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1ccea77e | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
dcc914f4 JP |
2 | /* |
3 | * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> | |
dcc914f4 JP |
4 | */ |
5 | ||
6 | #include <string.h> | |
7 | #include <stdlib.h> | |
8 | ||
43a4525f | 9 | #include "builtin.h" |
dcc914f4 JP |
10 | #include "check.h" |
11 | #include "elf.h" | |
12 | #include "special.h" | |
13 | #include "arch.h" | |
14 | #include "warn.h" | |
15 | ||
16 | #include <linux/hashtable.h> | |
17 | #include <linux/kernel.h> | |
18 | ||
e6da9567 JP |
19 | #define FAKE_JUMP_OFFSET -1 |
20 | ||
87b512de JP |
21 | #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table" |
22 | ||
dcc914f4 JP |
23 | struct alternative { |
24 | struct list_head list; | |
25 | struct instruction *insn; | |
764eef4b | 26 | bool skip_orig; |
dcc914f4 JP |
27 | }; |
28 | ||
29 | const char *objname; | |
baa41469 | 30 | struct cfi_state initial_func_cfi; |
dcc914f4 | 31 | |
627fce14 JP |
32 | struct instruction *find_insn(struct objtool_file *file, |
33 | struct section *sec, unsigned long offset) | |
dcc914f4 JP |
34 | { |
35 | struct instruction *insn; | |
36 | ||
37 | hash_for_each_possible(file->insn_hash, insn, hash, offset) | |
38 | if (insn->sec == sec && insn->offset == offset) | |
39 | return insn; | |
40 | ||
41 | return NULL; | |
42 | } | |
43 | ||
44 | static struct instruction *next_insn_same_sec(struct objtool_file *file, | |
45 | struct instruction *insn) | |
46 | { | |
47 | struct instruction *next = list_next_entry(insn, list); | |
48 | ||
baa41469 | 49 | if (!next || &next->list == &file->insn_list || next->sec != insn->sec) |
dcc914f4 JP |
50 | return NULL; |
51 | ||
52 | return next; | |
53 | } | |
54 | ||
13810435 JP |
55 | static struct instruction *next_insn_same_func(struct objtool_file *file, |
56 | struct instruction *insn) | |
57 | { | |
58 | struct instruction *next = list_next_entry(insn, list); | |
59 | struct symbol *func = insn->func; | |
60 | ||
61 | if (!func) | |
62 | return NULL; | |
63 | ||
64 | if (&next->list != &file->insn_list && next->func == func) | |
65 | return next; | |
66 | ||
67 | /* Check if we're already in the subfunction: */ | |
68 | if (func == func->cfunc) | |
69 | return NULL; | |
70 | ||
71 | /* Move to the subfunction: */ | |
72 | return find_insn(file, func->cfunc->sec, func->cfunc->offset); | |
73 | } | |
74 | ||
75 | #define func_for_each_insn_all(file, func, insn) \ | |
76 | for (insn = find_insn(file, func->sec, func->offset); \ | |
77 | insn; \ | |
78 | insn = next_insn_same_func(file, insn)) | |
79 | ||
dcc914f4 JP |
80 | #define func_for_each_insn(file, func, insn) \ |
81 | for (insn = find_insn(file, func->sec, func->offset); \ | |
82 | insn && &insn->list != &file->insn_list && \ | |
83 | insn->sec == func->sec && \ | |
84 | insn->offset < func->offset + func->len; \ | |
85 | insn = list_next_entry(insn, list)) | |
86 | ||
87 | #define func_for_each_insn_continue_reverse(file, func, insn) \ | |
88 | for (insn = list_prev_entry(insn, list); \ | |
89 | &insn->list != &file->insn_list && \ | |
90 | insn->sec == func->sec && insn->offset >= func->offset; \ | |
91 | insn = list_prev_entry(insn, list)) | |
92 | ||
93 | #define sec_for_each_insn_from(file, insn) \ | |
94 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
95 | ||
baa41469 JP |
96 | #define sec_for_each_insn_continue(file, insn) \ |
97 | for (insn = next_insn_same_sec(file, insn); insn; \ | |
98 | insn = next_insn_same_sec(file, insn)) | |
dcc914f4 | 99 | |
a2296140 JP |
100 | static bool is_static_jump(struct instruction *insn) |
