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1/* $OpenBSD: elf.c,v 1.39 2021/11/07 08:09:04 semarie Exp $ */
2
3/*
4 * Copyright (c) 2003 Michael Shalayeff
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR OR HIS RELATIVES BE LIABLE FOR ANY DIRECT,
20 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF MIND, USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
24 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
25 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
26 * THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/mman.h>
30#include <unistd.h>
31#include <a.out.h>
32#include <elf.h>
33#include <errno.h>
34#include <err.h>
35#include <stdint.h>
36#include <stdio.h>
37#include <stdlib.h>
38#include <string.h>
39#include <ctype.h>
40#include "util.h"
41#include "elfuncs.h"
42
43#if ELFSIZE == 32
44#define swap_addr swap32
45#define swap_off swap32
46#define swap_sword swap32
47#define swap_word swap32
48#define swap_sxword swap32
49#define swap_xword swap32
50#define swap_half swap16
51#define swap_quarter swap16
52#define elf_fix_header elf32_fix_header
53#define elf_load_shdrs elf32_load_shdrs
54#define elf_fix_shdrs elf32_fix_shdrs
55#define elf_fix_sym elf32_fix_sym
56#define elf_size elf32_size
57#define elf_symloadx elf32_symloadx
58#define elf_symload elf32_symload
59#define elf2nlist elf32_2nlist
60#define elf_shn2type elf32_shn2type
61#elif ELFSIZE == 64
62#define swap_addr swap64
63#define swap_off swap64
64#ifdef __alpha__
65#define swap_sword swap64
66#define swap_word swap64
67#else
68#define swap_sword swap32
69#define swap_word swap32
70#endif
71#define swap_sxword swap64
72#define swap_xword swap64
73#define swap_half swap64
74#define swap_quarter swap16
75#define elf_fix_header elf64_fix_header
76#define elf_load_shdrs elf64_load_shdrs
77#define elf_fix_shdrs elf64_fix_shdrs
78#define elf_fix_sym elf64_fix_sym
79#define elf_size elf64_size
80#define elf_symloadx elf64_symloadx
81#define elf_symload elf64_symload
82#define elf2nlist elf64_2nlist
83#define elf_shn2type elf64_shn2type
84#else
85#error "Unsupported ELF class"
86#endif
87
88#define ELF_SDATA ".sdata"
89#define ELF_TDATA ".tdata"
90#define ELF_SBSS ".sbss"
91#define ELF_TBSS ".tbss"
92#define ELF_PLT ".plt"
93
94#ifndef SHN_MIPS_ACOMMON
95#define SHN_MIPS_ACOMMON SHN_LOPROC + 0
96#endif
97#ifndef SHN_MIPS_TEXT
98#define SHN_MIPS_TEXT SHN_LOPROC + 1
99#endif
100#ifndef SHN_MIPS_DATA
101#define SHN_MIPS_DATA SHN_LOPROC + 2
102#endif
103#ifndef SHN_MIPS_SUNDEFINED
104#define SHN_MIPS_SUNDEFINED SHN_LOPROC + 4
105#endif
106#ifndef SHN_MIPS_SCOMMON
107#define SHN_MIPS_SCOMMON SHN_LOPROC + 3
108#endif
109
110#ifndef STT_PARISC_MILLI
111#define STT_PARISC_MILLI STT_LOPROC + 0
112#endif
113
114
115static int elf_fix_header(Elf_Ehdr *);
116static int elf_fix_shdrs(Elf_Ehdr *, Elf_Shdr *);
