libsanitizer/asan/asan_poisoning.h

   1 //===-- asan_poisoning.h ----------------------------------------*- C++ -*-===//
   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 // Shadow memory poisoning by ASan RTL and by user application.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "asan_interceptors.h"
  14 #include "asan_internal.h"
  15 #include "asan_mapping.h"
  16 #include "sanitizer_common/sanitizer_flags.h"
  17
  18 namespace __asan {
  19
  20 // Enable/disable memory poisoning.
  21 void SetCanPoisonMemory(bool value);
  22 bool CanPoisonMemory();
  23
  24 // Poisons the shadow memory for "size" bytes starting from "addr".
  25 void PoisonShadow(uptr addr, uptr size, u8 value);
  26
  27 // Poisons the shadow memory for "redzone_size" bytes starting from
  28 // "addr + size".
  29 void PoisonShadowPartialRightRedzone(uptr addr,
  30                                      uptr size,
  31                                      uptr redzone_size,
  32                                      u8 value);
  33
  34 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
  35 // assume that memory addresses are properly aligned. Use in
  36 // performance-critical code with care.
  37 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
  38                                     u8 value) {
  39   DCHECK(!value || CanPoisonMemory());
  40   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
  41   uptr shadow_end = MEM_TO_SHADOW(
  42       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
  43   // FIXME: Page states are different on Windows, so using the same interface
  44   // for mapping shadow and zeroing out pages doesn't "just work", so we should
  45   // probably provide higher-level interface for these operations.
  46   // For now, just memset on Windows.
  47   if (value || SANITIZER_WINDOWS == 1 ||
  48       // TODO(mcgrathr): Fuchsia doesn't allow the shadow mapping to be
  49       // changed at all.  It doesn't currently have an efficient means
  50       // to zero a bunch of pages, but maybe we should add one.
  51       SANITIZER_FUCHSIA == 1 ||
  52       // RTEMS doesn't have have pages, let alone a fast way to zero
  53       // them, so default to memset.
  54       SANITIZER_RTEMS == 1 ||
  55       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
  56     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
  57   } else {
  58     uptr page_size = GetPageSizeCached();
  59     uptr page_beg = RoundUpTo(shadow_beg, page_size);
  60     uptr page_end = RoundDownTo(shadow_end, page_size);
  61
  62     if (page_beg >= page_end) {
  63       REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
  64     } else {
  65       if (page_beg != shadow_beg) {
  66         REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
  67       }
  68       if (page_end != shadow_end) {
  69         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
  70       }
  71       ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
  72     }
  73   }
  74 }
  75
  76 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
  77     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
  78   DCHECK(CanPoisonMemory());
  79   bool poison_partial = flags()->poison_partial;
  80   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
  81   for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
  82     if (i + SHADOW_GRANULARITY <= size) {
  83       *shadow = 0;  // fully addressable
  84     } else if (i >= size) {
  85       *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
  86     } else {
  87       // first size-i bytes are addressable
  88       *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
  89     }
  90   }
  91 }
  92
  93 // Calls __sanitizer::ReleaseMemoryPagesToOS() on
  94 // [MemToShadow(p), MemToShadow(p+size)].
  95 void FlushUnneededASanShadowMemory(uptr p, uptr size);
  96
  97 }  // namespace __asan