cfd23479 |
1 | #include <stdio.h> |
2 | #include <stdlib.h> |
3 | #include <string.h> |
4 | #include <linux/coff.h> |
5 | #include <assert.h> |
6 | #include <stdint.h> |
7 | |
ede51255 |
8 | #include "my_assert.h" |
9 | |
cfd23479 |
10 | /* http://www.delorie.com/djgpp/doc/coff/ */ |
11 | |
12 | typedef struct { |
13 | unsigned short f_magic; /* magic number */ |
14 | unsigned short f_nscns; /* number of sections */ |
15 | unsigned int f_timdat; /* time & date stamp */ |
16 | unsigned int f_symptr; /* file pointer to symtab */ |
17 | unsigned int f_nsyms; /* number of symtab entries */ |
18 | unsigned short f_opthdr; /* sizeof(optional hdr) */ |
19 | unsigned short f_flags; /* flags */ |
20 | } FILHDR; |
21 | |
22 | typedef struct { |
23 | unsigned short magic; /* type of file */ |
24 | unsigned short vstamp; /* version stamp */ |
25 | unsigned int tsize; /* text size in bytes, padded to FW bdry*/ |
26 | unsigned int dsize; /* initialized data " " */ |
27 | unsigned int bsize; /* uninitialized data " " */ |
28 | unsigned int entry; /* entry pt. */ |
29 | unsigned int text_start; /* base of text used for this file */ |
30 | unsigned int data_start; /* base of data used for this file */ |
31 | } AOUTHDR; |
32 | |
33 | typedef struct { |
34 | char s_name[8]; /* section name */ |
35 | unsigned int s_paddr; /* physical address, aliased s_nlib */ |
36 | unsigned int s_vaddr; /* virtual address */ |
37 | unsigned int s_size; /* section size */ |
38 | unsigned int s_scnptr; /* file ptr to raw data for section */ |
39 | unsigned int s_relptr; /* file ptr to relocation */ |
40 | unsigned int s_lnnoptr; /* file ptr to line numbers */ |
41 | unsigned short s_nreloc; /* number of relocation entries */ |
42 | unsigned short s_nlnno; /* number of line number entries */ |
43 | unsigned int s_flags; /* flags */ |
44 | } SCNHDR; |
45 | |
46 | typedef struct { |
47 | unsigned int r_vaddr; /* address of relocation */ |
48 | unsigned int r_symndx; /* symbol we're adjusting for */ |
49 | unsigned short r_type; /* type of relocation */ |
50 | } __attribute__((packed)) RELOC; |
51 | |
e86c9ee6 |
52 | typedef struct { |
53 | union { |
54 | char e_name[E_SYMNMLEN]; |
55 | struct { |
56 | unsigned int e_zeroes; |
57 | unsigned int e_offset; |
58 | } e; |
59 | } e; |
60 | unsigned int e_value; |
61 | short e_scnum; |
62 | unsigned short e_type; |
63 | unsigned char e_sclass; |
64 | unsigned char e_numaux; |
65 | } __attribute__((packed)) SYMENT; |
66 | |
67 | #define C_EXT 2 |
68 | |
69 | struct my_symtab { |
70 | unsigned int addr; |
71 | unsigned int fpos; // for patching |
72 | char *name; |
73 | }; |
74 | |
e86c9ee6 |
75 | static int symt_cmp(const void *p1_, const void *p2_) |