117static int elf_fix_sym(Elf_Ehdr *, Elf_Sym *);
118static int elf_shn2type(Elf_Ehdr *, u_int _shn, const char *_sn);
119static int elf2nlist(Elf_Sym *, Elf_Ehdr *, Elf_Shdr *, char *_shstr,
120 struct xnlist *_np);
121static int elf_symloadx(const char *_name, FILE *, off_t, Elf_Ehdr *,
122 Elf_Shdr *, char *_shstr, long _shstrsize, struct xnlist **_pnames,
123 struct xnlist ***_psnames, size_t *_pstabsize, int *_pnrawnames,
124 const char *_strtab, const char *_symtab);
125
126int
127elf_fix_header(Elf_Ehdr *eh)
128{
129 /* nothing to do */
130 if (eh->e_ident[EI_DATA] == ELF_TARG_DATA)
131 return (0);
132
133 eh->e_type = swap16(eh->e_type);
134 eh->e_machine = swap16(eh->e_machine);
135 eh->e_version = swap32(eh->e_version);
136 eh->e_entry = swap_addr(eh->e_entry);
137 eh->e_phoff = swap_off(eh->e_phoff);
138 eh->e_shoff = swap_off(eh->e_shoff);
139 eh->e_flags = swap32(eh->e_flags);
140 eh->e_ehsize = swap16(eh->e_ehsize);
141 eh->e_phentsize = swap16(eh->e_phentsize);
142 eh->e_phnum = swap16(eh->e_phnum);
143 eh->e_shentsize = swap16(eh->e_shentsize);
144 eh->e_shnum = swap16(eh->e_shnum);
145 eh->e_shstrndx = swap16(eh->e_shstrndx);
146
147 return (1);
148}
149
150Elf_Shdr *
151elf_load_shdrs(const char *name, FILE *fp, off_t foff, Elf_Ehdr *head)
152{
153 Elf_Shdr *shdr;
154
155 elf_fix_header(head);
156
157 if (head->e_shnum == 0) {
158 warnx("%s: no section header table", name);
159 return (NULL);
160 }
161
162 if (head->e_shstrndx >= head->e_shnum) {
163 warnx("%s: inconsistent section header table", name);
164 return (NULL);
165 }
166
167 if (head->e_shentsize < sizeof(Elf_Shdr)) {
168 warnx("%s: inconsistent section header size", name);
169 return (NULL);
170 }
171
172 if ((shdr = calloc(head->e_shnum, head->e_shentsize)) == NULL) {
173 warn("%s: malloc shdr", name);
174 return (NULL);
175 }
176
177 if (fseeko(fp, foff + head->e_shoff, SEEK_SET)) {
178 warn("%s: fseeko", name);
179 free(shdr);
180 return (NULL);
181 }
182
183 if (fread(shdr, head->e_shentsize, head->e_shnum, fp) != head->e_shnum) {
184 warnx("%s: premature EOF", name);
185 free(shdr);
186 return (NULL);
187 }
188
189 elf_fix_shdrs(head, shdr);
190 return (shdr);
191}
192
193int
194elf_fix_shdrs(Elf_Ehdr *eh, Elf_Shdr *shdr)
195{
196 int i;
197
198 /* nothing to do */
199 if (eh->e_ident[EI_DATA] == ELF_TARG_DATA)
200 return (0);
201
202 for (i = eh->e_shnum; i--; shdr++) {
203 shdr->sh_name = swap32(shdr->sh_name);
204 shdr->sh_type = swap32(shdr->sh_type);
205 shdr->sh_flags = swap_xword(shdr->sh_flags);
206 shdr->sh_addr = swap_addr(shdr->sh_addr);
207 shdr->sh_offset = swap_off(shdr->sh_offset);
208 shdr->sh_size = swap_xword(shdr->sh_size);
209 shdr->sh_link = swap32(shdr->sh_link);
210 shdr->sh_info = swap32(shdr->sh_info);
211 shdr->sh_addralign = swap_xword(shdr->sh_addralign);
212 shdr->sh_entsize = swap_xword(shdr->sh_entsize);
