relative_patcher_x86_base.cc revision 71b0ddf988208c9f77e7d2c1e75066cc3fe20c61 
1/*
2 * Copyright (C) 2015 The Android Open Source Project
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 *      http://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#include "linker/x86/relative_patcher_x86_base.h"
18
19namespace art {
20namespace linker {
21
22uint32_t X86BaseRelativePatcher::ReserveSpace(
23    uint32_t offset,
24    const CompiledMethod* compiled_method ATTRIBUTE_UNUSED,
25    MethodReference method_ref ATTRIBUTE_UNUSED) {
26  return offset;  // No space reserved; no limit on relative call distance.
27}
28
29uint32_t X86BaseRelativePatcher::ReserveSpaceEnd(uint32_t offset) {
30  return offset;  // No space reserved; no limit on relative call distance.
31}
32
33uint32_t X86BaseRelativePatcher::WriteThunks(OutputStream* out ATTRIBUTE_UNUSED, uint32_t offset) {
34  return offset;  // No thunks added; no limit on relative call distance.
35}
36
37void X86BaseRelativePatcher::PatchCall(std::vector<uint8_t>* code, uint32_t literal_offset,
38                                       uint32_t patch_offset, uint32_t target_offset) {
39  DCHECK_LE(literal_offset + 4u, code->size());
40  // Unsigned arithmetic with its well-defined overflow behavior is just fine here.
41  uint32_t displacement = target_offset - patch_offset;
42  displacement -= kPcDisplacement;  // The base PC is at the end of the 4-byte patch.
43
44  typedef __attribute__((__aligned__(1))) int32_t unaligned_int32_t;
45  reinterpret_cast<unaligned_int32_t*>(&(*code)[literal_offset])[0] = displacement;
46}
47
48}  // namespace linker
49}  // namespace art
50