76 | { |
77 | const struct my_symtab *p1 = p1_, *p2 = p2_; |
78 | return p1->addr - p2->addr; |
79 | } |
80 | |
cfd23479 |
81 | void parse_headers(FILE *f, unsigned int *base_out, |
82 | long *sect_ofs, uint8_t **sect_data, long *sect_sz, |
e86c9ee6 |
83 | RELOC **relocs, long *reloc_cnt, |
84 | struct my_symtab **symtab_out, long *sym_cnt) |
cfd23479 |
85 | { |
e86c9ee6 |
86 | struct my_symtab *symt_o = NULL; |
87 | char *stringtab = NULL; |
cfd23479 |
88 | unsigned int base = 0; |
e86c9ee6 |
89 | int text_scnum = 0; |
90 | long filesize; |
91 | char symname[9]; |
cfd23479 |
92 | long opthdr_pos; |
93 | long reloc_size; |
94 | FILHDR hdr; |
95 | AOUTHDR opthdr; |
96 | SCNHDR scnhdr; |
e86c9ee6 |
97 | SYMENT syment; |
98 | int i, s, val; |
cfd23479 |
99 | int ret; |
100 | |
e86c9ee6 |
101 | ret = fseek(f, 0, SEEK_END); |
102 | my_assert(ret, 0); |
103 | |
104 | filesize = ftell(f); |
105 | |
106 | ret = fseek(f, 0, SEEK_SET); |
107 | my_assert(ret, 0); |
108 | |
cfd23479 |
109 | ret = fread(&hdr, 1, sizeof(hdr), f); |
110 | my_assert(ret, sizeof(hdr)); |
111 | |
112 | if (hdr.f_magic == 0x5a4d) // MZ |
113 | { |
114 | ret = fseek(f, 0x3c, SEEK_SET); |
115 | my_assert(ret, 0); |
116 | ret = fread(&val, 1, sizeof(val), f); |
117 | my_assert(ret, sizeof(val)); |
118 | |
119 | ret = fseek(f, val, SEEK_SET); |
120 | my_assert(ret, 0); |
121 | ret = fread(&val, 1, sizeof(val), f); |
122 | my_assert(ret, sizeof(val)); |
123 | my_assert(val, 0x4550); // PE |
124 | |
125 | // should be COFF now |
126 | ret = fread(&hdr, 1, sizeof(hdr), f); |
127 | my_assert(ret, sizeof(hdr)); |
128 | } |
129 | |
130 | my_assert(hdr.f_magic, COFF_I386MAGIC); |
131 | |
132 | if (hdr.f_opthdr != 0) |
133 | { |
134 | opthdr_pos = ftell(f); |
135 | |
136 | if (hdr.f_opthdr < sizeof(opthdr)) |
137 | my_assert(1, 0); |
138 | |
139 | ret = fread(&opthdr, 1, sizeof(opthdr), f); |
140 | my_assert(ret, sizeof(opthdr)); |
141 | my_assert(opthdr.magic, COFF_ZMAGIC); |
142 | |
143 | printf("text_start: %x\n", opthdr.text_start); |
144 | |
145 | if (hdr.f_opthdr > sizeof(opthdr)) { |
146 | ret = fread(&base, 1, sizeof(base), f); |
147 | my_assert(ret, sizeof(base)); |
148 | printf("base: %x\n", base); |
149 | } |
150 | ret = fseek(f, opthdr_pos + hdr.f_opthdr, SEEK_SET); |
151 | my_assert(ret, 0); |
152 | } |
153 | |
e86c9ee6 |
154 | // note: assuming first non-empty one is .text .. |
cfd23479 |
155 | for (s = 0; s < hdr.f_nscns; s++) { |
156 | ret = fread(&scnhdr, 1, sizeof(scnhdr), f); |
157 | my_assert(ret, sizeof(scnhdr)); |
158 | |
e86c9ee6 |
159 | if (scnhdr.s_size != 0) { |
160 | text_scnum = s + 1; |
cfd23479 |
161 | break; |
e86c9ee6 |
