lib/asan/asan_fake_stack.cc

   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
  18 namespace __asan {
  19
  20 static const u64 kMagic1 = kAsanStackAfterReturnMagic;
  21 static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
  22 static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
  23 static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;
  24
  25 // For small size classes inline PoisonShadow for better performance.
  26 ALWAYS_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
  38 FakeStack *FakeStack::Create(uptr stack_size_log) {
  39   static uptr kMinStackSizeLog = 16;
  40   static uptr kMaxStackSizeLog = FIRST_32_SECOND_64(24, 28);
  41   if (stack_size_log < kMinStackSizeLog)
  42     stack_size_log = kMinStackSizeLog;
  43   if (stack_size_log > kMaxStackSizeLog)
  44     stack_size_log = kMaxStackSizeLog;
  45   uptr size = RequiredSize(stack_size_log);
  46   FakeStack *res = reinterpret_cast<FakeStack *>(
  47       flags()->uar_noreserve ? MmapNoReserveOrDie(size, "FakeStack")
  48                              : MmapOrDie(size, "FakeStack"));
  49   res->stack_size_log_ = stack_size_log;
  50   u8 *p = reinterpret_cast<u8 *>(res);
  51   VReport(1, "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
  52           "mmapped %zdK, noreserve=%d \n",
  53           GetCurrentTidOrInvalid(), p,
  54           p + FakeStack::RequiredSize(stack_size_log), stack_size_log,
  55           size >> 10, flags()->uar_noreserve);
  56   return res;
  57 }
  58
  59 void FakeStack::Destroy(int tid) {
  60   PoisonAll(0);
  61   if (common_flags()->verbosity >= 2) {
  62     InternalScopedString str(kNumberOfSizeClasses * 50);
  63     for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++)
  64       str.append("%zd: %zd/%zd; ", class_id, hint_position_[class_id],
  65                  NumberOfFrames(stack_size_log(), class_id));
  66     Report("T%d: FakeStack destroyed: %s\n", tid, str.data());
  67   }
  68   uptr size = RequiredSize(stack_size_log_);
  69   FlushUnneededASanShadowMemory(reinterpret_cast<uptr>(this), size);
  70   UnmapOrDie(this, size);
  71 }
  72
  73 void FakeStack::PoisonAll(u8 magic) {
  74   PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
  75                magic);
  76 }
  77
  78 ALWAYS_INLINE USED
  79 FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
  80                                uptr real_stack) {
  81   CHECK_LT(class_id, kNumberOfSizeClasses);
  82   if (needs_gc_)
  83     GC(real_stack);
  84   uptr &hint_position = hint_position_[class_id];
  85   const int num_iter = NumberOfFrames(stack_size_log, class_id);
  86   u8 *flags = GetFlags(stack_size_log, class_id);
  87   for (int i = 0; i < num_iter; i++) {
  88     uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
  89     // This part is tricky. On one hand, checking and setting flags[pos]
  90     // should be atomic to ensure async-signal safety. But on the other hand,
  91     // if the signal arrives between checking and setting flags[pos], the
  92     // signal handler's fake stack will start from a different hint_position
  93     // and so will not touch this particular byte. So, it is safe to do this
  94     // with regular non-atimic load and store (at least I was not able to make
  95     // this code crash).
  96     if (flags[pos]) continue;
  97     flags[pos] = 1;
  98     FakeFrame *res = reinterpret_cast<FakeFrame *>(
  99         GetFrame(stack_size_log, class_id, pos));
 100     res->real_stack = real_stack;
 101     *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
 102     return res;
 103   }
 104   return 0; // We are out of fake stack.
 105 }
 106
 107 uptr FakeStack::AddrIsInFakeStack(uptr ptr, uptr *frame_beg, uptr *frame_end) {
 108   uptr stack_size_log = this->stack_size_log();
 109   uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
 110   uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
 111   if (ptr < beg || ptr >= end) return 0;
 112   uptr class_id = (ptr - beg) >> stack_size_log;
 113   uptr base = beg + (class_id << stack_size_log);
 114   CHECK_LE(base, ptr);
 115   CHECK_LT(ptr, base + (1UL << stack_size_log));
 116   uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
 117   uptr res = base + pos * BytesInSizeClass(class_id);
 118   *frame_end = res + BytesInSizeClass(class_id);
 119   *frame_beg = res + sizeof(FakeFrame);
 120   return res;
 121 }
 122
 123 void FakeStack::HandleNoReturn() {
 124   needs_gc_ = true;
 125 }
 126
 127 // When throw, longjmp or some such happens we don't call OnFree() and
 128 // as the result may leak one or more fake frames, but the good news is that
 129 // we are notified about all such events by HandleNoReturn().