101 | { | |
102 | return insn->type == INSN_JUMP_CONDITIONAL || | |
103 | insn->type == INSN_JUMP_UNCONDITIONAL; | |
104 | } | |
105 | ||
0c1ddd33 JP |
106 | static bool is_sibling_call(struct instruction *insn) |
107 | { | |
108 | /* An indirect jump is either a sibling call or a jump to a table. */ | |
109 | if (insn->type == INSN_JUMP_DYNAMIC) | |
110 | return list_empty(&insn->alts); | |
111 | ||
a2296140 | 112 | if (!is_static_jump(insn)) |
0c1ddd33 JP |
113 | return false; |
114 | ||
115 | /* add_jump_destinations() sets insn->call_dest for sibling calls. */ | |
116 | return !!insn->call_dest; | |
117 | } | |
118 | ||
dcc914f4 JP |
119 | /* |
120 | * This checks to see if the given function is a "noreturn" function. | |
121 | * | |
122 | * For global functions which are outside the scope of this object file, we | |
123 | * have to keep a manual list of them. | |
124 | * | |
125 | * For local functions, we have to detect them manually by simply looking for | |
126 | * the lack of a return instruction. | |
dcc914f4 | 127 | */ |
8e25c9f8 JP |
128 | static bool __dead_end_function(struct objtool_file *file, struct symbol *func, |
129 | int recursion) | |
dcc914f4 JP |
130 | { |
131 | int i; | |
132 | struct instruction *insn; | |
133 | bool empty = true; | |
134 | ||
135 | /* | |
136 | * Unfortunately these have to be hard coded because the noreturn | |
137 | * attribute isn't provided in ELF data. | |
138 | */ | |
139 | static const char * const global_noreturns[] = { | |
140 | "__stack_chk_fail", | |
141 | "panic", | |
142 | "do_exit", | |
143 | "do_task_dead", | |
144 | "__module_put_and_exit", | |
145 | "complete_and_exit", | |
dcc914f4 JP |
146 | "__reiserfs_panic", |
147 | "lbug_with_loc", | |
148 | "fortify_panic", | |
b394d468 | 149 | "usercopy_abort", |
684fb246 | 150 | "machine_real_restart", |
4fa5ecda | 151 | "rewind_stack_do_exit", |
33adf80f | 152 | "kunit_try_catch_throw", |
dcc914f4 JP |
153 | }; |
154 | ||
c9bab22b JP |
155 | if (!func) |
156 | return false; | |
157 | ||
dcc914f4 | 158 | if (func->bind == STB_WEAK) |
8e25c9f8 | 159 | return false; |
dcc914f4 JP |
160 | |
161 | if (func->bind == STB_GLOBAL) | |
162 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
163 | if (!strcmp(func->name, global_noreturns[i])) | |
8e25c9f8 | 164 | return true; |
dcc914f4 | 165 | |
13810435 | 166 | if (!func->len) |
8e25c9f8 | 167 | return false; |
dcc914f4 | 168 | |
13810435 JP |
169 | insn = find_insn(file, func->sec, func->offset); |
170 | if (!insn->func) | |
8e25c9f8 | 171 | return false; |
13810435 JP |
172 | |
173 | func_for_each_insn_all(file, func, insn) { | |
dcc914f4 JP |
174 | empty = false; |
175 | ||
176 | if (insn->type == INSN_RETURN) | |
8e25c9f8 | 177 | return false; |
dcc914f4 JP |
178 | } |
179 | ||
180 | if (empty) | |
8e25c9f8 | 181 | return false; |
dcc914f4 JP |
182 | |
183 | /* | |
184 | * A function can have a sibling call instead of a return. In that | |
185 | * case, the function's dead-end status depends on whether the target | |
186 | * of the sibling call returns. | |
187 | */ | |
13810435 | 188 | func_for_each_insn_all(file, func, insn) { |
0c1ddd33 | 189 | if (is_sibling_call(insn)) { |
dcc914f4 | 190 | struct instruction *dest = insn->jump_dest; |
dcc914f4 JP |
191 | |
192 | if (!dest) | |
193 | /* sibling call to another file */ | |
8e25c9f8 | 194 | return false; |
dcc914f4 | 195 | |
0c1ddd33 JP |
196 | /* local sibling call */ |
197 | if (recursion == 5) { | |
198 | /* | |
199 | * Infinite recursion: two functions have | |
200 | * sibling calls to each other. This is a very | |
201 | * rare case. It means they aren't dead ends. | |
