1 // Copyright (c) 2012, Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 // * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 // * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
14 // * Neither the name of Google Inc. nor the names of its
15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30 // linux_ptrace_dumper.cc: Implement google_breakpad::LinuxPtraceDumper.
31 // See linux_ptrace_dumper.h for detals.
32 // This class was originally splitted from google_breakpad::LinuxDumper.
33
34 // This code deals with the mechanics of getting information about a crashed
35 // process. Since this code may run in a compromised address space, the same
36 // rules apply as detailed at the top of minidump_writer.h: no libc calls and
37 // use the alternative allocator.
38
39 #include "client/linux/minidump_writer/linux_ptrace_dumper.h"
40
41 #include <asm/ptrace.h>
42 #include <assert.h>
43 #include <errno.h>
44 #include <fcntl.h>
45 #include <limits.h>
46 #include <stddef.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <sys/ptrace.h>
50 #include <sys/uio.h>
51 #include <sys/wait.h>
52
53 #if defined(__i386)
54 #include <cpuid.h>
55 #endif
56
57 #include "client/linux/minidump_writer/directory_reader.h"
58 #include "client/linux/minidump_writer/line_reader.h"
59 #include "common/linux/linux_libc_support.h"
60 #include "third_party/lss/linux_syscall_support.h"
61
62 // Suspends a thread by attaching to it.
SuspendThread(pid_t pid)63 static bool SuspendThread(pid_t pid) {
64 // This may fail if the thread has just died or debugged.
65 errno = 0;
66 if (sys_ptrace(PTRACE_ATTACH, pid, NULL, NULL) != 0 &&
67 errno != 0) {
68 return false;
69 }
70 while (sys_waitpid(pid, NULL, __WALL) < 0) {
71 if (errno != EINTR) {
72 sys_ptrace(PTRACE_DETACH, pid, NULL, NULL);
73 return false;
74 }
75 }
76 #if defined(__i386) || defined(__x86_64)
77 // On x86, the stack pointer is NULL or -1, when executing trusted code in
78 // the seccomp sandbox. Not only does this cause difficulties down the line
79 // when trying to dump the thread's stack, it also results in the minidumps
80 // containing information about the trusted threads. This information is
81 // generally completely meaningless and just pollutes the minidumps.
82 // We thus test the stack pointer and exclude any threads that are part of
83 // the seccomp sandbox's trusted code.
84 user_regs_struct regs;
85 if (sys_ptrace(PTRACE_GETREGS, pid, NULL, ®s) == -1 ||
86 #if defined(__i386)
87 !regs.esp
88 #elif defined(__x86_64)
89 !regs.rsp
90 #endif
91 ) {
92 sys_ptrace(PTRACE_DETACH, pid, NULL, NULL);
93 return false;
94 }
95 #endif
96 return true;
97 }
98
99 // Resumes a thread by detaching from it.
ResumeThread(pid_t pid)100 static bool ResumeThread(pid_t pid) {
101 return sys_ptrace(PTRACE_DETACH, pid, NULL, NULL) >= 0;
102 }
103
104 namespace google_breakpad {
105
LinuxPtraceDumper(pid_t pid)106 LinuxPtraceDumper::LinuxPtraceDumper(pid_t pid)
107 : LinuxDumper(pid),
108 threads_suspended_(false) {
109 }
110
BuildProcPath(char * path,pid_t pid,const char * node) const111 bool LinuxPtraceDumper::BuildProcPath(char* path, pid_t pid,
112 const char* node) const {
113 if (!path || !node || pid <= 0)
114 return false;
115
116 size_t node_len = my_strlen(node);
117 if (node_len == 0)
118 return false;
119
120 const unsigned pid_len = my_uint_len(pid);
121 const size_t total_length = 6 + pid_len + 1 + node_len;
122 if (total_length >= NAME_MAX)
123 return false;
124
125 my_memcpy(path, "/proc/", 6);
126 my_uitos(path + 6, pid, pid_len);
127 path[6 + pid_len] = '/';
128 my_memcpy(path + 6 + pid_len + 1, node, node_len);
129 path[total_length] = '\0';
130 return true;
131 }
132
CopyFromProcess(void * dest,pid_t child,const void * src,size_t length)133 bool LinuxPtraceDumper::CopyFromProcess(void* dest, pid_t child,
134 const void* src, size_t length) {
135 unsigned long tmp = 55;
136 size_t done = 0;
137 static const size_t word_size = sizeof(tmp);
138 uint8_t* const local = (uint8_t*) dest;
139 uint8_t* const remote = (uint8_t*) src;
140
141 while (done < length) {
142 const size_t l = (length - done > word_size) ? word_size : (length - done);
143 if (sys_ptrace(PTRACE_PEEKDATA, child, remote + done, &tmp) == -1) {
144 tmp = 0;
145 }
146 my_memcpy(local + done, &tmp, l);
147 done += l;
148 }
149 return true;
150 }
151
152 // Read thread info from /proc/$pid/status.
