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1 | // SPDX-License-Identifier: GPL-2.0-or-later | |
2 | /* | |
3 | * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> | |
4 | */ | |
5 | ||
6 | #include <string.h> | |
7 | #include <stdlib.h> | |
8 | #include <inttypes.h> | |
9 | #include <sys/mman.h> | |
10 | ||
11 | #include <arch/elf.h> | |
12 | #include <objtool/builtin.h> | |
13 | #include <objtool/cfi.h> | |
14 | #include <objtool/arch.h> | |
15 | #include <objtool/check.h> | |
16 | #include <objtool/special.h> | |
17 | #include <objtool/warn.h> | |
18 | #include <objtool/endianness.h> | |
19 | ||
20 | #include <linux/objtool.h> | |
21 | #include <linux/hashtable.h> | |
22 | #include <linux/kernel.h> | |
23 | #include <linux/static_call_types.h> | |
24 | ||
25 | struct alternative { | |
26 | struct list_head list; | |
27 | struct instruction *insn; | |
28 | bool skip_orig; | |
29 | }; | |
30 | ||
31 | static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; | |
32 | ||
33 | static struct cfi_init_state initial_func_cfi; | |
34 | static struct cfi_state init_cfi; | |
35 | static struct cfi_state func_cfi; | |
36 | ||
37 | struct instruction *find_insn(struct objtool_file *file, | |
38 | struct section *sec, unsigned long offset) | |
39 | { | |
40 | struct instruction *insn; | |
41 | ||
42 | hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) { | |
43 | if (insn->sec == sec && insn->offset == offset) | |
44 | return insn; | |
45 | } | |
46 | ||
47 | return NULL; | |
48 | } | |
49 | ||
50 | static struct instruction *next_insn_same_sec(struct objtool_file *file, | |
51 | struct instruction *insn) | |
52 | { | |
53 | struct instruction *next = list_next_entry(insn, list); | |
54 | ||
55 | if (!next || &next->list == &file->insn_list || next->sec != insn->sec) | |
56 | return NULL; | |
57 | ||
58 | return next; | |
59 | } | |
60 | ||
61 | static struct instruction *next_insn_same_func(struct objtool_file *file, | |
62 | struct instruction *insn) | |
63 | { | |
64 | struct instruction *next = list_next_entry(insn, list); | |
65 | struct symbol *func = insn->func; | |
66 | ||
67 | if (!func) | |
68 | return NULL; | |
69 | ||
70 | if (&next->list != &file->insn_list && next->func == func) | |
71 | return next; | |
72 | ||
73 | /* Check if we're already in the subfunction: */ | |
74 | if (func == func->cfunc) | |
75 | return NULL; | |
76 | ||
77 | /* Move to the subfunction: */ | |
78 | return find_insn(file, func->cfunc->sec, func->cfunc->offset); | |
79 | } | |
80 | ||
81 | static struct instruction *prev_insn_same_sym(struct objtool_file *file, | |
82 | struct instruction *insn) | |
83 | { | |
84 | struct instruction *prev = list_prev_entry(insn, list); | |
85 | ||
86 | if (&prev->list != &file->insn_list && prev->func == insn->func) | |
87 | return prev; | |
88 | ||
89 | return NULL; | |
90 | } | |
91 | ||
92 | #define func_for_each_insn(file, func, insn) \ | |
93 | for (insn = find_insn(file, func->sec, func->offset); \ | |
94 | insn; \ | |
95 | insn = next_insn_same_func(file, insn)) | |
96 | ||
97 | #define sym_for_each_insn(file, sym, insn) \ | |
98 | for (insn = find_insn(file, sym->sec, sym->offset); \ | |
99 | insn && &insn->list != &file->insn_list && \ | |
100 | insn->sec == sym->sec && \ | |
101 | insn->offset < sym->offset + sym->len; \ | |
102 | insn = list_next_entry(insn, list)) | |
103 | ||
104 | #define sym_for_each_insn_continue_reverse(file, sym, insn) \ | |
105 | for (insn = list_prev_entry(insn, list); \ | |
106 | &insn->list != &file->insn_list && \ | |
107 | insn->sec == sym->sec && insn->offset >= sym->offset; \ | |
108 | insn = list_prev_entry(insn, list)) | |
109 | ||
110 | #define sec_for_each_insn_from(file, insn) \ | |
111 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
112 | ||
113 | #define sec_for_each_insn_continue(file, insn) \ | |
114 | for (insn = next_insn_same_sec(file, insn); insn; \ | |
115 | insn = next_insn_same_sec(file, insn)) | |
116 | ||
117 | static bool is_jump_table_jump(struct instruction *insn) | |
118 | { | |
119 | struct alt_group *alt_group = insn->alt_group; | |
120 | ||
121 | if (insn->jump_table) | |
122 | return true; | |
123 | ||
124 | /* Retpoline alternative for a jump table? */ | |
125 | return alt_group && alt_group->orig_group && | |
126 | alt_group->orig_group->first_insn->jump_table; | |
127 | } | |
128 | ||
129 | static bool is_sibling_call(struct instruction *insn) | |
130 | { | |
131 | /* | |
132 | * Assume only ELF functions can make sibling calls. This ensures | |
133 | * sibling call detection consistency between vmlinux.o and individual | |
134 | * objects. | |
135 | */ | |
136 | if (!insn->func) | |
137 | return false; | |
138 | ||
139 | /* An indirect jump is either a sibling call or a jump to a table. */ | |
140 | if (insn->type == INSN_JUMP_DYNAMIC) | |
141 | return !is_jump_table_jump(insn); | |
142 | ||
143 | /* add_jump_destinations() sets insn->call_dest for sibling calls. */ | |
144 | return (is_static_jump(insn) && insn->call_dest); | |
145 | } | |
146 | ||
147 | /* | |
148 | * This checks to see if the given function is a "noreturn" function. | |
149 | * | |
150 | * For global functions which are outside the scope of this object file, we | |
151 | * have to keep a manual list of them. | |
152 | * | |
153 | * For local functions, we have to detect them manually by simply looking for | |
154 | * the lack of a return instruction. | |
155 | */ | |
156 | static bool __dead_end_function(struct objtool_file *file, struct symbol *func, | |
157 | int recursion) | |
158 | { | |
159 | int i; | |
160 | struct instruction *insn; | |
161 | bool empty = true; | |
162 | ||
163 | /* | |
164 | * Unfortunately these have to be hard coded because the noreturn | |
165 | * attribute isn't provided in ELF data. | |
166 | */ | |
167 | static const char * const global_noreturns[] = { | |
168 | "__stack_chk_fail", | |
169 | "panic", | |
170 | "do_exit", | |
171 | "do_task_dead", | |
172 | "__module_put_and_exit", | |
173 | "complete_and_exit", | |
174 | "__reiserfs_panic", | |
175 | "lbug_with_loc", | |
176 | "fortify_panic", | |
177 | "usercopy_abort", | |
178 | "machine_real_restart", | |
179 | "rewind_stack_do_exit", | |
180 | "kunit_try_catch_throw", | |
181 | "xen_start_kernel", | |
182 | "cpu_bringup_and_idle", | |
183 | }; | |
184 | ||
185 | if (!func) | |
186 | return false; | |
187 | ||
188 | if (func->bind == STB_WEAK) | |
189 | return false; | |
190 | ||
191 | if (func->bind == STB_GLOBAL) | |
192 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
193 | if (!strcmp(func->name, global_noreturns[i])) | |
194 | return true; | |
195 | ||
196 | if (!func->len) | |
197 | return false; | |
198 | ||
199 | insn = find_insn(file, func->sec, func->offset); | |
200 | if (!insn->func) | |
201 | return false; | |
202 | ||
203 | func_for_each_insn(file, func, insn) { | |
204 | empty = false; | |
205 | ||
206 | if (insn->type == INSN_RETURN) | |
207 | return false; | |
208 | } | |
209 | ||
210 | if (empty) | |
211 | return false; | |
212 | ||
213 | /* | |
214 | * A function can have a sibling call instead of a return. In that | |
215 | * case, the function's dead-end status depends on whether the target | |
216 | * of the sibling call returns. | |
217 | */ | |
218 | func_for_each_insn(file, func, insn) { | |
219 | if (is_sibling_call(insn)) { | |
220 | struct instruction *dest = insn->jump_dest; | |
221 | ||
222 | if (!dest) | |
223 | /* sibling call to another file */ | |
224 | return false; | |
225 | ||
226 | /* local sibling call */ | |
227 | if (recursion == 5) { | |
228 | /* | |
229 | * Infinite recursion: two functions have | |
230 | * sibling calls to each other. This is a very | |
231 | * rare case. It means they aren't dead ends. | |
232 | */ | |
233 | return false; | |
234 | } | |
235 | ||
236 | return __dead_end_function(file, dest->func, recursion+1); | |
237 | } | |
238 | } | |
239 | ||
240 | return true; | |
241 | } | |
242 | ||
243 | static bool dead_end_function(struct objtool_file *file, struct symbol *func) | |
244 | { | |
245 | return __dead_end_function(file, func, 0); | |
246 | } | |
247 | ||
248 | static void init_cfi_state(struct cfi_state *cfi) | |
249 | { | |
250 | int i; | |
251 | ||
252 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
253 | cfi->regs[i].base = CFI_UNDEFINED; | |
254 | cfi->vals[i].base = CFI_UNDEFINED; | |
255 | } | |
256 | cfi->cfa.base = CFI_UNDEFINED; | |
257 | cfi->drap_reg = CFI_UNDEFINED; | |
258 | cfi->drap_offset = -1; | |
259 | } | |
260 | ||
261 | static void init_insn_state(struct insn_state *state, struct section *sec) | |
262 | { | |
263 | memset(state, 0, sizeof(*state)); | |
264 | init_cfi_state(&state->cfi); | |
265 | ||
266 | /* | |
267 | * We need the full vmlinux for noinstr validation, otherwise we can | |
268 | * not correctly determine insn->call_dest->sec (external symbols do | |
269 | * not have a section). | |
270 | */ | |
271 | if (vmlinux && noinstr && sec) | |
272 | state->noinstr = sec->noinstr; | |
273 | } | |
274 | ||
275 | static struct cfi_state *cfi_alloc(void) | |
276 | { | |
277 | struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1); | |
278 | if (!cfi) { | |
279 | WARN("calloc failed"); | |
280 | exit(1); | |
281 | } | |
282 | nr_cfi++; | |
283 | return cfi; | |
284 | } | |
285 | ||
286 | static int cfi_bits; | |
287 | static struct hlist_head *cfi_hash; | |
288 | ||
289 | static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2) | |
290 | { | |
291 | return memcmp((void *)cfi1 + sizeof(cfi1->hash), | |
292 | (void *)cfi2 + sizeof(cfi2->hash), | |
293 | sizeof(struct cfi_state) - sizeof(struct hlist_node)); | |
294 | } | |
295 | ||
296 | static inline u32 cfi_key(struct cfi_state *cfi) | |
297 | { | |
298 | return jhash((void *)cfi + sizeof(cfi->hash), | |
299 | sizeof(*cfi) - sizeof(cfi->hash), 0); | |
300 | } | |
301 | ||
302 | static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi) | |
303 | { | |
304 | struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; | |
305 | struct cfi_state *obj; | |
306 | ||
307 | hlist_for_each_entry(obj, head, hash) { | |
308 | if (!cficmp(cfi, obj)) { | |
309 | nr_cfi_cache++; | |
310 | return obj; | |
311 | } | |
312 | } | |
313 | ||
314 | obj = cfi_alloc(); | |
315 | *obj = *cfi; | |
316 | hlist_add_head(&obj->hash, head); | |
317 | ||
318 | return obj; | |
319 | } | |
320 | ||
321 | static void cfi_hash_add(struct cfi_state *cfi) | |
322 | { | |
323 | struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; | |
324 | ||
325 | hlist_add_head(&cfi->hash, head); | |
326 | } | |
327 | ||
328 | static void *cfi_hash_alloc(unsigned long size) | |
329 | { | |
330 | cfi_bits = max(10, ilog2(size)); | |
331 | cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits, | |
332 | PROT_READ|PROT_WRITE, | |
333 | MAP_PRIVATE|MAP_ANON, -1, 0); | |
334 | if (cfi_hash == (void *)-1L) { | |
335 | WARN("mmap fail cfi_hash"); | |
336 | cfi_hash = NULL; | |
337 | } else if (stats) { | |
338 | printf("cfi_bits: %d\n", cfi_bits); | |
339 | } | |
340 | ||
341 | return cfi_hash; | |
342 | } | |
343 | ||
344 | static unsigned long nr_insns; | |
345 | static unsigned long nr_insns_visited; | |
346 | ||
347 | /* | |
348 | * Call the arch-specific instruction decoder for all the instructions and add | |
349 | * them to the global instruction list. | |
350 | */ | |
351 | static int decode_instructions(struct objtool_file *file) | |
352 | { | |
353 | struct section *sec; | |
354 | struct symbol *func; | |
355 | unsigned long offset; | |
356 | struct instruction *insn; | |
357 | int ret; | |
358 | ||
359 | for_each_sec(file, sec) { | |
360 | ||
361 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
362 | continue; | |
363 | ||
364 | if (strcmp(sec->name, ".altinstr_replacement") && | |
365 | strcmp(sec->name, ".altinstr_aux") && | |
366 | strncmp(sec->name, ".discard.", 9)) | |
367 | sec->text = true; | |
368 | ||
369 | if (!strcmp(sec->name, ".noinstr.text") || | |
370 | !strcmp(sec->name, ".entry.text")) | |
371 | sec->noinstr = true; | |
372 | ||
373 | for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { | |
374 | insn = malloc(sizeof(*insn)); | |
375 | if (!insn) { | |
376 | WARN("malloc failed"); | |
377 | return -1; | |
378 | } | |
379 | memset(insn, 0, sizeof(*insn)); | |
380 | INIT_LIST_HEAD(&insn->alts); | |
381 | INIT_LIST_HEAD(&insn->stack_ops); | |
382 | ||
383 | insn->sec = sec; | |
384 | insn->offset = offset; | |
385 | ||
386 | ret = arch_decode_instruction(file->elf, sec, offset, | |
387 | sec->sh.sh_size - offset, | |
388 | &insn->len, &insn->type, | |
389 | &insn->immediate, | |
390 | &insn->stack_ops); | |
391 | if (ret) | |
392 | goto err; | |
393 | ||
394 | hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset)); | |
395 | list_add_tail(&insn->list, &file->insn_list); | |
396 | nr_insns++; | |
397 | } | |
398 | ||
399 | list_for_each_entry(func, &sec->symbol_list, list) { | |
400 | if (func->type != STT_FUNC || func->alias != func) | |
401 | continue; | |
402 | ||
403 | if (!find_insn(file, sec, func->offset)) { | |
404 | WARN("%s(): can't find starting instruction", | |
405 | func->name); | |
406 | return -1; | |
407 | } | |
408 | ||
409 | sym_for_each_insn(file, func, insn) | |
410 | insn->func = func; | |
411 | } | |
412 | } | |
413 | ||
414 | if (stats) | |
415 | printf("nr_insns: %lu\n", nr_insns); | |
416 | ||
417 | return 0; | |
418 | ||
419 | err: | |
420 | free(insn); | |
421 | return ret; | |
422 | } | |
423 | ||
424 | static struct instruction *find_last_insn(struct objtool_file *file, | |
425 | struct section *sec) | |
426 | { | |
427 | struct instruction *insn = NULL; | |
428 | unsigned int offset; | |
429 | unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; | |
430 | ||
431 | for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) | |
432 | insn = find_insn(file, sec, offset); | |
433 | ||
434 | return insn; | |
435 | } | |
436 | ||
437 | /* | |
438 | * Mark "ud2" instructions and manually annotated dead ends. | |
