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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 | ||
b4ca1a81 | 21 | #include "builtin.h" |
dcc914f4 JP |
22 | #include "check.h" |
23 | #include "elf.h" | |
24 | #include "special.h" | |
25 | #include "arch.h" | |
26 | #include "warn.h" | |
27 | ||
28 | #include <linux/hashtable.h> | |
29 | #include <linux/kernel.h> | |
30 | ||
dcc914f4 JP |
31 | struct alternative { |
32 | struct list_head list; | |
33 | struct instruction *insn; | |
34 | }; | |
35 | ||
36 | const char *objname; | |
baa41469 | 37 | struct cfi_state initial_func_cfi; |
dcc914f4 | 38 | |
627fce14 JP |
39 | struct instruction *find_insn(struct objtool_file *file, |
40 | struct section *sec, unsigned long offset) | |
dcc914f4 JP |
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 | ||
dcc914f4 JP |
62 | #define func_for_each_insn(file, func, insn) \ |
63 | for (insn = find_insn(file, func->sec, func->offset); \ | |
64 | insn && &insn->list != &file->insn_list && \ | |
65 | insn->sec == func->sec && \ | |
66 | insn->offset < func->offset + func->len; \ | |
67 | insn = list_next_entry(insn, list)) | |
68 | ||
69 | #define func_for_each_insn_continue_reverse(file, func, insn) \ | |
70 | for (insn = list_prev_entry(insn, list); \ | |
71 | &insn->list != &file->insn_list && \ | |
72 | insn->sec == func->sec && insn->offset >= func->offset; \ | |
73 | insn = list_prev_entry(insn, list)) | |
74 | ||
75 | #define sec_for_each_insn_from(file, insn) \ | |
76 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
77 | ||
baa41469 JP |
78 | #define sec_for_each_insn_continue(file, insn) \ |
79 | for (insn = next_insn_same_sec(file, insn); insn; \ | |
80 | insn = next_insn_same_sec(file, insn)) | |
dcc914f4 JP |
81 | |
82 | /* | |
83 | * Check if the function has been manually whitelisted with the | |
84 | * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted | |
85 | * due to its use of a context switching instruction. | |
86 | */ | |
87 | static bool ignore_func(struct objtool_file *file, struct symbol *func) | |
88 | { | |
89 | struct rela *rela; | |
dcc914f4 JP |
90 | |
91 | /* check for STACK_FRAME_NON_STANDARD */ | |
92 | if (file->whitelist && file->whitelist->rela) | |
93 | list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) { | |
94 | if (rela->sym->type == STT_SECTION && | |
95 | rela->sym->sec == func->sec && | |
96 | rela->addend == func->offset) | |
97 | return true; | |
98 | if (rela->sym->type == STT_FUNC && rela->sym == func) | |
99 | return true; | |
100 | } | |
101 | ||
dcc914f4 JP |
102 | return false; |
103 | } | |
104 | ||
105 | /* | |
106 | * This checks to see if the given function is a "noreturn" function. | |
107 | * | |
108 | * For global functions which are outside the scope of this object file, we | |
109 | * have to keep a manual list of them. | |
110 | * | |
111 | * For local functions, we have to detect them manually by simply looking for | |
112 | * the lack of a return instruction. | |
113 | * | |
114 | * Returns: | |
115 | * -1: error | |
116 | * 0: no dead end | |
117 | * 1: dead end | |
118 | */ | |
119 | static int __dead_end_function(struct objtool_file *file, struct symbol *func, | |
120 | int recursion) | |
121 | { | |
122 | int i; | |
123 | struct instruction *insn; | |
124 | bool empty = true; | |
125 | ||
126 | /* | |
127 | * Unfortunately these have to be hard coded because the noreturn | |
128 | * attribute isn't provided in ELF data. | |
129 | */ | |
130 | static const char * const global_noreturns[] = { | |
131 | "__stack_chk_fail", | |
132 | "panic", | |
133 | "do_exit", | |
134 | "do_task_dead", | |
135 | "__module_put_and_exit", | |
136 | "complete_and_exit", | |
137 | "kvm_spurious_fault", | |
138 | "__reiserfs_panic", | |
139 | "lbug_with_loc", | |
140 | "fortify_panic", | |
141 | }; | |
142 | ||
143 | if (func->bind == STB_WEAK) | |
144 | return 0; | |
145 | ||
146 | if (func->bind == STB_GLOBAL) | |
147 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
148 | if (!strcmp(func->name, global_noreturns[i])) | |
149 | return 1; | |
150 | ||
151 | if (!func->sec) | |
152 | return 0; | |
153 | ||
154 | func_for_each_insn(file, func, insn) { | |
155 | empty = false; | |
156 | ||
157 | if (insn->type == INSN_RETURN) | |
158 | return 0; | |
159 | } | |
160 | ||
161 | if (empty) | |
162 | return 0; | |
163 | ||
164 | /* | |
165 | * A function can have a sibling call instead of a return. In that | |
166 | * case, the function's dead-end status depends on whether the target | |
167 | * of the sibling call returns. | |
168 | */ | |
169 | func_for_each_insn(file, func, insn) { | |
170 | if (insn->sec != func->sec || | |
171 | insn->offset >= func->offset + func->len) | |
172 | break; | |
173 | ||
174 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { | |
175 | struct instruction *dest = insn->jump_dest; | |
176 | struct symbol *dest_func; | |
177 | ||
178 | if (!dest) | |
179 | /* sibling call to another file */ | |
180 | return 0; | |
181 | ||
182 | if (dest->sec != func->sec || | |
183 | dest->offset < func->offset || | |
184 | dest->offset >= func->offset + func->len) { | |
185 | /* local sibling call */ | |
186 | dest_func = find_symbol_by_offset(dest->sec, | |
187 | dest->offset); | |
188 | if (!dest_func) | |
189 | continue; | |
190 | ||
191 | if (recursion == 5) { | |
192 | WARN_FUNC("infinite recursion (objtool bug!)", | |
193 | dest->sec, dest->offset); | |
194 | return -1; | |
195 | } | |
196 | ||
197 | return __dead_end_function(file, dest_func, | |
198 | recursion + 1); | |
199 | } | |
200 | } | |
201 | ||
202 | if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts)) | |
203 | /* sibling call */ | |
204 | return 0; | |
205 | } | |
206 | ||
207 | return 1; | |
208 | } | |
209 | ||
210 | static int dead_end_function(struct objtool_file *file, struct symbol *func) | |
211 | { | |
212 | return __dead_end_function(file, func, 0); | |
213 | } | |
214 | ||
baa41469 JP |
215 | static void clear_insn_state(struct insn_state *state) |
216 | { | |
217 | int i; | |
218 | ||
219 | memset(state, 0, sizeof(*state)); | |
220 | state->cfa.base = CFI_UNDEFINED; | |
dd88a0a0 | 221 | for (i = 0; i < CFI_NUM_REGS; i++) { |
baa41469 | 222 | state->regs[i].base = CFI_UNDEFINED; |
dd88a0a0 JP |
223 | state->vals[i].base = CFI_UNDEFINED; |
224 | } | |
baa41469 | 225 | state->drap_reg = CFI_UNDEFINED; |
bf4d1a83 | 226 | state->drap_offset = -1; |
baa41469 JP |
227 | } |
228 | ||
dcc914f4 JP |
229 | /* |
230 | * Call the arch-specific instruction decoder for all the instructions and add | |
231 | * them to the global instruction list. | |
232 | */ | |
233 | static int decode_instructions(struct objtool_file *file) | |
234 | { | |
235 | struct section *sec; | |
236 | struct symbol *func; | |
237 | unsigned long offset; | |
238 | struct instruction *insn; | |
239 | int ret; | |
240 | ||
baa41469 | 241 | for_each_sec(file, sec) { |
dcc914f4 JP |
242 | |
243 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
244 | continue; | |
245 | ||
627fce14 JP |
246 | if (strcmp(sec->name, ".altinstr_replacement") && |
247 | strcmp(sec->name, ".altinstr_aux") && | |
248 | strncmp(sec->name, ".discard.", 9)) | |
249 | sec->text = true; | |
250 | ||
dcc914f4 JP |
251 | for (offset = 0; offset < sec->len; offset += insn->len) { |
252 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
253 | if (!insn) { |
254 | WARN("malloc failed"); | |
255 | return -1; | |
256 | } | |
dcc914f4 | 257 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 258 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
259 | clear_insn_state(&insn->state); |
260 | ||
dcc914f4 JP |
261 | insn->sec = sec; |
262 | insn->offset = offset; | |
263 | ||
264 | ret = arch_decode_instruction(file->elf, sec, offset, | |
265 | sec->len - offset, | |
266 | &insn->len, &insn->type, | |
baa41469 JP |
267 | &insn->immediate, |
268 | &insn->stack_op); | |
dcc914f4 | 269 | if (ret) |
b7037983 | 270 | goto err; |
dcc914f4 JP |
271 | |
272 | if (!insn->type || insn->type > INSN_LAST) { | |
273 | WARN_FUNC("invalid instruction type %d", | |
274 | insn->sec, insn->offset, insn->type); | |
b7037983 KB |
275 | ret = -1; |
276 | goto err; | |
dcc914f4 JP |
277 | } |
278 | ||
279 | hash_add(file->insn_hash, &insn->hash, insn->offset); | |
280 | list_add_tail(&insn->list, &file->insn_list); | |
281 | } | |
282 | ||
283 | list_for_each_entry(func, &sec->symbol_list, list) { | |
284 | if (func->type != STT_FUNC) | |
285 | continue; | |
286 | ||
287 | if (!find_insn(file, sec, func->offset)) { | |
288 | WARN("%s(): can't find starting instruction", | |
289 | func->name); | |