202 | */ | |
203 | return false; | |
dcc914f4 | 204 | } |
dcc914f4 | 205 | |
0c1ddd33 JP |
206 | return __dead_end_function(file, dest->func, recursion+1); |
207 | } | |
dcc914f4 JP |
208 | } |
209 | ||
8e25c9f8 | 210 | return true; |
dcc914f4 JP |
211 | } |
212 | ||
8e25c9f8 | 213 | static bool dead_end_function(struct objtool_file *file, struct symbol *func) |
dcc914f4 JP |
214 | { |
215 | return __dead_end_function(file, func, 0); | |
216 | } | |
217 | ||
baa41469 JP |
218 | static void clear_insn_state(struct insn_state *state) |
219 | { | |
220 | int i; | |
221 | ||
222 | memset(state, 0, sizeof(*state)); | |
223 | state->cfa.base = CFI_UNDEFINED; | |
dd88a0a0 | 224 | for (i = 0; i < CFI_NUM_REGS; i++) { |
baa41469 | 225 | state->regs[i].base = CFI_UNDEFINED; |
dd88a0a0 JP |
226 | state->vals[i].base = CFI_UNDEFINED; |
227 | } | |
baa41469 | 228 | state->drap_reg = CFI_UNDEFINED; |
bf4d1a83 | 229 | state->drap_offset = -1; |
baa41469 JP |
230 | } |
231 | ||
dcc914f4 JP |
232 | /* |
233 | * Call the arch-specific instruction decoder for all the instructions and add | |
234 | * them to the global instruction list. | |
235 | */ | |
236 | static int decode_instructions(struct objtool_file *file) | |
237 | { | |
238 | struct section *sec; | |
239 | struct symbol *func; | |
240 | unsigned long offset; | |
241 | struct instruction *insn; | |
242 | int ret; | |
243 | ||
baa41469 | 244 | for_each_sec(file, sec) { |
dcc914f4 JP |
245 | |
246 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
247 | continue; | |
248 | ||
627fce14 JP |
249 | if (strcmp(sec->name, ".altinstr_replacement") && |
250 | strcmp(sec->name, ".altinstr_aux") && | |
251 | strncmp(sec->name, ".discard.", 9)) | |
252 | sec->text = true; | |
253 | ||
dcc914f4 JP |
254 | for (offset = 0; offset < sec->len; offset += insn->len) { |
255 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
256 | if (!insn) { |
257 | WARN("malloc failed"); | |
258 | return -1; | |
259 | } | |
dcc914f4 | 260 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 261 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
262 | clear_insn_state(&insn->state); |
263 | ||
dcc914f4 JP |
264 | insn->sec = sec; |
265 | insn->offset = offset; | |
266 | ||
267 | ret = arch_decode_instruction(file->elf, sec, offset, | |
268 | sec->len - offset, | |
269 | &insn->len, &insn->type, | |
baa41469 JP |
270 | &insn->immediate, |
271 | &insn->stack_op); | |
dcc914f4 | 272 | if (ret) |
b7037983 | 273 | goto err; |
dcc914f4 | 274 | |
dcc914f4 JP |
275 | hash_add(file->insn_hash, &insn->hash, insn->offset); |
276 | list_add_tail(&insn->list, &file->insn_list); | |
277 | } | |
278 | ||
279 | list_for_each_entry(func, &sec->symbol_list, list) { | |
e10cd8fe | 280 | if (func->type != STT_FUNC || func->alias != func) |
dcc914f4 JP |
281 | continue; |
282 | ||
283 | if (!find_insn(file, sec, func->offset)) { | |
284 | WARN("%s(): can't find starting instruction", | |
285 | func->name); | |
286 | return -1; | |
287 | } | |
288 | ||
289 | func_for_each_insn(file, func, insn) | |
e10cd8fe | 290 | insn->func = func; |
dcc914f4 JP |
291 | } |
292 | } | |
293 | ||
294 | return 0; | |
b7037983 KB |
295 | |
296 | err: | |
297 | free(insn); | |
298 | return ret; | |
dcc914f4 JP |
299 | } |
300 | ||
301 | /* | |
649ea4d5 | 302 | * Mark "ud2" instructions and manually annotated dead ends. |
dcc914f4 JP |
303 | */ |
304 | static int add_dead_ends(struct objtool_file *file) | |
305 | { | |
306 | struct section *sec; | |
307 | struct rela *rela; | |
308 | struct instruction *insn; | |
309 | bool found; | |
310 | ||
649ea4d5 JP |
311 | /* |
