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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 | ||
43a4525f | 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", | |
b394d468 | 141 | "usercopy_abort", |
dcc914f4 JP |
142 | }; |
143 | ||
144 | if (func->bind == STB_WEAK) | |
145 | return 0; | |
146 | ||
147 | if (func->bind == STB_GLOBAL) | |
148 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
149 | if (!strcmp(func->name, global_noreturns[i])) | |
150 | return 1; | |
151 | ||
152 | if (!func->sec) | |
153 | return 0; | |
154 | ||
155 | func_for_each_insn(file, func, insn) { | |
156 | empty = false; | |
157 | ||
158 | if (insn->type == INSN_RETURN) | |
159 | return 0; | |
160 | } | |
161 | ||
162 | if (empty) | |
163 | return 0; | |
164 | ||
165 | /* | |
166 | * A function can have a sibling call instead of a return. In that | |
167 | * case, the function's dead-end status depends on whether the target | |
168 | * of the sibling call returns. | |
169 | */ | |
170 | func_for_each_insn(file, func, insn) { | |
171 | if (insn->sec != func->sec || | |
172 | insn->offset >= func->offset + func->len) | |
173 | break; | |
174 | ||
175 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { | |
176 | struct instruction *dest = insn->jump_dest; | |
177 | struct symbol *dest_func; | |
178 | ||
179 | if (!dest) | |
180 | /* sibling call to another file */ | |
181 | return 0; | |
182 | ||
183 | if (dest->sec != func->sec || | |
184 | dest->offset < func->offset || | |
185 | dest->offset >= func->offset + func->len) { | |
186 | /* local sibling call */ | |
187 | dest_func = find_symbol_by_offset(dest->sec, | |
188 | dest->offset); | |
189 | if (!dest_func) | |
190 | continue; | |
191 | ||
192 | if (recursion == 5) { | |
0afd0d9e JP |
193 | /* |
194 | * Infinite recursion: two functions | |
195 | * have sibling calls to each other. | |
196 | * This is a very rare case. It means | |
197 | * they aren't dead ends. | |
198 | */ | |
199 | return 0; | |
dcc914f4 JP |
200 | } |
201 | ||
202 | return __dead_end_function(file, dest_func, | |
203 | recursion + 1); | |
204 | } | |
205 | } | |
206 | ||
207 | if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts)) | |
208 | /* sibling call */ | |
209 | return 0; | |
210 | } | |
211 | ||
212 | return 1; | |
213 | } | |
214 | ||
215 | static int dead_end_function(struct objtool_file *file, struct symbol *func) | |
216 | { | |
217 | return __dead_end_function(file, func, 0); | |
218 | } | |
219 | ||
baa41469 JP |
220 | static void clear_insn_state(struct insn_state *state) |
221 | { | |
222 | int i; | |
223 | ||
224 | memset(state, 0, sizeof(*state)); | |
225 | state->cfa.base = CFI_UNDEFINED; | |
dd88a0a0 | 226 | for (i = 0; i < CFI_NUM_REGS; i++) { |
baa41469 | 227 | state->regs[i].base = CFI_UNDEFINED; |
dd88a0a0 JP |
228 | state->vals[i].base = CFI_UNDEFINED; |
229 | } | |
baa41469 | 230 | state->drap_reg = CFI_UNDEFINED; |
bf4d1a83 | 231 | state->drap_offset = -1; |
baa41469 JP |
232 | } |
233 | ||
dcc914f4 JP |
234 | /* |
235 | * Call the arch-specific instruction decoder for all the instructions and add | |
236 | * them to the global instruction list. | |
237 | */ | |
238 | static int decode_instructions(struct objtool_file *file) | |
239 | { | |
240 | struct section *sec; | |
241 | struct symbol *func; | |
242 | unsigned long offset; | |
243 | struct instruction *insn; | |
244 | int ret; | |
245 | ||
baa41469 | 246 | for_each_sec(file, sec) { |
dcc914f4 JP |
247 | |
248 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
249 | continue; | |
250 | ||
627fce14 JP |
251 | if (strcmp(sec->name, ".altinstr_replacement") && |
252 | strcmp(sec->name, ".altinstr_aux") && | |
253 | strncmp(sec->name, ".discard.", 9)) | |
254 | sec->text = true; | |
255 | ||
dcc914f4 JP |
256 | for (offset = 0; offset < sec->len; offset += insn->len) { |
257 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
258 | if (!insn) { |
259 | WARN("malloc failed"); | |
260 | return -1; | |
261 | } | |
dcc914f4 | 262 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 263 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
264 | clear_insn_state(&insn->state); |
265 | ||
dcc914f4 JP |
266 | insn->sec = sec; |
267 | insn->offset = offset; | |
268 | ||
269 | ret = arch_decode_instruction(file->elf, sec, offset, | |
270 | sec->len - offset, | |
271 | &insn->len, &insn->type, | |
baa41469 JP |
272 | &insn->immediate, |
273 | &insn->stack_op); | |
dcc914f4 | 274 | if (ret) |
b7037983 | 275 | goto err; |
dcc914f4 JP |
276 | |
277 | if (!insn->type || insn->type > INSN_LAST) { | |
278 | WARN_FUNC("invalid instruction type %d", | |
279 | insn->sec, insn->offset, insn->type); | |
b7037983 KB |
280 | ret = -1; |
281 | goto err; | |
dcc914f4 JP |
282 | } |
283 | ||
284 | hash_add(file->insn_hash, &insn->hash, insn->offset); | |
285 | list_add_tail(&insn->list, &file->insn_list); | |
286 | } | |
287 | ||
288 | list_for_each_entry(func, &sec->symbol_list, list) { | |
289 | if (func->type != STT_FUNC) | |
290 | continue; | |
291 | ||
292 | if (!find_insn(file, sec, func->offset)) { | |
293 | WARN("%s(): can't find starting instruction", | |
294 | func->name); | |
295 | return -1; | |
296 | } | |
297 | ||
298 | func_for_each_insn(file, func, insn) | |
299 | if (!insn->func) | |
300 | insn->func = func; | |
301 | } | |
302 | } | |
303 | ||
304 | return 0; | |
b7037983 KB |
305 | |
306 | err: | |
307 | free(insn); | |
308 | return ret; | |
dcc914f4 JP |
309 | } |
310 | ||
311 | /* | |
649ea4d5 | 312 | * Mark "ud2" instructions and manually annotated dead ends. |
dcc914f4 JP |
313 | */ |
314 | static int add_dead_ends(struct objtool_file *file) | |
315 | { | |
316 | struct section *sec; | |
317 | struct rela *rela; | |
318 | struct instruction *insn; | |
319 | bool found; | |
320 | ||
649ea4d5 JP |
321 | /* |
322 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
323 | * GCC 7 inserts it for certain divide-by-zero cases. | |
324 | */ | |
325 | for_each_insn(file, insn) | |
326 | if (insn->type == INSN_BUG) | |
327 | insn->dead_end = true; | |
328 | ||
329 | /* | |
330 | * Check for manually annotated dead ends. | |
331 | */ | |
dcc914f4 JP |
332 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
333 | if (!sec) | |
649ea4d5 | 334 | goto reachable; |
dcc914f4 JP |
335 | |
336 | list_for_each_entry(rela, &sec->rela_list, list) { | |
337 | if (rela->sym->type != STT_SECTION) { | |
338 | WARN("unexpected relocation symbol type in %s", sec->name); | |
339 | return -1; | |
340 | } | |
341 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
342 | if (insn) | |
343 | insn = list_prev_entry(insn, list); | |
344 | else if (rela->addend == rela->sym->sec->len) { | |
345 | found = false; | |
346 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
347 | if (insn->sec == rela->sym->sec) { | |
348 | found = true; | |
349 | break; | |
350 | } | |
351 | } | |
352 | ||
353 | if (!found) { | |
354 | WARN("can't find unreachable insn at %s+0x%x", | |
355 | rela->sym->sec->name, rela->addend); | |
356 | return -1; | |
357 | } | |
358 | } else { | |
359 | WARN("can't find unreachable insn at %s+0x%x", | |
360 | rela->sym->sec->name, rela->addend); | |
361 | return -1; | |
362 | } | |
363 | ||
364 | insn->dead_end = true; | |
365 | } | |
366 | ||
649ea4d5 JP |
367 | reachable: |
368 | /* | |
369 | * These manually annotated reachable checks are needed for GCC 4.4, | |
370 | * where the Linux unreachable() macro isn't supported. In that case | |
371 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
372 | * not a dead end. | |
373 | */ | |
374 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
375 | if (!sec) | |
376 | return 0; | |
377 | ||
378 | list_for_each_entry(rela, &sec->rela_list, list) { | |
379 | if (rela->sym->type != STT_SECTION) { | |
380 | WARN("unexpected relocation symbol type in %s", sec->name); | |
381 | return -1; | |
382 | } | |
383 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
384 | if (insn) | |
385 | insn = list_prev_entry(insn, list); | |
386 | else if (rela->addend == rela->sym->sec->len) { | |
387 | found = false; | |
388 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
389 | if (insn->sec == rela->sym->sec) { | |
390 | found = true; | |
391 | break; | |
392 | } | |
