1#include <stdio.h>
2#include <stdarg.h>
3#include <stdlib.h>
4#include <stdint.h>
5#include <string.h>
6#include <errno.h>
7#include <unistd.h>
8#include <elf.h>
9#include <byteswap.h>
10#define USE_BSD
11#include <endian.h>
12
13#define MAX_SHDRS 100
14#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
15static Elf32_Ehdr ehdr;
16static Elf32_Shdr shdr[MAX_SHDRS];
17static Elf32_Sym *symtab[MAX_SHDRS];
18static Elf32_Rel *reltab[MAX_SHDRS];
19static char *strtab[MAX_SHDRS];
20static unsigned long reloc_count, reloc_idx;
21static unsigned long *relocs;
22
23
24
25
26
27
28
29static const char* safe_abs_relocs[] = {
30 "__kernel_vsyscall",
31 "__kernel_rt_sigreturn",
32 "__kernel_sigreturn",
33 "SYSENTER_RETURN",
34 "VDSO_NOTE_MASK",
35 "xen_irq_disable_direct_reloc",
36 "xen_save_fl_direct_reloc",
37};
38
39static int is_safe_abs_reloc(const char* sym_name)
40{
41 int i;
42
43 for(i = 0; i < ARRAY_SIZE(safe_abs_relocs); i++) {
44 if (!strcmp(sym_name, safe_abs_relocs[i]))
45
46 return 1;
47 }
48 if (strncmp(sym_name, "__crc_", 6) == 0)
49 return 1;
50 return 0;
51}
52
53static void die(char *fmt, ...)
54{
55 va_list ap;
56 va_start(ap, fmt);
57 vfprintf(stderr, fmt, ap);
58 va_end(ap);
59 exit(1);
60}
61
62static const char *sym_type(unsigned type)
63{
64 static const char *type_name[] = {
65#define SYM_TYPE(X) [X] = #X
66 SYM_TYPE(STT_NOTYPE),
67 SYM_TYPE(STT_OBJECT),
68 SYM_TYPE(STT_FUNC),
69 SYM_TYPE(STT_SECTION),
70 SYM_TYPE(STT_FILE),
71 SYM_TYPE(STT_COMMON),
72 SYM_TYPE(STT_TLS),
73#undef SYM_TYPE
74 };
75 const char *name = "unknown sym type name";
76 if (type < ARRAY_SIZE(type_name)) {
77 name = type_name[type];
78 }
79 return name;
80}
81
82static const char *sym_bind(unsigned bind)
83{
84 static const char *bind_name[] = {
85#define SYM_BIND(X) [X] = #X
86 SYM_BIND(STB_LOCAL),
87 SYM_BIND(STB_GLOBAL),
88 SYM_BIND(STB_WEAK),
89#undef SYM_BIND
90 };
91 const char *name = "unknown sym bind name";
92 if (bind < ARRAY_SIZE(bind_name)) {
93 name = bind_name[bind];
94 }
95 return name;
96}
97
98static const char *sym_visibility(unsigned visibility)
99{
100 static const char *visibility_name[] = {
101#define SYM_VISIBILITY(X) [X] = #X
102 SYM_VISIBILITY(STV_DEFAULT),
103 SYM_VISIBILITY(STV_INTERNAL),
104 SYM_VISIBILITY(STV_HIDDEN),
105 SYM_VISIBILITY(STV_PROTECTED),
106#undef SYM_VISIBILITY
107 };
108 const char *name = "unknown sym visibility name";
109 if (visibility < ARRAY_SIZE(visibility_name)) {
110 name = visibility_name[visibility];
111 }
112 return name;
113}
114
115static const char *rel_type(unsigned type)
116{
117 static const char *type_name[] = {
118#define REL_TYPE(X) [X] = #X
119 REL_TYPE(R_386_NONE),
120 REL_TYPE(R_386_32),
121 REL_TYPE(R_386_PC32),
122 REL_TYPE(R_386_GOT32),
123 REL_TYPE(R_386_PLT32),
124 REL_TYPE(R_386_COPY),
125 REL_TYPE(R_386_GLOB_DAT),
126 REL_TYPE(R_386_JMP_SLOT),
127 REL_TYPE(R_386_RELATIVE),
128 REL_TYPE(R_386_GOTOFF),
129 REL_TYPE(R_386_GOTPC),
130#undef REL_TYPE
131 };
132 const char *name = "unknown type rel type name";
133 if (type < ARRAY_SIZE(type_name)) {
