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