393 | } | |
394 | ||
395 | if (!found) { | |
396 | WARN("can't find reachable insn at %s+0x%x", | |
397 | rela->sym->sec->name, rela->addend); | |
398 | return -1; | |
399 | } | |
400 | } else { | |
401 | WARN("can't find reachable insn at %s+0x%x", | |
402 | rela->sym->sec->name, rela->addend); | |
403 | return -1; | |
404 | } | |
405 | ||
406 | insn->dead_end = false; | |
407 | } | |
408 | ||
dcc914f4 JP |
409 | return 0; |
410 | } | |
411 | ||
412 | /* | |
413 | * Warnings shouldn't be reported for ignored functions. | |
414 | */ | |
415 | static void add_ignores(struct objtool_file *file) | |
416 | { | |
417 | struct instruction *insn; | |
418 | struct section *sec; | |
419 | struct symbol *func; | |
420 | ||
baa41469 | 421 | for_each_sec(file, sec) { |
dcc914f4 JP |
422 | list_for_each_entry(func, &sec->symbol_list, list) { |
423 | if (func->type != STT_FUNC) | |
424 | continue; | |
425 | ||
426 | if (!ignore_func(file, func)) | |
427 | continue; | |
428 | ||
429 | func_for_each_insn(file, func, insn) | |
baa41469 | 430 | insn->ignore = true; |
dcc914f4 JP |
431 | } |
432 | } | |
433 | } | |
434 | ||
258c7605 JP |
435 | /* |
436 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
437 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
438 | * But it at least allows objtool to understand the control flow *around* the | |
439 | * retpoline. | |
440 | */ | |
441 | static int add_nospec_ignores(struct objtool_file *file) | |
442 | { | |
443 | struct section *sec; | |
444 | struct rela *rela; | |
445 | struct instruction *insn; | |
446 | ||
447 | sec = find_section_by_name(file->elf, ".rela.discard.nospec"); | |
448 | if (!sec) | |
449 | return 0; | |
450 | ||
451 | list_for_each_entry(rela, &sec->rela_list, list) { | |
452 | if (rela->sym->type != STT_SECTION) { | |
453 | WARN("unexpected relocation symbol type in %s", sec->name); | |
454 | return -1; | |
455 | } | |
456 | ||
457 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
458 | if (!insn) { | |
459 | WARN("bad .discard.nospec entry"); | |
460 | return -1; | |
461 | } | |
462 | ||
463 | insn->ignore_alts = true; | |
464 | } | |
465 | ||
466 | return 0; | |
467 | } | |
468 | ||
dcc914f4 JP |
469 | /* |
470 | * Find the destination instructions for all jumps. | |
471 | */ | |
472 | static int add_jump_destinations(struct objtool_file *file) | |
473 | { | |
474 | struct instruction *insn; | |
475 | struct rela *rela; | |
476 | struct section *dest_sec; | |
477 | unsigned long dest_off; | |
478 | ||
479 | for_each_insn(file, insn) { | |
480 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
481 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
482 | continue; | |
483 | ||
baa41469 | 484 | if (insn->ignore) |
dcc914f4 JP |
485 | continue; |
486 | ||
487 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
488 | insn->len); | |
489 | if (!rela) { | |
490 | dest_sec = insn->sec; | |
491 | dest_off = insn->offset + insn->len + insn->immediate; | |
492 | } else if (rela->sym->type == STT_SECTION) { | |
493 | dest_sec = rela->sym->sec; | |
494 | dest_off = rela->addend + 4; | |
495 | } else if (rela->sym->sec->idx) { | |
496 | dest_sec = rela->sym->sec; | |
497 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
498 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
499 | /* | |
500 | * Retpoline jumps are really dynamic jumps in | |
501 | * disguise, so convert them accordingly. | |
502 | */ | |
503 | insn->type = INSN_JUMP_DYNAMIC; | |
b5bc2231 | 504 | insn->retpoline_safe = true; |
39b73533 | 505 | continue; |
dcc914f4 JP |
506 | } else { |
507 | /* sibling call */ | |
508 | insn->jump_dest = 0; | |
509 | continue; | |
510 | } | |
511 | ||
512 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
513 | if (!insn->jump_dest) { | |
514 | ||
515 | /* | |
516 | * This is a special case where an alt instruction | |
517 | * jumps past the end of the section. These are | |
518 | * handled later in handle_group_alt(). | |
519 | */ | |
520 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
521 | continue; | |
522 | ||
523 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
524 | insn->sec, insn->offset, dest_sec->name, | |
525 | dest_off); | |
526 | return -1; | |
527 | } | |
528 | } | |
529 | ||
530 | return 0; | |
531 | } | |
532 | ||
533 | /* | |
534 | * Find the destination instructions for all calls. | |
535 | */ | |
536 | static int add_call_destinations(struct objtool_file *file) | |
537 | { | |
538 | struct instruction *insn; | |
539 | unsigned long dest_off; | |
540 | struct rela *rela; | |
541 | ||
542 | for_each_insn(file, insn) { | |
543 | if (insn->type != INSN_CALL) | |
544 | continue; | |
545 | ||
546 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
547 | insn->len); | |
548 | if (!rela) { | |
549 | dest_off = insn->offset + insn->len + insn->immediate; | |
550 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
551 | dest_off); | |
a845c7cf JP |
552 | |
553 | if (!insn->call_dest && !insn->ignore) { | |
554 | WARN_FUNC("unsupported intra-function call", | |
555 | insn->sec, insn->offset); | |
b5bc2231 PZ |
556 | if (retpoline) |
557 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
558 | return -1; |
559 | } | |
a845c7cf | 560 | |
dcc914f4 JP |
561 | } else if (rela->sym->type == STT_SECTION) { |
562 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
563 | rela->addend+4); | |
564 | if (!insn->call_dest || | |
565 | insn->call_dest->type != STT_FUNC) { | |
566 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
567 | insn->sec, insn->offset, | |
568 | rela->sym->sec->name, | |
569 | rela->addend + 4); | |
570 | return -1; | |
571 | } | |
572 | } else | |
573 | insn->call_dest = rela->sym; | |
574 | } | |
575 | ||
576 | return 0; | |
577 | } | |
578 | ||
579 | /* | |
580 | * The .alternatives section requires some extra special care, over and above | |
581 | * what other special sections require: | |
582 | * | |
583 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
584 | * instruction at the end so that validate_branch() skips all the original | |
585 | * replaced instructions when validating the new instruction path. | |
586 | * | |
587 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
588 | * that case the old instructions are replaced with noops. We simulate that | |
589 | * by creating a fake jump as the only new instruction. | |
590 | * | |
591 | * 3. In some cases, the alternative section includes an instruction which | |
592 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
593 | * jumps' destinations to point back to .text rather than the end of the | |
594 | * entry in .altinstr_replacement. | |
595 | * | |
596 | * 4. It has been requested that we don't validate the !POPCNT feature path | |
597 | * which is a "very very small percentage of machines". | |
598 | */ | |
599 | static int handle_group_alt(struct objtool_file *file, | |
600 | struct special_alt *special_alt, | |
601 | struct instruction *orig_insn, | |
602 | struct instruction **new_insn) | |
603 | { | |
17bc3391 | 604 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
605 | unsigned long dest_off; |
606 | ||
607 | last_orig_insn = NULL; | |
608 | insn = orig_insn; | |
609 | sec_for_each_insn_from(file, insn) { | |
610 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
611 | break; | |
612 | ||
613 | if (special_alt->skip_orig) | |
614 | insn->type = INSN_NOP; | |
615 | ||
616 | insn->alt_group = true; | |
617 | last_orig_insn = insn; | |
618 | } | |
619 | ||
17bc3391 JP |
620 | if (next_insn_same_sec(file, last_orig_insn)) { |
621 | fake_jump = malloc(sizeof(*fake_jump)); | |
622 | if (!fake_jump) { | |
623 | WARN("malloc failed"); | |
624 | return -1; | |
625 | } | |
626 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
627 | INIT_LIST_HEAD(&fake_jump->alts); | |
628 | clear_insn_state(&fake_jump->state); | |
629 | ||
630 | fake_jump->sec = special_alt->new_sec; | |
631 | fake_jump->offset = -1; | |
632 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; | |
633 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
634 | fake_jump->ignore = true; | |
dcc914f4 | 635 | } |
dcc914f4 JP |
636 | |
637 | if (!special_alt->new_len) { | |
17bc3391 JP |
638 | if (!fake_jump) { |
639 | WARN("%s: empty alternative at end of section", | |
