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* Copyright (C) 2015 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <vector>
#include "arch/instruction_set.h"
#include "arch/instruction_set_features.h"
#include "base/macros.h"
#include "method_reference.h"
#include "utils/array_ref.h"
namespace art {
class CompiledMethod;
class LinkerPatch;
class OutputStream;
namespace linker {
* @class RelativePatcherTargetProvider
* @brief Interface for providing method offsets for relative call targets.
class RelativePatcherTargetProvider {
* Find the offset of the target method of a relative call if known.
* The process of assigning target method offsets includes calls to the relative patcher's
* ReserveSpace() which in turn can use FindMethodOffset() to determine if a method already
* has an offset assigned and, if so, what's that offset. If the offset has not yet been
* assigned or if it's too far for the particular architecture's relative call,
* ReserveSpace() may need to allocate space for a special dispatch thunk.
* @param ref the target method of the relative call.
* @return true in the first element of the pair if the method was found, false otherwise;
* if found, the second element specifies the offset.
virtual std::pair<bool, uint32_t> FindMethodOffset(MethodReference ref) = 0;
virtual ~RelativePatcherTargetProvider() { }
* @class RelativePatcher
* @brief Interface for architecture-specific link-time patching of PC-relative references.
class RelativePatcher {
static std::unique_ptr<RelativePatcher> Create(
InstructionSet instruction_set, const InstructionSetFeatures* features,
RelativePatcherTargetProvider* provider);
virtual ~RelativePatcher() { }
uint32_t CodeAlignmentSize() const {
return size_code_alignment_;
uint32_t RelativeCallThunksSize() const {
return size_relative_call_thunks_;
uint32_t MiscThunksSize() const {
return size_misc_thunks_;
// Reserve space for thunks if needed before a method, return adjusted offset.
virtual uint32_t ReserveSpace(uint32_t offset,
const CompiledMethod* compiled_method,
MethodReference method_ref) = 0;
// Reserve space for thunks if needed after the last method, return adjusted offset.
// The caller may use this method to preemptively force thunk space reservation and
// then resume reservation for more methods. This is useful when there is a gap in
// the .text segment, for example when going to the next oat file for multi-image.
virtual uint32_t ReserveSpaceEnd(uint32_t offset) = 0;
// Write relative call thunks if needed, return adjusted offset. Returns 0 on write failure.
virtual uint32_t WriteThunks(OutputStream* out, uint32_t offset) = 0;
// Patch method code. The input displacement is relative to the patched location,
// the patcher may need to adjust it if the correct base is different.
virtual void PatchCall(std::vector<uint8_t>* code,
uint32_t literal_offset,
uint32_t patch_offset,
uint32_t target_offset) = 0;
// Patch a reference to a dex cache location.
virtual void PatchDexCacheReference(std::vector<uint8_t>* code,
const LinkerPatch& patch,
uint32_t patch_offset,
uint32_t target_offset) = 0;
: size_code_alignment_(0u),
size_misc_thunks_(0u) {
bool WriteCodeAlignment(OutputStream* out, uint32_t aligned_code_delta);
bool WriteRelCallThunk(OutputStream* out, const ArrayRef<const uint8_t>& thunk);
bool WriteMiscThunk(OutputStream* out, const ArrayRef<const uint8_t>& thunk);
uint32_t size_code_alignment_;
uint32_t size_relative_call_thunks_;
uint32_t size_misc_thunks_;
} // namespace linker
} // namespace art