213 }
214
215 return (1);
216}
217
218int
219elf_fix_sym(Elf_Ehdr *eh, Elf_Sym *sym)
220{
221 /* nothing to do */
222 if (eh->e_ident[EI_DATA] == ELF_TARG_DATA)
223 return (0);
224
225 sym->st_name = swap32(sym->st_name);
226 sym->st_shndx = swap16(sym->st_shndx);
227 sym->st_value = swap_addr(sym->st_value);
228 sym->st_size = swap_xword(sym->st_size);
229
230 return (1);
231}
232
233int
234elf_shn2type(Elf_Ehdr *eh, u_int shn, const char *sn)
235{
236 switch (shn) {
237 case SHN_MIPS_SUNDEFINED:
238 if (eh->e_machine == EM_MIPS)
239 return (N_UNDF | N_EXT);
240 break;
241
242 case SHN_UNDEF:
243 return (N_UNDF | N_EXT);
244
245 case SHN_ABS:
246 return (N_ABS);
247
248 case SHN_MIPS_ACOMMON:
249 if (eh->e_machine == EM_MIPS)
250 return (N_COMM);
251 break;
252
253 case SHN_MIPS_SCOMMON:
254 if (eh->e_machine == EM_MIPS)
255 return (N_COMM);
256 break;
257
258 case SHN_COMMON:
259 return (N_COMM);
260
261 case SHN_MIPS_TEXT:
262 if (eh->e_machine == EM_MIPS)
263 return (N_TEXT);
264 break;
265
266 case SHN_MIPS_DATA:
267 if (eh->e_machine == EM_MIPS)
268 return (N_DATA);
269 break;
270
271 default:
272 /* TODO: beyond 8 a table-driven binsearch should be used */
273 if (sn == NULL)
274 return (-1);
275 else if (!strcmp(sn, ELF_TEXT))
276 return (N_TEXT);
277 else if (!strncmp(sn, ".text.", 6))
278 return (N_TEXT);
279 else if (!strcmp(sn, ELF_RODATA))
280 return (N_SIZE);
281 else if (!strcmp(sn, ELF_OPENBSDRANDOMDATA))
282 return (N_SIZE);
283 else if (!strcmp(sn, ELF_DATA))
284 return (N_DATA);
285 else if (!strcmp(sn, ELF_SDATA))
286 return (N_DATA);
287 else if (!strcmp(sn, ELF_TDATA))
288 return (N_DATA);
289 else if (!strcmp(sn, ELF_BSS))
290 return (N_BSS);
291 else if (!strcmp(sn, ELF_SBSS))
292 return (N_BSS);
293 else if (!strcmp(sn, ELF_TBSS))
294 return (N_BSS);
295 else if (!strncmp(sn, ELF_GOT, sizeof(ELF_GOT) - 1))
296 return (N_DATA);
297 else if (!strncmp(sn, ELF_PLT, sizeof(ELF_PLT) - 1))
298 return (N_DATA);
299 }
300
301 return (-1);
302}
303
304/*
305 * Devise xnlist's type from Elf_Sym.
306 * XXX this task is done as well in libc and kvm_mkdb.
307 */
308int
309elf2nlist(Elf_Sym *sym, Elf_Ehdr *eh, Elf_Shdr *shdr, char *shstr,
310 struct xnlist *np)
311{
312 u_char stt;
313 const char *sn;
314 int type;
315
316 if (sym->st_shndx < eh->e_shnum)
317 sn = shstr + shdr[sym->st_shndx].sh_name;
318 else
319 sn = NULL;
320#if 0
321 {
322 extern char *stab;
323 printf("%d:%s %d %d %s\n", sym->st_shndx, sn? sn : "",
324 ELF_ST_TYPE(sym->st_info), ELF_ST_BIND(sym->st_info),
325 stab + sym->st_name);
326 }
327#endif
328
329 switch (stt = ELF_ST_TYPE(sym->st_info)) {
330 case STT_NOTYPE:
331 case STT_OBJECT:
332 case STT_TLS:
333 type = elf_shn2type(eh, sym->st_shndx, sn);
334 if (type < 0) {
335 if (sn == NULL)
336 np->nl.n_other = '?';
337 else
338 np->nl.n_type = stt == STT_NOTYPE ?
