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442f04c3 JP |
1 | /* |
2 | * Copyright (C) 2015 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 | /* | |
19 | * objtool check: | |
20 | * | |
21 | * This command analyzes every .o file and ensures the validity of its stack | |
22 | * trace metadata. It enforces a set of rules on asm code and C inline | |
23 | * assembly code so that stack traces can be reliable. | |
24 | * | |
25 | * For more information, see tools/objtool/Documentation/stack-validation.txt. | |
26 | */ | |
27 | ||
28 | #include <string.h> | |
29 | #include <subcmd/parse-options.h> | |
30 | ||
31 | #include "builtin.h" | |
32 | #include "elf.h" | |
33 | #include "special.h" | |
34 | #include "arch.h" | |
35 | #include "warn.h" | |
36 | ||
042ba73f JP |
37 | #include <linux/hashtable.h> |
38 | ||
442f04c3 JP |
39 | #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) |
40 | ||
41 | #define STATE_FP_SAVED 0x1 | |
42 | #define STATE_FP_SETUP 0x2 | |
43 | #define STATE_FENTRY 0x4 | |
44 | ||
45 | struct instruction { | |
46 | struct list_head list; | |
042ba73f | 47 | struct hlist_node hash; |
442f04c3 JP |
48 | struct section *sec; |
49 | unsigned long offset; | |
50 | unsigned int len, state; | |
51 | unsigned char type; | |
52 | unsigned long immediate; | |
53 | bool alt_group, visited; | |
54 | struct symbol *call_dest; | |
55 | struct instruction *jump_dest; | |
56 | struct list_head alts; | |
57 | }; | |
58 | ||
59 | struct alternative { | |
60 | struct list_head list; | |
61 | struct instruction *insn; | |
62 | }; | |
63 | ||
64 | struct objtool_file { | |
65 | struct elf *elf; | |
a196e171 | 66 | struct list_head insn_list; |
042ba73f JP |
67 | DECLARE_HASHTABLE(insn_hash, 16); |
68 | struct section *rodata, *whitelist; | |
442f04c3 JP |
69 | }; |
70 | ||
71 | const char *objname; | |
72 | static bool nofp; | |
73 | ||
74aec058 JP |
74 | static struct instruction *find_insn(struct objtool_file *file, |
75 | struct section *sec, unsigned long offset) | |
442f04c3 JP |
76 | { |
77 | struct instruction *insn; | |
78 | ||
042ba73f | 79 | hash_for_each_possible(file->insn_hash, insn, hash, offset) |
442f04c3 JP |
80 | if (insn->sec == sec && insn->offset == offset) |
81 | return insn; | |
82 | ||
83 | return NULL; | |
84 | } | |
85 | ||
74aec058 JP |
86 | static struct instruction *next_insn_same_sec(struct objtool_file *file, |
87 | struct instruction *insn) | |
88 | { | |
89 | struct instruction *next = list_next_entry(insn, list); | |
90 | ||
a196e171 | 91 | if (&next->list == &file->insn_list || next->sec != insn->sec) |
74aec058 JP |
92 | return NULL; |
93 | ||
94 | return next; | |
95 | } | |
96 | ||
97 | #define for_each_insn(file, insn) \ | |
a196e171 | 98 | list_for_each_entry(insn, &file->insn_list, list) |
74aec058 JP |
99 | |
100 | #define func_for_each_insn(file, func, insn) \ | |
101 | for (insn = find_insn(file, func->sec, func->offset); \ | |
a196e171 | 102 | insn && &insn->list != &file->insn_list && \ |
74aec058 JP |
103 | insn->sec == func->sec && \ |
104 | insn->offset < func->offset + func->len; \ | |
105 | insn = list_next_entry(insn, list)) | |
106 | ||
107 | #define sec_for_each_insn_from(file, insn) \ | |
108 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
109 | ||
110 | ||
442f04c3 JP |
111 | /* |
112 | * Check if the function has been manually whitelisted with the | |
113 | * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted | |
114 | * due to its use of a context switching instruction. | |
115 | */ | |
116 | static bool ignore_func(struct objtool_file *file, struct symbol *func) | |
117 | { | |
442f04c3 JP |
118 | struct rela *rela; |
119 | struct instruction *insn; | |
120 | ||
121 | /* check for STACK_FRAME_NON_STANDARD */ | |
042ba73f JP |
122 | if (file->whitelist && file->whitelist->rela) |
123 | list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) | |
442f04c3 JP |
124 | if (rela->sym->sec == func->sec && |
125 | rela->addend == func->offset) | |
126 | return true; | |
127 | ||
128 | /* check if it has a context switching instruction */ | |
74aec058 | 129 | func_for_each_insn(file, func, insn) |
442f04c3 JP |
130 | if (insn->type == INSN_CONTEXT_SWITCH) |
131 | return true; | |
442f04c3 JP |
132 | |
133 | return false; | |
134 | } | |
135 | ||
136 | /* | |
137 | * This checks to see if the given function is a "noreturn" function. | |
138 | * | |
139 | * For global functions which are outside the scope of this object file, we | |
140 | * have to keep a manual list of them. | |
141 | * | |
142 | * For local functions, we have to detect them manually by simply looking for | |
