libsanitizer/asan/asan_fake_stack.cc

   1 //===-- asan_fake_stack.cc ------------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is a part of AddressSanitizer, an address sanity checker.
   9 //
  10 // FakeStack is used to detect use-after-return bugs.
  11 //===----------------------------------------------------------------------===//
  12 #include "asan_allocator.h"
  13 #include "asan_poisoning.h"
  14 #include "asan_thread.h"
  15
  16 namespace __asan {
  17
  18 static const u64 kMagic1 = kAsanStackAfterReturnMagic;
  19 static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
  20 static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
  21 static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;
  22
  23 // For small size classes inline PoisonShadow for better performance.
  24 ALWAYS_INLINE void SetShadow(uptr ptr, uptr size, uptr class_id, u64 magic) {
  25   CHECK_EQ(SHADOW_SCALE, 3);  // This code expects SHADOW_SCALE=3.
  26   u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
  27   if (class_id <= 6) {
  28     for (uptr i = 0; i < (1U << class_id); i++)
  29       shadow[i] = magic;
  30   } else {
  31     // The size class is too big, it's cheaper to poison only size bytes.
  32     PoisonShadow(ptr, size, static_cast<u8>(magic));
  33   }
  34 }
  35
  36 FakeStack *FakeStack::Create(uptr stack_size_log) {
  37   static uptr kMinStackSizeLog = 16;
  38   static uptr kMaxStackSizeLog = FIRST_32_SECOND_64(24, 28);
  39   if (stack_size_log < kMinStackSizeLog)
  40     stack_size_log = kMinStackSizeLog;
  41   if (stack_size_log > kMaxStackSizeLog)
  42     stack_size_log = kMaxStackSizeLog;
  43   FakeStack *res = reinterpret_cast<FakeStack *>(
  44       MmapOrDie(RequiredSize(stack_size_log), "FakeStack"));
  45   res->stack_size_log_ = stack_size_log;
  46   if (common_flags()->verbosity) {
  47     u8 *p = reinterpret_cast<u8 *>(res);
  48     Report("T%d: FakeStack created: %p -- %p stack_size_log: %zd \n",
  49            GetCurrentTidOrInvalid(), p,
  50            p + FakeStack::RequiredSize(stack_size_log), stack_size_log);
  51   }
  52   return res;
  53 }
  54
  55 void FakeStack::Destroy() {
  56   PoisonAll(0);
  57   UnmapOrDie(this, RequiredSize(stack_size_log_));
  58 }
  59
  60 void FakeStack::PoisonAll(u8 magic) {
  61   PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
  62                magic);
  63 }
  64
  65 ALWAYS_INLINE USED
  66 FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
  67                                uptr real_stack) {
  68   CHECK_LT(class_id, kNumberOfSizeClasses);
  69   if (needs_gc_)
  70     GC(real_stack);
  71   uptr &hint_position = hint_position_[class_id];
  72   const int num_iter = NumberOfFrames(stack_size_log, class_id);
  73   u8 *flags = GetFlags(stack_size_log, class_id);
  74   for (int i = 0; i < num_iter; i++) {
  75     uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
  76     // This part is tricky. On one hand, checking and setting flags[pos]
  77     // should be atomic to ensure async-signal safety. But on the other hand,
  78     // if the signal arrives between checking and setting flags[pos], the
  79     // signal handler's fake stack will start from a different hint_position
  80     // and so will not touch this particular byte. So, it is safe to do this
  81     // with regular non-atimic load and store (at least I was not able to make
  82     // this code crash).
  83     if (flags[pos]) continue;
  84     flags[pos] = 1;
  85     FakeFrame *res = reinterpret_cast<FakeFrame *>(
  86         GetFrame(stack_size_log, class_id, pos));
  87     res->real_stack = real_stack;
  88     *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
  89     return res;
  90   }
  91   return 0; // We are out of fake stack.
