asan_stack.cc revision 3f4c3875c42078e22c7e5356c5746fd18756d958 
1//===-- asan_stack.cc -------------------------------------------*- C++ -*-===//
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_procmaps.h"
17#include "asan_stack.h"
18#include "asan_thread.h"
19#include "asan_thread_registry.h"
20
21#ifdef ASAN_USE_EXTERNAL_SYMBOLIZER
22extern bool
23ASAN_USE_EXTERNAL_SYMBOLIZER(const void *pc, char *out, int out_size);
24#endif
25
26namespace __asan {
27
28// ----------------------- AsanStackTrace ----------------------------- {{{1
29#if defined(ASAN_USE_EXTERNAL_SYMBOLIZER)
30void AsanStackTrace::PrintStack(uptr *addr, uptr size) {
31  for (uptr i = 0; i < size && addr[i]; i++) {
32    uptr pc = addr[i];
33    char buff[4096];
34    ASAN_USE_EXTERNAL_SYMBOLIZER((void*)pc, buff, sizeof(buff));
35    Printf("  #%zu 0x%zx %s\n", i, pc, buff);
36  }
37}
38
39#else  // ASAN_USE_EXTERNAL_SYMBOLIZER
40void AsanStackTrace::PrintStack(uptr *addr, uptr size) {
41  AsanProcMaps proc_maps;
42  for (uptr i = 0; i < size && addr[i]; i++) {
43    proc_maps.Reset();
44    uptr pc = addr[i];
45    uptr offset;
46    char filename[4096];
47    if (proc_maps.GetObjectNameAndOffset(pc, &offset,
48                                         filename, sizeof(filename))) {
49      Printf("    #%zu 0x%zx (%s+0x%zx)\n", i, pc, filename, offset);
50    } else {
51      Printf("    #%zu 0x%zx\n", i, pc);
52    }
53  }
54}
55#endif  // ASAN_USE_EXTERNAL_SYMBOLIZER
56
57uptr AsanStackTrace::GetCurrentPc() {
58  return GET_CALLER_PC();
59}
60
61void AsanStackTrace::FastUnwindStack(uptr pc, uptr bp) {
62  CHECK(size == 0 && trace[0] == pc);
63  size = 1;
64  if (!asan_inited) return;
65  AsanThread *t = asanThreadRegistry().GetCurrent();
66  if (!t) return;
67  uptr *frame = (uptr*)bp;
68  uptr *prev_frame = frame;
69  uptr *top = (uptr*)t->stack_top();
70  uptr *bottom = (uptr*)t->stack_bottom();
71  while (frame >= prev_frame &&
72         frame < top - 2 &&
73         frame > bottom &&
74         size < max_size) {
75    uptr pc1 = frame[1];
76    if (pc1 != pc) {
77      trace[size++] = pc1;
78    }
79    prev_frame = frame;
80    frame = (uptr*)frame[0];
81  }
82}
83
84// On 32-bits we don't compress stack traces.
85// On 64-bits we compress stack traces: if a given pc differes slightly from
86// the previous one, we record a 31-bit offset instead of the full pc.
87uptr AsanStackTrace::CompressStack(AsanStackTrace *stack,
88                                   uint32_t *compressed, uptr size) {
89#if __WORDSIZE == 32
90  // Don't compress, just copy.
91  uptr res = 0;
92  for (uptr i = 0; i < stack->size && i < size; i++) {
93    compressed[i] = stack->trace[i];
94    res++;
95  }
96  if (stack->size < size)
97    compressed[stack->size] = 0;
98#else  // 64 bits, compress.
99  uptr prev_pc = 0;
100  const uptr kMaxOffset = (1ULL << 30) - 1;
101  uptr c_index = 0;
102  uptr res = 0;
103  for (uptr i = 0, n = stack->size; i < n; i++) {
104    uptr pc = stack->trace[i];
105    if (!pc) break;
106    if ((int64_t)pc < 0) break;
107    // Printf("C pc[%zu] %zx\n", i, pc);
108    if (prev_pc - pc < kMaxOffset || pc - prev_pc < kMaxOffset) {
109      uptr offset = (int64_t)(pc - prev_pc);
110      offset |= (1U << 31);
111      if (c_index >= size) break;
112      // Printf("C co[%zu] offset %zx\n", i, offset);
113      compressed[c_index++] = offset;
114    } else {
115      uptr hi = pc >> 32;
116      uptr lo = (pc << 32) >> 32;
117      CHECK((hi & (1 << 31)) == 0);
118      if (c_index + 1 >= size) break;
119      // Printf("C co[%zu] hi/lo: %zx %zx\n", c_index, hi, lo);
120      compressed[c_index++] = hi;
121      compressed[c_index++] = lo;
122    }
123    res++;
124    prev_pc = pc;
125  }
126  if (c_index < size)
127    compressed[c_index] = 0;
128  if (c_index + 1 < size)
129    compressed[c_index + 1] = 0;
130#endif  // __WORDSIZE
131
132  // debug-only code
133#if 0
134  AsanStackTrace check_stack;
135  UncompressStack(&check_stack, compressed, size);
136  if (res < check_stack.size) {
137    Printf("res %zu check_stack.size %zu; c_size %zu\n", res,
138           check_stack.size, size);
139  }
140  // |res| may be greater than check_stack.size, because
141  // UncompressStack(CompressStack(stack)) eliminates the 0x0 frames.
142  CHECK(res >= check_stack.size);
143  CHECK(0 == REAL(memcmp)(check_stack.trace, stack->trace,
144                          check_stack.size * sizeof(uptr)));
145#endif
146
147  return res;
148}
149
150void AsanStackTrace::UncompressStack(AsanStackTrace *stack,
151                                     uint32_t *compressed, uptr size) {
152#if __WORDSIZE == 32
153  // Don't uncompress, just copy.
154  stack->size = 0;
155  for (uptr i = 0; i < size && i < kStackTraceMax; i++) {
156    if (!compressed[i]) break;
157    stack->size++;
158    stack->trace[i] = compressed[i];
159  }
160#else  // 64 bits, uncompress
161  uptr prev_pc = 0;
162  stack->size = 0;
163  for (uptr i = 0; i < size && stack->size < kStackTraceMax; i++) {
164    uint32_t x = compressed[i];
165    uptr pc = 0;
166    if (x & (1U << 31)) {
167      // Printf("U co[%zu] offset: %x\n", i, x);
168      // this is an offset
169      int32_t offset = x;
170      offset = (offset << 1) >> 1;  // remove the 31-byte and sign-extend.
171      pc = prev_pc + offset;
172      CHECK(pc);
173    } else {
174      // CHECK(i + 1 < size);
175      if (i + 1 >= size) break;
176      uptr hi = x;
177      uptr lo = compressed[i+1];
178      // Printf("U co[%zu] hi/lo: %zx %zx\n", i, hi, lo);
179      i++;
180      pc = (hi << 32) | lo;
181      if (!pc) break;
182    }
183    // Printf("U pc[%zu] %zx\n", stack->size, pc);
184    stack->trace[stack->size++] = pc;
185    prev_pc = pc;
186  }
187#endif  // __WORDSIZE
188}
189
190}  // namespace __asan
191