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/stack_trace.h"
6
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <signal.h>
10 #include <stddef.h>
11 #include <stdint.h>
12 #include <stdio.h>
13 #include <stdlib.h>
14 #include <sys/param.h>
15 #include <sys/stat.h>
16 #include <sys/types.h>
17 #include <unistd.h>
18
19 #include <map>
20 #include <memory>
21 #include <ostream>
22 #include <string>
23 #include <vector>
24
25 #if defined(__GLIBCXX__)
26 #include <cxxabi.h>
27 #endif
28 #if !defined(__UCLIBC__)
29 #include <execinfo.h>
30 #endif
31
32 #if defined(OS_MACOSX)
33 #include <AvailabilityMacros.h>
34 #endif
35
36 #include "base/debug/debugger.h"
37 #include "base/debug/proc_maps_linux.h"
38 #include "base/logging.h"
39 #include "base/macros.h"
40 #include "base/memory/free_deleter.h"
41 #include "base/memory/singleton.h"
42 #include "base/numerics/safe_conversions.h"
43 #include "base/posix/eintr_wrapper.h"
44 #include "base/strings/string_number_conversions.h"
45 #include "build/build_config.h"
46
47 #if defined(USE_SYMBOLIZE)
48 #error "symbolize support was removed from libchrome"
49 #endif
50
51 namespace base {
52 namespace debug {
53
54 namespace {
55
56 volatile sig_atomic_t in_signal_handler = 0;
57
58 #if !defined(USE_SYMBOLIZE) && defined(__GLIBCXX__)
59 // The prefix used for mangled symbols, per the Itanium C++ ABI:
60 // http://www.codesourcery.com/cxx-abi/abi.html#mangling
61 const char kMangledSymbolPrefix[] = "_Z";
62
63 // Characters that can be used for symbols, generated by Ruby:
64 // (('a'..'z').to_a+('A'..'Z').to_a+('0'..'9').to_a + ['_']).join
65 const char kSymbolCharacters[] =
66 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";
67 #endif // !defined(USE_SYMBOLIZE) && defined(__GLIBCXX__)
68
69 #if !defined(USE_SYMBOLIZE)
70 // Demangles C++ symbols in the given text. Example:
71 //
72 // "out/Debug/base_unittests(_ZN10StackTraceC1Ev+0x20) [0x817778c]"
73 // =>
74 // "out/Debug/base_unittests(StackTrace::StackTrace()+0x20) [0x817778c]"
75 #if defined(__GLIBCXX__) && !defined(__UCLIBC__)
DemangleSymbols(std::string * text)76 void DemangleSymbols(std::string* text) {
77 // Note: code in this function is NOT async-signal safe (std::string uses
78 // malloc internally).
79 std::string::size_type search_from = 0;
80 while (search_from < text->size()) {
81 // Look for the start of a mangled symbol, from search_from.
82 std::string::size_type mangled_start =
83 text->find(kMangledSymbolPrefix, search_from);
84 if (mangled_start == std::string::npos) {
85 break; // Mangled symbol not found.
86 }
87
88 // Look for the end of the mangled symbol.
89 std::string::size_type mangled_end =
90 text->find_first_not_of(kSymbolCharacters, mangled_start);
91 if (mangled_end == std::string::npos) {
92 mangled_end = text->size();
93 }
94 std::string mangled_symbol =
95 text->substr(mangled_start, mangled_end - mangled_start);
96
97 // Try to demangle the mangled symbol candidate.
98 int status = 0;
99 std::unique_ptr<char, base::FreeDeleter> demangled_symbol(
100 abi::__cxa_demangle(mangled_symbol.c_str(), NULL, 0, &status));
101 if (status == 0) { // Demangling is successful.
102 // Remove the mangled symbol.
103 text->erase(mangled_start, mangled_end - mangled_start);
104 // Insert the demangled symbol.
105 text->insert(mangled_start, demangled_symbol.get());
106 // Next time, we'll start right after the demangled symbol we inserted.
107 search_from = mangled_start + strlen(demangled_symbol.get());
108 } else {
109 // Failed to demangle. Retry after the "_Z" we just found.