134 name = type_name[type];
135 }
136 return name;
137}
138
139static const char *sec_name(unsigned shndx)
140{
141 const char *sec_strtab;
142 const char *name;
143 sec_strtab = strtab[ehdr.e_shstrndx];
144 name = "<noname>";
145 if (shndx < ehdr.e_shnum) {
146 name = sec_strtab + shdr[shndx].sh_name;
147 }
148 else if (shndx == SHN_ABS) {
149 name = "ABSOLUTE";
150 }
151 else if (shndx == SHN_COMMON) {
152 name = "COMMON";
153 }
154 return name;
155}
156
157static const char *sym_name(const char *sym_strtab, Elf32_Sym *sym)
158{
159 const char *name;
160 name = "<noname>";
161 if (sym->st_name) {
162 name = sym_strtab + sym->st_name;
163 }
164 else {
165 name = sec_name(shdr[sym->st_shndx].sh_name);
166 }
167 return name;
168}
169
170
171
172#if BYTE_ORDER == LITTLE_ENDIAN
173#define le16_to_cpu(val) (val)
174#define le32_to_cpu(val) (val)
175#endif
176#if BYTE_ORDER == BIG_ENDIAN
177#define le16_to_cpu(val) bswap_16(val)
178#define le32_to_cpu(val) bswap_32(val)
179#endif
180
181static uint16_t elf16_to_cpu(uint16_t val)
182{
183 return le16_to_cpu(val);
184}
185
186static uint32_t elf32_to_cpu(uint32_t val)
187{
188 return le32_to_cpu(val);
189}
190
191static void read_ehdr(FILE *fp)
192{
193 if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) {
194 die("Cannot read ELF header: %s\n",
195 strerror(errno));
196 }
197 if (memcmp(ehdr.e_ident, ELFMAG, 4) != 0) {
198 die("No ELF magic\n");
199 }
200 if (ehdr.e_ident[EI_CLASS] != ELFCLASS32) {
201 die("Not a 32 bit executable\n");
202 }
203 if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB) {
204 die("Not a LSB ELF executable\n");
205 }
206 if (ehdr.e_ident[EI_VERSION] != EV_CURRENT) {
207 die("Unknown ELF version\n");
208 }
209
210 ehdr.e_type = elf16_to_cpu(ehdr.e_type);
211 ehdr.e_machine = elf16_to_cpu(ehdr.e_machine);
212 ehdr.e_version = elf32_to_cpu(ehdr.e_version);
213 ehdr.e_entry = elf32_to_cpu(ehdr.e_entry);
214 ehdr.e_phoff = elf32_to_cpu(ehdr.e_phoff);
215 ehdr.e_shoff = elf32_to_cpu(ehdr.e_shoff);
216 ehdr.e_flags = elf32_to_cpu(ehdr.e_flags);
217 ehdr.e_ehsize = elf16_to_cpu(ehdr.e_ehsize);
218 ehdr.e_phentsize = elf16_to_cpu(ehdr.e_phentsize);
219 ehdr.e_phnum = elf16_to_cpu(ehdr.e_phnum);
220 ehdr.e_shentsize = elf16_to_cpu(ehdr.e_shentsize);
221 ehdr.e_shnum = elf16_to_cpu(ehdr.e_shnum);
222 ehdr.e_shstrndx = elf16_to_cpu(ehdr.e_shstrndx);
223
224 if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN)) {
225 die("Unsupported ELF header type\n");
226 }
227 if (ehdr.e_machine != EM_386) {
228 die("Not for x86\n");
229 }
230 if (ehdr.e_version != EV_CURRENT) {
231 die("Unknown ELF version\n");
232 }
233 if (ehdr.e_ehsize != sizeof(Elf32_Ehdr)) {
234 die("Bad Elf header size\n");
235 }
236 if (ehdr.e_phentsize != sizeof(Elf32_Phdr)) {
237 die("Bad program header entry\n");
238 }
239 if (ehdr.e_shentsize != sizeof(Elf32_Shdr)) {
240 die("Bad section header entry\n");
241 }
242 if (ehdr.e_shstrndx >= ehdr.e_shnum) {
243 die("String table index out of bounds\n");
244 }
245}
246
247static void read_shdrs(FILE *fp)
248{
249 int i;
