be async-signal safe (it's used by in-process
// stack dumping signal handler). NO malloc or stdio is allowed here.
#if !defined(__UCLIBC__) && !defined(_AIX)
count = std::min(arraysize(trace_), count);
// Though the backtrace API man page does not list any possible negative
// return values, we take no chance.
count_ = base::saturated_cast<size_t>(backtrace(trace_, count));
#else
count_ = 0;
#endif
}
void StackTrace::PrintWithPrefix(const char* prefix_string) const {
// NOTE: This code MUST be async-signal safe (it's used by in-process
// stack dumping signal handler). NO malloc or stdio is allowed here.
#if !defined(__UCLIBC__) && !defined(_AIX)
PrintBacktraceOutputHandler handler;
ProcessBacktrace(trace_, count_, prefix_string, &handler);
#endif
}
#if !defined(__UCLIBC__) && !defined(_AIX)
void StackTrace::OutputToStreamWithPrefix(std::ostream* os,
const char* prefix_string) const {
StreamBacktraceOutputHandler handler(os);
ProcessBacktrace(trace_, count_, prefix_string, &handler);
}
#endif
namespace internal {
// NOTE: code from sandbox/linux/seccomp-bpf/demo.cc.
char* itoa_r(intptr_t i, char* buf, size_t sz, int base, size_t padding) {
// Make sure we can write at least one NUL byte.
size_t n = 1;
if (n > sz)
return nullptr;
if (base < 2 || base > 16) {
buf[0] = '\000';
return nullptr;
}
char* start = buf;
uintptr_t j = i;
// Handle negative numbers (only for base 10).
if (i < 0 && base == 10) {
// This does "j = -i" while avoiding integer overflow.
j = static_cast<uintptr_t>(-(i + 1)) + 1;
// Make sure we can write the '-' character.
if (++n > sz) {
buf[0] = '\000';
return nullptr;
}
*start++ = '-';
}
// Loop until we have converted the entire number. Output at least one
// character (i.e. '0').
char* ptr = start;
do {
// Make sure there is still enough space left in our output buffer.
if (++n > sz) {
buf[0] = '\000';
return nullptr;
}
// Output the next digit.
*ptr++ = "0123456789abcdef"[j % base];
j /= base;
if (padding > 0)
padding--;
} while (j > 0 || padding > 0);
// Terminate the output with a NUL character.
*ptr = '\000';
// Conversion to ASCII actually resulted in the digits being in reverse
// order. We can't easily generate them in forward order, as we can't tell
// the number of characters needed until we are done converting.
// So, now, we reverse the string (except for the possible "-" sign).
while (--ptr > start) {
char ch = *ptr;
*ptr = *start;
*start++ = ch;
}
return buf;
}
} // namespace internal
} // namespace debug
} // namespace base