290 | return -1; | |
291 | } | |
292 | ||
293 | func_for_each_insn(file, func, insn) | |
294 | if (!insn->func) | |
295 | insn->func = func; | |
296 | } | |
297 | } | |
298 | ||
299 | return 0; | |
b7037983 KB |
300 | |
301 | err: | |
302 | free(insn); | |
303 | return ret; | |
dcc914f4 JP |
304 | } |
305 | ||
306 | /* | |
649ea4d5 | 307 | * Mark "ud2" instructions and manually annotated dead ends. |
dcc914f4 JP |
308 | */ |
309 | static int add_dead_ends(struct objtool_file *file) | |
310 | { | |
311 | struct section *sec; | |
312 | struct rela *rela; | |
313 | struct instruction *insn; | |
314 | bool found; | |
315 | ||
649ea4d5 JP |
316 | /* |
317 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
318 | * GCC 7 inserts it for certain divide-by-zero cases. | |
319 | */ | |
320 | for_each_insn(file, insn) | |
321 | if (insn->type == INSN_BUG) | |
322 | insn->dead_end = true; | |
323 | ||
324 | /* | |
325 | * Check for manually annotated dead ends. | |
326 | */ | |
dcc914f4 JP |
327 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
328 | if (!sec) | |
649ea4d5 | 329 | goto reachable; |
dcc914f4 JP |
330 | |
331 | list_for_each_entry(rela, &sec->rela_list, list) { | |
332 | if (rela->sym->type != STT_SECTION) { | |
333 | WARN("unexpected relocation symbol type in %s", sec->name); | |
334 | return -1; | |
335 | } | |
336 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
337 | if (insn) | |
338 | insn = list_prev_entry(insn, list); | |
339 | else if (rela->addend == rela->sym->sec->len) { | |
340 | found = false; | |
341 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
342 | if (insn->sec == rela->sym->sec) { | |
343 | found = true; | |
344 | break; | |
345 | } | |
346 | } | |
347 | ||
348 | if (!found) { | |
349 | WARN("can't find unreachable insn at %s+0x%x", | |
350 | rela->sym->sec->name, rela->addend); | |
351 | return -1; | |
352 | } | |
353 | } else { | |
354 | WARN("can't find unreachable insn at %s+0x%x", | |
355 | rela->sym->sec->name, rela->addend); | |
356 | return -1; | |
357 | } | |
358 | ||
359 | insn->dead_end = true; | |
360 | } | |
361 | ||
649ea4d5 JP |
362 | reachable: |
363 | /* | |
364 | * These manually annotated reachable checks are needed for GCC 4.4, | |
365 | * where the Linux unreachable() macro isn't supported. In that case | |
366 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
367 | * not a dead end. | |
368 | */ | |
369 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
370 | if (!sec) | |
371 | return 0; | |
372 | ||
373 | list_for_each_entry(rela, &sec->rela_list, list) { | |
374 | if (rela->sym->type != STT_SECTION) { | |
375 | WARN("unexpected relocation symbol type in %s", sec->name); | |
376 | return -1; | |
377 | } | |
378 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
379 | if (insn) | |
380 | insn = list_prev_entry(insn, list); | |
381 | else if (rela->addend == rela->sym->sec->len) { | |
382 | found = false; | |
383 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
384 | if (insn->sec == rela->sym->sec) { | |
385 | found = true; | |
386 | break; | |
387 | } | |
388 | } | |
389 | ||
390 | if (!found) { | |
391 | WARN("can't find reachable insn at %s+0x%x", | |
392 | rela->sym->sec->name, rela->addend); | |
393 | return -1; | |
394 | } | |
395 | } else { | |
396 | WARN("can't find reachable insn at %s+0x%x", | |
397 | rela->sym->sec->name, rela->addend); | |
398 | return -1; | |
399 | } | |
400 | ||
401 | insn->dead_end = false; | |
402 | } | |
403 | ||
dcc914f4 JP |
404 | return 0; |
405 | } | |
406 | ||
407 | /* | |
408 | * Warnings shouldn't be reported for ignored functions. | |
409 | */ | |
410 | static void add_ignores(struct objtool_file *file) | |
411 | { | |
412 | struct instruction *insn; | |
413 | struct section *sec; | |
414 | struct symbol *func; | |
415 | ||
baa41469 | 416 | for_each_sec(file, sec) { |
dcc914f4 JP |
417 | list_for_each_entry(func, &sec->symbol_list, list) { |
418 | if (func->type != STT_FUNC) | |
419 | continue; | |
420 | ||
421 | if (!ignore_func(file, func)) | |
422 | continue; | |
423 | ||
424 | func_for_each_insn(file, func, insn) | |
baa41469 | 425 | insn->ignore = true; |
dcc914f4 JP |
426 | } |
427 | } | |
428 | } | |
429 | ||
258c7605 JP |
430 | /* |
431 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
432 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
433 | * But it at least allows objtool to understand the control flow *around* the | |
434 | * retpoline. | |
435 | */ | |
436 | static int add_nospec_ignores(struct objtool_file *file) | |
437 | { | |
438 | struct section *sec; | |
439 | struct rela *rela; | |
440 | struct instruction *insn; | |
441 | ||
442 | sec = find_section_by_name(file->elf, ".rela.discard.nospec"); | |
443 | if (!sec) | |
444 | return 0; | |
445 | ||
446 | list_for_each_entry(rela, &sec->rela_list, list) { | |
447 | if (rela->sym->type != STT_SECTION) { | |
448 | WARN("unexpected relocation symbol type in %s", sec->name); | |
449 | return -1; | |
450 | } | |
451 | ||
452 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
453 | if (!insn) { | |
454 | WARN("bad .discard.nospec entry"); | |
455 | return -1; | |
456 | } | |
457 | ||
458 | insn->ignore_alts = true; | |
459 | } | |
460 | ||
461 | return 0; | |
462 | } | |
463 | ||
dcc914f4 JP |
464 | /* |
465 | * Find the destination instructions for all jumps. | |
466 | */ | |
467 | static int add_jump_destinations(struct objtool_file *file) | |
468 | { | |
469 | struct instruction *insn; | |
470 | struct rela *rela; | |
471 | struct section *dest_sec; | |
472 | unsigned long dest_off; | |
473 | ||
474 | for_each_insn(file, insn) { | |
475 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
476 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
477 | continue; | |
478 | ||
baa41469 | 479 | if (insn->ignore) |
dcc914f4 JP |
480 | continue; |
481 | ||
482 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
483 | insn->len); | |
484 | if (!rela) { | |
485 | dest_sec = insn->sec; | |
486 | dest_off = insn->offset + insn->len + insn->immediate; | |
487 | } else if (rela->sym->type == STT_SECTION) { | |
488 | dest_sec = rela->sym->sec; | |
489 | dest_off = rela->addend + 4; | |
490 | } else if (rela->sym->sec->idx) { | |
491 | dest_sec = rela->sym->sec; | |
492 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
493 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
494 | /* | |
495 | * Retpoline jumps are really dynamic jumps in | |
496 | * disguise, so convert them accordingly. | |
497 | */ | |
498 | insn->type = INSN_JUMP_DYNAMIC; | |
cb83ad28 | 499 | insn->retpoline_safe = true; |
39b73533 | 500 | continue; |
dcc914f4 JP |
501 | } else { |
502 | /* sibling call */ | |
503 | insn->jump_dest = 0; | |
504 | continue; | |
505 | } | |
506 | ||
507 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
508 | if (!insn->jump_dest) { | |
509 | ||
510 | /* | |
511 | * This is a special case where an alt instruction | |
512 | * jumps past the end of the section. These are | |
513 | * handled later in handle_group_alt(). | |
514 | */ | |
515 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
516 | continue; | |
517 | ||
518 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
519 | insn->sec, insn->offset, dest_sec->name, | |
520 | dest_off); | |
521 | return -1; | |
522 | } | |
523 | } | |
524 | ||
525 | return 0; | |
526 | } | |
527 | ||
528 | /* | |
529 | * Find the destination instructions for all calls. | |
530 | */ | |
531 | static int add_call_destinations(struct objtool_file *file) | |
532 | { | |
533 | struct instruction *insn; | |
534 | unsigned long dest_off; | |
535 | struct rela *rela; | |
536 | ||
537 | for_each_insn(file, insn) { | |
538 | if (insn->type != INSN_CALL) | |
539 | continue; | |
540 | ||
541 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
542 | insn->len); | |
543 | if (!rela) { | |
544 | dest_off = insn->offset + insn->len + insn->immediate; | |
545 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
546 | dest_off); | |
feb6e6c6 JP |
547 | |
548 | if (!insn->call_dest && !insn->ignore) { | |
549 | WARN_FUNC("unsupported intra-function call", | |
550 | insn->sec, insn->offset); | |
cb83ad28 PZ |
551 | if (retpoline) |
552 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
553 | return -1; |
554 | } | |
feb6e6c6 | 555 | |
dcc914f4 JP |
556 | } else if (rela->sym->type == STT_SECTION) { |
557 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
558 | rela->addend+4); | |
559 | if (!insn->call_dest || | |
560 | insn->call_dest->type != STT_FUNC) { | |
561 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
562 | insn->sec, insn->offset, | |
