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 // Poisons the shadow memory for "size" bytes starting from "addr".
  21 void PoisonShadow(uptr addr, uptr size, u8 value);
  22
  23 // Poisons the shadow memory for "redzone_size" bytes starting from
  24 // "addr + size".
  25 void PoisonShadowPartialRightRedzone(uptr addr,
  26                                      uptr size,
  27                                      uptr redzone_size,
  28                                      u8 value);
  29
  30 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
  31 // assume that memory addresses are properly aligned. Use in
  32 // performance-critical code with care.
  33 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
  34                                     u8 value) {
  35   DCHECK(flags()->poison_heap);
  36   uptr PageSize = GetPageSizeCached();
  37   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
  38   uptr shadow_end = MEM_TO_SHADOW(
  39       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
  40   // FIXME: Page states are different on Windows, so using the same interface
  41   // for mapping shadow and zeroing out pages doesn't "just work", so we should
  42   // probably provide higher-level interface for these operations.
  43   // For now, just memset on Windows.
  44   if (value ||
  45       SANITIZER_WINDOWS == 1 ||
  46       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
  47     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
  48   } else {
  49     uptr page_beg = RoundUpTo(shadow_beg, PageSize);
  50     uptr page_end = RoundDownTo(shadow_end, PageSize);
  51
  52     if (page_beg >= page_end) {
  53       REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
  54     } else {
  55       if (page_beg != shadow_beg) {
  56         REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
  57       }
  58       if (page_end != shadow_end) {
  59         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
  60       }
  61       void *res = MmapFixedNoReserve(page_beg, page_end - page_beg);
  62       CHECK_EQ(page_beg, res);
  63     }
  64   }
  65 }
  66
  67 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
  68     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
  69   DCHECK(flags()->poison_heap);
  70   bool poison_partial = flags()->poison_partial;
  71   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
  72   for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
  73     if (i + SHADOW_GRANULARITY <= size) {
  74       *shadow = 0;  // fully addressable
  75     } else if (i >= size) {
  76       *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
  77     } else {
  78       // first size-i bytes are addressable
  79       *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
  80     }
  81   }
  82 }
  83
  84 // Calls __sanitizer::FlushUnneededShadowMemory() on
  85 // [MemToShadow(p), MemToShadow(p+size)] with proper rounding.
  86 void FlushUnneededASanShadowMemory(uptr p, uptr size);
  87
  88 }  // namespace __asan