110 search_from = mangled_start + 2;
111 }
112 }
113 }
114 #elif !defined(__UCLIBC__)
DemangleSymbols(std::string *)115 void DemangleSymbols(std::string* /* text */) {}
116 #endif // defined(__GLIBCXX__) && !defined(__UCLIBC__)
117
118 #endif // !defined(USE_SYMBOLIZE)
119
120 class BacktraceOutputHandler {
121 public:
122 virtual void HandleOutput(const char* output) = 0;
123
124 protected:
~BacktraceOutputHandler()125 virtual ~BacktraceOutputHandler() {}
126 };
127
128 #if defined(USE_SYMBOLIZE) || !defined(__UCLIBC__)
OutputPointer(void * pointer,BacktraceOutputHandler * handler)129 void OutputPointer(void* pointer, BacktraceOutputHandler* handler) {
130 // This should be more than enough to store a 64-bit number in hex:
131 // 16 hex digits + 1 for null-terminator.
132 char buf[17] = { '\0' };
133 handler->HandleOutput("0x");
134 internal::itoa_r(reinterpret_cast<intptr_t>(pointer),
135 buf, sizeof(buf), 16, 12);
136 handler->HandleOutput(buf);
137 }
138 #endif // defined(USE_SYMBOLIZE) || !defined(__UCLIBC__)
139
140 #if defined(USE_SYMBOLIZE)
OutputFrameId(intptr_t frame_id,BacktraceOutputHandler * handler)141 void OutputFrameId(intptr_t frame_id, BacktraceOutputHandler* handler) {
142 // Max unsigned 64-bit number in decimal has 20 digits (18446744073709551615).
143 // Hence, 30 digits should be more than enough to represent it in decimal
144 // (including the null-terminator).
145 char buf[30] = { '\0' };
146 handler->HandleOutput("#");
147 internal::itoa_r(frame_id, buf, sizeof(buf), 10, 1);
148 handler->HandleOutput(buf);
149 }
150 #endif // defined(USE_SYMBOLIZE)
151
152 #if !defined(__UCLIBC__)
ProcessBacktrace(void * const * trace,size_t size,BacktraceOutputHandler * handler)153 void ProcessBacktrace(void *const * trace,
154 size_t size,
155 BacktraceOutputHandler* handler) {
156 (void)trace; // unused based on build context below.
157 (void)size; // unusud based on build context below.
158 (void)handler; // unused based on build context below.
159 // NOTE: This code MUST be async-signal safe (it's used by in-process
160 // stack dumping signal handler). NO malloc or stdio is allowed here.
161
162 #if defined(USE_SYMBOLIZE)
163 for (size_t i = 0; i < size; ++i) {
164 OutputFrameId(i, handler);
165 handler->HandleOutput(" ");
166 OutputPointer(trace[i], handler);
167 handler->HandleOutput(" ");
168
169 char buf[1024] = { '\0' };
170
171 // Subtract by one as return address of function may be in the next
172 // function when a function is annotated as noreturn.
173 void* address = static_cast<char*>(trace[i]) - 1;
174 if (google::Symbolize(address, buf, sizeof(buf)))
175 handler->HandleOutput(buf);
176 else
177 handler->HandleOutput("<unknown>");
178
179 handler->HandleOutput("\n");
180 }
181 #else
182 bool printed = false;
183
184 // Below part is async-signal unsafe (uses malloc), so execute it only
185 // when we are not executing the signal handler.
186 if (in_signal_handler == 0) {
187 std::unique_ptr<char*, FreeDeleter> trace_symbols(
188 backtrace_symbols(trace, size));
189 if (trace_symbols.get()) {
190 for (size_t i = 0; i < size; ++i) {
191 std::string trace_symbol = trace_symbols.get()[i];
192 DemangleSymbols(&trace_symbol);
193 handler->HandleOutput(trace_symbol.c_str());
194 handler->HandleOutput("\n");
195 }
196
197 printed = true;
198 }
199 }
200
201 if (!printed) {
202 for (size_t i = 0; i < size; ++i) {
203 handler->HandleOutput(" [");
204 OutputPointer(trace[i], handler);
205 handler->HandleOutput("]\n");
206 }
207 }
208 #endif // defined(USE_SYMBOLIZE)
209 }
210 #endif // !defined(__UCLIBC__)
211
PrintToStderr(const char * output)212 void PrintToStderr(const char* output) {
213 // NOTE: This code MUST be async-signal safe (it's used by in-process
214 // stack dumping signal handler). NO malloc or stdio is allowed here.
215 ignore_result(HANDLE_EINTR(write(STDERR_FILENO, output, strlen(output))));
216 }
217
StackDumpSignalHandler(int signal,siginfo_t * info,void * void_context)218 void StackDumpSignalHandler(int signal, siginfo_t* info, void* void_context) {
219 (void)void_context; // unused depending on build context
220 // NOTE: This code MUST be async-signal safe.
