asan_stack.cc revision 4e21c6bc78bdc36736cd61639a160ea5f725b333 
1//===-- asan_stack.cc -----------------------------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file is a part of AddressSanitizer, an address sanity checker.
11//
12// Code for ASan stack trace.
13//===----------------------------------------------------------------------===//
14#include "asan_interceptors.h"
15#include "asan_lock.h"
16#include "asan_stack.h"
17#include "asan_thread.h"
18#include "asan_thread_registry.h"
19#include "sanitizer_common/sanitizer_procmaps.h"
20#include "sanitizer_common/sanitizer_symbolizer.h"
21
22#ifdef ASAN_USE_EXTERNAL_SYMBOLIZER
23extern bool
24ASAN_USE_EXTERNAL_SYMBOLIZER(const void *pc, char *out, int out_size);
25#endif
26
27namespace __asan {
28
29static const char *StripPathPrefix(const char *filepath) {
30  const char *path_prefix = flags()->strip_path_prefix;
31  if (filepath == internal_strstr(filepath, path_prefix))
32    return filepath + internal_strlen(path_prefix);
33  return filepath;
34}
35
36// ----------------------- AsanStackTrace ----------------------------- {{{1
37// PCs in stack traces are actually the return addresses, that is,
38// addresses of the next instructions after the call. That's why we
39// decrement them.
40static uptr patch_pc(uptr pc) {
41#ifdef __arm__
42  // Cancel Thumb bit.
43  pc = pc & (~1);
44#endif
45  return pc - 1;
46}
47
48#if defined(ASAN_USE_EXTERNAL_SYMBOLIZER)
49void AsanStackTrace::PrintStack(uptr *addr, uptr size) {
50  for (uptr i = 0; i < size && addr[i]; i++) {
51    uptr pc = addr[i];
52    if (i < size - 1 && addr[i + 1])
53      pc = patch_pc(pc);
54    char buff[4096];
55    ASAN_USE_EXTERNAL_SYMBOLIZER((void*)pc, buff, sizeof(buff));
56    // We can't know anything about the string returned by external
57    // symbolizer, but if it starts with filename, try to strip path prefix
58    // from it.
59    AsanPrintf("  #%zu 0x%zx %s\n", i, pc, StripPathPrefix(buff));
60  }
61}
62
63#else  // ASAN_USE_EXTERNAL_SYMBOLIZER
64void AsanStackTrace::PrintStack(uptr *addr, uptr size) {
65  ProcessMaps proc_maps;
66  uptr frame_num = 0;
67  for (uptr i = 0; i < size && addr[i]; i++) {
68    uptr pc = addr[i];
69    if (i < size - 1 && addr[i + 1])
70      pc = patch_pc(pc);
71    AddressInfo addr_frames[64];
72    uptr addr_frames_num = 0;
73    if (flags()->symbolize) {
74      addr_frames_num = SymbolizeCode(pc, addr_frames,
75                                      ASAN_ARRAY_SIZE(addr_frames));
76    }
77    if (addr_frames_num > 0) {
78      for (uptr j = 0; j < addr_frames_num; j++) {
79        AddressInfo &info = addr_frames[j];
80        AsanPrintf("    #%zu 0x%zx", frame_num, pc);
81        if (info.function) {
82          AsanPrintf(" in %s", info.function);
83        }
84        if (info.file) {
85          AsanPrintf(" %s:%d:%d", StripPathPrefix(info.file), info.line,
86                                  info.column);
87        } else if (info.module) {
88          AsanPrintf(" (%s+0x%zx)", StripPathPrefix(info.module),
89                                    info.module_offset);
90        }
91        AsanPrintf("\n");
92        info.Clear();
93        frame_num++;
94      }
95    } else {
96      uptr offset;
97      char filename[4096];
98      if (proc_maps.GetObjectNameAndOffset(pc, &offset,
99                                           filename, sizeof(filename))) {
100        AsanPrintf("    #%zu 0x%zx (%s+0x%zx)\n",
101                   frame_num, pc, StripPathPrefix(filename), offset);
102      } else {
103        AsanPrintf("    #%zu 0x%zx\n", frame_num, pc);
104      }
105      frame_num++;
106    }
107  }
108}
109#endif  // ASAN_USE_EXTERNAL_SYMBOLIZER
110
111uptr AsanStackTrace::GetCurrentPc() {
112  return GET_CALLER_PC();
113}
114
115void AsanStackTrace::FastUnwindStack(uptr pc, uptr bp) {
116  CHECK(size == 0 && trace[0] == pc);
117  size = 1;
118  if (!asan_inited) return;
119  AsanThread *t = asanThreadRegistry().GetCurrent();
120  if (!t) return;
121  uptr *frame = (uptr*)bp;
122  uptr *prev_frame = frame;
123  uptr *top = (uptr*)t->stack_top();
124  uptr *bottom = (uptr*)t->stack_bottom();
125  while (frame >= prev_frame &&
126         frame < top - 2 &&
127         frame > bottom &&
128         size < max_size) {
129    uptr pc1 = frame[1];
130    if (pc1 != pc) {
131      trace[size++] = pc1;
132    }
133    prev_frame = frame;
134    frame = (uptr*)frame[0];
135  }
136}
137
138// On 32-bits we don't compress stack traces.
