base/debug/debugger_posix.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/debug/debugger.h"
   6 #include "build/build_config.h"
   7
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <sys/param.h>
  13 #include <sys/stat.h>
  14 #include <sys/types.h>
  15 #include <unistd.h>
  16
  17 #include <string>
  18 #include <vector>
  19
  20 #if !defined(OS_ANDROID) && !defined(OS_NACL)
  21 #include <execinfo.h>
  22 #endif
  23
  24 #if defined(__GLIBCXX__)
  25 #include <cxxabi.h>
  26 #endif
  27
  28 #if defined(OS_MACOSX)
  29 #include <AvailabilityMacros.h>
  30 #endif
  31
  32 #if defined(OS_MACOSX) || defined(OS_BSD)
  33 #include <sys/sysctl.h>
  34 #endif
  35
  36 #if defined(OS_FREEBSD)
  37 #include <sys/user.h>
  38 #endif
  39
  40 #include <ostream>
  41
  42 #include "base/basictypes.h"
  43 #include "base/logging.h"
  44 #include "base/memory/scoped_ptr.h"
  45 #include "base/posix/eintr_wrapper.h"
  46 #include "base/safe_strerror_posix.h"
  47 #include "base/stringprintf.h"
  48 #include "base/strings/string_piece.h"
  49
  50 #if defined(USE_SYMBOLIZE)
  51 #include "base/third_party/symbolize/symbolize.h"
  52 #endif
  53
  54 #if defined(OS_ANDROID)
  55 #include "base/threading/platform_thread.h"
  56 #endif
  57
  58 namespace base {
  59 namespace debug {
  60
  61 bool SpawnDebuggerOnProcess(unsigned process_id) {
  62 #if OS_ANDROID || OS_NACL
  63   NOTIMPLEMENTED();
  64   return false;
  65 #else
  66   const std::string debug_cmd =
  67       StringPrintf("xterm -e 'gdb --pid=%u' &", process_id);
  68   LOG(WARNING) << "Starting debugger on pid " << process_id
  69                << " with command `" << debug_cmd << "`";
  70   int ret = system(debug_cmd.c_str());
  71   if (ret == -1)
  72     return false;
  73   return true;
  74 #endif
  75 }
  76
  77 #if defined(OS_MACOSX) || defined(OS_BSD)
  78
  79 // Based on Apple's recommended method as described in
  80 // http://developer.apple.com/qa/qa2004/qa1361.html
  81 bool BeingDebugged() {
  82   // NOTE: This code MUST be async-signal safe (it's used by in-process
  83   // stack dumping signal handler). NO malloc or stdio is allowed here.
  84   //
  85   // While some code used below may be async-signal unsafe, note how
  86   // the result is cached (see |is_set| and |being_debugged| static variables
  87   // right below). If this code is properly warmed-up early
  88   // in the start-up process, it should be safe to use later.
  89
  90   // If the process is sandboxed then we can't use the sysctl, so cache the
  91   // value.
  92   static bool is_set = false;
  93   static bool being_debugged = false;
  94
  95   if (is_set)
  96     return being_debugged;
  97
  98   // Initialize mib, which tells sysctl what info we want.  In this case,
  99   // we're looking for information about a specific process ID.
 100   int mib[] = {
 101     CTL_KERN,
 102     KERN_PROC,
 103     KERN_PROC_PID,
 104     getpid()
 105 #if defined(OS_OPENBSD)
 106     , sizeof(struct kinfo_proc),
 107     0
 108 #endif
 109   };
 110
 111   // Caution: struct kinfo_proc is marked __APPLE_API_UNSTABLE.  The source and
 112   // binary interfaces may change.
 113   struct kinfo_proc info;
 114   size_t info_size = sizeof(info);
 115
 116 #if defined(OS_OPENBSD)
 117   if (sysctl(mib, arraysize(mib), NULL, &info_size, NULL, 0) < 0)
 118     return -1;
 119
 120   mib[5] = (info_size / sizeof(struct kinfo_proc));
 121 #endif
 122
 123   int sysctl_result = sysctl(mib, arraysize(mib), &info, &info_size, NULL, 0);
 124   DCHECK_EQ(sysctl_result, 0);
 125   if (sysctl_result != 0) {
 126     is_set = true;
 127     being_debugged = false;
 128     return being_debugged;
 129   }
 130
 131   // This process is being debugged if the P_TRACED flag is set.
 132   is_set = true;
 133 #if defined(OS_FREEBSD)
 134   being_debugged = (info.ki_flag & P_TRACED) != 0;
 135 #elif defined(OS_BSD)
 136   being_debugged = (info.p_flag & P_TRACED) != 0;
 137 #else
 138   being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;
 139 #endif
 140   return being_debugged;
 141 }
 142
 143 #elif defined(OS_LINUX) || defined(OS_ANDROID)
 144
 145 // We can look in /proc/self/status for TracerPid.  We are likely used in crash
 146 // handling, so we are careful not to use the heap or have side effects.
