1 //===-- ELFHeader.cpp -----------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include <cstring>
10
11 #include "lldb/Core/Section.h"
12 #include "lldb/Utility/DataExtractor.h"
13 #include "lldb/Utility/Stream.h"
14
15 #include "ELFHeader.h"
16
17 using namespace elf;
18 using namespace lldb;
19 using namespace llvm::ELF;
20
21 // Static utility functions.
22 //
23 // GetMaxU64 and GetMaxS64 wrap the similarly named methods from DataExtractor
24 // with error handling code and provide for parsing a sequence of values.
GetMaxU64(const lldb_private::DataExtractor & data,lldb::offset_t * offset,uint64_t * value,uint32_t byte_size)25 static bool GetMaxU64(const lldb_private::DataExtractor &data,
26 lldb::offset_t *offset, uint64_t *value,
27 uint32_t byte_size) {
28 const lldb::offset_t saved_offset = *offset;
29 *value = data.GetMaxU64(offset, byte_size);
30 return *offset != saved_offset;
31 }
32
GetMaxU64(const lldb_private::DataExtractor & data,lldb::offset_t * offset,uint64_t * value,uint32_t byte_size,uint32_t count)33 static bool GetMaxU64(const lldb_private::DataExtractor &data,
34 lldb::offset_t *offset, uint64_t *value,
35 uint32_t byte_size, uint32_t count) {
36 lldb::offset_t saved_offset = *offset;
37
38 for (uint32_t i = 0; i < count; ++i, ++value) {
39 if (!GetMaxU64(data, offset, value, byte_size)) {
40 *offset = saved_offset;
41 return false;
42 }
43 }
44 return true;
45 }
46
GetMaxS64(const lldb_private::DataExtractor & data,lldb::offset_t * offset,int64_t * value,uint32_t byte_size)47 static bool GetMaxS64(const lldb_private::DataExtractor &data,
48 lldb::offset_t *offset, int64_t *value,
49 uint32_t byte_size) {
50 const lldb::offset_t saved_offset = *offset;
51 *value = data.GetMaxS64(offset, byte_size);
52 return *offset != saved_offset;
53 }
54
GetMaxS64(const lldb_private::DataExtractor & data,lldb::offset_t * offset,int64_t * value,uint32_t byte_size,uint32_t count)55 static bool GetMaxS64(const lldb_private::DataExtractor &data,
56 lldb::offset_t *offset, int64_t *value,
57 uint32_t byte_size, uint32_t count) {
58 lldb::offset_t saved_offset = *offset;
59
60 for (uint32_t i = 0; i < count; ++i, ++value) {
61 if (!GetMaxS64(data, offset, value, byte_size)) {
62 *offset = saved_offset;
63 return false;
64 }
65 }
66 return true;
67 }
68
69 // ELFHeader
70
ELFHeader()71 ELFHeader::ELFHeader() { memset(this, 0, sizeof(ELFHeader)); }
72
GetByteOrder() const73 ByteOrder ELFHeader::GetByteOrder() const {
74 if (e_ident[EI_DATA] == ELFDATA2MSB)
75 return eByteOrderBig;
76 if (e_ident[EI_DATA] == ELFDATA2LSB)
77 return eByteOrderLittle;
78 return eByteOrderInvalid;
79 }
80
HasHeaderExtension() const81 bool ELFHeader::HasHeaderExtension() const {
82 bool result = false;
83
84 // Check if any of these values looks like sentinel.
85 result |= e_phnum_hdr == 0xFFFF; // PN_XNUM
86 result |= e_shnum_hdr == SHN_UNDEF;
87 result |= e_shstrndx_hdr == SHN_XINDEX;
88
89 // If header extension is present, the section offset cannot be null.
90 result &= e_shoff != 0;
91
92 // Done.
93 return result;
94 }
95
ParseHeaderExtension(lldb_private::DataExtractor & data)96 void ELFHeader::ParseHeaderExtension(lldb_private::DataExtractor &data) {
97 // Extract section #0 header.
98 ELFSectionHeader section_zero;
99 lldb::offset_t offset = 0;
100 lldb_private::DataExtractor sh_data(data, e_shoff, e_shentsize);
101 bool ok = section_zero.Parse(sh_data, &offset);
102
103 // If we succeeded, fix the header.