143 | * the lack of a return instruction. | |
b1e03249 JP |
144 | * |
145 | * Returns: | |
146 | * -1: error | |
147 | * 0: no dead end | |
148 | * 1: dead end | |
442f04c3 | 149 | */ |
b1e03249 JP |
150 | static int __dead_end_function(struct objtool_file *file, struct symbol *func, |
151 | int recursion) | |
442f04c3 JP |
152 | { |
153 | int i; | |
74aec058 | 154 | struct instruction *insn; |
442f04c3 JP |
155 | bool empty = true; |
156 | ||
157 | /* | |
158 | * Unfortunately these have to be hard coded because the noreturn | |
159 | * attribute isn't provided in ELF data. | |
160 | */ | |
161 | static const char * const global_noreturns[] = { | |
162 | "__stack_chk_fail", | |
163 | "panic", | |
164 | "do_exit", | |
165 | "__module_put_and_exit", | |
166 | "complete_and_exit", | |
167 | "kvm_spurious_fault", | |
168 | "__reiserfs_panic", | |
169 | "lbug_with_loc" | |
170 | }; | |
171 | ||
172 | if (func->bind == STB_WEAK) | |
b1e03249 | 173 | return 0; |
442f04c3 JP |
174 | |
175 | if (func->bind == STB_GLOBAL) | |
176 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
177 | if (!strcmp(func->name, global_noreturns[i])) | |
b1e03249 | 178 | return 1; |
442f04c3 JP |
179 | |
180 | if (!func->sec) | |
b1e03249 | 181 | return 0; |
442f04c3 | 182 | |
74aec058 | 183 | func_for_each_insn(file, func, insn) { |
442f04c3 JP |
184 | empty = false; |
185 | ||
186 | if (insn->type == INSN_RETURN) | |
b1e03249 | 187 | return 0; |
81bfafca JP |
188 | } |
189 | ||
190 | if (empty) | |
b1e03249 | 191 | return 0; |
81bfafca JP |
192 | |
193 | /* | |
194 | * A function can have a sibling call instead of a return. In that | |
195 | * case, the function's dead-end status depends on whether the target | |
196 | * of the sibling call returns. | |
197 | */ | |
74aec058 | 198 | func_for_each_insn(file, func, insn) { |
81bfafca JP |
199 | if (insn->sec != func->sec || |
200 | insn->offset >= func->offset + func->len) | |
201 | break; | |
442f04c3 JP |
202 | |
203 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { | |
204 | struct instruction *dest = insn->jump_dest; | |
205 | struct symbol *dest_func; | |
206 | ||
207 | if (!dest) | |
208 | /* sibling call to another file */ | |
b1e03249 | 209 | return 0; |
442f04c3 JP |
210 | |
211 | if (dest->sec != func->sec || | |
212 | dest->offset < func->offset || | |
213 | dest->offset >= func->offset + func->len) { | |
214 | /* local sibling call */ | |
215 | dest_func = find_symbol_by_offset(dest->sec, | |
216 | dest->offset); | |
217 | if (!dest_func) | |
218 | continue; | |
219 | ||
b1e03249 JP |
220 | if (recursion == 5) { |
221 | WARN_FUNC("infinite recursion (objtool bug!)", | |
222 | dest->sec, dest->offset); | |
223 | return -1; | |
224 | } | |
225 | ||
226 | return __dead_end_function(file, dest_func, | |
227 | recursion + 1); | |
442f04c3 JP |
228 | } |
229 | } | |
230 | ||
231 | if (insn->type == INSN_JUMP_DYNAMIC) | |
232 | /* sibling call */ | |
b1e03249 | 233 | return 0; |
442f04c3 JP |
234 | } |
235 | ||
b1e03249 JP |
236 | return 1; |
237 | } | |
238 | ||
239 | static int dead_end_function(struct objtool_file *file, struct symbol *func) | |
240 | { | |
241 | return __dead_end_function(file, func, 0); | |
442f04c3 JP |
242 | } |
243 | ||
244 | /* | |
245 | * Call the arch-specific instruction decoder for all the instructions and add | |
a196e171 | 246 | * them to the global instruction list. |
442f04c3 JP |
247 | */ |
248 | static int decode_instructions(struct objtool_file *file) | |
249 | { | |
250 | struct section *sec; | |
251 | unsigned long offset; | |
252 | struct instruction *insn; | |
253 | int ret; | |
254 | ||
442f04c3 JP |
255 | list_for_each_entry(sec, &file->elf->sections, list) { |
256 | ||
257 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
258 | continue; | |
259 | ||
260 | for (offset = 0; offset < sec->len; offset += insn->len) { | |
261 | insn = malloc(sizeof(*insn)); | |
262 | memset(insn, 0, sizeof(*insn)); | |
263 | ||
264 | INIT_LIST_HEAD(&insn->alts); | |
265 | insn->sec = sec; | |
266 | insn->offset = offset; | |
267 | ||
268 | ret = arch_decode_instruction(file->elf, sec, offset, | |
269 | sec->len - offset, | |
270 | &insn->len, &insn->type, | |
271 | &insn->immediate); | |
272 | if (ret) | |
273 | return ret; | |
274 | ||
275 | if (!insn->type || insn->type > INSN_LAST) { | |
276 | WARN_FUNC("invalid instruction type %d", | |
277 | insn->sec, insn->offset, insn->type); | |
278 | return -1; | |
279 | } | |
280 | ||
042ba73f | 281 | hash_add(file->insn_hash, &insn->hash, insn->offset); |
a196e171 | 282 | list_add_tail(&insn->list, &file->insn_list); |
442f04c3 JP |
283 | } |
284 | } | |