439 | */ | |
440 | static int add_dead_ends(struct objtool_file *file) | |
441 | { | |
442 | struct section *sec; | |
443 | struct reloc *reloc; | |
444 | struct instruction *insn; | |
445 | ||
446 | /* | |
447 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
448 | * GCC 7 inserts it for certain divide-by-zero cases. | |
449 | */ | |
450 | for_each_insn(file, insn) | |
451 | if (insn->type == INSN_BUG) | |
452 | insn->dead_end = true; | |
453 | ||
454 | /* | |
455 | * Check for manually annotated dead ends. | |
456 | */ | |
457 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); | |
458 | if (!sec) | |
459 | goto reachable; | |
460 | ||
461 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
462 | if (reloc->sym->type != STT_SECTION) { | |
463 | WARN("unexpected relocation symbol type in %s", sec->name); | |
464 | return -1; | |
465 | } | |
466 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
467 | if (insn) | |
468 | insn = list_prev_entry(insn, list); | |
469 | else if (reloc->addend == reloc->sym->sec->sh.sh_size) { | |
470 | insn = find_last_insn(file, reloc->sym->sec); | |
471 | if (!insn) { | |
472 | WARN("can't find unreachable insn at %s+0x%" PRIx64, | |
473 | reloc->sym->sec->name, reloc->addend); | |
474 | return -1; | |
475 | } | |
476 | } else { | |
477 | WARN("can't find unreachable insn at %s+0x%" PRIx64, | |
478 | reloc->sym->sec->name, reloc->addend); | |
479 | return -1; | |
480 | } | |
481 | ||
482 | insn->dead_end = true; | |
483 | } | |
484 | ||
485 | reachable: | |
486 | /* | |
487 | * These manually annotated reachable checks are needed for GCC 4.4, | |
488 | * where the Linux unreachable() macro isn't supported. In that case | |
489 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
490 | * not a dead end. | |
491 | */ | |
492 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
493 | if (!sec) | |
494 | return 0; | |
495 | ||
496 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
497 | if (reloc->sym->type != STT_SECTION) { | |
498 | WARN("unexpected relocation symbol type in %s", sec->name); | |
499 | return -1; | |
500 | } | |
501 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
502 | if (insn) | |
503 | insn = list_prev_entry(insn, list); | |
504 | else if (reloc->addend == reloc->sym->sec->sh.sh_size) { | |
505 | insn = find_last_insn(file, reloc->sym->sec); | |
506 | if (!insn) { | |
507 | WARN("can't find reachable insn at %s+0x%" PRIx64, | |
508 | reloc->sym->sec->name, reloc->addend); | |
509 | return -1; | |
510 | } | |
511 | } else { | |
512 | WARN("can't find reachable insn at %s+0x%" PRIx64, | |
513 | reloc->sym->sec->name, reloc->addend); | |
514 | return -1; | |
515 | } | |
516 | ||
517 | insn->dead_end = false; | |
518 | } | |
519 | ||
520 | return 0; | |
521 | } | |
522 | ||
523 | static int create_static_call_sections(struct objtool_file *file) | |
524 | { | |
525 | struct section *sec; | |
526 | struct static_call_site *site; | |
527 | struct instruction *insn; | |
528 | struct symbol *key_sym; | |
529 | char *key_name, *tmp; | |
530 | int idx; | |
531 | ||
532 | sec = find_section_by_name(file->elf, ".static_call_sites"); | |
533 | if (sec) { | |
534 | INIT_LIST_HEAD(&file->static_call_list); | |
535 | WARN("file already has .static_call_sites section, skipping"); | |
536 | return 0; | |
537 | } | |
538 | ||
539 | if (list_empty(&file->static_call_list)) | |
540 | return 0; | |
541 | ||
542 | idx = 0; | |
543 | list_for_each_entry(insn, &file->static_call_list, call_node) | |
544 | idx++; | |
545 | ||
546 | sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE, | |
547 | sizeof(struct static_call_site), idx); | |
548 | if (!sec) | |
549 | return -1; | |
550 | ||
551 | idx = 0; | |
552 | list_for_each_entry(insn, &file->static_call_list, call_node) { | |
553 | ||
554 | site = (struct static_call_site *)sec->data->d_buf + idx; | |
555 | memset(site, 0, sizeof(struct static_call_site)); | |
556 | ||
557 | /* populate reloc for 'addr' */ | |
558 | if (elf_add_reloc_to_insn(file->elf, sec, | |
559 | idx * sizeof(struct static_call_site), | |
560 | R_X86_64_PC32, | |
561 | insn->sec, insn->offset)) | |
562 | return -1; | |
563 | ||
564 | /* find key symbol */ | |
565 | key_name = strdup(insn->call_dest->name); | |
566 | if (!key_name) { | |
567 | perror("strdup"); | |
568 | return -1; | |
569 | } | |
570 | if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR, | |
571 | STATIC_CALL_TRAMP_PREFIX_LEN)) { | |
572 | WARN("static_call: trampoline name malformed: %s", key_name); | |
573 | return -1; | |
574 | } | |
575 | tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN; | |
576 | memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN); | |
577 | ||
578 | key_sym = find_symbol_by_name(file->elf, tmp); | |
579 | if (!key_sym) { | |
580 | if (!module) { | |
581 | WARN("static_call: can't find static_call_key symbol: %s", tmp); | |
582 | return -1; | |
583 | } | |
584 | ||
585 | /* | |
586 | * For modules(), the key might not be exported, which | |
587 | * means the module can make static calls but isn't | |
588 | * allowed to change them. | |
589 | * | |
590 | * In that case we temporarily set the key to be the | |
591 | * trampoline address. This is fixed up in | |
592 | * static_call_add_module(). | |
593 | */ | |
594 | key_sym = insn->call_dest; | |
595 | } | |
596 | free(key_name); | |
597 | ||
598 | /* populate reloc for 'key' */ | |
599 | if (elf_add_reloc(file->elf, sec, | |
600 | idx * sizeof(struct static_call_site) + 4, | |
601 | R_X86_64_PC32, key_sym, | |
602 | is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) | |
603 | return -1; | |
604 | ||
605 | idx++; | |
606 | } | |
607 | ||
608 | return 0; | |
609 | } | |
610 | ||
611 | static int create_retpoline_sites_sections(struct objtool_file *file) | |
612 | { | |
613 | struct instruction *insn; | |
614 | struct section *sec; | |
615 | int idx; | |
616 | ||
617 | sec = find_section_by_name(file->elf, ".retpoline_sites"); | |
618 | if (sec) { | |
619 | WARN("file already has .retpoline_sites, skipping"); | |
620 | return 0; | |
621 | } | |
622 | ||
623 | idx = 0; | |
624 | list_for_each_entry(insn, &file->retpoline_call_list, call_node) | |
625 | idx++; | |
626 | ||
627 | if (!idx) | |
628 | return 0; | |
629 | ||
630 | sec = elf_create_section(file->elf, ".retpoline_sites", 0, | |
631 | sizeof(int), idx); | |
632 | if (!sec) { | |
633 | WARN("elf_create_section: .retpoline_sites"); | |
634 | return -1; | |
635 | } | |
636 | ||
637 | idx = 0; | |
638 | list_for_each_entry(insn, &file->retpoline_call_list, call_node) { | |
639 | ||
640 | int *site = (int *)sec->data->d_buf + idx; | |
641 | *site = 0; | |
642 | ||
643 | if (elf_add_reloc_to_insn(file->elf, sec, | |
644 | idx * sizeof(int), | |
645 | R_X86_64_PC32, | |
646 | insn->sec, insn->offset)) { | |
647 | WARN("elf_add_reloc_to_insn: .retpoline_sites"); | |
648 | return -1; | |
649 | } | |
650 | ||
651 | idx++; | |
652 | } | |
653 | ||
654 | return 0; | |
655 | } | |
656 | ||
657 | static int create_return_sites_sections(struct objtool_file *file) | |
658 | { | |
659 | struct instruction *insn; | |
660 | struct section *sec; | |
661 | int idx; | |
662 | ||
663 | sec = find_section_by_name(file->elf, ".return_sites"); | |
664 | if (sec) { | |
665 | WARN("file already has .return_sites, skipping"); | |
666 | return 0; | |
667 | } | |
668 | ||
669 | idx = 0; | |
670 | list_for_each_entry(insn, &file->return_thunk_list, call_node) | |
671 | idx++; | |
672 | ||
673 | if (!idx) | |
674 | return 0; | |
675 | ||
676 | sec = elf_create_section(file->elf, ".return_sites", 0, | |
677 | sizeof(int), idx); | |
678 | if (!sec) { | |
679 | WARN("elf_create_section: .return_sites"); | |
680 | return -1; | |
681 | } | |
682 | ||
683 | idx = 0; | |
684 | list_for_each_entry(insn, &file->return_thunk_list, call_node) { | |
685 | ||
686 | int *site = (int *)sec->data->d_buf + idx; | |
687 | *site = 0; | |
688 | ||
689 | if (elf_add_reloc_to_insn(file->elf, sec, | |
690 | idx * sizeof(int), | |
691 | R_X86_64_PC32, | |
692 | insn->sec, insn->offset)) { | |
693 | WARN("elf_add_reloc_to_insn: .return_sites"); | |
694 | return -1; | |
695 | } | |
696 | ||
697 | idx++; | |
698 | } | |
699 | ||
700 | return 0; | |
701 | } | |
702 | ||
703 | static int create_mcount_loc_sections(struct objtool_file *file) | |
704 | { | |
705 | struct section *sec; | |
706 | unsigned long *loc; | |
707 | struct instruction *insn; | |
708 | int idx; | |
709 | ||
710 | sec = find_section_by_name(file->elf, "__mcount_loc"); | |
711 | if (sec) { | |
712 | INIT_LIST_HEAD(&file->mcount_loc_list); | |
713 | WARN("file already has __mcount_loc section, skipping"); | |
714 | return 0; | |
715 | } | |
716 | ||
717 | if (list_empty(&file->mcount_loc_list)) | |
718 | return 0; | |
719 | ||
720 | idx = 0; | |
721 | list_for_each_entry(insn, &file->mcount_loc_list, call_node) | |
722 | idx++; | |
723 | ||
724 | sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx); | |
725 | if (!sec) | |
726 | return -1; | |
727 | ||
728 | idx = 0; | |
729 | list_for_each_entry(insn, &file->mcount_loc_list, call_node) { | |
730 | ||
731 | loc = (unsigned long *)sec->data->d_buf + idx; | |
732 | memset(loc, 0, sizeof(unsigned long)); | |
733 | ||
734 | if (elf_add_reloc_to_insn(file->elf, sec, | |
735 | idx * sizeof(unsigned long), | |
736 | R_X86_64_64, | |
737 | insn->sec, insn->offset)) | |
738 | return -1; | |
739 | ||
740 | idx++; | |
741 | } | |
742 | ||
743 | return 0; | |
744 | } | |
745 | ||
746 | /* | |
747 | * Warnings shouldn't be reported for ignored functions. | |
748 | */ | |
749 | static void add_ignores(struct objtool_file *file) | |
750 | { | |
751 | struct instruction *insn; | |
752 | struct section *sec; | |
753 | struct symbol *func; | |
754 | struct reloc *reloc; | |
755 | ||
756 | sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); | |
757 | if (!sec) | |
758 | return; | |
759 | ||
760 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
761 | switch (reloc->sym->type) { | |
762 | case STT_FUNC: | |
763 | func = reloc->sym; | |
764 | break; | |
765 | ||
766 | case STT_SECTION: | |
767 | func = find_func_by_offset(reloc->sym->sec, reloc->addend); | |
768 | if (!func) | |
769 | continue; | |
770 | break; | |
771 | ||
772 | default: | |
773 | WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type); | |
774 | continue; | |
775 | } | |
776 | ||
777 | func_for_each_insn(file, func, insn) | |
778 | insn->ignore = true; | |
779 | } | |
780 | } | |
781 | ||
782 | /* | |
783 | * This is a whitelist of functions that is allowed to be called with AC set. | |
784 | * The list is meant to be minimal and only contains compiler instrumentation | |
785 | * ABI and a few functions used to implement *_{to,from}_user() functions. | |
786 | * | |
787 | * These functions must not directly change AC, but may PUSHF/POPF. | |
788 | */ | |
789 | static const char *uaccess_safe_builtin[] = { | |
790 | /* KASAN */ | |
791 | "kasan_report", | |
792 | "kasan_check_range", | |
793 | /* KASAN out-of-line */ | |
794 | "__asan_loadN_noabort", | |
795 | "__asan_load1_noabort", | |
796 | "__asan_load2_noabort", | |
797 | "__asan_load4_noabort", | |
798 | "__asan_load8_noabort", | |
799 | "__asan_load16_noabort", | |
800 | "__asan_storeN_noabort", | |
801 | "__asan_store1_noabort", | |
802 | "__asan_store2_noabort", | |
803 | "__asan_store4_noabort", | |
804 | "__asan_store8_noabort", | |
805 | "__asan_store16_noabort", | |
806 | "__kasan_check_read", | |
807 | "__kasan_check_write", | |
808 | /* KASAN in-line */ | |
809 | "__asan_report_load_n_noabort", | |
810 | "__asan_report_load1_noabort", | |
811 | "__asan_report_load2_noabort", | |
812 | "__asan_report_load4_noabort", | |
813 | "__asan_report_load8_noabort", | |
814 | "__asan_report_load16_noabort", | |
815 | "__asan_report_store_n_noabort", | |
816 | "__asan_report_store1_noabort", | |
817 | "__asan_report_store2_noabort", | |
818 | "__asan_report_store4_noabort", | |
819 | "__asan_report_store8_noabort", | |
820 | "__asan_report_store16_noabort", | |
821 | /* KCSAN */ | |
822 | "__kcsan_check_access", | |
823 | "kcsan_found_watchpoint", | |
824 | "kcsan_setup_watchpoint", | |
825 | "kcsan_check_scoped_accesses", | |
826 | "kcsan_disable_current", | |
827 | "kcsan_enable_current_nowarn", | |
828 | /* KCSAN/TSAN */ | |
829 | "__tsan_func_entry", | |
830 | "__tsan_func_exit", | |
831 | "__tsan_read_range", | |
832 | "__tsan_write_range", | |
833 | "__tsan_read1", | |
834 | "__tsan_read2", | |
835 | "__tsan_read4", | |
836 | "__tsan_read8", | |
837 | "__tsan_read16", | |
838 | "__tsan_write1", | |
839 | "__tsan_write2", | |
840 | "__tsan_write4", | |
841 | "__tsan_write8", | |
842 | "__tsan_write16", | |
843 | "__tsan_read_write1", | |
844 | "__tsan_read_write2", | |
845 | "__tsan_read_write4", | |
846 | "__tsan_read_write8", | |
847 | "__tsan_read_write16", | |
848 | "__tsan_atomic8_load", | |
849 | "__tsan_atomic16_load", | |
850 | "__tsan_atomic32_load", | |
851 | "__tsan_atomic64_load", | |
852 | "__tsan_atomic8_store", | |
853 | "__tsan_atomic16_store", | |
854 | "__tsan_atomic32_store", | |
855 | "__tsan_atomic64_store", | |
856 | "__tsan_atomic8_exchange", | |
857 | "__tsan_atomic16_exchange", | |
858 | "__tsan_atomic32_exchange", | |
859 | "__tsan_atomic64_exchange", | |
860 | "__tsan_atomic8_fetch_add", | |
861 | "__tsan_atomic16_fetch_add", | |
862 | "__tsan_atomic32_fetch_add", | |
863 | "__tsan_atomic64_fetch_add", | |
864 | "__tsan_atomic8_fetch_sub", | |
865 | "__tsan_atomic16_fetch_sub", | |
866 | "__tsan_atomic32_fetch_sub", | |
867 | "__tsan_atomic64_fetch_sub", | |
868 | "__tsan_atomic8_fetch_and", | |
869 | "__tsan_atomic16_fetch_and", | |
870 | "__tsan_atomic32_fetch_and", | |
871 | "__tsan_atomic64_fetch_and", | |
872 | "__tsan_atomic8_fetch_or", | |
873 | "__tsan_atomic16_fetch_or", | |
874 | "__tsan_atomic32_fetch_or", | |
875 | "__tsan_atomic64_fetch_or", | |
876 | "__tsan_atomic8_fetch_xor", | |
877 | "__tsan_atomic16_fetch_xor", | |
878 | "__tsan_atomic32_fetch_xor", | |
