asan_fake_stack.cc revision b388987bf988435ee87dc4848ea8e62ebfa942eb 
1//===-- asan_fake_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// FakeStack is used to detect use-after-return bugs.
13//===----------------------------------------------------------------------===//
14#include "asan_allocator.h"
15#include "asan_poisoning.h"
16#include "asan_thread.h"
17
18namespace __asan {
19
20static const u64 kMagic1 = kAsanStackAfterReturnMagic;
21static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
22static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
23static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;
24
25// For small size classes inline PoisonShadow for better performance.
26ALWAYS_INLINE void SetShadow(uptr ptr, uptr size, uptr class_id, u64 magic) {
27  CHECK_EQ(SHADOW_SCALE, 3);  // This code expects SHADOW_SCALE=3.
28  u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
29  if (class_id <= 6) {
30    for (uptr i = 0; i < (1U << class_id); i++)
31      shadow[i] = magic;
32  } else {
33    // The size class is too big, it's cheaper to poison only size bytes.
34    PoisonShadow(ptr, size, static_cast<u8>(magic));
35  }
36}
37
38void FakeStack::PoisonAll(u8 magic) {
39  PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
40               magic);
41}
42
43ALWAYS_INLINE USED
44FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
45                               uptr real_stack) {
46  CHECK_LT(class_id, kNumberOfSizeClasses);
47  if (needs_gc_)
48    GC(real_stack);
49  uptr &hint_position = hint_position_[class_id];
50  const int num_iter = NumberOfFrames(stack_size_log, class_id);
51  u8 *flags = GetFlags(stack_size_log, class_id);
52  for (int i = 0; i < num_iter; i++) {
53    uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
54    // This part is tricky. On one hand, checking and setting flags[pos]
55    // should be atomic to ensure async-signal safety. But on the other hand,
56    // if the signal arrives between checking and setting flags[pos], the
57    // signal handler's fake stack will start from a different hint_position
58    // and so will not touch this particular byte. So, it is safe to do this
59    // with regular non-atimic load and store (at least I was not able to make
60    // this code crash).
61    if (flags[pos]) continue;
62    flags[pos] = 1;
63    FakeFrame *res = reinterpret_cast<FakeFrame *>(
64        GetFrame(stack_size_log, class_id, pos));
65    res->real_stack = real_stack;
66    *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
67    return res;
68  }
69  CHECK(0 && "Failed to allocate a fake stack frame");
70  return 0;
71}
72
73uptr FakeStack::AddrIsInFakeStack(uptr ptr) {
74  uptr stack_size_log = this->stack_size_log();
75  uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
76  uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
77  if (ptr < beg || ptr >= end) return 0;
78  uptr class_id = (ptr - beg) >> stack_size_log;
79  uptr base = beg + (class_id << stack_size_log);
80  CHECK_LE(base, ptr);
81  CHECK_LT(ptr, base + (1UL << stack_size_log));
82  uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
83  return base + pos * BytesInSizeClass(class_id);
84}
85
86void FakeStack::HandleNoReturn() {
87  needs_gc_ = true;
88}
89
90// When throw, longjmp or some such happens we don't call OnFree() and
91// as the result may leak one or more fake frames, but the good news is that
92// we are notified about all such events by HandleNoReturn().
93// If we recently had such no-return event we need to collect garbage frames.
94// We do it based on their 'real_stack' values -- everything that is lower
95// than the current real_stack is garbage.
96NOINLINE void FakeStack::GC(uptr real_stack) {
97  uptr collected = 0;
98  for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
99    u8 *flags = GetFlags(stack_size_log(), class_id);
100    for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
101         i++) {
102      if (flags[i] == 0) continue;  // not allocated.
103      FakeFrame *ff = reinterpret_cast<FakeFrame *>(
104          GetFrame(stack_size_log(), class_id, i));
105      if (ff->real_stack < real_stack) {
106        flags[i] = 0;
107        collected++;
108      }
109    }
110  }
111  needs_gc_ = false;
112}
113
114#if SANITIZER_LINUX && !SANITIZER_ANDROID
115static THREADLOCAL FakeStack *fake_stack_tls;
116
117FakeStack *GetTLSFakeStack() {
118  return fake_stack_tls;
119}
120void SetTLSFakeStack(FakeStack *fs) {
121  fake_stack_tls = fs;
122}
123#else
124FakeStack *GetTLSFakeStack() { return 0; }
125void SetTLSFakeStack(FakeStack *fs) { }
126#endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
127
128static FakeStack *GetFakeStack() {
129  AsanThread *t = GetCurrentThread();
130  if (!t) return 0;
131  return t->fake_stack();
132}
133
134static FakeStack *GetFakeStackFast() {
135  if (FakeStack *fs = GetTLSFakeStack())
136    return fs;
137  return GetFakeStack();
138}
139
140ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size, uptr real_stack) {
141  FakeStack *fs = GetFakeStackFast();
142  if (!fs) return real_stack;
143  FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
144  uptr ptr = reinterpret_cast<uptr>(ff);
145  SetShadow(ptr, size, class_id, 0);
146  return ptr;
147}
148
149ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size, uptr real_stack) {
150  if (ptr == real_stack)
151    return;
152  FakeStack::Deallocate(ptr, class_id);
153  SetShadow(ptr, size, class_id, kMagic8);
154}
155
156}  // namespace __asan
157
158// ---------------------- Interface ---------------- {{{1
159#define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
160  extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
161  __asan_stack_malloc_##class_id(uptr size, uptr real_stack) {                 \
162    return __asan::OnMalloc(class_id, size, real_stack);                       \
163  }                                                                            \
164  extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
165      uptr ptr, uptr size, uptr real_stack) {                                  \
166    __asan::OnFree(ptr, class_id, size, real_stack);                           \
167  }
168
169DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
170DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
171DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
172DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
173DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
174DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
175DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
176DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
177DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
178DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
179DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
180