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dcc914f4 JP |
1 | /* |
2 | * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version 2 | |
7 | * of the License, or (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, see <http://www.gnu.org/licenses/>. | |
16 | */ | |
17 | ||
18 | #include <string.h> | |
19 | #include <stdlib.h> | |
20 | ||
21 | #include "check.h" | |
22 | #include "elf.h" | |
23 | #include "special.h" | |
24 | #include "arch.h" | |
25 | #include "warn.h" | |
26 | ||
27 | #include <linux/hashtable.h> | |
28 | #include <linux/kernel.h> | |
29 | ||
dcc914f4 JP |
30 | struct alternative { |
31 | struct list_head list; | |
32 | struct instruction *insn; | |
33 | }; | |
34 | ||
35 | const char *objname; | |
36 | static bool nofp; | |
baa41469 | 37 | struct cfi_state initial_func_cfi; |
dcc914f4 JP |
38 | |
39 | static struct instruction *find_insn(struct objtool_file *file, | |
40 | struct section *sec, unsigned long offset) | |
41 | { | |
42 | struct instruction *insn; | |
43 | ||
44 | hash_for_each_possible(file->insn_hash, insn, hash, offset) | |
45 | if (insn->sec == sec && insn->offset == offset) | |
46 | return insn; | |
47 | ||
48 | return NULL; | |
49 | } | |
50 | ||
51 | static struct instruction *next_insn_same_sec(struct objtool_file *file, | |
52 | struct instruction *insn) | |
53 | { | |
54 | struct instruction *next = list_next_entry(insn, list); | |
55 | ||
baa41469 | 56 | if (!next || &next->list == &file->insn_list || next->sec != insn->sec) |
dcc914f4 JP |
57 | return NULL; |
58 | ||
59 | return next; | |
60 | } | |
61 | ||
62 | static bool gcov_enabled(struct objtool_file *file) | |
63 | { | |
64 | struct section *sec; | |
65 | struct symbol *sym; | |
66 | ||
baa41469 | 67 | for_each_sec(file, sec) |
dcc914f4 JP |
68 | list_for_each_entry(sym, &sec->symbol_list, list) |
69 | if (!strncmp(sym->name, "__gcov_.", 8)) | |
70 | return true; | |
71 | ||
72 | return false; | |
73 | } | |
74 | ||
dcc914f4 JP |
75 | #define func_for_each_insn(file, func, insn) \ |
76 | for (insn = find_insn(file, func->sec, func->offset); \ | |
77 | insn && &insn->list != &file->insn_list && \ | |
78 | insn->sec == func->sec && \ | |
79 | insn->offset < func->offset + func->len; \ | |
80 | insn = list_next_entry(insn, list)) | |
81 | ||
82 | #define func_for_each_insn_continue_reverse(file, func, insn) \ | |
83 | for (insn = list_prev_entry(insn, list); \ | |
84 | &insn->list != &file->insn_list && \ | |
85 | insn->sec == func->sec && insn->offset >= func->offset; \ | |
86 | insn = list_prev_entry(insn, list)) | |
87 | ||
88 | #define sec_for_each_insn_from(file, insn) \ | |
89 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
90 | ||
baa41469 JP |
91 | #define sec_for_each_insn_continue(file, insn) \ |
92 | for (insn = next_insn_same_sec(file, insn); insn; \ | |
93 | insn = next_insn_same_sec(file, insn)) | |
dcc914f4 JP |
94 | |
95 | /* | |
96 | * Check if the function has been manually whitelisted with the | |
97 | * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted | |
98 | * due to its use of a context switching instruction. | |
99 | */ | |
100 | static bool ignore_func(struct objtool_file *file, struct symbol *func) | |
101 | { | |
102 | struct rela *rela; | |
2513cbf9 | 103 | struct instruction *insn; |
dcc914f4 JP |
104 | |
105 | /* check for STACK_FRAME_NON_STANDARD */ | |
106 | if (file->whitelist && file->whitelist->rela) | |
107 | list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) { | |
108 | if (rela->sym->type == STT_SECTION && | |
109 | rela->sym->sec == func->sec && | |
110 | rela->addend == func->offset) | |
111 | return true; | |
112 | if (rela->sym->type == STT_FUNC && rela->sym == func) | |
113 | return true; | |
114 | } | |
115 | ||
2513cbf9 JP |
116 | /* check if it has a context switching instruction */ |
117 | func_for_each_insn(file, func, insn) | |
118 | if (insn->type == INSN_CONTEXT_SWITCH) | |
119 | return true; | |
120 | ||
dcc914f4 JP |
121 | return false; |
122 | } | |
123 | ||
124 | /* | |
125 | * This checks to see if the given function is a "noreturn" function. | |
126 | * | |
127 | * For global functions which are outside the scope of this object file, we | |
128 | * have to keep a manual list of them. | |
129 | * | |
130 | * For local functions, we have to detect them manually by simply looking for | |
131 | * the lack of a return instruction. | |
132 | * | |
133 | * Returns: | |
134 | * -1: error | |
135 | * 0: no dead end | |
136 | * 1: dead end | |
137 | */ | |
138 | static int __dead_end_function(struct objtool_file *file, struct symbol *func, | |
139 | int recursion) | |
140 | { | |
141 | int i; | |
142 | struct instruction *insn; | |
143 | bool empty = true; | |
144 | ||
145 | /* | |
146 | * Unfortunately these have to be hard coded because the noreturn | |
147 | * attribute isn't provided in ELF data. | |
148 | */ | |
149 | static const char * const global_noreturns[] = { | |
150 | "__stack_chk_fail", | |
151 | "panic", | |
152 | "do_exit", | |
153 | "do_task_dead", | |
154 | "__module_put_and_exit", | |
155 | "complete_and_exit", | |
156 | "kvm_spurious_fault", | |
157 | "__reiserfs_panic", | |
158 | "lbug_with_loc", | |
159 | "fortify_panic", | |
160 | }; | |
161 | ||
162 | if (func->bind == STB_WEAK) | |
163 | return 0; | |
164 | ||
165 | if (func->bind == STB_GLOBAL) | |
166 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
167 | if (!strcmp(func->name, global_noreturns[i])) | |
168 | return 1; | |
169 | ||
170 | if (!func->sec) | |
171 | return 0; | |
172 | ||
173 | func_for_each_insn(file, func, insn) { | |
174 | empty = false; | |
175 | ||
176 | if (insn->type == INSN_RETURN) | |
177 | return 0; | |
178 | } | |
179 | ||
180 | if (empty) | |
181 | return 0; | |
182 | ||
183 | /* | |
184 | * A function can have a sibling call instead of a return. In that | |
185 | * case, the function's dead-end status depends on whether the target | |
186 | * of the sibling call returns. | |
187 | */ | |
188 | func_for_each_insn(file, func, insn) { | |
189 | if (insn->sec != func->sec || | |
190 | insn->offset >= func->offset + func->len) | |
191 | break; | |
192 | ||
193 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { | |
194 | struct instruction *dest = insn->jump_dest; | |
195 | struct symbol *dest_func; | |
196 | ||
197 | if (!dest) | |
198 | /* sibling call to another file */ | |
199 | return 0; | |
200 | ||
201 | if (dest->sec != func->sec || | |
202 | dest->offset < func->offset || | |
203 | dest->offset >= func->offset + func->len) { | |
204 | /* local sibling call */ | |
205 | dest_func = find_symbol_by_offset(dest->sec, | |
206 | dest->offset); | |