339 N_COMM : N_DATA;
340 } else {
341 /* a hack for .rodata check (; */
342 if (type == N_SIZE) {
343 np->nl.n_type = N_DATA;
344 np->nl.n_other = 'r';
345 } else
346 np->nl.n_type = type;
347 }
348 if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
349 np->nl.n_other = 'W';
350 break;
351
352 case STT_FUNC:
353 type = elf_shn2type(eh, sym->st_shndx, NULL);
354 np->nl.n_type = type < 0? N_TEXT : type;
355 if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
356 np->nl.n_other = 'W';
357 } else if (sn != NULL && *sn != 0 &&
358 strcmp(sn, ELF_INIT) &&
359 strcmp(sn, ELF_TEXT) &&
360 strncmp(sn, ".text.", 6) &&
361 strcmp(sn, ELF_FINI)) /* XXX GNU compat */
362 np->nl.n_other = '?';
363 break;
364
365 case STT_SECTION:
366 type = elf_shn2type(eh, sym->st_shndx, NULL);
367 if (type < 0)
368 np->nl.n_other = '?';
369 else
370 np->nl.n_type = type;
371 break;
372
373 case STT_FILE:
374 np->nl.n_type = N_FN | N_EXT;
375 break;
376
377 case STT_PARISC_MILLI:
378 if (eh->e_machine == EM_PARISC)
379 np->nl.n_type = N_TEXT;
380 else
381 np->nl.n_other = '?';
382 break;
383
384 default:
385 np->nl.n_other = '?';
386 break;
387 }
388 if (np->nl.n_type != N_UNDF && ELF_ST_BIND(sym->st_info) != STB_LOCAL) {
389 np->nl.n_type |= N_EXT;
390 if (np->nl.n_other)
391 np->nl.n_other = toupper((unsigned char)np->nl.n_other);
392 }
393
394 return (0);
395}
396
397int
398elf_size(Elf_Ehdr *head, Elf_Shdr *shdr,
399 u_long *ptext, u_long *pdata, u_long *pbss)
400{
401 int i;
402
403 *ptext = *pdata = *pbss = 0;
404
405 for (i = 0; i < head->e_shnum; i++) {
406 if (!(shdr[i].sh_flags & SHF_ALLOC))
407 ;
408 else if (shdr[i].sh_flags & SHF_EXECINSTR ||
409 !(shdr[i].sh_flags & SHF_WRITE))
410 *ptext += shdr[i].sh_size;
411 else if (shdr[i].sh_type == SHT_NOBITS)
412 *pbss += shdr[i].sh_size;
413 else
414 *pdata += shdr[i].sh_size;
415 }
416
417 return (0);
418}
419
420int
421elf_symloadx(const char *name, FILE *fp, off_t foff, Elf_Ehdr *eh,
422 Elf_Shdr *shdr, char *shstr, long shstrsize, struct xnlist **pnames,
423 struct xnlist ***psnames, size_t *pstabsize, int *pnrawnames,
424 const char *strtab, const char *symtab)
425{
426 long symsize;
427 struct xnlist *np;
428 Elf_Sym sbuf;
429 int i;
430
431 for (i = 0; i < eh->e_shnum; i++) {
432 if (shdr[i].sh_name >= shstrsize) {
433 warnx("%s: corrupt file", name);
434 return (1);
435 }
436 if (!strcmp(shstr + shdr[i].sh_name, strtab)) {
437 *pstabsize = shdr[i].sh_size;
438 if (*pstabsize > SIZE_MAX) {
439 warnx("%s: corrupt file", name);
440 return (1);
441 }
442
443 MMAP(stab, *pstabsize, PROT_READ, MAP_PRIVATE|MAP_FILE,
444 fileno(fp), foff + shdr[i].sh_offset);
445 if (stab == MAP_FAILED)
446 return (1);
447 }
448 }