312 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
313 | * GCC 7 inserts it for certain divide-by-zero cases. | |
314 | */ | |
315 | for_each_insn(file, insn) | |
316 | if (insn->type == INSN_BUG) | |
317 | insn->dead_end = true; | |
318 | ||
319 | /* | |
320 | * Check for manually annotated dead ends. | |
321 | */ | |
dcc914f4 JP |
322 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
323 | if (!sec) | |
649ea4d5 | 324 | goto reachable; |
dcc914f4 JP |
325 | |
326 | list_for_each_entry(rela, &sec->rela_list, list) { | |
327 | if (rela->sym->type != STT_SECTION) { | |
328 | WARN("unexpected relocation symbol type in %s", sec->name); | |
329 | return -1; | |
330 | } | |
331 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
332 | if (insn) | |
333 | insn = list_prev_entry(insn, list); | |
334 | else if (rela->addend == rela->sym->sec->len) { | |
335 | found = false; | |
336 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
337 | if (insn->sec == rela->sym->sec) { | |
338 | found = true; | |
339 | break; | |
340 | } | |
341 | } | |
342 | ||
343 | if (!found) { | |
344 | WARN("can't find unreachable insn at %s+0x%x", | |
345 | rela->sym->sec->name, rela->addend); | |
346 | return -1; | |
347 | } | |
348 | } else { | |
349 | WARN("can't find unreachable insn at %s+0x%x", | |
350 | rela->sym->sec->name, rela->addend); | |
351 | return -1; | |
352 | } | |
353 | ||
354 | insn->dead_end = true; | |
355 | } | |
356 | ||
649ea4d5 JP |
357 | reachable: |
358 | /* | |
359 | * These manually annotated reachable checks are needed for GCC 4.4, | |
360 | * where the Linux unreachable() macro isn't supported. In that case | |
361 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
362 | * not a dead end. | |
363 | */ | |
364 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
365 | if (!sec) | |
366 | return 0; | |
367 | ||
368 | list_for_each_entry(rela, &sec->rela_list, list) { | |
369 | if (rela->sym->type != STT_SECTION) { | |
370 | WARN("unexpected relocation symbol type in %s", sec->name); | |
371 | return -1; | |
372 | } | |
373 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
374 | if (insn) | |
375 | insn = list_prev_entry(insn, list); | |
376 | else if (rela->addend == rela->sym->sec->len) { | |
377 | found = false; | |
378 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
379 | if (insn->sec == rela->sym->sec) { | |
380 | found = true; | |
381 | break; | |
382 | } | |
383 | } | |
384 | ||
385 | if (!found) { | |
386 | WARN("can't find reachable insn at %s+0x%x", | |
387 | rela->sym->sec->name, rela->addend); | |
388 | return -1; | |
389 | } | |
390 | } else { | |
391 | WARN("can't find reachable insn at %s+0x%x", | |
392 | rela->sym->sec->name, rela->addend); | |
393 | return -1; | |
394 | } | |
395 | ||
396 | insn->dead_end = false; | |
397 | } | |
398 | ||
dcc914f4 JP |
399 | return 0; |
400 | } | |
401 | ||
402 | /* | |
403 | * Warnings shouldn't be reported for ignored functions. | |
404 | */ | |
405 | static void add_ignores(struct objtool_file *file) | |
406 | { | |
407 | struct instruction *insn; | |
408 | struct section *sec; | |
409 | struct symbol *func; | |
aaf5c623 | 410 | struct rela *rela; |
dcc914f4 | 411 | |
aaf5c623 PZ |
412 | sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); |
413 | if (!sec) | |
414 | return; | |
dcc914f4 | 415 | |
aaf5c623 PZ |
416 | list_for_each_entry(rela, &sec->rela_list, list) { |
417 | switch (rela->sym->type) { | |
418 | case STT_FUNC: | |
419 | func = rela->sym; | |
420 | break; | |
421 | ||
422 | case STT_SECTION: | |
423 | func = find_symbol_by_offset(rela->sym->sec, rela->addend); | |