207 | if (!dest_func) | |
208 | continue; | |
209 | ||
210 | if (recursion == 5) { | |
211 | WARN_FUNC("infinite recursion (objtool bug!)", | |
212 | dest->sec, dest->offset); | |
213 | return -1; | |
214 | } | |
215 | ||
216 | return __dead_end_function(file, dest_func, | |
217 | recursion + 1); | |
218 | } | |
219 | } | |
220 | ||
221 | if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts)) | |
222 | /* sibling call */ | |
223 | return 0; | |
224 | } | |
225 | ||
226 | return 1; | |
227 | } | |
228 | ||
229 | static int dead_end_function(struct objtool_file *file, struct symbol *func) | |
230 | { | |
231 | return __dead_end_function(file, func, 0); | |
232 | } | |
233 | ||
baa41469 JP |
234 | static void clear_insn_state(struct insn_state *state) |
235 | { | |
236 | int i; | |
237 | ||
238 | memset(state, 0, sizeof(*state)); | |
239 | state->cfa.base = CFI_UNDEFINED; | |
240 | for (i = 0; i < CFI_NUM_REGS; i++) | |
241 | state->regs[i].base = CFI_UNDEFINED; | |
242 | state->drap_reg = CFI_UNDEFINED; | |
243 | } | |
244 | ||
dcc914f4 JP |
245 | /* |
246 | * Call the arch-specific instruction decoder for all the instructions and add | |
247 | * them to the global instruction list. | |
248 | */ | |
249 | static int decode_instructions(struct objtool_file *file) | |
250 | { | |
251 | struct section *sec; | |
252 | struct symbol *func; | |
253 | unsigned long offset; | |
254 | struct instruction *insn; | |
255 | int ret; | |
256 | ||
baa41469 | 257 | for_each_sec(file, sec) { |
dcc914f4 JP |
258 | |
259 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
260 | continue; | |
261 | ||
262 | for (offset = 0; offset < sec->len; offset += insn->len) { | |
263 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
264 | if (!insn) { |
265 | WARN("malloc failed"); | |
266 | return -1; | |
267 | } | |
dcc914f4 | 268 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 269 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
270 | clear_insn_state(&insn->state); |
271 | ||
dcc914f4 JP |
272 | insn->sec = sec; |
273 | insn->offset = offset; | |
274 | ||
275 | ret = arch_decode_instruction(file->elf, sec, offset, | |
276 | sec->len - offset, | |
277 | &insn->len, &insn->type, | |
baa41469 JP |
278 | &insn->immediate, |
279 | &insn->stack_op); | |
dcc914f4 JP |
280 | if (ret) |
281 | return ret; | |
282 | ||
283 | if (!insn->type || insn->type > INSN_LAST) { | |
284 | WARN_FUNC("invalid instruction type %d", | |
285 | insn->sec, insn->offset, insn->type); | |
286 | return -1; | |
287 | } | |
288 | ||
289 | hash_add(file->insn_hash, &insn->hash, insn->offset); | |
290 | list_add_tail(&insn->list, &file->insn_list); | |
291 | } | |
292 | ||
293 | list_for_each_entry(func, &sec->symbol_list, list) { | |
294 | if (func->type != STT_FUNC) | |
295 | continue; | |
296 | ||
297 | if (!find_insn(file, sec, func->offset)) { | |
298 | WARN("%s(): can't find starting instruction", | |
299 | func->name); | |
300 | return -1; | |
301 | } | |
302 | ||
303 | func_for_each_insn(file, func, insn) | |
304 | if (!insn->func) | |
305 | insn->func = func; | |
306 | } | |
307 | } | |
308 | ||
309 | return 0; | |
310 | } | |
311 | ||
312 | /* | |
313 | * Find all uses of the unreachable() macro, which are code path dead ends. | |
314 | */ | |
315 | static int add_dead_ends(struct objtool_file *file) | |
316 | { | |
317 | struct section *sec; | |
318 | struct rela *rela; | |
319 | struct instruction *insn; | |
320 | bool found; | |
321 | ||
322 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); | |
323 | if (!sec) | |
324 | return 0; | |
325 | ||
326 | list_for_each_entry(rela, &sec->rela_list, list) { | |
327 | if (rela->sym->type != STT_SECTION) { | |
328 | WARN("unexpected relocation symbol type in %s", sec->name); | |
329 | return -1; | |
330 | } | |
331 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
332 | if (insn) | |
333 | insn = list_prev_entry(insn, list); | |
334 | else if (rela->addend == rela->sym->sec->len) { | |
335 | found = false; | |
336 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
337 | if (insn->sec == rela->sym->sec) { | |
338 | found = true; | |
339 | break; | |
340 | } | |
341 | } | |
342 | ||
343 | if (!found) { | |
344 | WARN("can't find unreachable insn at %s+0x%x", | |
345 | rela->sym->sec->name, rela->addend); | |
346 | return -1; | |
347 | } | |
348 | } else { | |
349 | WARN("can't find unreachable insn at %s+0x%x", | |
350 | rela->sym->sec->name, rela->addend); | |
351 | return -1; | |
352 | } | |
353 | ||
354 | insn->dead_end = true; | |
355 | } | |
356 | ||
357 | return 0; | |
358 | } | |
359 | ||
360 | /* | |
361 | * Warnings shouldn't be reported for ignored functions. | |
362 | */ | |
363 | static void add_ignores(struct objtool_file *file) | |
364 | { | |
365 | struct instruction *insn; | |
366 | struct section *sec; | |
367 | struct symbol *func; | |
368 | ||
baa41469 | 369 | for_each_sec(file, sec) { |
dcc914f4 JP |
370 | list_for_each_entry(func, &sec->symbol_list, list) { |
371 | if (func->type != STT_FUNC) | |
372 | continue; | |
373 | ||
374 | if (!ignore_func(file, func)) | |
375 | continue; | |
376 | ||
377 | func_for_each_insn(file, func, insn) | |
baa41469 | 378 | insn->ignore = true; |
dcc914f4 JP |
379 | } |
380 | } | |
381 | } | |
382 | ||
383 | /* | |
384 | * Find the destination instructions for all jumps. | |
385 | */ | |
386 | static int add_jump_destinations(struct objtool_file *file) | |
387 | { | |
388 | struct instruction *insn; | |
389 | struct rela *rela; | |
390 | struct section *dest_sec; | |
391 | unsigned long dest_off; | |
392 | ||
393 | for_each_insn(file, insn) { | |
394 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
395 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
396 | continue; | |
397 | ||
baa41469 | 398 | if (insn->ignore) |
dcc914f4 JP |
399 | continue; |
400 | ||
401 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
402 | insn->len); | |
403 | if (!rela) { | |
404 | dest_sec = insn->sec; | |
405 | dest_off = insn->offset + insn->len + insn->immediate; | |
406 | } else if (rela->sym->type == STT_SECTION) { | |
407 | dest_sec = rela->sym->sec; | |
408 | dest_off = rela->addend + 4; | |
409 | } else if (rela->sym->sec->idx) { | |
410 | dest_sec = rela->sym->sec; | |
411 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
412 | } else { | |
413 | /* sibling call */ | |
414 | insn->jump_dest = 0; | |
415 | continue; | |
416 | } | |
417 | ||
418 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
419 | if (!insn->jump_dest) { | |
420 | ||
421 | /* | |
422 | * This is a special case where an alt instruction | |
423 | * jumps past the end of the section. These are | |
