1 /*
2 * Copyright (C) 2017 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 <stdint.h>
18
19 #include <unwindstack/DwarfError.h>
20 #include <unwindstack/DwarfStructs.h>
21 #include <unwindstack/Elf.h>
22 #include <unwindstack/ElfInterface.h>
23 #include <unwindstack/Memory.h>
24
25 #include "Check.h"
26 #include "DwarfEhFrameWithHdr.h"
27 #include "DwarfEncoding.h"
28
29 namespace unwindstack {
30
IsEncodingRelative(uint8_t encoding)31 static inline bool IsEncodingRelative(uint8_t encoding) {
32 encoding >>= 4;
33 return encoding > 0 && encoding <= DW_EH_PE_funcrel;
34 }
35
36 template <typename AddressType>
EhFrameInit(const SectionInfo & info)37 bool DwarfEhFrameWithHdr<AddressType>::EhFrameInit(const SectionInfo& info) {
38 return DwarfSectionImpl<AddressType>::Init(info);
39 }
40
41 template <typename AddressType>
Init(const SectionInfo & info)42 bool DwarfEhFrameWithHdr<AddressType>::Init(const SectionInfo& info) {
43 if (info.flags & SHF_COMPRESSED) {
44 return false;
45 }
46
47 memory_.clear_func_offset();
48 memory_.clear_text_offset();
49 memory_.set_data_offset(info.offset);
50 memory_.set_cur_offset(info.offset);
51
52 hdr_section_bias_ = info.bias;
53
54 // Read the first four bytes all at once.
55 uint8_t data[4];
56 if (!memory_.ReadBytes(data, 4)) {
57 last_error_.code = DWARF_ERROR_MEMORY_INVALID;
58 last_error_.address = memory_.cur_offset();
59 return false;
60 }
61
62 version_ = data[0];
63 if (version_ != 1) {
64 // Unknown version.
65 last_error_.code = DWARF_ERROR_UNSUPPORTED_VERSION;
66 return false;
67 }
68
69 uint8_t ptr_encoding = data[1];
70 uint8_t fde_count_encoding = data[2];
71 table_encoding_ = data[3];
72 table_entry_size_ = memory_.template GetEncodedSize<AddressType>(table_encoding_);
73
74 // If we can't perform a binary search on the entries, it's not worth
75 // using this object. The calling code will fall back to the DwarfEhFrame
76 // object in this case.
77 if (table_entry_size_ == 0) {
78 last_error_.code = DWARF_ERROR_ILLEGAL_VALUE;
79 return false;
80 }
81
82 memory_.set_pc_offset(memory_.cur_offset());
83 uint64_t ptr_offset;
84 if (!memory_.template ReadEncodedValue<AddressType>(ptr_encoding, &ptr_offset)) {
85 last_error_.code = DWARF_ERROR_MEMORY_INVALID;
86 last_error_.address = memory_.cur_offset();
87 return false;
88 }
89
90 memory_.set_pc_offset(memory_.cur_offset());
91 if (!memory_.template ReadEncodedValue<AddressType>(fde_count_encoding, &fde_count_)) {
92 last_error_.code = DWARF_ERROR_MEMORY_INVALID;
93 last_error_.address = memory_.cur_offset();
94 return false;
95 }
96
97 if (fde_count_ == 0) {
98 last_error_.code = DWARF_ERROR_NO_FDES;
99 return false;
100 }
101
102 hdr_entries_offset_ = memory_.cur_offset();
103 hdr_entries_data_offset_ = info.offset;
104
105 return true;
106 }
107
108 template <typename AddressType>
GetFdeFromPc(uint64_t pc)109 const DwarfFde* DwarfEhFrameWithHdr<AddressType>::GetFdeFromPc(uint64_t pc) {
110 uint64_t fde_offset;
111 if (!GetFdeOffsetFromPc(pc, &fde_offset)) {
112 return nullptr;
113 }
114 const DwarfFde* fde = this->GetFdeFromOffset(fde_offset);
115 if (fde == nullptr) {
116 return nullptr;
117 }
118
119 // There is a possibility that this entry points to a zero length FDE
120 // due to a bug. If this happens, try and find the non-zero length FDE
121 // from eh_frame directly. See b/142483624.
