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 "compiled_method.h" 20 21 namespace art { 22 namespace linker { 23 24 void X86RelativePatcher::PatchDexCacheReference(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 kDummy32BitOffset. 42 constexpr int kDummy32BitOffset = 256; // Must match X86Mir2Lir::kDummy32BitOffset. 43 DCHECK_LE(literal_offset, code->size()); 44 DCHECK_EQ((*code)[literal_offset + 0u], static_cast<uint8_t>(kDummy32BitOffset >> 0)); 45 DCHECK_EQ((*code)[literal_offset + 1u], static_cast<uint8_t>(kDummy32BitOffset >> 8)); 46 DCHECK_EQ((*code)[literal_offset + 2u], static_cast<uint8_t>(kDummy32BitOffset >> 16)); 47 DCHECK_EQ((*code)[literal_offset + 3u], static_cast<uint8_t>(kDummy32BitOffset >> 24)); 48 49 // Apply patch. 50 uint32_t anchor_offset = patch_offset - literal_offset + anchor_literal_offset; 51 uint32_t diff = target_offset - anchor_offset; 52 (*code)[literal_offset + 0u] = static_cast<uint8_t>(diff >> 0); 53 (*code)[literal_offset + 1u] = static_cast<uint8_t>(diff >> 8); 54 (*code)[literal_offset + 2u] = static_cast<uint8_t>(diff >> 16); 55 (*code)[literal_offset + 3u] = static_cast<uint8_t>(diff >> 24); 56 } 57 58 } // namespace linker 59 } // namespace art 60
