blob: 150a7d8ffed2a9926b94f9f3ddc507aa59ec4fbe [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/debugger.h"
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <memory>
#include <vector>
#include "base/macros.h"
#include "base/test/clang_coverage.h"
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
#include "build/build_config.h"
#if defined(__GLIBCXX__)
#include <cxxabi.h>
#if defined(OS_MACOSX)
#include <AvailabilityMacros.h>
#if defined(OS_MACOSX) || defined(OS_BSD)
#include <sys/sysctl.h>
#if defined(OS_FREEBSD)
#include <sys/user.h>
#include <ostream>
#include "base/debug/alias.h"
#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"
#include "base/strings/string_piece.h"
#if defined(USE_SYMBOLIZE)
#include "base/third_party/symbolize/symbolize.h"
#if defined(OS_ANDROID)
#include "base/threading/platform_thread.h"
namespace base {
namespace debug {
#if defined(OS_MACOSX) || defined(OS_BSD)
// Based on Apple's recommended method as described in
bool BeingDebugged() {
// 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.
// While some code used below may be async-signal unsafe, note how
// the result is cached (see |is_set| and |being_debugged| static variables
// right below). If this code is properly warmed-up early
// in the start-up process, it should be safe to use later.
// If the process is sandboxed then we can't use the sysctl, so cache the
// value.
static bool is_set = false;
static bool being_debugged = false;
if (is_set)
return being_debugged;
// Initialize mib, which tells sysctl what info we want. In this case,
// we're looking for information about a specific process ID.
int mib[] = {
#if defined(OS_OPENBSD)
, sizeof(struct kinfo_proc),
// Caution: struct kinfo_proc is marked __APPLE_API_UNSTABLE. The source and
// binary interfaces may change.
struct kinfo_proc info;
size_t info_size = sizeof(info);
#if defined(OS_OPENBSD)
if (sysctl(mib, arraysize(mib), NULL, &info_size, NULL, 0) < 0)
return -1;
mib[5] = (info_size / sizeof(struct kinfo_proc));
int sysctl_result = sysctl(mib, arraysize(mib), &info, &info_size, NULL, 0);
DCHECK_EQ(sysctl_result, 0);
if (sysctl_result != 0) {
is_set = true;
being_debugged = false;
return being_debugged;
// This process is being debugged if the P_TRACED flag is set.
is_set = true;
#if defined(OS_FREEBSD)
being_debugged = (info.ki_flag & P_TRACED) != 0;
#elif defined(OS_BSD)
being_debugged = (info.p_flag & P_TRACED) != 0;
being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;
return being_debugged;
#elif defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_AIX)
// We can look in /proc/self/status for TracerPid. We are likely used in crash
// handling, so we are careful not to use the heap or have side effects.
// Another option that is common is to try to ptrace yourself, but then we
// can't detach without forking(), and that's not so great.
// static
bool BeingDebugged() {
// 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.
int status_fd = open("/proc/self/status", O_RDONLY);
if (status_fd == -1)
return false;
// We assume our line will be in the first 1024 characters and that we can
// read this much all at once. In practice this will generally be true.
// This simplifies and speeds up things considerably.
char buf[1024];
ssize_t num_read = HANDLE_EINTR(read(status_fd, buf, sizeof(buf)));
if (IGNORE_EINTR(close(status_fd)) < 0)
return false;
if (num_read <= 0)
return false;
StringPiece status(buf, num_read);
StringPiece tracer("TracerPid:\t");
StringPiece::size_type pid_index = status.find(tracer);
if (pid_index == StringPiece::npos)
return false;
// Our pid is 0 without a debugger, assume this for any pid starting with 0.
pid_index += tracer.size();
return pid_index < status.size() && status[pid_index] != '0';
#elif defined(OS_FUCHSIA)
bool BeingDebugged() {
// TODO(fuchsia): No gdb/gdbserver in the SDK yet.
return false;
bool BeingDebugged() {
return false;
// We want to break into the debugger in Debug mode, and cause a crash dump in
// Release mode. Breakpad behaves as follows:
// +-------+-----------------+-----------------+
// | OS | Dump on SIGTRAP | Dump on SIGABRT |
// +-------+-----------------+-----------------+
// | Linux | N | Y |
// | Mac | Y | N |
// +-------+-----------------+-----------------+
// Thus we do the following:
// Linux: Debug mode if a debugger is attached, send SIGTRAP; otherwise send
// Mac: Always send SIGTRAP.
#if defined(ARCH_CPU_ARMEL)
#define DEBUG_BREAK_ASM() asm("bkpt 0")
#elif defined(ARCH_CPU_ARM64)
#define DEBUG_BREAK_ASM() asm("brk 0")
#elif defined(ARCH_CPU_MIPS_FAMILY)
#define DEBUG_BREAK_ASM() asm("break 2")
#elif defined(ARCH_CPU_X86_FAMILY)
#define DEBUG_BREAK_ASM() asm("int3")
#if defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
#define DEBUG_BREAK() abort()
#elif defined(OS_NACL)
// The NaCl verifier doesn't let use use int3. For now, we call abort(). We
// should ask for advice from some NaCl experts about the optimum thing here.
#define DEBUG_BREAK() abort()
#elif !defined(OS_MACOSX)
// Though Android has a "helpful" process called debuggerd to catch native
// signals on the general assumption that they are fatal errors. If no debugger
// is attached, we call abort since Breakpad needs SIGABRT to create a dump.
// When debugger is attached, for ARM platform the bkpt instruction appears
// to cause SIGBUS which is trapped by debuggerd, and we've had great
// difficulty continuing in a debugger once we stop from SIG triggered by native
// code, use GDB to set |go| to 1 to resume execution; for X86 platform, use
// "int3" to setup breakpiont and raise SIGTRAP.
// On other POSIX architectures, except Mac OS X, we use the same logic to
// ensure that breakpad creates a dump on crashes while it is still possible to
// use a debugger.
namespace {
void DebugBreak() {
if (!BeingDebugged()) {
} else {
#if defined(DEBUG_BREAK_ASM)
volatile int go = 0;
while (!go) {
} // namespace
#define DEBUG_BREAK() DebugBreak()
#elif defined(DEBUG_BREAK_ASM)
#error "Don't know how to debug break on this architecture/OS"
void BreakDebugger() {
#if defined(CLANG_COVERAGE)
// 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.
// Linker's ICF feature may merge this function with other functions with the
// same definition (e.g. any function whose sole job is to call abort()) and
// it may confuse the crash report processing system.
static int static_variable_to_make_this_function_unique = 0;
#if defined(OS_ANDROID) && !defined(OFFICIAL_BUILD)
// For Android development we always build release (debug builds are
// unmanageably large), so the unofficial build is used for debugging. It is
// helpful to be able to insert BreakDebugger() statements in the source,
// attach the debugger, inspect the state of the program and then resume it by
// setting the 'go' variable above.
#elif defined(NDEBUG)
// Terminate the program after signaling the debug break.
} // namespace debug
} // namespace base