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 <vector>
  18
  19 #if defined(__GLIBCXX__)
  20 #include <cxxabi.h>
  21 #endif
  22
  23 #if defined(OS_MACOSX)
  24 #include <AvailabilityMacros.h>
  25 #endif
  26
  27 #if defined(OS_MACOSX) || defined(OS_BSD)
  28 #include <sys/sysctl.h>
  29 #endif
  30
  31 #if defined(OS_FREEBSD)
  32 #include <sys/user.h>
  33 #endif
  34
  35 #include <ostream>
  36
  37 #include "base/basictypes.h"
  38 #include "base/logging.h"
  39 #include "base/memory/scoped_ptr.h"
  40 #include "base/posix/eintr_wrapper.h"
  41 #include "base/strings/string_piece.h"
  42
  43 #if defined(USE_SYMBOLIZE)
  44 #include "base/third_party/symbolize/symbolize.h"
  45 #endif
  46
  47 #if defined(OS_ANDROID)
  48 #include "base/threading/platform_thread.h"
  49 #endif
  50
  51 namespace base {
  52 namespace debug {
  53
  54 #if defined(OS_MACOSX) || defined(OS_BSD)
  55
  56 // Based on Apple's recommended method as described in
  57 // http://developer.apple.com/qa/qa2004/qa1361.html
  58 bool BeingDebugged() {
  59   // NOTE: This code MUST be async-signal safe (it's used by in-process
  60   // stack dumping signal handler). NO malloc or stdio is allowed here.
  61   //
  62   // While some code used below may be async-signal unsafe, note how
  63   // the result is cached (see |is_set| and |being_debugged| static variables
  64   // right below). If this code is properly warmed-up early
  65   // in the start-up process, it should be safe to use later.
  66
  67   // If the process is sandboxed then we can't use the sysctl, so cache the
  68   // value.
  69   static bool is_set = false;
  70   static bool being_debugged = false;
  71
  72   if (is_set)
  73     return being_debugged;
  74
  75   // Initialize mib, which tells sysctl what info we want.  In this case,
  76   // we're looking for information about a specific process ID.
  77   int mib[] = {
  78     CTL_KERN,
  79     KERN_PROC,
  80     KERN_PROC_PID,
  81     getpid()
  82 #if defined(OS_OPENBSD)
  83     , sizeof(struct kinfo_proc),
  84     0
  85 #endif
  86   };
  87
  88   // Caution: struct kinfo_proc is marked __APPLE_API_UNSTABLE.  The source and
  89   // binary interfaces may change.
  90   struct kinfo_proc info;
  91   size_t info_size = sizeof(info);
  92
  93 #if defined(OS_OPENBSD)
  94   if (sysctl(mib, arraysize(mib), NULL, &info_size, NULL, 0) < 0)
  95     return -1;
  96
  97   mib[5] = (info_size / sizeof(struct kinfo_proc));
  98 #endif
  99
 100   int sysctl_result = sysctl(mib, arraysize(mib), &info, &info_size, NULL, 0);
 101   DCHECK_EQ(sysctl_result, 0);
 102   if (sysctl_result != 0) {
 103     is_set = true;
 104     being_debugged = false;
 105     return being_debugged;
 106   }
 107
 108   // This process is being debugged if the P_TRACED flag is set.
 109   is_set = true;
 110 #if defined(OS_FREEBSD)
 111   being_debugged = (info.ki_flag & P_TRACED) != 0;
 112 #elif defined(OS_BSD)
 113   being_debugged = (info.p_flag & P_TRACED) != 0;
 114 #else
 115   being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;
 116 #endif
 117   return being_debugged;
 118 }
 119
 120 #elif defined(OS_LINUX) || defined(OS_ANDROID)
 121
 122 // We can look in /proc/self/status for TracerPid.  We are likely used in crash
 123 // handling, so we are careful not to use the heap or have side effects.
 124 // Another option that is common is to try to ptrace yourself, but then we
 125 // can't detach without forking(), and that's not so great.
 126 // static
 127 bool BeingDebugged() {
 128   // NOTE: This code MUST be async-signal safe (it's used by in-process
 129   // stack dumping signal handler). NO malloc or stdio is allowed here.
 130
 131   int status_fd = open("/proc/self/status", O_RDONLY);
 132   if (status_fd == -1)
 133     return false;
 134
 135   // We assume our line will be in the first 1024 characters and that we can
 136   // read this much all at once.  In practice this will generally be true.
 137   // This simplifies and speeds up things considerably.