640 | special_alt->orig_sec->name); | |
641 | return -1; | |
642 | } | |
643 | ||
dcc914f4 JP |
644 | *new_insn = fake_jump; |
645 | return 0; | |
646 | } | |
647 | ||
648 | last_new_insn = NULL; | |
649 | insn = *new_insn; | |
650 | sec_for_each_insn_from(file, insn) { | |
651 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
652 | break; | |
653 | ||
654 | last_new_insn = insn; | |
655 | ||
a845c7cf JP |
656 | insn->ignore = orig_insn->ignore_alts; |
657 | ||
dcc914f4 JP |
658 | if (insn->type != INSN_JUMP_CONDITIONAL && |
659 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
660 | continue; | |
661 | ||
662 | if (!insn->immediate) | |
663 | continue; | |
664 | ||
665 | dest_off = insn->offset + insn->len + insn->immediate; | |
17bc3391 JP |
666 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
667 | if (!fake_jump) { | |
668 | WARN("%s: alternative jump to end of section", | |
669 | special_alt->orig_sec->name); | |
670 | return -1; | |
671 | } | |
dcc914f4 | 672 | insn->jump_dest = fake_jump; |
17bc3391 | 673 | } |
dcc914f4 JP |
674 | |
675 | if (!insn->jump_dest) { | |
676 | WARN_FUNC("can't find alternative jump destination", | |
677 | insn->sec, insn->offset); | |
678 | return -1; | |
679 | } | |
680 | } | |
681 | ||
682 | if (!last_new_insn) { | |
683 | WARN_FUNC("can't find last new alternative instruction", | |
684 | special_alt->new_sec, special_alt->new_off); | |
685 | return -1; | |
686 | } | |
687 | ||
17bc3391 JP |
688 | if (fake_jump) |
689 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
690 | |
691 | return 0; | |
692 | } | |
693 | ||
694 | /* | |
695 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
696 | * If the original instruction is a jump, make the alt entry an effective nop | |
697 | * by just skipping the original instruction. | |
698 | */ | |
699 | static int handle_jump_alt(struct objtool_file *file, | |
700 | struct special_alt *special_alt, | |
701 | struct instruction *orig_insn, | |
702 | struct instruction **new_insn) | |
703 | { | |
704 | if (orig_insn->type == INSN_NOP) | |
705 | return 0; | |
706 | ||
707 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
708 | WARN_FUNC("unsupported instruction at jump label", | |
709 | orig_insn->sec, orig_insn->offset); | |
710 | return -1; | |
711 | } | |
712 | ||
713 | *new_insn = list_next_entry(orig_insn, list); | |
714 | return 0; | |
715 | } | |
716 | ||
717 | /* | |
718 | * Read all the special sections which have alternate instructions which can be | |
719 | * patched in or redirected to at runtime. Each instruction having alternate | |
720 | * instruction(s) has them added to its insn->alts list, which will be | |
721 | * traversed in validate_branch(). | |
722 | */ | |
723 | static int add_special_section_alts(struct objtool_file *file) | |
724 | { | |
725 | struct list_head special_alts; | |
726 | struct instruction *orig_insn, *new_insn; | |
727 | struct special_alt *special_alt, *tmp; | |
728 | struct alternative *alt; | |
729 | int ret; | |
730 | ||
731 | ret = special_get_alts(file->elf, &special_alts); | |
732 | if (ret) | |
733 | return ret; | |
734 | ||
735 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
736 | |
737 | orig_insn = find_insn(file, special_alt->orig_sec, | |
738 | special_alt->orig_off); | |
739 | if (!orig_insn) { | |
740 | WARN_FUNC("special: can't find orig instruction", | |
741 | special_alt->orig_sec, special_alt->orig_off); | |
742 | ret = -1; | |
743 | goto out; | |
744 | } | |
745 | ||
746 | new_insn = NULL; | |
747 | if (!special_alt->group || special_alt->new_len) { | |
748 | new_insn = find_insn(file, special_alt->new_sec, | |
749 | special_alt->new_off); | |
750 | if (!new_insn) { | |
751 | WARN_FUNC("special: can't find new instruction", | |
752 | special_alt->new_sec, | |
753 | special_alt->new_off); | |
754 | ret = -1; | |
755 | goto out; | |
756 | } | |
757 | } | |
758 | ||
759 | if (special_alt->group) { | |
760 | ret = handle_group_alt(file, special_alt, orig_insn, | |
761 | &new_insn); | |
762 | if (ret) | |
763 | goto out; | |
764 | } else if (special_alt->jump_or_nop) { | |
765 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
766 | &new_insn); | |
767 | if (ret) | |
768 | goto out; | |
769 | } | |
770 | ||
258c7605 JP |
771 | alt = malloc(sizeof(*alt)); |
772 | if (!alt) { | |
773 | WARN("malloc failed"); | |
774 | ret = -1; | |
775 | goto out; | |
776 | } | |
777 | ||
dcc914f4 JP |
778 | alt->insn = new_insn; |
779 | list_add_tail(&alt->list, &orig_insn->alts); | |
780 | ||
781 | list_del(&special_alt->list); | |
782 | free(special_alt); | |
783 | } | |
784 | ||
785 | out: | |
786 | return ret; | |
787 | } | |
788 | ||
789 | static int add_switch_table(struct objtool_file *file, struct symbol *func, | |
790 | struct instruction *insn, struct rela *table, | |
791 | struct rela *next_table) | |
792 | { | |
793 | struct rela *rela = table; | |
794 | struct instruction *alt_insn; | |
795 | struct alternative *alt; | |
796 | ||
797 | list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { | |
798 | if (rela == next_table) | |
799 | break; | |
800 | ||
801 | if (rela->sym->sec != insn->sec || | |
802 | rela->addend <= func->offset || | |
803 | rela->addend >= func->offset + func->len) | |
804 | break; | |
805 | ||
806 | alt_insn = find_insn(file, insn->sec, rela->addend); | |
807 | if (!alt_insn) { | |
808 | WARN("%s: can't find instruction at %s+0x%x", | |
809 | file->rodata->rela->name, insn->sec->name, | |
810 | rela->addend); | |
811 | return -1; | |
812 | } | |
813 | ||
814 | alt = malloc(sizeof(*alt)); | |
815 | if (!alt) { | |
816 | WARN("malloc failed"); | |
817 | return -1; | |
818 | } | |
819 | ||
820 | alt->insn = alt_insn; | |
821 | list_add_tail(&alt->list, &insn->alts); | |
822 | } | |
823 | ||
824 | return 0; | |
825 | } | |
826 | ||
827 | /* | |
828 | * find_switch_table() - Given a dynamic jump, find the switch jump table in | |
829 | * .rodata associated with it. | |
830 | * | |
831 | * There are 3 basic patterns: | |
832 | * | |
833 | * 1. jmpq *[rodata addr](,%reg,8) | |
834 | * | |
835 | * This is the most common case by far. It jumps to an address in a simple | |
836 | * jump table which is stored in .rodata. | |
837 | * | |
838 | * 2. jmpq *[rodata addr](%rip) | |
839 | * | |
840 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
841 | * functions in the kernel, only with certain obscure non-distro configs. | |
842 | * | |
843 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
844 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
845 | * jump) to use a single entry in the table. The rest of the jump table and | |
846 | * some of its jump targets remain as dead code. | |
847 | * | |
848 | * In such a case we can just crudely ignore all unreachable instruction | |
849 | * warnings for the entire object file. Ideally we would just ignore them | |
850 | * for the function, but that would require redesigning the code quite a | |
851 | * bit. And honestly that's just not worth doing: unreachable instruction | |
852 | * warnings are of questionable value anyway, and this is such a rare issue. | |
853 | * | |
854 | * 3. mov [rodata addr],%reg1 | |
855 | * ... some instructions ... | |
856 | * jmpq *(%reg1,%reg2,8) | |
857 | * | |
858 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
859 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
860 | * | |
99ce7962 PZ |
861 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
862 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
863 | * and jmpq uses .rodata itself, which can confuse things. | |
864 | * | |
dcc914f4 JP |
865 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
866 | * ensure the same register is used in the mov and jump instructions. | |
99ce7962 PZ |
867 | * |
868 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 JP |
869 | */ |
870 | static struct rela *find_switch_table(struct objtool_file *file, | |
871 | struct symbol *func, | |
872 | struct instruction *insn) | |
873 | { | |
874 | struct rela *text_rela, *rodata_rela; | |
875 | struct instruction *orig_insn = insn; | |
876 | ||
877 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); | |
878 | if (text_rela && text_rela->sym == file->rodata->sym) { | |
879 | /* case 1 */ | |
