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 // Enable/disable memory poisoning.
21 void SetCanPoisonMemory(bool value);
22 bool CanPoisonMemory();
23
24 // Poisons the shadow memory for "size" bytes starting from "addr".
25 void PoisonShadow(uptr addr, uptr size, u8 value);
26
27 // Poisons the shadow memory for "redzone_size" bytes starting from
28 // "addr + size".
29 void 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.
FastPoisonShadow(uptr aligned_beg,uptr aligned_size,u8 value)37 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
38 u8 value) {
39 DCHECK(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 shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
53 REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
54 } else {
55 uptr page_size = GetPageSizeCached();
56 uptr page_beg = RoundUpTo(shadow_beg, page_size);
57 uptr page_end = RoundDownTo(shadow_end, page_size);
58
59 if (page_beg >= page_end) {
60 REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
61 } else {
62 if (page_beg != shadow_beg) {
63 REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
64 }
65 if (page_end != shadow_end) {
66 REAL(memset)((void *)page_end, 0, shadow_end - page_end);
67 }
68 ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
69 }
70 }
71 }
72
FastPoisonShadowPartialRightRedzone(uptr aligned_addr,uptr size,uptr redzone_size,u8 value)73 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
74 uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
75 DCHECK(CanPoisonMemory());
76 bool poison_partial = flags()->poison_partial;
77 u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
78 for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
79 if (i + SHADOW_GRANULARITY <= size) {
80 *shadow = 0; // fully addressable
81 } else if (i >= size) {
82 *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value; // unaddressable
83 } else {
84 // first size-i bytes are addressable
85 *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
86 }
87 }
88 }
89
90 // Calls __sanitizer::ReleaseMemoryPagesToOS() on
91 // [MemToShadow(p), MemToShadow(p+size)].
92 void FlushUnneededASanShadowMemory(uptr p, uptr size);
93
94 } // namespace __asan
95