449 for (i = 0; i < eh->e_shnum; i++) {
450 if (!strcmp(shstr + shdr[i].sh_name, symtab)) {
451 symsize = shdr[i].sh_size;
452 if (fseeko(fp, foff + shdr[i].sh_offset, SEEK_SET)) {
453 warn("%s: fseeko", name);
454 if (stab)
455 MUNMAP(stab, *pstabsize);
456 return (1);
457 }
458
459 *pnrawnames = symsize / sizeof(sbuf);
460 if ((*pnames = calloc(*pnrawnames, sizeof(*np))) == NULL) {
461 warn("%s: malloc names", name);
462 if (stab)
463 MUNMAP(stab, *pstabsize);
464 *pnrawnames = 0;
465 return (1);
466 }
467 if ((*psnames = calloc(*pnrawnames, sizeof(np))) == NULL) {
468 warn("%s: malloc snames", name);
469 if (stab)
470 MUNMAP(stab, *pstabsize);
471 free(*pnames);
472 *pnames = NULL;
473 *pnrawnames = 0;
474 return (1);
475 }
476
477 for (np = *pnames; symsize > 0; symsize -= sizeof(sbuf)) {
478 if (fread(&sbuf, 1, sizeof(sbuf),
479 fp) != sizeof(sbuf)) {
480 warn("%s: read symbol", name);
481 if (stab)
482 MUNMAP(stab, *pstabsize);
483 free(*pnames);
484 free(*psnames);
485 *pnames = NULL;
486 *psnames = NULL;
487 *pnrawnames = 0;
488 return (1);
489 }
490
491 elf_fix_sym(eh, &sbuf);
492
493 if (!sbuf.st_name ||
494 sbuf.st_name > *pstabsize)
495 continue;
496
497 elf2nlist(&sbuf, eh, shdr, shstr, np);
498 np->nl.n_value = sbuf.st_value;
499 np->nl.n_un.n_strx = sbuf.st_name;
500 np->n_size = sbuf.st_size;
501 np++;
502 }
503 *pnrawnames = np - *pnames;
504 }
505 }
506 return (0);
507}
508
509int
510elf_symload(const char *name, FILE *fp, off_t foff, Elf_Ehdr *eh,
511 Elf_Shdr *shdr, struct xnlist **pnames, struct xnlist ***psnames,
512 size_t *pstabsize, int *pnrawnames)
513{
514 long shstrsize;
515 char *shstr;
516
517 shstrsize = shdr[eh->e_shstrndx].sh_size;
518 if (shstrsize == 0) {
519 warnx("%s: no name list", name);
520 return (1);
521 }
522
523 if ((shstr = malloc(shstrsize)) == NULL) {
524 warn("%s: malloc shstr", name);
525 return (1);
526 }
527
528 if (fseeko(fp, foff + shdr[eh->e_shstrndx].sh_offset, SEEK_SET)) {
529 warn("%s: fseeko", name);
530 free(shstr);
531 return (1);
532 }
533
534 if (fread(shstr, 1, shstrsize, fp) != shstrsize) {
535 warnx("%s: premature EOF", name);
536 free(shstr);
537 return(1);
538 }
539
540 stab = NULL;
541 *pnames = NULL; *psnames = NULL; *pnrawnames = 0;
542 if (!dynamic_only) {
543 elf_symloadx(name, fp, foff, eh, shdr, shstr, shstrsize, pnames,
544 psnames, pstabsize, pnrawnames, ELF_STRTAB, ELF_SYMTAB);
545 }
546 if (stab == NULL) {
547 elf_symloadx(name, fp, foff, eh, shdr, shstr, shstrsize, pnames,
548 psnames, pstabsize, pnrawnames, ELF_DYNSTR, ELF_DYNSYM);
549 }
550
551 free(shstr);
552 if (stab == NULL) {
553 warnx("%s: no name list", name);
554 free(*pnames);
555 free(*psnames);
556 return (1);
557 }
558
559 return (0);
560}