424 | if (!func || func->type != STT_FUNC) | |
dcc914f4 | 425 | continue; |
aaf5c623 | 426 | break; |
dcc914f4 | 427 | |
aaf5c623 PZ |
428 | default: |
429 | WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type); | |
430 | continue; | |
dcc914f4 | 431 | } |
aaf5c623 PZ |
432 | |
433 | func_for_each_insn_all(file, func, insn) | |
434 | insn->ignore = true; | |
dcc914f4 JP |
435 | } |
436 | } | |
437 | ||
ea24213d PZ |
438 | /* |
439 | * This is a whitelist of functions that is allowed to be called with AC set. | |
440 | * The list is meant to be minimal and only contains compiler instrumentation | |
441 | * ABI and a few functions used to implement *_{to,from}_user() functions. | |
442 | * | |
443 | * These functions must not directly change AC, but may PUSHF/POPF. | |
444 | */ | |
445 | static const char *uaccess_safe_builtin[] = { | |
446 | /* KASAN */ | |
447 | "kasan_report", | |
448 | "check_memory_region", | |
449 | /* KASAN out-of-line */ | |
450 | "__asan_loadN_noabort", | |
451 | "__asan_load1_noabort", | |
452 | "__asan_load2_noabort", | |
453 | "__asan_load4_noabort", | |
454 | "__asan_load8_noabort", | |
455 | "__asan_load16_noabort", | |
456 | "__asan_storeN_noabort", | |
457 | "__asan_store1_noabort", | |
458 | "__asan_store2_noabort", | |
459 | "__asan_store4_noabort", | |
460 | "__asan_store8_noabort", | |
461 | "__asan_store16_noabort", | |
462 | /* KASAN in-line */ | |
463 | "__asan_report_load_n_noabort", | |
464 | "__asan_report_load1_noabort", | |
465 | "__asan_report_load2_noabort", | |
466 | "__asan_report_load4_noabort", | |
467 | "__asan_report_load8_noabort", | |
468 | "__asan_report_load16_noabort", | |
469 | "__asan_report_store_n_noabort", | |
470 | "__asan_report_store1_noabort", | |
471 | "__asan_report_store2_noabort", | |
472 | "__asan_report_store4_noabort", | |
473 | "__asan_report_store8_noabort", | |
474 | "__asan_report_store16_noabort", | |
475 | /* KCOV */ | |
476 | "write_comp_data", | |
477 | "__sanitizer_cov_trace_pc", | |
478 | "__sanitizer_cov_trace_const_cmp1", | |
479 | "__sanitizer_cov_trace_const_cmp2", | |
480 | "__sanitizer_cov_trace_const_cmp4", | |
481 | "__sanitizer_cov_trace_const_cmp8", | |
482 | "__sanitizer_cov_trace_cmp1", | |
483 | "__sanitizer_cov_trace_cmp2", | |
484 | "__sanitizer_cov_trace_cmp4", | |
485 | "__sanitizer_cov_trace_cmp8", | |
486 | /* UBSAN */ | |
487 | "ubsan_type_mismatch_common", | |
488 | "__ubsan_handle_type_mismatch", | |
489 | "__ubsan_handle_type_mismatch_v1", | |
9a50dcaf | 490 | "__ubsan_handle_shift_out_of_bounds", |
ea24213d PZ |
491 | /* misc */ |
492 | "csum_partial_copy_generic", | |
493 | "__memcpy_mcsafe", | |
a7e47f26 | 494 | "mcsafe_handle_tail", |
ea24213d PZ |
495 | "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ |
496 | NULL | |
497 | }; | |
498 | ||
499 | static void add_uaccess_safe(struct objtool_file *file) | |
500 | { | |
501 | struct symbol *func; | |
502 | const char **name; | |
503 | ||
504 | if (!uaccess) | |
505 | return; | |
506 | ||
507 | for (name = uaccess_safe_builtin; *name; name++) { | |
508 | func = find_symbol_by_name(file->elf, *name); | |
509 | if (!func) | |
510 | continue; | |
511 | ||
e10cd8fe | 512 | func->uaccess_safe = true; |
dcc914f4 JP |
513 | } |
514 | } | |
515 | ||
258c7605 JP |
516 | /* |
517 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
518 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
519 | * But it at least allows objtool to understand the control flow *around* the | |
520 | * retpoline. | |
521 | */ | |
ff05ab23 | 522 | static int add_ignore_alternatives(struct objtool_file *file) |
258c7605 JP |
523 | { |