563 | rela->sym->sec->name, | |
564 | rela->addend + 4); | |
565 | return -1; | |
566 | } | |
567 | } else | |
568 | insn->call_dest = rela->sym; | |
569 | } | |
570 | ||
571 | return 0; | |
572 | } | |
573 | ||
574 | /* | |
575 | * The .alternatives section requires some extra special care, over and above | |
576 | * what other special sections require: | |
577 | * | |
578 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
579 | * instruction at the end so that validate_branch() skips all the original | |
580 | * replaced instructions when validating the new instruction path. | |
581 | * | |
582 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
583 | * that case the old instructions are replaced with noops. We simulate that | |
584 | * by creating a fake jump as the only new instruction. | |
585 | * | |
586 | * 3. In some cases, the alternative section includes an instruction which | |
587 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
588 | * jumps' destinations to point back to .text rather than the end of the | |
589 | * entry in .altinstr_replacement. | |
590 | * | |
591 | * 4. It has been requested that we don't validate the !POPCNT feature path | |
592 | * which is a "very very small percentage of machines". | |
593 | */ | |
594 | static int handle_group_alt(struct objtool_file *file, | |
595 | struct special_alt *special_alt, | |
596 | struct instruction *orig_insn, | |
597 | struct instruction **new_insn) | |
598 | { | |
f46e44d7 | 599 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
600 | unsigned long dest_off; |
601 | ||
602 | last_orig_insn = NULL; | |
603 | insn = orig_insn; | |
604 | sec_for_each_insn_from(file, insn) { | |
605 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
606 | break; | |
607 | ||
608 | if (special_alt->skip_orig) | |
609 | insn->type = INSN_NOP; | |
610 | ||
611 | insn->alt_group = true; | |
612 | last_orig_insn = insn; | |
613 | } | |
614 | ||
f46e44d7 JP |
615 | if (next_insn_same_sec(file, last_orig_insn)) { |
616 | fake_jump = malloc(sizeof(*fake_jump)); | |
617 | if (!fake_jump) { | |
618 | WARN("malloc failed"); | |
619 | return -1; | |
620 | } | |
621 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
622 | INIT_LIST_HEAD(&fake_jump->alts); | |
623 | clear_insn_state(&fake_jump->state); | |
624 | ||
625 | fake_jump->sec = special_alt->new_sec; | |
626 | fake_jump->offset = -1; | |
627 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; | |
628 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
629 | fake_jump->ignore = true; | |
dcc914f4 | 630 | } |
dcc914f4 JP |
631 | |
632 | if (!special_alt->new_len) { | |
f46e44d7 JP |
633 | if (!fake_jump) { |
634 | WARN("%s: empty alternative at end of section", | |
635 | special_alt->orig_sec->name); | |
636 | return -1; | |
637 | } | |
638 | ||
dcc914f4 JP |
639 | *new_insn = fake_jump; |
640 | return 0; | |
641 | } | |
642 | ||
643 | last_new_insn = NULL; | |
644 | insn = *new_insn; | |
645 | sec_for_each_insn_from(file, insn) { | |
646 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
647 | break; | |
648 | ||
649 | last_new_insn = insn; | |
650 | ||
feb6e6c6 JP |
651 | insn->ignore = orig_insn->ignore_alts; |
652 | ||
dcc914f4 JP |
653 | if (insn->type != INSN_JUMP_CONDITIONAL && |
654 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
655 | continue; | |
656 | ||
657 | if (!insn->immediate) | |
658 | continue; | |
659 | ||
660 | dest_off = insn->offset + insn->len + insn->immediate; | |
f46e44d7 JP |
661 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
662 | if (!fake_jump) { | |
663 | WARN("%s: alternative jump to end of section", | |
664 | special_alt->orig_sec->name); | |
665 | return -1; | |
666 | } | |
dcc914f4 | 667 | insn->jump_dest = fake_jump; |
f46e44d7 | 668 | } |
dcc914f4 JP |
669 | |
670 | if (!insn->jump_dest) { | |
671 | WARN_FUNC("can't find alternative jump destination", | |
672 | insn->sec, insn->offset); | |
673 | return -1; | |
674 | } | |
675 | } | |
676 | ||
677 | if (!last_new_insn) { | |
678 | WARN_FUNC("can't find last new alternative instruction", | |
679 | special_alt->new_sec, special_alt->new_off); | |
680 | return -1; | |
681 | } | |
682 | ||
f46e44d7 JP |
683 | if (fake_jump) |
684 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
685 | |
686 | return 0; | |
687 | } | |
688 | ||
689 | /* | |
690 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
691 | * If the original instruction is a jump, make the alt entry an effective nop | |
692 | * by just skipping the original instruction. | |
693 | */ | |
694 | static int handle_jump_alt(struct objtool_file *file, | |
695 | struct special_alt *special_alt, | |
696 | struct instruction *orig_insn, | |
697 | struct instruction **new_insn) | |
698 | { | |
699 | if (orig_insn->type == INSN_NOP) | |
700 | return 0; | |
701 | ||
702 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
703 | WARN_FUNC("unsupported instruction at jump label", | |
704 | orig_insn->sec, orig_insn->offset); | |
705 | return -1; | |
706 | } | |
707 | ||
708 | *new_insn = list_next_entry(orig_insn, list); | |
709 | return 0; | |
710 | } | |
711 | ||
712 | /* | |
713 | * Read all the special sections which have alternate instructions which can be | |
714 | * patched in or redirected to at runtime. Each instruction having alternate | |
715 | * instruction(s) has them added to its insn->alts list, which will be | |
716 | * traversed in validate_branch(). | |
717 | */ | |
718 | static int add_special_section_alts(struct objtool_file *file) | |
719 | { | |
720 | struct list_head special_alts; | |
721 | struct instruction *orig_insn, *new_insn; | |
722 | struct special_alt *special_alt, *tmp; | |
723 | struct alternative *alt; | |
724 | int ret; | |
725 | ||
726 | ret = special_get_alts(file->elf, &special_alts); | |
727 | if (ret) | |
728 | return ret; | |
729 | ||
730 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
731 | |
732 | orig_insn = find_insn(file, special_alt->orig_sec, | |
733 | special_alt->orig_off); | |
734 | if (!orig_insn) { | |
735 | WARN_FUNC("special: can't find orig instruction", | |
736 | special_alt->orig_sec, special_alt->orig_off); | |
737 | ret = -1; | |
738 | goto out; | |
739 | } | |
740 | ||
741 | new_insn = NULL; | |
742 | if (!special_alt->group || special_alt->new_len) { | |
743 | new_insn = find_insn(file, special_alt->new_sec, | |
744 | special_alt->new_off); | |
745 | if (!new_insn) { | |
746 | WARN_FUNC("special: can't find new instruction", | |
747 | special_alt->new_sec, | |
748 | special_alt->new_off); | |
749 | ret = -1; | |
750 | goto out; | |
751 | } | |
752 | } | |
753 | ||
754 | if (special_alt->group) { | |
755 | ret = handle_group_alt(file, special_alt, orig_insn, | |
756 | &new_insn); | |
757 | if (ret) | |
758 | goto out; | |
759 | } else if (special_alt->jump_or_nop) { | |
760 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
761 | &new_insn); | |
762 | if (ret) | |
763 | goto out; | |
764 | } | |
765 | ||
258c7605 JP |
766 | alt = malloc(sizeof(*alt)); |
767 | if (!alt) { | |
768 | WARN("malloc failed"); | |
769 | ret = -1; | |
770 | goto out; | |
771 | } | |
772 | ||
dcc914f4 JP |
773 | alt->insn = new_insn; |
774 | list_add_tail(&alt->list, &orig_insn->alts); | |
775 | ||
776 | list_del(&special_alt->list); | |
777 | free(special_alt); | |
778 | } | |
779 | ||
780 | out: | |
781 | return ret; | |
782 | } | |
783 | ||
784 | static int add_switch_table(struct objtool_file *file, struct symbol *func, | |
785 | struct instruction *insn, struct rela *table, | |
786 | struct rela *next_table) | |
787 | { | |
788 | struct rela *rela = table; | |
789 | struct instruction *alt_insn; | |
790 | struct alternative *alt; | |
791 | ||
792 | list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { | |
793 | if (rela == next_table) | |
794 | break; | |
795 | ||
796 | if (rela->sym->sec != insn->sec || | |
797 | rela->addend <= func->offset || | |
798 | rela->addend >= func->offset + func->len) | |
799 | break; | |
800 | ||
801 | alt_insn = find_insn(file, insn->sec, rela->addend); | |
802 | if (!alt_insn) { | |
803 | WARN("%s: can't find instruction at %s+0x%x", | |
804 | file->rodata->rela->name, insn->sec->name, | |
805 | rela->addend); | |
806 | return -1; | |
807 | } | |
808 | ||
809 | alt = malloc(sizeof(*alt)); | |
810 | if (!alt) { | |
811 | WARN("malloc failed"); | |
812 | return -1; | |
813 | } | |
814 | ||
815 | alt->insn = alt_insn; | |
816 | list_add_tail(&alt->list, &insn->alts); | |
817 | } | |
818 | ||
819 | return 0; | |
820 | } | |
821 | ||
822 | /* | |
823 | * find_switch_table() - Given a dynamic jump, find the switch jump table in | |