162 | } |
cfd23479 |
163 | } |
164 | |
e86c9ee6 |
165 | printf("f_nsyms: %x\n", hdr.f_nsyms); |
cfd23479 |
166 | printf("s_name: '%s'\n", scnhdr.s_name); |
167 | printf("s_vaddr: %x\n", scnhdr.s_vaddr); |
168 | printf("s_size: %x\n", scnhdr.s_size); |
e86c9ee6 |
169 | //printf("s_scnptr: %x\n", scnhdr.s_scnptr); |
cfd23479 |
170 | printf("s_nreloc: %x\n", scnhdr.s_nreloc); |
171 | printf("--\n"); |
172 | |
173 | ret = fseek(f, scnhdr.s_scnptr, SEEK_SET); |
174 | my_assert(ret, 0); |
175 | |
176 | *sect_data = malloc(scnhdr.s_size); |
177 | my_assert_not(*sect_data, NULL); |
178 | ret = fread(*sect_data, 1, scnhdr.s_size, f); |
179 | my_assert(ret, scnhdr.s_size); |
180 | |
181 | *sect_ofs = scnhdr.s_scnptr; |
182 | *sect_sz = scnhdr.s_size; |
183 | |
e86c9ee6 |
184 | // relocs |
cfd23479 |
185 | ret = fseek(f, scnhdr.s_relptr, SEEK_SET); |
186 | my_assert(ret, 0); |
187 | |
188 | reloc_size = scnhdr.s_nreloc * sizeof((*relocs)[0]); |
189 | *relocs = malloc(reloc_size + 1); |
190 | my_assert_not(*relocs, NULL); |
191 | ret = fread(*relocs, 1, reloc_size, f); |
192 | my_assert(ret, reloc_size); |
193 | |
194 | *reloc_cnt = scnhdr.s_nreloc; |
195 | |
e86c9ee6 |
196 | // symtab |
197 | if (hdr.f_nsyms != 0) { |
198 | symname[8] = 0; |
199 | |
200 | symt_o = malloc(hdr.f_nsyms * sizeof(symt_o[0]) + 1); |
201 | my_assert_not(symt_o, NULL); |
202 | |
203 | ret = fseek(f, hdr.f_symptr |
204 | + hdr.f_nsyms * sizeof(syment), SEEK_SET); |
205 | my_assert(ret, 0); |
206 | ret = fread(&i, 1, sizeof(i), f); |
207 | my_assert(ret, sizeof(i)); |
208 | my_assert((unsigned int)i < filesize, 1); |
209 | |
210 | stringtab = malloc(i); |
211 | my_assert_not(stringtab, NULL); |
212 | memset(stringtab, 0, 4); |
213 | ret = fread(stringtab + 4, 1, i - 4, f); |
214 | my_assert(ret, i - 4); |
215 | |
216 | ret = fseek(f, hdr.f_symptr, SEEK_SET); |
217 | my_assert(ret, 0); |
218 | } |
219 | |
220 | for (i = s = 0; i < hdr.f_nsyms; i++) { |
221 | long pos = ftell(f); |
222 | |
223 | ret = fread(&syment, 1, sizeof(syment), f); |
224 | my_assert(ret, sizeof(syment)); |
225 | |
226 | strncpy(symname, syment.e.e_name, 8); |
227 | //printf("%3d %2d %08x '%s'\n", syment.e_sclass, |
228 | // syment.e_scnum, syment.e_value, symname); |
229 | |
230 | if (syment.e_scnum != text_scnum || syment.e_sclass != C_EXT) |
231 | continue; |
232 | |
233 | symt_o[s].addr = syment.e_value; |
234 | symt_o[s].fpos = pos; |
235 | if (syment.e.e.e_zeroes == 0) |
236 | symt_o[s].name = stringtab + syment.e.e.e_offset; |
237 | else |
238 | symt_o[s].name = strdup(symname); |
239 | s++; |
240 | |
241 | if (syment.e_numaux) { |
242 | ret = fseek(f, syment.e_numaux * sizeof(syment), |