250 if (ehdr.e_shnum > MAX_SHDRS) {
251 die("%d section headers supported: %d\n",
252 ehdr.e_shnum, MAX_SHDRS);
253 }
254 if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
255 die("Seek to %d failed: %s\n",
256 ehdr.e_shoff, strerror(errno));
257 }
258 if (fread(&shdr, sizeof(shdr[0]), ehdr.e_shnum, fp) != ehdr.e_shnum) {
259 die("Cannot read ELF section headers: %s\n",
260 strerror(errno));
261 }
262 for(i = 0; i < ehdr.e_shnum; i++) {
263 shdr[i].sh_name = elf32_to_cpu(shdr[i].sh_name);
264 shdr[i].sh_type = elf32_to_cpu(shdr[i].sh_type);
265 shdr[i].sh_flags = elf32_to_cpu(shdr[i].sh_flags);
266 shdr[i].sh_addr = elf32_to_cpu(shdr[i].sh_addr);
267 shdr[i].sh_offset = elf32_to_cpu(shdr[i].sh_offset);
268 shdr[i].sh_size = elf32_to_cpu(shdr[i].sh_size);
269 shdr[i].sh_link = elf32_to_cpu(shdr[i].sh_link);
270 shdr[i].sh_info = elf32_to_cpu(shdr[i].sh_info);
271 shdr[i].sh_addralign = elf32_to_cpu(shdr[i].sh_addralign);
272 shdr[i].sh_entsize = elf32_to_cpu(shdr[i].sh_entsize);
273 }
274
275}
276
277static void read_strtabs(FILE *fp)
278{
279 int i;
280 for(i = 0; i < ehdr.e_shnum; i++) {
281 if (shdr[i].sh_type != SHT_STRTAB) {
282 continue;
283 }
284 strtab[i] = malloc(shdr[i].sh_size);
285 if (!strtab[i]) {
286 die("malloc of %d bytes for strtab failed\n",
287 shdr[i].sh_size);
288 }
289 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
290 die("Seek to %d failed: %s\n",
291 shdr[i].sh_offset, strerror(errno));
292 }
293 if (fread(strtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
294 die("Cannot read symbol table: %s\n",
295 strerror(errno));
296 }
297 }
298}
299
300static void read_symtabs(FILE *fp)
301{
302 int i,j;
303 for(i = 0; i < ehdr.e_shnum; i++) {
304 if (shdr[i].sh_type != SHT_SYMTAB) {
305 continue;
306 }
307 symtab[i] = malloc(shdr[i].sh_size);
308 if (!symtab[i]) {
309 die("malloc of %d bytes for symtab failed\n",
310 shdr[i].sh_size);
311 }
312 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
313 die("Seek to %d failed: %s\n",
314 shdr[i].sh_offset, strerror(errno));
315 }
316 if (fread(symtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
317 die("Cannot read symbol table: %s\n",
318 strerror(errno));
319 }
320 for(j = 0; j < shdr[i].sh_size/sizeof(symtab[i][0]); j++) {
321 symtab[i][j].st_name = elf32_to_cpu(symtab[i][j].st_name);
322 symtab[i][j].st_value = elf32_to_cpu(symtab[i][j].st_value);
323 symtab[i][j].st_size = elf32_to_cpu(symtab[i][j].st_size);
324 symtab[i][j].st_shndx = elf16_to_cpu(symtab[i][j].st_shndx);
325 }
326 }
327}
328
329
330static void read_relocs(FILE *fp)
331{
332 int i,j;
333 for(i = 0; i < ehdr.e_shnum; i++) {
334 if (shdr[i].sh_type != SHT_REL) {
335 continue;
336 }
337 reltab[i] = malloc(shdr[i].sh_size);
338 if (!reltab[i]) {
339 die("malloc of %d bytes for relocs failed\n",
340 shdr[i].sh_size);
341 }
342 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
343 die("Seek to %d failed: %s\n",
344 shdr[i].sh_offset, strerror(errno));
345 }
346 if (fread(reltab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
347 die("Cannot read symbol table: %s\n",