285 | ||
286 | return 0; | |
287 | } | |
288 | ||
289 | /* | |
290 | * Warnings shouldn't be reported for ignored functions. | |
291 | */ | |
a196e171 | 292 | static void add_ignores(struct objtool_file *file) |
442f04c3 JP |
293 | { |
294 | struct instruction *insn; | |
295 | struct section *sec; | |
296 | struct symbol *func; | |
297 | ||
298 | list_for_each_entry(sec, &file->elf->sections, list) { | |
a196e171 | 299 | list_for_each_entry(func, &sec->symbol_list, list) { |
442f04c3 JP |
300 | if (func->type != STT_FUNC) |
301 | continue; | |
302 | ||
303 | if (!ignore_func(file, func)) | |
304 | continue; | |
305 | ||
74aec058 | 306 | func_for_each_insn(file, func, insn) |
442f04c3 | 307 | insn->visited = true; |
442f04c3 JP |
308 | } |
309 | } | |
310 | } | |
311 | ||
312 | /* | |
313 | * Find the destination instructions for all jumps. | |
314 | */ | |
a196e171 | 315 | static int add_jump_destinations(struct objtool_file *file) |
442f04c3 JP |
316 | { |
317 | struct instruction *insn; | |
318 | struct rela *rela; | |
319 | struct section *dest_sec; | |
320 | unsigned long dest_off; | |
321 | ||
74aec058 | 322 | for_each_insn(file, insn) { |
442f04c3 JP |
323 | if (insn->type != INSN_JUMP_CONDITIONAL && |
324 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
325 | continue; | |
326 | ||
327 | /* skip ignores */ | |
328 | if (insn->visited) | |
329 | continue; | |
330 | ||
331 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
332 | insn->len); | |
333 | if (!rela) { | |
334 | dest_sec = insn->sec; | |
335 | dest_off = insn->offset + insn->len + insn->immediate; | |
336 | } else if (rela->sym->type == STT_SECTION) { | |
337 | dest_sec = rela->sym->sec; | |
338 | dest_off = rela->addend + 4; | |
339 | } else if (rela->sym->sec->idx) { | |
340 | dest_sec = rela->sym->sec; | |
341 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
342 | } else { | |
343 | /* sibling call */ | |
344 | insn->jump_dest = 0; | |
345 | continue; | |
346 | } | |
347 | ||
74aec058 | 348 | insn->jump_dest = find_insn(file, dest_sec, dest_off); |
442f04c3 JP |
349 | if (!insn->jump_dest) { |
350 | ||
351 | /* | |
352 | * This is a special case where an alt instruction | |
353 | * jumps past the end of the section. These are | |
354 | * handled later in handle_group_alt(). | |
355 | */ | |
356 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
357 | continue; | |
358 | ||
359 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
360 | insn->sec, insn->offset, dest_sec->name, | |
361 | dest_off); | |
362 | return -1; | |
363 | } | |
364 | } | |
365 | ||
366 | return 0; | |
367 | } | |
368 | ||
369 | /* | |
370 | * Find the destination instructions for all calls. | |
371 | */ | |
a196e171 | 372 | static int add_call_destinations(struct objtool_file *file) |
442f04c3 JP |
373 | { |
374 | struct instruction *insn; | |
375 | unsigned long dest_off; | |
376 | struct rela *rela; | |
377 | ||
74aec058 | 378 | for_each_insn(file, insn) { |
442f04c3 JP |
379 | if (insn->type != INSN_CALL) |
380 | continue; | |
381 | ||
382 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
383 | insn->len); | |
384 | if (!rela) { | |
385 | dest_off = insn->offset + insn->len + insn->immediate; | |
386 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
387 | dest_off); | |
388 | if (!insn->call_dest) { | |
389 | WARN_FUNC("can't find call dest symbol at offset 0x%lx", | |
390 | insn->sec, insn->offset, dest_off); | |
391 | return -1; | |
392 | } | |
393 | } else if (rela->sym->type == STT_SECTION) { | |
394 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
395 | rela->addend+4); | |
396 | if (!insn->call_dest || | |
397 | insn->call_dest->type != STT_FUNC) { | |
398 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
399 | insn->sec, insn->offset, | |
400 | rela->sym->sec->name, | |
401 | rela->addend + 4); | |
402 | return -1; | |
403 | } | |
404 | } else | |
405 | insn->call_dest = rela->sym; | |
406 | } | |
407 | ||
408 | return 0; | |
409 | } | |
410 | ||
411 | /* | |
412 | * The .alternatives section requires some extra special care, over and above | |
413 | * what other special sections require: | |
414 | * | |
415 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
416 | * instruction at the end so that validate_branch() skips all the original | |
417 | * replaced instructions when validating the new instruction path. | |
418 | * | |
419 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
420 | * that case the old instructions are replaced with noops. We simulate that | |
421 | * by creating a fake jump as the only new instruction. | |
422 | * | |