424 | * handled later in handle_group_alt(). | |
425 | */ | |
426 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
427 | continue; | |
428 | ||
429 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
430 | insn->sec, insn->offset, dest_sec->name, | |
431 | dest_off); | |
432 | return -1; | |
433 | } | |
434 | } | |
435 | ||
436 | return 0; | |
437 | } | |
438 | ||
439 | /* | |
440 | * Find the destination instructions for all calls. | |
441 | */ | |
442 | static int add_call_destinations(struct objtool_file *file) | |
443 | { | |
444 | struct instruction *insn; | |
445 | unsigned long dest_off; | |
446 | struct rela *rela; | |
447 | ||
448 | for_each_insn(file, insn) { | |
449 | if (insn->type != INSN_CALL) | |
450 | continue; | |
451 | ||
452 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
453 | insn->len); | |
454 | if (!rela) { | |
455 | dest_off = insn->offset + insn->len + insn->immediate; | |
456 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
457 | dest_off); | |
458 | if (!insn->call_dest) { | |
459 | WARN_FUNC("can't find call dest symbol at offset 0x%lx", | |
460 | insn->sec, insn->offset, dest_off); | |
461 | return -1; | |
462 | } | |
463 | } else if (rela->sym->type == STT_SECTION) { | |
464 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
465 | rela->addend+4); | |
466 | if (!insn->call_dest || | |
467 | insn->call_dest->type != STT_FUNC) { | |
468 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
469 | insn->sec, insn->offset, | |
470 | rela->sym->sec->name, | |
471 | rela->addend + 4); | |
472 | return -1; | |
473 | } | |
474 | } else | |
475 | insn->call_dest = rela->sym; | |
476 | } | |
477 | ||
478 | return 0; | |
479 | } | |
480 | ||
481 | /* | |
482 | * The .alternatives section requires some extra special care, over and above | |
483 | * what other special sections require: | |
484 | * | |
485 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
486 | * instruction at the end so that validate_branch() skips all the original | |
487 | * replaced instructions when validating the new instruction path. | |
488 | * | |
489 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
490 | * that case the old instructions are replaced with noops. We simulate that | |
491 | * by creating a fake jump as the only new instruction. | |
492 | * | |
493 | * 3. In some cases, the alternative section includes an instruction which | |
494 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
495 | * jumps' destinations to point back to .text rather than the end of the | |
496 | * entry in .altinstr_replacement. | |
497 | * | |
498 | * 4. It has been requested that we don't validate the !POPCNT feature path | |
499 | * which is a "very very small percentage of machines". | |
500 | */ | |
501 | static int handle_group_alt(struct objtool_file *file, | |
502 | struct special_alt *special_alt, | |
503 | struct instruction *orig_insn, | |
504 | struct instruction **new_insn) | |
505 | { | |
506 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump; | |
507 | unsigned long dest_off; | |
508 | ||
509 | last_orig_insn = NULL; | |
510 | insn = orig_insn; | |
511 | sec_for_each_insn_from(file, insn) { | |
512 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
513 | break; | |
514 | ||
515 | if (special_alt->skip_orig) | |
516 | insn->type = INSN_NOP; | |
517 | ||
518 | insn->alt_group = true; | |
519 | last_orig_insn = insn; | |
520 | } | |
521 | ||
522 | if (!next_insn_same_sec(file, last_orig_insn)) { | |
523 | WARN("%s: don't know how to handle alternatives at end of section", | |
524 | special_alt->orig_sec->name); | |
525 | return -1; | |
526 | } | |
527 | ||
528 | fake_jump = malloc(sizeof(*fake_jump)); | |
529 | if (!fake_jump) { | |
530 | WARN("malloc failed"); | |
531 | return -1; | |
532 | } | |
533 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
534 | INIT_LIST_HEAD(&fake_jump->alts); | |
baa41469 JP |
535 | clear_insn_state(&fake_jump->state); |
536 | ||
dcc914f4 JP |
537 | fake_jump->sec = special_alt->new_sec; |
538 | fake_jump->offset = -1; | |
539 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; | |
540 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
baa41469 | 541 | fake_jump->ignore = true; |
dcc914f4 JP |
542 | |
543 | if (!special_alt->new_len) { | |
544 | *new_insn = fake_jump; | |
545 | return 0; | |
546 | } | |
547 | ||
548 | last_new_insn = NULL; | |
549 | insn = *new_insn; | |
550 | sec_for_each_insn_from(file, insn) { | |
551 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
552 | break; | |
553 | ||
554 | last_new_insn = insn; | |
555 | ||
556 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
557 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
558 | continue; | |
559 | ||
560 | if (!insn->immediate) | |
561 | continue; | |
562 | ||
563 | dest_off = insn->offset + insn->len + insn->immediate; | |
564 | if (dest_off == special_alt->new_off + special_alt->new_len) | |
565 | insn->jump_dest = fake_jump; | |
566 | ||
567 | if (!insn->jump_dest) { | |
568 | WARN_FUNC("can't find alternative jump destination", | |
569 | insn->sec, insn->offset); | |
570 | return -1; | |
571 | } | |
572 | } | |
573 | ||
574 | if (!last_new_insn) { | |
575 | WARN_FUNC("can't find last new alternative instruction", | |
576 | special_alt->new_sec, special_alt->new_off); | |
577 | return -1; | |
578 | } | |
579 | ||
580 | list_add(&fake_jump->list, &last_new_insn->list); | |
581 | ||
582 | return 0; | |
583 | } | |
584 | ||
585 | /* | |
586 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
587 | * If the original instruction is a jump, make the alt entry an effective nop | |
588 | * by just skipping the original instruction. | |
589 | */ | |
590 | static int handle_jump_alt(struct objtool_file *file, | |
591 | struct special_alt *special_alt, | |
592 | struct instruction *orig_insn, | |
593 | struct instruction **new_insn) | |
594 | { | |
595 | if (orig_insn->type == INSN_NOP) | |
596 | return 0; | |
597 | ||
598 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
599 | WARN_FUNC("unsupported instruction at jump label", | |
600 | orig_insn->sec, orig_insn->offset); | |
601 | return -1; | |
602 | } | |
603 | ||
604 | *new_insn = list_next_entry(orig_insn, list); | |
605 | return 0; | |
606 | } | |
607 | ||
608 | /* | |
609 | * Read all the special sections which have alternate instructions which can be | |
610 | * patched in or redirected to at runtime. Each instruction having alternate | |
611 | * instruction(s) has them added to its insn->alts list, which will be | |
612 | * traversed in validate_branch(). | |
613 | */ | |
614 | static int add_special_section_alts(struct objtool_file *file) | |
