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 <string.h>
19
20 #include <memory>
21 #include <string>
22
23 #define LOG_TAG "unwind"
24 #include <log/log.h>
25
26 #include "Elf.h"
27 #include "ElfInterface.h"
28 #include "ElfInterfaceArm.h"
29 #include "Machine.h"
30 #include "Memory.h"
31 #include "Regs.h"
32
Init()33 bool Elf::Init() {
34 if (!memory_) {
35 return false;
36 }
37
38 interface_.reset(CreateInterfaceFromMemory(memory_.get()));
39 if (!interface_) {
40 return false;
41 }
42
43 valid_ = interface_->Init();
44 if (valid_) {
45 interface_->InitHeaders();
46 } else {
47 interface_.reset(nullptr);
48 }
49 return valid_;
50 }
51
IsValidElf(Memory * memory)52 bool Elf::IsValidElf(Memory* memory) {
53 if (memory == nullptr) {
54 return false;
55 }
56
57 // Verify that this is a valid elf file.
58 uint8_t e_ident[SELFMAG + 1];
59 if (!memory->Read(0, e_ident, SELFMAG)) {
60 return false;
61 }
62
63 if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
64 return false;
65 }
66 return true;
67 }
68
CreateInterfaceFromMemory(Memory * memory)69 ElfInterface* Elf::CreateInterfaceFromMemory(Memory* memory) {
70 if (!IsValidElf(memory)) {
71 return nullptr;
72 }
73
74 std::unique_ptr<ElfInterface> interface;
75 if (!memory->Read(EI_CLASS, &class_type_, 1)) {
76 return nullptr;
77 }
78 if (class_type_ == ELFCLASS32) {
79 Elf32_Half e_machine;
80 if (!memory->Read(EI_NIDENT + sizeof(Elf32_Half), &e_machine, sizeof(e_machine))) {
81 return nullptr;
82 }
83
84 if (e_machine != EM_ARM && e_machine != EM_386) {
85 // Unsupported.
86 ALOGI("32 bit elf that is neither arm nor x86: e_machine = %d\n", e_machine);
87 return nullptr;
88 }
89
90 machine_type_ = e_machine;
91 if (e_machine == EM_ARM) {
92 interface.reset(new ElfInterfaceArm(memory));
93 } else {
94 interface.reset(new ElfInterface32(memory));
95 }
96 } else if (class_type_ == ELFCLASS64) {
97 Elf64_Half e_machine;
98 if (!memory->Read(EI_NIDENT + sizeof(Elf64_Half), &e_machine, sizeof(e_machine))) {
99 return nullptr;
100 }
101
102 if (e_machine != EM_AARCH64 && e_machine != EM_X86_64) {
103 // Unsupported.
104 ALOGI("64 bit elf that is neither aarch64 nor x86_64: e_machine = %d\n", e_machine);
105 return nullptr;
106 }
107
108 machine_type_ = e_machine;
109 interface.reset(new ElfInterface64(memory));
110 }
111
112 return interface.release();
113 }
114