879 | "__tsan_atomic64_fetch_xor", | |
880 | "__tsan_atomic8_fetch_nand", | |
881 | "__tsan_atomic16_fetch_nand", | |
882 | "__tsan_atomic32_fetch_nand", | |
883 | "__tsan_atomic64_fetch_nand", | |
884 | "__tsan_atomic8_compare_exchange_strong", | |
885 | "__tsan_atomic16_compare_exchange_strong", | |
886 | "__tsan_atomic32_compare_exchange_strong", | |
887 | "__tsan_atomic64_compare_exchange_strong", | |
888 | "__tsan_atomic8_compare_exchange_weak", | |
889 | "__tsan_atomic16_compare_exchange_weak", | |
890 | "__tsan_atomic32_compare_exchange_weak", | |
891 | "__tsan_atomic64_compare_exchange_weak", | |
892 | "__tsan_atomic8_compare_exchange_val", | |
893 | "__tsan_atomic16_compare_exchange_val", | |
894 | "__tsan_atomic32_compare_exchange_val", | |
895 | "__tsan_atomic64_compare_exchange_val", | |
896 | "__tsan_atomic_thread_fence", | |
897 | "__tsan_atomic_signal_fence", | |
898 | /* KCOV */ | |
899 | "write_comp_data", | |
900 | "check_kcov_mode", | |
901 | "__sanitizer_cov_trace_pc", | |
902 | "__sanitizer_cov_trace_const_cmp1", | |
903 | "__sanitizer_cov_trace_const_cmp2", | |
904 | "__sanitizer_cov_trace_const_cmp4", | |
905 | "__sanitizer_cov_trace_const_cmp8", | |
906 | "__sanitizer_cov_trace_cmp1", | |
907 | "__sanitizer_cov_trace_cmp2", | |
908 | "__sanitizer_cov_trace_cmp4", | |
909 | "__sanitizer_cov_trace_cmp8", | |
910 | "__sanitizer_cov_trace_switch", | |
911 | /* UBSAN */ | |
912 | "ubsan_type_mismatch_common", | |
913 | "__ubsan_handle_type_mismatch", | |
914 | "__ubsan_handle_type_mismatch_v1", | |
915 | "__ubsan_handle_shift_out_of_bounds", | |
916 | /* misc */ | |
917 | "csum_partial_copy_generic", | |
918 | "copy_mc_fragile", | |
919 | "copy_mc_fragile_handle_tail", | |
920 | "copy_mc_enhanced_fast_string", | |
921 | "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ | |
922 | NULL | |
923 | }; | |
924 | ||
925 | static void add_uaccess_safe(struct objtool_file *file) | |
926 | { | |
927 | struct symbol *func; | |
928 | const char **name; | |
929 | ||
930 | if (!uaccess) | |
931 | return; | |
932 | ||
933 | for (name = uaccess_safe_builtin; *name; name++) { | |
934 | func = find_symbol_by_name(file->elf, *name); | |
935 | if (!func) | |
936 | continue; | |
937 | ||
938 | func->uaccess_safe = true; | |
939 | } | |
940 | } | |
941 | ||
942 | /* | |
943 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
944 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
945 | * But it at least allows objtool to understand the control flow *around* the | |
946 | * retpoline. | |
947 | */ | |
948 | static int add_ignore_alternatives(struct objtool_file *file) | |
949 | { | |
950 | struct section *sec; | |
951 | struct reloc *reloc; | |
952 | struct instruction *insn; | |
953 | ||
954 | sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); | |
955 | if (!sec) | |
956 | return 0; | |
957 | ||
958 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
959 | if (reloc->sym->type != STT_SECTION) { | |
960 | WARN("unexpected relocation symbol type in %s", sec->name); | |
961 | return -1; | |
962 | } | |
963 | ||
964 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
965 | if (!insn) { | |
966 | WARN("bad .discard.ignore_alts entry"); | |
967 | return -1; | |
968 | } | |
969 | ||
970 | insn->ignore_alts = true; | |
971 | } | |
972 | ||
973 | return 0; | |
974 | } | |
975 | ||
976 | __weak bool arch_is_retpoline(struct symbol *sym) | |
977 | { | |
978 | return false; | |
979 | } | |
980 | ||
981 | __weak bool arch_is_rethunk(struct symbol *sym) | |
982 | { | |
983 | return false; | |
984 | } | |
985 | ||
986 | #define NEGATIVE_RELOC ((void *)-1L) | |
987 | ||
988 | static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) | |
989 | { | |
990 | if (insn->reloc == NEGATIVE_RELOC) | |
991 | return NULL; | |
992 | ||
993 | if (!insn->reloc) { | |
994 | insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec, | |
995 | insn->offset, insn->len); | |
996 | if (!insn->reloc) { | |
997 | insn->reloc = NEGATIVE_RELOC; | |
998 | return NULL; | |
999 | } | |
1000 | } | |
1001 | ||
1002 | return insn->reloc; | |
1003 | } | |
1004 | ||
1005 | static void remove_insn_ops(struct instruction *insn) | |
1006 | { | |
1007 | struct stack_op *op, *tmp; | |
1008 | ||
1009 | list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { | |
1010 | list_del(&op->list); | |
1011 | free(op); | |
1012 | } | |
1013 | } | |
1014 | ||
1015 | static void annotate_call_site(struct objtool_file *file, | |
1016 | struct instruction *insn, bool sibling) | |
1017 | { | |
1018 | struct reloc *reloc = insn_reloc(file, insn); | |
1019 | struct symbol *sym = insn->call_dest; | |
1020 | ||
1021 | if (!sym) | |
1022 | sym = reloc->sym; | |
1023 | ||
1024 | /* | |
1025 | * Alternative replacement code is just template code which is | |
1026 | * sometimes copied to the original instruction. For now, don't | |
1027 | * annotate it. (In the future we might consider annotating the | |
1028 | * original instruction if/when it ever makes sense to do so.) | |
1029 | */ | |
1030 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
1031 | return; | |
1032 | ||
1033 | if (sym->static_call_tramp) { | |
1034 | list_add_tail(&insn->call_node, &file->static_call_list); | |
1035 | return; | |
1036 | } | |
1037 | ||
1038 | if (sym->retpoline_thunk) { | |
1039 | list_add_tail(&insn->call_node, &file->retpoline_call_list); | |
1040 | return; | |
1041 | } | |
1042 | ||
1043 | /* | |
1044 | * Many compilers cannot disable KCOV with a function attribute | |
1045 | * so they need a little help, NOP out any KCOV calls from noinstr | |
1046 | * text. | |
1047 | */ | |
1048 | if (insn->sec->noinstr && sym->kcov) { | |
1049 | if (reloc) { | |
1050 | reloc->type = R_NONE; | |
1051 | elf_write_reloc(file->elf, reloc); | |
1052 | } | |
1053 | ||
1054 | elf_write_insn(file->elf, insn->sec, | |
1055 | insn->offset, insn->len, | |
1056 | sibling ? arch_ret_insn(insn->len) | |
1057 | : arch_nop_insn(insn->len)); | |
1058 | ||
1059 | insn->type = sibling ? INSN_RETURN : INSN_NOP; | |
1060 | ||
1061 | if (sibling) { | |
1062 | /* | |
1063 | * We've replaced the tail-call JMP insn by two new | |
1064 | * insn: RET; INT3, except we only have a single struct | |
1065 | * insn here. Mark it retpoline_safe to avoid the SLS | |
1066 | * warning, instead of adding another insn. | |
1067 | */ | |
1068 | insn->retpoline_safe = true; | |
1069 | } | |
1070 | ||
1071 | return; | |
1072 | } | |
1073 | ||
1074 | if (mcount && sym->fentry) { | |
1075 | if (sibling) | |
1076 | WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset); | |
1077 | ||
1078 | if (reloc) { | |
1079 | reloc->type = R_NONE; | |
1080 | elf_write_reloc(file->elf, reloc); | |
1081 | } | |
1082 | ||
1083 | elf_write_insn(file->elf, insn->sec, | |
1084 | insn->offset, insn->len, | |
1085 | arch_nop_insn(insn->len)); | |
1086 | ||
1087 | insn->type = INSN_NOP; | |
1088 | ||
1089 | list_add_tail(&insn->call_node, &file->mcount_loc_list); | |
1090 | return; | |
1091 | } | |
1092 | } | |
1093 | ||
1094 | static void add_call_dest(struct objtool_file *file, struct instruction *insn, | |
1095 | struct symbol *dest, bool sibling) | |
1096 | { | |
1097 | insn->call_dest = dest; | |
1098 | if (!dest) | |
1099 | return; | |
1100 | ||
1101 | /* | |
1102 | * Whatever stack impact regular CALLs have, should be undone | |
1103 | * by the RETURN of the called function. | |
1104 | * | |
1105 | * Annotated intra-function calls retain the stack_ops but | |
1106 | * are converted to JUMP, see read_intra_function_calls(). | |
1107 | */ | |
1108 | remove_insn_ops(insn); | |
1109 | ||
1110 | annotate_call_site(file, insn, sibling); | |
1111 | } | |
1112 | ||
1113 | static void add_retpoline_call(struct objtool_file *file, struct instruction *insn) | |
1114 | { | |
1115 | /* | |
1116 | * Retpoline calls/jumps are really dynamic calls/jumps in disguise, | |
1117 | * so convert them accordingly. | |
1118 | */ | |
1119 | switch (insn->type) { | |
1120 | case INSN_CALL: | |
1121 | insn->type = INSN_CALL_DYNAMIC; | |
1122 | break; | |
1123 | case INSN_JUMP_UNCONDITIONAL: | |
1124 | insn->type = INSN_JUMP_DYNAMIC; | |
1125 | break; | |
1126 | case INSN_JUMP_CONDITIONAL: | |
1127 | insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; | |
1128 | break; | |
1129 | default: | |
1130 | return; | |
1131 | } | |
1132 | ||
1133 | insn->retpoline_safe = true; | |
1134 | ||
1135 | /* | |
1136 | * Whatever stack impact regular CALLs have, should be undone | |
1137 | * by the RETURN of the called function. | |
1138 | * | |
1139 | * Annotated intra-function calls retain the stack_ops but | |
1140 | * are converted to JUMP, see read_intra_function_calls(). | |
1141 | */ | |
1142 | remove_insn_ops(insn); | |
1143 | ||
1144 | annotate_call_site(file, insn, false); | |
1145 | } | |
1146 | ||
1147 | static void add_return_call(struct objtool_file *file, struct instruction *insn) | |
1148 | { | |
1149 | /* | |
1150 | * Return thunk tail calls are really just returns in disguise, | |
1151 | * so convert them accordingly. | |
1152 | */ | |
1153 | insn->type = INSN_RETURN; | |
1154 | insn->retpoline_safe = true; | |
1155 | ||
1156 | list_add_tail(&insn->call_node, &file->return_thunk_list); | |
1157 | } | |
1158 | ||
1159 | /* | |
1160 | * Find the destination instructions for all jumps. | |
1161 | */ | |
1162 | static int add_jump_destinations(struct objtool_file *file) | |
1163 | { | |
1164 | struct instruction *insn; | |
1165 | struct reloc *reloc; | |
1166 | struct section *dest_sec; | |
1167 | unsigned long dest_off; | |
1168 | ||
1169 | for_each_insn(file, insn) { | |
1170 | if (!is_static_jump(insn)) | |
1171 | continue; | |
1172 | ||
1173 | reloc = insn_reloc(file, insn); | |
1174 | if (!reloc) { | |
1175 | dest_sec = insn->sec; | |
1176 | dest_off = arch_jump_destination(insn); | |
1177 | } else if (reloc->sym->type == STT_SECTION) { | |
1178 | dest_sec = reloc->sym->sec; | |
1179 | dest_off = arch_dest_reloc_offset(reloc->addend); | |
1180 | } else if (reloc->sym->retpoline_thunk) { | |
1181 | add_retpoline_call(file, insn); | |
1182 | continue; | |
1183 | } else if (reloc->sym->return_thunk) { | |
1184 | add_return_call(file, insn); | |
1185 | continue; | |
1186 | } else if (insn->func) { | |
1187 | /* internal or external sibling call (with reloc) */ | |
1188 | add_call_dest(file, insn, reloc->sym, true); | |
1189 | continue; | |
1190 | } else if (reloc->sym->sec->idx) { | |
1191 | dest_sec = reloc->sym->sec; | |
1192 | dest_off = reloc->sym->sym.st_value + | |
1193 | arch_dest_reloc_offset(reloc->addend); | |
1194 | } else { | |
1195 | /* non-func asm code jumping to another file */ | |
1196 | continue; | |
1197 | } | |
1198 | ||
1199 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
1200 | if (!insn->jump_dest) { | |
1201 | ||
1202 | /* | |
1203 | * This is a special case where an alt instruction | |
1204 | * jumps past the end of the section. These are | |
1205 | * handled later in handle_group_alt(). | |
1206 | */ | |
1207 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
1208 | continue; | |
1209 | ||
1210 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
1211 | insn->sec, insn->offset, dest_sec->name, | |
1212 | dest_off); | |
1213 | return -1; | |
1214 | } | |
1215 | ||
1216 | /* | |
1217 | * Cross-function jump. | |
1218 | */ | |
1219 | if (insn->func && insn->jump_dest->func && | |
1220 | insn->func != insn->jump_dest->func) { | |
1221 | ||
1222 | /* | |
1223 | * For GCC 8+, create parent/child links for any cold | |
1224 | * subfunctions. This is _mostly_ redundant with a | |
1225 | * similar initialization in read_symbols(). | |
1226 | * | |
1227 | * If a function has aliases, we want the *first* such | |
1228 | * function in the symbol table to be the subfunction's | |
1229 | * parent. In that case we overwrite the | |
1230 | * initialization done in read_symbols(). | |
1231 | * | |
1232 | * However this code can't completely replace the | |
1233 | * read_symbols() code because this doesn't detect the | |
1234 | * case where the parent function's only reference to a | |
1235 | * subfunction is through a jump table. | |
1236 | */ | |
1237 | if (!strstr(insn->func->name, ".cold") && | |
1238 | strstr(insn->jump_dest->func->name, ".cold")) { | |
1239 | insn->func->cfunc = insn->jump_dest->func; | |
1240 | insn->jump_dest->func->pfunc = insn->func; | |
1241 | ||
1242 | } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && | |
1243 | insn->jump_dest->offset == insn->jump_dest->func->offset) { | |
1244 | /* internal sibling call (without reloc) */ | |
1245 | add_call_dest(file, insn, insn->jump_dest->func, true); | |
1246 | } | |
1247 | } | |
1248 | } | |
1249 | ||
1250 | return 0; | |
1251 | } | |
1252 | ||
1253 | static struct symbol *find_call_destination(struct section *sec, unsigned long offset) | |
1254 | { | |
1255 | struct symbol *call_dest; | |
1256 | ||
1257 | call_dest = find_func_by_offset(sec, offset); | |
1258 | if (!call_dest) | |
1259 | call_dest = find_symbol_by_offset(sec, offset); | |
1260 | ||
1261 | return call_dest; | |
1262 | } | |
1263 | ||
1264 | /* | |
1265 | * Find the destination instructions for all calls. | |
1266 | */ | |
1267 | static int add_call_destinations(struct objtool_file *file) | |
1268 | { | |
1269 | struct instruction *insn; | |
1270 | unsigned long dest_off; | |
1271 | struct symbol *dest; | |
1272 | struct reloc *reloc; | |
1273 | ||
1274 | for_each_insn(file, insn) { | |
1275 | if (insn->type != INSN_CALL) | |
1276 | continue; | |
1277 | ||
1278 | reloc = insn_reloc(file, insn); | |
1279 | if (!reloc) { | |
1280 | dest_off = arch_jump_destination(insn); | |
1281 | dest = find_call_destination(insn->sec, dest_off); | |
1282 | ||
1283 | add_call_dest(file, insn, dest, false); | |
1284 | ||
1285 | if (insn->ignore) | |
1286 | continue; | |
1287 | ||
1288 | if (!insn->call_dest) { | |
1289 | WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset); | |
1290 | return -1; | |
1291 | } | |
1292 | ||
1293 | if (insn->func && insn->call_dest->type != STT_FUNC) { | |