423 | * 3. In some cases, the alternative section includes an instruction which | |
424 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
425 | * jumps' destinations to point back to .text rather than the end of the | |
426 | * entry in .altinstr_replacement. | |
427 | * | |
428 | * 4. It has been requested that we don't validate the !POPCNT feature path | |
429 | * which is a "very very small percentage of machines". | |
430 | */ | |
431 | static int handle_group_alt(struct objtool_file *file, | |
432 | struct special_alt *special_alt, | |
433 | struct instruction *orig_insn, | |
434 | struct instruction **new_insn) | |
435 | { | |
436 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump; | |
437 | unsigned long dest_off; | |
438 | ||
439 | last_orig_insn = NULL; | |
440 | insn = orig_insn; | |
74aec058 JP |
441 | sec_for_each_insn_from(file, insn) { |
442 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
442f04c3 JP |
443 | break; |
444 | ||
445 | if (special_alt->skip_orig) | |
446 | insn->type = INSN_NOP; | |
447 | ||
448 | insn->alt_group = true; | |
449 | last_orig_insn = insn; | |
450 | } | |
451 | ||
74aec058 | 452 | if (!next_insn_same_sec(file, last_orig_insn)) { |
442f04c3 JP |
453 | WARN("%s: don't know how to handle alternatives at end of section", |
454 | special_alt->orig_sec->name); | |
455 | return -1; | |
456 | } | |
457 | ||
458 | fake_jump = malloc(sizeof(*fake_jump)); | |
459 | if (!fake_jump) { | |
460 | WARN("malloc failed"); | |
461 | return -1; | |
462 | } | |
463 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
464 | INIT_LIST_HEAD(&fake_jump->alts); | |
465 | fake_jump->sec = special_alt->new_sec; | |
466 | fake_jump->offset = -1; | |
467 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; | |
468 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
469 | ||
470 | if (!special_alt->new_len) { | |
471 | *new_insn = fake_jump; | |
472 | return 0; | |
473 | } | |
474 | ||
475 | last_new_insn = NULL; | |
476 | insn = *new_insn; | |
74aec058 JP |
477 | sec_for_each_insn_from(file, insn) { |
478 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
442f04c3 JP |
479 | break; |
480 | ||
481 | last_new_insn = insn; | |
482 | ||
483 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
484 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
485 | continue; | |
486 | ||
487 | if (!insn->immediate) | |
488 | continue; | |
489 | ||
490 | dest_off = insn->offset + insn->len + insn->immediate; | |
491 | if (dest_off == special_alt->new_off + special_alt->new_len) | |
492 | insn->jump_dest = fake_jump; | |
493 | ||
494 | if (!insn->jump_dest) { | |
495 | WARN_FUNC("can't find alternative jump destination", | |
496 | insn->sec, insn->offset); | |
497 | return -1; | |
498 | } | |
499 | } | |
500 | ||
501 | if (!last_new_insn) { | |
502 | WARN_FUNC("can't find last new alternative instruction", | |
503 | special_alt->new_sec, special_alt->new_off); | |
504 | return -1; | |
505 | } | |
506 | ||
507 | list_add(&fake_jump->list, &last_new_insn->list); | |
508 | ||
509 | return 0; | |
510 | } | |
511 | ||
512 | /* | |
513 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
514 | * If the original instruction is a jump, make the alt entry an effective nop | |
515 | * by just skipping the original instruction. | |
516 | */ | |
517 | static int handle_jump_alt(struct objtool_file *file, | |
518 | struct special_alt *special_alt, | |
519 | struct instruction *orig_insn, | |
520 | struct instruction **new_insn) | |
521 | { | |
522 | if (orig_insn->type == INSN_NOP) | |
523 | return 0; | |
524 | ||
525 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
526 | WARN_FUNC("unsupported instruction at jump label", | |
527 | orig_insn->sec, orig_insn->offset); | |
528 | return -1; | |
529 | } | |
530 | ||
531 | *new_insn = list_next_entry(orig_insn, list); | |
532 | return 0; | |
533 | } | |
534 | ||
535 | /* | |
536 | * Read all the special sections which have alternate instructions which can be | |
537 | * patched in or redirected to at runtime. Each instruction having alternate | |
538 | * instruction(s) has them added to its insn->alts list, which will be | |
539 | * traversed in validate_branch(). | |
540 | */ | |
a196e171 | 541 | static int add_special_section_alts(struct objtool_file *file) |
442f04c3 JP |
542 | { |
543 | struct list_head special_alts; | |
544 | struct instruction *orig_insn, *new_insn; | |
545 | struct special_alt *special_alt, *tmp; | |
546 | struct alternative *alt; | |
547 | int ret; | |
548 | ||
549 | ret = special_get_alts(file->elf, &special_alts); | |
550 | if (ret) | |
551 | return ret; | |
552 | ||
553 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