615 | { | |
616 | struct list_head special_alts; | |
617 | struct instruction *orig_insn, *new_insn; | |
618 | struct special_alt *special_alt, *tmp; | |
619 | struct alternative *alt; | |
620 | int ret; | |
621 | ||
622 | ret = special_get_alts(file->elf, &special_alts); | |
623 | if (ret) | |
624 | return ret; | |
625 | ||
626 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
627 | alt = malloc(sizeof(*alt)); | |
628 | if (!alt) { | |
629 | WARN("malloc failed"); | |
630 | ret = -1; | |
631 | goto out; | |
632 | } | |
633 | ||
634 | orig_insn = find_insn(file, special_alt->orig_sec, | |
635 | special_alt->orig_off); | |
636 | if (!orig_insn) { | |
637 | WARN_FUNC("special: can't find orig instruction", | |
638 | special_alt->orig_sec, special_alt->orig_off); | |
639 | ret = -1; | |
640 | goto out; | |
641 | } | |
642 | ||
643 | new_insn = NULL; | |
644 | if (!special_alt->group || special_alt->new_len) { | |
645 | new_insn = find_insn(file, special_alt->new_sec, | |
646 | special_alt->new_off); | |
647 | if (!new_insn) { | |
648 | WARN_FUNC("special: can't find new instruction", | |
649 | special_alt->new_sec, | |
650 | special_alt->new_off); | |
651 | ret = -1; | |
652 | goto out; | |
653 | } | |
654 | } | |
655 | ||
656 | if (special_alt->group) { | |
657 | ret = handle_group_alt(file, special_alt, orig_insn, | |
658 | &new_insn); | |
659 | if (ret) | |
660 | goto out; | |
661 | } else if (special_alt->jump_or_nop) { | |
662 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
663 | &new_insn); | |
664 | if (ret) | |
665 | goto out; | |
666 | } | |
667 | ||
668 | alt->insn = new_insn; | |
669 | list_add_tail(&alt->list, &orig_insn->alts); | |
670 | ||
671 | list_del(&special_alt->list); | |
672 | free(special_alt); | |
673 | } | |
674 | ||
675 | out: | |
676 | return ret; | |
677 | } | |
678 | ||
679 | static int add_switch_table(struct objtool_file *file, struct symbol *func, | |
680 | struct instruction *insn, struct rela *table, | |
681 | struct rela *next_table) | |
682 | { | |
683 | struct rela *rela = table; | |
684 | struct instruction *alt_insn; | |
685 | struct alternative *alt; | |
686 | ||
687 | list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { | |
688 | if (rela == next_table) | |
689 | break; | |
690 | ||
691 | if (rela->sym->sec != insn->sec || | |
692 | rela->addend <= func->offset || | |
693 | rela->addend >= func->offset + func->len) | |
694 | break; | |
695 | ||
696 | alt_insn = find_insn(file, insn->sec, rela->addend); | |
697 | if (!alt_insn) { | |
698 | WARN("%s: can't find instruction at %s+0x%x", | |
699 | file->rodata->rela->name, insn->sec->name, | |
700 | rela->addend); | |
701 | return -1; | |
702 | } | |
703 | ||
704 | alt = malloc(sizeof(*alt)); | |
705 | if (!alt) { | |
706 | WARN("malloc failed"); | |
707 | return -1; | |
708 | } | |
709 | ||
710 | alt->insn = alt_insn; | |
711 | list_add_tail(&alt->list, &insn->alts); | |
712 | } | |
713 | ||
714 | return 0; | |
715 | } | |
716 | ||
717 | /* | |
718 | * find_switch_table() - Given a dynamic jump, find the switch jump table in | |
719 | * .rodata associated with it. | |
720 | * | |
721 | * There are 3 basic patterns: | |
722 | * | |
723 | * 1. jmpq *[rodata addr](,%reg,8) | |
724 | * | |
725 | * This is the most common case by far. It jumps to an address in a simple | |
726 | * jump table which is stored in .rodata. | |
727 | * | |
728 | * 2. jmpq *[rodata addr](%rip) | |
729 | * | |
730 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
731 | * functions in the kernel, only with certain obscure non-distro configs. | |
732 | * | |
733 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
734 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
735 | * jump) to use a single entry in the table. The rest of the jump table and | |
736 | * some of its jump targets remain as dead code. | |
737 | * | |
738 | * In such a case we can just crudely ignore all unreachable instruction | |
739 | * warnings for the entire object file. Ideally we would just ignore them | |
740 | * for the function, but that would require redesigning the code quite a | |
741 | * bit. And honestly that's just not worth doing: unreachable instruction | |
742 | * warnings are of questionable value anyway, and this is such a rare issue. | |
743 | * | |
744 | * 3. mov [rodata addr],%reg1 | |
745 | * ... some instructions ... | |
746 | * jmpq *(%reg1,%reg2,8) | |
747 | * | |
748 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
749 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
750 | * | |
751 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, | |
752 | * ensure the same register is used in the mov and jump instructions. | |
753 | */ | |
754 | static struct rela *find_switch_table(struct objtool_file *file, | |
755 | struct symbol *func, | |
756 | struct instruction *insn) | |
757 | { | |
758 | struct rela *text_rela, *rodata_rela; | |
759 | struct instruction *orig_insn = insn; | |
760 | ||
761 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); | |
762 | if (text_rela && text_rela->sym == file->rodata->sym) { | |
763 | /* case 1 */ | |
764 | rodata_rela = find_rela_by_dest(file->rodata, | |
765 | text_rela->addend); | |
766 | if (rodata_rela) | |
767 | return rodata_rela; | |
768 | ||
769 | /* case 2 */ | |
770 | rodata_rela = find_rela_by_dest(file->rodata, | |
771 | text_rela->addend + 4); | |
772 | if (!rodata_rela) | |
773 | return NULL; | |
774 | file->ignore_unreachables = true; | |
775 | return rodata_rela; | |
776 | } | |
777 | ||
778 | /* case 3 */ | |
779 | func_for_each_insn_continue_reverse(file, func, insn) { | |
780 | if (insn->type == INSN_JUMP_DYNAMIC) | |
781 | break; | |
782 | ||
783 | /* allow small jumps within the range */ | |
784 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
785 | insn->jump_dest && | |
786 | (insn->jump_dest->offset <= insn->offset || | |
787 | insn->jump_dest->offset > orig_insn->offset)) | |
788 | break; | |
789 | ||
790 | /* look for a relocation which references .rodata */ | |
791 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
792 | insn->len); | |
793 | if (!text_rela || text_rela->sym != file->rodata->sym) | |
794 | continue; | |
795 | ||
796 | /* | |
797 | * Make sure the .rodata address isn't associated with a | |
798 | * symbol. gcc jump tables are anonymous data. | |
799 | */ | |
800 | if (find_symbol_containing(file->rodata, text_rela->addend)) | |
801 | continue; | |
802 | ||
803 | return find_rela_by_dest(file->rodata, text_rela->addend); | |
804 | } | |
805 | ||
806 | return NULL; | |
807 | } | |
808 | ||
809 | static int add_func_switch_tables(struct objtool_file *file, | |