1294 | WARN_FUNC("unsupported call to non-function", | |
1295 | insn->sec, insn->offset); | |
1296 | return -1; | |
1297 | } | |
1298 | ||
1299 | } else if (reloc->sym->type == STT_SECTION) { | |
1300 | dest_off = arch_dest_reloc_offset(reloc->addend); | |
1301 | dest = find_call_destination(reloc->sym->sec, dest_off); | |
1302 | if (!dest) { | |
1303 | WARN_FUNC("can't find call dest symbol at %s+0x%lx", | |
1304 | insn->sec, insn->offset, | |
1305 | reloc->sym->sec->name, | |
1306 | dest_off); | |
1307 | return -1; | |
1308 | } | |
1309 | ||
1310 | add_call_dest(file, insn, dest, false); | |
1311 | ||
1312 | } else if (reloc->sym->retpoline_thunk) { | |
1313 | add_retpoline_call(file, insn); | |
1314 | ||
1315 | } else | |
1316 | add_call_dest(file, insn, reloc->sym, false); | |
1317 | } | |
1318 | ||
1319 | return 0; | |
1320 | } | |
1321 | ||
1322 | /* | |
1323 | * The .alternatives section requires some extra special care over and above | |
1324 | * other special sections because alternatives are patched in place. | |
1325 | */ | |
1326 | static int handle_group_alt(struct objtool_file *file, | |
1327 | struct special_alt *special_alt, | |
1328 | struct instruction *orig_insn, | |
1329 | struct instruction **new_insn) | |
1330 | { | |
1331 | struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL; | |
1332 | struct alt_group *orig_alt_group, *new_alt_group; | |
1333 | unsigned long dest_off; | |
1334 | ||
1335 | ||
1336 | orig_alt_group = malloc(sizeof(*orig_alt_group)); | |
1337 | if (!orig_alt_group) { | |
1338 | WARN("malloc failed"); | |
1339 | return -1; | |
1340 | } | |
1341 | orig_alt_group->cfi = calloc(special_alt->orig_len, | |
1342 | sizeof(struct cfi_state *)); | |
1343 | if (!orig_alt_group->cfi) { | |
1344 | WARN("calloc failed"); | |
1345 | return -1; | |
1346 | } | |
1347 | ||
1348 | last_orig_insn = NULL; | |
1349 | insn = orig_insn; | |
1350 | sec_for_each_insn_from(file, insn) { | |
1351 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
1352 | break; | |
1353 | ||
1354 | insn->alt_group = orig_alt_group; | |
1355 | last_orig_insn = insn; | |
1356 | } | |
1357 | orig_alt_group->orig_group = NULL; | |
1358 | orig_alt_group->first_insn = orig_insn; | |
1359 | orig_alt_group->last_insn = last_orig_insn; | |
1360 | ||
1361 | ||
1362 | new_alt_group = malloc(sizeof(*new_alt_group)); | |
1363 | if (!new_alt_group) { | |
1364 | WARN("malloc failed"); | |
1365 | return -1; | |
1366 | } | |
1367 | ||
1368 | if (special_alt->new_len < special_alt->orig_len) { | |
1369 | /* | |
1370 | * Insert a fake nop at the end to make the replacement | |
1371 | * alt_group the same size as the original. This is needed to | |
1372 | * allow propagate_alt_cfi() to do its magic. When the last | |
1373 | * instruction affects the stack, the instruction after it (the | |
1374 | * nop) will propagate the new state to the shared CFI array. | |
1375 | */ | |
1376 | nop = malloc(sizeof(*nop)); | |
1377 | if (!nop) { | |
1378 | WARN("malloc failed"); | |
1379 | return -1; | |
1380 | } | |
1381 | memset(nop, 0, sizeof(*nop)); | |
1382 | INIT_LIST_HEAD(&nop->alts); | |
1383 | INIT_LIST_HEAD(&nop->stack_ops); | |
1384 | ||
1385 | nop->sec = special_alt->new_sec; | |
1386 | nop->offset = special_alt->new_off + special_alt->new_len; | |
1387 | nop->len = special_alt->orig_len - special_alt->new_len; | |
1388 | nop->type = INSN_NOP; | |
1389 | nop->func = orig_insn->func; | |
1390 | nop->alt_group = new_alt_group; | |
1391 | nop->ignore = orig_insn->ignore_alts; | |
1392 | } | |
1393 | ||
1394 | if (!special_alt->new_len) { | |
1395 | *new_insn = nop; | |
1396 | goto end; | |
1397 | } | |
1398 | ||
1399 | insn = *new_insn; | |
1400 | sec_for_each_insn_from(file, insn) { | |
1401 | struct reloc *alt_reloc; | |
1402 | ||
1403 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
1404 | break; | |
1405 | ||
1406 | last_new_insn = insn; | |
1407 | ||
1408 | insn->ignore = orig_insn->ignore_alts; | |
1409 | insn->func = orig_insn->func; | |
1410 | insn->alt_group = new_alt_group; | |
1411 | ||
1412 | /* | |
1413 | * Since alternative replacement code is copy/pasted by the | |
1414 | * kernel after applying relocations, generally such code can't | |
1415 | * have relative-address relocation references to outside the | |
1416 | * .altinstr_replacement section, unless the arch's | |
1417 | * alternatives code can adjust the relative offsets | |
1418 | * accordingly. | |
1419 | */ | |
1420 | alt_reloc = insn_reloc(file, insn); | |
1421 | if (alt_reloc && | |
1422 | !arch_support_alt_relocation(special_alt, insn, alt_reloc)) { | |
1423 | ||
1424 | WARN_FUNC("unsupported relocation in alternatives section", | |
1425 | insn->sec, insn->offset); | |
1426 | return -1; | |
1427 | } | |
1428 | ||
1429 | if (!is_static_jump(insn)) | |
1430 | continue; | |
1431 | ||
1432 | if (!insn->immediate) | |
1433 | continue; | |
1434 | ||
1435 | dest_off = arch_jump_destination(insn); | |
1436 | if (dest_off == special_alt->new_off + special_alt->new_len) | |
1437 | insn->jump_dest = next_insn_same_sec(file, last_orig_insn); | |
1438 | ||
1439 | if (!insn->jump_dest) { | |
1440 | WARN_FUNC("can't find alternative jump destination", | |
1441 | insn->sec, insn->offset); | |
1442 | return -1; | |
1443 | } | |
1444 | } | |
1445 | ||
1446 | if (!last_new_insn) { | |
1447 | WARN_FUNC("can't find last new alternative instruction", | |
1448 | special_alt->new_sec, special_alt->new_off); | |
1449 | return -1; | |
1450 | } | |
1451 | ||
1452 | if (nop) | |
1453 | list_add(&nop->list, &last_new_insn->list); | |
1454 | end: | |
1455 | new_alt_group->orig_group = orig_alt_group; | |
1456 | new_alt_group->first_insn = *new_insn; | |
1457 | new_alt_group->last_insn = nop ? : last_new_insn; | |
1458 | new_alt_group->cfi = orig_alt_group->cfi; | |
1459 | return 0; | |
1460 | } | |
1461 | ||
1462 | /* | |
1463 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
1464 | * If the original instruction is a jump, make the alt entry an effective nop | |
1465 | * by just skipping the original instruction. | |
1466 | */ | |
1467 | static int handle_jump_alt(struct objtool_file *file, | |
1468 | struct special_alt *special_alt, | |
1469 | struct instruction *orig_insn, | |
1470 | struct instruction **new_insn) | |
1471 | { | |
1472 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL && | |
1473 | orig_insn->type != INSN_NOP) { | |
1474 | ||
1475 | WARN_FUNC("unsupported instruction at jump label", | |
1476 | orig_insn->sec, orig_insn->offset); | |
1477 | return -1; | |
1478 | } | |
1479 | ||
1480 | if (special_alt->key_addend & 2) { | |
1481 | struct reloc *reloc = insn_reloc(file, orig_insn); | |
1482 | ||
1483 | if (reloc) { | |
1484 | reloc->type = R_NONE; | |
1485 | elf_write_reloc(file->elf, reloc); | |
1486 | } | |
1487 | elf_write_insn(file->elf, orig_insn->sec, | |
1488 | orig_insn->offset, orig_insn->len, | |
1489 | arch_nop_insn(orig_insn->len)); | |
1490 | orig_insn->type = INSN_NOP; | |
1491 | } | |
1492 | ||
1493 | if (orig_insn->type == INSN_NOP) { | |
1494 | if (orig_insn->len == 2) | |
1495 | file->jl_nop_short++; | |
1496 | else | |
1497 | file->jl_nop_long++; | |
1498 | ||
1499 | return 0; | |
1500 | } | |
1501 | ||
1502 | if (orig_insn->len == 2) | |
1503 | file->jl_short++; | |
1504 | else | |
1505 | file->jl_long++; | |
1506 | ||
1507 | *new_insn = list_next_entry(orig_insn, list); | |
1508 | return 0; | |
1509 | } | |
1510 | ||
1511 | /* | |
1512 | * Read all the special sections which have alternate instructions which can be | |
1513 | * patched in or redirected to at runtime. Each instruction having alternate | |
1514 | * instruction(s) has them added to its insn->alts list, which will be | |
1515 | * traversed in validate_branch(). | |
1516 | */ | |
1517 | static int add_special_section_alts(struct objtool_file *file) | |
1518 | { | |
1519 | struct list_head special_alts; | |
1520 | struct instruction *orig_insn, *new_insn; | |
1521 | struct special_alt *special_alt, *tmp; | |
1522 | struct alternative *alt; | |
1523 | int ret; | |
1524 | ||
1525 | ret = special_get_alts(file->elf, &special_alts); | |
1526 | if (ret) | |
1527 | return ret; | |
1528 | ||
1529 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
1530 | ||
1531 | orig_insn = find_insn(file, special_alt->orig_sec, | |
1532 | special_alt->orig_off); | |
1533 | if (!orig_insn) { | |
1534 | WARN_FUNC("special: can't find orig instruction", | |
1535 | special_alt->orig_sec, special_alt->orig_off); | |
1536 | ret = -1; | |
1537 | goto out; | |
1538 | } | |
1539 | ||
1540 | new_insn = NULL; | |
1541 | if (!special_alt->group || special_alt->new_len) { | |
1542 | new_insn = find_insn(file, special_alt->new_sec, | |
1543 | special_alt->new_off); | |
1544 | if (!new_insn) { | |
1545 | WARN_FUNC("special: can't find new instruction", | |
1546 | special_alt->new_sec, | |
1547 | special_alt->new_off); | |
1548 | ret = -1; | |
1549 | goto out; | |
1550 | } | |
1551 | } | |
1552 | ||
1553 | if (special_alt->group) { | |
1554 | if (!special_alt->orig_len) { | |
1555 | WARN_FUNC("empty alternative entry", | |
1556 | orig_insn->sec, orig_insn->offset); | |
1557 | continue; | |
1558 | } | |
1559 | ||
1560 | ret = handle_group_alt(file, special_alt, orig_insn, | |
1561 | &new_insn); | |
1562 | if (ret) | |
1563 | goto out; | |
1564 | } else if (special_alt->jump_or_nop) { | |
1565 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
1566 | &new_insn); | |
1567 | if (ret) | |
1568 | goto out; | |
1569 | } | |
1570 | ||
1571 | alt = malloc(sizeof(*alt)); | |
1572 | if (!alt) { | |
1573 | WARN("malloc failed"); | |
1574 | ret = -1; | |
1575 | goto out; | |
1576 | } | |
1577 | ||
1578 | alt->insn = new_insn; | |
1579 | alt->skip_orig = special_alt->skip_orig; | |
1580 | orig_insn->ignore_alts |= special_alt->skip_alt; | |
1581 | list_add_tail(&alt->list, &orig_insn->alts); | |
1582 | ||
1583 | list_del(&special_alt->list); | |
1584 | free(special_alt); | |
1585 | } | |
1586 | ||
1587 | if (stats) { | |
1588 | printf("jl\\\tNOP\tJMP\n"); | |
1589 | printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short); | |
1590 | printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long); | |
1591 | } | |
1592 | ||
1593 | out: | |
1594 | return ret; | |
1595 | } | |
1596 | ||
1597 | static int add_jump_table(struct objtool_file *file, struct instruction *insn, | |
1598 | struct reloc *table) | |
1599 | { | |
1600 | struct reloc *reloc = table; | |
1601 | struct instruction *dest_insn; | |
1602 | struct alternative *alt; | |
1603 | struct symbol *pfunc = insn->func->pfunc; | |
1604 | unsigned int prev_offset = 0; | |
1605 | ||
1606 | /* | |
1607 | * Each @reloc is a switch table relocation which points to the target | |
1608 | * instruction. | |
1609 | */ | |
1610 | list_for_each_entry_from(reloc, &table->sec->reloc_list, list) { | |
1611 | ||
1612 | /* Check for the end of the table: */ | |
1613 | if (reloc != table && reloc->jump_table_start) | |
1614 | break; | |
1615 | ||
1616 | /* Make sure the table entries are consecutive: */ | |
1617 | if (prev_offset && reloc->offset != prev_offset + 8) | |
1618 | break; | |
1619 | ||
1620 | /* Detect function pointers from contiguous objects: */ | |
1621 | if (reloc->sym->sec == pfunc->sec && | |
1622 | reloc->addend == pfunc->offset) | |
1623 | break; | |
1624 | ||
1625 | dest_insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1626 | if (!dest_insn) | |
1627 | break; | |
1628 | ||
1629 | /* Make sure the destination is in the same function: */ | |
1630 | if (!dest_insn->func || dest_insn->func->pfunc != pfunc) | |
1631 | break; | |
1632 | ||
1633 | alt = malloc(sizeof(*alt)); | |
1634 | if (!alt) { | |
1635 | WARN("malloc failed"); | |
1636 | return -1; | |
1637 | } | |
1638 | ||
1639 | alt->insn = dest_insn; | |
1640 | list_add_tail(&alt->list, &insn->alts); | |
1641 | prev_offset = reloc->offset; | |
1642 | } | |
1643 | ||
1644 | if (!prev_offset) { | |
1645 | WARN_FUNC("can't find switch jump table", | |
1646 | insn->sec, insn->offset); | |
1647 | return -1; | |
1648 | } | |
1649 | ||
1650 | return 0; | |
1651 | } | |
1652 | ||
1653 | /* | |
1654 | * find_jump_table() - Given a dynamic jump, find the switch jump table | |
1655 | * associated with it. | |
1656 | */ | |
1657 | static struct reloc *find_jump_table(struct objtool_file *file, | |
1658 | struct symbol *func, | |
1659 | struct instruction *insn) | |
1660 | { | |
1661 | struct reloc *table_reloc; | |
1662 | struct instruction *dest_insn, *orig_insn = insn; | |
1663 | ||
1664 | /* | |
1665 | * Backward search using the @first_jump_src links, these help avoid | |
1666 | * much of the 'in between' code. Which avoids us getting confused by | |
1667 | * it. | |
1668 | */ | |
1669 | for (; | |
1670 | insn && insn->func && insn->func->pfunc == func; | |
1671 | insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) { | |
1672 | ||
1673 | if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) | |
1674 | break; | |
1675 | ||
1676 | /* allow small jumps within the range */ | |
1677 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
1678 | insn->jump_dest && | |
1679 | (insn->jump_dest->offset <= insn->offset || | |
1680 | insn->jump_dest->offset > orig_insn->offset)) | |
1681 | break; | |
1682 | ||
1683 | table_reloc = arch_find_switch_table(file, insn); | |
1684 | if (!table_reloc) | |
1685 | continue; | |
1686 | dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend); | |
1687 | if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) | |
1688 | continue; | |
1689 | ||
1690 | return table_reloc; | |
1691 | } | |
1692 | ||
1693 | return NULL; | |
1694 | } | |
1695 | ||
1696 | /* | |
1697 | * First pass: Mark the head of each jump table so that in the next pass, | |
1698 | * we know when a given jump table ends and the next one starts. | |
1699 | */ | |
1700 | static void mark_func_jump_tables(struct objtool_file *file, | |
1701 | struct symbol *func) | |
1702 | { | |
1703 | struct instruction *insn, *last = NULL; | |