153 // Fill out the |tgid|, |ppid| and |pid| members of |info|. If unavailable,
154 // these members are set to -1. Returns true iff all three members are
155 // available.
GetThreadInfoByIndex(size_t index,ThreadInfo * info)156 bool LinuxPtraceDumper::GetThreadInfoByIndex(size_t index, ThreadInfo* info) {
157 if (index >= threads_.size())
158 return false;
159
160 pid_t tid = threads_[index];
161
162 assert(info != NULL);
163 char status_path[NAME_MAX];
164 if (!BuildProcPath(status_path, tid, "status"))
165 return false;
166
167 const int fd = sys_open(status_path, O_RDONLY, 0);
168 if (fd < 0)
169 return false;
170
171 LineReader* const line_reader = new(allocator_) LineReader(fd);
172 const char* line;
173 unsigned line_len;
174
175 info->ppid = info->tgid = -1;
176
177 while (line_reader->GetNextLine(&line, &line_len)) {
178 if (my_strncmp("Tgid:\t", line, 6) == 0) {
179 my_strtoui(&info->tgid, line + 6);
180 } else if (my_strncmp("PPid:\t", line, 6) == 0) {
181 my_strtoui(&info->ppid, line + 6);
182 }
183
184 line_reader->PopLine(line_len);
185 }
186 sys_close(fd);
187
188 if (info->ppid == -1 || info->tgid == -1)
189 return false;
190
191 #ifdef PTRACE_GETREGSET
192 struct iovec io;
193 io.iov_base = &info->regs;
194 io.iov_len = sizeof(info->regs);
195 if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_PRSTATUS, (void*)&io) == -1) {
196 return false;
197 }
198
199 io.iov_base = &info->fpregs;
200 io.iov_len = sizeof(info->fpregs);
201 if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_FPREGSET, (void*)&io) == -1) {
202 return false;
203 }
204 #else
205 if (sys_ptrace(PTRACE_GETREGS, tid, NULL, &info->regs) == -1) {
206 return false;
207 }
208
209 if (sys_ptrace(PTRACE_GETFPREGS, tid, NULL, &info->fpregs) == -1) {
210 return false;
211 }
212 #endif
213
214 #if defined(__i386)
215 #if !defined(bit_FXSAVE) // e.g. Clang
216 #define bit_FXSAVE bit_FXSR
217 #endif
218 // Detect if the CPU supports the FXSAVE/FXRSTOR instructions
219 int eax, ebx, ecx, edx;
220 __cpuid(1, eax, ebx, ecx, edx);
221 if (edx & bit_FXSAVE) {
222 if (sys_ptrace(PTRACE_GETFPXREGS, tid, NULL, &info->fpxregs) == -1) {
223 return false;
224 }
225 } else {
226 memset(&info->fpxregs, 0, sizeof(info->fpxregs));
227 }
228 #endif // defined(__i386)
229
230 #if defined(__i386) || defined(__x86_64)
231 for (unsigned i = 0; i < ThreadInfo::kNumDebugRegisters; ++i) {
232 if (sys_ptrace(
233 PTRACE_PEEKUSER, tid,
234 reinterpret_cast<void*> (offsetof(struct user,
235 u_debugreg[0]) + i *
236 sizeof(debugreg_t)),
237 &info->dregs[i]) == -1) {
238 return false;
239 }
240 }
241 #endif
242
243 #if defined(__mips__)
244 for (int i = 0; i < 3; ++i) {
245 sys_ptrace(PTRACE_PEEKUSER, tid,
246 reinterpret_cast<void*>(DSP_BASE + (i * 2)), &info->hi[i]);
247 sys_ptrace(PTRACE_PEEKUSER, tid,
248 reinterpret_cast<void*>(DSP_BASE + (i * 2) + 1), &info->lo[i]);
249 }
