1 /*
2 * Copyright (C) 1996-1997 John D. Polstra. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
28
29 #include <sys/types.h>
30 #include <sys/mman.h>
31 #include <sys/stat.h>
32
33 #include <machine/elf.h>
34
35 #include <arpa/inet.h>
36
37 #include <a.out.h>
38 #include <assert.h>
39 #include <ctype.h>
40 #include <err.h>
41 #include <fcntl.h>
42 #include <sys/link_aout.h>
43 #include <stab.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <unistd.h>
48
49 #include "extern.h"
50
51 #define PAGE_SIZE 4096 /* i386 specific */
52
53 #ifndef N_SETA
54 #define N_SETA 0x14 /* Absolute set element symbol */
55 #endif /* This is input to LD, in a .o file. */
56
57 #ifndef N_SETT
58 #define N_SETT 0x16 /* Text set element symbol */
59 #endif /* This is input to LD, in a .o file. */
60
61 #ifndef N_SETD
62 #define N_SETD 0x18 /* Data set element symbol */
63 #endif /* This is input to LD, in a .o file. */
64
65 #ifndef N_SETB
66 #define N_SETB 0x1A /* Bss set element symbol */
67 #endif /* This is input to LD, in a .o file. */
68
69 #ifndef N_SETV
70 #define N_SETV 0x1C /* Pointer to set vector in data area. */
71 #endif /* This is output from LD. */
72
73 #ifdef STANDALONE
74 static
75 #endif
76
77 static void dump_rels(const char *, const struct relocation_info *,
78 unsigned long, const char *(*)(unsigned long), unsigned char *);
79 static void dump_segs(void);
80 static void dump_sods(void);
81 static void dump_sym(const struct nlist *);
82 static void dump_syms(void);
83
84 static void dump_rtsyms(void);
85
86 static const char *rtsym_name(unsigned long);
87 static const char *sym_name(unsigned long);
88
89 #ifdef STANDALONE
90 static
91 #endif
92 int error_count;
93
94 /*
95 * Variables ending in _base are pointers to things in our address space,
96 * i.e., in the file itself.
97 *
98 * Variables ending in _addr are adjusted according to where things would
99 * actually appear in memory if the file were loaded.
100 */
101 static const char *file_base;
102 static const char *text_base;
103 static const char *data_base;
104 static const struct relocation_info *rel_base;
105 static const struct nlist *sym_base;
106 static const char *str_base;
107
108 static const struct relocation_info *rtrel_base;
109 static const struct nzlist *rtsym_base;
110 static const char *rtstr_base;
111
112 static const struct exec *ex;
113 static const struct _dynamic *dyn;
114 static const struct section_dispatch_table *sdt;
115
116 static const char *text_addr;
117 static const char *data_addr;
118
119 static unsigned long rel_count;
120 static unsigned long sym_count;
121
122 static unsigned long rtrel_count;
123 static unsigned long rtsym_count;
124
125 /* Dynamically allocated flags, 1 byte per symbol, to record whether each
126 symbol was referenced by a relocation entry. */
127 static unsigned char *sym_used;
128 static unsigned char *rtsym_used;
129
130 static unsigned long origin; /* What values are relocated relative to */
131
132 #ifdef STANDALONE
133 int
main(int argc,char * argv[])134 main(int argc, char *argv[])
135 {
136 int i;
137
138 for (i = 1; i < argc; ++i)
139 dump_file(argv[i]);
140
141 return error_count == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
142 }
143 #endif
144
align_struct(const void * expr)145 static inline const void *align_struct(const void *expr)
146 {
147 assert(!(((int)expr) & 3));
148 return expr;
149 }
150
align_long(const void * expr)151 static inline const void *align_long(const void *expr)
152 {
153 assert(!(((int)expr) & 3));
154 return expr;
155 }
156
align_short(const void * expr)157 static inline const void *align_short(const void *expr)
158 {
