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#ifndef ART_COMPILER_LINKER_RELATIVE_PATCHER_H_
18#define ART_COMPILER_LINKER_RELATIVE_PATCHER_H_
19
20#include <vector>
21
22#include "arch/instruction_set.h"
23#include "arch/instruction_set_features.h"
24#include "base/array_ref.h"
25#include "base/macros.h"
26#include "dex/method_reference.h"
27
28namespace art {
29
30class CompiledMethod;
31
32namespace debug {
33struct MethodDebugInfo;
34}  // namespace debug
35
36namespace linker {
37
38class LinkerPatch;
39class OutputStream;
40
41/**
42 * @class RelativePatcherTargetProvider
43 * @brief Interface for providing method offsets for relative call targets.
44 */
45class RelativePatcherTargetProvider {
46 public:
47  /**
48   * Find the offset of the target method of a relative call if known.
49   *
50   * The process of assigning target method offsets includes calls to the relative patcher's
51   * ReserveSpace() which in turn can use FindMethodOffset() to determine if a method already
52   * has an offset assigned and, if so, what's that offset. If the offset has not yet been
53   * assigned or if it's too far for the particular architecture's relative call,
54   * ReserveSpace() may need to allocate space for a special dispatch thunk.
55   *
56   * @param ref the target method of the relative call.
57   * @return true in the first element of the pair if the method was found, false otherwise;
58   *         if found, the second element specifies the offset.
59   */
60  virtual std::pair<bool, uint32_t> FindMethodOffset(MethodReference ref) = 0;
61
62 protected:
63  virtual ~RelativePatcherTargetProvider() { }
64};
65
66/**
67 * @class RelativePatcher
68 * @brief Interface for architecture-specific link-time patching of PC-relative references.
69 */
70class RelativePatcher {
71 public:
72  static std::unique_ptr<RelativePatcher> Create(
73      InstructionSet instruction_set, const InstructionSetFeatures* features,
74      RelativePatcherTargetProvider* provider);
75
76  virtual ~RelativePatcher() { }
77
78  uint32_t CodeAlignmentSize() const {
79    return size_code_alignment_;
80  }
81
82  uint32_t RelativeCallThunksSize() const {
83    return size_relative_call_thunks_;
84  }
85
86  uint32_t MiscThunksSize() const {
87    return size_misc_thunks_;
88  }
89
90  // Reserve space for thunks if needed before a method, return adjusted offset.
91  virtual uint32_t ReserveSpace(uint32_t offset,
92                                const CompiledMethod* compiled_method,
93                                MethodReference method_ref) = 0;
94
95  // Reserve space for thunks if needed after the last method, return adjusted offset.
96  // The caller may use this method to preemptively force thunk space reservation and
97  // then resume reservation for more methods. This is useful when there is a gap in
98  // the .text segment, for example when going to the next oat file for multi-image.
99  virtual uint32_t ReserveSpaceEnd(uint32_t offset) = 0;
100
101  // Write relative call thunks if needed, return adjusted offset. Returns 0 on write failure.
102  virtual uint32_t WriteThunks(OutputStream* out, uint32_t offset) = 0;
103
104  // Patch method code. The input displacement is relative to the patched location,
105  // the patcher may need to adjust it if the correct base is different.
106  virtual void PatchCall(std::vector<uint8_t>* code,
107                         uint32_t literal_offset,
108                         uint32_t patch_offset,
109                         uint32_t target_offset) = 0;
110
111  // Patch a reference to a dex cache location.
112  virtual void PatchPcRelativeReference(std::vector<uint8_t>* code,
113                                        const LinkerPatch& patch,
114                                        uint32_t patch_offset,
115                                        uint32_t target_offset) = 0;
116
117  // Patch a branch to a Baker read barrier thunk.
118  virtual void PatchBakerReadBarrierBranch(std::vector<uint8_t>* code,
119                                           const LinkerPatch& patch,
120                                           uint32_t patch_offset) = 0;
121
122  virtual std::vector<debug::MethodDebugInfo> GenerateThunkDebugInfo(
123      uint32_t executable_offset) = 0;
124
125 protected:
126  RelativePatcher()
127      : size_code_alignment_(0u),
128        size_relative_call_thunks_(0u),
129        size_misc_thunks_(0u) {
130  }
131
132  bool WriteCodeAlignment(OutputStream* out, uint32_t aligned_code_delta);
133  bool WriteThunk(OutputStream* out, const ArrayRef<const uint8_t>& thunk);
134  bool WriteMiscThunk(OutputStream* out, const ArrayRef<const uint8_t>& thunk);
135
136 private:
137  uint32_t size_code_alignment_;
138  uint32_t size_relative_call_thunks_;
139  uint32_t size_misc_thunks_;
140
141  DISALLOW_COPY_AND_ASSIGN(RelativePatcher);
142};
143
144}  // namespace linker
145}  // namespace art
146
147#endif  // ART_COMPILER_LINKER_RELATIVE_PATCHER_H_
148