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/arm/relative_patcher_thumb2.h"
18
19 #include "art_method.h"
20 #include "compiled_method.h"
21 #include "utils/arm/assembler_thumb2.h"
22
23 namespace art {
24 namespace linker {
25
Thumb2RelativePatcher(RelativePatcherTargetProvider * provider)26 Thumb2RelativePatcher::Thumb2RelativePatcher(RelativePatcherTargetProvider* provider)
27 : ArmBaseRelativePatcher(provider, kThumb2, CompileThunkCode(),
28 kMaxPositiveDisplacement, kMaxNegativeDisplacement) {
29 }
30
PatchCall(std::vector<uint8_t> * code,uint32_t literal_offset,uint32_t patch_offset,uint32_t target_offset)31 void Thumb2RelativePatcher::PatchCall(std::vector<uint8_t>* code,
32 uint32_t literal_offset,
33 uint32_t patch_offset,
34 uint32_t target_offset) {
35 DCHECK_LE(literal_offset + 4u, code->size());
36 DCHECK_EQ(literal_offset & 1u, 0u);
37 DCHECK_EQ(patch_offset & 1u, 0u);
38 DCHECK_EQ(target_offset & 1u, 1u); // Thumb2 mode bit.
39 uint32_t displacement = CalculateDisplacement(patch_offset, target_offset & ~1u);
40 displacement -= kPcDisplacement; // The base PC is at the end of the 4-byte patch.
41 DCHECK_EQ(displacement & 1u, 0u);
42 DCHECK((displacement >> 24) == 0u || (displacement >> 24) == 255u); // 25-bit signed.
43 uint32_t signbit = (displacement >> 31) & 0x1;
44 uint32_t i1 = (displacement >> 23) & 0x1;
45 uint32_t i2 = (displacement >> 22) & 0x1;
46 uint32_t imm10 = (displacement >> 12) & 0x03ff;
47 uint32_t imm11 = (displacement >> 1) & 0x07ff;
48 uint32_t j1 = i1 ^ (signbit ^ 1);
49 uint32_t j2 = i2 ^ (signbit ^ 1);
50 uint32_t value = (signbit << 26) | (j1 << 13) | (j2 << 11) | (imm10 << 16) | imm11;
51 value |= 0xf000d000; // BL
52
53 // Check that we're just overwriting an existing BL.
54 DCHECK_EQ(GetInsn32(code, literal_offset) & 0xf800d000, 0xf000d000);
55 // Write the new BL.
56 SetInsn32(code, literal_offset, value);
57 }
58
PatchPcRelativeReference(std::vector<uint8_t> * code,const LinkerPatch & patch,uint32_t patch_offset,uint32_t target_offset)59 void Thumb2RelativePatcher::PatchPcRelativeReference(std::vector<uint8_t>* code,
60 const LinkerPatch& patch,
61 uint32_t patch_offset,
62 uint32_t target_offset) {
63 uint32_t literal_offset = patch.LiteralOffset();
64 uint32_t pc_literal_offset = patch.PcInsnOffset();
65 uint32_t pc_base = patch_offset + (pc_literal_offset - literal_offset) + 4u /* PC adjustment */;
66 uint32_t diff = target_offset - pc_base;
67
68 uint32_t insn = GetInsn32(code, literal_offset);
69 DCHECK_EQ(insn & 0xff7ff0ffu, 0xf2400000u); // MOVW/MOVT, unpatched (imm16 == 0).
70 uint32_t diff16 = ((insn & 0x00800000u) != 0u) ? (diff >> 16) : (diff & 0xffffu);
71 uint32_t imm4 = (diff16 >> 12) & 0xfu;
72 uint32_t imm = (diff16 >> 11) & 0x1u;
73 uint32_t imm3 = (diff16 >> 8) & 0x7u;
74 uint32_t imm8 = diff16 & 0xffu;
75 insn = (insn & 0xfbf08f00u) | (imm << 26) | (imm4 << 16) | (imm3 << 12) | imm8;
76 SetInsn32(code, literal_offset, insn);
77 }
78
CompileThunkCode()79 std::vector<uint8_t> Thumb2RelativePatcher::CompileThunkCode() {
80 // The thunk just uses the entry point in the ArtMethod. This works even for calls
81 // to the generic JNI and interpreter trampolines.
82 ArenaPool pool;
83 ArenaAllocator arena(&pool);
84 arm::Thumb2Assembler assembler(&arena);
85 assembler.LoadFromOffset(
86 arm::kLoadWord, arm::PC, arm::R0,
87 ArtMethod::EntryPointFromQuickCompiledCodeOffset(kArmPointerSize).Int32Value());
88 assembler.bkpt(0);
89 assembler.FinalizeCode();
90 std::vector<uint8_t> thunk_code(assembler.CodeSize());
91 MemoryRegion code(thunk_code.data(), thunk_code.size());
92 assembler.FinalizeInstructions(code);
93 return thunk_code;
94 }
95
SetInsn32(std::vector<uint8_t> * code,uint32_t offset,uint32_t value)96 void Thumb2RelativePatcher::SetInsn32(std::vector<uint8_t>* code, uint32_t offset, uint32_t value) {
97 DCHECK_LE(offset + 4u, code->size());
98 DCHECK_EQ(offset & 1u, 0u);
99 uint8_t* addr = &(*code)[offset];
100 addr[0] = (value >> 16) & 0xff;
101 addr[1] = (value >> 24) & 0xff;
102 addr[2] = (value >> 0) & 0xff;
103 addr[3] = (value >> 8) & 0xff;
104 }
105
GetInsn32(ArrayRef<const uint8_t> code,uint32_t offset)106 uint32_t Thumb2RelativePatcher::GetInsn32(ArrayRef<const uint8_t> code, uint32_t offset) {
107 DCHECK_LE(offset + 4u, code.size());
108 DCHECK_EQ(offset & 1u, 0u);
109 const uint8_t* addr = &code[offset];
110 return
111 (static_cast<uint32_t>(addr[0]) << 16) +
112 (static_cast<uint32_t>(addr[1]) << 24) +
113 (static_cast<uint32_t>(addr[2]) << 0)+
114 (static_cast<uint32_t>(addr[3]) << 8);
115 }
116
117 template <typename Vector>
GetInsn32(Vector * code,uint32_t offset)118 uint32_t Thumb2RelativePatcher::GetInsn32(Vector* code, uint32_t offset) {
119 static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
120 return GetInsn32(ArrayRef<const uint8_t>(*code), offset);
121 }
122
123 } // namespace linker
124 } // namespace art
125