554 | alt = malloc(sizeof(*alt)); | |
555 | if (!alt) { | |
556 | WARN("malloc failed"); | |
557 | ret = -1; | |
558 | goto out; | |
559 | } | |
560 | ||
74aec058 JP |
561 | orig_insn = find_insn(file, special_alt->orig_sec, |
562 | special_alt->orig_off); | |
442f04c3 JP |
563 | if (!orig_insn) { |
564 | WARN_FUNC("special: can't find orig instruction", | |
565 | special_alt->orig_sec, special_alt->orig_off); | |
566 | ret = -1; | |
567 | goto out; | |
568 | } | |
569 | ||
570 | new_insn = NULL; | |
571 | if (!special_alt->group || special_alt->new_len) { | |
74aec058 JP |
572 | new_insn = find_insn(file, special_alt->new_sec, |
573 | special_alt->new_off); | |
442f04c3 JP |
574 | if (!new_insn) { |
575 | WARN_FUNC("special: can't find new instruction", | |
576 | special_alt->new_sec, | |
577 | special_alt->new_off); | |
578 | ret = -1; | |
579 | goto out; | |
580 | } | |
581 | } | |
582 | ||
583 | if (special_alt->group) { | |
584 | ret = handle_group_alt(file, special_alt, orig_insn, | |
585 | &new_insn); | |
586 | if (ret) | |
587 | goto out; | |
588 | } else if (special_alt->jump_or_nop) { | |
589 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
590 | &new_insn); | |
591 | if (ret) | |
592 | goto out; | |
593 | } | |
594 | ||
595 | alt->insn = new_insn; | |
596 | list_add_tail(&alt->list, &orig_insn->alts); | |
597 | ||
598 | list_del(&special_alt->list); | |
599 | free(special_alt); | |
600 | } | |
601 | ||
602 | out: | |
603 | return ret; | |
604 | } | |
605 | ||
8133fbb4 JP |
606 | static int add_switch_table(struct objtool_file *file, struct symbol *func, |
607 | struct instruction *insn, struct rela *table, | |
608 | struct rela *next_table) | |
442f04c3 | 609 | { |
8133fbb4 JP |
610 | struct rela *rela = table; |
611 | struct instruction *alt_insn; | |
442f04c3 JP |
612 | struct alternative *alt; |
613 | ||
8133fbb4 JP |
614 | list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { |
615 | if (rela == next_table) | |
616 | break; | |
617 | ||
618 | if (rela->sym->sec != insn->sec || | |
619 | rela->addend <= func->offset || | |
620 | rela->addend >= func->offset + func->len) | |
621 | break; | |
622 | ||
623 | alt_insn = find_insn(file, insn->sec, rela->addend); | |
624 | if (!alt_insn) { | |
625 | WARN("%s: can't find instruction at %s+0x%x", | |
626 | file->rodata->rela->name, insn->sec->name, | |
627 | rela->addend); | |
628 | return -1; | |
629 | } | |
630 | ||
631 | alt = malloc(sizeof(*alt)); | |
632 | if (!alt) { | |
633 | WARN("malloc failed"); | |
634 | return -1; | |
635 | } | |
636 | ||
637 | alt->insn = alt_insn; | |
638 | list_add_tail(&alt->list, &insn->alts); | |
639 | } | |
640 | ||
641 | return 0; | |
642 | } | |
643 | ||
644 | static int add_func_switch_tables(struct objtool_file *file, | |
645 | struct symbol *func) | |
646 | { | |
647 | struct instruction *insn, *prev_jump; | |
648 | struct rela *text_rela, *rodata_rela, *prev_rela; | |
649 | int ret; | |
650 | ||
651 | prev_jump = NULL; | |
652 | ||
653 | func_for_each_insn(file, func, insn) { | |
442f04c3 JP |
654 | if (insn->type != INSN_JUMP_DYNAMIC) |
655 | continue; | |
656 | ||
a196e171 JP |
657 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, |
658 | insn->len); | |
8133fbb4 | 659 | if (!text_rela || text_rela->sym != file->rodata->sym) |
442f04c3 JP |
660 | continue; |
661 | ||
662 | /* common case: jmpq *[addr](,%rax,8) */ | |
8133fbb4 JP |
663 | rodata_rela = find_rela_by_dest(file->rodata, |
664 | text_rela->addend); | |
665 | ||
666 | /* | |
667 | * TODO: Document where this is needed, or get rid of it. | |
668 | * | |
669 | * rare case: jmpq *[addr](%rip) | |
670 | */ | |
a196e171 | 671 | if (!rodata_rela) |
8133fbb4 | 672 | rodata_rela = find_rela_by_dest(file->rodata, |
a196e171 | 673 | text_rela->addend + 4); |
8133fbb4 | 674 | |
a196e171 | 675 | if (!rodata_rela) |
442f04c3 JP |
676 | continue; |
677 | ||
8133fbb4 JP |
678 | /* |
679 | * We found a switch table, but we don't know yet how big it | |
680 | * is. Don't add it until we reach the end of the function or | |
681 | * the beginning of another switch table in the same function. | |
682 | */ | |
683 | if (prev_jump) { | |
684 | ret = add_switch_table(file, func, prev_jump, prev_rela, | |
685 | rodata_rela); | |
686 | if (ret) | |
687 | return ret; | |
442f04c3 JP |
688 | } |
689 | ||
8133fbb4 JP |
690 | prev_jump = insn; |
691 | prev_rela = rodata_rela; | |
692 | } | |
442f04c3 | 693 | |
8133fbb4 JP |
694 | if (prev_jump) { |
695 | ret = add_switch_table(file, func, prev_jump, prev_rela, NULL); | |
696 | if (ret) | |
697 | return ret; | |
698 | } | |
699 | ||
700 | return 0; | |
