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
33bool 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
52bool 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
69ElfInterface* 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