122 if (fde->pc_start == fde->pc_end) {
123 fde = DwarfSectionImpl<AddressType>::GetFdeFromPc(pc);
124 if (fde == nullptr) {
125 return nullptr;
126 }
127 }
128
129 // Guaranteed pc >= pc_start, need to check pc in the fde range.
130 if (pc < fde->pc_end) {
131 return fde;
132 }
133 last_error_.code = DWARF_ERROR_ILLEGAL_STATE;
134 return nullptr;
135 }
136
137 template <typename AddressType>
138 const typename DwarfEhFrameWithHdr<AddressType>::FdeInfo*
GetFdeInfoFromIndex(size_t index)139 DwarfEhFrameWithHdr<AddressType>::GetFdeInfoFromIndex(size_t index) {
140 auto entry = fde_info_.find(index);
141 if (entry != fde_info_.end()) {
142 return &fde_info_[index];
143 }
144 FdeInfo* info = &fde_info_[index];
145
146 memory_.set_data_offset(hdr_entries_data_offset_);
147 memory_.set_cur_offset(hdr_entries_offset_ + 2 * index * table_entry_size_);
148 memory_.set_pc_offset(0);
149 uint64_t value;
150 if (!memory_.template ReadEncodedValue<AddressType>(table_encoding_, &value) ||
151 !memory_.template ReadEncodedValue<AddressType>(table_encoding_, &info->offset)) {
152 last_error_.code = DWARF_ERROR_MEMORY_INVALID;
153 last_error_.address = memory_.cur_offset();
154 fde_info_.erase(index);
155 return nullptr;
156 }
157
158 // Relative encodings require adding in the load bias.
159 if (IsEncodingRelative(table_encoding_)) {
160 value += hdr_section_bias_;
161 }
162 info->pc = value;
163 return info;
164 }
165
166 template <typename AddressType>
GetFdeOffsetFromPc(uint64_t pc,uint64_t * fde_offset)167 bool DwarfEhFrameWithHdr<AddressType>::GetFdeOffsetFromPc(uint64_t pc, uint64_t* fde_offset) {
168 if (fde_count_ == 0) {
169 return false;
170 }
171
172 size_t first = 0;
173 size_t last = fde_count_;
174 while (first < last) {
175 size_t current = (first + last) / 2;
176 const FdeInfo* info = GetFdeInfoFromIndex(current);
177 if (info == nullptr) {
178 return false;
179 }
180 if (pc == info->pc) {
181 *fde_offset = info->offset;
182 return true;
183 }
184 if (pc < info->pc) {
185 last = current;
186 } else {
187 first = current + 1;
188 }
189 }
190 if (last != 0) {
191 const FdeInfo* info = GetFdeInfoFromIndex(last - 1);
192 if (info == nullptr) {
193 return false;
194 }
195 *fde_offset = info->offset;
196 return true;
197 }
198 return false;
199 }
200
201 template <typename AddressType>
GetFdes(std::vector<const DwarfFde * > * fdes)202 void DwarfEhFrameWithHdr<AddressType>::GetFdes(std::vector<const DwarfFde*>* fdes) {
203 for (size_t i = 0; i < fde_count_; i++) {
204 const FdeInfo* info = GetFdeInfoFromIndex(i);
205 if (info == nullptr) {
206 break;
207 }
208 const DwarfFde* fde = this->GetFdeFromOffset(info->offset);
209 if (fde == nullptr) {
210 break;
211 }
212
213 // There is a possibility that this entry points to a zero length FDE
214 // due to a bug. If this happens, try and find the non-zero length FDE
215 // from eh_frame directly. See b/142483624.
216 if (fde->pc_start == fde->pc_end) {
217 const DwarfFde* fde_real = DwarfSectionImpl<AddressType>::GetFdeFromPc(fde->pc_start);
218 if (fde_real != nullptr) {
219 fde = fde_real;
220 }
221 }
222 fdes->push_back(fde);
223 }
224 }
225
226 // Explicitly instantiate DwarfEhFrameWithHdr
227 template class DwarfEhFrameWithHdr<uint32_t>;
228 template class DwarfEhFrameWithHdr<uint64_t>;
229
230 } // namespace unwindstack
231