159 assert(!(((int)expr) & 1));
160 return expr;
161 }
162
163 #ifdef STANDALONE
164 static
165 #endif
166 void
dump_file(const char * fname)167 dump_file(const char *fname)
168 {
169 int fd;
170 struct stat sb;
171 caddr_t objbase;
172
173 if (stat(fname, &sb) == -1) {
174 warnx("cannot stat \"%s\"", fname);
175 ++error_count;
176 return;
177 }
178
179 if ((sb.st_mode & S_IFMT) != S_IFREG) {
180 warnx("\"%s\" is not a regular file", fname);
181 ++error_count;
182 return;
183 }
184
185 if ((fd = open(fname, O_RDONLY, 0)) == -1) {
186 warnx("cannot open \"%s\"", fname);
187 ++error_count;
188 return;
189 }
190
191 objbase = mmap(0, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
192 if (objbase == (caddr_t) -1) {
193 warnx("cannot mmap \"%s\"", fname);
194 ++error_count;
195 close(fd);
196 return;
197 }
198
199 close(fd);
200
201 file_base = (const char *) objbase; /* Makes address arithmetic easier */
202
203 if (IS_ELF(*(const Elf32_Ehdr*) align_struct(file_base))) {
204 warnx("%s: this is an ELF program; use objdump to examine", fname);
205 ++error_count;
206 munmap(objbase, sb.st_size);
207 return;
208 }
209
210 ex = (const struct exec *) align_struct(file_base);
211
212 printf("%s: a_midmag = 0x%lx\n", fname, (long)ex->a_midmag);
213 printf(" magic = 0x%lx = 0%lo, netmagic = 0x%lx = 0%lo\n",
214 (long)N_GETMAGIC(*ex), (long)N_GETMAGIC(*ex),
215 (long)N_GETMAGIC_NET(*ex), (long)N_GETMAGIC_NET(*ex));
216
217 if (N_BADMAG(*ex)) {
218 warnx("%s: bad magic number", fname);
219 ++error_count;
220 munmap(objbase, sb.st_size);
221 return;
222 }
223
224 printf(" a_text = 0x%lx\n", (long)ex->a_text);
225 printf(" a_data = 0x%lx\n", (long)ex->a_data);
226 printf(" a_bss = 0x%lx\n", (long)ex->a_bss);
227 printf(" a_syms = 0x%lx\n", (long)ex->a_syms);
228 printf(" a_entry = 0x%lx\n", (long)ex->a_entry);
229 printf(" a_trsize = 0x%lx\n", (long)ex->a_trsize);
230 printf(" a_drsize = 0x%lx\n", (long)ex->a_drsize);
231
232 text_base = file_base + N_TXTOFF(*ex);
233 data_base = file_base + N_DATOFF(*ex);
234 rel_base = (const struct relocation_info *)
235 align_struct(file_base + N_RELOFF(*ex));
236 sym_base = (const struct nlist *) align_struct(file_base + N_SYMOFF(*ex));
237 str_base = file_base + N_STROFF(*ex);
238
239 rel_count = (ex->a_trsize + ex->a_drsize) / sizeof rel_base[0];
240 assert(rel_count * sizeof rel_base[0] == ex->a_trsize + ex->a_drsize);
241 sym_count = ex->a_syms / sizeof sym_base[0];
242 assert(sym_count * sizeof sym_base[0] == ex->a_syms);
243
244 if (sym_count != 0) {
245 sym_used = (unsigned char *) calloc(sym_count, sizeof(unsigned char));
246 assert(sym_used != NULL);
247 }
248
249 printf(" Entry = 0x%lx\n", (long)ex->a_entry);
250 printf(" Text offset = %x, address = %lx\n", N_TXTOFF(*ex),
251 (long)N_TXTADDR(*ex));
252 printf(" Data offset = %lx, address = %lx\n", (long)N_DATOFF(*ex),
253 (long)N_DATADDR(*ex));
254
255 /*
256 * In an executable program file, everything is relocated relative to
257 * the assumed run-time load address, i.e., N_TXTADDR(*ex), i.e., 0x1000.
258 *
259 * In a shared library file, everything is relocated relative to the
260 * start of the file, i.e., N_TXTOFF(*ex), i.e., 0.
261 *
262 * The way to tell the difference is by looking at ex->a_entry. If it
263 * is >= 0x1000, then we have an executable program. Otherwise, we
264 * have a shared library.
265 *
266 * When a program is executed, the entire file is mapped into memory,
267 * including the a.out header and so forth. But it is not mapped at
268 * address 0; rather it is mapped at address 0x1000. The first page
269 * of the user's address space is left unmapped in order to catch null
270 * pointer dereferences.
