aboutsummaryrefslogtreecommitdiff
path: root/lib/asan/asan_fake_stack.cc
blob: bf4f1eb4c781c18d88184d8cd06af0bdbf394382 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
//===-- asan_fake_stack.cc ------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
//
// FakeStack is used to detect use-after-return bugs.
//===----------------------------------------------------------------------===//
#include "asan_allocator.h"
#include "asan_poisoning.h"
#include "asan_thread.h"

namespace __asan {

static const u64 kMagic1 = kAsanStackAfterReturnMagic;
static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;

// For small size classes inline PoisonShadow for better performance.
ALWAYS_INLINE void SetShadow(uptr ptr, uptr size, uptr class_id, u64 magic) {
  CHECK_EQ(SHADOW_SCALE, 3);  // This code expects SHADOW_SCALE=3.
  u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
  if (class_id <= 6) {
    for (uptr i = 0; i < (1U << class_id); i++) {
      shadow[i] = magic;
      SanitizerBreakOptimization(0);  // Make sure this does not become memset.
    }
  } else {
    // The size class is too big, it's cheaper to poison only size bytes.
    PoisonShadow(ptr, size, static_cast<u8>(magic));
  }
}

FakeStack *FakeStack::Create(uptr stack_size_log) {
  static uptr kMinStackSizeLog = 16;
  static uptr kMaxStackSizeLog = FIRST_32_SECOND_64(24, 28);
  if (stack_size_log < kMinStackSizeLog)
    stack_size_log = kMinStackSizeLog;
  if (stack_size_log > kMaxStackSizeLog)
    stack_size_log = kMaxStackSizeLog;
  uptr size = RequiredSize(stack_size_log);
  FakeStack *res = reinterpret_cast<FakeStack *>(
      flags()->uar_noreserve ? MmapNoReserveOrDie(size, "FakeStack")
                             : MmapOrDie(size, "FakeStack"));
  res->stack_size_log_ = stack_size_log;
  u8 *p = reinterpret_cast<u8 *>(res);
  VReport(1, "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
          "mmapped %zdK, noreserve=%d \n",
          GetCurrentTidOrInvalid(), p,
          p + FakeStack::RequiredSize(stack_size_log), stack_size_log,
          size >> 10, flags()->uar_noreserve);
  return res;
}

void FakeStack::Destroy(int tid) {
  PoisonAll(0);
  if (Verbosity() >= 2) {
    InternalScopedString str(kNumberOfSizeClasses * 50);
    for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++)
      str.append("%zd: %zd/%zd; ", class_id, hint_position_[class_id],
                 NumberOfFrames(stack_size_log(), class_id));
    Report("T%d: FakeStack destroyed: %s\n", tid, str.data());
  }
  uptr size = RequiredSize(stack_size_log_);
  FlushUnneededASanShadowMemory(reinterpret_cast<uptr>(this), size);
  UnmapOrDie(this, size);
}

void FakeStack::PoisonAll(u8 magic) {
  PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
               magic);
}

ALWAYS_INLINE USED
FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
                               uptr real_stack) {
  CHECK_LT(class_id, kNumberOfSizeClasses);
  if (needs_gc_)
    GC(real_stack);
  uptr &hint_position = hint_position_[class_id];
  const int num_iter = NumberOfFrames(stack_size_log, class_id);
  u8 *flags = GetFlags(stack_size_log, class_id);
  for (int i = 0; i < num_iter; i++) {
    uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
    // This part is tricky. On one hand, checking and setting flags[pos]
    // should be atomic to ensure async-signal safety. But on the other hand,
    // if the signal arrives between checking and setting flags[pos], the
    // signal handler's fake stack will start from a different hint_position
    // and so will not touch this particular byte. So, it is safe to do this
    // with regular non-atimic load and store (at least I was not able to make
    // this code crash).
    if (flags[pos]) continue;
    flags[pos] = 1;
    FakeFrame *res = reinterpret_cast<FakeFrame *>(
        GetFrame(stack_size_log, class_id, pos));
    res->real_stack = real_stack;
    *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
    return res;
  }
  return 0; // We are out of fake stack.
}

uptr FakeStack::AddrIsInFakeStack(uptr ptr, uptr *frame_beg, uptr *frame_end) {
  uptr stack_size_log = this->stack_size_log();
  uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
  uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
  if (ptr < beg || ptr >= end) return 0;
  uptr class_id = (ptr - beg) >> stack_size_log;
  uptr base = beg + (class_id << stack_size_log);
  CHECK_LE(base, ptr);
  CHECK_LT(ptr, base + (1UL << stack_size_log));
  uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
  uptr res = base + pos * BytesInSizeClass(class_id);
  *frame_end = res + BytesInSizeClass(class_id);
  *frame_beg = res + sizeof(FakeFrame);
  return res;
}