243 | SEEK_CUR); |
244 | my_assert(ret, 0); |
245 | i += syment.e_numaux; |
246 | } |
247 | } |
248 | |
249 | if (symt_o != NULL) |
250 | qsort(symt_o, s, sizeof(symt_o[0]), symt_cmp); |
251 | |
252 | *sym_cnt = s; |
253 | *symtab_out = symt_o; |
254 | |
255 | if (base != 0 && base_out != NULL) |
cfd23479 |
256 | *base_out = base + scnhdr.s_vaddr; |
257 | } |
258 | |
259 | static int handle_pad(uint8_t *d_obj, uint8_t *d_exe, int maxlen) |
260 | { |
261 | static const uint8_t p7[7] = { 0x8d, 0xa4, 0x24, 0x00, 0x00, 0x00, 0x00 }; |
262 | static const uint8_t p6[6] = { 0x8d, 0x9b, 0x00, 0x00, 0x00, 0x00 }; |
263 | static const uint8_t p5[5] = { 0x05, 0x00, 0x00, 0x00, 0x00 }; |
264 | static const uint8_t p4[4] = { 0x8d, 0x64, 0x24, 0x00 }; |
265 | static const uint8_t p3[3] = { 0x8d, 0x49, 0x00 }; |
266 | static const uint8_t p2[2] = { 0x8b, 0xff }; |
267 | static const uint8_t p1[1] = { 0x90 }; |
268 | int len; |
269 | int i; |
270 | |
271 | for (i = 0; i < maxlen; i++) |
272 | if (d_exe[i] != 0xcc) |
273 | break; |
274 | |
275 | for (len = i; len > 0; ) |
276 | { |
277 | i = len; |
278 | if (i > 7) |
279 | i = 7; |
280 | |
281 | switch (i) { |
282 | #define CASE(x) \ |
283 | case sizeof(p ## x): \ |
284 | if (memcmp(d_obj, p ## x, sizeof(p ## x))) \ |
285 | return 0; \ |
286 | memset(d_obj, 0xcc, sizeof(p ## x)); \ |
287 | break; |
288 | CASE(7) |
289 | CASE(6) |
290 | CASE(5) |
291 | CASE(4) |
292 | CASE(3) |
293 | CASE(2) |
294 | CASE(1) |
295 | default: |
296 | printf("%s: unhandled len: %d\n", __func__, len); |
297 | return 0; |
298 | #undef CASE |
299 | } |
300 | |
301 | len -= i; |
302 | d_obj += i; |
303 | } |
304 | |
305 | return 1; |
306 | } |
307 | |
308 | struct equiv_opcode { |
309 | signed char len; |
310 | signed char ofs; |
311 | short cmp_rm; |
312 | uint8_t v_masm[8]; |
313 | uint8_t v_masm_mask[8]; |
314 | uint8_t v_msvc[8]; |
315 | uint8_t v_msvc_mask[8]; |
316 | } equiv_ops[] = { |
317 | // cmp $0x11,%ax |
318 | { 4, -1, 0, |
319 | { 0x66,0x83,0xf8,0x03 }, { 0xff,0xff,0xff,0x00 }, |
320 | { 0x66,0x3d,0x03,0x00 }, { 0xff,0xff,0x00,0xff }, }, |
321 | // lea -0x1(%ebx,%eax,1),%esi // op mod/rm sib offs |
322 | // mov, test, imm grp 1 |
323 | { 3, -2, 1, |
324 | { 0x8d,0x74,0x03 }, { 0xf0,0x07,0xc0 }, |
325 | { 0x8d,0x74,0x18 }, { 0xf0,0x07,0xc0 }, }, |
326 | // movzbl 0x58f24a(%eax,%ecx,1),%eax |
327 | { 4, -3, 1, |
328 | { 0x0f,0xb6,0x84,0x08 }, { 0xff,0xff,0x07,0xc0 }, |
329 | { 0x0f,0xb6,0x84,0x01 }, { 0xff,0xff,0x07,0xc0 }, }, |
330 | // inc/dec |
331 | { 3, -2, 1, |
332 | { 0xfe,0x4c,0x03 }, { 0xfe,0xff,0xc0 }, |
333 | { 0xfe,0x4c,0x18 }, { 0xfe,0xff,0xc0 }, }, |
334 | // cmp |
335 | { 3, -2, 1, |