221 // NO malloc or stdio is allowed here.
222
223 // Record the fact that we are in the signal handler now, so that the rest
224 // of StackTrace can behave in an async-signal-safe manner.
225 in_signal_handler = 1;
226
227 if (BeingDebugged())
228 BreakDebugger();
229
230 PrintToStderr("Received signal ");
231 char buf[1024] = { 0 };
232 internal::itoa_r(signal, buf, sizeof(buf), 10, 0);
233 PrintToStderr(buf);
234 if (signal == SIGBUS) {
235 if (info->si_code == BUS_ADRALN)
236 PrintToStderr(" BUS_ADRALN ");
237 else if (info->si_code == BUS_ADRERR)
238 PrintToStderr(" BUS_ADRERR ");
239 else if (info->si_code == BUS_OBJERR)
240 PrintToStderr(" BUS_OBJERR ");
241 else
242 PrintToStderr(" <unknown> ");
243 } else if (signal == SIGFPE) {
244 if (info->si_code == FPE_FLTDIV)
245 PrintToStderr(" FPE_FLTDIV ");
246 else if (info->si_code == FPE_FLTINV)
247 PrintToStderr(" FPE_FLTINV ");
248 else if (info->si_code == FPE_FLTOVF)
249 PrintToStderr(" FPE_FLTOVF ");
250 else if (info->si_code == FPE_FLTRES)
251 PrintToStderr(" FPE_FLTRES ");
252 else if (info->si_code == FPE_FLTSUB)
253 PrintToStderr(" FPE_FLTSUB ");
254 else if (info->si_code == FPE_FLTUND)
255 PrintToStderr(" FPE_FLTUND ");
256 else if (info->si_code == FPE_INTDIV)
257 PrintToStderr(" FPE_INTDIV ");
258 else if (info->si_code == FPE_INTOVF)
259 PrintToStderr(" FPE_INTOVF ");
260 else
261 PrintToStderr(" <unknown> ");
262 } else if (signal == SIGILL) {
263 if (info->si_code == ILL_BADSTK)
264 PrintToStderr(" ILL_BADSTK ");
265 else if (info->si_code == ILL_COPROC)
266 PrintToStderr(" ILL_COPROC ");
267 else if (info->si_code == ILL_ILLOPN)
268 PrintToStderr(" ILL_ILLOPN ");
269 else if (info->si_code == ILL_ILLADR)
270 PrintToStderr(" ILL_ILLADR ");
271 else if (info->si_code == ILL_ILLTRP)
272 PrintToStderr(" ILL_ILLTRP ");
273 else if (info->si_code == ILL_PRVOPC)
274 PrintToStderr(" ILL_PRVOPC ");
275 else if (info->si_code == ILL_PRVREG)
276 PrintToStderr(" ILL_PRVREG ");
277 else
278 PrintToStderr(" <unknown> ");
279 } else if (signal == SIGSEGV) {
280 if (info->si_code == SEGV_MAPERR)
281 PrintToStderr(" SEGV_MAPERR ");
282 else if (info->si_code == SEGV_ACCERR)
283 PrintToStderr(" SEGV_ACCERR ");
284 else
285 PrintToStderr(" <unknown> ");
286 }
287 if (signal == SIGBUS || signal == SIGFPE ||
288 signal == SIGILL || signal == SIGSEGV) {
289 internal::itoa_r(reinterpret_cast<intptr_t>(info->si_addr),
290 buf, sizeof(buf), 16, 12);
291 PrintToStderr(buf);
292 }
293 PrintToStderr("\n");
294
295 #if defined(CFI_ENFORCEMENT)
296 if (signal == SIGILL && info->si_code == ILL_ILLOPN) {
297 PrintToStderr(
298 "CFI: Most likely a control flow integrity violation; for more "
299 "information see:\n");
300 PrintToStderr(
301 "https://www.chromium.org/developers/testing/control-flow-integrity\n");
302 }
303 #endif
304
305 debug::StackTrace().Print();
306
307 #if defined(OS_LINUX)
308 #if ARCH_CPU_X86_FAMILY
309 ucontext_t* context = reinterpret_cast<ucontext_t*>(void_context);
310 const struct {
311 const char* label;
312 greg_t value;
313 } registers[] = {
314 #if ARCH_CPU_32_BITS
315 { " gs: ", context->uc_mcontext.gregs[REG_GS] },