1704 | struct reloc *reloc; | |
1705 | ||
1706 | func_for_each_insn(file, func, insn) { | |
1707 | if (!last) | |
1708 | last = insn; | |
1709 | ||
1710 | /* | |
1711 | * Store back-pointers for unconditional forward jumps such | |
1712 | * that find_jump_table() can back-track using those and | |
1713 | * avoid some potentially confusing code. | |
1714 | */ | |
1715 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
1716 | insn->offset > last->offset && | |
1717 | insn->jump_dest->offset > insn->offset && | |
1718 | !insn->jump_dest->first_jump_src) { | |
1719 | ||
1720 | insn->jump_dest->first_jump_src = insn; | |
1721 | last = insn->jump_dest; | |
1722 | } | |
1723 | ||
1724 | if (insn->type != INSN_JUMP_DYNAMIC) | |
1725 | continue; | |
1726 | ||
1727 | reloc = find_jump_table(file, func, insn); | |
1728 | if (reloc) { | |
1729 | reloc->jump_table_start = true; | |
1730 | insn->jump_table = reloc; | |
1731 | } | |
1732 | } | |
1733 | } | |
1734 | ||
1735 | static int add_func_jump_tables(struct objtool_file *file, | |
1736 | struct symbol *func) | |
1737 | { | |
1738 | struct instruction *insn; | |
1739 | int ret; | |
1740 | ||
1741 | func_for_each_insn(file, func, insn) { | |
1742 | if (!insn->jump_table) | |
1743 | continue; | |
1744 | ||
1745 | ret = add_jump_table(file, insn, insn->jump_table); | |
1746 | if (ret) | |
1747 | return ret; | |
1748 | } | |
1749 | ||
1750 | return 0; | |
1751 | } | |
1752 | ||
1753 | /* | |
1754 | * For some switch statements, gcc generates a jump table in the .rodata | |
1755 | * section which contains a list of addresses within the function to jump to. | |
1756 | * This finds these jump tables and adds them to the insn->alts lists. | |
1757 | */ | |
1758 | static int add_jump_table_alts(struct objtool_file *file) | |
1759 | { | |
1760 | struct section *sec; | |
1761 | struct symbol *func; | |
1762 | int ret; | |
1763 | ||
1764 | if (!file->rodata) | |
1765 | return 0; | |
1766 | ||
1767 | for_each_sec(file, sec) { | |
1768 | list_for_each_entry(func, &sec->symbol_list, list) { | |
1769 | if (func->type != STT_FUNC) | |
1770 | continue; | |
1771 | ||
1772 | mark_func_jump_tables(file, func); | |
1773 | ret = add_func_jump_tables(file, func); | |
1774 | if (ret) | |
1775 | return ret; | |
1776 | } | |
1777 | } | |
1778 | ||
1779 | return 0; | |
1780 | } | |
1781 | ||
1782 | static void set_func_state(struct cfi_state *state) | |
1783 | { | |
1784 | state->cfa = initial_func_cfi.cfa; | |
1785 | memcpy(&state->regs, &initial_func_cfi.regs, | |
1786 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
1787 | state->stack_size = initial_func_cfi.cfa.offset; | |
1788 | } | |
1789 | ||
1790 | static int read_unwind_hints(struct objtool_file *file) | |
1791 | { | |
1792 | struct cfi_state cfi = init_cfi; | |
1793 | struct section *sec, *relocsec; | |
1794 | struct unwind_hint *hint; | |
1795 | struct instruction *insn; | |
1796 | struct reloc *reloc; | |
1797 | int i; | |
1798 | ||
1799 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1800 | if (!sec) | |
1801 | return 0; | |
1802 | ||
1803 | relocsec = sec->reloc; | |
1804 | if (!relocsec) { | |
1805 | WARN("missing .rela.discard.unwind_hints section"); | |
1806 | return -1; | |
1807 | } | |
1808 | ||
1809 | if (sec->sh.sh_size % sizeof(struct unwind_hint)) { | |
1810 | WARN("struct unwind_hint size mismatch"); | |
1811 | return -1; | |
1812 | } | |
1813 | ||
1814 | file->hints = true; | |
1815 | ||
1816 | for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { | |
1817 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1818 | ||
1819 | reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); | |
1820 | if (!reloc) { | |
1821 | WARN("can't find reloc for unwind_hints[%d]", i); | |
1822 | return -1; | |
1823 | } | |
1824 | ||
1825 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1826 | if (!insn) { | |
1827 | WARN("can't find insn for unwind_hints[%d]", i); | |
1828 | return -1; | |
1829 | } | |
1830 | ||
1831 | insn->hint = true; | |
1832 | ||
1833 | if (hint->type == UNWIND_HINT_TYPE_FUNC) { | |
1834 | insn->cfi = &func_cfi; | |
1835 | continue; | |
1836 | } | |
1837 | ||
1838 | if (insn->cfi) | |
1839 | cfi = *(insn->cfi); | |
1840 | ||
1841 | if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) { | |
1842 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1843 | insn->sec, insn->offset, hint->sp_reg); | |
1844 | return -1; | |
1845 | } | |
1846 | ||
1847 | cfi.cfa.offset = bswap_if_needed(hint->sp_offset); | |
1848 | cfi.type = hint->type; | |
1849 | cfi.end = hint->end; | |
1850 | ||
1851 | insn->cfi = cfi_hash_find_or_add(&cfi); | |
1852 | } | |
1853 | ||
1854 | return 0; | |
1855 | } | |
1856 | ||
1857 | static int read_retpoline_hints(struct objtool_file *file) | |
1858 | { | |
1859 | struct section *sec; | |
1860 | struct instruction *insn; | |
1861 | struct reloc *reloc; | |
1862 | ||
1863 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); | |
1864 | if (!sec) | |
1865 | return 0; | |
1866 | ||
1867 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
1868 | if (reloc->sym->type != STT_SECTION) { | |
1869 | WARN("unexpected relocation symbol type in %s", sec->name); | |
1870 | return -1; | |
1871 | } | |
1872 | ||
1873 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1874 | if (!insn) { | |
1875 | WARN("bad .discard.retpoline_safe entry"); | |
1876 | return -1; | |
1877 | } | |
1878 | ||
1879 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1880 | insn->type != INSN_CALL_DYNAMIC) { | |
1881 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", | |
1882 | insn->sec, insn->offset); | |
1883 | return -1; | |
1884 | } | |
1885 | ||
1886 | insn->retpoline_safe = true; | |
1887 | } | |
1888 | ||
1889 | return 0; | |
1890 | } | |
1891 | ||
1892 | static int read_instr_hints(struct objtool_file *file) | |
1893 | { | |
1894 | struct section *sec; | |
1895 | struct instruction *insn; | |
1896 | struct reloc *reloc; | |
1897 | ||
1898 | sec = find_section_by_name(file->elf, ".rela.discard.instr_end"); | |
1899 | if (!sec) | |
1900 | return 0; | |
1901 | ||
1902 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
1903 | if (reloc->sym->type != STT_SECTION) { | |
1904 | WARN("unexpected relocation symbol type in %s", sec->name); | |
1905 | return -1; | |
1906 | } | |
1907 | ||
1908 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1909 | if (!insn) { | |
1910 | WARN("bad .discard.instr_end entry"); | |
1911 | return -1; | |
1912 | } | |
1913 | ||
1914 | insn->instr--; | |
1915 | } | |
1916 | ||
1917 | sec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); | |
1918 | if (!sec) | |
1919 | return 0; | |
1920 | ||
1921 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
1922 | if (reloc->sym->type != STT_SECTION) { | |
1923 | WARN("unexpected relocation symbol type in %s", sec->name); | |
1924 | return -1; | |
1925 | } | |
1926 | ||
1927 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1928 | if (!insn) { | |
1929 | WARN("bad .discard.instr_begin entry"); | |
1930 | return -1; | |
1931 | } | |
1932 | ||
1933 | insn->instr++; | |
1934 | } | |
1935 | ||
1936 | return 0; | |
1937 | } | |
1938 | ||
1939 | static int read_intra_function_calls(struct objtool_file *file) | |
1940 | { | |
1941 | struct instruction *insn; | |
1942 | struct section *sec; | |
1943 | struct reloc *reloc; | |
1944 | ||
1945 | sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); | |
1946 | if (!sec) | |
1947 | return 0; | |
1948 | ||
1949 | list_for_each_entry(reloc, &sec->reloc_list, list) { | |
1950 | unsigned long dest_off; | |
1951 | ||
1952 | if (reloc->sym->type != STT_SECTION) { | |
1953 | WARN("unexpected relocation symbol type in %s", | |
1954 | sec->name); | |
1955 | return -1; | |
1956 | } | |
1957 | ||
1958 | insn = find_insn(file, reloc->sym->sec, reloc->addend); | |
1959 | if (!insn) { | |
1960 | WARN("bad .discard.intra_function_call entry"); | |
1961 | return -1; | |
1962 | } | |
1963 | ||
1964 | if (insn->type != INSN_CALL) { | |
1965 | WARN_FUNC("intra_function_call not a direct call", | |
1966 | insn->sec, insn->offset); | |
1967 | return -1; | |
1968 | } | |
1969 | ||
1970 | /* | |
1971 | * Treat intra-function CALLs as JMPs, but with a stack_op. | |
1972 | * See add_call_destinations(), which strips stack_ops from | |
1973 | * normal CALLs. | |
1974 | */ | |
1975 | insn->type = INSN_JUMP_UNCONDITIONAL; | |
1976 | ||
1977 | dest_off = insn->offset + insn->len + insn->immediate; | |
1978 | insn->jump_dest = find_insn(file, insn->sec, dest_off); | |
1979 | if (!insn->jump_dest) { | |
1980 | WARN_FUNC("can't find call dest at %s+0x%lx", | |
1981 | insn->sec, insn->offset, | |
1982 | insn->sec->name, dest_off); | |
1983 | return -1; | |
1984 | } | |
1985 | } | |
1986 | ||
1987 | return 0; | |
1988 | } | |
1989 | ||
1990 | static int classify_symbols(struct objtool_file *file) | |
1991 | { | |
1992 | struct section *sec; | |
1993 | struct symbol *func; | |
1994 | ||
1995 | for_each_sec(file, sec) { | |
1996 | list_for_each_entry(func, &sec->symbol_list, list) { | |
1997 | if (func->bind != STB_GLOBAL) | |
1998 | continue; | |
1999 | ||
2000 | if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR, | |
2001 | strlen(STATIC_CALL_TRAMP_PREFIX_STR))) | |
2002 | func->static_call_tramp = true; | |
2003 | ||
2004 | if (arch_is_retpoline(func)) | |
2005 | func->retpoline_thunk = true; | |
2006 | ||
2007 | if (arch_is_rethunk(func)) | |
2008 | func->return_thunk = true; | |
2009 | ||
2010 | if (!strcmp(func->name, "__fentry__")) | |
2011 | func->fentry = true; | |
2012 | ||
2013 | if (!strncmp(func->name, "__sanitizer_cov_", 16)) | |
2014 | func->kcov = true; | |
2015 | } | |
2016 | } | |
2017 | ||
2018 | return 0; | |
2019 | } | |
2020 | ||
2021 | static void mark_rodata(struct objtool_file *file) | |
2022 | { | |
2023 | struct section *sec; | |
2024 | bool found = false; | |
2025 | ||
2026 | /* | |
2027 | * Search for the following rodata sections, each of which can | |
2028 | * potentially contain jump tables: | |
2029 | * | |
2030 | * - .rodata: can contain GCC switch tables | |
2031 | * - .rodata.<func>: same, if -fdata-sections is being used | |
2032 | * - .rodata..c_jump_table: contains C annotated jump tables | |
2033 | * | |
2034 | * .rodata.str1.* sections are ignored; they don't contain jump tables. | |
2035 | */ | |
2036 | for_each_sec(file, sec) { | |
2037 | if (!strncmp(sec->name, ".rodata", 7) && | |
2038 | !strstr(sec->name, ".str1.")) { | |
2039 | sec->rodata = true; | |
2040 | found = true; | |
2041 | } | |
2042 | } | |
2043 | ||
2044 | file->rodata = found; | |
2045 | } | |
2046 | ||
2047 | static int decode_sections(struct objtool_file *file) | |
2048 | { | |
2049 | int ret; | |
2050 | ||
2051 | mark_rodata(file); | |
2052 | ||
2053 | ret = decode_instructions(file); | |
2054 | if (ret) | |
2055 | return ret; | |
2056 | ||
2057 | ret = add_dead_ends(file); | |
2058 | if (ret) | |
2059 | return ret; | |
2060 | ||
2061 | add_ignores(file); | |
2062 | add_uaccess_safe(file); | |
2063 | ||
2064 | ret = add_ignore_alternatives(file); | |
2065 | if (ret) | |
2066 | return ret; | |
2067 | ||
2068 | /* | |
2069 | * Must be before add_{jump_call}_destination. | |
2070 | */ | |
2071 | ret = classify_symbols(file); | |
2072 | if (ret) | |
2073 | return ret; | |
2074 | ||
2075 | /* | |
2076 | * Must be before add_special_section_alts() as that depends on | |
2077 | * jump_dest being set. | |
2078 | */ | |
2079 | ret = add_jump_destinations(file); | |
2080 | if (ret) | |
2081 | return ret; | |
2082 | ||
2083 | ret = add_special_section_alts(file); | |
2084 | if (ret) | |
2085 | return ret; | |
2086 | ||
2087 | /* | |
2088 | * Must be before add_call_destination(); it changes INSN_CALL to | |
2089 | * INSN_JUMP. | |
2090 | */ | |
2091 | ret = read_intra_function_calls(file); | |
2092 | if (ret) | |
2093 | return ret; | |
2094 | ||
2095 | ret = add_call_destinations(file); | |
2096 | if (ret) | |
2097 | return ret; | |
2098 | ||
2099 | ret = add_jump_table_alts(file); | |
2100 | if (ret) | |
2101 | return ret; | |
2102 | ||
2103 | ret = read_unwind_hints(file); | |
2104 | if (ret) | |
2105 | return ret; | |
2106 | ||
2107 | ret = read_retpoline_hints(file); | |
2108 | if (ret) | |
2109 | return ret; | |
2110 | ||
2111 | ret = read_instr_hints(file); | |
2112 | if (ret) | |
2113 | return ret; | |
2114 | ||
2115 | return 0; | |
2116 | } | |
2117 | ||
2118 | static bool is_fentry_call(struct instruction *insn) | |
2119 | { | |
2120 | if (insn->type == INSN_CALL && | |
2121 | insn->call_dest && | |
2122 | insn->call_dest->fentry) | |
2123 | return true; | |
2124 | ||
2125 | return false; | |
2126 | } | |
2127 | ||
2128 | static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) | |
2129 | { | |
2130 | struct cfi_state *cfi = &state->cfi; | |
2131 | int i; | |
2132 | ||
2133 | if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) | |
2134 | return true; | |
2135 | ||
2136 | if (cfi->cfa.offset != initial_func_cfi.cfa.offset) | |
2137 | return true; | |
2138 | ||
2139 | if (cfi->stack_size != initial_func_cfi.cfa.offset) | |
2140 | return true; | |
2141 | ||
2142 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
2143 | if (cfi->regs[i].base != initial_func_cfi.regs[i].base || | |
2144 | cfi->regs[i].offset != initial_func_cfi.regs[i].offset) | |
2145 | return true; | |
2146 | } | |
2147 | ||
2148 | return false; | |
2149 | } | |
2150 | ||
2151 | static bool check_reg_frame_pos(const struct cfi_reg *reg, | |
2152 | int expected_offset) | |
2153 | { | |
2154 | return reg->base == CFI_CFA && | |
2155 | reg->offset == expected_offset; | |
2156 | } | |
2157 | ||
2158 | static bool has_valid_stack_frame(struct insn_state *state) | |
2159 | { | |
2160 | struct cfi_state *cfi = &state->cfi; | |
2161 | ||
2162 | if (cfi->cfa.base == CFI_BP && | |
2163 | check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) && | |
2164 | check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8)) | |
2165 | return true; | |
2166 | ||