810 | struct symbol *func) | |
811 | { | |
812 | struct instruction *insn, *prev_jump = NULL; | |
813 | struct rela *rela, *prev_rela = NULL; | |
814 | int ret; | |
815 | ||
816 | func_for_each_insn(file, func, insn) { | |
817 | if (insn->type != INSN_JUMP_DYNAMIC) | |
818 | continue; | |
819 | ||
820 | rela = find_switch_table(file, func, insn); | |
821 | if (!rela) | |
822 | continue; | |
823 | ||
824 | /* | |
825 | * We found a switch table, but we don't know yet how big it | |
826 | * is. Don't add it until we reach the end of the function or | |
827 | * the beginning of another switch table in the same function. | |
828 | */ | |
829 | if (prev_jump) { | |
830 | ret = add_switch_table(file, func, prev_jump, prev_rela, | |
831 | rela); | |
832 | if (ret) | |
833 | return ret; | |
834 | } | |
835 | ||
836 | prev_jump = insn; | |
837 | prev_rela = rela; | |
838 | } | |
839 | ||
840 | if (prev_jump) { | |
841 | ret = add_switch_table(file, func, prev_jump, prev_rela, NULL); | |
842 | if (ret) | |
843 | return ret; | |
844 | } | |
845 | ||
846 | return 0; | |
847 | } | |
848 | ||
849 | /* | |
850 | * For some switch statements, gcc generates a jump table in the .rodata | |
851 | * section which contains a list of addresses within the function to jump to. | |
852 | * This finds these jump tables and adds them to the insn->alts lists. | |
853 | */ | |
854 | static int add_switch_table_alts(struct objtool_file *file) | |
855 | { | |
856 | struct section *sec; | |
857 | struct symbol *func; | |
858 | int ret; | |
859 | ||
860 | if (!file->rodata || !file->rodata->rela) | |
861 | return 0; | |
862 | ||
baa41469 | 863 | for_each_sec(file, sec) { |
dcc914f4 JP |
864 | list_for_each_entry(func, &sec->symbol_list, list) { |
865 | if (func->type != STT_FUNC) | |
866 | continue; | |
867 | ||
868 | ret = add_func_switch_tables(file, func); | |
869 | if (ret) | |
870 | return ret; | |
871 | } | |
872 | } | |
873 | ||
874 | return 0; | |
875 | } | |
876 | ||
877 | static int decode_sections(struct objtool_file *file) | |
878 | { | |
879 | int ret; | |
880 | ||
881 | ret = decode_instructions(file); | |
882 | if (ret) | |
883 | return ret; | |
884 | ||
885 | ret = add_dead_ends(file); | |
886 | if (ret) | |
887 | return ret; | |
888 | ||
889 | add_ignores(file); | |
890 | ||
891 | ret = add_jump_destinations(file); | |
892 | if (ret) | |
893 | return ret; | |
894 | ||
895 | ret = add_call_destinations(file); | |
896 | if (ret) | |
897 | return ret; | |
898 | ||
899 | ret = add_special_section_alts(file); | |
900 | if (ret) | |
901 | return ret; | |
902 | ||
903 | ret = add_switch_table_alts(file); | |
904 | if (ret) | |
905 | return ret; | |
906 | ||
907 | return 0; | |
908 | } | |
909 | ||
910 | static bool is_fentry_call(struct instruction *insn) | |
911 | { | |
912 | if (insn->type == INSN_CALL && | |
913 | insn->call_dest->type == STT_NOTYPE && | |
914 | !strcmp(insn->call_dest->name, "__fentry__")) | |
915 | return true; | |
916 | ||
917 | return false; | |
918 | } | |
919 | ||
baa41469 | 920 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 921 | { |
baa41469 JP |
922 | int i; |
923 | ||
924 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
925 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
926 | state->stack_size != initial_func_cfi.cfa.offset || | |
927 | state->drap) | |
928 | return true; | |
929 | ||
930 | for (i = 0; i < CFI_NUM_REGS; i++) | |
931 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
932 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
933 | return true; | |
934 | ||
935 | return false; | |
936 | } | |
937 | ||
938 | static bool has_valid_stack_frame(struct insn_state *state) | |
939 | { | |
940 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
941 | state->regs[CFI_BP].offset == -16) | |
942 | return true; | |
943 | ||
944 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
945 | return true; | |
946 | ||
947 | return false; | |
dcc914f4 JP |
948 | } |
949 | ||
baa41469 JP |
950 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
951 | int offset) | |
dcc914f4 | 952 | { |
baa41469 JP |
953 | if ((arch_callee_saved_reg(reg) || |
954 | (state->drap && reg == state->drap_reg)) && | |
955 | state->regs[reg].base == CFI_UNDEFINED) { | |
956 | state->regs[reg].base = base; | |
957 | state->regs[reg].offset = offset; | |
958 | } | |
dcc914f4 JP |
959 | } |
960 | ||
baa41469 | 961 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 962 | { |
baa41469 JP |
963 | state->regs[reg].base = CFI_UNDEFINED; |
964 | state->regs[reg].offset = 0; | |
965 | } | |
966 | ||
967 | /* | |
968 | * A note about DRAP stack alignment: | |
969 | * | |
970 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
971 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
972 | * register. The typical DRAP pattern is: | |
973 | * | |
974 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
975 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
976 | * 41 ff 72 f8 pushq -0x8(%r10) | |
977 | * 55 push %rbp | |
978 | * 48 89 e5 mov %rsp,%rbp | |
979 | * (more pushes) | |
980 | * 41 52 push %r10 | |
981 | * ... | |
982 | * 41 5a pop %r10 | |
983 | * (more pops) | |
984 | * 5d pop %rbp | |
985 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
986 | * c3 retq | |
987 | * | |
988 | * There are some variations in the epilogues, like: | |
989 | * | |
990 | * 5b pop %rbx | |
991 | * 41 5a pop %r10 | |
992 | * 41 5c pop %r12 | |
993 | * 41 5d pop %r13 | |
994 | * 41 5e pop %r14 | |
995 | * c9 leaveq | |
996 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
997 | * c3 retq | |
998 | * | |
999 | * and: | |
1000 | * | |
1001 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1002 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1003 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1004 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1005 | * c9 leaveq | |
1006 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1007 | * c3 retq | |
1008 | * | |
1009 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1010 | * restored beforehand: | |
1011 | * | |
1012 | * 41 55 push %r13 | |
1013 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1014 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1015 | * ... | |
1016 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1017 | * 41 5d pop %r13 | |
1018 | * c3 retq | |
1019 | */ | |
1020 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1021 | { | |
1022 | struct stack_op *op = &insn->stack_op; | |
1023 | struct cfi_reg *cfa = &state->cfa; | |
1024 | struct cfi_reg *regs = state->regs; | |
1025 | ||
1026 | /* stack operations don't make sense with an undefined CFA */ | |