880 | rodata_rela = find_rela_by_dest(file->rodata, | |
881 | text_rela->addend); | |
882 | if (rodata_rela) | |
883 | return rodata_rela; | |
884 | ||
885 | /* case 2 */ | |
886 | rodata_rela = find_rela_by_dest(file->rodata, | |
887 | text_rela->addend + 4); | |
888 | if (!rodata_rela) | |
889 | return NULL; | |
99ce7962 | 890 | |
dcc914f4 JP |
891 | file->ignore_unreachables = true; |
892 | return rodata_rela; | |
893 | } | |
894 | ||
895 | /* case 3 */ | |
99ce7962 PZ |
896 | /* |
897 | * Backward search using the @first_jump_src links, these help avoid | |
898 | * much of the 'in between' code. Which avoids us getting confused by | |
899 | * it. | |
900 | */ | |
901 | for (insn = list_prev_entry(insn, list); | |
902 | ||
903 | &insn->list != &file->insn_list && | |
904 | insn->sec == func->sec && | |
905 | insn->offset >= func->offset; | |
906 | ||
907 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { | |
908 | ||
dcc914f4 JP |
909 | if (insn->type == INSN_JUMP_DYNAMIC) |
910 | break; | |
911 | ||
912 | /* allow small jumps within the range */ | |
913 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
914 | insn->jump_dest && | |
915 | (insn->jump_dest->offset <= insn->offset || | |
916 | insn->jump_dest->offset > orig_insn->offset)) | |
917 | break; | |
918 | ||
919 | /* look for a relocation which references .rodata */ | |
920 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
921 | insn->len); | |
922 | if (!text_rela || text_rela->sym != file->rodata->sym) | |
923 | continue; | |
924 | ||
925 | /* | |
926 | * Make sure the .rodata address isn't associated with a | |
927 | * symbol. gcc jump tables are anonymous data. | |
928 | */ | |
929 | if (find_symbol_containing(file->rodata, text_rela->addend)) | |
930 | continue; | |
931 | ||
1402fd8e JP |
932 | rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend); |
933 | if (!rodata_rela) | |
934 | continue; | |
935 | ||
936 | return rodata_rela; | |
dcc914f4 JP |
937 | } |
938 | ||
939 | return NULL; | |
940 | } | |
941 | ||
99ce7962 | 942 | |
dcc914f4 JP |
943 | static int add_func_switch_tables(struct objtool_file *file, |
944 | struct symbol *func) | |
945 | { | |
99ce7962 | 946 | struct instruction *insn, *last = NULL, *prev_jump = NULL; |
dcc914f4 JP |
947 | struct rela *rela, *prev_rela = NULL; |
948 | int ret; | |
949 | ||
950 | func_for_each_insn(file, func, insn) { | |
99ce7962 PZ |
951 | if (!last) |
952 | last = insn; | |
953 | ||
954 | /* | |
955 | * Store back-pointers for unconditional forward jumps such | |
956 | * that find_switch_table() can back-track using those and | |
957 | * avoid some potentially confusing code. | |
958 | */ | |
959 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
960 | insn->offset > last->offset && | |
961 | insn->jump_dest->offset > insn->offset && | |
962 | !insn->jump_dest->first_jump_src) { | |
963 | ||
964 | insn->jump_dest->first_jump_src = insn; | |
965 | last = insn->jump_dest; | |
966 | } | |
967 | ||
dcc914f4 JP |
968 | if (insn->type != INSN_JUMP_DYNAMIC) |
969 | continue; | |
970 | ||
971 | rela = find_switch_table(file, func, insn); | |
972 | if (!rela) | |
973 | continue; | |
974 | ||
975 | /* | |
976 | * We found a switch table, but we don't know yet how big it | |
977 | * is. Don't add it until we reach the end of the function or | |
978 | * the beginning of another switch table in the same function. | |
979 | */ | |
980 | if (prev_jump) { | |
981 | ret = add_switch_table(file, func, prev_jump, prev_rela, | |
982 | rela); | |
983 | if (ret) | |
984 | return ret; | |
985 | } | |
986 | ||
987 | prev_jump = insn; | |
988 | prev_rela = rela; | |
989 | } | |
990 | ||
991 | if (prev_jump) { | |
992 | ret = add_switch_table(file, func, prev_jump, prev_rela, NULL); | |
993 | if (ret) | |
994 | return ret; | |
995 | } | |
996 | ||
997 | return 0; | |
998 | } | |
999 | ||
1000 | /* | |
1001 | * For some switch statements, gcc generates a jump table in the .rodata | |
1002 | * section which contains a list of addresses within the function to jump to. | |
1003 | * This finds these jump tables and adds them to the insn->alts lists. | |
1004 | */ | |
1005 | static int add_switch_table_alts(struct objtool_file *file) | |
1006 | { | |
1007 | struct section *sec; | |
1008 | struct symbol *func; | |
1009 | int ret; | |
1010 | ||
1011 | if (!file->rodata || !file->rodata->rela) | |
1012 | return 0; | |
1013 | ||
baa41469 | 1014 | for_each_sec(file, sec) { |
dcc914f4 JP |
1015 | list_for_each_entry(func, &sec->symbol_list, list) { |
1016 | if (func->type != STT_FUNC) | |
1017 | continue; | |
1018 | ||
1019 | ret = add_func_switch_tables(file, func); | |
1020 | if (ret) | |
1021 | return ret; | |
1022 | } | |
1023 | } | |
1024 | ||
1025 | return 0; | |
1026 | } | |
1027 | ||
39358a03 JP |
1028 | static int read_unwind_hints(struct objtool_file *file) |
1029 | { | |
1030 | struct section *sec, *relasec; | |
1031 | struct rela *rela; | |
1032 | struct unwind_hint *hint; | |
1033 | struct instruction *insn; | |
1034 | struct cfi_reg *cfa; | |
1035 | int i; | |
1036 | ||
1037 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1038 | if (!sec) | |
1039 | return 0; | |
1040 | ||
1041 | relasec = sec->rela; | |
1042 | if (!relasec) { | |
1043 | WARN("missing .rela.discard.unwind_hints section"); | |
1044 | return -1; | |
1045 | } | |
1046 | ||
1047 | if (sec->len % sizeof(struct unwind_hint)) { | |
1048 | WARN("struct unwind_hint size mismatch"); | |
1049 | return -1; | |
1050 | } | |
1051 | ||
1052 | file->hints = true; | |
1053 | ||
1054 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1055 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1056 | ||
1057 | rela = find_rela_by_dest(sec, i * sizeof(*hint)); | |
1058 | if (!rela) { | |
1059 | WARN("can't find rela for unwind_hints[%d]", i); | |
1060 | return -1; | |
1061 | } | |
1062 | ||
1063 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1064 | if (!insn) { | |
1065 | WARN("can't find insn for unwind_hints[%d]", i); | |
1066 | return -1; | |
1067 | } | |
1068 | ||
1069 | cfa = &insn->state.cfa; | |
1070 | ||
1071 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1072 | insn->save = true; | |
1073 | continue; | |
1074 | ||
1075 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1076 | insn->restore = true; | |
1077 | insn->hint = true; | |
1078 | continue; | |
1079 | } | |
1080 | ||
1081 | insn->hint = true; | |
1082 | ||
1083 | switch (hint->sp_reg) { | |
1084 | case ORC_REG_UNDEFINED: | |
1085 | cfa->base = CFI_UNDEFINED; | |
1086 | break; | |
1087 | case ORC_REG_SP: | |
1088 | cfa->base = CFI_SP; | |
1089 | break; | |
1090 | case ORC_REG_BP: | |
1091 | cfa->base = CFI_BP; | |
1092 | break; | |
1093 | case ORC_REG_SP_INDIRECT: | |
1094 | cfa->base = CFI_SP_INDIRECT; | |
1095 | break; | |
1096 | case ORC_REG_R10: | |
1097 | cfa->base = CFI_R10; | |
1098 | break; | |
1099 | case ORC_REG_R13: | |
1100 | cfa->base = CFI_R13; | |
1101 | break; | |
1102 | case ORC_REG_DI: | |
1103 | cfa->base = CFI_DI; | |
1104 | break; | |
1105 | case ORC_REG_DX: | |
1106 | cfa->base = CFI_DX; | |
1107 | break; | |
1108 | default: | |
1109 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1110 | insn->sec, insn->offset, hint->sp_reg); | |
1111 | return -1; | |
1112 | } | |
1113 | ||
1114 | cfa->offset = hint->sp_offset; | |
1115 | insn->state.type = hint->type; | |
1116 | } | |
1117 | ||
1118 | return 0; | |
1119 | } | |
1120 | ||
b5bc2231 PZ |
1121 | static int read_retpoline_hints(struct objtool_file *file) |
1122 | { | |
63474dc4 | 1123 | struct section *sec; |
b5bc2231 PZ |
1124 | struct instruction *insn; |
1125 | struct rela *rela; | |
b5bc2231 | 1126 | |
63474dc4 | 1127 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
b5bc2231 PZ |
1128 | if (!sec) |
1129 | return 0; | |
1130 | ||
63474dc4 JP |
1131 | list_for_each_entry(rela, &sec->rela_list, list) { |
1132 | if (rela->sym->type != STT_SECTION) { | |
1133 | WARN("unexpected relocation symbol type in %s", sec->name); | |
b5bc2231 PZ |
1134 | return -1; |
1135 | } | |
1136 | ||
1137 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1138 | if (!insn) { | |
63474dc4 | 1139 | WARN("bad .discard.retpoline_safe entry"); |
b5bc2231 PZ |
1140 | return -1; |
1141 | } | |
1142 | ||