2167 | if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP) | |
2168 | return true; | |
2169 | ||
2170 | return false; | |
2171 | } | |
2172 | ||
2173 | static int update_cfi_state_regs(struct instruction *insn, | |
2174 | struct cfi_state *cfi, | |
2175 | struct stack_op *op) | |
2176 | { | |
2177 | struct cfi_reg *cfa = &cfi->cfa; | |
2178 | ||
2179 | if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT) | |
2180 | return 0; | |
2181 | ||
2182 | /* push */ | |
2183 | if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) | |
2184 | cfa->offset += 8; | |
2185 | ||
2186 | /* pop */ | |
2187 | if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) | |
2188 | cfa->offset -= 8; | |
2189 | ||
2190 | /* add immediate to sp */ | |
2191 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
2192 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
2193 | cfa->offset -= op->src.offset; | |
2194 | ||
2195 | return 0; | |
2196 | } | |
2197 | ||
2198 | static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) | |
2199 | { | |
2200 | if (arch_callee_saved_reg(reg) && | |
2201 | cfi->regs[reg].base == CFI_UNDEFINED) { | |
2202 | cfi->regs[reg].base = base; | |
2203 | cfi->regs[reg].offset = offset; | |
2204 | } | |
2205 | } | |
2206 | ||
2207 | static void restore_reg(struct cfi_state *cfi, unsigned char reg) | |
2208 | { | |
2209 | cfi->regs[reg].base = initial_func_cfi.regs[reg].base; | |
2210 | cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset; | |
2211 | } | |
2212 | ||
2213 | /* | |
2214 | * A note about DRAP stack alignment: | |
2215 | * | |
2216 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
2217 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
2218 | * register. The typical DRAP pattern is: | |
2219 | * | |
2220 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
2221 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
2222 | * 41 ff 72 f8 pushq -0x8(%r10) | |
2223 | * 55 push %rbp | |
2224 | * 48 89 e5 mov %rsp,%rbp | |
2225 | * (more pushes) | |
2226 | * 41 52 push %r10 | |
2227 | * ... | |
2228 | * 41 5a pop %r10 | |
2229 | * (more pops) | |
2230 | * 5d pop %rbp | |
2231 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
2232 | * c3 retq | |
2233 | * | |
2234 | * There are some variations in the epilogues, like: | |
2235 | * | |
2236 | * 5b pop %rbx | |
2237 | * 41 5a pop %r10 | |
2238 | * 41 5c pop %r12 | |
2239 | * 41 5d pop %r13 | |
2240 | * 41 5e pop %r14 | |
2241 | * c9 leaveq | |
2242 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
2243 | * c3 retq | |
2244 | * | |
2245 | * and: | |
2246 | * | |
2247 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
2248 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
2249 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
2250 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
2251 | * c9 leaveq | |
2252 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
2253 | * c3 retq | |
2254 | * | |
2255 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
2256 | * restored beforehand: | |
2257 | * | |
2258 | * 41 55 push %r13 | |
2259 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
2260 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
2261 | * ... | |
2262 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
2263 | * 41 5d pop %r13 | |
2264 | * c3 retq | |
2265 | */ | |
2266 | static int update_cfi_state(struct instruction *insn, | |
2267 | struct instruction *next_insn, | |
2268 | struct cfi_state *cfi, struct stack_op *op) | |
2269 | { | |
2270 | struct cfi_reg *cfa = &cfi->cfa; | |
2271 | struct cfi_reg *regs = cfi->regs; | |
2272 | ||
2273 | /* stack operations don't make sense with an undefined CFA */ | |
2274 | if (cfa->base == CFI_UNDEFINED) { | |
2275 | if (insn->func) { | |
2276 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
2277 | return -1; | |
2278 | } | |
2279 | return 0; | |
2280 | } | |
2281 | ||
2282 | if (cfi->type == UNWIND_HINT_TYPE_REGS || | |
2283 | cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL) | |
2284 | return update_cfi_state_regs(insn, cfi, op); | |
2285 | ||
2286 | switch (op->dest.type) { | |
2287 | ||
2288 | case OP_DEST_REG: | |
2289 | switch (op->src.type) { | |
2290 | ||
2291 | case OP_SRC_REG: | |
2292 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && | |
2293 | cfa->base == CFI_SP && | |
2294 | check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) { | |
2295 | ||
2296 | /* mov %rsp, %rbp */ | |
2297 | cfa->base = op->dest.reg; | |
2298 | cfi->bp_scratch = false; | |
2299 | } | |
2300 | ||
2301 | else if (op->src.reg == CFI_SP && | |
2302 | op->dest.reg == CFI_BP && cfi->drap) { | |
2303 | ||
2304 | /* drap: mov %rsp, %rbp */ | |
2305 | regs[CFI_BP].base = CFI_BP; | |
2306 | regs[CFI_BP].offset = -cfi->stack_size; | |
2307 | cfi->bp_scratch = false; | |
2308 | } | |
2309 | ||
2310 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { | |
2311 | ||
2312 | /* | |
2313 | * mov %rsp, %reg | |
2314 | * | |
2315 | * This is needed for the rare case where GCC | |
2316 | * does: | |
2317 | * | |
2318 | * mov %rsp, %rax | |
2319 | * ... | |
2320 | * mov %rax, %rsp | |
2321 | */ | |
2322 | cfi->vals[op->dest.reg].base = CFI_CFA; | |
2323 | cfi->vals[op->dest.reg].offset = -cfi->stack_size; | |
2324 | } | |
2325 | ||
2326 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && | |
2327 | (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) { | |
2328 | ||
2329 | /* | |
2330 | * mov %rbp, %rsp | |
2331 | * | |
2332 | * Restore the original stack pointer (Clang). | |
2333 | */ | |
2334 | cfi->stack_size = -cfi->regs[CFI_BP].offset; | |
2335 | } | |
2336 | ||
2337 | else if (op->dest.reg == cfa->base) { | |
2338 | ||
2339 | /* mov %reg, %rsp */ | |
2340 | if (cfa->base == CFI_SP && | |
2341 | cfi->vals[op->src.reg].base == CFI_CFA) { | |
2342 | ||
2343 | /* | |
2344 | * This is needed for the rare case | |
2345 | * where GCC does something dumb like: | |
2346 | * | |
2347 | * lea 0x8(%rsp), %rcx | |
2348 | * ... | |
2349 | * mov %rcx, %rsp | |
2350 | */ | |
2351 | cfa->offset = -cfi->vals[op->src.reg].offset; | |
2352 | cfi->stack_size = cfa->offset; | |
2353 | ||
2354 | } else if (cfa->base == CFI_SP && | |
2355 | cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && | |
2356 | cfi->vals[op->src.reg].offset == cfa->offset) { | |
2357 | ||
2358 | /* | |
2359 | * Stack swizzle: | |
2360 | * | |
2361 | * 1: mov %rsp, (%[tos]) | |
2362 | * 2: mov %[tos], %rsp | |
2363 | * ... | |
2364 | * 3: pop %rsp | |
2365 | * | |
2366 | * Where: | |
2367 | * | |
2368 | * 1 - places a pointer to the previous | |
2369 | * stack at the Top-of-Stack of the | |
2370 | * new stack. | |
2371 | * | |
2372 | * 2 - switches to the new stack. | |
2373 | * | |
2374 | * 3 - pops the Top-of-Stack to restore | |
2375 | * the original stack. | |
2376 | * | |
2377 | * Note: we set base to SP_INDIRECT | |
2378 | * here and preserve offset. Therefore | |
2379 | * when the unwinder reaches ToS it | |
2380 | * will dereference SP and then add the | |
2381 | * offset to find the next frame, IOW: | |
2382 | * (%rsp) + offset. | |
2383 | */ | |
2384 | cfa->base = CFI_SP_INDIRECT; | |
2385 | ||
2386 | } else { | |
2387 | cfa->base = CFI_UNDEFINED; | |
2388 | cfa->offset = 0; | |
2389 | } | |
2390 | } | |
2391 | ||
2392 | else if (op->dest.reg == CFI_SP && | |
2393 | cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && | |
2394 | cfi->vals[op->src.reg].offset == cfa->offset) { | |
2395 | ||
2396 | /* | |
2397 | * The same stack swizzle case 2) as above. But | |
2398 | * because we can't change cfa->base, case 3) | |
2399 | * will become a regular POP. Pretend we're a | |
2400 | * PUSH so things don't go unbalanced. | |
2401 | */ | |
2402 | cfi->stack_size += 8; | |
2403 | } | |
2404 | ||
2405 | ||
2406 | break; | |
2407 | ||
2408 | case OP_SRC_ADD: | |
2409 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
2410 | ||
2411 | /* add imm, %rsp */ | |
2412 | cfi->stack_size -= op->src.offset; | |
2413 | if (cfa->base == CFI_SP) | |
2414 | cfa->offset -= op->src.offset; | |
2415 | break; | |
2416 | } | |
2417 | ||
2418 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
2419 | ||
2420 | /* lea disp(%rbp), %rsp */ | |
2421 | cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
2422 | break; | |
2423 | } | |
2424 | ||
2425 | if (!cfi->drap && op->src.reg == CFI_SP && | |
2426 | op->dest.reg == CFI_BP && cfa->base == CFI_SP && | |
2427 | check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) { | |
2428 | ||
2429 | /* lea disp(%rsp), %rbp */ | |
2430 | cfa->base = CFI_BP; | |
2431 | cfa->offset -= op->src.offset; | |
2432 | cfi->bp_scratch = false; | |
2433 | break; | |
2434 | } | |
2435 | ||
2436 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { | |
2437 | ||
2438 | /* drap: lea disp(%rsp), %drap */ | |
2439 | cfi->drap_reg = op->dest.reg; | |
2440 | ||
2441 | /* | |
2442 | * lea disp(%rsp), %reg | |
2443 | * | |
2444 | * This is needed for the rare case where GCC | |
2445 | * does something dumb like: | |
2446 | * | |
2447 | * lea 0x8(%rsp), %rcx | |
2448 | * ... | |
2449 | * mov %rcx, %rsp | |
2450 | */ | |
2451 | cfi->vals[op->dest.reg].base = CFI_CFA; | |
2452 | cfi->vals[op->dest.reg].offset = \ | |
2453 | -cfi->stack_size + op->src.offset; | |
2454 | ||
2455 | break; | |
2456 | } | |
2457 | ||
2458 | if (cfi->drap && op->dest.reg == CFI_SP && | |
2459 | op->src.reg == cfi->drap_reg) { | |
2460 | ||
2461 | /* drap: lea disp(%drap), %rsp */ | |
2462 | cfa->base = CFI_SP; | |
2463 | cfa->offset = cfi->stack_size = -op->src.offset; | |
2464 | cfi->drap_reg = CFI_UNDEFINED; | |
2465 | cfi->drap = false; | |
2466 | break; | |
2467 | } | |
2468 | ||
2469 | if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { | |
2470 | WARN_FUNC("unsupported stack register modification", | |
2471 | insn->sec, insn->offset); | |
2472 | return -1; | |
2473 | } | |
2474 | ||
2475 | break; | |
2476 | ||
2477 | case OP_SRC_AND: | |
2478 | if (op->dest.reg != CFI_SP || | |
2479 | (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
2480 | (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
2481 | WARN_FUNC("unsupported stack pointer realignment", | |
2482 | insn->sec, insn->offset); | |
2483 | return -1; | |
2484 | } | |
2485 | ||
2486 | if (cfi->drap_reg != CFI_UNDEFINED) { | |
2487 | /* drap: and imm, %rsp */ | |
2488 | cfa->base = cfi->drap_reg; | |
2489 | cfa->offset = cfi->stack_size = 0; | |
2490 | cfi->drap = true; | |
2491 | } | |
2492 | ||
2493 | /* | |
2494 | * Older versions of GCC (4.8ish) realign the stack | |
2495 | * without DRAP, with a frame pointer. | |
2496 | */ | |
2497 | ||
2498 | break; | |
2499 | ||
2500 | case OP_SRC_POP: | |
2501 | case OP_SRC_POPF: | |
2502 | if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) { | |
2503 | ||
2504 | /* pop %rsp; # restore from a stack swizzle */ | |
2505 | cfa->base = CFI_SP; | |
2506 | break; | |
2507 | } | |
2508 | ||
2509 | if (!cfi->drap && op->dest.reg == cfa->base) { | |
2510 | ||
2511 | /* pop %rbp */ | |
2512 | cfa->base = CFI_SP; | |
2513 | } | |
2514 | ||
2515 | if (cfi->drap && cfa->base == CFI_BP_INDIRECT && | |
2516 | op->dest.reg == cfi->drap_reg && | |
2517 | cfi->drap_offset == -cfi->stack_size) { | |
2518 | ||
2519 | /* drap: pop %drap */ | |
2520 | cfa->base = cfi->drap_reg; | |
2521 | cfa->offset = 0; | |
2522 | cfi->drap_offset = -1; | |
2523 | ||
2524 | } else if (cfi->stack_size == -regs[op->dest.reg].offset) { | |
2525 | ||
2526 | /* pop %reg */ | |
2527 | restore_reg(cfi, op->dest.reg); | |
2528 | } | |
2529 | ||
2530 | cfi->stack_size -= 8; | |
2531 | if (cfa->base == CFI_SP) | |
2532 | cfa->offset -= 8; | |
2533 | ||
2534 | break; | |
2535 | ||
2536 | case OP_SRC_REG_INDIRECT: | |
2537 | if (!cfi->drap && op->dest.reg == cfa->base && | |
2538 | op->dest.reg == CFI_BP) { | |
2539 | ||
2540 | /* mov disp(%rsp), %rbp */ | |
2541 | cfa->base = CFI_SP; | |
2542 | cfa->offset = cfi->stack_size; | |
2543 | } | |
2544 | ||
2545 | if (cfi->drap && op->src.reg == CFI_BP && | |
2546 | op->src.offset == cfi->drap_offset) { | |
2547 | ||
2548 | /* drap: mov disp(%rbp), %drap */ | |
2549 | cfa->base = cfi->drap_reg; | |
2550 | cfa->offset = 0; | |
2551 | cfi->drap_offset = -1; | |
2552 | } | |
2553 | ||
2554 | if (cfi->drap && op->src.reg == CFI_BP && | |
2555 | op->src.offset == regs[op->dest.reg].offset) { | |
2556 | ||
2557 | /* drap: mov disp(%rbp), %reg */ | |
2558 | restore_reg(cfi, op->dest.reg); | |
2559 | ||
2560 | } else if (op->src.reg == cfa->base && | |
2561 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
2562 | ||
2563 | /* mov disp(%rbp), %reg */ | |
2564 | /* mov disp(%rsp), %reg */ | |
2565 | restore_reg(cfi, op->dest.reg); | |
2566 | ||
2567 | } else if (op->src.reg == CFI_SP && | |
2568 | op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) { | |
2569 | ||
2570 | /* mov disp(%rsp), %reg */ | |
2571 | restore_reg(cfi, op->dest.reg); | |
2572 | } | |
2573 | ||
2574 | break; | |
2575 | ||
2576 | default: | |
2577 | WARN_FUNC("unknown stack-related instruction", | |
2578 | insn->sec, insn->offset); | |
2579 | return -1; | |
2580 | } | |
2581 | ||
2582 | break; | |
2583 | ||
2584 | case OP_DEST_PUSH: | |
2585 | case OP_DEST_PUSHF: | |
2586 | cfi->stack_size += 8; | |
2587 | if (cfa->base == CFI_SP) | |
2588 | cfa->offset += 8; | |
2589 | ||
2590 | if (op->src.type != OP_SRC_REG) | |
2591 | break; | |
2592 | ||
2593 | if (cfi->drap) { | |
2594 | if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { | |
2595 | ||
2596 | /* drap: push %drap */ | |
2597 | cfa->base = CFI_BP_INDIRECT; | |
2598 | cfa->offset = -cfi->stack_size; | |
2599 | ||
2600 | /* save drap so we know when to restore it */ | |
2601 | cfi->drap_offset = -cfi->stack_size; | |
2602 | ||
2603 | } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) { | |
2604 | ||
2605 | /* drap: push %rbp */ | |
2606 | cfi->stack_size = 0; | |
2607 | ||
2608 | } else { | |
2609 | ||
2610 | /* drap: push %reg */ | |
2611 | save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size); | |
2612 | } | |
2613 | ||