271 *
272 * In this program, when we map in an executable program, we have to
273 * simulate the empty page by decrementing our assumed base address by
274 * a pagesize.
275 */
276
277 text_addr = text_base;
278 data_addr = data_base;
279 origin = 0;
280
281 if (ex->a_entry >= PAGE_SIZE) { /* Executable, not a shared library */
282 /*
283 * The fields in the object have already been relocated on the
284 * assumption that the object will be loaded at N_TXTADDR(*ex).
285 * We have to compensate for that.
286 */
287 text_addr -= PAGE_SIZE;
288 data_addr -= PAGE_SIZE;
289 origin = PAGE_SIZE;
290 printf(" Program, origin = %lx\n", origin);
291 } else if (N_GETFLAG(*ex) & EX_DYNAMIC)
292 printf(" Shared library, origin = %lx\n", origin);
293 else
294 printf(" Object file, origin = %lx\n", origin);
295
296 if (N_GETFLAG(*ex) & EX_DYNAMIC) {
297 dyn = (const struct _dynamic *) align_struct(data_base);
298 printf(" Dynamic version = %d\n", dyn->d_version);
299
300 sdt = (const struct section_dispatch_table *)
301 align_struct(text_addr + (unsigned long) dyn->d_un.d_sdt);
302
303 rtrel_base = (const struct relocation_info *)
304 align_struct(text_addr + sdt->sdt_rel);
305 rtrel_count = (sdt->sdt_hash - sdt->sdt_rel) / sizeof rtrel_base[0];
306 assert(rtrel_count * sizeof rtrel_base[0] ==
307 (size_t)(sdt->sdt_hash - sdt->sdt_rel));
308
309 rtsym_base = (const struct nzlist *)
310 align_struct(text_addr + sdt->sdt_nzlist);
311 rtsym_count = (sdt->sdt_strings - sdt->sdt_nzlist) /
312 sizeof rtsym_base[0];
313 assert(rtsym_count * sizeof rtsym_base[0] ==
314 (size_t)(sdt->sdt_strings - sdt->sdt_nzlist));
315
316 if (rtsym_count != 0) {
317 rtsym_used = (unsigned char *) calloc(rtsym_count,
318 sizeof(unsigned char));
319 assert(rtsym_used != NULL);
320 }
321
322 rtstr_base = text_addr + sdt->sdt_strings;
323 }
324
325 dump_segs();
326 dump_sods();
327 dump_rels("Relocations", rel_base, rel_count, sym_name, sym_used);
328 dump_syms();
329
330 dump_rels("Run-time relocations", rtrel_base, rtrel_count, rtsym_name,
331 rtsym_used);
332 dump_rtsyms();
333
334 if (rtsym_used != NULL) {
335 free(rtsym_used);
336 rtsym_used = NULL;
337 }
338 if (sym_used != NULL) {
339 free(sym_used);
340 sym_used = NULL;
341 }
342 munmap(objbase, sb.st_size);
343 }
344
345 static void
dump_rels(const char * label,const struct relocation_info * base,unsigned long count,const char * (* name)(unsigned long),unsigned char * sym_used_flags)346 dump_rels(const char *label, const struct relocation_info *base,
347 unsigned long count, const char *(*name)(unsigned long),
348 unsigned char *sym_used_flags)
349 {
350 unsigned long i;
351
352 printf(" %s:\n", label);
353 for (i = 0; i < count; ++i) {
354 const struct relocation_info *r = &base[i];
355 unsigned int size;
356 char contents[16];
357
358 size = 1u << r->r_length;
359
360 if (origin <= (unsigned long)r->r_address
361 && (unsigned long)r->r_address < origin + ex->a_text + ex->a_data
362 && 1 <= size && size <= 4) {
363 /*
364 * XXX - This can cause unaligned accesses. OK for the
365 * i386, not so for other architectures.