316 { " fs: ", context->uc_mcontext.gregs[REG_FS] },
317 { " es: ", context->uc_mcontext.gregs[REG_ES] },
318 { " ds: ", context->uc_mcontext.gregs[REG_DS] },
319 { " edi: ", context->uc_mcontext.gregs[REG_EDI] },
320 { " esi: ", context->uc_mcontext.gregs[REG_ESI] },
321 { " ebp: ", context->uc_mcontext.gregs[REG_EBP] },
322 { " esp: ", context->uc_mcontext.gregs[REG_ESP] },
323 { " ebx: ", context->uc_mcontext.gregs[REG_EBX] },
324 { " edx: ", context->uc_mcontext.gregs[REG_EDX] },
325 { " ecx: ", context->uc_mcontext.gregs[REG_ECX] },
326 { " eax: ", context->uc_mcontext.gregs[REG_EAX] },
327 { " trp: ", context->uc_mcontext.gregs[REG_TRAPNO] },
328 { " err: ", context->uc_mcontext.gregs[REG_ERR] },
329 { " ip: ", context->uc_mcontext.gregs[REG_EIP] },
330 { " cs: ", context->uc_mcontext.gregs[REG_CS] },
331 { " efl: ", context->uc_mcontext.gregs[REG_EFL] },
332 { " usp: ", context->uc_mcontext.gregs[REG_UESP] },
333 { " ss: ", context->uc_mcontext.gregs[REG_SS] },
334 #elif ARCH_CPU_64_BITS
335 { " r8: ", context->uc_mcontext.gregs[REG_R8] },
336 { " r9: ", context->uc_mcontext.gregs[REG_R9] },
337 { " r10: ", context->uc_mcontext.gregs[REG_R10] },
338 { " r11: ", context->uc_mcontext.gregs[REG_R11] },
339 { " r12: ", context->uc_mcontext.gregs[REG_R12] },
340 { " r13: ", context->uc_mcontext.gregs[REG_R13] },
341 { " r14: ", context->uc_mcontext.gregs[REG_R14] },
342 { " r15: ", context->uc_mcontext.gregs[REG_R15] },
343 { " di: ", context->uc_mcontext.gregs[REG_RDI] },
344 { " si: ", context->uc_mcontext.gregs[REG_RSI] },
345 { " bp: ", context->uc_mcontext.gregs[REG_RBP] },
346 { " bx: ", context->uc_mcontext.gregs[REG_RBX] },
347 { " dx: ", context->uc_mcontext.gregs[REG_RDX] },
348 { " ax: ", context->uc_mcontext.gregs[REG_RAX] },
349 { " cx: ", context->uc_mcontext.gregs[REG_RCX] },
350 { " sp: ", context->uc_mcontext.gregs[REG_RSP] },
351 { " ip: ", context->uc_mcontext.gregs[REG_RIP] },
352 { " efl: ", context->uc_mcontext.gregs[REG_EFL] },
353 { " cgf: ", context->uc_mcontext.gregs[REG_CSGSFS] },
354 { " erf: ", context->uc_mcontext.gregs[REG_ERR] },
355 { " trp: ", context->uc_mcontext.gregs[REG_TRAPNO] },
356 { " msk: ", context->uc_mcontext.gregs[REG_OLDMASK] },
357 { " cr2: ", context->uc_mcontext.gregs[REG_CR2] },
358 #endif // ARCH_CPU_32_BITS
359 };
360
361 #if ARCH_CPU_32_BITS
362 const int kRegisterPadding = 8;
363 #elif ARCH_CPU_64_BITS
364 const int kRegisterPadding = 16;
365 #endif
366
367 for (size_t i = 0; i < arraysize(registers); i++) {
368 PrintToStderr(registers[i].label);
369 internal::itoa_r(registers[i].value, buf, sizeof(buf),
370 16, kRegisterPadding);
371 PrintToStderr(buf);
372
373 if ((i + 1) % 4 == 0)
374 PrintToStderr("\n");
375 }
376 PrintToStderr("\n");
377 #endif // ARCH_CPU_X86_FAMILY
378 #endif // defined(OS_LINUX)
379
380 PrintToStderr("[end of stack trace]\n");
381
382 #if defined(OS_MACOSX) && !defined(OS_IOS)
383 if (::signal(signal, SIG_DFL) == SIG_ERR)
384 _exit(1);
385 #else
386 // Non-Mac OSes should probably reraise the signal as well, but the Linux
387 // sandbox tests break on CrOS devices.