336 | { 0x38,0x0c,0x0c }, { 0xff,0xff,0xc0 }, |
337 | { 0x38,0x0c,0x30 }, { 0xff,0xff,0xc0 }, }, |
338 | // test %dl,%bl |
339 | { 2, -1, 1, |
340 | { 0x84,0xd3 }, { 0xfe,0xc0 }, |
341 | { 0x84,0xda }, { 0xfe,0xc0 }, }, |
342 | // cmp r,r/m vs rm/r |
343 | { 2, 0, 1, |
344 | { 0x3a,0xca }, { 0xff,0xc0 }, |
345 | { 0x38,0xd1 }, { 0xff,0xc0 }, }, |
346 | // rep + 66 prefix |
347 | { 2, 0, 0, |
348 | { 0xf3,0x66 }, { 0xfe,0xff }, |
349 | { 0x66,0xf3 }, { 0xff,0xfe }, }, |
350 | // fadd st, st(0) vs st(0), st |
351 | { 2, 0, 0, |
352 | { 0xd8,0xc0 }, { 0xff,0xf7 }, |
353 | { 0xdc,0xc0 }, { 0xff,0xf7 }, }, |
354 | |
355 | // broad filters (may take too much..) |
356 | // testb $0x4,0x1d(%esi,%eax,1) |
357 | // movb, push, .. |
358 | { 3, -2, 1, |
359 | { 0xf6,0x44,0x06 }, { 0x00,0x07,0xc0 }, |
360 | { 0xf6,0x44,0x30 }, { 0x00,0x07,0xc0 }, }, |
361 | }; |
362 | |
363 | static int cmp_mask(uint8_t *d, uint8_t *expect, uint8_t *mask, int len) |
364 | { |
365 | int i; |
366 | |
367 | for (i = 0; i < len; i++) |
368 | if ((d[i] & mask[i]) != (expect[i] & mask[i])) |
369 | return 1; |
370 | |
371 | return 0; |
372 | } |
373 | |
374 | static int check_equiv(uint8_t *d_obj, uint8_t *d_exe, int maxlen) |
375 | { |
376 | uint8_t vo, ve, vo2, ve2; |
377 | int i, jo, je; |
378 | int len, ofs; |
379 | |
380 | for (i = 0; i < sizeof(equiv_ops) / sizeof(equiv_ops[0]); i++) |
381 | { |
382 | struct equiv_opcode *op = &equiv_ops[i]; |
383 | |
384 | len = op->len; |
385 | if (maxlen < len) |
386 | continue; |
387 | |
388 | ofs = op->ofs; |
389 | if (cmp_mask(d_obj + ofs, op->v_masm, |
390 | op->v_masm_mask, len)) |
391 | continue; |
392 | if (cmp_mask(d_exe + ofs, op->v_msvc, |
393 | op->v_msvc_mask, len)) |
394 | continue; |
395 | |
396 | jo = je = 0; |
397 | d_obj += ofs; |
398 | d_exe += ofs; |
399 | while (1) |
400 | { |
401 | for (; jo < len; jo++) |
402 | if (op->v_masm_mask[jo] != 0xff) |
403 | break; |
404 | for (; je < len; je++) |
405 | if (op->v_msvc_mask[je] != 0xff) |
406 | break; |
407 | |
408 | if ((jo == len && je != len) || (jo != len && je == len)) { |
409 | printf("invalid equiv_ops\n"); |
410 | return -1; |
411 | } |
412 | if (jo == len) |
413 | return len + ofs - 1; // matched |
414 | |
415 | // var byte |
416 | vo = d_obj[jo] & ~op->v_masm_mask[jo]; |
417 | ve = d_exe[je] & ~op->v_msvc_mask[je]; |
418 | if (op->cmp_rm && op->v_masm_mask[jo] == 0xc0) { |
419 | vo2 = vo >> 3; |
420 | vo &= 7; |
421 | ve2 = ve & 7; |
422 | ve >>= 3; |
423 | if (vo != ve || vo2 != ve2) |
424 | return -1; |
425 | } |
426 | else { |
427 | if (vo != ve) |
428 | return -1; |
429 | } |
430 | |
431 | jo++; |
432 | je++; |
433 | } |
434 | } |
435 | |