1143 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1144 | insn->type != INSN_CALL_DYNAMIC) { | |
63474dc4 | 1145 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
b5bc2231 PZ |
1146 | insn->sec, insn->offset); |
1147 | return -1; | |
1148 | } | |
1149 | ||
1150 | insn->retpoline_safe = true; | |
1151 | } | |
1152 | ||
1153 | return 0; | |
1154 | } | |
1155 | ||
dcc914f4 JP |
1156 | static int decode_sections(struct objtool_file *file) |
1157 | { | |
1158 | int ret; | |
1159 | ||
1160 | ret = decode_instructions(file); | |
1161 | if (ret) | |
1162 | return ret; | |
1163 | ||
1164 | ret = add_dead_ends(file); | |
1165 | if (ret) | |
1166 | return ret; | |
1167 | ||
1168 | add_ignores(file); | |
1169 | ||
258c7605 JP |
1170 | ret = add_nospec_ignores(file); |
1171 | if (ret) | |
1172 | return ret; | |
1173 | ||
dcc914f4 JP |
1174 | ret = add_jump_destinations(file); |
1175 | if (ret) | |
1176 | return ret; | |
1177 | ||
a845c7cf | 1178 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1179 | if (ret) |
1180 | return ret; | |
1181 | ||
a845c7cf | 1182 | ret = add_call_destinations(file); |
dcc914f4 JP |
1183 | if (ret) |
1184 | return ret; | |
1185 | ||
1186 | ret = add_switch_table_alts(file); | |
1187 | if (ret) | |
1188 | return ret; | |
1189 | ||
39358a03 JP |
1190 | ret = read_unwind_hints(file); |
1191 | if (ret) | |
1192 | return ret; | |
1193 | ||
b5bc2231 PZ |
1194 | ret = read_retpoline_hints(file); |
1195 | if (ret) | |
1196 | return ret; | |
1197 | ||
dcc914f4 JP |
1198 | return 0; |
1199 | } | |
1200 | ||
1201 | static bool is_fentry_call(struct instruction *insn) | |
1202 | { | |
1203 | if (insn->type == INSN_CALL && | |
1204 | insn->call_dest->type == STT_NOTYPE && | |
1205 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1206 | return true; | |
1207 | ||
1208 | return false; | |
1209 | } | |
1210 | ||
baa41469 | 1211 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1212 | { |
baa41469 JP |
1213 | int i; |
1214 | ||
1215 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1216 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1217 | state->stack_size != initial_func_cfi.cfa.offset || | |
1218 | state->drap) | |
1219 | return true; | |
1220 | ||
1221 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1222 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1223 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1224 | return true; | |
1225 | ||
1226 | return false; | |
1227 | } | |
1228 | ||
1229 | static bool has_valid_stack_frame(struct insn_state *state) | |
1230 | { | |
1231 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1232 | state->regs[CFI_BP].offset == -16) | |
1233 | return true; | |
1234 | ||
1235 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1236 | return true; | |
1237 | ||
1238 | return false; | |
dcc914f4 JP |
1239 | } |
1240 | ||
627fce14 JP |
1241 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1242 | { | |
1243 | struct cfi_reg *cfa = &state->cfa; | |
1244 | struct stack_op *op = &insn->stack_op; | |
1245 | ||
1246 | if (cfa->base != CFI_SP) | |
1247 | return 0; | |
1248 | ||
1249 | /* push */ | |
1250 | if (op->dest.type == OP_DEST_PUSH) | |
1251 | cfa->offset += 8; | |
1252 | ||
1253 | /* pop */ | |
1254 | if (op->src.type == OP_SRC_POP) | |
1255 | cfa->offset -= 8; | |
1256 | ||
1257 | /* add immediate to sp */ | |
1258 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1259 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1260 | cfa->offset -= op->src.offset; | |
1261 | ||
1262 | return 0; | |
1263 | } | |
1264 | ||
baa41469 JP |
1265 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1266 | int offset) | |
dcc914f4 | 1267 | { |
bf4d1a83 | 1268 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1269 | state->regs[reg].base == CFI_UNDEFINED) { |
1270 | state->regs[reg].base = base; | |
1271 | state->regs[reg].offset = offset; | |
1272 | } | |
dcc914f4 JP |
1273 | } |
1274 | ||
baa41469 | 1275 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1276 | { |
baa41469 JP |
1277 | state->regs[reg].base = CFI_UNDEFINED; |
1278 | state->regs[reg].offset = 0; | |
1279 | } | |
1280 | ||
1281 | /* | |
1282 | * A note about DRAP stack alignment: | |
1283 | * | |
1284 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1285 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1286 | * register. The typical DRAP pattern is: | |
1287 | * | |
1288 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1289 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1290 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1291 | * 55 push %rbp | |
1292 | * 48 89 e5 mov %rsp,%rbp | |
1293 | * (more pushes) | |
1294 | * 41 52 push %r10 | |
1295 | * ... | |
1296 | * 41 5a pop %r10 | |
1297 | * (more pops) | |
1298 | * 5d pop %rbp | |
1299 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1300 | * c3 retq | |
1301 | * | |
1302 | * There are some variations in the epilogues, like: | |
1303 | * | |
1304 | * 5b pop %rbx | |
1305 | * 41 5a pop %r10 | |
1306 | * 41 5c pop %r12 | |
1307 | * 41 5d pop %r13 | |
1308 | * 41 5e pop %r14 | |
1309 | * c9 leaveq | |
1310 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1311 | * c3 retq | |
1312 | * | |
1313 | * and: | |
1314 | * | |
1315 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1316 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1317 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1318 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1319 | * c9 leaveq | |
1320 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1321 | * c3 retq | |
1322 | * | |
1323 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1324 | * restored beforehand: | |
1325 | * | |
1326 | * 41 55 push %r13 | |
1327 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1328 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1329 | * ... | |
1330 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1331 | * 41 5d pop %r13 | |
1332 | * c3 retq | |
1333 | */ | |
1334 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1335 | { | |
1336 | struct stack_op *op = &insn->stack_op; | |
1337 | struct cfi_reg *cfa = &state->cfa; | |
1338 | struct cfi_reg *regs = state->regs; | |
1339 | ||
1340 | /* stack operations don't make sense with an undefined CFA */ | |
1341 | if (cfa->base == CFI_UNDEFINED) { | |
1342 | if (insn->func) { | |
1343 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1344 | return -1; | |
1345 | } | |
1346 | return 0; | |
1347 | } | |
1348 | ||
627fce14 JP |
1349 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1350 | return update_insn_state_regs(insn, state); | |
1351 | ||
baa41469 JP |
1352 | switch (op->dest.type) { |
1353 | ||
1354 | case OP_DEST_REG: | |
1355 | switch (op->src.type) { | |
1356 | ||
1357 | case OP_SRC_REG: | |
0d0970ee JP |
1358 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1359 | cfa->base == CFI_SP && | |
1360 | regs[CFI_BP].base == CFI_CFA && | |
1361 | regs[CFI_BP].offset == -cfa->offset) { | |
1362 | ||
1363 | /* mov %rsp, %rbp */ | |
1364 | cfa->base = op->dest.reg; | |
1365 | state->bp_scratch = false; | |
1366 | } | |
dd88a0a0 | 1367 | |
0d0970ee JP |
1368 | else if (op->src.reg == CFI_SP && |
1369 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1370 | |
0d0970ee JP |
1371 | /* drap: mov %rsp, %rbp */ |
1372 | regs[CFI_BP].base = CFI_BP; | |
1373 | regs[CFI_BP].offset = -state->stack_size; | |
1374 | state->bp_scratch = false; | |
1375 | } | |
dd88a0a0 | 1376 | |
0d0970ee JP |
1377 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1378 | ||
1379 | /* | |
1380 | * mov %rsp, %reg | |
1381 | * | |
1382 | * This is needed for the rare case where GCC | |
1383 | * does: | |
1384 | * | |
1385 | * mov %rsp, %rax | |
1386 | * ... | |
1387 | * mov %rax, %rsp | |
1388 | */ | |
1389 | state->vals[op->dest.reg].base = CFI_CFA; | |
1390 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1391 | } |
1392 | ||
3c1f0583 JP |
1393 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
1394 | cfa->base == CFI_BP) { | |
1395 | ||
1396 | /* | |
1397 | * mov %rbp, %rsp | |
1398 | * | |
1399 | * Restore the original stack pointer (Clang). | |
1400 | */ | |
1401 | state->stack_size = -state->regs[CFI_BP].offset; | |
1402 | } | |
1403 | ||
dd88a0a0 JP |
1404 | else if (op->dest.reg == cfa->base) { |