388 // https://code.google.com/p/chromium/issues/detail?id=551681
389 _exit(1);
390 #endif // defined(OS_MACOSX) && !defined(OS_IOS)
391 }
392
393 class PrintBacktraceOutputHandler : public BacktraceOutputHandler {
394 public:
PrintBacktraceOutputHandler()395 PrintBacktraceOutputHandler() {}
396
HandleOutput(const char * output)397 void HandleOutput(const char* output) override {
398 // NOTE: This code MUST be async-signal safe (it's used by in-process
399 // stack dumping signal handler). NO malloc or stdio is allowed here.
400 PrintToStderr(output);
401 }
402
403 private:
404 DISALLOW_COPY_AND_ASSIGN(PrintBacktraceOutputHandler);
405 };
406
407 class StreamBacktraceOutputHandler : public BacktraceOutputHandler {
408 public:
StreamBacktraceOutputHandler(std::ostream * os)409 explicit StreamBacktraceOutputHandler(std::ostream* os) : os_(os) {
410 }
411
HandleOutput(const char * output)412 void HandleOutput(const char* output) override { (*os_) << output; }
413
414 private:
415 std::ostream* os_;
416
417 DISALLOW_COPY_AND_ASSIGN(StreamBacktraceOutputHandler);
418 };
419
WarmUpBacktrace()420 void WarmUpBacktrace() {
421 // Warm up stack trace infrastructure. It turns out that on the first
422 // call glibc initializes some internal data structures using pthread_once,
423 // and even backtrace() can call malloc(), leading to hangs.
424 //
425 // Example stack trace snippet (with tcmalloc):
426 //
427 // #8 0x0000000000a173b5 in tc_malloc
428 // at ./third_party/tcmalloc/chromium/src/debugallocation.cc:1161
429 // #9 0x00007ffff7de7900 in _dl_map_object_deps at dl-deps.c:517
430 // #10 0x00007ffff7ded8a9 in dl_open_worker at dl-open.c:262
431 // #11 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
432 // #12 0x00007ffff7ded31a in _dl_open (file=0x7ffff625e298 "libgcc_s.so.1")
433 // at dl-open.c:639
434 // #13 0x00007ffff6215602 in do_dlopen at dl-libc.c:89
435 // #14 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
436 // #15 0x00007ffff62156c4 in dlerror_run at dl-libc.c:48
437 // #16 __GI___libc_dlopen_mode at dl-libc.c:165
438 // #17 0x00007ffff61ef8f5 in init
439 // at ../sysdeps/x86_64/../ia64/backtrace.c:53
440 // #18 0x00007ffff6aad400 in pthread_once
441 // at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_once.S:104
442 // #19 0x00007ffff61efa14 in __GI___backtrace
443 // at ../sysdeps/x86_64/../ia64/backtrace.c:104
444 // #20 0x0000000000752a54 in base::debug::StackTrace::StackTrace
445 // at base/debug/stack_trace_posix.cc:175
446 // #21 0x00000000007a4ae5 in
447 // base::(anonymous namespace)::StackDumpSignalHandler
448 // at base/process_util_posix.cc:172
449 // #22 <signal handler called>
450 StackTrace stack_trace;
451 }
452
453 } // namespace
454
455 #if defined(USE_SYMBOLIZE)
456
457 // class SandboxSymbolizeHelper.
458 //
459 // The purpose of this class is to prepare and install a "file open" callback
460 // needed by the stack trace symbolization code
461 // (base/third_party/symbolize/symbolize.h) so that it can function properly
462 // in a sandboxed process. The caveat is that this class must be instantiated
463 // before the sandboxing is enabled so that it can get the chance to open all
464 // the object files that are loaded in the virtual address space of the current
465 // process.
466 class SandboxSymbolizeHelper {
467 public:
468 // Returns the singleton instance.
GetInstance()469 static SandboxSymbolizeHelper* GetInstance() {
470 return Singleton<SandboxSymbolizeHelper>::get();
471 }
472
473 private:
474 friend struct DefaultSingletonTraits<SandboxSymbolizeHelper>;
475
SandboxSymbolizeHelper()476 SandboxSymbolizeHelper()
477 : is_initialized_(false) {
478 Init();
479 }
480
~SandboxSymbolizeHelper()481 ~SandboxSymbolizeHelper() {
482 UnregisterCallback();
483 CloseObjectFiles();
484 }
485
486 // Returns a O_RDONLY file descriptor for |file_path| if it was opened
487 // successfully during the initialization. The file is repositioned at
488 // offset 0.