701 | } | |
442f04c3 | 702 | |
8133fbb4 JP |
703 | /* |
704 | * For some switch statements, gcc generates a jump table in the .rodata | |
705 | * section which contains a list of addresses within the function to jump to. | |
706 | * This finds these jump tables and adds them to the insn->alts lists. | |
707 | */ | |
708 | static int add_switch_table_alts(struct objtool_file *file) | |
709 | { | |
710 | struct section *sec; | |
711 | struct symbol *func; | |
712 | int ret; | |
713 | ||
714 | if (!file->rodata || !file->rodata->rela) | |
715 | return 0; | |
716 | ||
717 | list_for_each_entry(sec, &file->elf->sections, list) { | |
718 | list_for_each_entry(func, &sec->symbol_list, list) { | |
719 | if (func->type != STT_FUNC) | |
720 | continue; | |
721 | ||
722 | ret = add_func_switch_tables(file, func); | |
723 | if (ret) | |
724 | return ret; | |
442f04c3 JP |
725 | } |
726 | } | |
727 | ||
728 | return 0; | |
729 | } | |
730 | ||
731 | static int decode_sections(struct objtool_file *file) | |
732 | { | |
733 | int ret; | |
734 | ||
042ba73f | 735 | file->whitelist = find_section_by_name(file->elf, "__func_stack_frame_non_standard"); |
8133fbb4 JP |
736 | file->rodata = find_section_by_name(file->elf, ".rodata"); |
737 | ||
442f04c3 JP |
738 | ret = decode_instructions(file); |
739 | if (ret) | |
740 | return ret; | |
741 | ||
a196e171 | 742 | add_ignores(file); |
442f04c3 | 743 | |
a196e171 | 744 | ret = add_jump_destinations(file); |
442f04c3 JP |
745 | if (ret) |
746 | return ret; | |
747 | ||
a196e171 | 748 | ret = add_call_destinations(file); |
442f04c3 JP |
749 | if (ret) |
750 | return ret; | |
751 | ||
a196e171 | 752 | ret = add_special_section_alts(file); |
442f04c3 JP |
753 | if (ret) |
754 | return ret; | |
755 | ||
a196e171 | 756 | ret = add_switch_table_alts(file); |
442f04c3 JP |
757 | if (ret) |
758 | return ret; | |
759 | ||
760 | return 0; | |
761 | } | |
762 | ||
763 | static bool is_fentry_call(struct instruction *insn) | |
764 | { | |
765 | if (insn->type == INSN_CALL && | |
766 | insn->call_dest->type == STT_NOTYPE && | |
767 | !strcmp(insn->call_dest->name, "__fentry__")) | |
768 | return true; | |
769 | ||
770 | return false; | |
771 | } | |
772 | ||
773 | static bool has_modified_stack_frame(struct instruction *insn) | |
774 | { | |
775 | return (insn->state & STATE_FP_SAVED) || | |
776 | (insn->state & STATE_FP_SETUP); | |
777 | } | |
778 | ||
779 | static bool has_valid_stack_frame(struct instruction *insn) | |
780 | { | |
781 | return (insn->state & STATE_FP_SAVED) && | |
782 | (insn->state & STATE_FP_SETUP); | |
783 | } | |
784 | ||
d8d1b2cb JP |
785 | static unsigned int frame_state(unsigned long state) |
786 | { | |
787 | return (state & (STATE_FP_SAVED | STATE_FP_SETUP)); | |
788 | } | |
789 | ||
442f04c3 JP |
790 | /* |
791 | * Follow the branch starting at the given instruction, and recursively follow | |
792 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
793 | * each instruction and validate all the rules described in | |
794 | * tools/objtool/Documentation/stack-validation.txt. | |
795 | */ | |
796 | static int validate_branch(struct objtool_file *file, | |
797 | struct instruction *first, unsigned char first_state) | |
798 | { | |
799 | struct alternative *alt; | |
800 | struct instruction *insn; | |
801 | struct section *sec; | |
802 | unsigned char state; | |
803 | int ret, warnings = 0; | |
804 | ||
805 | insn = first; | |
806 | sec = insn->sec; | |
807 | state = first_state; | |
808 | ||
809 | if (insn->alt_group && list_empty(&insn->alts)) { | |
810 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
811 | sec, insn->offset); | |
812 | warnings++; | |
813 | } | |
814 | ||
815 | while (1) { | |
816 | if (insn->visited) { | |
d8d1b2cb | 817 | if (frame_state(insn->state) != frame_state(state)) { |
442f04c3 JP |
818 | WARN_FUNC("frame pointer state mismatch", |
819 | sec, insn->offset); | |
820 | warnings++; | |
821 | } | |
822 | ||
823 | return warnings; | |
824 | } | |
825 | ||
826 | /* | |
827 | * Catch a rare case where a noreturn function falls through to | |
828 | * the next function. | |
829 | */ | |
830 | if (is_fentry_call(insn) && (state & STATE_FENTRY)) | |
831 | return warnings; | |
832 | ||
833 | insn->visited = true; | |
834 | insn->state = state; | |
835 | ||
836 | list_for_each_entry(alt, &insn->alts, list) { | |
837 | ret = validate_branch(file, alt->insn, state); | |
838 | warnings += ret; | |
839 | } | |
840 | ||
841 | switch (insn->type) { | |
842 | ||
843 | case INSN_FP_SAVE: | |
844 | if (!nofp) { | |
845 | if (state & STATE_FP_SAVED) { | |
846 | WARN_FUNC("duplicate frame pointer save", | |