824 | * .rodata associated with it. | |
825 | * | |
826 | * There are 3 basic patterns: | |
827 | * | |
828 | * 1. jmpq *[rodata addr](,%reg,8) | |
829 | * | |
830 | * This is the most common case by far. It jumps to an address in a simple | |
831 | * jump table which is stored in .rodata. | |
832 | * | |
833 | * 2. jmpq *[rodata addr](%rip) | |
834 | * | |
835 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
836 | * functions in the kernel, only with certain obscure non-distro configs. | |
837 | * | |
838 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
839 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
840 | * jump) to use a single entry in the table. The rest of the jump table and | |
841 | * some of its jump targets remain as dead code. | |
842 | * | |
843 | * In such a case we can just crudely ignore all unreachable instruction | |
844 | * warnings for the entire object file. Ideally we would just ignore them | |
845 | * for the function, but that would require redesigning the code quite a | |
846 | * bit. And honestly that's just not worth doing: unreachable instruction | |
847 | * warnings are of questionable value anyway, and this is such a rare issue. | |
848 | * | |
849 | * 3. mov [rodata addr],%reg1 | |
850 | * ... some instructions ... | |
851 | * jmpq *(%reg1,%reg2,8) | |
852 | * | |
853 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
854 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
855 | * | |
a11aacd0 PZ |
856 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
857 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
858 | * and jmpq uses .rodata itself, which can confuse things. | |
859 | * | |
dcc914f4 JP |
860 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
861 | * ensure the same register is used in the mov and jump instructions. | |
a11aacd0 PZ |
862 | * |
863 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 JP |
864 | */ |
865 | static struct rela *find_switch_table(struct objtool_file *file, | |
866 | struct symbol *func, | |
867 | struct instruction *insn) | |
868 | { | |
869 | struct rela *text_rela, *rodata_rela; | |
870 | struct instruction *orig_insn = insn; | |
871 | ||
872 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); | |
873 | if (text_rela && text_rela->sym == file->rodata->sym) { | |
874 | /* case 1 */ | |
875 | rodata_rela = find_rela_by_dest(file->rodata, | |
876 | text_rela->addend); | |
877 | if (rodata_rela) | |
878 | return rodata_rela; | |
879 | ||
880 | /* case 2 */ | |
881 | rodata_rela = find_rela_by_dest(file->rodata, | |
882 | text_rela->addend + 4); | |
883 | if (!rodata_rela) | |
884 | return NULL; | |
a11aacd0 | 885 | |
dcc914f4 JP |
886 | file->ignore_unreachables = true; |
887 | return rodata_rela; | |
888 | } | |
889 | ||
890 | /* case 3 */ | |
a11aacd0 PZ |
891 | /* |
892 | * Backward search using the @first_jump_src links, these help avoid | |
893 | * much of the 'in between' code. Which avoids us getting confused by | |
894 | * it. | |
895 | */ | |
896 | for (insn = list_prev_entry(insn, list); | |
897 | ||
898 | &insn->list != &file->insn_list && | |
899 | insn->sec == func->sec && | |
900 | insn->offset >= func->offset; | |
901 | ||
902 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { | |
903 | ||
dcc914f4 JP |
904 | if (insn->type == INSN_JUMP_DYNAMIC) |
905 | break; | |
906 | ||
907 | /* allow small jumps within the range */ | |
908 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
909 | insn->jump_dest && | |
910 | (insn->jump_dest->offset <= insn->offset || | |
911 | insn->jump_dest->offset > orig_insn->offset)) | |
912 | break; | |
913 | ||
914 | /* look for a relocation which references .rodata */ | |
915 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
916 | insn->len); | |
917 | if (!text_rela || text_rela->sym != file->rodata->sym) | |
918 | continue; | |
919 | ||
920 | /* | |
921 | * Make sure the .rodata address isn't associated with a | |
922 | * symbol. gcc jump tables are anonymous data. | |
923 | */ | |
924 | if (find_symbol_containing(file->rodata, text_rela->addend)) | |
925 | continue; | |
926 | ||
927 | return find_rela_by_dest(file->rodata, text_rela->addend); | |
928 | } | |
929 | ||
930 | return NULL; | |
931 | } | |
932 | ||
a11aacd0 | 933 | |
dcc914f4 JP |
934 | static int add_func_switch_tables(struct objtool_file *file, |
935 | struct symbol *func) | |
936 | { | |
a11aacd0 | 937 | struct instruction *insn, *last = NULL, *prev_jump = NULL; |
dcc914f4 JP |
938 | struct rela *rela, *prev_rela = NULL; |
939 | int ret; | |
940 | ||
941 | func_for_each_insn(file, func, insn) { | |
a11aacd0 PZ |
942 | if (!last) |
943 | last = insn; | |
944 | ||
945 | /* | |
946 | * Store back-pointers for unconditional forward jumps such | |
947 | * that find_switch_table() can back-track using those and | |
948 | * avoid some potentially confusing code. | |
949 | */ | |
950 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
951 | insn->offset > last->offset && | |
952 | insn->jump_dest->offset > insn->offset && | |
953 | !insn->jump_dest->first_jump_src) { | |
954 | ||
955 | insn->jump_dest->first_jump_src = insn; | |
956 | last = insn->jump_dest; | |
957 | } | |
958 | ||
dcc914f4 JP |
959 | if (insn->type != INSN_JUMP_DYNAMIC) |
960 | continue; | |
961 | ||
962 | rela = find_switch_table(file, func, insn); | |
963 | if (!rela) | |
964 | continue; | |
965 | ||
966 | /* | |
967 | * We found a switch table, but we don't know yet how big it | |
968 | * is. Don't add it until we reach the end of the function or | |
969 | * the beginning of another switch table in the same function. | |
970 | */ | |
971 | if (prev_jump) { | |
972 | ret = add_switch_table(file, func, prev_jump, prev_rela, | |
973 | rela); | |
974 | if (ret) | |
975 | return ret; | |
976 | } | |
977 | ||
978 | prev_jump = insn; | |
979 | prev_rela = rela; | |
980 | } | |
981 | ||
982 | if (prev_jump) { | |
983 | ret = add_switch_table(file, func, prev_jump, prev_rela, NULL); | |
984 | if (ret) | |
985 | return ret; | |
986 | } | |
987 | ||
988 | return 0; | |
989 | } | |
990 | ||
991 | /* | |
992 | * For some switch statements, gcc generates a jump table in the .rodata | |
993 | * section which contains a list of addresses within the function to jump to. | |
994 | * This finds these jump tables and adds them to the insn->alts lists. | |
995 | */ | |
996 | static int add_switch_table_alts(struct objtool_file *file) | |
997 | { | |
998 | struct section *sec; | |
999 | struct symbol *func; | |
1000 | int ret; | |
1001 | ||
1002 | if (!file->rodata || !file->rodata->rela) | |
1003 | return 0; | |
1004 | ||
baa41469 | 1005 | for_each_sec(file, sec) { |
dcc914f4 JP |
1006 | list_for_each_entry(func, &sec->symbol_list, list) { |
1007 | if (func->type != STT_FUNC) | |
1008 | continue; | |
1009 | ||
1010 | ret = add_func_switch_tables(file, func); | |
1011 | if (ret) | |
1012 | return ret; | |
1013 | } | |
1014 | } | |
1015 | ||
1016 | return 0; | |
1017 | } | |
1018 | ||
39358a03 JP |
1019 | static int read_unwind_hints(struct objtool_file *file) |
1020 | { | |
1021 | struct section *sec, *relasec; | |
1022 | struct rela *rela; | |
1023 | struct unwind_hint *hint; | |
1024 | struct instruction *insn; | |
1025 | struct cfi_reg *cfa; | |
1026 | int i; | |
1027 | ||
1028 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1029 | if (!sec) | |
1030 | return 0; | |
1031 | ||
1032 | relasec = sec->rela; | |
1033 | if (!relasec) { | |
1034 | WARN("missing .rela.discard.unwind_hints section"); | |
1035 | return -1; | |
1036 | } | |
1037 | ||
1038 | if (sec->len % sizeof(struct unwind_hint)) { | |
1039 | WARN("struct unwind_hint size mismatch"); | |
1040 | return -1; | |
1041 | } | |
1042 | ||
1043 | file->hints = true; | |
1044 | ||
1045 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1046 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1047 | ||
1048 | rela = find_rela_by_dest(sec, i * sizeof(*hint)); | |
1049 | if (!rela) { | |
1050 | WARN("can't find rela for unwind_hints[%d]", i); | |
1051 | return -1; | |
1052 | } | |
1053 | ||
1054 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1055 | if (!insn) { | |
1056 | WARN("can't find insn for unwind_hints[%d]", i); | |
1057 | return -1; | |
1058 | } | |
1059 | ||
1060 | cfa = &insn->state.cfa; | |
1061 | ||
1062 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1063 | insn->save = true; | |
1064 | continue; | |
1065 | ||
1066 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1067 | insn->restore = true; | |
1068 | insn->hint = true; | |
1069 | continue; | |
1070 | } | |
1071 | ||
1072 | insn->hint = true; | |
1073 | ||