1405 | ||
1406 | /* mov %reg, %rsp */ | |
1407 | if (cfa->base == CFI_SP && | |
1408 | state->vals[op->src.reg].base == CFI_CFA) { | |
1409 | ||
1410 | /* | |
1411 | * This is needed for the rare case | |
1412 | * where GCC does something dumb like: | |
1413 | * | |
1414 | * lea 0x8(%rsp), %rcx | |
1415 | * ... | |
1416 | * mov %rcx, %rsp | |
1417 | */ | |
1418 | cfa->offset = -state->vals[op->src.reg].offset; | |
1419 | state->stack_size = cfa->offset; | |
1420 | ||
1421 | } else { | |
1422 | cfa->base = CFI_UNDEFINED; | |
1423 | cfa->offset = 0; | |
1424 | } | |
baa41469 JP |
1425 | } |
1426 | ||
1427 | break; | |
1428 | ||
1429 | case OP_SRC_ADD: | |
1430 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1431 | ||
1432 | /* add imm, %rsp */ | |
1433 | state->stack_size -= op->src.offset; | |
1434 | if (cfa->base == CFI_SP) | |
1435 | cfa->offset -= op->src.offset; | |
1436 | break; | |
1437 | } | |
1438 | ||
1439 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1440 | ||
1441 | /* lea disp(%rbp), %rsp */ | |
1442 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1443 | break; | |
1444 | } | |
1445 | ||
dd88a0a0 | 1446 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1447 | |
1448 | /* drap: lea disp(%rsp), %drap */ | |
1449 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1450 | |
1451 | /* | |
1452 | * lea disp(%rsp), %reg | |
1453 | * | |
1454 | * This is needed for the rare case where GCC | |
1455 | * does something dumb like: | |
1456 | * | |
1457 | * lea 0x8(%rsp), %rcx | |
1458 | * ... | |
1459 | * mov %rcx, %rsp | |
1460 | */ | |
1461 | state->vals[op->dest.reg].base = CFI_CFA; | |
1462 | state->vals[op->dest.reg].offset = \ | |
1463 | -state->stack_size + op->src.offset; | |
1464 | ||
baa41469 JP |
1465 | break; |
1466 | } | |
1467 | ||
1468 | if (state->drap && op->dest.reg == CFI_SP && | |
1469 | op->src.reg == state->drap_reg) { | |
1470 | ||
1471 | /* drap: lea disp(%drap), %rsp */ | |
1472 | cfa->base = CFI_SP; | |
1473 | cfa->offset = state->stack_size = -op->src.offset; | |
1474 | state->drap_reg = CFI_UNDEFINED; | |
1475 | state->drap = false; | |
1476 | break; | |
1477 | } | |
1478 | ||
1479 | if (op->dest.reg == state->cfa.base) { | |
1480 | WARN_FUNC("unsupported stack register modification", | |
1481 | insn->sec, insn->offset); | |
1482 | return -1; | |
1483 | } | |
1484 | ||
1485 | break; | |
1486 | ||
1487 | case OP_SRC_AND: | |
1488 | if (op->dest.reg != CFI_SP || | |
1489 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1490 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1491 | WARN_FUNC("unsupported stack pointer realignment", | |
1492 | insn->sec, insn->offset); | |
1493 | return -1; | |
1494 | } | |
1495 | ||
1496 | if (state->drap_reg != CFI_UNDEFINED) { | |
1497 | /* drap: and imm, %rsp */ | |
1498 | cfa->base = state->drap_reg; | |
1499 | cfa->offset = state->stack_size = 0; | |
1500 | state->drap = true; | |
baa41469 JP |
1501 | } |
1502 | ||
1503 | /* | |
1504 | * Older versions of GCC (4.8ish) realign the stack | |
1505 | * without DRAP, with a frame pointer. | |
1506 | */ | |
1507 | ||
1508 | break; | |
1509 | ||
1510 | case OP_SRC_POP: | |
1511 | if (!state->drap && op->dest.type == OP_DEST_REG && | |
1512 | op->dest.reg == cfa->base) { | |
1513 | ||
1514 | /* pop %rbp */ | |
1515 | cfa->base = CFI_SP; | |
1516 | } | |
1517 | ||
bf4d1a83 JP |
1518 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1519 | op->dest.type == OP_DEST_REG && | |
1520 | op->dest.reg == state->drap_reg && | |
1521 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1522 | |
bf4d1a83 JP |
1523 | /* drap: pop %drap */ |
1524 | cfa->base = state->drap_reg; | |
1525 | cfa->offset = 0; | |
1526 | state->drap_offset = -1; | |
baa41469 | 1527 | |
bf4d1a83 | 1528 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1529 | |
bf4d1a83 | 1530 | /* pop %reg */ |
baa41469 JP |
1531 | restore_reg(state, op->dest.reg); |
1532 | } | |
1533 | ||
1534 | state->stack_size -= 8; | |
1535 | if (cfa->base == CFI_SP) | |
1536 | cfa->offset -= 8; | |
1537 | ||
1538 | break; | |
1539 | ||
1540 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1541 | if (state->drap && op->src.reg == CFI_BP && |
1542 | op->src.offset == state->drap_offset) { | |
1543 | ||
1544 | /* drap: mov disp(%rbp), %drap */ | |
1545 | cfa->base = state->drap_reg; | |
1546 | cfa->offset = 0; | |
1547 | state->drap_offset = -1; | |
1548 | } | |
1549 | ||
baa41469 JP |
1550 | if (state->drap && op->src.reg == CFI_BP && |
1551 | op->src.offset == regs[op->dest.reg].offset) { | |
1552 | ||
1553 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1554 | restore_reg(state, op->dest.reg); |
1555 | ||
1556 | } else if (op->src.reg == cfa->base && | |
1557 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1558 | ||
1559 | /* mov disp(%rbp), %reg */ | |
1560 | /* mov disp(%rsp), %reg */ | |
1561 | restore_reg(state, op->dest.reg); | |
1562 | } | |
1563 | ||
1564 | break; | |
1565 | ||
1566 | default: | |
1567 | WARN_FUNC("unknown stack-related instruction", | |
1568 | insn->sec, insn->offset); | |
1569 | return -1; | |
1570 | } | |
1571 | ||
1572 | break; | |
1573 | ||
1574 | case OP_DEST_PUSH: | |
1575 | state->stack_size += 8; | |
1576 | if (cfa->base == CFI_SP) | |
1577 | cfa->offset += 8; | |
1578 | ||
1579 | if (op->src.type != OP_SRC_REG) | |
1580 | break; | |
1581 | ||
1582 | if (state->drap) { | |
1583 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1584 | ||
1585 | /* drap: push %drap */ | |
1586 | cfa->base = CFI_BP_INDIRECT; | |
1587 | cfa->offset = -state->stack_size; | |
1588 | ||
bf4d1a83 JP |
1589 | /* save drap so we know when to restore it */ |
1590 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1591 | |
1592 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1593 | ||
1594 | /* drap: push %rbp */ | |
1595 | state->stack_size = 0; | |
1596 | ||
1597 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1598 | ||
1599 | /* drap: push %reg */ | |
1600 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1601 | } | |
1602 | ||
1603 | } else { | |
1604 | ||
1605 | /* push %reg */ | |
1606 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1607 | } | |
1608 | ||
1609 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1610 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1611 | cfa->base != CFI_BP) |
1612 | state->bp_scratch = true; | |
1613 | break; | |
1614 | ||
1615 | case OP_DEST_REG_INDIRECT: | |
1616 | ||
1617 | if (state->drap) { | |
1618 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1619 | ||
1620 | /* drap: mov %drap, disp(%rbp) */ | |
1621 | cfa->base = CFI_BP_INDIRECT; | |
1622 | cfa->offset = op->dest.offset; | |
1623 | ||
bf4d1a83 JP |
1624 | /* save drap offset so we know when to restore it */ |
1625 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1626 | } |
1627 | ||
1628 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1629 | ||
1630 | /* drap: mov reg, disp(%rbp) */ | |
1631 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1632 | } | |
1633 | ||
1634 | } else if (op->dest.reg == cfa->base) { | |
1635 | ||
1636 | /* mov reg, disp(%rbp) */ | |
1637 | /* mov reg, disp(%rsp) */ | |
1638 | save_reg(state, op->src.reg, CFI_CFA, | |
1639 | op->dest.offset - state->cfa.offset); | |
1640 | } | |
1641 | ||
1642 | break; | |
1643 | ||
1644 | case OP_DEST_LEAVE: | |
1645 | if ((!state->drap && cfa->base != CFI_BP) || | |
1646 | (state->drap && cfa->base != state->drap_reg)) { | |
1647 | WARN_FUNC("leave instruction with modified stack frame", | |
1648 | insn->sec, insn->offset); | |
1649 | return -1; | |
1650 | } | |
1651 | ||
1652 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1653 | ||
1654 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1655 | restore_reg(state, CFI_BP); | |
1656 | ||
1657 | if (!state->drap) { | |
1658 | cfa->base = CFI_SP; | |
1659 | cfa->offset -= 8; | |
1660 | } | |
1661 | ||
1662 | break; | |
1663 | ||
1664 | case OP_DEST_MEM: | |
1665 | if (op->src.type != OP_SRC_POP) { | |
1666 | WARN_FUNC("unknown stack-related memory operation", | |
1667 | insn->sec, insn->offset); | |
1668 | return -1; | |
1669 | } | |
1670 | ||
1671 | /* pop mem */ | |
1672 | state->stack_size -= 8; | |
1673 | if (cfa->base == CFI_SP) | |
1674 | cfa->offset -= 8; | |
