1 /*
2 * Copyright (C) 2016 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 <elf.h>
18 #include <stdint.h>
19
20 #include <unwindstack/MachineArm.h>
21 #include <unwindstack/Memory.h>
22 #include <unwindstack/RegsArm.h>
23
24 #include "ArmExidx.h"
25 #include "ElfInterfaceArm.h"
26
27 namespace unwindstack {
28
FindEntry(uint32_t pc,uint64_t * entry_offset)29 bool ElfInterfaceArm::FindEntry(uint32_t pc, uint64_t* entry_offset) {
30 if (start_offset_ == 0 || total_entries_ == 0) {
31 last_error_.code = ERROR_UNWIND_INFO;
32 return false;
33 }
34
35 size_t first = 0;
36 size_t last = total_entries_;
37 while (first < last) {
38 size_t current = (first + last) / 2;
39 uint32_t addr = addrs_[current];
40 if (addr == 0) {
41 if (!GetPrel31Addr(start_offset_ + current * 8, &addr)) {
42 return false;
43 }
44 addrs_[current] = addr;
45 }
46 if (pc == addr) {
47 *entry_offset = start_offset_ + current * 8;
48 return true;
49 }
50 if (pc < addr) {
51 last = current;
52 } else {
53 first = current + 1;
54 }
55 }
56 if (last != 0) {
57 *entry_offset = start_offset_ + (last - 1) * 8;
58 return true;
59 }
60 last_error_.code = ERROR_UNWIND_INFO;
61 return false;
62 }
63
GetPrel31Addr(uint32_t offset,uint32_t * addr)64 bool ElfInterfaceArm::GetPrel31Addr(uint32_t offset, uint32_t* addr) {
65 uint32_t data;
66 if (!memory_->Read32(offset, &data)) {
67 last_error_.code = ERROR_MEMORY_INVALID;
68 last_error_.address = offset;
69 return false;
70 }
71
72 // Sign extend the value if necessary.
73 int32_t value = (static_cast<int32_t>(data) << 1) >> 1;
74 *addr = offset + value;
75 return true;
76 }
77
78 #if !defined(PT_ARM_EXIDX)
79 #define PT_ARM_EXIDX 0x70000001
80 #endif
81
HandleType(uint64_t offset,uint32_t type,uint64_t load_bias)82 bool ElfInterfaceArm::HandleType(uint64_t offset, uint32_t type, uint64_t load_bias) {
83 if (type != PT_ARM_EXIDX) {
84 return false;
85 }
86
87 Elf32_Phdr phdr;
88 if (!memory_->ReadField(offset, &phdr, &phdr.p_vaddr, sizeof(phdr.p_vaddr))) {
89 return true;
90 }
91 if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
92 return true;
93 }
94 start_offset_ = phdr.p_vaddr - load_bias;
95 total_entries_ = phdr.p_memsz / 8;
96 return true;
97 }
98
Step(uint64_t pc,uint64_t load_bias,Regs * regs,Memory * process_memory,bool * finished)99 bool ElfInterfaceArm::Step(uint64_t pc, uint64_t load_bias, Regs* regs, Memory* process_memory,
100 bool* finished) {
101 // Dwarf unwind information is precise about whether a pc is covered or not,
102 // but arm unwind information only has ranges of pc. In order to avoid
103 // incorrectly doing a bad unwind using arm unwind information for a
104 // different function, always try and unwind with the dwarf information first.
105 return ElfInterface32::Step(pc, load_bias, regs, process_memory, finished) ||
106 StepExidx(pc, load_bias, regs, process_memory, finished);
107 }
108
StepExidx(uint64_t pc,uint64_t load_bias,Regs * regs,Memory * process_memory,bool * finished)109 bool ElfInterfaceArm::StepExidx(uint64_t pc, uint64_t load_bias, Regs* regs, Memory* process_memory,
110 bool* finished) {
111 // Adjust the load bias to get the real relative pc.
112 if (pc < load_bias) {
113 last_error_.code = ERROR_UNWIND_INFO;
114 return false;
115 }
116 pc -= load_bias;
117
118 RegsArm* regs_arm = reinterpret_cast<RegsArm*>(regs);
119 uint64_t entry_offset;
120 if (!FindEntry(pc, &entry_offset)) {
121 return false;
122 }
123
124 ArmExidx arm(regs_arm, memory_, process_memory);
125 arm.set_cfa(regs_arm->sp());
126 bool return_value = false;
127 if (arm.ExtractEntryData(entry_offset) && arm.Eval()) {
128 // If the pc was not set, then use the LR registers for the PC.
129 if (!arm.pc_set()) {
130 (*regs_arm)[ARM_REG_PC] = (*regs_arm)[ARM_REG_LR];
131 }
132 (*regs_arm)[ARM_REG_SP] = arm.cfa();
133 return_value = true;
134
135 // If the pc was set to zero, consider this the final frame.
136 *finished = (regs_arm->pc() == 0) ? true : false;
137 }
138
139 if (arm.status() == ARM_STATUS_NO_UNWIND) {
140 *finished = true;
141 return true;
142 }
143
144 if (!return_value) {
145 switch (arm.status()) {
146 case ARM_STATUS_NONE:
147 case ARM_STATUS_NO_UNWIND:
148 case ARM_STATUS_FINISH:
149 last_error_.code = ERROR_NONE;
150 break;
151
152 case ARM_STATUS_RESERVED:
153 case ARM_STATUS_SPARE:
154 case ARM_STATUS_TRUNCATED:
155 case ARM_STATUS_MALFORMED:
156 case ARM_STATUS_INVALID_ALIGNMENT:
157 case ARM_STATUS_INVALID_PERSONALITY:
158 last_error_.code = ERROR_UNWIND_INFO;
159 break;
160
161 case ARM_STATUS_READ_FAILED:
162 last_error_.code = ERROR_MEMORY_INVALID;
163 last_error_.address = arm.status_address();
164 break;
165 }
166 }
167 return return_value;
168 }
169
GetFunctionName(uint64_t addr,uint64_t load_bias,std::string * name,uint64_t * offset)170 bool ElfInterfaceArm::GetFunctionName(uint64_t addr, uint64_t load_bias, std::string* name,
171 uint64_t* offset) {
172 // For ARM, thumb function symbols have bit 0 set, but the address passed
173 // in here might not have this bit set and result in a failure to find
174 // the thumb function names. Adjust the address and offset to account
175 // for this possible case.
176 if (ElfInterface32::GetFunctionName(addr | 1, load_bias, name, offset)) {
177 *offset &= ~1;
178 return true;
179 }
180 return false;
181 }
182
183 } // namespace unwindstack
184