1074 | switch (hint->sp_reg) { | |
1075 | case ORC_REG_UNDEFINED: | |
1076 | cfa->base = CFI_UNDEFINED; | |
1077 | break; | |
1078 | case ORC_REG_SP: | |
1079 | cfa->base = CFI_SP; | |
1080 | break; | |
1081 | case ORC_REG_BP: | |
1082 | cfa->base = CFI_BP; | |
1083 | break; | |
1084 | case ORC_REG_SP_INDIRECT: | |
1085 | cfa->base = CFI_SP_INDIRECT; | |
1086 | break; | |
1087 | case ORC_REG_R10: | |
1088 | cfa->base = CFI_R10; | |
1089 | break; | |
1090 | case ORC_REG_R13: | |
1091 | cfa->base = CFI_R13; | |
1092 | break; | |
1093 | case ORC_REG_DI: | |
1094 | cfa->base = CFI_DI; | |
1095 | break; | |
1096 | case ORC_REG_DX: | |
1097 | cfa->base = CFI_DX; | |
1098 | break; | |
1099 | default: | |
1100 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1101 | insn->sec, insn->offset, hint->sp_reg); | |
1102 | return -1; | |
1103 | } | |
1104 | ||
1105 | cfa->offset = hint->sp_offset; | |
1106 | insn->state.type = hint->type; | |
1107 | } | |
1108 | ||
1109 | return 0; | |
1110 | } | |
1111 | ||
cb83ad28 PZ |
1112 | static int read_retpoline_hints(struct objtool_file *file) |
1113 | { | |
1114 | struct section *sec, *relasec; | |
1115 | struct instruction *insn; | |
1116 | struct rela *rela; | |
1117 | int i; | |
1118 | ||
1119 | sec = find_section_by_name(file->elf, ".discard.retpoline_safe"); | |
1120 | if (!sec) | |
1121 | return 0; | |
1122 | ||
1123 | relasec = sec->rela; | |
1124 | if (!relasec) { | |
1125 | WARN("missing .rela.discard.retpoline_safe section"); | |
1126 | return -1; | |
1127 | } | |
1128 | ||
1129 | if (sec->len % sizeof(unsigned long)) { | |
1130 | WARN("retpoline_safe size mismatch: %d %ld", sec->len, sizeof(unsigned long)); | |
1131 | return -1; | |
1132 | } | |
1133 | ||
1134 | for (i = 0; i < sec->len / sizeof(unsigned long); i++) { | |
1135 | rela = find_rela_by_dest(sec, i * sizeof(unsigned long)); | |
1136 | if (!rela) { | |
1137 | WARN("can't find rela for retpoline_safe[%d]", i); | |
1138 | return -1; | |
1139 | } | |
1140 | ||
1141 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1142 | if (!insn) { | |
1143 | WARN("can't find insn for retpoline_safe[%d]", i); | |
1144 | return -1; | |
1145 | } | |
1146 | ||
1147 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1148 | insn->type != INSN_CALL_DYNAMIC) { | |
1149 | WARN_FUNC("retpoline_safe hint not a indirect jump/call", | |
1150 | insn->sec, insn->offset); | |
1151 | return -1; | |
1152 | } | |
1153 | ||
1154 | insn->retpoline_safe = true; | |
1155 | } | |
1156 | ||
1157 | return 0; | |
1158 | } | |
1159 | ||
dcc914f4 JP |
1160 | static int decode_sections(struct objtool_file *file) |
1161 | { | |
1162 | int ret; | |
1163 | ||
1164 | ret = decode_instructions(file); | |
1165 | if (ret) | |
1166 | return ret; | |
1167 | ||
1168 | ret = add_dead_ends(file); | |
1169 | if (ret) | |
1170 | return ret; | |
1171 | ||
1172 | add_ignores(file); | |
1173 | ||
258c7605 JP |
1174 | ret = add_nospec_ignores(file); |
1175 | if (ret) | |
1176 | return ret; | |
1177 | ||
dcc914f4 JP |
1178 | ret = add_jump_destinations(file); |
1179 | if (ret) | |
1180 | return ret; | |
1181 | ||
feb6e6c6 | 1182 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1183 | if (ret) |
1184 | return ret; | |
1185 | ||
feb6e6c6 | 1186 | ret = add_call_destinations(file); |
dcc914f4 JP |
1187 | if (ret) |
1188 | return ret; | |
1189 | ||
1190 | ret = add_switch_table_alts(file); | |
1191 | if (ret) | |
1192 | return ret; | |
1193 | ||
39358a03 JP |
1194 | ret = read_unwind_hints(file); |
1195 | if (ret) | |
1196 | return ret; | |
1197 | ||
cb83ad28 PZ |
1198 | ret = read_retpoline_hints(file); |
1199 | if (ret) | |
1200 | return ret; | |
1201 | ||
dcc914f4 JP |
1202 | return 0; |
1203 | } | |
1204 | ||
1205 | static bool is_fentry_call(struct instruction *insn) | |
1206 | { | |
1207 | if (insn->type == INSN_CALL && | |
1208 | insn->call_dest->type == STT_NOTYPE && | |
1209 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1210 | return true; | |
1211 | ||
1212 | return false; | |
1213 | } | |
1214 | ||
baa41469 | 1215 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1216 | { |
baa41469 JP |
1217 | int i; |
1218 | ||
1219 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1220 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1221 | state->stack_size != initial_func_cfi.cfa.offset || | |
1222 | state->drap) | |
1223 | return true; | |
1224 | ||
1225 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1226 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1227 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1228 | return true; | |
1229 | ||
1230 | return false; | |
1231 | } | |
1232 | ||
1233 | static bool has_valid_stack_frame(struct insn_state *state) | |
1234 | { | |
1235 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1236 | state->regs[CFI_BP].offset == -16) | |
1237 | return true; | |
1238 | ||
1239 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1240 | return true; | |
1241 | ||
1242 | return false; | |
dcc914f4 JP |
1243 | } |
1244 | ||
627fce14 JP |
1245 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1246 | { | |
1247 | struct cfi_reg *cfa = &state->cfa; | |
1248 | struct stack_op *op = &insn->stack_op; | |
1249 | ||
1250 | if (cfa->base != CFI_SP) | |
1251 | return 0; | |
1252 | ||
1253 | /* push */ | |
1254 | if (op->dest.type == OP_DEST_PUSH) | |
1255 | cfa->offset += 8; | |
1256 | ||
1257 | /* pop */ | |
1258 | if (op->src.type == OP_SRC_POP) | |
1259 | cfa->offset -= 8; | |
1260 | ||
1261 | /* add immediate to sp */ | |
1262 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1263 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1264 | cfa->offset -= op->src.offset; | |
1265 | ||
1266 | return 0; | |
1267 | } | |
1268 | ||
baa41469 JP |
1269 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1270 | int offset) | |
dcc914f4 | 1271 | { |
bf4d1a83 | 1272 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1273 | state->regs[reg].base == CFI_UNDEFINED) { |
1274 | state->regs[reg].base = base; | |
1275 | state->regs[reg].offset = offset; | |
1276 | } | |
dcc914f4 JP |
1277 | } |
1278 | ||
baa41469 | 1279 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1280 | { |
baa41469 JP |
1281 | state->regs[reg].base = CFI_UNDEFINED; |
1282 | state->regs[reg].offset = 0; | |
1283 | } | |
1284 | ||
1285 | /* | |
1286 | * A note about DRAP stack alignment: | |
1287 | * | |
1288 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1289 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1290 | * register. The typical DRAP pattern is: | |
1291 | * | |
1292 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1293 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1294 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1295 | * 55 push %rbp | |
1296 | * 48 89 e5 mov %rsp,%rbp | |
1297 | * (more pushes) | |
1298 | * 41 52 push %r10 | |
1299 | * ... | |
1300 | * 41 5a pop %r10 | |
1301 | * (more pops) | |
1302 | * 5d pop %rbp | |
1303 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1304 | * c3 retq | |
1305 | * | |
1306 | * There are some variations in the epilogues, like: | |
1307 | * | |
1308 | * 5b pop %rbx | |
1309 | * 41 5a pop %r10 | |
1310 | * 41 5c pop %r12 | |
1311 | * 41 5d pop %r13 | |
1312 | * 41 5e pop %r14 | |
1313 | * c9 leaveq | |
1314 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1315 | * c3 retq | |
1316 | * | |
1317 | * and: | |
1318 | * | |
1319 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1320 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1321 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1322 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1323 | * c9 leaveq | |
1324 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1325 | * c3 retq | |
1326 | * | |
1327 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1328 | * restored beforehand: | |
1329 | * | |
1330 | * 41 55 push %r13 | |
1331 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1332 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1333 | * ... | |
1334 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1335 | * 41 5d pop %r13 | |
1336 | * c3 retq | |
1337 | */ | |
1338 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1339 | { | |
1340 | struct stack_op *op = &insn->stack_op; | |
1341 | struct cfi_reg *cfa = &state->cfa; | |
1342 | struct cfi_reg *regs = state->regs; | |
1343 | ||
1344 | /* stack operations don't make sense with an undefined CFA */ | |
1345 | if (cfa->base == CFI_UNDEFINED) { | |
1346 | if (insn->func) { | |
1347 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1348 | return -1; | |
1349 | } | |
1350 | return 0; | |
1351 | } | |
1352 | ||