 138   char buf[1024];
 139
 140   ssize_t num_read = HANDLE_EINTR(read(status_fd, buf, sizeof(buf)));
 141   if (IGNORE_EINTR(close(status_fd)) < 0)
 142     return false;
 143
 144   if (num_read <= 0)
 145     return false;
 146
 147   StringPiece status(buf, num_read);
 148   StringPiece tracer("TracerPid:\t");
 149
 150   StringPiece::size_type pid_index = status.find(tracer);
 151   if (pid_index == StringPiece::npos)
 152     return false;
 153
 154   // Our pid is 0 without a debugger, assume this for any pid starting with 0.
 155   pid_index += tracer.size();
 156   return pid_index < status.size() && status[pid_index] != '0';
 157 }
 158
 159 #else
 160
 161 bool BeingDebugged() {
 162   NOTIMPLEMENTED();
 163   return false;
 164 }
 165
 166 #endif
 167
 168 // We want to break into the debugger in Debug mode, and cause a crash dump in
 169 // Release mode. Breakpad behaves as follows:
 170 //
 171 // +-------+-----------------+-----------------+
 172 // | OS    | Dump on SIGTRAP | Dump on SIGABRT |
 173 // +-------+-----------------+-----------------+
 174 // | Linux |       N         |        Y        |
 175 // | Mac   |       Y         |        N        |
 176 // +-------+-----------------+-----------------+
 177 //
 178 // Thus we do the following:
 179 // Linux: Debug mode if a debugger is attached, send SIGTRAP; otherwise send
 180 //        SIGABRT
 181 // Mac: Always send SIGTRAP.
 182
 183 #if defined(ARCH_CPU_ARMEL)
 184 #define DEBUG_BREAK_ASM() asm("bkpt 0")
 185 #elif defined(ARCH_CPU_ARM64)
 186 #define DEBUG_BREAK_ASM() asm("brk 0")
 187 #elif defined(ARCH_CPU_MIPS_FAMILY)
 188 #define DEBUG_BREAK_ASM() asm("break 2")
 189 #elif defined(ARCH_CPU_X86_FAMILY)
 190 #define DEBUG_BREAK_ASM() asm("int3")
 191 #endif
 192
 193 #if defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
 194 #define DEBUG_BREAK() abort()
 195 #elif defined(OS_NACL)
 196 // The NaCl verifier doesn't let use use int3.  For now, we call abort().  We
 197 // should ask for advice from some NaCl experts about the optimum thing here.
 198 // http://code.google.com/p/nativeclient/issues/detail?id=645
 199 #define DEBUG_BREAK() abort()
 200 #elif !defined(OS_MACOSX)
 201 // Though Android has a "helpful" process called debuggerd to catch native
 202 // signals on the general assumption that they are fatal errors. If no debugger
 203 // is attached, we call abort since Breakpad needs SIGABRT to create a dump.
 204 // When debugger is attached, for ARM platform the bkpt instruction appears
 205 // to cause SIGBUS which is trapped by debuggerd, and we've had great
 206 // difficulty continuing in a debugger once we stop from SIG triggered by native
 207 // code, use GDB to set |go| to 1 to resume execution; for X86 platform, use
 208 // "int3" to setup breakpiont and raise SIGTRAP.
 209 //
 210 // On other POSIX architectures, except Mac OS X, we use the same logic to
 211 // ensure that breakpad creates a dump on crashes while it is still possible to
 212 // use a debugger.
 213 namespace {
 214 void DebugBreak() {
 215   if (!BeingDebugged()) {
 216     abort();
 217   } else {
 218 #if defined(DEBUG_BREAK_ASM)
 219     DEBUG_BREAK_ASM();
 220 #else
 221     volatile int go = 0;
 222     while (!go) {
 223       base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
 224     }
 225 #endif
 226   }
 227 }
 228 }  // namespace
 229 #define DEBUG_BREAK() DebugBreak()
 230 #elif defined(DEBUG_BREAK_ASM)
 231 #define DEBUG_BREAK() DEBUG_BREAK_ASM()
 232 #else
 233 #error "Don't know how to debug break on this architecture/OS"
 234 #endif
 235
 236 void BreakDebugger() {
 237   // NOTE: This code MUST be async-signal safe (it's used by in-process
 238   // stack dumping signal handler). NO malloc or stdio is allowed here.
 239
 240   DEBUG_BREAK();
 241 #if defined(OS_ANDROID) && !defined(OFFICIAL_BUILD)
 242   // For Android development we always build release (debug builds are
 243   // unmanageably large), so the unofficial build is used for debugging. It is
 244   // helpful to be able to insert BreakDebugger() statements in the source,
 245   // attach the debugger, inspect the state of the program and then resume it by
 246   // setting the 'go' variable above.
 247 #elif defined(NDEBUG)
 248   // Terminate the program after signaling the debug break.
 249   _exit(1);
 250 #endif
 251 }
 252
 253 }  // namespace debug
 254 }  // namespace base