104 if (ok) {
105 if (e_phnum_hdr == 0xFFFF) // PN_XNUM
106 e_phnum = section_zero.sh_info;
107 if (e_shnum_hdr == SHN_UNDEF)
108 e_shnum = section_zero.sh_size;
109 if (e_shstrndx_hdr == SHN_XINDEX)
110 e_shstrndx = section_zero.sh_link;
111 }
112 }
113
Parse(lldb_private::DataExtractor & data,lldb::offset_t * offset)114 bool ELFHeader::Parse(lldb_private::DataExtractor &data,
115 lldb::offset_t *offset) {
116 // Read e_ident. This provides byte order and address size info.
117 if (data.GetU8(offset, &e_ident, EI_NIDENT) == nullptr)
118 return false;
119
120 const unsigned byte_size = Is32Bit() ? 4 : 8;
121 data.SetByteOrder(GetByteOrder());
122 data.SetAddressByteSize(byte_size);
123
124 // Read e_type and e_machine.
125 if (data.GetU16(offset, &e_type, 2) == nullptr)
126 return false;
127
128 // Read e_version.
129 if (data.GetU32(offset, &e_version, 1) == nullptr)
130 return false;
131
132 // Read e_entry, e_phoff and e_shoff.
133 if (!GetMaxU64(data, offset, &e_entry, byte_size, 3))
134 return false;
135
136 // Read e_flags.
137 if (data.GetU32(offset, &e_flags, 1) == nullptr)
138 return false;
139
140 // Read e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum and e_shstrndx.
141 if (data.GetU16(offset, &e_ehsize, 6) == nullptr)
142 return false;
143
144 // Initialize e_phnum, e_shnum, and e_shstrndx with the values read from the
145 // header.
146 e_phnum = e_phnum_hdr;
147 e_shnum = e_shnum_hdr;
148 e_shstrndx = e_shstrndx_hdr;
149
150 // See if we have extended header in section #0.
151 if (HasHeaderExtension())
152 ParseHeaderExtension(data);
153
154 return true;
155 }
156
MagicBytesMatch(const uint8_t * magic)157 bool ELFHeader::MagicBytesMatch(const uint8_t *magic) {
158 return memcmp(magic, ElfMagic, strlen(ElfMagic)) == 0;
159 }
160
AddressSizeInBytes(const uint8_t * magic)161 unsigned ELFHeader::AddressSizeInBytes(const uint8_t *magic) {
162 unsigned address_size = 0;
163
164 switch (magic[EI_CLASS]) {
165 case ELFCLASS32:
166 address_size = 4;
167 break;
168
169 case ELFCLASS64:
170 address_size = 8;
171 break;
172 }
173 return address_size;
174 }
175
GetRelocationJumpSlotType() const176 unsigned ELFHeader::GetRelocationJumpSlotType() const {
177 unsigned slot = 0;
178
179 switch (e_machine) {
180 default:
181 assert(false && "architecture not supported");
182 break;
183 case EM_PPC:
184 slot = R_PPC_JMP_SLOT;
185 break;
186 case EM_PPC64:
187 slot = R_PPC64_JMP_SLOT;
188 break;
189 case EM_386:
190 case EM_IAMCU: // FIXME: is this correct?
191 slot = R_386_JUMP_SLOT;
192 break;
193 case EM_X86_64:
194 slot = R_X86_64_JUMP_SLOT;
195 break;
196 case EM_ARM:
197 slot = R_ARM_JUMP_SLOT;
198 break;
199 case EM_HEXAGON:
200 slot = R_HEX_JMP_SLOT;
201 break;
202 case EM_AARCH64:
203 slot = R_AARCH64_JUMP_SLOT;
204 break;
205 case EM_MIPS:
206 slot = R_MIPS_JUMP_SLOT;
207 break;
208 case EM_S390:
209 slot = R_390_JMP_SLOT;
210 break;
211 case EM_RISCV:
212 slot = R_RISCV_JUMP_SLOT;
213 break;
214 case EM_LOONGARCH:
215 slot = R_LARCH_JUMP_SLOT;
216 break;
217 }
218
219 return slot;
220 }
221
222 // ELFSectionHeader
223
ELFSectionHeader()224 ELFSectionHeader::ELFSectionHeader() {
225 memset(this, 0, sizeof(ELFSectionHeader));
226 }
227
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)228 bool ELFSectionHeader::Parse(const lldb_private::DataExtractor &data,
229 lldb::offset_t *offset) {
230 const unsigned byte_size = data.GetAddressByteSize();
231
232 // Read sh_name and sh_type.
