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
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <stddef.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 <memory>
18 #include <vector>
19
20 #include "base/macros.h"
21 #include "build/build_config.h"
22
23 #if defined(__GLIBCXX__)
24 #include <cxxabi.h>
25 #endif
26
27 #if defined(OS_MACOSX)
28 #include <AvailabilityMacros.h>
29 #endif
30
31 #if defined(OS_MACOSX) || defined(OS_BSD)
32 #include <sys/sysctl.h>
33 #endif
34
35 #if defined(OS_FREEBSD)
36 #include <sys/user.h>
37 #endif
38
39 #include <ostream>
40
41 #include "base/debug/alias.h"
42 #include "base/logging.h"
43 #include "base/posix/eintr_wrapper.h"
44 #include "base/strings/string_piece.h"
45
46 #if defined(USE_SYMBOLIZE)
47 #error "symbolize support was removed from libchrome"
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 #if defined(OS_MACOSX) || defined(OS_BSD)
58
59 // Based on Apple's recommended method as described in
60 // http://developer.apple.com/qa/qa2004/qa1361.html
BeingDebugged()61 bool BeingDebugged() {
62 // NOTE: This code MUST be async-signal safe (it's used by in-process
63 // stack dumping signal handler). NO malloc or stdio is allowed here.
64 //
65 // While some code used below may be async-signal unsafe, note how
66 // the result is cached (see |is_set| and |being_debugged| static variables
67 // right below). If this code is properly warmed-up early
68 // in the start-up process, it should be safe to use later.
69
70 // If the process is sandboxed then we can't use the sysctl, so cache the
71 // value.
72 static bool is_set = false;
73 static bool being_debugged = false;
74
75 if (is_set)
76 return being_debugged;
77
78 // Initialize mib, which tells sysctl what info we want. In this case,
79 // we're looking for information about a specific process ID.
80 int mib[] = {
81 CTL_KERN,
82 KERN_PROC,
83 KERN_PROC_PID,
84 getpid()
85 #if defined(OS_OPENBSD)
86 , sizeof(struct kinfo_proc),
87 0
88 #endif
89 };
90
91 // Caution: struct kinfo_proc is marked __APPLE_API_UNSTABLE. The source and
92 // binary interfaces may change.
93 struct kinfo_proc info;
94 size_t info_size = sizeof(info);
95
96 #if defined(OS_OPENBSD)
97 if (sysctl(mib, arraysize(mib), NULL, &info_size, NULL, 0) < 0)
98 return -1;
99
100 mib[5] = (info_size / sizeof(struct kinfo_proc));
101 #endif
102
103 int sysctl_result = sysctl(mib, arraysize(mib), &info, &info_size, NULL, 0);
104 DCHECK_EQ(sysctl_result, 0);
105 if (sysctl_result != 0) {
106 is_set = true;
107 being_debugged = false;
108 return being_debugged;
109 }
110
111 // This process is being debugged if the P_TRACED flag is set.
112 is_set = true;
113 #if defined(OS_FREEBSD)
114 being_debugged = (info.ki_flag & P_TRACED) != 0;
115 #elif defined(OS_BSD)
116 being_debugged = (info.p_flag & P_TRACED) != 0;
117 #else
118 being_debugged = (info.kp_proc.p_flag & P_TRACED) != 0;
119 #endif
120 return being_debugged;
121 }
122
123 #elif defined(OS_LINUX) || defined(OS_ANDROID)
124
125 // We can look in /proc/self/status for TracerPid. We are likely used in crash
126 // handling, so we are careful not to use the heap or have side effects.
127 // Another option that is common is to try to ptrace yourself, but then we
128 // can't detach without forking(), and that's not so great.
129 // static
130 bool BeingDebugged() {
131 // NOTE: This code MUST be async-signal safe (it's used by in-process
132 // stack dumping signal handler). NO malloc or stdio is allowed here.
133
134 int status_fd = open("/proc/self/status", O_RDONLY);
135 if (status_fd == -1)
136 return false;
137
138 // We assume our line will be in the first 1024 characters and that we can
139 // read this much all at once. In practice this will generally be true.
140 // This simplifies and speeds up things considerably.
141 char buf[1024];
142
143 ssize_t num_read = HANDLE_EINTR(read(status_fd, buf, sizeof(buf)));
144 if (IGNORE_EINTR(close(status_fd)) < 0)
145 return false;
146
147 if (num_read <= 0)
148 return false;
149
150 StringPiece status(buf, num_read);
151 StringPiece tracer("TracerPid:\t");
152
153 StringPiece::size_type pid_index = status.find(tracer);
154 if (pid_index == StringPiece::npos)
155 return false;
156
157 // Our pid is 0 without a debugger, assume this for any pid starting with 0.
