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
26 // PC displacement from patch location; Thumb2 PC is always at instruction address + 4.
27 static constexpr int32_t kPcDisplacement = 4;
28
29 // Maximum positive and negative displacement for method call measured from the patch location.
30 // (Signed 25 bit displacement with the last bit 0 has range [-2^24, 2^24-2] measured from
31 // the Thumb2 PC pointing right after the BL, i.e. 4 bytes later than the patch location.)
32 constexpr uint32_t kMaxMethodCallPositiveDisplacement = (1u << 24) - 2 + kPcDisplacement;
33 constexpr uint32_t kMaxMethodCallNegativeDisplacement = (1u << 24) - kPcDisplacement;
34
Thumb2RelativePatcher(RelativePatcherTargetProvider * provider)35 Thumb2RelativePatcher::Thumb2RelativePatcher(RelativePatcherTargetProvider* provider)
36 : ArmBaseRelativePatcher(provider, kThumb2) {
37 }
38
PatchCall(std::vector<uint8_t> * code,uint32_t literal_offset,uint32_t patch_offset,uint32_t target_offset)39 void Thumb2RelativePatcher::PatchCall(std::vector<uint8_t>* code,
40 uint32_t literal_offset,
41 uint32_t patch_offset,
42 uint32_t target_offset) {
43 DCHECK_LE(literal_offset + 4u, code->size());
44 DCHECK_EQ(literal_offset & 1u, 0u);
45 DCHECK_EQ(patch_offset & 1u, 0u);
46 DCHECK_EQ(target_offset & 1u, 1u); // Thumb2 mode bit.
47 uint32_t displacement = CalculateMethodCallDisplacement(patch_offset, target_offset & ~1u);
48 displacement -= kPcDisplacement; // The base PC is at the end of the 4-byte patch.
49 DCHECK_EQ(displacement & 1u, 0u);
50 DCHECK((displacement >> 24) == 0u || (displacement >> 24) == 255u); // 25-bit signed.
51 uint32_t signbit = (displacement >> 31) & 0x1;
52 uint32_t i1 = (displacement >> 23) & 0x1;
53 uint32_t i2 = (displacement >> 22) & 0x1;
54 uint32_t imm10 = (displacement >> 12) & 0x03ff;
55 uint32_t imm11 = (displacement >> 1) & 0x07ff;
56 uint32_t j1 = i1 ^ (signbit ^ 1);
57 uint32_t j2 = i2 ^ (signbit ^ 1);
58 uint32_t value = (signbit << 26) | (j1 << 13) | (j2 << 11) | (imm10 << 16) | imm11;
59 value |= 0xf000d000; // BL
60
61 // Check that we're just overwriting an existing BL.
62 DCHECK_EQ(GetInsn32(code, literal_offset) & 0xf800d000, 0xf000d000);
63 // Write the new BL.
64 SetInsn32(code, literal_offset, value);
65 }
66
PatchPcRelativeReference(std::vector<uint8_t> * code,const LinkerPatch & patch,uint32_t patch_offset,uint32_t target_offset)67 void Thumb2RelativePatcher::PatchPcRelativeReference(std::vector<uint8_t>* code,
68 const LinkerPatch& patch,
69 uint32_t patch_offset,
70 uint32_t target_offset) {
71 uint32_t literal_offset = patch.LiteralOffset();
72 uint32_t pc_literal_offset = patch.PcInsnOffset();
73 uint32_t pc_base = patch_offset + (pc_literal_offset - literal_offset) + 4u /* PC adjustment */;
74 uint32_t diff = target_offset - pc_base;
75
76 uint32_t insn = GetInsn32(code, literal_offset);