489 // IMPORTANT: This function must be async-signal-safe because it can be
490 // called from a signal handler (symbolizing stack frames for a crash).
GetFileDescriptor(const char * file_path)491 int GetFileDescriptor(const char* file_path) {
492 int fd = -1;
493
494 #if !defined(OFFICIAL_BUILD)
495 if (file_path) {
496 // The assumption here is that iterating over std::map<std::string, int>
497 // using a const_iterator does not allocate dynamic memory, hense it is
498 // async-signal-safe.
499 std::map<std::string, int>::const_iterator it;
500 for (it = modules_.begin(); it != modules_.end(); ++it) {
501 if (strcmp((it->first).c_str(), file_path) == 0) {
502 // POSIX.1-2004 requires an implementation to guarantee that dup()
503 // is async-signal-safe.
504 fd = dup(it->second);
505 break;
506 }
507 }
508 // POSIX.1-2004 requires an implementation to guarantee that lseek()
509 // is async-signal-safe.
510 if (fd >= 0 && lseek(fd, 0, SEEK_SET) < 0) {
511 // Failed to seek.
512 fd = -1;
513 }
514 }
515 #endif // !defined(OFFICIAL_BUILD)
516
517 return fd;
518 }
519
520 // Searches for the object file (from /proc/self/maps) that contains
521 // the specified pc. If found, sets |start_address| to the start address
522 // of where this object file is mapped in memory, sets the module base
523 // address into |base_address|, copies the object file name into
524 // |out_file_name|, and attempts to open the object file. If the object
525 // file is opened successfully, returns the file descriptor. Otherwise,
526 // returns -1. |out_file_name_size| is the size of the file name buffer
527 // (including the null terminator).
528 // IMPORTANT: This function must be async-signal-safe because it can be
529 // called from a signal handler (symbolizing stack frames for a crash).
OpenObjectFileContainingPc(uint64_t pc,uint64_t & start_address,uint64_t & base_address,char * file_path,int file_path_size)530 static int OpenObjectFileContainingPc(uint64_t pc, uint64_t& start_address,
531 uint64_t& base_address, char* file_path,
532 int file_path_size) {
533 // This method can only be called after the singleton is instantiated.
534 // This is ensured by the following facts:
535 // * This is the only static method in this class, it is private, and
536 // the class has no friends (except for the DefaultSingletonTraits).
537 // The compiler guarantees that it can only be called after the
538 // singleton is instantiated.
539 // * This method is used as a callback for the stack tracing code and
540 // the callback registration is done in the constructor, so logically
541 // it cannot be called before the singleton is created.
542 SandboxSymbolizeHelper* instance = GetInstance();
543
544 // The assumption here is that iterating over
545 // std::vector<MappedMemoryRegion> using a const_iterator does not allocate
546 // dynamic memory, hence it is async-signal-safe.
547 std::vector<MappedMemoryRegion>::const_iterator it;
548 bool is_first = true;
549 for (it = instance->regions_.begin(); it != instance->regions_.end();
550 ++it, is_first = false) {
551 const MappedMemoryRegion& region = *it;
552 if (region.start <= pc && pc < region.end) {
553 start_address = region.start;
554 // Don't subtract 'start_address' from the first entry:
555 // * If a binary is compiled w/o -pie, then the first entry in
556 // process maps is likely the binary itself (all dynamic libs
557 // are mapped higher in address space). For such a binary,
558 // instruction offset in binary coincides with the actual
559 // instruction address in virtual memory (as code section
560 // is mapped to a fixed memory range).
561 // * If a binary is compiled with -pie, all the modules are
562 // mapped high at address space (in particular, higher than
563 // shadow memory of the tool), so the module can't be the
564 // first entry.
565 base_address = (is_first ? 0U : start_address) - region.offset;
566 if (file_path && file_path_size > 0) {
567 strncpy(file_path, region.path.c_str(), file_path_size);
568 // Ensure null termination.
569 file_path[file_path_size - 1] = '\0';
570 }
571 return instance->GetFileDescriptor(region.path.c_str());
572 }
573 }
574 return -1;
575 }
576
577 // Parses /proc/self/maps in order to compile a list of all object file names
578 // for the modules that are loaded in the current process.
579 // Returns true on success.
CacheMemoryRegions()580 bool CacheMemoryRegions() {
581 // Reads /proc/self/maps.
582 std::string contents;
583 if (!ReadProcMaps(&contents)) {
584 LOG(ERROR) << "Failed to read /proc/self/maps";
585 return false;
586 }
587
588 // Parses /proc/self/maps.