847 | sec, insn->offset); | |
848 | warnings++; | |
849 | } | |
850 | state |= STATE_FP_SAVED; | |
851 | } | |
852 | break; | |
853 | ||
854 | case INSN_FP_SETUP: | |
855 | if (!nofp) { | |
856 | if (state & STATE_FP_SETUP) { | |
857 | WARN_FUNC("duplicate frame pointer setup", | |
858 | sec, insn->offset); | |
859 | warnings++; | |
860 | } | |
861 | state |= STATE_FP_SETUP; | |
862 | } | |
863 | break; | |
864 | ||
865 | case INSN_FP_RESTORE: | |
866 | if (!nofp) { | |
867 | if (has_valid_stack_frame(insn)) | |
868 | state &= ~STATE_FP_SETUP; | |
869 | ||
870 | state &= ~STATE_FP_SAVED; | |
871 | } | |
872 | break; | |
873 | ||
874 | case INSN_RETURN: | |
875 | if (!nofp && has_modified_stack_frame(insn)) { | |
876 | WARN_FUNC("return without frame pointer restore", | |
877 | sec, insn->offset); | |
878 | warnings++; | |
879 | } | |
880 | return warnings; | |
881 | ||
882 | case INSN_CALL: | |
883 | if (is_fentry_call(insn)) { | |
884 | state |= STATE_FENTRY; | |
885 | break; | |
886 | } | |
887 | ||
b1e03249 JP |
888 | ret = dead_end_function(file, insn->call_dest); |
889 | if (ret == 1) | |
442f04c3 | 890 | return warnings; |
b1e03249 JP |
891 | if (ret == -1) |
892 | warnings++; | |
442f04c3 JP |
893 | |
894 | /* fallthrough */ | |
895 | case INSN_CALL_DYNAMIC: | |
896 | if (!nofp && !has_valid_stack_frame(insn)) { | |
897 | WARN_FUNC("call without frame pointer save/setup", | |
898 | sec, insn->offset); | |
899 | warnings++; | |
900 | } | |
901 | break; | |
902 | ||
903 | case INSN_JUMP_CONDITIONAL: | |
904 | case INSN_JUMP_UNCONDITIONAL: | |
905 | if (insn->jump_dest) { | |
906 | ret = validate_branch(file, insn->jump_dest, | |
907 | state); | |
908 | warnings += ret; | |
909 | } else if (has_modified_stack_frame(insn)) { | |
910 | WARN_FUNC("sibling call from callable instruction with changed frame pointer", | |
911 | sec, insn->offset); | |
912 | warnings++; | |
913 | } /* else it's a sibling call */ | |
914 | ||
915 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
916 | return warnings; | |
917 | ||
918 | break; | |
919 | ||
920 | case INSN_JUMP_DYNAMIC: | |
921 | if (list_empty(&insn->alts) && | |
922 | has_modified_stack_frame(insn)) { | |
923 | WARN_FUNC("sibling call from callable instruction with changed frame pointer", | |
924 | sec, insn->offset); | |
925 | warnings++; | |
926 | } | |
927 | ||
928 | return warnings; | |
929 | ||
930 | case INSN_BUG: | |
931 | return warnings; | |
932 | ||
933 | default: | |
934 | break; | |
935 | } | |
936 | ||
74aec058 JP |
937 | insn = next_insn_same_sec(file, insn); |
938 | if (!insn) { | |
442f04c3 JP |
939 | WARN("%s: unexpected end of section", sec->name); |
940 | warnings++; | |
941 | return warnings; | |
942 | } | |
943 | } | |
944 | ||
945 | return warnings; | |
946 | } | |
947 | ||
948 | static bool is_gcov_insn(struct instruction *insn) | |
949 | { | |
950 | struct rela *rela; | |
951 | struct section *sec; | |
952 | struct symbol *sym; | |
953 | unsigned long offset; | |
954 | ||
955 | rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); | |
956 | if (!rela) | |
957 | return false; | |
958 | ||
959 | if (rela->sym->type != STT_SECTION) | |
960 | return false; | |
961 | ||
962 | sec = rela->sym->sec; | |
963 | offset = rela->addend + insn->offset + insn->len - rela->offset; | |
964 | ||
a196e171 | 965 | list_for_each_entry(sym, &sec->symbol_list, list) { |
442f04c3 JP |
966 | if (sym->type != STT_OBJECT) |
967 | continue; | |
968 | ||
969 | if (offset >= sym->offset && offset < sym->offset + sym->len) | |
970 | return (!memcmp(sym->name, "__gcov0.", 8)); | |
971 | } | |
972 | ||
973 | return false; | |
974 | } | |
975 | ||
976 | static bool is_kasan_insn(struct instruction *insn) | |
977 | { | |
978 | return (insn->type == INSN_CALL && | |
979 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
980 | } | |
981 | ||
982 | static bool is_ubsan_insn(struct instruction *insn) | |
983 | { | |
984 | return (insn->type == INSN_CALL && | |
985 | !strcmp(insn->call_dest->name, | |
986 | "__ubsan_handle_builtin_unreachable")); | |
987 | } | |
988 | ||
74aec058 JP |
989 | static bool ignore_unreachable_insn(struct symbol *func, |
990 | struct instruction *insn) | |
442f04c3 JP |
991 | { |
992 | int i; | |
993 | ||
994 | if (insn->type == INSN_NOP) | |
995 | return true; | |
996 | ||
997 | if (is_gcov_insn(insn)) | |
998 | return true; | |
999 | ||
1000 | /* | |
1001 | * Check if this (or a subsequent) instruction is related to | |
1002 | * CONFIG_UBSAN or CONFIG_KASAN. | |
1003 | * | |
1004 | * End the search at 5 instructions to avoid going into the weeds. | |
1005 | */ | |