627fce14 JP |
1353 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1354 | return update_insn_state_regs(insn, state); | |
1355 | ||
baa41469 JP |
1356 | switch (op->dest.type) { |
1357 | ||
1358 | case OP_DEST_REG: | |
1359 | switch (op->src.type) { | |
1360 | ||
1361 | case OP_SRC_REG: | |
0d0970ee JP |
1362 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1363 | cfa->base == CFI_SP && | |
1364 | regs[CFI_BP].base == CFI_CFA && | |
1365 | regs[CFI_BP].offset == -cfa->offset) { | |
1366 | ||
1367 | /* mov %rsp, %rbp */ | |
1368 | cfa->base = op->dest.reg; | |
1369 | state->bp_scratch = false; | |
1370 | } | |
dd88a0a0 | 1371 | |
0d0970ee JP |
1372 | else if (op->src.reg == CFI_SP && |
1373 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1374 | |
0d0970ee JP |
1375 | /* drap: mov %rsp, %rbp */ |
1376 | regs[CFI_BP].base = CFI_BP; | |
1377 | regs[CFI_BP].offset = -state->stack_size; | |
1378 | state->bp_scratch = false; | |
1379 | } | |
dd88a0a0 | 1380 | |
0d0970ee JP |
1381 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1382 | ||
1383 | /* | |
1384 | * mov %rsp, %reg | |
1385 | * | |
1386 | * This is needed for the rare case where GCC | |
1387 | * does: | |
1388 | * | |
1389 | * mov %rsp, %rax | |
1390 | * ... | |
1391 | * mov %rax, %rsp | |
1392 | */ | |
1393 | state->vals[op->dest.reg].base = CFI_CFA; | |
1394 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1395 | } |
1396 | ||
1397 | else if (op->dest.reg == cfa->base) { | |
1398 | ||
1399 | /* mov %reg, %rsp */ | |
1400 | if (cfa->base == CFI_SP && | |
1401 | state->vals[op->src.reg].base == CFI_CFA) { | |
1402 | ||
1403 | /* | |
1404 | * This is needed for the rare case | |
1405 | * where GCC does something dumb like: | |
1406 | * | |
1407 | * lea 0x8(%rsp), %rcx | |
1408 | * ... | |
1409 | * mov %rcx, %rsp | |
1410 | */ | |
1411 | cfa->offset = -state->vals[op->src.reg].offset; | |
1412 | state->stack_size = cfa->offset; | |
1413 | ||
1414 | } else { | |
1415 | cfa->base = CFI_UNDEFINED; | |
1416 | cfa->offset = 0; | |
1417 | } | |
baa41469 JP |
1418 | } |
1419 | ||
1420 | break; | |
1421 | ||
1422 | case OP_SRC_ADD: | |
1423 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1424 | ||
1425 | /* add imm, %rsp */ | |
1426 | state->stack_size -= op->src.offset; | |
1427 | if (cfa->base == CFI_SP) | |
1428 | cfa->offset -= op->src.offset; | |
1429 | break; | |
1430 | } | |
1431 | ||
1432 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1433 | ||
1434 | /* lea disp(%rbp), %rsp */ | |
1435 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1436 | break; | |
1437 | } | |
1438 | ||
dd88a0a0 | 1439 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1440 | |
1441 | /* drap: lea disp(%rsp), %drap */ | |
1442 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1443 | |
1444 | /* | |
1445 | * lea disp(%rsp), %reg | |
1446 | * | |
1447 | * This is needed for the rare case where GCC | |
1448 | * does something dumb like: | |
1449 | * | |
1450 | * lea 0x8(%rsp), %rcx | |
1451 | * ... | |
1452 | * mov %rcx, %rsp | |
1453 | */ | |
1454 | state->vals[op->dest.reg].base = CFI_CFA; | |
1455 | state->vals[op->dest.reg].offset = \ | |
1456 | -state->stack_size + op->src.offset; | |
1457 | ||
baa41469 JP |
1458 | break; |
1459 | } | |
1460 | ||
1461 | if (state->drap && op->dest.reg == CFI_SP && | |
1462 | op->src.reg == state->drap_reg) { | |
1463 | ||
1464 | /* drap: lea disp(%drap), %rsp */ | |
1465 | cfa->base = CFI_SP; | |
1466 | cfa->offset = state->stack_size = -op->src.offset; | |
1467 | state->drap_reg = CFI_UNDEFINED; | |
1468 | state->drap = false; | |
1469 | break; | |
1470 | } | |
1471 | ||
1472 | if (op->dest.reg == state->cfa.base) { | |
1473 | WARN_FUNC("unsupported stack register modification", | |
1474 | insn->sec, insn->offset); | |
1475 | return -1; | |
1476 | } | |
1477 | ||
1478 | break; | |
1479 | ||
1480 | case OP_SRC_AND: | |
1481 | if (op->dest.reg != CFI_SP || | |
1482 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1483 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1484 | WARN_FUNC("unsupported stack pointer realignment", | |
1485 | insn->sec, insn->offset); | |
1486 | return -1; | |
1487 | } | |
1488 | ||
1489 | if (state->drap_reg != CFI_UNDEFINED) { | |
1490 | /* drap: and imm, %rsp */ | |
1491 | cfa->base = state->drap_reg; | |
1492 | cfa->offset = state->stack_size = 0; | |
1493 | state->drap = true; | |
baa41469 JP |
1494 | } |
1495 | ||
1496 | /* | |
1497 | * Older versions of GCC (4.8ish) realign the stack | |
1498 | * without DRAP, with a frame pointer. | |
1499 | */ | |
1500 | ||
1501 | break; | |
1502 | ||
1503 | case OP_SRC_POP: | |
1504 | if (!state->drap && op->dest.type == OP_DEST_REG && | |
1505 | op->dest.reg == cfa->base) { | |
1506 | ||
1507 | /* pop %rbp */ | |
1508 | cfa->base = CFI_SP; | |
1509 | } | |
1510 | ||
bf4d1a83 JP |
1511 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1512 | op->dest.type == OP_DEST_REG && | |
1513 | op->dest.reg == state->drap_reg && | |
1514 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1515 | |
bf4d1a83 JP |
1516 | /* drap: pop %drap */ |
1517 | cfa->base = state->drap_reg; | |
1518 | cfa->offset = 0; | |
1519 | state->drap_offset = -1; | |
baa41469 | 1520 | |
bf4d1a83 | 1521 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1522 | |
bf4d1a83 | 1523 | /* pop %reg */ |
baa41469 JP |
1524 | restore_reg(state, op->dest.reg); |
1525 | } | |
1526 | ||
1527 | state->stack_size -= 8; | |
1528 | if (cfa->base == CFI_SP) | |
1529 | cfa->offset -= 8; | |
1530 | ||
1531 | break; | |
1532 | ||
1533 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1534 | if (state->drap && op->src.reg == CFI_BP && |
1535 | op->src.offset == state->drap_offset) { | |
1536 | ||
1537 | /* drap: mov disp(%rbp), %drap */ | |
1538 | cfa->base = state->drap_reg; | |
1539 | cfa->offset = 0; | |
1540 | state->drap_offset = -1; | |
1541 | } | |
1542 | ||
baa41469 JP |
1543 | if (state->drap && op->src.reg == CFI_BP && |
1544 | op->src.offset == regs[op->dest.reg].offset) { | |
1545 | ||
1546 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1547 | restore_reg(state, op->dest.reg); |
1548 | ||
1549 | } else if (op->src.reg == cfa->base && | |
1550 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1551 | ||
1552 | /* mov disp(%rbp), %reg */ | |
1553 | /* mov disp(%rsp), %reg */ | |
1554 | restore_reg(state, op->dest.reg); | |
1555 | } | |
1556 | ||
1557 | break; | |
1558 | ||
1559 | default: | |
1560 | WARN_FUNC("unknown stack-related instruction", | |
1561 | insn->sec, insn->offset); | |
1562 | return -1; | |
1563 | } | |
1564 | ||
1565 | break; | |
1566 | ||
1567 | case OP_DEST_PUSH: | |
1568 | state->stack_size += 8; | |
1569 | if (cfa->base == CFI_SP) | |
1570 | cfa->offset += 8; | |
1571 | ||
1572 | if (op->src.type != OP_SRC_REG) | |
1573 | break; | |
1574 | ||
1575 | if (state->drap) { | |
1576 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1577 | ||
1578 | /* drap: push %drap */ | |
1579 | cfa->base = CFI_BP_INDIRECT; | |
1580 | cfa->offset = -state->stack_size; | |
1581 | ||
bf4d1a83 JP |
1582 | /* save drap so we know when to restore it */ |
1583 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1584 | |
1585 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1586 | ||
1587 | /* drap: push %rbp */ | |
1588 | state->stack_size = 0; | |
1589 | ||
1590 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1591 | ||
1592 | /* drap: push %reg */ | |
1593 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1594 | } | |
1595 | ||
1596 | } else { | |
1597 | ||
1598 | /* push %reg */ | |
1599 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1600 | } | |
1601 | ||
1602 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1603 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1604 | cfa->base != CFI_BP) |
1605 | state->bp_scratch = true; | |
1606 | break; | |
1607 | ||
1608 | case OP_DEST_REG_INDIRECT: | |
1609 | ||
1610 | if (state->drap) { | |
1611 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1612 | ||
1613 | /* drap: mov %drap, disp(%rbp) */ | |
1614 | cfa->base = CFI_BP_INDIRECT; | |
1615 | cfa->offset = op->dest.offset; | |
1616 | ||
bf4d1a83 JP |
1617 | /* save drap offset so we know when to restore it */ |
1618 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1619 | } |
1620 | ||
1621 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1622 | ||
1623 | /* drap: mov reg, disp(%rbp) */ | |
1624 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1625 | } | |
1626 | ||
1627 | } else if (op->dest.reg == cfa->base) { | |
1628 | ||
1629 | /* mov reg, disp(%rbp) */ | |
1630 | /* mov reg, disp(%rsp) */ | |