589 if (!ParseProcMaps(contents, ®ions_)) {
590 LOG(ERROR) << "Failed to parse the contents of /proc/self/maps";
591 return false;
592 }
593
594 is_initialized_ = true;
595 return true;
596 }
597
598 // Opens all object files and caches their file descriptors.
OpenSymbolFiles()599 void OpenSymbolFiles() {
600 // Pre-opening and caching the file descriptors of all loaded modules is
601 // not safe for production builds. Hence it is only done in non-official
602 // builds. For more details, take a look at: http://crbug.com/341966.
603 #if !defined(OFFICIAL_BUILD)
604 // Open the object files for all read-only executable regions and cache
605 // their file descriptors.
606 std::vector<MappedMemoryRegion>::const_iterator it;
607 for (it = regions_.begin(); it != regions_.end(); ++it) {
608 const MappedMemoryRegion& region = *it;
609 // Only interesed in read-only executable regions.
610 if ((region.permissions & MappedMemoryRegion::READ) ==
611 MappedMemoryRegion::READ &&
612 (region.permissions & MappedMemoryRegion::WRITE) == 0 &&
613 (region.permissions & MappedMemoryRegion::EXECUTE) ==
614 MappedMemoryRegion::EXECUTE) {
615 if (region.path.empty()) {
616 // Skip regions with empty file names.
617 continue;
618 }
619 if (region.path[0] == '[') {
620 // Skip pseudo-paths, like [stack], [vdso], [heap], etc ...
621 continue;
622 }
623 // Avoid duplicates.
624 if (modules_.find(region.path) == modules_.end()) {
625 int fd = open(region.path.c_str(), O_RDONLY | O_CLOEXEC);
626 if (fd >= 0) {
627 modules_.insert(std::make_pair(region.path, fd));
628 } else {
629 LOG(WARNING) << "Failed to open file: " << region.path
630 << "\n Error: " << strerror(errno);
631 }
632 }
633 }
634 }
635 #endif // !defined(OFFICIAL_BUILD)
636 }
637
638 // Initializes and installs the symbolization callback.
Init()639 void Init() {
640 if (CacheMemoryRegions()) {
641 OpenSymbolFiles();
642 google::InstallSymbolizeOpenObjectFileCallback(
643 &OpenObjectFileContainingPc);
644 }
645 }
646
647 // Unregister symbolization callback.
UnregisterCallback()648 void UnregisterCallback() {
649 if (is_initialized_) {
650 google::InstallSymbolizeOpenObjectFileCallback(NULL);
651 is_initialized_ = false;
652 }
653 }
654
655 // Closes all file descriptors owned by this instance.
CloseObjectFiles()656 void CloseObjectFiles() {
657 #if !defined(OFFICIAL_BUILD)
658 std::map<std::string, int>::iterator it;
659 for (it = modules_.begin(); it != modules_.end(); ++it) {
660 int ret = IGNORE_EINTR(close(it->second));
661 DCHECK(!ret);
662 it->second = -1;
663 }
664 modules_.clear();
665 #endif // !defined(OFFICIAL_BUILD)
666 }
667
668 // Set to true upon successful initialization.
669 bool is_initialized_;
670
671 #if !defined(OFFICIAL_BUILD)
672 // Mapping from file name to file descriptor. Includes file descriptors
673 // for all successfully opened object files and the file descriptor for
674 // /proc/self/maps. This code is not safe for production builds.
675 std::map<std::string, int> modules_;
676 #endif // !defined(OFFICIAL_BUILD)
677
678 // Cache for the process memory regions. Produced by parsing the contents
679 // of /proc/self/maps cache.
680 std::vector<MappedMemoryRegion> regions_;
681
682 DISALLOW_COPY_AND_ASSIGN(SandboxSymbolizeHelper);
683 };
684 #endif // USE_SYMBOLIZE
685
EnableInProcessStackDumping()686 bool EnableInProcessStackDumping() {
687 #if defined(USE_SYMBOLIZE)
688 SandboxSymbolizeHelper::GetInstance();
689 #endif // USE_SYMBOLIZE
690
691 // When running in an application, our code typically expects SIGPIPE
692 // to be ignored. Therefore, when testing that same code, it should run
693 // with SIGPIPE ignored as well.