436 | return -1; |
437 | } |
438 | |
439 | int main(int argc, char *argv[]) |
440 | { |
441 | FILE *f_obj, *f_exe; |
442 | long text_ofs_obj, text_ofs_exe; |
443 | long sztext_obj, sztext_exe, sztext_cmn; |
444 | RELOC *relocs_obj, *relocs_exe; |
e86c9ee6 |
445 | long reloc_cnt_obj, reloc_cnt_exe; |
446 | struct my_symtab *syms_obj, *syms_exe; |
447 | long sym_cnt_obj, sym_cnt_exe; |
cfd23479 |
448 | uint8_t *d_obj, *d_exe; |
e86c9ee6 |
449 | unsigned int base = 0; |
cfd23479 |
450 | int retval = 1; |
451 | int left; |
452 | int ret; |
453 | int i; |
454 | |
455 | if (argc != 3) { |
e86c9ee6 |
456 | printf("usage:\n%s <a_obj> <exe>\n", argv[0]); |
cfd23479 |
457 | return 1; |
458 | } |
459 | |
460 | f_obj = fopen(argv[1], "r+b"); |
461 | if (f_obj == NULL) { |
462 | fprintf(stderr, "%s", argv[1]); |
463 | perror(""); |
464 | return 1; |
465 | } |
466 | |
467 | f_exe = fopen(argv[2], "r"); |
468 | if (f_exe == NULL) { |
e86c9ee6 |
469 | fprintf(stderr, "%s", argv[2]); |
cfd23479 |
470 | perror(""); |
471 | return 1; |
472 | } |
473 | |
e86c9ee6 |
474 | parse_headers(f_obj, NULL, &text_ofs_obj, &d_obj, &sztext_obj, |
475 | &relocs_obj, &reloc_cnt_obj, &syms_obj, &sym_cnt_obj); |
cfd23479 |
476 | parse_headers(f_exe, &base, &text_ofs_exe, &d_exe, &sztext_exe, |
e86c9ee6 |
477 | &relocs_exe, &reloc_cnt_exe, &syms_exe, &sym_cnt_exe); |
cfd23479 |
478 | |
479 | sztext_cmn = sztext_obj; |
480 | if (sztext_cmn > sztext_exe) |
481 | sztext_cmn = sztext_exe; |
cfd23479 |
482 | |
483 | if (sztext_cmn == 0) { |
484 | printf("bad .text size(s): %ld, %ld\n", |
485 | sztext_obj, sztext_exe); |
486 | return 1; |
487 | } |
488 | |
e86c9ee6 |
489 | for (i = 0; i < reloc_cnt_obj; i++) |
cfd23479 |
490 | { |
491 | unsigned int a = relocs_obj[i].r_vaddr; |
492 | //printf("%04x %08x\n", relocs_obj[i].r_type, a); |
493 | |
494 | switch (relocs_obj[i].r_type) { |
495 | case 0x06: |
496 | memset(d_obj + a, 0, 4); |
497 | memset(d_exe + a, 0, 4); |
498 | break; |
499 | default: |
500 | printf("unknown reloc %x @%08x\n", |
501 | relocs_obj[i].r_type, base + a); |
502 | return 1; |
503 | } |
504 | } |
505 | |
506 | for (i = 0; i < sztext_cmn; i++) |
507 | { |
508 | if (d_obj[i] == d_exe[i]) |
509 | continue; |
510 | |
511 | left = sztext_cmn - i; |
512 | |
513 | if (d_exe[i] == 0xcc) { // padding |
514 | if (handle_pad(d_obj + i, d_exe + i, left)) |
515 | continue; |
516 | } |
517 | |
518 | ret = check_equiv(d_obj + i, d_exe + i, left); |
519 | if (ret >= 0) { |
520 | i += ret; |
521 | continue; |
522 | } |
523 | |
524 | printf("%x: %02x vs %02x\n", base + i, d_obj[i], d_exe[i]); |
525 | goto out; |
526 | } |
527 | |
528 | out: |
529 | return retval; |
530 | } |