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
BeingDebugged()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 {
DebugBreak()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
BreakDebugger()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
256