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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.h"
18 
19 #include "linker/linker_patch.h"
20 
21 namespace art {
22 namespace linker {
23 
PatchPcRelativeReference(std::vector<uint8_t> * code,const LinkerPatch & patch,uint32_t patch_offset,uint32_t target_offset)24 void X86RelativePatcher::PatchPcRelativeReference(std::vector<uint8_t>* code,
25                                                   const LinkerPatch& patch,
26                                                   uint32_t patch_offset,
27                                                   uint32_t target_offset) {
28   uint32_t anchor_literal_offset = patch.PcInsnOffset();
29   uint32_t literal_offset = patch.LiteralOffset();
30 
31   // Check that the anchor points to pop in a "call +0; pop <reg>" sequence.
32   DCHECK_GE(anchor_literal_offset, 5u);
33   DCHECK_LT(anchor_literal_offset, code->size());
34   DCHECK_EQ((*code)[anchor_literal_offset - 5u], 0xe8u);
35   DCHECK_EQ((*code)[anchor_literal_offset - 4u], 0x00u);
36   DCHECK_EQ((*code)[anchor_literal_offset - 3u], 0x00u);
37   DCHECK_EQ((*code)[anchor_literal_offset - 2u], 0x00u);
38   DCHECK_EQ((*code)[anchor_literal_offset - 1u], 0x00u);
39   DCHECK_EQ((*code)[anchor_literal_offset] & 0xf8u, 0x58u);
40 
41   // Check that the patched data contains kPlaceholder32BitOffset.
42   // Must match CodeGeneratorX86_64::kPlaceholder32BitOffset.
43   constexpr int kPlaceholder32BitOffset = 256;
44   DCHECK_LE(literal_offset, code->size());
45   DCHECK_EQ((*code)[literal_offset + 0u], static_cast<uint8_t>(kPlaceholder32BitOffset >> 0));
46   DCHECK_EQ((*code)[literal_offset + 1u], static_cast<uint8_t>(kPlaceholder32BitOffset >> 8));
47   DCHECK_EQ((*code)[literal_offset + 2u], static_cast<uint8_t>(kPlaceholder32BitOffset >> 16));
48   DCHECK_EQ((*code)[literal_offset + 3u], static_cast<uint8_t>(kPlaceholder32BitOffset >> 24));
49 
50   // Apply patch.
51   uint32_t anchor_offset = patch_offset - literal_offset + anchor_literal_offset;
52   uint32_t diff = target_offset - anchor_offset;
53   (*code)[literal_offset + 0u] = static_cast<uint8_t>(diff >> 0);
54   (*code)[literal_offset + 1u] = static_cast<uint8_t>(diff >> 8);
55   (*code)[literal_offset + 2u] = static_cast<uint8_t>(diff >> 16);
56   (*code)[literal_offset + 3u] = static_cast<uint8_t>(diff >> 24);
57 }
58 
PatchEntrypointCall(std::vector<uint8_t> * code ATTRIBUTE_UNUSED,const LinkerPatch & patch ATTRIBUTE_UNUSED,uint32_t patch_offset ATTRIBUTE_UNUSED)59 void X86RelativePatcher::PatchEntrypointCall(std::vector<uint8_t>* code ATTRIBUTE_UNUSED,
60                                              const LinkerPatch& patch ATTRIBUTE_UNUSED,
61                                              uint32_t patch_offset ATTRIBUTE_UNUSED) {
62   LOG(FATAL) << "UNIMPLEMENTED";
63 }
64 
PatchBakerReadBarrierBranch(std::vector<uint8_t> * code ATTRIBUTE_UNUSED,const LinkerPatch & patch ATTRIBUTE_UNUSED,uint32_t patch_offset ATTRIBUTE_UNUSED)65 void X86RelativePatcher::PatchBakerReadBarrierBranch(std::vector<uint8_t>* code ATTRIBUTE_UNUSED,
66                                                      const LinkerPatch& patch ATTRIBUTE_UNUSED,
67                                                      uint32_t patch_offset ATTRIBUTE_UNUSED) {
68   LOG(FATAL) << "UNIMPLEMENTED";
69 }
70 
71 }  // namespace linker
72 }  // namespace art
73