139// On 64-bits we compress stack traces: if a given pc differes slightly from
140// the previous one, we record a 31-bit offset instead of the full pc.
141uptr AsanStackTrace::CompressStack(AsanStackTrace *stack,
142                                   u32 *compressed, uptr size) {
143#if __WORDSIZE == 32
144  // Don't compress, just copy.
145  uptr res = 0;
146  for (uptr i = 0; i < stack->size && i < size; i++) {
147    compressed[i] = stack->trace[i];
148    res++;
149  }
150  if (stack->size < size)
151    compressed[stack->size] = 0;
152#else  // 64 bits, compress.
153  uptr prev_pc = 0;
154  const uptr kMaxOffset = (1ULL << 30) - 1;
155  uptr c_index = 0;
156  uptr res = 0;
157  for (uptr i = 0, n = stack->size; i < n; i++) {
158    uptr pc = stack->trace[i];
159    if (!pc) break;
160    if ((s64)pc < 0) break;
161    // Printf("C pc[%zu] %zx\n", i, pc);
162    if (prev_pc - pc < kMaxOffset || pc - prev_pc < kMaxOffset) {
163      uptr offset = (s64)(pc - prev_pc);
164      offset |= (1U << 31);
165      if (c_index >= size) break;
166      // Printf("C co[%zu] offset %zx\n", i, offset);
167      compressed[c_index++] = offset;
168    } else {
169      uptr hi = pc >> 32;
170      uptr lo = (pc << 32) >> 32;
171      CHECK((hi & (1 << 31)) == 0);
172      if (c_index + 1 >= size) break;
173      // Printf("C co[%zu] hi/lo: %zx %zx\n", c_index, hi, lo);
174      compressed[c_index++] = hi;
175      compressed[c_index++] = lo;
176    }
177    res++;
178    prev_pc = pc;
179  }
180  if (c_index < size)
181    compressed[c_index] = 0;
182  if (c_index + 1 < size)
183    compressed[c_index + 1] = 0;
184#endif  // __WORDSIZE
185
186  // debug-only code
187#if 0
188  AsanStackTrace check_stack;
189  UncompressStack(&check_stack, compressed, size);
190  if (res < check_stack.size) {
191    Printf("res %zu check_stack.size %zu; c_size %zu\n", res,
192           check_stack.size, size);
193  }
194  // |res| may be greater than check_stack.size, because
195  // UncompressStack(CompressStack(stack)) eliminates the 0x0 frames.
196  CHECK(res >= check_stack.size);
197  CHECK(0 == REAL(memcmp)(check_stack.trace, stack->trace,
198                          check_stack.size * sizeof(uptr)));
199#endif
200
201  return res;
202}
203
204void AsanStackTrace::UncompressStack(AsanStackTrace *stack,
205                                     u32 *compressed, uptr size) {
206#if __WORDSIZE == 32
207  // Don't uncompress, just copy.
208  stack->size = 0;
209  for (uptr i = 0; i < size && i < kStackTraceMax; i++) {
210    if (!compressed[i]) break;
211    stack->size++;
212    stack->trace[i] = compressed[i];
213  }
214#else  // 64 bits, uncompress
215  uptr prev_pc = 0;
216  stack->size = 0;
217  for (uptr i = 0; i < size && stack->size < kStackTraceMax; i++) {
218    u32 x = compressed[i];
219    uptr pc = 0;
220    if (x & (1U << 31)) {
221      // Printf("U co[%zu] offset: %x\n", i, x);
222      // this is an offset
223      s32 offset = x;
224      offset = (offset << 1) >> 1;  // remove the 31-byte and sign-extend.
225      pc = prev_pc + offset;
226      CHECK(pc);
227    } else {
228      // CHECK(i + 1 < size);
229      if (i + 1 >= size) break;
230      uptr hi = x;
231      uptr lo = compressed[i+1];
232      // Printf("U co[%zu] hi/lo: %zx %zx\n", i, hi, lo);
233      i++;
234      pc = (hi << 32) | lo;
235      if (!pc) break;
236    }
237    // Printf("U pc[%zu] %zx\n", stack->size, pc);
238    stack->trace[stack->size++] = pc;
239    prev_pc = pc;
240  }
241#endif  // __WORDSIZE
242}
243
244}  // namespace __asan
245