1675 | ||
1676 | break; | |
1677 | ||
1678 | default: | |
1679 | WARN_FUNC("unknown stack-related instruction", | |
1680 | insn->sec, insn->offset); | |
1681 | return -1; | |
1682 | } | |
1683 | ||
1684 | return 0; | |
1685 | } | |
1686 | ||
1687 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1688 | { | |
1689 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1690 | int i; | |
1691 | ||
1692 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1693 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1694 | insn->sec, insn->offset, | |
1695 | state1->cfa.base, state1->cfa.offset, | |
1696 | state2->cfa.base, state2->cfa.offset); | |
1697 | ||
1698 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1699 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1700 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1701 | sizeof(struct cfi_reg))) | |
1702 | continue; | |
1703 | ||
1704 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1705 | insn->sec, insn->offset, | |
1706 | i, state1->regs[i].base, state1->regs[i].offset, | |
1707 | i, state2->regs[i].base, state2->regs[i].offset); | |
1708 | break; | |
1709 | } | |
1710 | ||
627fce14 JP |
1711 | } else if (state1->type != state2->type) { |
1712 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1713 | insn->sec, insn->offset, state1->type, state2->type); | |
1714 | ||
baa41469 | 1715 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1716 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1717 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1718 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1719 | insn->sec, insn->offset, |
bf4d1a83 JP |
1720 | state1->drap, state1->drap_reg, state1->drap_offset, |
1721 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1722 | |
1723 | } else | |
1724 | return true; | |
1725 | ||
1726 | return false; | |
dcc914f4 JP |
1727 | } |
1728 | ||
1729 | /* | |
1730 | * Follow the branch starting at the given instruction, and recursively follow | |
1731 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
1732 | * each instruction and validate all the rules described in | |
1733 | * tools/objtool/Documentation/stack-validation.txt. | |
1734 | */ | |
baa41469 JP |
1735 | static int validate_branch(struct objtool_file *file, struct instruction *first, |
1736 | struct insn_state state) | |
dcc914f4 JP |
1737 | { |
1738 | struct alternative *alt; | |
39358a03 | 1739 | struct instruction *insn, *next_insn; |
dcc914f4 JP |
1740 | struct section *sec; |
1741 | struct symbol *func = NULL; | |
dcc914f4 JP |
1742 | int ret; |
1743 | ||
1744 | insn = first; | |
1745 | sec = insn->sec; | |
dcc914f4 JP |
1746 | |
1747 | if (insn->alt_group && list_empty(&insn->alts)) { | |
1748 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
1749 | sec, insn->offset); | |
12b25729 | 1750 | return 1; |
dcc914f4 JP |
1751 | } |
1752 | ||
1753 | while (1) { | |
39358a03 JP |
1754 | next_insn = next_insn_same_sec(file, insn); |
1755 | ||
ee97638b JP |
1756 | |
1757 | if (file->c_file && func && insn->func && func != insn->func) { | |
1758 | WARN("%s() falls through to next function %s()", | |
1759 | func->name, insn->func->name); | |
1760 | return 1; | |
dcc914f4 JP |
1761 | } |
1762 | ||
ee97638b JP |
1763 | if (insn->func) |
1764 | func = insn->func; | |
baa41469 | 1765 | |
4855022a JP |
1766 | if (func && insn->ignore) { |
1767 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
1768 | sec, insn->offset); | |
12b25729 | 1769 | return 1; |
4855022a JP |
1770 | } |
1771 | ||
dcc914f4 | 1772 | if (insn->visited) { |
39358a03 | 1773 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 1774 | return 1; |
dcc914f4 JP |
1775 | |
1776 | return 0; | |
1777 | } | |
1778 | ||
39358a03 JP |
1779 | if (insn->hint) { |
1780 | if (insn->restore) { | |
1781 | struct instruction *save_insn, *i; | |
1782 | ||
1783 | i = insn; | |
1784 | save_insn = NULL; | |
1785 | func_for_each_insn_continue_reverse(file, func, i) { | |
1786 | if (i->save) { | |
1787 | save_insn = i; | |
1788 | break; | |
1789 | } | |
1790 | } | |
1791 | ||
1792 | if (!save_insn) { | |
1793 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
1794 | sec, insn->offset); | |
1795 | return 1; | |
1796 | } | |
1797 | ||
1798 | if (!save_insn->visited) { | |
1799 | /* | |
1800 | * Oops, no state to copy yet. | |
1801 | * Hopefully we can reach this | |
1802 | * instruction from another branch | |
1803 | * after the save insn has been | |
1804 | * visited. | |
1805 | */ | |
1806 | if (insn == first) | |
1807 | return 0; | |
1808 | ||
1809 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
1810 | sec, insn->offset); | |
1811 | return 1; | |
1812 | } | |
1813 | ||
1814 | insn->state = save_insn->state; | |
1815 | } | |
1816 | ||
1817 | state = insn->state; | |
1818 | ||
1819 | } else | |
1820 | insn->state = state; | |
dcc914f4 | 1821 | |
baa41469 JP |
1822 | insn->visited = true; |
1823 | ||
a845c7cf JP |
1824 | if (!insn->ignore_alts) { |
1825 | list_for_each_entry(alt, &insn->alts, list) { | |
1826 | ret = validate_branch(file, alt->insn, state); | |
1827 | if (ret) | |
1828 | return 1; | |
1829 | } | |
dcc914f4 JP |
1830 | } |
1831 | ||
1832 | switch (insn->type) { | |
1833 | ||
dcc914f4 | 1834 | case INSN_RETURN: |
baa41469 JP |
1835 | if (func && has_modified_stack_frame(&state)) { |
1836 | WARN_FUNC("return with modified stack frame", | |
dcc914f4 JP |
1837 | sec, insn->offset); |
1838 | return 1; | |
1839 | } | |
baa41469 JP |
1840 | |
1841 | if (state.bp_scratch) { | |
1842 | WARN("%s uses BP as a scratch register", | |
1843 | insn->func->name); | |
1844 | return 1; | |
1845 | } | |
1846 | ||
dcc914f4 JP |
1847 | return 0; |
1848 | ||
1849 | case INSN_CALL: | |
baa41469 | 1850 | if (is_fentry_call(insn)) |
dcc914f4 | 1851 | break; |
dcc914f4 JP |
1852 | |
1853 | ret = dead_end_function(file, insn->call_dest); | |
1854 | if (ret == 1) | |
1855 | return 0; | |
1856 | if (ret == -1) | |
1857 | return 1; | |
1858 | ||
1859 | /* fallthrough */ | |
1860 | case INSN_CALL_DYNAMIC: | |
867ac9d7 | 1861 | if (!no_fp && func && !has_valid_stack_frame(&state)) { |
dcc914f4 JP |
1862 | WARN_FUNC("call without frame pointer save/setup", |
1863 | sec, insn->offset); | |
1864 | return 1; | |
1865 | } | |
1866 | break; | |
1867 | ||
1868 | case INSN_JUMP_CONDITIONAL: | |
1869 | case INSN_JUMP_UNCONDITIONAL: | |
4855022a JP |
1870 | if (insn->jump_dest && |
1871 | (!func || !insn->jump_dest->func || | |
1872 | func == insn->jump_dest->func)) { | |
dcc914f4 JP |
1873 | ret = validate_branch(file, insn->jump_dest, |
1874 | state); | |
1875 | if (ret) | |
1876 | return 1; | |
4855022a | 1877 | |
baa41469 JP |
1878 | } else if (func && has_modified_stack_frame(&state)) { |
1879 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1880 | sec, insn->offset); |
1881 | return 1; | |
4855022a | 1882 | } |
dcc914f4 JP |
1883 | |
1884 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
1885 | return 0; | |
1886 | ||
1887 | break; | |
1888 | ||
1889 | case INSN_JUMP_DYNAMIC: | |
baa41469 JP |
1890 | if (func && list_empty(&insn->alts) && |
1891 | has_modified_stack_frame(&state)) { | |
1892 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1893 | sec, insn->offset); |
1894 | return 1; | |
1895 | } | |
1896 | ||
1897 | return 0; | |
1898 | ||
39358a03 JP |
1899 | case INSN_CONTEXT_SWITCH: |
1900 | if (func && (!next_insn || !next_insn->hint)) { | |
1901 | WARN_FUNC("unsupported instruction in callable function", | |
1902 | sec, insn->offset); | |
1903 | return 1; | |
1904 | } | |
1905 | return 0; | |
1906 | ||
baa41469 JP |
1907 | case INSN_STACK: |
1908 | if (update_insn_state(insn, &state)) | |
12b25729 | 1909 | return 1; |
baa41469 JP |
1910 | |
1911 | break; | |
1912 | ||
dcc914f4 JP |
1913 | default: |
1914 | break; | |
1915 | } | |
1916 | ||
1917 | if (insn->dead_end) | |
1918 | return 0; | |
1919 | ||
00d96180 JP |
1920 | if (!next_insn) { |
1921 | if (state.cfa.base == CFI_UNDEFINED) | |
1922 | return 0; | |
dcc914f4 JP |
1923 | WARN("%s: unexpected end of section", sec->name); |
1924 | return 1; | |
1925 | } | |
00d96180 JP |
1926 | |
1927 | insn = next_insn; | |
dcc914f4 JP |
1928 | } |
1929 | ||
1930 | return 0; | |
1931 | } | |
1932 | ||
39358a03 JP |
