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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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "linker/x86/relative_patcher_x86.h"
#include "compiled_method.h"
namespace art {
namespace linker {
void X86RelativePatcher::PatchDexCacheReference(std::vector<uint8_t>* code,
const LinkerPatch& patch,
uint32_t patch_offset,
uint32_t target_offset) {
uint32_t anchor_literal_offset = patch.PcInsnOffset();
uint32_t literal_offset = patch.LiteralOffset();
// Check that the anchor points to pop in a "call +0; pop <reg>" sequence.
DCHECK_GE(anchor_literal_offset, 5u);
DCHECK_LT(anchor_literal_offset, code->size());
DCHECK_EQ((*code)[anchor_literal_offset - 5u], 0xe8u);
DCHECK_EQ((*code)[anchor_literal_offset - 4u], 0x00u);
DCHECK_EQ((*code)[anchor_literal_offset - 3u], 0x00u);
DCHECK_EQ((*code)[anchor_literal_offset - 2u], 0x00u);
DCHECK_EQ((*code)[anchor_literal_offset - 1u], 0x00u);
DCHECK_EQ((*code)[anchor_literal_offset] & 0xf8u, 0x58u);
// Check that the patched data contains kDummy32BitOffset.
constexpr int kDummy32BitOffset = 256; // Must match X86Mir2Lir::kDummy32BitOffset.
DCHECK_LE(literal_offset, code->size());
DCHECK_EQ((*code)[literal_offset + 0u], static_cast<uint8_t>(kDummy32BitOffset >> 0));
DCHECK_EQ((*code)[literal_offset + 1u], static_cast<uint8_t>(kDummy32BitOffset >> 8));
DCHECK_EQ((*code)[literal_offset + 2u], static_cast<uint8_t>(kDummy32BitOffset >> 16));
DCHECK_EQ((*code)[literal_offset + 3u], static_cast<uint8_t>(kDummy32BitOffset >> 24));
// Apply patch.
uint32_t anchor_offset = patch_offset - literal_offset + anchor_literal_offset;
uint32_t diff = target_offset - anchor_offset;
(*code)[literal_offset + 0u] = static_cast<uint8_t>(diff >> 0);
(*code)[literal_offset + 1u] = static_cast<uint8_t>(diff >> 8);
(*code)[literal_offset + 2u] = static_cast<uint8_t>(diff >> 16);
(*code)[literal_offset + 3u] = static_cast<uint8_t>(diff >> 24);
}
} // namespace linker
} // namespace art
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