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
18namespace __asan {
19
20// Enable/disable memory poisoning.
21void SetCanPoisonMemory(bool value);
22bool CanPoisonMemory();
23
24// Poisons the shadow memory for "size" bytes starting from "addr".
25void PoisonShadow(uptr addr, uptr size, u8 value);
26
27// Poisons the shadow memory for "redzone_size" bytes starting from
28// "addr + size".
29void 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.
37ALWAYS_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
76ALWAYS_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)].
95void FlushUnneededASanShadowMemory(uptr p, uptr size);
96
97}  // namespace __asan
98