 130 // If we recently had such no-return event we need to collect garbage frames.
 131 // We do it based on their 'real_stack' values -- everything that is lower
 132 // than the current real_stack is garbage.
 133 NOINLINE void FakeStack::GC(uptr real_stack) {
 134   uptr collected = 0;
 135   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 136     u8 *flags = GetFlags(stack_size_log(), class_id);
 137     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 138          i++) {
 139       if (flags[i] == 0) continue;  // not allocated.
 140       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 141           GetFrame(stack_size_log(), class_id, i));
 142       if (ff->real_stack < real_stack) {
 143         flags[i] = 0;
 144         collected++;
 145       }
 146     }
 147   }
 148   needs_gc_ = false;
 149 }
 150
 151 void FakeStack::ForEachFakeFrame(RangeIteratorCallback callback, void *arg) {
 152   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 153     u8 *flags = GetFlags(stack_size_log(), class_id);
 154     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 155          i++) {
 156       if (flags[i] == 0) continue;  // not allocated.
 157       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 158           GetFrame(stack_size_log(), class_id, i));
 159       uptr begin = reinterpret_cast<uptr>(ff);
 160       callback(begin, begin + FakeStack::BytesInSizeClass(class_id), arg);
 161     }
 162   }
 163 }
 164
 165 #if SANITIZER_LINUX && !SANITIZER_ANDROID
 166 static THREADLOCAL FakeStack *fake_stack_tls;
 167
 168 FakeStack *GetTLSFakeStack() {
 169   return fake_stack_tls;
 170 }
 171 void SetTLSFakeStack(FakeStack *fs) {
 172   fake_stack_tls = fs;
 173 }
 174 #else
 175 FakeStack *GetTLSFakeStack() { return 0; }
 176 void SetTLSFakeStack(FakeStack *fs) { }
 177 #endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
 178
 179 static FakeStack *GetFakeStack() {
 180   AsanThread *t = GetCurrentThread();
 181   if (!t) return 0;
 182   return t->fake_stack();
 183 }
 184
 185 static FakeStack *GetFakeStackFast() {
 186   if (FakeStack *fs = GetTLSFakeStack())
 187     return fs;
 188   if (!__asan_option_detect_stack_use_after_return)
 189     return 0;
 190   return GetFakeStack();
 191 }
 192
 193 ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size, uptr real_stack) {
 194   FakeStack *fs = GetFakeStackFast();
 195   if (!fs) return real_stack;
 196   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
 197   if (!ff)
 198     return real_stack;  // Out of fake stack, return the real one.
 199   uptr ptr = reinterpret_cast<uptr>(ff);
 200   SetShadow(ptr, size, class_id, 0);
 201   return ptr;
 202 }
 203
 204 ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size, uptr real_stack) {
 205   if (ptr == real_stack)
 206     return;
 207   FakeStack::Deallocate(ptr, class_id);
 208   SetShadow(ptr, size, class_id, kMagic8);
 209 }
 210
 211 }  // namespace __asan
 212
 213 // ---------------------- Interface ---------------- {{{1
 214 using namespace __asan;
 215 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
 216   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
 217   __asan_stack_malloc_##class_id(uptr size, uptr real_stack) {                 \
 218     return OnMalloc(class_id, size, real_stack);                               \
 219   }                                                                            \
 220   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
 221       uptr ptr, uptr size, uptr real_stack) {                                  \
 222     OnFree(ptr, class_id, size, real_stack);                                   \
 223   }
 224
 225 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
 226 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
 227 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
 228 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
 229 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
 230 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
 231 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
 232 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
 233 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
 234 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
 235 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
 236 extern "C" {
 237 SANITIZER_INTERFACE_ATTRIBUTE
 238 void *__asan_get_current_fake_stack() { return GetFakeStackFast(); }
 239
 240 SANITIZER_INTERFACE_ATTRIBUTE
 241 void *__asan_addr_is_in_fake_stack(void *fake_stack, void *addr, void **beg,
 242                                    void **end) {
 243   FakeStack *fs = reinterpret_cast<FakeStack*>(fake_stack);
 244   if (!fs) return 0;
 245   uptr frame_beg, frame_end;
 246   FakeFrame *frame = reinterpret_cast<FakeFrame *>(fs->AddrIsInFakeStack(
 247       reinterpret_cast<uptr>(addr), &frame_beg, &frame_end));
 248   if (!frame) return 0;
 249   if (frame->magic != kCurrentStackFrameMagic)
 250     return 0;
 251   if (beg) *beg = reinterpret_cast<void*>(frame_beg);
 252   if (end) *end = reinterpret_cast<void*>(frame_end);
 253   return reinterpret_cast<void*>(frame->real_stack);
 254 }
 255 }  // extern "C"