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