asan_poisoning.h revision 314564 
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
20namespace __asan {
21
22// Enable/disable memory poisoning.
23void SetCanPoisonMemory(bool value);
24bool CanPoisonMemory();
25
26// Poisons the shadow memory for "size" bytes starting from "addr".
27void PoisonShadow(uptr addr, uptr size, u8 value);
28
29// Poisons the shadow memory for "redzone_size" bytes starting from
30// "addr + size".
31void PoisonShadowPartialRightRedzone(uptr addr,
32                                     uptr size,
33                                     uptr redzone_size,
34                                     u8 value);
35
36// Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
37// assume that memory addresses are properly aligned. Use in
38// performance-critical code with care.
39ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
40                                    u8 value) {
41  DCHECK(CanPoisonMemory());
42  uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
43  uptr shadow_end = MEM_TO_SHADOW(
44      aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
45  // FIXME: Page states are different on Windows, so using the same interface
46  // for mapping shadow and zeroing out pages doesn't "just work", so we should
47  // probably provide higher-level interface for these operations.
48  // For now, just memset on Windows.
49  if (value ||
50      SANITIZER_WINDOWS == 1 ||
51      shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
52    REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
53  } else {
54    uptr page_size = GetPageSizeCached();
55    uptr page_beg = RoundUpTo(shadow_beg, page_size);
56    uptr page_end = RoundDownTo(shadow_end, page_size);
57
58    if (page_beg >= page_end) {
59      REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
60    } else {
61      if (page_beg != shadow_beg) {
62        REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
63      }
64      if (page_end != shadow_end) {
65        REAL(memset)((void *)page_end, 0, shadow_end - page_end);
66      }
67      ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
68    }
69  }
70}
71
72ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
73    uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
74  DCHECK(CanPoisonMemory());
75  bool poison_partial = flags()->poison_partial;
76  u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
77  for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
78    if (i + SHADOW_GRANULARITY <= size) {
79      *shadow = 0;  // fully addressable
80    } else if (i >= size) {
81      *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
82    } else {
83      // first size-i bytes are addressable
84      *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
85    }
86  }
87}
88
89// Calls __sanitizer::ReleaseMemoryPagesToOS() on
90// [MemToShadow(p), MemToShadow(p+size)].
91void FlushUnneededASanShadowMemory(uptr p, uptr size);
92
93}  // namespace __asan
94