1631 | save_reg(state, op->src.reg, CFI_CFA, | |
1632 | op->dest.offset - state->cfa.offset); | |
1633 | } | |
1634 | ||
1635 | break; | |
1636 | ||
1637 | case OP_DEST_LEAVE: | |
1638 | if ((!state->drap && cfa->base != CFI_BP) || | |
1639 | (state->drap && cfa->base != state->drap_reg)) { | |
1640 | WARN_FUNC("leave instruction with modified stack frame", | |
1641 | insn->sec, insn->offset); | |
1642 | return -1; | |
1643 | } | |
1644 | ||
1645 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1646 | ||
1647 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1648 | restore_reg(state, CFI_BP); | |
1649 | ||
1650 | if (!state->drap) { | |
1651 | cfa->base = CFI_SP; | |
1652 | cfa->offset -= 8; | |
1653 | } | |
1654 | ||
1655 | break; | |
1656 | ||
1657 | case OP_DEST_MEM: | |
1658 | if (op->src.type != OP_SRC_POP) { | |
1659 | WARN_FUNC("unknown stack-related memory operation", | |
1660 | insn->sec, insn->offset); | |
1661 | return -1; | |
1662 | } | |
1663 | ||
1664 | /* pop mem */ | |
1665 | state->stack_size -= 8; | |
1666 | if (cfa->base == CFI_SP) | |
1667 | cfa->offset -= 8; | |
1668 | ||
1669 | break; | |
1670 | ||
1671 | default: | |
1672 | WARN_FUNC("unknown stack-related instruction", | |
1673 | insn->sec, insn->offset); | |
1674 | return -1; | |
1675 | } | |
1676 | ||
1677 | return 0; | |
1678 | } | |
1679 | ||
1680 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1681 | { | |
1682 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1683 | int i; | |
1684 | ||
1685 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1686 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1687 | insn->sec, insn->offset, | |
1688 | state1->cfa.base, state1->cfa.offset, | |
1689 | state2->cfa.base, state2->cfa.offset); | |
1690 | ||
1691 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1692 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1693 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1694 | sizeof(struct cfi_reg))) | |
1695 | continue; | |
1696 | ||
1697 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1698 | insn->sec, insn->offset, | |
1699 | i, state1->regs[i].base, state1->regs[i].offset, | |
1700 | i, state2->regs[i].base, state2->regs[i].offset); | |
1701 | break; | |
1702 | } | |
1703 | ||
627fce14 JP |
1704 | } else if (state1->type != state2->type) { |
1705 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1706 | insn->sec, insn->offset, state1->type, state2->type); | |
1707 | ||
baa41469 | 1708 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1709 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1710 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1711 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1712 | insn->sec, insn->offset, |
bf4d1a83 JP |
1713 | state1->drap, state1->drap_reg, state1->drap_offset, |
1714 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1715 | |
1716 | } else | |
1717 | return true; | |
1718 | ||
1719 | return false; | |
dcc914f4 JP |
1720 | } |
1721 | ||
1722 | /* | |
1723 | * Follow the branch starting at the given instruction, and recursively follow | |
1724 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
1725 | * each instruction and validate all the rules described in | |
1726 | * tools/objtool/Documentation/stack-validation.txt. | |
1727 | */ | |
baa41469 JP |
1728 | static int validate_branch(struct objtool_file *file, struct instruction *first, |
1729 | struct insn_state state) | |
dcc914f4 JP |
1730 | { |
1731 | struct alternative *alt; | |
39358a03 | 1732 | struct instruction *insn, *next_insn; |
dcc914f4 JP |
1733 | struct section *sec; |
1734 | struct symbol *func = NULL; | |
dcc914f4 JP |
1735 | int ret; |
1736 | ||
1737 | insn = first; | |
1738 | sec = insn->sec; | |
dcc914f4 JP |
1739 | |
1740 | if (insn->alt_group && list_empty(&insn->alts)) { | |
1741 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
1742 | sec, insn->offset); | |
12b25729 | 1743 | return 1; |
dcc914f4 JP |
1744 | } |
1745 | ||
1746 | while (1) { | |
39358a03 JP |
1747 | next_insn = next_insn_same_sec(file, insn); |
1748 | ||
ee97638b JP |
1749 | |
1750 | if (file->c_file && func && insn->func && func != insn->func) { | |
1751 | WARN("%s() falls through to next function %s()", | |
1752 | func->name, insn->func->name); | |
1753 | return 1; | |
dcc914f4 JP |
1754 | } |
1755 | ||
ee97638b JP |
1756 | if (insn->func) |
1757 | func = insn->func; | |
baa41469 | 1758 | |
4855022a JP |
1759 | if (func && insn->ignore) { |
1760 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
1761 | sec, insn->offset); | |
12b25729 | 1762 | return 1; |
4855022a JP |
1763 | } |
1764 | ||
dcc914f4 | 1765 | if (insn->visited) { |
39358a03 | 1766 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 1767 | return 1; |
dcc914f4 JP |
1768 | |
1769 | return 0; | |
1770 | } | |
1771 | ||
39358a03 JP |
1772 | if (insn->hint) { |
1773 | if (insn->restore) { | |
1774 | struct instruction *save_insn, *i; | |
1775 | ||
1776 | i = insn; | |
1777 | save_insn = NULL; | |
1778 | func_for_each_insn_continue_reverse(file, func, i) { | |
1779 | if (i->save) { | |
1780 | save_insn = i; | |
1781 | break; | |
1782 | } | |
1783 | } | |
1784 | ||
1785 | if (!save_insn) { | |
1786 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
1787 | sec, insn->offset); | |
1788 | return 1; | |
1789 | } | |
1790 | ||
1791 | if (!save_insn->visited) { | |
1792 | /* | |
1793 | * Oops, no state to copy yet. | |
1794 | * Hopefully we can reach this | |
1795 | * instruction from another branch | |
1796 | * after the save insn has been | |
1797 | * visited. | |
1798 | */ | |
1799 | if (insn == first) | |
1800 | return 0; | |
1801 | ||
1802 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
1803 | sec, insn->offset); | |
1804 | return 1; | |
1805 | } | |
1806 | ||
1807 | insn->state = save_insn->state; | |
1808 | } | |
1809 | ||
1810 | state = insn->state; | |
1811 | ||
1812 | } else | |
1813 | insn->state = state; | |
dcc914f4 | 1814 | |
baa41469 JP |
1815 | insn->visited = true; |
1816 | ||
feb6e6c6 JP |
1817 | if (!insn->ignore_alts) { |
1818 | list_for_each_entry(alt, &insn->alts, list) { | |
1819 | ret = validate_branch(file, alt->insn, state); | |
1820 | if (ret) | |
1821 | return 1; | |
1822 | } | |
dcc914f4 JP |
1823 | } |
1824 | ||
1825 | switch (insn->type) { | |
1826 | ||
dcc914f4 | 1827 | case INSN_RETURN: |
baa41469 JP |
1828 | if (func && has_modified_stack_frame(&state)) { |
1829 | WARN_FUNC("return with modified stack frame", | |
dcc914f4 JP |
1830 | sec, insn->offset); |
1831 | return 1; | |
1832 | } | |
baa41469 JP |
1833 | |
1834 | if (state.bp_scratch) { | |
1835 | WARN("%s uses BP as a scratch register", | |
1836 | insn->func->name); | |
1837 | return 1; | |
1838 | } | |
1839 | ||
dcc914f4 JP |
1840 | return 0; |
1841 | ||
1842 | case INSN_CALL: | |
baa41469 | 1843 | if (is_fentry_call(insn)) |
dcc914f4 | 1844 | break; |
dcc914f4 JP |
1845 | |
1846 | ret = dead_end_function(file, insn->call_dest); | |
1847 | if (ret == 1) | |
1848 | return 0; | |
1849 | if (ret == -1) | |
1850 | return 1; | |
1851 | ||
1852 | /* fallthrough */ | |
1853 | case INSN_CALL_DYNAMIC: | |
867ac9d7 | 1854 | if (!no_fp && func && !has_valid_stack_frame(&state)) { |
dcc914f4 JP |
1855 | WARN_FUNC("call without frame pointer save/setup", |
1856 | sec, insn->offset); | |
1857 | return 1; | |
1858 | } | |
1859 | break; | |
1860 | ||
1861 | case INSN_JUMP_CONDITIONAL: | |
1862 | case INSN_JUMP_UNCONDITIONAL: | |
4855022a JP |
1863 | if (insn->jump_dest && |
1864 | (!func || !insn->jump_dest->func || | |
1865 | func == insn->jump_dest->func)) { | |
dcc914f4 JP |
1866 | ret = validate_branch(file, insn->jump_dest, |
1867 | state); | |
1868 | if (ret) | |
1869 | return 1; | |
4855022a | 1870 | |
baa41469 JP |
1871 | } else if (func && has_modified_stack_frame(&state)) { |
1872 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1873 | sec, insn->offset); |
1874 | return 1; | |
4855022a | 1875 | } |
dcc914f4 JP |
1876 | |
1877 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
1878 | return 0; | |
1879 | ||
1880 | break; | |
1881 | ||
1882 | case INSN_JUMP_DYNAMIC: | |
baa41469 JP |
1883 | if (func && list_empty(&insn->alts) && |
1884 | has_modified_stack_frame(&state)) { | |
1885 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1886 | sec, insn->offset); |
1887 | return 1; | |
1888 | } | |
1889 | ||
1890 | return 0; | |
1891 | ||
39358a03 JP |
1892 | case INSN_CONTEXT_SWITCH: |
1893 | if (func && (!next_insn || !next_insn->hint)) { | |
1894 | WARN_FUNC("unsupported instruction in callable function", | |
1895 | sec, insn->offset); | |
1896 | return 1; | |