1006 | for (i = 0; i < 5; i++) { | |
1007 | ||
1008 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
1009 | return true; | |
1010 | ||
1011 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) { | |
1012 | insn = insn->jump_dest; | |
1013 | continue; | |
1014 | } | |
1015 | ||
74aec058 | 1016 | if (insn->offset + insn->len >= func->offset + func->len) |
442f04c3 JP |
1017 | break; |
1018 | insn = list_next_entry(insn, list); | |
1019 | } | |
1020 | ||
1021 | return false; | |
1022 | } | |
1023 | ||
1024 | static int validate_functions(struct objtool_file *file) | |
1025 | { | |
1026 | struct section *sec; | |
1027 | struct symbol *func; | |
1028 | struct instruction *insn; | |
442f04c3 JP |
1029 | int ret, warnings = 0; |
1030 | ||
1031 | list_for_each_entry(sec, &file->elf->sections, list) { | |
a196e171 | 1032 | list_for_each_entry(func, &sec->symbol_list, list) { |
442f04c3 JP |
1033 | if (func->type != STT_FUNC) |
1034 | continue; | |
1035 | ||
74aec058 | 1036 | insn = find_insn(file, sec, func->offset); |
442f04c3 JP |
1037 | if (!insn) { |
1038 | WARN("%s(): can't find starting instruction", | |
1039 | func->name); | |
1040 | warnings++; | |
1041 | continue; | |
1042 | } | |
1043 | ||
1044 | ret = validate_branch(file, insn, 0); | |
1045 | warnings += ret; | |
1046 | } | |
1047 | } | |
1048 | ||
1049 | list_for_each_entry(sec, &file->elf->sections, list) { | |
a196e171 | 1050 | list_for_each_entry(func, &sec->symbol_list, list) { |
442f04c3 JP |
1051 | if (func->type != STT_FUNC) |
1052 | continue; | |
1053 | ||
74aec058 | 1054 | func_for_each_insn(file, func, insn) { |
442f04c3 JP |
1055 | if (insn->visited) |
1056 | continue; | |
1057 | ||
74aec058 | 1058 | if (!ignore_unreachable_insn(func, insn)) { |
442f04c3 JP |
1059 | WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset); |
1060 | warnings++; | |
1061 | } | |
1062 | ||
1063 | insn->visited = true; | |
1064 | } | |
1065 | } | |
1066 | } | |
1067 | ||
1068 | return warnings; | |
1069 | } | |
1070 | ||
1071 | static int validate_uncallable_instructions(struct objtool_file *file) | |
1072 | { | |
1073 | struct instruction *insn; | |
1074 | int warnings = 0; | |
1075 | ||
74aec058 | 1076 | for_each_insn(file, insn) { |
442f04c3 JP |
1077 | if (!insn->visited && insn->type == INSN_RETURN) { |
1078 | WARN_FUNC("return instruction outside of a callable function", | |
1079 | insn->sec, insn->offset); | |
1080 | warnings++; | |
1081 | } | |
1082 | } | |
1083 | ||
1084 | return warnings; | |
1085 | } | |
1086 | ||
1087 | static void cleanup(struct objtool_file *file) | |
1088 | { | |
1089 | struct instruction *insn, *tmpinsn; | |
1090 | struct alternative *alt, *tmpalt; | |
1091 | ||
a196e171 | 1092 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { |
442f04c3 JP |
1093 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { |
1094 | list_del(&alt->list); | |
1095 | free(alt); | |
1096 | } | |
1097 | list_del(&insn->list); | |
042ba73f | 1098 | hash_del(&insn->hash); |
442f04c3 JP |
1099 | free(insn); |
1100 | } | |
1101 | elf_close(file->elf); | |
1102 | } | |
1103 | ||
1104 | const char * const check_usage[] = { | |
1105 | "objtool check [<options>] file.o", | |
1106 | NULL, | |
1107 | }; | |
1108 | ||
1109 | int cmd_check(int argc, const char **argv) | |
1110 | { | |
1111 | struct objtool_file file; | |
1112 | int ret, warnings = 0; | |
1113 | ||
1114 | const struct option options[] = { | |
1115 | OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"), | |
1116 | OPT_END(), | |
1117 | }; | |
1118 | ||
1119 | argc = parse_options(argc, argv, options, check_usage, 0); | |
1120 | ||
1121 | if (argc != 1) | |
1122 | usage_with_options(check_usage, options); | |
1123 | ||
1124 | objname = argv[0]; | |
1125 | ||
1126 | file.elf = elf_open(objname); | |
1127 | if (!file.elf) { | |
1128 | fprintf(stderr, "error reading elf file %s\n", objname); | |
1129 | return 1; | |
1130 | } | |
1131 | ||
a196e171 | 1132 | INIT_LIST_HEAD(&file.insn_list); |
042ba73f | 1133 | hash_init(file.insn_hash); |
442f04c3 JP |
1134 | |
1135 | ret = decode_sections(&file); | |
1136 | if (ret < 0) | |
1137 | goto out; | |
1138 | warnings += ret; | |
1139 | ||
1140 | ret = validate_functions(&file); | |
1141 | if (ret < 0) | |
1142 | goto out; | |
1143 | warnings += ret; | |
1144 | ||
1145 | ret = validate_uncallable_instructions(&file); | |
1146 | if (ret < 0) | |
1147 | goto out; | |
1148 | warnings += ret; | |
1149 | ||
1150 | out: | |
1151 | cleanup(&file); | |
1152 | ||
1153 | /* ignore warnings for now until we get all the code cleaned up */ | |
1154 | if (ret || warnings) | |
1155 | return 0; | |
1156 | return 0; | |
1157 | } |