// 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 "butil/debug/debugger.h"

#include "butil/build_config.h"

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <sys/param.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#include <vector>

#if defined(__GLIBCXX__)

#include <cxxabi.h>

#endif

#if defined(OS_MACOSX)

#include <AvailabilityMacros.h>

#endif

#if defined(OS_MACOSX) || defined(OS_BSD)

#include <sys/sysctl.h>

#endif

#if defined(OS_FREEBSD)

#include <sys/user.h>

#endif

#include <ostream>

#include "butil/basictypes.h"

#include "butil/logging.h"

#include "butil/memory/scoped_ptr.h"

#include "butil/posix/eintr_wrapper.h"

#include "butil/safe_strerror_posix.h"

#include "butil/strings/string_piece.h"

#if defined(USE_SYMBOLIZE)

#include "butil/third_party/symbolize/symbolize.h"

#endif

#if defined(OS_ANDROID)

#include "butil/threading/platform_thread.h"

#endif

namespace butil {

namespace debug {

#if defined(OS_MACOSX) || defined(OS_BSD)

// Based on Apple's recommended method as described in

// http://developer.apple.com/qa/qa2004/qa1361.html

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[] = {

    CTL_KERN,

    KERN_PROC,

    KERN_PROC_PID,

    getpid()

#if defined(OS_OPENBSD)

    , sizeof(struct kinfo_proc),

    0

#endif

  };

  // 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));

#endif

  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;

#else

  being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;

#endif

  return being_debugged;

}

#elif defined(OS_LINUX) || defined(OS_ANDROID)

// 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';

}

#else

bool BeingDebugged() {

  NOTIMPLEMENTED();

  return false;

}

#endif

// 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

//        SIGABRT

// 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_LOONGARCH64_FAMILY)

#define DEBUG_BREAK_ASM() asm("break 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")

#endif

#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.

// http://code.google.com/p/nativeclient/issues/detail?id=645

#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()) {

    abort();

  } else {

#if defined(DEBUG_BREAK_ASM)

    DEBUG_BREAK_ASM();

#else

    volatile int go = 0;

    while (!go) {

      butil::PlatformThread::Sleep(butil::TimeDelta::FromMilliseconds(100));

    }

#endif

  }

}

}  // namespace

#define DEBUG_BREAK() DebugBreak()

#elif defined(DEBUG_BREAK_ASM)

#define DEBUG_BREAK() DEBUG_BREAK_ASM()

#else

#error "Don't know how to debug break on this architecture/OS"

#endif

void BreakDebugger() {

  // 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.

  DEBUG_BREAK();

#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.

  _exit(1);

#endif

}

}  // namespace debug

}  // namespace butil