250 sys_ptrace(PTRACE_PEEKUSER, tid,
251 reinterpret_cast<void*>(DSP_CONTROL), &info->dsp_control);
252 #endif
253
254 const uint8_t* stack_pointer;
255 #if defined(__i386)
256 my_memcpy(&stack_pointer, &info->regs.esp, sizeof(info->regs.esp));
257 #elif defined(__x86_64)
258 my_memcpy(&stack_pointer, &info->regs.rsp, sizeof(info->regs.rsp));
259 #elif defined(__ARM_EABI__)
260 my_memcpy(&stack_pointer, &info->regs.ARM_sp, sizeof(info->regs.ARM_sp));
261 #elif defined(__aarch64__)
262 my_memcpy(&stack_pointer, &info->regs.sp, sizeof(info->regs.sp));
263 #elif defined(__mips__)
264 stack_pointer =
265 reinterpret_cast<uint8_t*>(info->regs.regs[MD_CONTEXT_MIPS_REG_SP]);
266 #else
267 #error "This code hasn't been ported to your platform yet."
268 #endif
269 info->stack_pointer = reinterpret_cast<uintptr_t>(stack_pointer);
270
271 return true;
272 }
273
IsPostMortem() const274 bool LinuxPtraceDumper::IsPostMortem() const {
275 return false;
276 }
277
ThreadsSuspend()278 bool LinuxPtraceDumper::ThreadsSuspend() {
279 if (threads_suspended_)
280 return true;
281 for (size_t i = 0; i < threads_.size(); ++i) {
282 if (!SuspendThread(threads_[i])) {
283 // If the thread either disappeared before we could attach to it, or if
284 // it was part of the seccomp sandbox's trusted code, it is OK to
285 // silently drop it from the minidump.
286 if (i < threads_.size() - 1) {
287 my_memmove(&threads_[i], &threads_[i + 1],
288 (threads_.size() - i - 1) * sizeof(threads_[i]));
289 }
290 threads_.resize(threads_.size() - 1);
291 --i;
292 }
293 }
294 threads_suspended_ = true;
295 return threads_.size() > 0;
296 }
297
ThreadsResume()298 bool LinuxPtraceDumper::ThreadsResume() {
299 if (!threads_suspended_)
300 return false;
301 bool good = true;
302 for (size_t i = 0; i < threads_.size(); ++i)
303 good &= ResumeThread(threads_[i]);
304 threads_suspended_ = false;
305 return good;
306 }
307
308 // Parse /proc/$pid/task to list all the threads of the process identified by
309 // pid.
EnumerateThreads()310 bool LinuxPtraceDumper::EnumerateThreads() {
311 char task_path[NAME_MAX];
312 if (!BuildProcPath(task_path, pid_, "task"))
313 return false;
314
315 const int fd = sys_open(task_path, O_RDONLY | O_DIRECTORY, 0);
316 if (fd < 0)
317 return false;
318 DirectoryReader* dir_reader = new(allocator_) DirectoryReader(fd);
319
320 // The directory may contain duplicate entries which we filter by assuming
321 // that they are consecutive.
322 int last_tid = -1;
323 const char* dent_name;
324 while (dir_reader->GetNextEntry(&dent_name)) {
325 if (my_strcmp(dent_name, ".") &&
326 my_strcmp(dent_name, "..")) {
327 int tid = 0;
328 if (my_strtoui(&tid, dent_name) &&
329 last_tid != tid) {
330 last_tid = tid;
331 threads_.push_back(tid);
332 }
333 }
334 dir_reader->PopEntry();
335 }
336
337 sys_close(fd);
338 return true;
339 }
340
341 } // namespace google_breakpad
342