2614 | } else { | |
2615 | ||
2616 | /* push %reg */ | |
2617 | save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size); | |
2618 | } | |
2619 | ||
2620 | /* detect when asm code uses rbp as a scratch register */ | |
2621 | if (!no_fp && insn->func && op->src.reg == CFI_BP && | |
2622 | cfa->base != CFI_BP) | |
2623 | cfi->bp_scratch = true; | |
2624 | break; | |
2625 | ||
2626 | case OP_DEST_REG_INDIRECT: | |
2627 | ||
2628 | if (cfi->drap) { | |
2629 | if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { | |
2630 | ||
2631 | /* drap: mov %drap, disp(%rbp) */ | |
2632 | cfa->base = CFI_BP_INDIRECT; | |
2633 | cfa->offset = op->dest.offset; | |
2634 | ||
2635 | /* save drap offset so we know when to restore it */ | |
2636 | cfi->drap_offset = op->dest.offset; | |
2637 | } else { | |
2638 | ||
2639 | /* drap: mov reg, disp(%rbp) */ | |
2640 | save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset); | |
2641 | } | |
2642 | ||
2643 | } else if (op->dest.reg == cfa->base) { | |
2644 | ||
2645 | /* mov reg, disp(%rbp) */ | |
2646 | /* mov reg, disp(%rsp) */ | |
2647 | save_reg(cfi, op->src.reg, CFI_CFA, | |
2648 | op->dest.offset - cfi->cfa.offset); | |
2649 | ||
2650 | } else if (op->dest.reg == CFI_SP) { | |
2651 | ||
2652 | /* mov reg, disp(%rsp) */ | |
2653 | save_reg(cfi, op->src.reg, CFI_CFA, | |
2654 | op->dest.offset - cfi->stack_size); | |
2655 | ||
2656 | } else if (op->src.reg == CFI_SP && op->dest.offset == 0) { | |
2657 | ||
2658 | /* mov %rsp, (%reg); # setup a stack swizzle. */ | |
2659 | cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT; | |
2660 | cfi->vals[op->dest.reg].offset = cfa->offset; | |
2661 | } | |
2662 | ||
2663 | break; | |
2664 | ||
2665 | case OP_DEST_MEM: | |
2666 | if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { | |
2667 | WARN_FUNC("unknown stack-related memory operation", | |
2668 | insn->sec, insn->offset); | |
2669 | return -1; | |
2670 | } | |
2671 | ||
2672 | /* pop mem */ | |
2673 | cfi->stack_size -= 8; | |
2674 | if (cfa->base == CFI_SP) | |
2675 | cfa->offset -= 8; | |
2676 | ||
2677 | break; | |
2678 | ||
2679 | default: | |
2680 | WARN_FUNC("unknown stack-related instruction", | |
2681 | insn->sec, insn->offset); | |
2682 | return -1; | |
2683 | } | |
2684 | ||
2685 | return 0; | |
2686 | } | |
2687 | ||
2688 | /* | |
2689 | * The stack layouts of alternatives instructions can sometimes diverge when | |
2690 | * they have stack modifications. That's fine as long as the potential stack | |
2691 | * layouts don't conflict at any given potential instruction boundary. | |
2692 | * | |
2693 | * Flatten the CFIs of the different alternative code streams (both original | |
2694 | * and replacement) into a single shared CFI array which can be used to detect | |
2695 | * conflicts and nicely feed a linear array of ORC entries to the unwinder. | |
2696 | */ | |
2697 | static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn) | |
2698 | { | |
2699 | struct cfi_state **alt_cfi; | |
2700 | int group_off; | |
2701 | ||
2702 | if (!insn->alt_group) | |
2703 | return 0; | |
2704 | ||
2705 | if (!insn->cfi) { | |
2706 | WARN("CFI missing"); | |
2707 | return -1; | |
2708 | } | |
2709 | ||
2710 | alt_cfi = insn->alt_group->cfi; | |
2711 | group_off = insn->offset - insn->alt_group->first_insn->offset; | |
2712 | ||
2713 | if (!alt_cfi[group_off]) { | |
2714 | alt_cfi[group_off] = insn->cfi; | |
2715 | } else { | |
2716 | if (cficmp(alt_cfi[group_off], insn->cfi)) { | |
2717 | WARN_FUNC("stack layout conflict in alternatives", | |
2718 | insn->sec, insn->offset); | |
2719 | return -1; | |
2720 | } | |
2721 | } | |
2722 | ||
2723 | return 0; | |
2724 | } | |
2725 | ||
2726 | static int handle_insn_ops(struct instruction *insn, | |
2727 | struct instruction *next_insn, | |
2728 | struct insn_state *state) | |
2729 | { | |
2730 | struct stack_op *op; | |
2731 | ||
2732 | list_for_each_entry(op, &insn->stack_ops, list) { | |
2733 | ||
2734 | if (update_cfi_state(insn, next_insn, &state->cfi, op)) | |
2735 | return 1; | |
2736 | ||
2737 | if (!insn->alt_group) | |
2738 | continue; | |
2739 | ||
2740 | if (op->dest.type == OP_DEST_PUSHF) { | |
2741 | if (!state->uaccess_stack) { | |
2742 | state->uaccess_stack = 1; | |
2743 | } else if (state->uaccess_stack >> 31) { | |
2744 | WARN_FUNC("PUSHF stack exhausted", | |
2745 | insn->sec, insn->offset); | |
2746 | return 1; | |
2747 | } | |
2748 | state->uaccess_stack <<= 1; | |
2749 | state->uaccess_stack |= state->uaccess; | |
2750 | } | |
2751 | ||
2752 | if (op->src.type == OP_SRC_POPF) { | |
2753 | if (state->uaccess_stack) { | |
2754 | state->uaccess = state->uaccess_stack & 1; | |
2755 | state->uaccess_stack >>= 1; | |
2756 | if (state->uaccess_stack == 1) | |
2757 | state->uaccess_stack = 0; | |
2758 | } | |
2759 | } | |
2760 | } | |
2761 | ||
2762 | return 0; | |
2763 | } | |
2764 | ||
2765 | static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) | |
2766 | { | |
2767 | struct cfi_state *cfi1 = insn->cfi; | |
2768 | int i; | |
2769 | ||
2770 | if (!cfi1) { | |
2771 | WARN("CFI missing"); | |
2772 | return false; | |
2773 | } | |
2774 | ||
2775 | if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) { | |
2776 | ||
2777 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
2778 | insn->sec, insn->offset, | |
2779 | cfi1->cfa.base, cfi1->cfa.offset, | |
2780 | cfi2->cfa.base, cfi2->cfa.offset); | |
2781 | ||
2782 | } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) { | |
2783 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
2784 | if (!memcmp(&cfi1->regs[i], &cfi2->regs[i], | |
2785 | sizeof(struct cfi_reg))) | |
2786 | continue; | |
2787 | ||
2788 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
2789 | insn->sec, insn->offset, | |
2790 | i, cfi1->regs[i].base, cfi1->regs[i].offset, | |
2791 | i, cfi2->regs[i].base, cfi2->regs[i].offset); | |
2792 | break; | |
2793 | } | |
2794 | ||
2795 | } else if (cfi1->type != cfi2->type) { | |
2796 | ||
2797 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
2798 | insn->sec, insn->offset, cfi1->type, cfi2->type); | |
2799 | ||
2800 | } else if (cfi1->drap != cfi2->drap || | |
2801 | (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) || | |
2802 | (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) { | |
2803 | ||
2804 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
2805 | insn->sec, insn->offset, | |
2806 | cfi1->drap, cfi1->drap_reg, cfi1->drap_offset, | |
2807 | cfi2->drap, cfi2->drap_reg, cfi2->drap_offset); | |
2808 | ||
2809 | } else | |
2810 | return true; | |
2811 | ||
2812 | return false; | |
2813 | } | |
2814 | ||
2815 | static inline bool func_uaccess_safe(struct symbol *func) | |
2816 | { | |
2817 | if (func) | |
2818 | return func->uaccess_safe; | |
2819 | ||
2820 | return false; | |
2821 | } | |
2822 | ||
2823 | static inline const char *call_dest_name(struct instruction *insn) | |
2824 | { | |
2825 | if (insn->call_dest) | |
2826 | return insn->call_dest->name; | |
2827 | ||
2828 | return "{dynamic}"; | |
2829 | } | |
2830 | ||
2831 | static inline bool noinstr_call_dest(struct symbol *func) | |
2832 | { | |
2833 | /* | |
2834 | * We can't deal with indirect function calls at present; | |
2835 | * assume they're instrumented. | |
2836 | */ | |
2837 | if (!func) | |
2838 | return false; | |
2839 | ||
2840 | /* | |
2841 | * If the symbol is from a noinstr section; we good. | |
2842 | */ | |
2843 | if (func->sec->noinstr) | |
2844 | return true; | |
2845 | ||
2846 | /* | |
2847 | * The __ubsan_handle_*() calls are like WARN(), they only happen when | |
2848 | * something 'BAD' happened. At the risk of taking the machine down, | |
2849 | * let them proceed to get the message out. | |
2850 | */ | |
2851 | if (!strncmp(func->name, "__ubsan_handle_", 15)) | |
2852 | return true; | |
2853 | ||
2854 | return false; | |
2855 | } | |
2856 | ||
2857 | static int validate_call(struct instruction *insn, struct insn_state *state) | |
2858 | { | |
2859 | if (state->noinstr && state->instr <= 0 && | |
2860 | !noinstr_call_dest(insn->call_dest)) { | |
2861 | WARN_FUNC("call to %s() leaves .noinstr.text section", | |
2862 | insn->sec, insn->offset, call_dest_name(insn)); | |
2863 | return 1; | |
2864 | } | |
2865 | ||
2866 | if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { | |
2867 | WARN_FUNC("call to %s() with UACCESS enabled", | |
2868 | insn->sec, insn->offset, call_dest_name(insn)); | |
2869 | return 1; | |
2870 | } | |
2871 | ||
2872 | if (state->df) { | |
2873 | WARN_FUNC("call to %s() with DF set", | |
2874 | insn->sec, insn->offset, call_dest_name(insn)); | |
2875 | return 1; | |
2876 | } | |
2877 | ||
2878 | return 0; | |
2879 | } | |
2880 | ||
2881 | static int validate_sibling_call(struct instruction *insn, struct insn_state *state) | |
2882 | { | |
2883 | if (has_modified_stack_frame(insn, state)) { | |
2884 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
2885 | insn->sec, insn->offset); | |
2886 | return 1; | |
2887 | } | |
2888 | ||
2889 | return validate_call(insn, state); | |
2890 | } | |
2891 | ||
2892 | static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) | |
2893 | { | |
2894 | if (state->noinstr && state->instr > 0) { | |
2895 | WARN_FUNC("return with instrumentation enabled", | |
2896 | insn->sec, insn->offset); | |
2897 | return 1; | |
2898 | } | |
2899 | ||
2900 | if (state->uaccess && !func_uaccess_safe(func)) { | |
2901 | WARN_FUNC("return with UACCESS enabled", | |
2902 | insn->sec, insn->offset); | |
2903 | return 1; | |
2904 | } | |
2905 | ||
2906 | if (!state->uaccess && func_uaccess_safe(func)) { | |
2907 | WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", | |
2908 | insn->sec, insn->offset); | |
2909 | return 1; | |
2910 | } | |
2911 | ||
2912 | if (state->df) { | |
2913 | WARN_FUNC("return with DF set", | |
2914 | insn->sec, insn->offset); | |
2915 | return 1; | |
2916 | } | |
2917 | ||
2918 | if (func && has_modified_stack_frame(insn, state)) { | |
2919 | WARN_FUNC("return with modified stack frame", | |
2920 | insn->sec, insn->offset); | |
2921 | return 1; | |
2922 | } | |
2923 | ||
2924 | if (state->cfi.bp_scratch) { | |
2925 | WARN_FUNC("BP used as a scratch register", | |
2926 | insn->sec, insn->offset); | |
2927 | return 1; | |
2928 | } | |
2929 | ||
2930 | return 0; | |
2931 | } | |
2932 | ||
2933 | static struct instruction *next_insn_to_validate(struct objtool_file *file, | |
2934 | struct instruction *insn) | |
2935 | { | |
2936 | struct alt_group *alt_group = insn->alt_group; | |
2937 | ||
2938 | /* | |
2939 | * Simulate the fact that alternatives are patched in-place. When the | |
2940 | * end of a replacement alt_group is reached, redirect objtool flow to | |
2941 | * the end of the original alt_group. | |
2942 | */ | |
2943 | if (alt_group && insn == alt_group->last_insn && alt_group->orig_group) | |
2944 | return next_insn_same_sec(file, alt_group->orig_group->last_insn); | |
2945 | ||
2946 | return next_insn_same_sec(file, insn); | |
2947 | } | |
2948 | ||
2949 | /* | |
2950 | * Follow the branch starting at the given instruction, and recursively follow | |
2951 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
2952 | * each instruction and validate all the rules described in | |
2953 | * tools/objtool/Documentation/stack-validation.txt. | |
2954 | */ | |
2955 | static int validate_branch(struct objtool_file *file, struct symbol *func, | |
2956 | struct instruction *insn, struct insn_state state) | |
2957 | { | |
2958 | struct alternative *alt; | |
2959 | struct instruction *next_insn, *prev_insn = NULL; | |
2960 | struct section *sec; | |
2961 | u8 visited; | |
2962 | int ret; | |
2963 | ||
2964 | sec = insn->sec; | |
2965 | ||
2966 | while (1) { | |
2967 | next_insn = next_insn_to_validate(file, insn); | |
2968 | ||
2969 | if (file->c_file && func && insn->func && func != insn->func->pfunc) { | |
2970 | WARN("%s() falls through to next function %s()", | |
2971 | func->name, insn->func->name); | |
2972 | return 1; | |
2973 | } | |
2974 | ||
2975 | if (func && insn->ignore) { | |
2976 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
2977 | sec, insn->offset); | |
2978 | return 1; | |
2979 | } | |
2980 | ||
2981 | visited = 1 << state.uaccess; | |
2982 | if (insn->visited) { | |
2983 | if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) | |
2984 | return 1; | |
2985 | ||
2986 | if (insn->visited & visited) | |
2987 | return 0; | |
2988 | } else { | |
2989 | nr_insns_visited++; | |
2990 | } | |
2991 | ||
2992 | if (state.noinstr) | |
2993 | state.instr += insn->instr; | |
2994 | ||
2995 | if (insn->hint) { | |
2996 | state.cfi = *insn->cfi; | |
2997 | } else { | |
2998 | /* XXX track if we actually changed state.cfi */ | |
2999 | ||
3000 | if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) { | |
3001 | insn->cfi = prev_insn->cfi; | |
3002 | nr_cfi_reused++; | |
3003 | } else { | |
3004 | insn->cfi = cfi_hash_find_or_add(&state.cfi); | |
3005 | } | |
3006 | } | |
3007 | ||
3008 | insn->visited |= visited; | |
3009 | ||
3010 | if (propagate_alt_cfi(file, insn)) | |
3011 | return 1; | |
3012 | ||
3013 | if (!insn->ignore_alts && !list_empty(&insn->alts)) { | |
3014 | bool skip_orig = false; | |
3015 | ||
3016 | list_for_each_entry(alt, &insn->alts, list) { | |
3017 | if (alt->skip_orig) | |
3018 | skip_orig = true; | |
3019 | ||
3020 | ret = validate_branch(file, func, alt->insn, state); | |
3021 | if (ret) { | |
3022 | if (backtrace) | |
3023 | BT_FUNC("(alt)", insn); | |
3024 | return ret; | |
3025 | } | |
3026 | } | |
3027 | ||
3028 | if (skip_orig) | |
3029 | return 0; | |
3030 | } | |
3031 | ||
3032 | if (handle_insn_ops(insn, next_insn, &state)) | |
3033 | return 1; | |
3034 | ||
3035 | switch (insn->type) { | |
3036 | ||
3037 | case INSN_RETURN: | |
3038 | if (sls && !insn->retpoline_safe && | |
3039 | next_insn && next_insn->type != INSN_TRAP) { | |
3040 | WARN_FUNC("missing int3 after ret", | |
3041 | insn->sec, insn->offset); | |
3042 | } | |
3043 | return validate_return(func, insn, &state); | |