1027 | if (cfa->base == CFI_UNDEFINED) { | |
1028 | if (insn->func) { | |
1029 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1030 | return -1; | |
1031 | } | |
1032 | return 0; | |
1033 | } | |
1034 | ||
1035 | switch (op->dest.type) { | |
1036 | ||
1037 | case OP_DEST_REG: | |
1038 | switch (op->src.type) { | |
1039 | ||
1040 | case OP_SRC_REG: | |
1041 | if (cfa->base == op->src.reg && cfa->base == CFI_SP && | |
1042 | op->dest.reg == CFI_BP && regs[CFI_BP].base == CFI_CFA && | |
1043 | regs[CFI_BP].offset == -cfa->offset) { | |
1044 | ||
1045 | /* mov %rsp, %rbp */ | |
1046 | cfa->base = op->dest.reg; | |
1047 | state->bp_scratch = false; | |
1048 | } else if (state->drap) { | |
1049 | ||
1050 | /* drap: mov %rsp, %rbp */ | |
1051 | regs[CFI_BP].base = CFI_BP; | |
1052 | regs[CFI_BP].offset = -state->stack_size; | |
1053 | state->bp_scratch = false; | |
1054 | } else if (!nofp) { | |
1055 | ||
1056 | WARN_FUNC("unknown stack-related register move", | |
1057 | insn->sec, insn->offset); | |
1058 | return -1; | |
1059 | } | |
1060 | ||
1061 | break; | |
1062 | ||
1063 | case OP_SRC_ADD: | |
1064 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1065 | ||
1066 | /* add imm, %rsp */ | |
1067 | state->stack_size -= op->src.offset; | |
1068 | if (cfa->base == CFI_SP) | |
1069 | cfa->offset -= op->src.offset; | |
1070 | break; | |
1071 | } | |
1072 | ||
1073 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1074 | ||
1075 | /* lea disp(%rbp), %rsp */ | |
1076 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1077 | break; | |
1078 | } | |
1079 | ||
1080 | if (op->dest.reg != CFI_BP && op->src.reg == CFI_SP && | |
1081 | cfa->base == CFI_SP) { | |
1082 | ||
1083 | /* drap: lea disp(%rsp), %drap */ | |
1084 | state->drap_reg = op->dest.reg; | |
1085 | break; | |
1086 | } | |
1087 | ||
1088 | if (state->drap && op->dest.reg == CFI_SP && | |
1089 | op->src.reg == state->drap_reg) { | |
1090 | ||
1091 | /* drap: lea disp(%drap), %rsp */ | |
1092 | cfa->base = CFI_SP; | |
1093 | cfa->offset = state->stack_size = -op->src.offset; | |
1094 | state->drap_reg = CFI_UNDEFINED; | |
1095 | state->drap = false; | |
1096 | break; | |
1097 | } | |
1098 | ||
1099 | if (op->dest.reg == state->cfa.base) { | |
1100 | WARN_FUNC("unsupported stack register modification", | |
1101 | insn->sec, insn->offset); | |
1102 | return -1; | |
1103 | } | |
1104 | ||
1105 | break; | |
1106 | ||
1107 | case OP_SRC_AND: | |
1108 | if (op->dest.reg != CFI_SP || | |
1109 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1110 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1111 | WARN_FUNC("unsupported stack pointer realignment", | |
1112 | insn->sec, insn->offset); | |
1113 | return -1; | |
1114 | } | |
1115 | ||
1116 | if (state->drap_reg != CFI_UNDEFINED) { | |
1117 | /* drap: and imm, %rsp */ | |
1118 | cfa->base = state->drap_reg; | |
1119 | cfa->offset = state->stack_size = 0; | |
1120 | state->drap = true; | |
1121 | ||
1122 | } | |
1123 | ||
1124 | /* | |
1125 | * Older versions of GCC (4.8ish) realign the stack | |
1126 | * without DRAP, with a frame pointer. | |
1127 | */ | |
1128 | ||
1129 | break; | |
1130 | ||
1131 | case OP_SRC_POP: | |
1132 | if (!state->drap && op->dest.type == OP_DEST_REG && | |
1133 | op->dest.reg == cfa->base) { | |
1134 | ||
1135 | /* pop %rbp */ | |
1136 | cfa->base = CFI_SP; | |
1137 | } | |
1138 | ||
1139 | if (regs[op->dest.reg].offset == -state->stack_size) { | |
1140 | ||
1141 | if (state->drap && cfa->base == CFI_BP_INDIRECT && | |
1142 | op->dest.type == OP_DEST_REG && | |
1143 | op->dest.reg == state->drap_reg) { | |
1144 | ||
1145 | /* drap: pop %drap */ | |
1146 | cfa->base = state->drap_reg; | |
1147 | cfa->offset = 0; | |
1148 | } | |
1149 | ||
1150 | restore_reg(state, op->dest.reg); | |
1151 | } | |
1152 | ||
1153 | state->stack_size -= 8; | |
1154 | if (cfa->base == CFI_SP) | |
1155 | cfa->offset -= 8; | |
1156 | ||
1157 | break; | |
1158 | ||
1159 | case OP_SRC_REG_INDIRECT: | |
1160 | if (state->drap && op->src.reg == CFI_BP && | |
1161 | op->src.offset == regs[op->dest.reg].offset) { | |
1162 | ||
1163 | /* drap: mov disp(%rbp), %reg */ | |
1164 | if (op->dest.reg == state->drap_reg) { | |
1165 | cfa->base = state->drap_reg; | |
1166 | cfa->offset = 0; | |
1167 | } | |
1168 | ||
1169 | restore_reg(state, op->dest.reg); | |
1170 | ||
1171 | } else if (op->src.reg == cfa->base && | |
1172 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1173 | ||
1174 | /* mov disp(%rbp), %reg */ | |
1175 | /* mov disp(%rsp), %reg */ | |
1176 | restore_reg(state, op->dest.reg); | |
1177 | } | |
1178 | ||
1179 | break; | |
1180 | ||
1181 | default: | |
1182 | WARN_FUNC("unknown stack-related instruction", | |
1183 | insn->sec, insn->offset); | |
1184 | return -1; | |
1185 | } | |
1186 | ||
1187 | break; | |
1188 | ||
1189 | case OP_DEST_PUSH: | |
1190 | state->stack_size += 8; | |
1191 | if (cfa->base == CFI_SP) | |
1192 | cfa->offset += 8; | |
1193 | ||
1194 | if (op->src.type != OP_SRC_REG) | |
1195 | break; | |
1196 | ||
1197 | if (state->drap) { | |
1198 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1199 | ||
1200 | /* drap: push %drap */ | |
1201 | cfa->base = CFI_BP_INDIRECT; | |
1202 | cfa->offset = -state->stack_size; | |
1203 | ||
1204 | /* save drap so we know when to undefine it */ | |
1205 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1206 | ||
1207 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1208 | ||
1209 | /* drap: push %rbp */ | |
1210 | state->stack_size = 0; | |
1211 | ||
1212 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1213 | ||
1214 | /* drap: push %reg */ | |
1215 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1216 | } | |
1217 | ||
1218 | } else { | |
1219 | ||
1220 | /* push %reg */ | |
1221 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1222 | } | |
1223 | ||
1224 | /* detect when asm code uses rbp as a scratch register */ | |
1225 | if (!nofp && insn->func && op->src.reg == CFI_BP && | |
1226 | cfa->base != CFI_BP) | |
1227 | state->bp_scratch = true; | |
1228 | break; | |
1229 | ||
1230 | case OP_DEST_REG_INDIRECT: | |
1231 | ||
1232 | if (state->drap) { | |
1233 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1234 | ||
1235 | /* drap: mov %drap, disp(%rbp) */ | |
1236 | cfa->base = CFI_BP_INDIRECT; | |
1237 | cfa->offset = op->dest.offset; | |
1238 | ||
1239 | /* save drap so we know when to undefine it */ | |
1240 | save_reg(state, op->src.reg, CFI_CFA, op->dest.offset); | |
1241 | } | |
1242 | ||
1243 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1244 | ||
1245 | /* drap: mov reg, disp(%rbp) */ | |
1246 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1247 | } | |