694 struct sigaction sigpipe_action;
695 memset(&sigpipe_action, 0, sizeof(sigpipe_action));
696 sigpipe_action.sa_handler = SIG_IGN;
697 sigemptyset(&sigpipe_action.sa_mask);
698 bool success = (sigaction(SIGPIPE, &sigpipe_action, NULL) == 0);
699
700 // Avoid hangs during backtrace initialization, see above.
701 WarmUpBacktrace();
702
703 struct sigaction action;
704 memset(&action, 0, sizeof(action));
705 action.sa_flags = SA_RESETHAND | SA_SIGINFO;
706 action.sa_sigaction = &StackDumpSignalHandler;
707 sigemptyset(&action.sa_mask);
708
709 success &= (sigaction(SIGILL, &action, NULL) == 0);
710 success &= (sigaction(SIGABRT, &action, NULL) == 0);
711 success &= (sigaction(SIGFPE, &action, NULL) == 0);
712 success &= (sigaction(SIGBUS, &action, NULL) == 0);
713 success &= (sigaction(SIGSEGV, &action, NULL) == 0);
714 // On Linux, SIGSYS is reserved by the kernel for seccomp-bpf sandboxing.
715 #if !defined(OS_LINUX)
716 success &= (sigaction(SIGSYS, &action, NULL) == 0);
717 #endif // !defined(OS_LINUX)
718
719 return success;
720 }
721
StackTrace()722 StackTrace::StackTrace() {
723 // NOTE: This code MUST be async-signal safe (it's used by in-process
724 // stack dumping signal handler). NO malloc or stdio is allowed here.
725
726 #if !defined(__UCLIBC__)
727 // Though the backtrace API man page does not list any possible negative
728 // return values, we take no chance.
729 count_ = base::saturated_cast<size_t>(backtrace(trace_, arraysize(trace_)));
730 #else
731 count_ = 0;
732 #endif
733 }
734
Print() const735 void StackTrace::Print() const {
736 // NOTE: This code MUST be async-signal safe (it's used by in-process
737 // stack dumping signal handler). NO malloc or stdio is allowed here.
738
739 #if !defined(__UCLIBC__)
740 PrintBacktraceOutputHandler handler;
741 ProcessBacktrace(trace_, count_, &handler);
742 #endif
743 }
744
745 #if !defined(__UCLIBC__)
OutputToStream(std::ostream * os) const746 void StackTrace::OutputToStream(std::ostream* os) const {
747 StreamBacktraceOutputHandler handler(os);
748 ProcessBacktrace(trace_, count_, &handler);
749 }
750 #endif
751
752 namespace internal {
753
754 // NOTE: code from sandbox/linux/seccomp-bpf/demo.cc.
itoa_r(intptr_t i,char * buf,size_t sz,int base,size_t padding)755 char* itoa_r(intptr_t i, char* buf, size_t sz, int base, size_t padding) {
756 // Make sure we can write at least one NUL byte.
757 size_t n = 1;
758 if (n > sz)
759 return NULL;
760
761 if (base < 2 || base > 16) {
762 buf[0] = '\000';
763 return NULL;
764 }
765
766 char* start = buf;
767
768 uintptr_t j = i;
769
770 // Handle negative numbers (only for base 10).
771 if (i < 0 && base == 10) {
772 // This does "j = -i" while avoiding integer overflow.
773 j = static_cast<uintptr_t>(-(i + 1)) + 1;
774
775 // Make sure we can write the '-' character.
776 if (++n > sz) {
777 buf[0] = '\000';
778 return NULL;
779 }
780 *start++ = '-';
781 }
782
783 // Loop until we have converted the entire number. Output at least one
784 // character (i.e. '0').
785 char* ptr = start;
786 do {
787 // Make sure there is still enough space left in our output buffer.
788 if (++n > sz) {
789 buf[0] = '\000';
790 return NULL;
791 }
792
793 // Output the next digit.
794 *ptr++ = "0123456789abcdef"[j % base];
795 j /= base;
796
797 if (padding > 0)
798 padding--;
799 } while (j > 0 || padding > 0);
800
801 // Terminate the output with a NUL character.
802 *ptr = '\000';
803
804 // Conversion to ASCII actually resulted in the digits being in reverse
805 // order. We can't easily generate them in forward order, as we can't tell
806 // the number of characters needed until we are done converting.
807 // So, now, we reverse the string (except for the possible "-" sign).
808 while (--ptr > start) {
809 char ch = *ptr;
810 *ptr = *start;
811 *start++ = ch;
812 }
813 return buf;
814 }
815
816 } // namespace internal
817
818 } // namespace debug
819 } // namespace base
820