3044 | ||
3045 | case INSN_CALL: | |
3046 | case INSN_CALL_DYNAMIC: | |
3047 | ret = validate_call(insn, &state); | |
3048 | if (ret) | |
3049 | return ret; | |
3050 | ||
3051 | if (!no_fp && func && !is_fentry_call(insn) && | |
3052 | !has_valid_stack_frame(&state)) { | |
3053 | WARN_FUNC("call without frame pointer save/setup", | |
3054 | sec, insn->offset); | |
3055 | return 1; | |
3056 | } | |
3057 | ||
3058 | if (dead_end_function(file, insn->call_dest)) | |
3059 | return 0; | |
3060 | ||
3061 | break; | |
3062 | ||
3063 | case INSN_JUMP_CONDITIONAL: | |
3064 | case INSN_JUMP_UNCONDITIONAL: | |
3065 | if (is_sibling_call(insn)) { | |
3066 | ret = validate_sibling_call(insn, &state); | |
3067 | if (ret) | |
3068 | return ret; | |
3069 | ||
3070 | } else if (insn->jump_dest) { | |
3071 | ret = validate_branch(file, func, | |
3072 | insn->jump_dest, state); | |
3073 | if (ret) { | |
3074 | if (backtrace) | |
3075 | BT_FUNC("(branch)", insn); | |
3076 | return ret; | |
3077 | } | |
3078 | } | |
3079 | ||
3080 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
3081 | return 0; | |
3082 | ||
3083 | break; | |
3084 | ||
3085 | case INSN_JUMP_DYNAMIC: | |
3086 | if (sls && !insn->retpoline_safe && | |
3087 | next_insn && next_insn->type != INSN_TRAP) { | |
3088 | WARN_FUNC("missing int3 after indirect jump", | |
3089 | insn->sec, insn->offset); | |
3090 | } | |
3091 | ||
3092 | /* fallthrough */ | |
3093 | case INSN_JUMP_DYNAMIC_CONDITIONAL: | |
3094 | if (is_sibling_call(insn)) { | |
3095 | ret = validate_sibling_call(insn, &state); | |
3096 | if (ret) | |
3097 | return ret; | |
3098 | } | |
3099 | ||
3100 | if (insn->type == INSN_JUMP_DYNAMIC) | |
3101 | return 0; | |
3102 | ||
3103 | break; | |
3104 | ||
3105 | case INSN_CONTEXT_SWITCH: | |
3106 | if (func && (!next_insn || !next_insn->hint)) { | |
3107 | WARN_FUNC("unsupported instruction in callable function", | |
3108 | sec, insn->offset); | |
3109 | return 1; | |
3110 | } | |
3111 | return 0; | |
3112 | ||
3113 | case INSN_STAC: | |
3114 | if (state.uaccess) { | |
3115 | WARN_FUNC("recursive UACCESS enable", sec, insn->offset); | |
3116 | return 1; | |
3117 | } | |
3118 | ||
3119 | state.uaccess = true; | |
3120 | break; | |
3121 | ||
3122 | case INSN_CLAC: | |
3123 | if (!state.uaccess && func) { | |
3124 | WARN_FUNC("redundant UACCESS disable", sec, insn->offset); | |
3125 | return 1; | |
3126 | } | |
3127 | ||
3128 | if (func_uaccess_safe(func) && !state.uaccess_stack) { | |
3129 | WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); | |
3130 | return 1; | |
3131 | } | |
3132 | ||
3133 | state.uaccess = false; | |
3134 | break; | |
3135 | ||
3136 | case INSN_STD: | |
3137 | if (state.df) { | |
3138 | WARN_FUNC("recursive STD", sec, insn->offset); | |
3139 | return 1; | |
3140 | } | |
3141 | ||
3142 | state.df = true; | |
3143 | break; | |
3144 | ||
3145 | case INSN_CLD: | |
3146 | if (!state.df && func) { | |
3147 | WARN_FUNC("redundant CLD", sec, insn->offset); | |
3148 | return 1; | |
3149 | } | |
3150 | ||
3151 | state.df = false; | |
3152 | break; | |
3153 | ||
3154 | default: | |
3155 | break; | |
3156 | } | |
3157 | ||
3158 | if (insn->dead_end) | |
3159 | return 0; | |
3160 | ||
3161 | if (!next_insn) { | |
3162 | if (state.cfi.cfa.base == CFI_UNDEFINED) | |
3163 | return 0; | |
3164 | WARN("%s: unexpected end of section", sec->name); | |
3165 | return 1; | |
3166 | } | |
3167 | ||
3168 | prev_insn = insn; | |
3169 | insn = next_insn; | |
3170 | } | |
3171 | ||
3172 | return 0; | |
3173 | } | |
3174 | ||
3175 | static int validate_unwind_hints(struct objtool_file *file, struct section *sec) | |
3176 | { | |
3177 | struct instruction *insn; | |
3178 | struct insn_state state; | |
3179 | int ret, warnings = 0; | |
3180 | ||
3181 | if (!file->hints) | |
3182 | return 0; | |
3183 | ||
3184 | init_insn_state(&state, sec); | |
3185 | ||
3186 | if (sec) { | |
3187 | insn = find_insn(file, sec, 0); | |
3188 | if (!insn) | |
3189 | return 0; | |
3190 | } else { | |
3191 | insn = list_first_entry(&file->insn_list, typeof(*insn), list); | |
3192 | } | |
3193 | ||
3194 | while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) { | |
3195 | if (insn->hint && !insn->visited) { | |
3196 | ret = validate_branch(file, insn->func, insn, state); | |
3197 | if (ret && backtrace) | |
3198 | BT_FUNC("<=== (hint)", insn); | |
3199 | warnings += ret; | |
3200 | } | |
3201 | ||
3202 | insn = list_next_entry(insn, list); | |
3203 | } | |
3204 | ||
3205 | return warnings; | |
3206 | } | |
3207 | ||
3208 | static int validate_retpoline(struct objtool_file *file) | |
3209 | { | |
3210 | struct instruction *insn; | |
3211 | int warnings = 0; | |
3212 | ||
3213 | for_each_insn(file, insn) { | |
3214 | if (insn->type != INSN_JUMP_DYNAMIC && | |
3215 | insn->type != INSN_CALL_DYNAMIC) | |
3216 | continue; | |
3217 | ||
3218 | if (insn->retpoline_safe) | |
3219 | continue; | |
3220 | ||
3221 | /* | |
3222 | * .init.text code is ran before userspace and thus doesn't | |
3223 | * strictly need retpolines, except for modules which are | |
3224 | * loaded late, they very much do need retpoline in their | |
3225 | * .init.text | |
3226 | */ | |
3227 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
3228 | continue; | |
3229 | ||
3230 | WARN_FUNC("indirect %s found in RETPOLINE build", | |
3231 | insn->sec, insn->offset, | |
3232 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
3233 | ||
3234 | warnings++; | |
3235 | } | |
3236 | ||
3237 | return warnings; | |
3238 | } | |
3239 | ||
3240 | static bool is_kasan_insn(struct instruction *insn) | |
3241 | { | |
3242 | return (insn->type == INSN_CALL && | |
3243 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
3244 | } | |
3245 | ||
3246 | static bool is_ubsan_insn(struct instruction *insn) | |
3247 | { | |
3248 | return (insn->type == INSN_CALL && | |
3249 | !strcmp(insn->call_dest->name, | |
3250 | "__ubsan_handle_builtin_unreachable")); | |
3251 | } | |
3252 | ||
3253 | static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn) | |
3254 | { | |
3255 | int i; | |
3256 | struct instruction *prev_insn; | |
3257 | ||
3258 | if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP) | |
3259 | return true; | |
3260 | ||
3261 | /* | |
3262 | * Ignore any unused exceptions. This can happen when a whitelisted | |
3263 | * function has an exception table entry. | |
3264 | * | |
3265 | * Also ignore alternative replacement instructions. This can happen | |
3266 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
3267 | */ | |
3268 | if (!strcmp(insn->sec->name, ".fixup") || | |
3269 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
3270 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
3271 | return true; | |
3272 | ||
3273 | if (!insn->func) | |
3274 | return false; | |
3275 | ||
3276 | /* | |
3277 | * CONFIG_UBSAN_TRAP inserts a UD2 when it sees | |
3278 | * __builtin_unreachable(). The BUG() macro has an unreachable() after | |
3279 | * the UD2, which causes GCC's undefined trap logic to emit another UD2 | |
3280 | * (or occasionally a JMP to UD2). | |
3281 | * | |
3282 | * It may also insert a UD2 after calling a __noreturn function. | |
3283 | */ | |
3284 | prev_insn = list_prev_entry(insn, list); | |
3285 | if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) && | |
3286 | (insn->type == INSN_BUG || | |
3287 | (insn->type == INSN_JUMP_UNCONDITIONAL && | |
3288 | insn->jump_dest && insn->jump_dest->type == INSN_BUG))) | |
3289 | return true; | |
3290 | ||
3291 | /* | |
3292 | * Check if this (or a subsequent) instruction is related to | |
3293 | * CONFIG_UBSAN or CONFIG_KASAN. | |
3294 | * | |
3295 | * End the search at 5 instructions to avoid going into the weeds. | |
3296 | */ | |
3297 | for (i = 0; i < 5; i++) { | |
3298 | ||
3299 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
3300 | return true; | |
3301 | ||
3302 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { | |
3303 | if (insn->jump_dest && | |
3304 | insn->jump_dest->func == insn->func) { | |
3305 | insn = insn->jump_dest; | |
3306 | continue; | |
3307 | } | |
3308 | ||
3309 | break; | |
3310 | } | |
3311 | ||
3312 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) | |
3313 | break; | |
3314 | ||
3315 | insn = list_next_entry(insn, list); | |
3316 | } | |
3317 | ||
3318 | return false; | |
3319 | } | |
3320 | ||
3321 | static int validate_symbol(struct objtool_file *file, struct section *sec, | |
3322 | struct symbol *sym, struct insn_state *state) | |
3323 | { | |
3324 | struct instruction *insn; | |
3325 | int ret; | |
3326 | ||
3327 | if (!sym->len) { | |
3328 | WARN("%s() is missing an ELF size annotation", sym->name); | |
3329 | return 1; | |
3330 | } | |
3331 | ||
3332 | if (sym->pfunc != sym || sym->alias != sym) | |
3333 | return 0; | |
3334 | ||
3335 | insn = find_insn(file, sec, sym->offset); | |
3336 | if (!insn || insn->ignore || insn->visited) | |
3337 | return 0; | |
3338 | ||
3339 | state->uaccess = sym->uaccess_safe; | |
3340 | ||
3341 | ret = validate_branch(file, insn->func, insn, *state); | |
3342 | if (ret && backtrace) | |
3343 | BT_FUNC("<=== (sym)", insn); | |
3344 | return ret; | |
3345 | } | |
3346 | ||
3347 | static int validate_section(struct objtool_file *file, struct section *sec) | |
3348 | { | |
3349 | struct insn_state state; | |
3350 | struct symbol *func; | |
3351 | int warnings = 0; | |
3352 | ||
3353 | list_for_each_entry(func, &sec->symbol_list, list) { | |
3354 | if (func->type != STT_FUNC) | |
3355 | continue; | |
3356 | ||
3357 | init_insn_state(&state, sec); | |
3358 | set_func_state(&state.cfi); | |
3359 | ||
3360 | warnings += validate_symbol(file, sec, func, &state); | |
3361 | } | |
3362 | ||
3363 | return warnings; | |
3364 | } | |
3365 | ||
3366 | static int validate_vmlinux_functions(struct objtool_file *file) | |
3367 | { | |
3368 | struct section *sec; | |
3369 | int warnings = 0; | |
3370 | ||
3371 | sec = find_section_by_name(file->elf, ".noinstr.text"); | |
3372 | if (sec) { | |
3373 | warnings += validate_section(file, sec); | |
3374 | warnings += validate_unwind_hints(file, sec); | |
3375 | } | |
3376 | ||
3377 | sec = find_section_by_name(file->elf, ".entry.text"); | |
3378 | if (sec) { | |
3379 | warnings += validate_section(file, sec); | |
3380 | warnings += validate_unwind_hints(file, sec); | |
3381 | } | |
3382 | ||
3383 | return warnings; | |
3384 | } | |
3385 | ||
3386 | static int validate_functions(struct objtool_file *file) | |
3387 | { | |
3388 | struct section *sec; | |
3389 | int warnings = 0; | |
3390 | ||
3391 | for_each_sec(file, sec) { | |
3392 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
3393 | continue; | |
3394 | ||
3395 | warnings += validate_section(file, sec); | |
3396 | } | |
3397 | ||
3398 | return warnings; | |
3399 | } | |
3400 | ||
3401 | static int validate_reachable_instructions(struct objtool_file *file) | |
3402 | { | |
3403 | struct instruction *insn; | |
3404 | ||
3405 | if (file->ignore_unreachables) | |
3406 | return 0; | |
3407 | ||
3408 | for_each_insn(file, insn) { | |
3409 | if (insn->visited || ignore_unreachable_insn(file, insn)) | |
3410 | continue; | |
3411 | ||
3412 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); | |
3413 | return 1; | |
3414 | } | |
3415 | ||
3416 | return 0; | |
3417 | } | |
3418 | ||
3419 | int check(struct objtool_file *file) | |
3420 | { | |
3421 | int ret, warnings = 0; | |
3422 | ||
3423 | arch_initial_func_cfi_state(&initial_func_cfi); | |
3424 | init_cfi_state(&init_cfi); | |
3425 | init_cfi_state(&func_cfi); | |
3426 | set_func_state(&func_cfi); | |
3427 | ||
3428 | if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) | |
3429 | goto out; | |
3430 | ||
3431 | cfi_hash_add(&init_cfi); | |
3432 | cfi_hash_add(&func_cfi); | |
3433 | ||
3434 | ret = decode_sections(file); | |
3435 | if (ret < 0) | |
3436 | goto out; | |
3437 | ||
3438 | warnings += ret; | |
3439 | ||
3440 | if (list_empty(&file->insn_list)) | |
3441 | goto out; | |
3442 | ||
3443 | if (vmlinux && !validate_dup) { | |
3444 | ret = validate_vmlinux_functions(file); | |
3445 | if (ret < 0) | |
3446 | goto out; | |
3447 | ||
3448 | warnings += ret; | |
3449 | goto out; | |
3450 | } | |
3451 | ||
3452 | if (retpoline) { | |
3453 | ret = validate_retpoline(file); | |
3454 | if (ret < 0) | |
3455 | return ret; | |
3456 | warnings += ret; | |
3457 | } | |
3458 | ||
3459 | ret = validate_functions(file); | |
3460 | if (ret < 0) | |
3461 | goto out; | |
3462 | warnings += ret; | |
3463 | ||
3464 | ret = validate_unwind_hints(file, NULL); | |
3465 | if (ret < 0) | |
3466 | goto out; | |
3467 | warnings += ret; | |
3468 | ||
3469 | if (!warnings) { | |
3470 | ret = validate_reachable_instructions(file); | |
3471 | if (ret < 0) | |
3472 | goto out; | |
3473 | warnings += ret; | |
3474 | } | |
3475 | ||
3476 | ret = create_static_call_sections(file); | |
3477 | if (ret < 0) | |
3478 | goto out; | |
3479 | warnings += ret; | |
3480 | ||
3481 | if (retpoline) { | |
3482 | ret = create_retpoline_sites_sections(file); | |
3483 | if (ret < 0) | |
3484 | goto out; | |
3485 | warnings += ret; | |
3486 | ||
3487 | ret = create_return_sites_sections(file); | |
3488 | if (ret < 0) | |
3489 | goto out; | |
3490 | warnings += ret; | |
3491 | } | |
3492 | ||
3493 | if (mcount) { | |
3494 | ret = create_mcount_loc_sections(file); | |
3495 | if (ret < 0) | |
3496 | goto out; | |
3497 | warnings += ret; | |
3498 | } | |
3499 | ||
3500 | if (stats) { | |
3501 | printf("nr_insns_visited: %ld\n", nr_insns_visited); | |
3502 | printf("nr_cfi: %ld\n", nr_cfi); | |
3503 | printf("nr_cfi_reused: %ld\n", nr_cfi_reused); | |
3504 | printf("nr_cfi_cache: %ld\n", nr_cfi_cache); | |
3505 | } | |
3506 | ||
3507 | out: | |
3508 | /* | |
3509 | * For now, don't fail the kernel build on fatal warnings. These | |
3510 | * errors are still fairly common due to the growing matrix of | |
3511 | * supported toolchains and their recent pace of change. | |
3512 | */ | |
3513 | return 0; | |
3514 | } |