1897 | } | |
1898 | return 0; | |
1899 | ||
baa41469 JP |
1900 | case INSN_STACK: |
1901 | if (update_insn_state(insn, &state)) | |
12b25729 | 1902 | return 1; |
baa41469 JP |
1903 | |
1904 | break; | |
1905 | ||
dcc914f4 JP |
1906 | default: |
1907 | break; | |
1908 | } | |
1909 | ||
1910 | if (insn->dead_end) | |
1911 | return 0; | |
1912 | ||
00d96180 JP |
1913 | if (!next_insn) { |
1914 | if (state.cfa.base == CFI_UNDEFINED) | |
1915 | return 0; | |
dcc914f4 JP |
1916 | WARN("%s: unexpected end of section", sec->name); |
1917 | return 1; | |
1918 | } | |
00d96180 JP |
1919 | |
1920 | insn = next_insn; | |
dcc914f4 JP |
1921 | } |
1922 | ||
1923 | return 0; | |
1924 | } | |
1925 | ||
39358a03 JP |
1926 | static int validate_unwind_hints(struct objtool_file *file) |
1927 | { | |
1928 | struct instruction *insn; | |
1929 | int ret, warnings = 0; | |
1930 | struct insn_state state; | |
1931 | ||
1932 | if (!file->hints) | |
1933 | return 0; | |
1934 | ||
1935 | clear_insn_state(&state); | |
1936 | ||
1937 | for_each_insn(file, insn) { | |
1938 | if (insn->hint && !insn->visited) { | |
1939 | ret = validate_branch(file, insn, state); | |
1940 | warnings += ret; | |
1941 | } | |
1942 | } | |
1943 | ||
1944 | return warnings; | |
1945 | } | |
1946 | ||
cb83ad28 PZ |
1947 | static int validate_retpoline(struct objtool_file *file) |
1948 | { | |
1949 | struct instruction *insn; | |
1950 | int warnings = 0; | |
1951 | ||
1952 | for_each_insn(file, insn) { | |
1953 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1954 | insn->type != INSN_CALL_DYNAMIC) | |
1955 | continue; | |
1956 | ||
1957 | if (insn->retpoline_safe) | |
1958 | continue; | |
1959 | ||
1960 | WARN_FUNC("indirect %s found in RETPOLINE build", | |
1961 | insn->sec, insn->offset, | |
1962 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
1963 | ||
1964 | warnings++; | |
1965 | } | |
1966 | ||
1967 | return warnings; | |
1968 | } | |
1969 | ||
dcc914f4 JP |
1970 | static bool is_kasan_insn(struct instruction *insn) |
1971 | { | |
1972 | return (insn->type == INSN_CALL && | |
1973 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
1974 | } | |
1975 | ||
1976 | static bool is_ubsan_insn(struct instruction *insn) | |
1977 | { | |
1978 | return (insn->type == INSN_CALL && | |
1979 | !strcmp(insn->call_dest->name, | |
1980 | "__ubsan_handle_builtin_unreachable")); | |
1981 | } | |
1982 | ||
baa41469 | 1983 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
1984 | { |
1985 | int i; | |
1986 | ||
baa41469 JP |
1987 | if (insn->ignore || insn->type == INSN_NOP) |
1988 | return true; | |
1989 | ||
1990 | /* | |
1991 | * Ignore any unused exceptions. This can happen when a whitelisted | |
1992 | * function has an exception table entry. | |
0e2bb2bc JP |
1993 | * |
1994 | * Also ignore alternative replacement instructions. This can happen | |
1995 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 1996 | */ |
0e2bb2bc JP |
1997 | if (!strcmp(insn->sec->name, ".fixup") || |
1998 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
1999 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2000 | return true; |
2001 | ||
2002 | /* | |
2003 | * Check if this (or a subsequent) instruction is related to | |
2004 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2005 | * | |
2006 | * End the search at 5 instructions to avoid going into the weeds. | |
2007 | */ | |
baa41469 JP |
2008 | if (!insn->func) |
2009 | return false; | |
dcc914f4 JP |
2010 | for (i = 0; i < 5; i++) { |
2011 | ||
2012 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2013 | return true; | |
2014 | ||
7c64b1f9 JP |
2015 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2016 | if (insn->jump_dest && | |
2017 | insn->jump_dest->func == insn->func) { | |
2018 | insn = insn->jump_dest; | |
2019 | continue; | |
2020 | } | |
2021 | ||
2022 | break; | |
dcc914f4 JP |
2023 | } |
2024 | ||
baa41469 | 2025 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2026 | break; |
7c64b1f9 | 2027 | |
dcc914f4 JP |
2028 | insn = list_next_entry(insn, list); |
2029 | } | |
2030 | ||
2031 | return false; | |
2032 | } | |
2033 | ||
2034 | static int validate_functions(struct objtool_file *file) | |
2035 | { | |
2036 | struct section *sec; | |
2037 | struct symbol *func; | |
2038 | struct instruction *insn; | |
baa41469 | 2039 | struct insn_state state; |
dcc914f4 JP |
2040 | int ret, warnings = 0; |
2041 | ||
baa41469 JP |
2042 | clear_insn_state(&state); |
2043 | ||
2044 | state.cfa = initial_func_cfi.cfa; | |
2045 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2046 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2047 | state.stack_size = initial_func_cfi.cfa.offset; | |
2048 | ||
2049 | for_each_sec(file, sec) { | |
dcc914f4 JP |
2050 | list_for_each_entry(func, &sec->symbol_list, list) { |
2051 | if (func->type != STT_FUNC) | |
2052 | continue; | |
2053 | ||
2054 | insn = find_insn(file, sec, func->offset); | |
baa41469 | 2055 | if (!insn || insn->ignore) |
dcc914f4 JP |
2056 | continue; |
2057 | ||
baa41469 | 2058 | ret = validate_branch(file, insn, state); |
dcc914f4 JP |
2059 | warnings += ret; |
2060 | } | |
2061 | } | |
2062 | ||
dcc914f4 JP |
2063 | return warnings; |
2064 | } | |
2065 | ||
baa41469 | 2066 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2067 | { |
2068 | struct instruction *insn; | |
baa41469 JP |
2069 | |
2070 | if (file->ignore_unreachables) | |
2071 | return 0; | |
dcc914f4 JP |
2072 | |
2073 | for_each_insn(file, insn) { | |
baa41469 JP |
2074 | if (insn->visited || ignore_unreachable_insn(insn)) |
2075 | continue; | |
2076 | ||
baa41469 JP |
2077 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2078 | return 1; | |
dcc914f4 JP |
2079 | } |
2080 | ||
baa41469 | 2081 | return 0; |
dcc914f4 JP |
2082 | } |
2083 | ||
2084 | static void cleanup(struct objtool_file *file) | |
2085 | { | |
2086 | struct instruction *insn, *tmpinsn; | |
2087 | struct alternative *alt, *tmpalt; | |
2088 | ||
2089 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { | |
2090 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { | |
2091 | list_del(&alt->list); | |
2092 | free(alt); | |
2093 | } | |
2094 | list_del(&insn->list); | |
2095 | hash_del(&insn->hash); | |
2096 | free(insn); | |
2097 | } | |
2098 | elf_close(file->elf); | |
2099 | } | |
2100 | ||
b4ca1a81 | 2101 | int check(const char *_objname, bool orc) |
dcc914f4 JP |
2102 | { |
2103 | struct objtool_file file; | |
2104 | int ret, warnings = 0; | |
2105 | ||
2106 | objname = _objname; | |
dcc914f4 | 2107 | |
627fce14 | 2108 | file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2109 | if (!file.elf) |
dcc914f4 | 2110 | return 1; |
dcc914f4 JP |
2111 | |
2112 | INIT_LIST_HEAD(&file.insn_list); | |
2113 | hash_init(file.insn_hash); | |
2114 | file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); | |
2115 | file.rodata = find_section_by_name(file.elf, ".rodata"); | |
dcc914f4 | 2116 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2117 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2118 | file.hints = false; |
dcc914f4 | 2119 | |
baa41469 JP |
2120 | arch_initial_func_cfi_state(&initial_func_cfi); |
2121 | ||
dcc914f4 JP |
2122 | ret = decode_sections(&file); |
2123 | if (ret < 0) | |
2124 | goto out; | |
2125 | warnings += ret; | |
2126 | ||
baa41469 | 2127 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2128 | goto out; |
dcc914f4 | 2129 | |
cb83ad28 PZ |
2130 | if (retpoline) { |
2131 | ret = validate_retpoline(&file); | |
2132 | if (ret < 0) | |
2133 | return ret; | |
2134 | warnings += ret; | |
2135 | } | |
2136 | ||
baa41469 | 2137 | ret = validate_functions(&file); |
dcc914f4 JP |
2138 | if (ret < 0) |
2139 | goto out; | |
2140 | warnings += ret; | |
2141 | ||
39358a03 JP |
2142 | ret = validate_unwind_hints(&file); |
2143 | if (ret < 0) | |
2144 | goto out; | |
2145 | warnings += ret; | |
2146 | ||
baa41469 JP |
2147 | if (!warnings) { |
2148 | ret = validate_reachable_instructions(&file); | |
2149 | if (ret < 0) | |
2150 | goto out; | |
2151 | warnings += ret; | |
2152 | } | |
2153 | ||
627fce14 JP |
2154 | if (orc) { |
2155 | ret = create_orc(&file); | |
2156 | if (ret < 0) | |
2157 | goto out; | |
2158 | ||
2159 | ret = create_orc_sections(&file); | |
2160 | if (ret < 0) | |
2161 | goto out; | |
2162 | ||
2163 | ret = elf_write(file.elf); | |
2164 | if (ret < 0) | |
2165 | goto out; | |
2166 | } | |
2167 | ||
dcc914f4 JP |
2168 | out: |
2169 | cleanup(&file); | |
2170 | ||
2171 | /* ignore warnings for now until we get all the code cleaned up */ | |
2172 | if (ret || warnings) | |
2173 | return 0; | |
2174 | return 0; | |
2175 | } |