1933 | static int validate_unwind_hints(struct objtool_file *file) |
1934 | { | |
1935 | struct instruction *insn; | |
1936 | int ret, warnings = 0; | |
1937 | struct insn_state state; | |
1938 | ||
1939 | if (!file->hints) | |
1940 | return 0; | |
1941 | ||
1942 | clear_insn_state(&state); | |
1943 | ||
1944 | for_each_insn(file, insn) { | |
1945 | if (insn->hint && !insn->visited) { | |
1946 | ret = validate_branch(file, insn, state); | |
1947 | warnings += ret; | |
1948 | } | |
1949 | } | |
1950 | ||
1951 | return warnings; | |
1952 | } | |
1953 | ||
b5bc2231 PZ |
1954 | static int validate_retpoline(struct objtool_file *file) |
1955 | { | |
1956 | struct instruction *insn; | |
1957 | int warnings = 0; | |
1958 | ||
1959 | for_each_insn(file, insn) { | |
1960 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1961 | insn->type != INSN_CALL_DYNAMIC) | |
1962 | continue; | |
1963 | ||
1964 | if (insn->retpoline_safe) | |
1965 | continue; | |
1966 | ||
ca41b97e PZ |
1967 | /* |
1968 | * .init.text code is ran before userspace and thus doesn't | |
1969 | * strictly need retpolines, except for modules which are | |
1970 | * loaded late, they very much do need retpoline in their | |
1971 | * .init.text | |
1972 | */ | |
1973 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
1974 | continue; | |
1975 | ||
b5bc2231 PZ |
1976 | WARN_FUNC("indirect %s found in RETPOLINE build", |
1977 | insn->sec, insn->offset, | |
1978 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
1979 | ||
1980 | warnings++; | |
1981 | } | |
1982 | ||
1983 | return warnings; | |
1984 | } | |
1985 | ||
dcc914f4 JP |
1986 | static bool is_kasan_insn(struct instruction *insn) |
1987 | { | |
1988 | return (insn->type == INSN_CALL && | |
1989 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
1990 | } | |
1991 | ||
1992 | static bool is_ubsan_insn(struct instruction *insn) | |
1993 | { | |
1994 | return (insn->type == INSN_CALL && | |
1995 | !strcmp(insn->call_dest->name, | |
1996 | "__ubsan_handle_builtin_unreachable")); | |
1997 | } | |
1998 | ||
baa41469 | 1999 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
2000 | { |
2001 | int i; | |
2002 | ||
baa41469 JP |
2003 | if (insn->ignore || insn->type == INSN_NOP) |
2004 | return true; | |
2005 | ||
2006 | /* | |
2007 | * Ignore any unused exceptions. This can happen when a whitelisted | |
2008 | * function has an exception table entry. | |
0e2bb2bc JP |
2009 | * |
2010 | * Also ignore alternative replacement instructions. This can happen | |
2011 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 2012 | */ |
0e2bb2bc JP |
2013 | if (!strcmp(insn->sec->name, ".fixup") || |
2014 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
2015 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2016 | return true; |
2017 | ||
2018 | /* | |
2019 | * Check if this (or a subsequent) instruction is related to | |
2020 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2021 | * | |
2022 | * End the search at 5 instructions to avoid going into the weeds. | |
2023 | */ | |
baa41469 JP |
2024 | if (!insn->func) |
2025 | return false; | |
dcc914f4 JP |
2026 | for (i = 0; i < 5; i++) { |
2027 | ||
2028 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2029 | return true; | |
2030 | ||
fe24e271 JP |
2031 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2032 | if (insn->jump_dest && | |
2033 | insn->jump_dest->func == insn->func) { | |
2034 | insn = insn->jump_dest; | |
2035 | continue; | |
2036 | } | |
2037 | ||
2038 | break; | |
dcc914f4 JP |
2039 | } |
2040 | ||
baa41469 | 2041 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2042 | break; |
fe24e271 | 2043 | |
dcc914f4 JP |
2044 | insn = list_next_entry(insn, list); |
2045 | } | |
2046 | ||
2047 | return false; | |
2048 | } | |
2049 | ||
2050 | static int validate_functions(struct objtool_file *file) | |
2051 | { | |
2052 | struct section *sec; | |
2053 | struct symbol *func; | |
2054 | struct instruction *insn; | |
baa41469 | 2055 | struct insn_state state; |
dcc914f4 JP |
2056 | int ret, warnings = 0; |
2057 | ||
baa41469 JP |
2058 | clear_insn_state(&state); |
2059 | ||
2060 | state.cfa = initial_func_cfi.cfa; | |
2061 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2062 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2063 | state.stack_size = initial_func_cfi.cfa.offset; | |
2064 | ||
2065 | for_each_sec(file, sec) { | |
dcc914f4 JP |
2066 | list_for_each_entry(func, &sec->symbol_list, list) { |
2067 | if (func->type != STT_FUNC) | |
2068 | continue; | |
2069 | ||
2070 | insn = find_insn(file, sec, func->offset); | |
baa41469 | 2071 | if (!insn || insn->ignore) |
dcc914f4 JP |
2072 | continue; |
2073 | ||
baa41469 | 2074 | ret = validate_branch(file, insn, state); |
dcc914f4 JP |
2075 | warnings += ret; |
2076 | } | |
2077 | } | |
2078 | ||
dcc914f4 JP |
2079 | return warnings; |
2080 | } | |
2081 | ||
baa41469 | 2082 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2083 | { |
2084 | struct instruction *insn; | |
baa41469 JP |
2085 | |
2086 | if (file->ignore_unreachables) | |
2087 | return 0; | |
dcc914f4 JP |
2088 | |
2089 | for_each_insn(file, insn) { | |
baa41469 JP |
2090 | if (insn->visited || ignore_unreachable_insn(insn)) |
2091 | continue; | |
2092 | ||
baa41469 JP |
2093 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2094 | return 1; | |
dcc914f4 JP |
2095 | } |
2096 | ||
baa41469 | 2097 | return 0; |
dcc914f4 JP |
2098 | } |
2099 | ||
2100 | static void cleanup(struct objtool_file *file) | |
2101 | { | |
2102 | struct instruction *insn, *tmpinsn; | |
2103 | struct alternative *alt, *tmpalt; | |
2104 | ||
2105 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { | |
2106 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { | |
2107 | list_del(&alt->list); | |
2108 | free(alt); | |
2109 | } | |
2110 | list_del(&insn->list); | |
2111 | hash_del(&insn->hash); | |
2112 | free(insn); | |
2113 | } | |
2114 | elf_close(file->elf); | |
2115 | } | |
2116 | ||
43a4525f | 2117 | int check(const char *_objname, bool orc) |
dcc914f4 JP |
2118 | { |
2119 | struct objtool_file file; | |
2120 | int ret, warnings = 0; | |
2121 | ||
2122 | objname = _objname; | |
dcc914f4 | 2123 | |
627fce14 | 2124 | file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2125 | if (!file.elf) |
dcc914f4 | 2126 | return 1; |
dcc914f4 JP |
2127 | |
2128 | INIT_LIST_HEAD(&file.insn_list); | |
2129 | hash_init(file.insn_hash); | |
2130 | file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); | |
2131 | file.rodata = find_section_by_name(file.elf, ".rodata"); | |
dcc914f4 | 2132 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2133 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2134 | file.hints = false; |
dcc914f4 | 2135 | |
baa41469 JP |
2136 | arch_initial_func_cfi_state(&initial_func_cfi); |
2137 | ||
dcc914f4 JP |
2138 | ret = decode_sections(&file); |
2139 | if (ret < 0) | |
2140 | goto out; | |
2141 | warnings += ret; | |
2142 | ||
baa41469 | 2143 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2144 | goto out; |
dcc914f4 | 2145 | |
b5bc2231 PZ |
2146 | if (retpoline) { |
2147 | ret = validate_retpoline(&file); | |
2148 | if (ret < 0) | |
2149 | return ret; | |
2150 | warnings += ret; | |
2151 | } | |
2152 | ||
baa41469 | 2153 | ret = validate_functions(&file); |
dcc914f4 JP |
2154 | if (ret < 0) |
2155 | goto out; | |
2156 | warnings += ret; | |
2157 | ||
39358a03 JP |
2158 | ret = validate_unwind_hints(&file); |
2159 | if (ret < 0) | |
2160 | goto out; | |
2161 | warnings += ret; | |
2162 | ||
baa41469 JP |
2163 | if (!warnings) { |
2164 | ret = validate_reachable_instructions(&file); | |
2165 | if (ret < 0) | |
2166 | goto out; | |
2167 | warnings += ret; | |
2168 | } | |
2169 | ||
627fce14 JP |
2170 | if (orc) { |
2171 | ret = create_orc(&file); | |
2172 | if (ret < 0) | |
2173 | goto out; | |
2174 | ||
2175 | ret = create_orc_sections(&file); | |
2176 | if (ret < 0) | |
2177 | goto out; | |
2178 | ||
2179 | ret = elf_write(file.elf); | |
2180 | if (ret < 0) | |
2181 | goto out; | |
2182 | } | |
2183 | ||
dcc914f4 JP |
2184 | out: |
2185 | cleanup(&file); | |
2186 | ||
2187 | /* ignore warnings for now until we get all the code cleaned up */ | |
2188 | if (ret || warnings) | |
2189 | return 0; | |
2190 | return 0; | |
2191 | } |