1//===-- asan_poisoning.h ----------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file is a part of AddressSanitizer, an address sanity checker.
10//
11// Shadow memory poisoning by ASan RTL and by user application.
12//===----------------------------------------------------------------------===//
13
14#include "asan_interceptors.h"
15#include "asan_internal.h"
16#include "asan_mapping.h"
17#include "sanitizer_common/sanitizer_flags.h"
18#include "sanitizer_common/sanitizer_platform.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(!value || CanPoisonMemory());
42#if SANITIZER_FUCHSIA
43 __sanitizer_fill_shadow(aligned_beg, aligned_size, value,
44 common_flags()->clear_shadow_mmap_threshold);
45#else
46 uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
47 uptr shadow_end =
48 MEM_TO_SHADOW(aligned_beg + aligned_size - ASAN_SHADOW_GRANULARITY) + 1;
49 // FIXME: Page states are different on Windows, so using the same interface
50 // for mapping shadow and zeroing out pages doesn't "just work", so we should
51 // probably provide higher-level interface for these operations.
52 // For now, just memset on Windows.
53 if (value || SANITIZER_WINDOWS == 1 ||
54 shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
55 REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
56 } else {
57 uptr page_size = GetPageSizeCached();
58 uptr page_beg = RoundUpTo(size: shadow_beg, boundary: page_size);
59 uptr page_end = RoundDownTo(x: shadow_end, boundary: page_size);
60
61 if (page_beg >= page_end) {
62 REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
63 } else {
64 if (page_beg != shadow_beg) {
65 REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
66 }
67 if (page_end != shadow_end) {
68 REAL(memset)((void *)page_end, 0, shadow_end - page_end);
69 }
70 ReserveShadowMemoryRange(beg: page_beg, end: page_end - 1, name: nullptr);
71 }
72 }
73#endif // SANITIZER_FUCHSIA
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 += ASAN_SHADOW_GRANULARITY, shadow++) {
82 if (i + ASAN_SHADOW_GRANULARITY <= size) {
83 *shadow = 0; // fully addressable
84 } else if (i >= size) {
85 *shadow =
86 (ASAN_SHADOW_GRANULARITY == 128) ? 0xff : value; // unaddressable
87 } else {
88 // first size-i bytes are addressable
89 *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
90 }
91 }
92}
93
94// Calls __sanitizer::ReleaseMemoryPagesToOS() on
95// [MemToShadow(p), MemToShadow(p+size)].
96void FlushUnneededASanShadowMemory(uptr p, uptr size);
97
98} // namespace __asan
99

source code of compiler-rt/lib/asan/asan_poisoning.h