366 */
367 switch (size) {
368 case 1:
369 snprintf(contents, sizeof contents, " [%02x]",
370 *(unsigned const char *)(text_addr + r->r_address));
371 break;
372 case 2:
373 snprintf(contents, sizeof contents, " [%04x]",
374 *(unsigned const short *)
375 align_short(text_addr + r->r_address));
376 break;
377 case 4:
378 snprintf(contents, sizeof contents, "[%08lx]",
379 *(unsigned const long *)
380 align_long(text_addr + r->r_address));
381 break;
382 }
383 } else
384 snprintf(contents, sizeof contents, " ");
385
386 printf(" %6lu %8x/%u %s %c%c%c%c%c%c", i,
387 r->r_address, size,
388 contents,
389 r->r_extern ? 'e' : '-',
390 r->r_jmptable ? 'j' : '-',
391 r->r_relative ? 'r' : '-',
392 r->r_baserel ? 'b' : '-',
393 r->r_pcrel ? 'p' : '-',
394 r->r_copy ? 'c' : '-');
395
396 if (r->r_extern || r->r_baserel || r->r_jmptable || r->r_copy) {
397 printf(" %4u %s", r->r_symbolnum, name(r->r_symbolnum));
398 sym_used_flags[r->r_symbolnum] = 1;
399 }
400
401 printf("\n");
402 }
403 }
404
405 static void
dump_rtsyms(void)406 dump_rtsyms(void)
407 {
408 unsigned long i;
409
410 printf(" Run-time symbols:\n");
411 for (i = 0; i < rtsym_count; ++i) {
412 printf(" %6lu%c ", i, rtsym_used[i] ? '*' : ' ');
413 dump_sym(&rtsym_base[i].nlist);
414 printf("/%-5ld %s\n", rtsym_base[i].nz_size, rtsym_name(i));
415 }
416 }
417
418 static void
dump_segs(void)419 dump_segs(void)
420 {
421 printf(" Text segment starts at address %lx\n", origin + N_TXTOFF(*ex));
422 if (N_GETFLAG(*ex) & EX_DYNAMIC) {
423 printf(" rel starts at %lx\n", sdt->sdt_rel);
424 printf(" hash starts at %lx\n", sdt->sdt_hash);
425 printf(" nzlist starts at %lx\n", sdt->sdt_nzlist);
426 printf(" strings starts at %lx\n", sdt->sdt_strings);
427 }
428
429 printf(" Data segment starts at address %lx\n", origin + N_DATOFF(*ex));
430 if (N_GETFLAG(*ex) & EX_DYNAMIC) {
431 printf(" _dynamic starts at %lx\n", origin + N_DATOFF(*ex));
432 printf(" so_debug starts at %lx\n", (unsigned long) dyn->d_debug);
433 printf(" sdt starts at %lx\n", (unsigned long) dyn->d_un.d_sdt);
434 printf(" got starts at %lx\n", sdt->sdt_got);
435 printf(" plt starts at %lx\n", sdt->sdt_plt);
436 printf(" rest of stuff starts at %lx\n",
437 sdt->sdt_plt + sdt->sdt_plt_sz);
438 }
439 }
440
441 static void
dump_sods(void)442 dump_sods(void)
443 {
444 long sod_offset;
445 long paths_offset;
446
447 if (dyn == NULL) /* Not a shared object */
448 return;
449
450 sod_offset = sdt->sdt_sods;
451 printf(" Shared object dependencies:\n");
452 while (sod_offset != 0) {
453 const struct sod *sodp = (const struct sod *) align_struct((text_addr + sod_offset));
454 const char *name = (const char *) (text_addr + sodp->sod_name);
455
456 if (sodp->sod_library)
457 printf(" -l%-16s version %d.%d\n", name, sodp->sod_major,
458 sodp->sod_minor);
459 else
460 printf(" %s\n", name);
461 sod_offset = sodp->sod_next;
462 }
463 paths_offset = sdt->sdt_paths;
464 printf(" Shared object additional paths:\n");
465 if (paths_offset != 0) {
466 printf(" %s\n", (const char *)(text_addr + paths_offset));
467 } else {
468 printf(" (none)\n");
469 }
470 }
471
472 static void
dump_sym(const struct nlist * np)473 dump_sym(const struct nlist *np)
474 {
475 char type[8];
476 char aux[8];