void FakeStack::HandleNoReturn() {
  needs_gc_ = true;
}

// When throw, longjmp or some such happens we don't call OnFree() and
// as the result may leak one or more fake frames, but the good news is that
// we are notified about all such events by HandleNoReturn().
// If we recently had such no-return event we need to collect garbage frames.
// We do it based on their 'real_stack' values -- everything that is lower
// than the current real_stack is garbage.
NOINLINE void FakeStack::GC(uptr real_stack) {
  uptr collected = 0;
  for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
    u8 *flags = GetFlags(stack_size_log(), class_id);
    for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
         i++) {
      if (flags[i] == 0) continue;  // not allocated.
      FakeFrame *ff = reinterpret_cast<FakeFrame *>(
          GetFrame(stack_size_log(), class_id, i));
      if (ff->real_stack < real_stack) {
        flags[i] = 0;
        collected++;
      }
    }
  }
  needs_gc_ = false;
}

void FakeStack::ForEachFakeFrame(RangeIteratorCallback callback, void *arg) {
  for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
    u8 *flags = GetFlags(stack_size_log(), class_id);
    for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
         i++) {
      if (flags[i] == 0) continue;  // not allocated.
      FakeFrame *ff = reinterpret_cast<FakeFrame *>(
          GetFrame(stack_size_log(), class_id, i));
      uptr begin = reinterpret_cast<uptr>(ff);
      callback(begin, begin + FakeStack::BytesInSizeClass(class_id), arg);
    }
  }
}

#if SANITIZER_LINUX && !SANITIZER_ANDROID
static THREADLOCAL FakeStack *fake_stack_tls;

FakeStack *GetTLSFakeStack() {
  return fake_stack_tls;
}
void SetTLSFakeStack(FakeStack *fs) {
  fake_stack_tls = fs;
}
#else
FakeStack *GetTLSFakeStack() { return 0; }
void SetTLSFakeStack(FakeStack *fs) { }
#endif  // SANITIZER_LINUX && !SANITIZER_ANDROID

static FakeStack *GetFakeStack() {
  AsanThread *t = GetCurrentThread();
  if (!t) return 0;
  return t->fake_stack();
}

static FakeStack *GetFakeStackFast() {
  if (FakeStack *fs = GetTLSFakeStack())
    return fs;
  if (!__asan_option_detect_stack_use_after_return)
    return 0;
  return GetFakeStack();
}

ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size) {
  FakeStack *fs = GetFakeStackFast();
  if (!fs) return 0;
  uptr local_stack;
  uptr real_stack = reinterpret_cast<uptr>(&local_stack);
  FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
  if (!ff) return 0;  // Out of fake stack.
  uptr ptr = reinterpret_cast<uptr>(ff);
  SetShadow(ptr, size, class_id, 0);
  return ptr;
}

ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size) {
  FakeStack::Deallocate(ptr, class_id);
  SetShadow(ptr, size, class_id, kMagic8);
}

}  // namespace __asan

// ---------------------- Interface ---------------- {{{1
using namespace __asan;
#define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
  extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
      __asan_stack_malloc_##class_id(uptr size) {                              \
    return OnMalloc(class_id, size);                                           \
  }                                                                            \
  extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
      uptr ptr, uptr size) {                                                   \
    OnFree(ptr, class_id, size);                                               \
  }

DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
extern "C" {
SANITIZER_INTERFACE_ATTRIBUTE
void *__asan_get_current_fake_stack() { return GetFakeStackFast(); }

SANITIZER_INTERFACE_ATTRIBUTE
void *__asan_addr_is_in_fake_stack(void *fake_stack, void *addr, void **beg,
                                   void **end) {
  FakeStack *fs = reinterpret_cast<FakeStack*>(fake_stack);
  if (!fs) return 0;
  uptr frame_beg, frame_end;
  FakeFrame *frame = reinterpret_cast<FakeFrame *>(fs->AddrIsInFakeStack(
      reinterpret_cast<uptr>(addr), &frame_beg, &frame_end));
  if (!frame) return 0;
  if (frame->magic != kCurrentStackFrameMagic)
    return 0;
  if (beg) *beg = reinterpret_cast<void*>(frame_beg);
  if (end) *end = reinterpret_cast<void*>(frame_end);
  return reinterpret_cast<void*>(frame->real_stack);
}
}  // extern "C"