1//
2// Copyright 2017 The Abseil Authors.
3//
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at
7//
8// https://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15//
16
17#ifndef ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
18#define ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
19
20#include <string.h>
21#include <cstdint>
22
23#include "absl/base/attributes.h"
24
25// unaligned APIs
26
27// Portable handling of unaligned loads, stores, and copies.
28
29// The unaligned API is C++ only. The declarations use C++ features
30// (namespaces, inline) which are absent or incompatible in C.
31#if defined(__cplusplus)
32
33#if defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) ||\
34 defined(MEMORY_SANITIZER)
35// Consider we have an unaligned load/store of 4 bytes from address 0x...05.
36// AddressSanitizer will treat it as a 3-byte access to the range 05:07 and
37// will miss a bug if 08 is the first unaddressable byte.
38// ThreadSanitizer will also treat this as a 3-byte access to 05:07 and will
39// miss a race between this access and some other accesses to 08.
40// MemorySanitizer will correctly propagate the shadow on unaligned stores
41// and correctly report bugs on unaligned loads, but it may not properly
42// update and report the origin of the uninitialized memory.
43// For all three tools, replacing an unaligned access with a tool-specific
44// callback solves the problem.
45
46// Make sure uint16_t/uint32_t/uint64_t are defined.
47#include <stdint.h>
48
49extern "C" {
50uint16_t __sanitizer_unaligned_load16(const void *p);
51uint32_t __sanitizer_unaligned_load32(const void *p);
52uint64_t __sanitizer_unaligned_load64(const void *p);
53void __sanitizer_unaligned_store16(void *p, uint16_t v);
54void __sanitizer_unaligned_store32(void *p, uint32_t v);
55void __sanitizer_unaligned_store64(void *p, uint64_t v);
56} // extern "C"
57
58namespace absl {
59namespace base_internal {
60
61inline uint16_t UnalignedLoad16(const void *p) {
62 return __sanitizer_unaligned_load16(p);
63}
64
65inline uint32_t UnalignedLoad32(const void *p) {
66 return __sanitizer_unaligned_load32(p);
67}
68
69inline uint64_t UnalignedLoad64(const void *p) {
70 return __sanitizer_unaligned_load64(p);
71}
72
73inline void UnalignedStore16(void *p, uint16_t v) {
74 __sanitizer_unaligned_store16(p, v);
75}
76
77inline void UnalignedStore32(void *p, uint32_t v) {
78 __sanitizer_unaligned_store32(p, v);
79}
80
81inline void UnalignedStore64(void *p, uint64_t v) {
82 __sanitizer_unaligned_store64(p, v);
83}
84
85} // namespace base_internal
86} // namespace absl
87
88#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
89 (absl::base_internal::UnalignedLoad16(_p))
90#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
91 (absl::base_internal::UnalignedLoad32(_p))
92#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
93 (absl::base_internal::UnalignedLoad64(_p))
94
95#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
96 (absl::base_internal::UnalignedStore16(_p, _val))
97#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
98 (absl::base_internal::UnalignedStore32(_p, _val))
99#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
100 (absl::base_internal::UnalignedStore64(_p, _val))
101
102#else
103
104namespace absl {
105namespace base_internal {
106
107inline uint16_t UnalignedLoad16(const void *p) {
108 uint16_t t;
109 memcpy(&t, p, sizeof t);
110 return t;
111}
112
113inline uint32_t UnalignedLoad32(const void *p) {
114 uint32_t t;
115 memcpy(&t, p, sizeof t);
116 return t;
117}
118
119inline uint64_t UnalignedLoad64(const void *p) {
120 uint64_t t;
121 memcpy(&t, p, sizeof t);
122 return t;
123}
124
125inline void UnalignedStore16(void *p, uint16_t v) { memcpy(p, &v, sizeof v); }
126
127inline void UnalignedStore32(void *p, uint32_t v) { memcpy(p, &v, sizeof v); }
128
129inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); }
130
131} // namespace base_internal
132} // namespace absl
133
134#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
135 (absl::base_internal::UnalignedLoad16(_p))
136#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
137 (absl::base_internal::UnalignedLoad32(_p))
138#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
139 (absl::base_internal::UnalignedLoad64(_p))
140
141#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
142 (absl::base_internal::UnalignedStore16(_p, _val))
143#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
144 (absl::base_internal::UnalignedStore32(_p, _val))
145#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
146 (absl::base_internal::UnalignedStore64(_p, _val))
147
148#endif
149
150#endif // defined(__cplusplus), end of unaligned API
151
152#endif // ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
153