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(__GLIBCXX__)
  21 #include <cxxabi.h>
  22 #endif
  23
  24 #if defined(OS_MACOSX)
  25 #include <AvailabilityMacros.h>
  26 #endif
  27
  28 #if defined(OS_MACOSX) || defined(OS_BSD)
  29 #include <sys/sysctl.h>
  30 #endif
  31
  32 #if defined(OS_FREEBSD)
  33 #include <sys/user.h>
  34 #endif
  35
  36 #include <ostream>
  37
  38 #include "base/basictypes.h"
  39 #include "base/logging.h"
  40 #include "base/memory/scoped_ptr.h"
  41 #include "base/posix/eintr_wrapper.h"
  42 #include "base/safe_strerror_posix.h"
  43 #include "base/stringprintf.h"
  44 #include "base/strings/string_piece.h"
  45
  46 #if defined(USE_SYMBOLIZE)
  47 #include "base/third_party/symbolize/symbolize.h"
  48 #endif
  49
  50 #if defined(OS_ANDROID)
  51 #include "base/threading/platform_thread.h"
  52 #endif
  53
  54 namespace base {
  55 namespace debug {
  56
  57 bool SpawnDebuggerOnProcess(unsigned process_id) {
  58 #if OS_ANDROID || OS_NACL
  59   NOTIMPLEMENTED();
  60   return false;
  61 #else
  62   const std::string debug_cmd =
  63       StringPrintf("xterm -e 'gdb --pid=%u' &", process_id);
  64   LOG(WARNING) << "Starting debugger on pid " << process_id
  65                << " with command `" << debug_cmd << "`";
  66   int ret = system(debug_cmd.c_str());
  67   if (ret == -1)
  68     return false;
  69   return true;
  70 #endif
  71 }
  72
  73 #if defined(OS_MACOSX) || defined(OS_BSD)
  74
  75 // Based on Apple's recommended method as described in
  76 // http://developer.apple.com/qa/qa2004/qa1361.html
  77 bool BeingDebugged() {
  78   // NOTE: This code MUST be async-signal safe (it's used by in-process
  79   // stack dumping signal handler). NO malloc or stdio is allowed here.
  80   //
  81   // While some code used below may be async-signal unsafe, note how
  82   // the result is cached (see |is_set| and |being_debugged| static variables
  83   // right below). If this code is properly warmed-up early
  84   // in the start-up process, it should be safe to use later.
  85
  86   // If the process is sandboxed then we can't use the sysctl, so cache the
  87   // value.
  88   static bool is_set = false;
  89   static bool being_debugged = false;
  90
  91   if (is_set)
  92     return being_debugged;
  93
  94   // Initialize mib, which tells sysctl what info we want.  In this case,
  95   // we're looking for information about a specific process ID.
  96   int mib[] = {
  97     CTL_KERN,
  98     KERN_PROC,
  99     KERN_PROC_PID,
 100     getpid()
 101 #if defined(OS_OPENBSD)
 102     , sizeof(struct kinfo_proc),
 103     0
 104 #endif
 105   };
 106
 107   // Caution: struct kinfo_proc is marked __APPLE_API_UNSTABLE.  The source and
 108   // binary interfaces may change.
 109   struct kinfo_proc info;
 110   size_t info_size = sizeof(info);
 111
 112 #if defined(OS_OPENBSD)
 113   if (sysctl(mib, arraysize(mib), NULL, &info_size, NULL, 0) < 0)
 114     return -1;
 115
 116   mib[5] = (info_size / sizeof(struct kinfo_proc));
 117 #endif
 118
 119   int sysctl_result = sysctl(mib, arraysize(mib), &info, &info_size, NULL, 0);
 120   DCHECK_EQ(sysctl_result, 0);
 121   if (sysctl_result != 0) {
 122     is_set = true;
 123     being_debugged = false;
 124     return being_debugged;
 125   }
 126
 127   // This process is being debugged if the P_TRACED flag is set.
 128   is_set = true;
 129 #if defined(OS_FREEBSD)
 130   being_debugged = (info.ki_flag & P_TRACED) != 0;
 131 #elif defined(OS_BSD)
 132   being_debugged = (info.p_flag & P_TRACED) != 0;
 133 #else
 134   being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;
 135 #endif
 136   return being_debugged;
 137 }
 138
 139 #elif defined(OS_LINUX) || defined(OS_ANDROID)
 140
 141 // We can look in /proc/self/status for TracerPid.  We are likely used in crash
 142 // handling, so we are careful not to use the heap or have side effects.
 143 // Another option that is common is to try to ptrace yourself, but then we
 144 // can't detach without forking(), and that's not so great.