348 strerror(errno));
349 }
350 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
351 reltab[i][j].r_offset = elf32_to_cpu(reltab[i][j].r_offset);
352 reltab[i][j].r_info = elf32_to_cpu(reltab[i][j].r_info);
353 }
354 }
355}
356
357
358static void print_absolute_symbols(void)
359{
360 int i;
361 printf("Absolute symbols\n");
362 printf(" Num: Value Size Type Bind Visibility Name\n");
363 for(i = 0; i < ehdr.e_shnum; i++) {
364 char *sym_strtab;
365 Elf32_Sym *sh_symtab;
366 int j;
367 if (shdr[i].sh_type != SHT_SYMTAB) {
368 continue;
369 }
370 sh_symtab = symtab[i];
371 sym_strtab = strtab[shdr[i].sh_link];
372 for(j = 0; j < shdr[i].sh_size/sizeof(symtab[0][0]); j++) {
373 Elf32_Sym *sym;
374 const char *name;
375 sym = &symtab[i][j];
376 name = sym_name(sym_strtab, sym);
377 if (sym->st_shndx != SHN_ABS) {
378 continue;
379 }
380 printf("%5d %08x %5d %10s %10s %12s %s\n",
381 j, sym->st_value, sym->st_size,
382 sym_type(ELF32_ST_TYPE(sym->st_info)),
383 sym_bind(ELF32_ST_BIND(sym->st_info)),
384 sym_visibility(ELF32_ST_VISIBILITY(sym->st_other)),
385 name);
386 }
387 }
388 printf("\n");
389}
390
391static void print_absolute_relocs(void)
392{
393 int i, printed = 0;
394
395 for(i = 0; i < ehdr.e_shnum; i++) {
396 char *sym_strtab;
397 Elf32_Sym *sh_symtab;
398 unsigned sec_applies, sec_symtab;
399 int j;
400 if (shdr[i].sh_type != SHT_REL) {
401 continue;
402 }
403 sec_symtab = shdr[i].sh_link;
404 sec_applies = shdr[i].sh_info;
405 if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) {
406 continue;
407 }
408 sh_symtab = symtab[sec_symtab];
409 sym_strtab = strtab[shdr[sec_symtab].sh_link];
410 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
411 Elf32_Rel *rel;
412 Elf32_Sym *sym;
413 const char *name;
414 rel = &reltab[i][j];
415 sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
416 name = sym_name(sym_strtab, sym);
417 if (sym->st_shndx != SHN_ABS) {
418 continue;
419 }
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434 if (is_safe_abs_reloc(name))
435 continue;
436
437 if (!printed) {
438 printf("WARNING: Absolute relocations"
439 " present\n");
440 printf("Offset Info Type Sym.Value "
441 "Sym.Name\n");
442 printed = 1;
443 }
444
445 printf("%08x %08x %10s %08x %s\n",
446 rel->r_offset,
447 rel->r_info,
448 rel_type(ELF32_R_TYPE(rel->r_info)),
449 sym->st_value,
450 name);
451 }
452 }
453
454 if (printed)
455 printf("\n");
456}
457
458static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
459{
460 int i;
461
462 for(i = 0; i < ehdr.e_shnum; i++) {
463 char *sym_strtab;
464 Elf32_Sym *sh_symtab;
465 unsigned sec_applies, sec_symtab;
466 int j;
467 if (shdr[i].sh_type != SHT_REL) {
468 continue;
469 }
470 sec_symtab = shdr[i].sh_link;
471 sec_applies = shdr[i].sh_info;
472 if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) {
473 continue;
474 }
475 sh_symtab = symtab[sec_symtab];
476 sym_strtab = strtab[shdr[sec_symtab].sh_link];
477 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
478 Elf32_Rel *rel;
479 Elf32_Sym *sym;
480 unsigned r_type;