 147 // Another option that is common is to try to ptrace yourself, but then we
 148 // can't detach without forking(), and that's not so great.
 149 // static
 150 bool BeingDebugged() {
 151   // NOTE: This code MUST be async-signal safe (it's used by in-process
 152   // stack dumping signal handler). NO malloc or stdio is allowed here.
 153
 154   int status_fd = open("/proc/self/status", O_RDONLY);
 155   if (status_fd == -1)
 156     return false;
 157
 158   // We assume our line will be in the first 1024 characters and that we can
 159   // read this much all at once.  In practice this will generally be true.
 160   // This simplifies and speeds up things considerably.
 161   char buf[1024];
 162
 163   ssize_t num_read = HANDLE_EINTR(read(status_fd, buf, sizeof(buf)));
 164   if (HANDLE_EINTR(close(status_fd)) < 0)
 165     return false;
 166
 167   if (num_read <= 0)
 168     return false;
 169
 170   StringPiece status(buf, num_read);
 171   StringPiece tracer("TracerPid:\t");
 172
 173   StringPiece::size_type pid_index = status.find(tracer);
 174   if (pid_index == StringPiece::npos)
 175     return false;
 176
 177   // Our pid is 0 without a debugger, assume this for any pid starting with 0.
 178   pid_index += tracer.size();
 179   return pid_index < status.size() && status[pid_index] != '0';
 180 }
 181
 182 #else
 183
 184 bool BeingDebugged() {
 185   NOTIMPLEMENTED();
 186   return false;
 187 }
 188
 189 #endif
 190
 191 // We want to break into the debugger in Debug mode, and cause a crash dump in
 192 // Release mode. Breakpad behaves as follows:
 193 //
 194 // +-------+-----------------+-----------------+
 195 // | OS    | Dump on SIGTRAP | Dump on SIGABRT |
 196 // +-------+-----------------+-----------------+
 197 // | Linux |       N         |        Y        |
 198 // | Mac   |       Y         |        N        |
 199 // +-------+-----------------+-----------------+
 200 //
 201 // Thus we do the following:
 202 // Linux: Debug mode, send SIGTRAP; Release mode, send SIGABRT.
 203 // Mac: Always send SIGTRAP.
 204
 205 #if defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
 206 #define DEBUG_BREAK() abort()
 207 #elif defined(OS_NACL)
 208 // The NaCl verifier doesn't let use use int3.  For now, we call abort().  We
 209 // should ask for advice from some NaCl experts about the optimum thing here.
 210 // http://code.google.com/p/nativeclient/issues/detail?id=645
 211 #define DEBUG_BREAK() abort()
 212 #elif defined(ARCH_CPU_ARM_FAMILY)
 213 #if defined(OS_ANDROID)
 214 // Though Android has a "helpful" process called debuggerd to catch native
 215 // signals on the general assumption that they are fatal errors. The bkpt
 216 // instruction appears to cause SIGBUS which is trapped by debuggerd, and
 217 // we've had great difficulty continuing in a debugger once we stop from
 218 // SIG triggered by native code.
 219 //
 220 // Use GDB to set |go| to 1 to resume execution.
 221 namespace {
 222 void DebugBreak() {
 223   if (!BeingDebugged()) {
 224     abort();
 225   } else {
 226     volatile int go = 0;
 227     while (!go) {
 228       base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
 229     }
 230   }
 231 }
 232 }  // namespace
 233 #define DEBUG_BREAK() DebugBreak()
 234 #else
 235 // ARM && !ANDROID
 236 #define DEBUG_BREAK() asm("bkpt 0")
 237 #endif
 238 #elif defined(ARCH_CPU_MIPS_FAMILY)
 239 #define DEBUG_BREAK() asm("break 2")
 240 #else
 241 #define DEBUG_BREAK() asm("int3")
 242 #endif
 243
 244 void BreakDebugger() {
 245   // NOTE: This code MUST be async-signal safe (it's used by in-process
 246   // stack dumping signal handler). NO malloc or stdio is allowed here.
 247
 248   DEBUG_BREAK();
 249 #if defined(OS_ANDROID) && !defined(OFFICIAL_BUILD)
 250   // For Android development we always build release (debug builds are
 251   // unmanageably large), so the unofficial build is used for debugging. It is
 252   // helpful to be able to insert BreakDebugger() statements in the source,
 253   // attach the debugger, inspect the state of the program and then resume it by
 254   // setting the 'go' variable above.
 255 #elif defined(NDEBUG)
 256   // Terminate the program after signaling the debug break.
 257   _exit(1);
 258 #endif
 259 }
 260
 261 }  // namespace debug
 262 }  // namespace base