  92 }
  93
  94 uptr FakeStack::AddrIsInFakeStack(uptr ptr) {
  95   uptr stack_size_log = this->stack_size_log();
  96   uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
  97   uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
  98   if (ptr < beg || ptr >= end) return 0;
  99   uptr class_id = (ptr - beg) >> stack_size_log;
 100   uptr base = beg + (class_id << stack_size_log);
 101   CHECK_LE(base, ptr);
 102   CHECK_LT(ptr, base + (1UL << stack_size_log));
 103   uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
 104   return base + pos * BytesInSizeClass(class_id);
 105 }
 106
 107 void FakeStack::HandleNoReturn() {
 108   needs_gc_ = true;
 109 }
 110
 111 // When throw, longjmp or some such happens we don't call OnFree() and
 112 // as the result may leak one or more fake frames, but the good news is that
 113 // we are notified about all such events by HandleNoReturn().
 114 // If we recently had such no-return event we need to collect garbage frames.
 115 // We do it based on their 'real_stack' values -- everything that is lower
 116 // than the current real_stack is garbage.
 117 NOINLINE void FakeStack::GC(uptr real_stack) {
 118   uptr collected = 0;
 119   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 120     u8 *flags = GetFlags(stack_size_log(), class_id);
 121     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 122          i++) {
 123       if (flags[i] == 0) continue;  // not allocated.
 124       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 125           GetFrame(stack_size_log(), class_id, i));
 126       if (ff->real_stack < real_stack) {
 127         flags[i] = 0;
 128         collected++;
 129       }
 130     }
 131   }
 132   needs_gc_ = false;
 133 }
 134
 135 void FakeStack::ForEachFakeFrame(RangeIteratorCallback callback, void *arg) {
 136   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 137     u8 *flags = GetFlags(stack_size_log(), class_id);
 138     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 139          i++) {
 140       if (flags[i] == 0) continue;  // not allocated.
 141       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 142           GetFrame(stack_size_log(), class_id, i));
 143       uptr begin = reinterpret_cast<uptr>(ff);
 144       callback(begin, begin + FakeStack::BytesInSizeClass(class_id), arg);
 145     }
 146   }
 147 }
 148
 149 #if SANITIZER_LINUX && !SANITIZER_ANDROID
 150 static THREADLOCAL FakeStack *fake_stack_tls;
 151
 152 FakeStack *GetTLSFakeStack() {
 153   return fake_stack_tls;
 154 }
 155 void SetTLSFakeStack(FakeStack *fs) {
 156   fake_stack_tls = fs;
 157 }
 158 #else
 159 FakeStack *GetTLSFakeStack() { return 0; }
 160 void SetTLSFakeStack(FakeStack *fs) { }
 161 #endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
 162
 163 static FakeStack *GetFakeStack() {
 164   AsanThread *t = GetCurrentThread();
 165   if (!t) return 0;
 166   return t->fake_stack();
 167 }
 168
 169 static FakeStack *GetFakeStackFast() {
 170   if (FakeStack *fs = GetTLSFakeStack())
 171     return fs;
 172   if (!__asan_option_detect_stack_use_after_return)
 173     return 0;
 174   return GetFakeStack();
 175 }
 176
 177 ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size, uptr real_stack) {
 178   FakeStack *fs = GetFakeStackFast();
 179   if (!fs) return real_stack;
 180   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
 181   if (!ff)
 182     return real_stack;  // Out of fake stack, return the real one.
 183   uptr ptr = reinterpret_cast<uptr>(ff);
 184   SetShadow(ptr, size, class_id, 0);
 185   return ptr;
 186 }
 187
 188 ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size, uptr real_stack) {
 189   if (ptr == real_stack)
 190     return;
 191   FakeStack::Deallocate(ptr, class_id);
 192   SetShadow(ptr, size, class_id, kMagic8);
 193 }
 194
 195 }  // namespace __asan
 196
 197 // ---------------------- Interface ---------------- {{{1
 198 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
 199   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
 200   __asan_stack_malloc_##class_id(uptr size, uptr real_stack) {                 \
 201     return __asan::OnMalloc(class_id, size, real_stack);                       \
 202   }                                                                            \
 203   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
 204       uptr ptr, uptr size, uptr real_stack) {                                  \
 205     __asan::OnFree(ptr, class_id, size, real_stack);                           \
 206   }
 207
 208 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
 209 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
 210 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
 211 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
 212 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
 213 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
 214 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
 215 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
 216 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
 217 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
 218 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)