233 if (data.GetU32(offset, &sh_name, 2) == nullptr)
234 return false;
235
236 // Read sh_flags.
237 if (!GetMaxU64(data, offset, &sh_flags, byte_size))
238 return false;
239
240 // Read sh_addr, sh_off and sh_size.
241 if (!GetMaxU64(data, offset, &sh_addr, byte_size, 3))
242 return false;
243
244 // Read sh_link and sh_info.
245 if (data.GetU32(offset, &sh_link, 2) == nullptr)
246 return false;
247
248 // Read sh_addralign and sh_entsize.
249 if (!GetMaxU64(data, offset, &sh_addralign, byte_size, 2))
250 return false;
251
252 return true;
253 }
254
255 // ELFSymbol
256
ELFSymbol()257 ELFSymbol::ELFSymbol() { memset(this, 0, sizeof(ELFSymbol)); }
258
259 #define ENUM_TO_CSTR(e) \
260 case e: \
261 return #e
262
bindingToCString(unsigned char binding)263 const char *ELFSymbol::bindingToCString(unsigned char binding) {
264 switch (binding) {
265 ENUM_TO_CSTR(STB_LOCAL);
266 ENUM_TO_CSTR(STB_GLOBAL);
267 ENUM_TO_CSTR(STB_WEAK);
268 ENUM_TO_CSTR(STB_LOOS);
269 ENUM_TO_CSTR(STB_HIOS);
270 ENUM_TO_CSTR(STB_LOPROC);
271 ENUM_TO_CSTR(STB_HIPROC);
272 }
273 return "";
274 }
275
typeToCString(unsigned char type)276 const char *ELFSymbol::typeToCString(unsigned char type) {
277 switch (type) {
278 ENUM_TO_CSTR(STT_NOTYPE);
279 ENUM_TO_CSTR(STT_OBJECT);
280 ENUM_TO_CSTR(STT_FUNC);
281 ENUM_TO_CSTR(STT_SECTION);
282 ENUM_TO_CSTR(STT_FILE);
283 ENUM_TO_CSTR(STT_COMMON);
284 ENUM_TO_CSTR(STT_TLS);
285 ENUM_TO_CSTR(STT_GNU_IFUNC);
286 ENUM_TO_CSTR(STT_HIOS);
287 ENUM_TO_CSTR(STT_LOPROC);
288 ENUM_TO_CSTR(STT_HIPROC);
289 }
290 return "";
291 }
292
sectionIndexToCString(elf_half shndx,const lldb_private::SectionList * section_list)293 const char *ELFSymbol::sectionIndexToCString(
294 elf_half shndx, const lldb_private::SectionList *section_list) {
295 switch (shndx) {
296 ENUM_TO_CSTR(SHN_UNDEF);
297 ENUM_TO_CSTR(SHN_LOPROC);
298 ENUM_TO_CSTR(SHN_HIPROC);
299 ENUM_TO_CSTR(SHN_LOOS);
300 ENUM_TO_CSTR(SHN_HIOS);
301 ENUM_TO_CSTR(SHN_ABS);
302 ENUM_TO_CSTR(SHN_COMMON);
303 ENUM_TO_CSTR(SHN_XINDEX);
304 default: {
305 const lldb_private::Section *section =
306 section_list->GetSectionAtIndex(shndx).get();
307 if (section)
308 return section->GetName().AsCString("");
309 } break;
310 }
311 return "";
312 }
313
Dump(lldb_private::Stream * s,uint32_t idx,const lldb_private::DataExtractor * strtab_data,const lldb_private::SectionList * section_list)314 void ELFSymbol::Dump(lldb_private::Stream *s, uint32_t idx,
315 const lldb_private::DataExtractor *strtab_data,
316 const lldb_private::SectionList *section_list) {
317 s->Printf("[%3u] 0x%16.16" PRIx64 " 0x%16.16" PRIx64
318 " 0x%8.8x 0x%2.2x (%-10s %-13s) 0x%2.2x 0x%4.4x (%-10s) %s\n",
319 idx, st_value, st_size, st_name, st_info,
320 bindingToCString(getBinding()), typeToCString(getType()), st_other,
321 st_shndx, sectionIndexToCString(st_shndx, section_list),
322 strtab_data ? strtab_data->PeekCStr(st_name) : "");
323 }
324
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)325 bool ELFSymbol::Parse(const lldb_private::DataExtractor &data,
326 lldb::offset_t *offset) {
327 const unsigned byte_size = data.GetAddressByteSize();
328 const bool parsing_32 = byte_size == 4;
329
330 // Read st_name.