1248 | ||
1249 | } else if (op->dest.reg == cfa->base) { | |
1250 | ||
1251 | /* mov reg, disp(%rbp) */ | |
1252 | /* mov reg, disp(%rsp) */ | |
1253 | save_reg(state, op->src.reg, CFI_CFA, | |
1254 | op->dest.offset - state->cfa.offset); | |
1255 | } | |
1256 | ||
1257 | break; | |
1258 | ||
1259 | case OP_DEST_LEAVE: | |
1260 | if ((!state->drap && cfa->base != CFI_BP) || | |
1261 | (state->drap && cfa->base != state->drap_reg)) { | |
1262 | WARN_FUNC("leave instruction with modified stack frame", | |
1263 | insn->sec, insn->offset); | |
1264 | return -1; | |
1265 | } | |
1266 | ||
1267 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1268 | ||
1269 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1270 | restore_reg(state, CFI_BP); | |
1271 | ||
1272 | if (!state->drap) { | |
1273 | cfa->base = CFI_SP; | |
1274 | cfa->offset -= 8; | |
1275 | } | |
1276 | ||
1277 | break; | |
1278 | ||
1279 | case OP_DEST_MEM: | |
1280 | if (op->src.type != OP_SRC_POP) { | |
1281 | WARN_FUNC("unknown stack-related memory operation", | |
1282 | insn->sec, insn->offset); | |
1283 | return -1; | |
1284 | } | |
1285 | ||
1286 | /* pop mem */ | |
1287 | state->stack_size -= 8; | |
1288 | if (cfa->base == CFI_SP) | |
1289 | cfa->offset -= 8; | |
1290 | ||
1291 | break; | |
1292 | ||
1293 | default: | |
1294 | WARN_FUNC("unknown stack-related instruction", | |
1295 | insn->sec, insn->offset); | |
1296 | return -1; | |
1297 | } | |
1298 | ||
1299 | return 0; | |
1300 | } | |
1301 | ||
1302 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1303 | { | |
1304 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1305 | int i; | |
1306 | ||
1307 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1308 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1309 | insn->sec, insn->offset, | |
1310 | state1->cfa.base, state1->cfa.offset, | |
1311 | state2->cfa.base, state2->cfa.offset); | |
1312 | ||
1313 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1314 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1315 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1316 | sizeof(struct cfi_reg))) | |
1317 | continue; | |
1318 | ||
1319 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1320 | insn->sec, insn->offset, | |
1321 | i, state1->regs[i].base, state1->regs[i].offset, | |
1322 | i, state2->regs[i].base, state2->regs[i].offset); | |
1323 | break; | |
1324 | } | |
1325 | ||
1326 | } else if (state1->drap != state2->drap || | |
1327 | (state1->drap && state1->drap_reg != state2->drap_reg)) { | |
1328 | WARN_FUNC("stack state mismatch: drap1=%d(%d) drap2=%d(%d)", | |
1329 | insn->sec, insn->offset, | |
1330 | state1->drap, state1->drap_reg, | |
1331 | state2->drap, state2->drap_reg); | |
1332 | ||
1333 | } else | |
1334 | return true; | |
1335 | ||
1336 | return false; | |
dcc914f4 JP |
1337 | } |
1338 | ||
1339 | /* | |
1340 | * Follow the branch starting at the given instruction, and recursively follow | |
1341 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
1342 | * each instruction and validate all the rules described in | |
1343 | * tools/objtool/Documentation/stack-validation.txt. | |
1344 | */ | |
baa41469 JP |
1345 | static int validate_branch(struct objtool_file *file, struct instruction *first, |
1346 | struct insn_state state) | |
dcc914f4 JP |
1347 | { |
1348 | struct alternative *alt; | |
1349 | struct instruction *insn; | |
1350 | struct section *sec; | |
1351 | struct symbol *func = NULL; | |
dcc914f4 JP |
1352 | int ret; |
1353 | ||
1354 | insn = first; | |
1355 | sec = insn->sec; | |
dcc914f4 JP |
1356 | |
1357 | if (insn->alt_group && list_empty(&insn->alts)) { | |
1358 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
1359 | sec, insn->offset); | |
baa41469 | 1360 | return -1; |
dcc914f4 JP |
1361 | } |
1362 | ||
1363 | while (1) { | |
1364 | if (file->c_file && insn->func) { | |
1365 | if (func && func != insn->func) { | |
1366 | WARN("%s() falls through to next function %s()", | |
1367 | func->name, insn->func->name); | |
1368 | return 1; | |
1369 | } | |
dcc914f4 JP |
1370 | } |
1371 | ||
baa41469 JP |
1372 | func = insn->func; |
1373 | ||
4855022a JP |
1374 | if (func && insn->ignore) { |
1375 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
1376 | sec, insn->offset); | |
1377 | return -1; | |
1378 | } | |
1379 | ||
dcc914f4 | 1380 | if (insn->visited) { |
baa41469 | 1381 | if (!!insn_state_match(insn, &state)) |
dcc914f4 | 1382 | return 1; |
dcc914f4 JP |
1383 | |
1384 | return 0; | |
1385 | } | |
1386 | ||
dcc914f4 JP |
1387 | insn->state = state; |
1388 | ||
baa41469 JP |
1389 | insn->visited = true; |
1390 | ||
dcc914f4 JP |
1391 | list_for_each_entry(alt, &insn->alts, list) { |
1392 | ret = validate_branch(file, alt->insn, state); | |
1393 | if (ret) | |
1394 | return 1; | |
1395 | } | |
1396 | ||
1397 | switch (insn->type) { | |
1398 | ||
dcc914f4 | 1399 | case INSN_RETURN: |
baa41469 JP |
1400 | if (func && has_modified_stack_frame(&state)) { |
1401 | WARN_FUNC("return with modified stack frame", | |
dcc914f4 JP |
1402 | sec, insn->offset); |
1403 | return 1; | |
1404 | } | |
baa41469 JP |
1405 | |
1406 | if (state.bp_scratch) { | |
1407 | WARN("%s uses BP as a scratch register", | |
1408 | insn->func->name); | |
1409 | return 1; | |
1410 | } | |
1411 | ||
dcc914f4 JP |
1412 | return 0; |
1413 | ||
1414 | case INSN_CALL: | |
baa41469 | 1415 | if (is_fentry_call(insn)) |
dcc914f4 | 1416 | break; |
dcc914f4 JP |
1417 | |
1418 | ret = dead_end_function(file, insn->call_dest); | |
1419 | if (ret == 1) | |
1420 | return 0; | |
1421 | if (ret == -1) | |
1422 | return 1; | |
1423 | ||
1424 | /* fallthrough */ | |
1425 | case INSN_CALL_DYNAMIC: | |
baa41469 | 1426 | if (!nofp && func && !has_valid_stack_frame(&state)) { |
dcc914f4 JP |
1427 | WARN_FUNC("call without frame pointer save/setup", |
1428 | sec, insn->offset); | |
1429 | return 1; | |
1430 | } | |
1431 | break; | |
1432 | ||
1433 | case INSN_JUMP_CONDITIONAL: | |
1434 | case INSN_JUMP_UNCONDITIONAL: | |
4855022a JP |
1435 | if (insn->jump_dest && |
1436 | (!func || !insn->jump_dest->func || | |
1437 | func == insn->jump_dest->func)) { | |
dcc914f4 JP |
1438 | ret = validate_branch(file, insn->jump_dest, |
1439 | state); | |
1440 | if (ret) | |
1441 | return 1; | |
4855022a | 1442 | |
baa41469 JP |
1443 | } else if (func && has_modified_stack_frame(&state)) { |
1444 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1445 | sec, insn->offset); |
1446 | return 1; | |
4855022a | 1447 | } |
dcc914f4 JP |
1448 | |
1449 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
1450 | return 0; | |
1451 | ||
1452 | break; | |
1453 | ||