477 char weak;
478 char *p;
479
480 switch (np->n_type & ~N_EXT) {
481 case N_UNDF: strcpy(type, "undf"); break;
482 case N_ABS: strcpy(type, "abs"); break;
483 case N_TEXT: strcpy(type, "text"); break;
484 case N_DATA: strcpy(type, "data"); break;
485 case N_BSS: strcpy(type, "bss"); break;
486 case N_INDR: strcpy(type, "indr"); break;
487 case N_SIZE: strcpy(type, "size"); break;
488 case N_COMM: strcpy(type, "comm"); break;
489 case N_SETA: strcpy(type, "seta"); break;
490 case N_SETT: strcpy(type, "sett"); break;
491 case N_SETD: strcpy(type, "setd"); break;
492 case N_SETB: strcpy(type, "setb"); break;
493 case N_SETV: strcpy(type, "setv"); break;
494 case N_FN: strcpy(type, np->n_type&N_EXT ? "fn" : "warn"); break;
495 case N_GSYM: strcpy(type, "gsym"); break;
496 case N_FNAME: strcpy(type, "fname"); break;
497 case N_FUN: strcpy(type, "fun"); break;
498 case N_STSYM: strcpy(type, "stsym"); break;
499 case N_LCSYM: strcpy(type, "lcsym"); break;
500 case N_MAIN: strcpy(type, "main"); break;
501 case N_PC: strcpy(type, "pc"); break;
502 case N_RSYM: strcpy(type, "rsym"); break;
503 case N_SLINE: strcpy(type, "sline"); break;
504 case N_DSLINE: strcpy(type, "dsline"); break;
505 case N_BSLINE: strcpy(type, "bsline"); break;
506 case N_SSYM: strcpy(type, "ssym"); break;
507 case N_SO: strcpy(type, "so"); break;
508 case N_LSYM: strcpy(type, "lsym"); break;
509 case N_BINCL: strcpy(type, "bincl"); break;
510 case N_SOL: strcpy(type, "sol"); break;
511 case N_PSYM: strcpy(type, "psym"); break;
512 case N_EINCL: strcpy(type, "eincl"); break;
513 case N_ENTRY: strcpy(type, "entry"); break;
514 case N_LBRAC: strcpy(type, "lbrac"); break;
515 case N_EXCL: strcpy(type, "excl"); break;
516 case N_RBRAC: strcpy(type, "rbrac"); break;
517 case N_BCOMM: strcpy(type, "bcomm"); break;
518 case N_ECOMM: strcpy(type, "ecomm"); break;
519 case N_ECOML: strcpy(type, "ecoml"); break;
520 case N_LENG: strcpy(type, "leng"); break;
521 default:
522 snprintf(type, sizeof type, "%#02x", np->n_type);
523 break;
524 }
525
526 if (np->n_type & N_EXT && type[0] != '0')
527 for (p = type; *p != '\0'; ++p)
528 *p = toupper(*p);
529
530 switch (N_AUX(np)) {
531 case 0: strcpy(aux, ""); break;
532 case AUX_OBJECT: strcpy(aux, "objt"); break;
533 case AUX_FUNC: strcpy(aux, "func"); break;
534 default: snprintf(aux, sizeof aux, "%#01x", N_AUX(np)); break;
535 }
536
537 weak = N_BIND(np) == BIND_WEAK ? 'w' : ' ';
538
539 printf("%c%-6s %-4s %8lx", weak, type, aux, np->n_value);
540 }
541
542 static void
dump_syms(void)543 dump_syms(void)
544 {
545 unsigned long i;
546
547 printf(" Symbols:\n");
548 for (i = 0; i < sym_count; ++i) {
549 printf(" %6lu%c ", i, sym_used[i] ? '*' : ' ');
550 dump_sym(&sym_base[i]);
551 printf(" %s\n", sym_name(i));
552 }
553 }
554
555 static const char *
rtsym_name(unsigned long n)556 rtsym_name(unsigned long n)
557 {
558 assert(n < rtsym_count);
559 if (rtsym_base[n].nz_strx == 0)
560 return "";
561 return rtstr_base + rtsym_base[n].nz_strx;
562 }
563
564 static const char *
sym_name(unsigned long n)565 sym_name(unsigned long n)
566 {
567 assert(n < sym_count);
568 if (sym_base[n].n_un.n_strx == 0)
569 return "";
570 return str_base + sym_base[n].n_un.n_strx;
571 }
572