158 pid_index += tracer.size();
159 return pid_index < status.size() && status[pid_index] != '0';
160 }
161
162 #else
163
164 bool BeingDebugged() {
165 NOTIMPLEMENTED();
166 return false;
167 }
168
169 #endif
170
171 // We want to break into the debugger in Debug mode, and cause a crash dump in
172 // Release mode. Breakpad behaves as follows:
173 //
174 // +-------+-----------------+-----------------+
175 // | OS | Dump on SIGTRAP | Dump on SIGABRT |
176 // +-------+-----------------+-----------------+
177 // | Linux | N | Y |
178 // | Mac | Y | N |
179 // +-------+-----------------+-----------------+
180 //
181 // Thus we do the following:
182 // Linux: Debug mode if a debugger is attached, send SIGTRAP; otherwise send
183 // SIGABRT
184 // Mac: Always send SIGTRAP.
185
186 #if defined(ARCH_CPU_ARMEL)
187 #define DEBUG_BREAK_ASM() asm("bkpt 0")
188 #elif defined(ARCH_CPU_ARM64)
189 #define DEBUG_BREAK_ASM() asm("brk 0")
190 #elif defined(ARCH_CPU_MIPS_FAMILY)
191 #define DEBUG_BREAK_ASM() asm("break 2")
192 #elif defined(ARCH_CPU_X86_FAMILY)
193 #define DEBUG_BREAK_ASM() asm("int3")
194 #endif
195
196 #if defined(NDEBUG) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
197 #define DEBUG_BREAK() abort()
198 #elif defined(OS_NACL)
199 // The NaCl verifier doesn't let use use int3. For now, we call abort(). We
200 // should ask for advice from some NaCl experts about the optimum thing here.
201 // http://code.google.com/p/nativeclient/issues/detail?id=645
202 #define DEBUG_BREAK() abort()
203 #elif !defined(OS_MACOSX)
204 // Though Android has a "helpful" process called debuggerd to catch native
205 // signals on the general assumption that they are fatal errors. If no debugger
206 // is attached, we call abort since Breakpad needs SIGABRT to create a dump.
207 // When debugger is attached, for ARM platform the bkpt instruction appears
208 // to cause SIGBUS which is trapped by debuggerd, and we've had great
209 // difficulty continuing in a debugger once we stop from SIG triggered by native
210 // code, use GDB to set |go| to 1 to resume execution; for X86 platform, use
211 // "int3" to setup breakpiont and raise SIGTRAP.
212 //
213 // On other POSIX architectures, except Mac OS X, we use the same logic to
214 // ensure that breakpad creates a dump on crashes while it is still possible to
215 // use a debugger.
216 namespace {
DebugBreak()217 void DebugBreak() {
218 if (!BeingDebugged()) {
219 abort();
220 } else {
221 #if defined(DEBUG_BREAK_ASM)
222 DEBUG_BREAK_ASM();
223 #else
224 volatile int go = 0;
225 while (!go) {
226 base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
227 }
228 #endif
229 }
230 }
231 } // namespace
232 #define DEBUG_BREAK() DebugBreak()
233 #elif defined(DEBUG_BREAK_ASM)
234 #define DEBUG_BREAK() DEBUG_BREAK_ASM()
235 #else
236 #error "Don't know how to debug break on this architecture/OS"
237 #endif
238
BreakDebugger()239 void BreakDebugger() {
240 // NOTE: This code MUST be async-signal safe (it's used by in-process
241 // stack dumping signal handler). NO malloc or stdio is allowed here.
242
243 // Linker's ICF feature may merge this function with other functions with the
244 // same definition (e.g. any function whose sole job is to call abort()) and
245 // it may confuse the crash report processing system. http://crbug.com/508489
246 static int static_variable_to_make_this_function_unique = 0;
247 base::debug::Alias(&static_variable_to_make_this_function_unique);
248
249 DEBUG_BREAK();
250 #if defined(OS_ANDROID) && !defined(OFFICIAL_BUILD)
251 // For Android development we always build release (debug builds are
252 // unmanageably large), so the unofficial build is used for debugging. It is
253 // helpful to be able to insert BreakDebugger() statements in the source,
254 // attach the debugger, inspect the state of the program and then resume it by
255 // setting the 'go' variable above.
256 #elif defined(NDEBUG)
257 // Terminate the program after signaling the debug break.
258 _exit(1);
259 #endif
260 }
261
262 } // namespace debug
263 } // namespace base
264