1454 | case INSN_JUMP_DYNAMIC: | |
baa41469 JP |
1455 | if (func && list_empty(&insn->alts) && |
1456 | has_modified_stack_frame(&state)) { | |
1457 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1458 | sec, insn->offset); |
1459 | return 1; | |
1460 | } | |
1461 | ||
1462 | return 0; | |
1463 | ||
baa41469 JP |
1464 | case INSN_STACK: |
1465 | if (update_insn_state(insn, &state)) | |
1466 | return -1; | |
1467 | ||
1468 | break; | |
1469 | ||
dcc914f4 JP |
1470 | default: |
1471 | break; | |
1472 | } | |
1473 | ||
1474 | if (insn->dead_end) | |
1475 | return 0; | |
1476 | ||
1477 | insn = next_insn_same_sec(file, insn); | |
1478 | if (!insn) { | |
1479 | WARN("%s: unexpected end of section", sec->name); | |
1480 | return 1; | |
1481 | } | |
1482 | } | |
1483 | ||
1484 | return 0; | |
1485 | } | |
1486 | ||
1487 | static bool is_kasan_insn(struct instruction *insn) | |
1488 | { | |
1489 | return (insn->type == INSN_CALL && | |
1490 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
1491 | } | |
1492 | ||
1493 | static bool is_ubsan_insn(struct instruction *insn) | |
1494 | { | |
1495 | return (insn->type == INSN_CALL && | |
1496 | !strcmp(insn->call_dest->name, | |
1497 | "__ubsan_handle_builtin_unreachable")); | |
1498 | } | |
1499 | ||
baa41469 | 1500 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
1501 | { |
1502 | int i; | |
1503 | ||
baa41469 JP |
1504 | if (insn->ignore || insn->type == INSN_NOP) |
1505 | return true; | |
1506 | ||
1507 | /* | |
1508 | * Ignore any unused exceptions. This can happen when a whitelisted | |
1509 | * function has an exception table entry. | |
1510 | */ | |
1511 | if (!strcmp(insn->sec->name, ".fixup")) | |
dcc914f4 JP |
1512 | return true; |
1513 | ||
1514 | /* | |
1515 | * Check if this (or a subsequent) instruction is related to | |
1516 | * CONFIG_UBSAN or CONFIG_KASAN. | |
1517 | * | |
1518 | * End the search at 5 instructions to avoid going into the weeds. | |
1519 | */ | |
baa41469 JP |
1520 | if (!insn->func) |
1521 | return false; | |
dcc914f4 JP |
1522 | for (i = 0; i < 5; i++) { |
1523 | ||
1524 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
1525 | return true; | |
1526 | ||
1527 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) { | |
1528 | insn = insn->jump_dest; | |
1529 | continue; | |
1530 | } | |
1531 | ||
baa41469 | 1532 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 JP |
1533 | break; |
1534 | insn = list_next_entry(insn, list); | |
1535 | } | |
1536 | ||
1537 | return false; | |
1538 | } | |
1539 | ||
1540 | static int validate_functions(struct objtool_file *file) | |
1541 | { | |
1542 | struct section *sec; | |
1543 | struct symbol *func; | |
1544 | struct instruction *insn; | |
baa41469 | 1545 | struct insn_state state; |
dcc914f4 JP |
1546 | int ret, warnings = 0; |
1547 | ||
baa41469 JP |
1548 | clear_insn_state(&state); |
1549 | ||
1550 | state.cfa = initial_func_cfi.cfa; | |
1551 | memcpy(&state.regs, &initial_func_cfi.regs, | |
1552 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
1553 | state.stack_size = initial_func_cfi.cfa.offset; | |
1554 | ||
1555 | for_each_sec(file, sec) { | |
dcc914f4 JP |
1556 | list_for_each_entry(func, &sec->symbol_list, list) { |
1557 | if (func->type != STT_FUNC) | |
1558 | continue; | |
1559 | ||
1560 | insn = find_insn(file, sec, func->offset); | |
baa41469 | 1561 | if (!insn || insn->ignore) |
dcc914f4 JP |
1562 | continue; |
1563 | ||
baa41469 | 1564 | ret = validate_branch(file, insn, state); |
dcc914f4 JP |
1565 | warnings += ret; |
1566 | } | |
1567 | } | |
1568 | ||
dcc914f4 JP |
1569 | return warnings; |
1570 | } | |
1571 | ||
baa41469 | 1572 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
1573 | { |
1574 | struct instruction *insn; | |
baa41469 JP |
1575 | |
1576 | if (file->ignore_unreachables) | |
1577 | return 0; | |
dcc914f4 JP |
1578 | |
1579 | for_each_insn(file, insn) { | |
baa41469 JP |
1580 | if (insn->visited || ignore_unreachable_insn(insn)) |
1581 | continue; | |
1582 | ||
1583 | /* | |
1584 | * gcov produces a lot of unreachable instructions. If we get | |
1585 | * an unreachable warning and the file has gcov enabled, just | |
1586 | * ignore it, and all other such warnings for the file. Do | |
1587 | * this here because this is an expensive function. | |
1588 | */ | |
1589 | if (gcov_enabled(file)) | |
1590 | return 0; | |
1591 | ||
1592 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); | |
1593 | return 1; | |
dcc914f4 JP |
1594 | } |
1595 | ||
baa41469 | 1596 | return 0; |
dcc914f4 JP |
1597 | } |
1598 | ||
1599 | static void cleanup(struct objtool_file *file) | |
1600 | { | |
1601 | struct instruction *insn, *tmpinsn; | |
1602 | struct alternative *alt, *tmpalt; | |
1603 | ||
1604 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { | |
1605 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { | |
1606 | list_del(&alt->list); | |
1607 | free(alt); | |
1608 | } | |
1609 | list_del(&insn->list); | |
1610 | hash_del(&insn->hash); | |
1611 | free(insn); | |
1612 | } | |
1613 | elf_close(file->elf); | |
1614 | } | |
1615 | ||
1616 | int check(const char *_objname, bool _nofp) | |
1617 | { | |
1618 | struct objtool_file file; | |
1619 | int ret, warnings = 0; | |
1620 | ||
1621 | objname = _objname; | |
1622 | nofp = _nofp; | |
1623 | ||
1624 | file.elf = elf_open(objname); | |
baa41469 | 1625 | if (!file.elf) |
dcc914f4 | 1626 | return 1; |
dcc914f4 JP |
1627 | |
1628 | INIT_LIST_HEAD(&file.insn_list); | |
1629 | hash_init(file.insn_hash); | |
1630 | file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); | |
1631 | file.rodata = find_section_by_name(file.elf, ".rodata"); | |
1632 | file.ignore_unreachables = false; | |
1633 | file.c_file = find_section_by_name(file.elf, ".comment"); | |
1634 | ||
baa41469 JP |
1635 | arch_initial_func_cfi_state(&initial_func_cfi); |
1636 | ||
dcc914f4 JP |
1637 | ret = decode_sections(&file); |
1638 | if (ret < 0) | |
1639 | goto out; | |
1640 | warnings += ret; | |
1641 | ||
baa41469 | 1642 | if (list_empty(&file.insn_list)) |
dcc914f4 | 1643 | goto out; |
dcc914f4 | 1644 | |
baa41469 | 1645 | ret = validate_functions(&file); |
dcc914f4 JP |
1646 | if (ret < 0) |
1647 | goto out; | |
1648 | warnings += ret; | |
1649 | ||
baa41469 JP |
1650 | if (!warnings) { |
1651 | ret = validate_reachable_instructions(&file); | |
1652 | if (ret < 0) | |
1653 | goto out; | |
1654 | warnings += ret; | |
1655 | } | |
1656 | ||
dcc914f4 JP |
1657 | out: |
1658 | cleanup(&file); | |
1659 | ||
1660 | /* ignore warnings for now until we get all the code cleaned up */ | |
1661 | if (ret || warnings) | |
1662 | return 0; | |
1663 | return 0; | |
1664 | } |