lib/asan/asan_poisoning.h

   1 //===-- asan_poisoning.h ----------------------------------------*- C++ -*-===//
   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 // Shadow memory poisoning by ASan RTL and by user application.
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "asan_interceptors.h"
  16 #include "asan_internal.h"
  17 #include "asan_mapping.h"
  18 #include "sanitizer_common/sanitizer_flags.h"
  19
  20 namespace __asan {
  21
  22 // Poisons the shadow memory for "size" bytes starting from "addr".
  23 void PoisonShadow(uptr addr, uptr size, u8 value);
  24
  25 // Poisons the shadow memory for "redzone_size" bytes starting from
  26 // "addr + size".
  27 void PoisonShadowPartialRightRedzone(uptr addr,
  28                                      uptr size,
  29                                      uptr redzone_size,
  30                                      u8 value);
  31
  32 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
  33 // assume that memory addresses are properly aligned. Use in
  34 // performance-critical code with care.
  35 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
  36                                     u8 value) {
  37   DCHECK(flags()->poison_heap);
  38   uptr PageSize = GetPageSizeCached();
  39   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
  40   uptr shadow_end = MEM_TO_SHADOW(
  41       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
  42   // FIXME: Page states are different on Windows, so using the same interface
  43   // for mapping shadow and zeroing out pages doesn't "just work", so we should
  44   // probably provide higher-level interface for these operations.
  45   // For now, just memset on Windows.
  46   if (value ||
  47       SANITIZER_WINDOWS == 1 ||
  48       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
  49     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
  50   } else {
  51     uptr page_beg = RoundUpTo(shadow_beg, PageSize);
  52     uptr page_end = RoundDownTo(shadow_end, PageSize);
  53
  54     if (page_beg >= page_end) {
  55       REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
  56     } else {
  57       if (page_beg != shadow_beg) {
  58         REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
  59       }
  60       if (page_end != shadow_end) {
  61         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
  62       }
  63       void *res = MmapFixedNoReserve(page_beg, page_end - page_beg);
  64       CHECK_EQ(page_beg, res);
  65     }
  66   }
  67 }
  68
  69 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
  70     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
  71   DCHECK(flags()->poison_heap);
  72   bool poison_partial = flags()->poison_partial;
  73   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
  74   for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
  75     if (i + SHADOW_GRANULARITY <= size) {
  76       *shadow = 0;  // fully addressable
  77     } else if (i >= size) {
  78       *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
  79     } else {
  80       // first size-i bytes are addressable
  81       *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
  82     }
  83   }
  84 }
  85
  86 // Calls __sanitizer::FlushUnneededShadowMemory() on
  87 // [MemToShadow(p), MemToShadow(p+size)] with proper rounding.
  88 void FlushUnneededASanShadowMemory(uptr p, uptr size);
  89
  90 }  // namespace __asan