481 rel = &reltab[i][j];
482 sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
483 r_type = ELF32_R_TYPE(rel->r_info);
484
485 if (sym->st_shndx == SHN_ABS) {
486 continue;
487 }
488 if (r_type == R_386_PC32) {
489
490 }
491 else if (r_type == R_386_32) {
492
493 visit(rel, sym);
494 }
495 else {
496 die("Unsupported relocation type: %d\n", r_type);
497 }
498 }
499 }
500}
501
502static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
503{
504 reloc_count += 1;
505}
506
507static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
508{
509
510 relocs[reloc_idx++] = rel->r_offset;
511}
512
513static int cmp_relocs(const void *va, const void *vb)
514{
515 const unsigned long *a, *b;
516 a = va; b = vb;
517 return (*a == *b)? 0 : (*a > *b)? 1 : -1;
518}
519
520static void emit_relocs(int as_text)
521{
522 int i;
523
524 reloc_count = 0;
525 walk_relocs(count_reloc);
526 relocs = malloc(reloc_count * sizeof(relocs[0]));
527 if (!relocs) {
528 die("malloc of %d entries for relocs failed\n",
529 reloc_count);
530 }
531
532 reloc_idx = 0;
533 walk_relocs(collect_reloc);
534
535
536 qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
537
538
539 if (as_text) {
540
541
542
543 printf(".section \".data.reloc\",\"a\"\n");
544 printf(".balign 4\n");
545 for(i = 0; i < reloc_count; i++) {
546 printf("\t .long 0x%08lx\n", relocs[i]);
547 }
548 printf("\n");
549 }
550 else {
551 unsigned char buf[4];
552 buf[0] = buf[1] = buf[2] = buf[3] = 0;
553
554 printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
555
556 for(i = 0; i < reloc_count; i++) {
557 buf[0] = (relocs[i] >> 0) & 0xff;
558 buf[1] = (relocs[i] >> 8) & 0xff;
559 buf[2] = (relocs[i] >> 16) & 0xff;
560 buf[3] = (relocs[i] >> 24) & 0xff;
561 printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
562 }
563 }
564}
565
566static void usage(void)
567{
568 die("relocs [--abs-syms |--abs-relocs | --text] vmlinux\n");
569}
570
571int main(int argc, char **argv)
572{
573 int show_absolute_syms, show_absolute_relocs;
574 int as_text;
575 const char *fname;
576 FILE *fp;
577 int i;
578
579 show_absolute_syms = 0;
580 show_absolute_relocs = 0;
581 as_text = 0;
582 fname = NULL;
583 for(i = 1; i < argc; i++) {
584 char *arg = argv[i];
585 if (*arg == '-') {
586 if (strcmp(argv[1], "--abs-syms") == 0) {
587 show_absolute_syms = 1;
588 continue;
589 }
590
591 if (strcmp(argv[1], "--abs-relocs") == 0) {
592 show_absolute_relocs = 1;
593 continue;
594 }
595 else if (strcmp(argv[1], "--text") == 0) {
596 as_text = 1;
597 continue;
598 }
599 }
600 else if (!fname) {
601 fname = arg;
602 continue;
603 }
604 usage();
605 }
606 if (!fname) {
607 usage();
608 }
609 fp = fopen(fname, "r");
610 if (!fp) {
611 die("Cannot open %s: %s\n",
612 fname, strerror(errno));
613 }
614 read_ehdr(fp);
615 read_shdrs(fp);
616 read_strtabs(fp);
617 read_symtabs(fp);
618 read_relocs(fp);
619 if (show_absolute_syms) {
620 print_absolute_symbols();
621 return 0;
622 }
623 if (show_absolute_relocs) {
624 print_absolute_relocs();
625 return 0;
626 }
627 emit_relocs(as_text);
628 return 0;
629}
630
