1 // Copyright 2025 The Abseil Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #ifndef ABSL_DEBUGGING_INTERNAL_ADDRESSES_H_
16 #define ABSL_DEBUGGING_INTERNAL_ADDRESSES_H_
17
18 #include <stdint.h>
19
20 #include "absl/base/config.h"
21
22 namespace absl {
23 ABSL_NAMESPACE_BEGIN
24 namespace debugging_internal {
25
26 // Removes any metadata (tag bits) from the given pointer, converting it into a
27 // user-readable address.
StripPointerMetadata(void * ptr)28 inline uintptr_t StripPointerMetadata(void* ptr) {
29 #if defined(__aarch64__)
30 // When PAC-RET (-mbranch-protection=pac-ret) is enabled, return addresses
31 // stored on the stack will be signed, which means that pointer bits outside
32 // of the virtual address range are potentially set. Since the stacktrace code
33 // is expected to return normal code pointers, this function clears those
34 // bits.
35 register uintptr_t x30 __asm__("x30") = reinterpret_cast<uintptr_t>(ptr);
36 // The normal instruction for clearing PAC bits is XPACI, but for
37 // compatibility with ARM platforms that do not support pointer
38 // authentication, we use the hint space instruction XPACLRI instead. Hint
39 // space instructions behave as NOPs on unsupported platforms.
40 #define ABSL_XPACLRI_HINT "hint #0x7;"
41 asm(ABSL_XPACLRI_HINT : "+r"(x30)); // asm("xpaclri" : "+r"(x30));
42 #undef ABSL_XPACLRI_HINT
43 return x30;
44 #else
45 return reinterpret_cast<uintptr_t>(ptr);
46 #endif
47 }
48
49 } // namespace debugging_internal
50 ABSL_NAMESPACE_END
51 } // namespace absl
52
53 #endif // ABSL_DEBUGGING_INTERNAL_ADDRESSES_H_
54