77 DCHECK_EQ(insn & 0xff7ff0ffu, 0xf2400000u); // MOVW/MOVT, unpatched (imm16 == 0).
78 uint32_t diff16 = ((insn & 0x00800000u) != 0u) ? (diff >> 16) : (diff & 0xffffu);
79 uint32_t imm4 = (diff16 >> 12) & 0xfu;
80 uint32_t imm = (diff16 >> 11) & 0x1u;
81 uint32_t imm3 = (diff16 >> 8) & 0x7u;
82 uint32_t imm8 = diff16 & 0xffu;
83 insn = (insn & 0xfbf08f00u) | (imm << 26) | (imm4 << 16) | (imm3 << 12) | imm8;
84 SetInsn32(code, literal_offset, insn);
85 }
86
PatchBakerReadBarrierBranch(std::vector<uint8_t> * code ATTRIBUTE_UNUSED,const LinkerPatch & patch ATTRIBUTE_UNUSED,uint32_t patch_offset ATTRIBUTE_UNUSED)87 void Thumb2RelativePatcher::PatchBakerReadBarrierBranch(std::vector<uint8_t>* code ATTRIBUTE_UNUSED,
88 const LinkerPatch& patch ATTRIBUTE_UNUSED,
89 uint32_t patch_offset ATTRIBUTE_UNUSED) {
90 LOG(FATAL) << "UNIMPLEMENTED";
91 }
92
GetBakerReadBarrierKey(const LinkerPatch & patch ATTRIBUTE_UNUSED)93 ArmBaseRelativePatcher::ThunkKey Thumb2RelativePatcher::GetBakerReadBarrierKey(
94 const LinkerPatch& patch ATTRIBUTE_UNUSED) {
95 LOG(FATAL) << "UNIMPLEMENTED";
96 UNREACHABLE();
97 }
98
CompileThunk(const ThunkKey & key)99 std::vector<uint8_t> Thumb2RelativePatcher::CompileThunk(const ThunkKey& key) {
100 DCHECK(key.GetType() == ThunkType::kMethodCall);
101 // The thunk just uses the entry point in the ArtMethod. This works even for calls
102 // to the generic JNI and interpreter trampolines.
103 ArenaPool pool;
104 ArenaAllocator arena(&pool);
105 arm::Thumb2Assembler assembler(&arena);
106 assembler.LoadFromOffset(
107 arm::kLoadWord, arm::PC, arm::R0,
108 ArtMethod::EntryPointFromQuickCompiledCodeOffset(kArmPointerSize).Int32Value());
109 assembler.bkpt(0);
110 assembler.FinalizeCode();
111 std::vector<uint8_t> thunk_code(assembler.CodeSize());
112 MemoryRegion code(thunk_code.data(), thunk_code.size());
113 assembler.FinalizeInstructions(code);
114 return thunk_code;
115 }
116
MaxPositiveDisplacement(ThunkType type)117 uint32_t Thumb2RelativePatcher::MaxPositiveDisplacement(ThunkType type) {
118 DCHECK(type == ThunkType::kMethodCall);
119 return kMaxMethodCallPositiveDisplacement;
120 }
121
MaxNegativeDisplacement(ThunkType type)122 uint32_t Thumb2RelativePatcher::MaxNegativeDisplacement(ThunkType type) {
123 DCHECK(type == ThunkType::kMethodCall);
124 return kMaxMethodCallNegativeDisplacement;
125 }
126
SetInsn32(std::vector<uint8_t> * code,uint32_t offset,uint32_t value)127 void Thumb2RelativePatcher::SetInsn32(std::vector<uint8_t>* code, uint32_t offset, uint32_t value) {
128 DCHECK_LE(offset + 4u, code->size());
129 DCHECK_EQ(offset & 1u, 0u);
130 uint8_t* addr = &(*code)[offset];
131 addr[0] = (value >> 16) & 0xff;
132 addr[1] = (value >> 24) & 0xff;
133 addr[2] = (value >> 0) & 0xff;
134 addr[3] = (value >> 8) & 0xff;
135 }
136
GetInsn32(ArrayRef<const uint8_t> code,uint32_t offset)137 uint32_t Thumb2RelativePatcher::GetInsn32(ArrayRef<const uint8_t> code, uint32_t offset) {
138 DCHECK_LE(offset + 4u, code.size());
139 DCHECK_EQ(offset & 1u, 0u);
140 const uint8_t* addr = &code[offset];
141 return
142 (static_cast<uint32_t>(addr[0]) << 16) +
143 (static_cast<uint32_t>(addr[1]) << 24) +
144 (static_cast<uint32_t>(addr[2]) << 0)+
145 (static_cast<uint32_t>(addr[3]) << 8);
146 }
147
148 template <typename Vector>
GetInsn32(Vector * code,uint32_t offset)149 uint32_t Thumb2RelativePatcher::GetInsn32(Vector* code, uint32_t offset) {
150 static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
151 return GetInsn32(ArrayRef<const uint8_t>(*code), offset);
152 }
153
154 } // namespace linker
155 } // namespace art
156