 145 // static
 146 bool BeingDebugged() {
 147   // NOTE: This code MUST be async-signal safe (it's used by in-process
 148   // stack dumping signal handler). NO malloc or stdio is allowed here.
 149
 150   int status_fd = open("/proc/self/status", O_RDONLY);
 151   if (status_fd == -1)
 152     return false;
 153
 154   // We assume our line will be in the first 1024 characters and that we can
 155   // read this much all at once.  In practice this will generally be true.
 156   // This simplifies and speeds up things considerably.
 157   char buf[1024];
 158
 159   ssize_t num_read = HANDLE_EINTR(read(status_fd, buf, sizeof(buf)));
 160   if (HANDLE_EINTR(close(status_fd)) < 0)
 161     return false;
 162
 163   if (num_read <= 0)
 164     return false;
 165
 166   StringPiece status(buf, num_read);
 167   StringPiece tracer("TracerPid:\t");
 168
 169   StringPiece::size_type pid_index = status.find(tracer);
 170   if (pid_index == StringPiece::npos)
 171     return false;
 172
 173   // Our pid is 0 without a debugger, assume this for any pid starting with 0.
 174   pid_index += tracer.size();
 175   return pid_index < status.size() && status[pid_index] != '0';
 176 }
 177
 178 #else
 179
 180 bool BeingDebugged() {
 181   NOTIMPLEMENTED();
 182   return false;
 183 }
 184
 185 #endif
 186
 187 // We want to break into the debugger in Debug mode, and cause a crash dump in
 188 // Release mode. Breakpad behaves as follows:
 189 //
 190 // +-------+-----------------+-----------------+
 191 // | OS    | Dump on SIGTRAP | Dump on SIGABRT |
 192 // +-------+-----------------+-----------------+
 193 // | Linux |       N         |        Y        |
 194 // | Mac   |       Y         |        N        |
 195 // +-------+-----------------+-----------------+
 196 //
 197 // Thus we do the following:
 198 // Linux: Debug mode, send SIGTRAP; Release mode, send SIGABRT.
 199 // Mac: Always send SIGTRAP.
 200
 201 #if defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
 202 #define DEBUG_BREAK() abort()
 203 #elif defined(OS_NACL)
 204 // The NaCl verifier doesn't let use use int3.  For now, we call abort().  We
 205 // should ask for advice from some NaCl experts about the optimum thing here.
 206 // http://code.google.com/p/nativeclient/issues/detail?id=645
 207 #define DEBUG_BREAK() abort()
 208 #elif defined(OS_ANDROID)
 209 // Though Android has a "helpful" process called debuggerd to catch native
 210 // signals on the general assumption that they are fatal errors. If no debugger
 211 // is attached, we call abort since Breakpad needs SIGABRT to create a dump.
 212 // When debugger is attached, for ARM platform the bkpt instruction appears
 213 // to cause SIGBUS which is trapped by debuggerd, and we've had great
 214 // difficulty continuing in a debugger once we stop from SIG triggered by native
 215 // code, use GDB to set |go| to 1 to resume execution; for X86 platform, use
 216 // "int3" to setup breakpiont and raise SIGTRAP.
 217 namespace {
 218 void DebugBreak() {
 219   if (!BeingDebugged()) {
 220     abort();
 221   } else {
 222 #if defined(ARCH_CPU_X86_FAMILY)
 223     asm("int3");
 224 #else
 225     volatile int go = 0;
 226     while (!go) {
 227       base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
 228     }
 229 #endif
 230   }
 231 }
 232 }  // namespace
 233 #define DEBUG_BREAK() DebugBreak()
 234 #elif defined(ARCH_CPU_ARM_FAMILY)
 235 // ARM && !ANDROID
 236 #define DEBUG_BREAK() asm("bkpt 0")
 237 #elif defined(ARCH_CPU_MIPS_FAMILY)
 238 #define DEBUG_BREAK() asm("break 2")
 239 #else
 240 #define DEBUG_BREAK() asm("int3")
 241 #endif
 242
 243 void BreakDebugger() {
 244   // NOTE: This code MUST be async-signal safe (it's used by in-process
 245   // stack dumping signal handler). NO malloc or stdio is allowed here.
 246
 247   DEBUG_BREAK();
 248 #if defined(OS_ANDROID) && !defined(OFFICIAL_BUILD)
 249   // For Android development we always build release (debug builds are
 250   // unmanageably large), so the unofficial build is used for debugging. It is
 251   // helpful to be able to insert BreakDebugger() statements in the source,
 252   // attach the debugger, inspect the state of the program and then resume it by
 253   // setting the 'go' variable above.
 254 #elif defined(NDEBUG)
 255   // Terminate the program after signaling the debug break.
 256   _exit(1);
 257 #endif
 258 }
 259
 260 }  // namespace debug
 261 }  // namespace base