331 if (data.GetU32(offset, &st_name, 1) == nullptr)
332 return false;
333
334 if (parsing_32) {
335 // Read st_value and st_size.
336 if (!GetMaxU64(data, offset, &st_value, byte_size, 2))
337 return false;
338
339 // Read st_info and st_other.
340 if (data.GetU8(offset, &st_info, 2) == nullptr)
341 return false;
342
343 // Read st_shndx.
344 if (data.GetU16(offset, &st_shndx, 1) == nullptr)
345 return false;
346 } else {
347 // Read st_info and st_other.
348 if (data.GetU8(offset, &st_info, 2) == nullptr)
349 return false;
350
351 // Read st_shndx.
352 if (data.GetU16(offset, &st_shndx, 1) == nullptr)
353 return false;
354
355 // Read st_value and st_size.
356 if (data.GetU64(offset, &st_value, 2) == nullptr)
357 return false;
358 }
359 return true;
360 }
361
362 // ELFProgramHeader
363
ELFProgramHeader()364 ELFProgramHeader::ELFProgramHeader() {
365 memset(this, 0, sizeof(ELFProgramHeader));
366 }
367
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)368 bool ELFProgramHeader::Parse(const lldb_private::DataExtractor &data,
369 lldb::offset_t *offset) {
370 const uint32_t byte_size = data.GetAddressByteSize();
371 const bool parsing_32 = byte_size == 4;
372
373 // Read p_type;
374 if (data.GetU32(offset, &p_type, 1) == nullptr)
375 return false;
376
377 if (parsing_32) {
378 // Read p_offset, p_vaddr, p_paddr, p_filesz and p_memsz.
379 if (!GetMaxU64(data, offset, &p_offset, byte_size, 5))
380 return false;
381
382 // Read p_flags.
383 if (data.GetU32(offset, &p_flags, 1) == nullptr)
384 return false;
385
386 // Read p_align.
387 if (!GetMaxU64(data, offset, &p_align, byte_size))
388 return false;
389 } else {
390 // Read p_flags.
391 if (data.GetU32(offset, &p_flags, 1) == nullptr)
392 return false;
393
394 // Read p_offset, p_vaddr, p_paddr, p_filesz, p_memsz and p_align.
395 if (!GetMaxU64(data, offset, &p_offset, byte_size, 6))
396 return false;
397 }
398
399 return true;
400 }
401
402 // ELFDynamic
403
ELFDynamic()404 ELFDynamic::ELFDynamic() { memset(this, 0, sizeof(ELFDynamic)); }
405
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)406 bool ELFDynamic::Parse(const lldb_private::DataExtractor &data,
407 lldb::offset_t *offset) {
408 const unsigned byte_size = data.GetAddressByteSize();
409 return GetMaxS64(data, offset, &d_tag, byte_size, 2);
410 }
411
412 // ELFRel
413
ELFRel()414 ELFRel::ELFRel() { memset(this, 0, sizeof(ELFRel)); }
415
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)416 bool ELFRel::Parse(const lldb_private::DataExtractor &data,
417 lldb::offset_t *offset) {
418 const unsigned byte_size = data.GetAddressByteSize();
419
420 // Read r_offset and r_info.
421 return GetMaxU64(data, offset, &r_offset, byte_size, 2) != false;
422 }
423
424 // ELFRela
425
ELFRela()426 ELFRela::ELFRela() { memset(this, 0, sizeof(ELFRela)); }
427
Parse(const lldb_private::DataExtractor & data,lldb::offset_t * offset)428 bool ELFRela::Parse(const lldb_private::DataExtractor &data,
429 lldb::offset_t *offset) {
430 const unsigned byte_size = data.GetAddressByteSize();
431
432 // Read r_offset and r_info.
433 if (!GetMaxU64(data, offset, &r_offset, byte_size, 2))
434 return false;
435
436 // Read r_addend;
437 if (!GetMaxS64(data, offset, &r_addend, byte_size))
438 return false;
439
440 return true;
441 }
442