524 | struct section *sec; | |
525 | struct rela *rela; | |
526 | struct instruction *insn; | |
527 | ||
ff05ab23 | 528 | sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); |
258c7605 JP |
529 | if (!sec) |
530 | return 0; | |
531 | ||
532 | list_for_each_entry(rela, &sec->rela_list, list) { | |
533 | if (rela->sym->type != STT_SECTION) { | |
534 | WARN("unexpected relocation symbol type in %s", sec->name); | |
535 | return -1; | |
536 | } | |
537 | ||
538 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
539 | if (!insn) { | |
ff05ab23 | 540 | WARN("bad .discard.ignore_alts entry"); |
258c7605 JP |
541 | return -1; |
542 | } | |
543 | ||
544 | insn->ignore_alts = true; | |
545 | } | |
546 | ||
547 | return 0; | |
548 | } | |
549 | ||
dcc914f4 JP |
550 | /* |
551 | * Find the destination instructions for all jumps. | |
552 | */ | |
553 | static int add_jump_destinations(struct objtool_file *file) | |
554 | { | |
555 | struct instruction *insn; | |
556 | struct rela *rela; | |
557 | struct section *dest_sec; | |
558 | unsigned long dest_off; | |
559 | ||
560 | for_each_insn(file, insn) { | |
a2296140 | 561 | if (!is_static_jump(insn)) |
dcc914f4 JP |
562 | continue; |
563 | ||
e6da9567 | 564 | if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET) |
dcc914f4 JP |
565 | continue; |
566 | ||
567 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
568 | insn->len); | |
569 | if (!rela) { | |
570 | dest_sec = insn->sec; | |
571 | dest_off = insn->offset + insn->len + insn->immediate; | |
572 | } else if (rela->sym->type == STT_SECTION) { | |
573 | dest_sec = rela->sym->sec; | |
574 | dest_off = rela->addend + 4; | |
575 | } else if (rela->sym->sec->idx) { | |
576 | dest_sec = rela->sym->sec; | |
577 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
578 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
579 | /* | |
580 | * Retpoline jumps are really dynamic jumps in | |
581 | * disguise, so convert them accordingly. | |
582 | */ | |
b68b9907 JP |
583 | if (insn->type == INSN_JUMP_UNCONDITIONAL) |
584 | insn->type = INSN_JUMP_DYNAMIC; | |
585 | else | |
586 | insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; | |
587 | ||
b5bc2231 | 588 | insn->retpoline_safe = true; |
39b73533 | 589 | continue; |
dcc914f4 | 590 | } else { |
0c1ddd33 | 591 | /* external sibling call */ |
54262aa2 | 592 | insn->call_dest = rela->sym; |
dcc914f4 JP |
593 | continue; |
594 | } | |
595 | ||
596 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
597 | if (!insn->jump_dest) { | |
598 | ||
599 | /* | |
600 | * This is a special case where an alt instruction | |
601 | * jumps past the end of the section. These are | |
602 | * handled later in handle_group_alt(). | |
603 | */ | |
604 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
605 | continue; | |
606 | ||
607 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
608 | insn->sec, insn->offset, dest_sec->name, | |
609 | dest_off); | |
610 | return -1; | |
611 | } | |
cd77849a JP |
612 | |
613 | /* | |
54262aa2 | 614 | * Cross-function jump. |
cd77849a JP |
615 | */ |
616 | if (insn->func && insn->jump_dest->func && | |
54262aa2 PZ |
617 | insn->func != insn->jump_dest->func) { |
618 | ||
619 | /* | |
620 | * For GCC 8+, create parent/child links for any cold | |
621 | * subfunctions. This is _mostly_ redundant with a | |
622 | * similar initialization in read_symbols(). | |
623 | * | |
624 | * If a function has aliases, we want the *first* such | |
625 | * function in the symbol table to be the subfunction's | |
626 | * parent. In that case we overwrite the | |
627 | * initialization done in read_symbols(). | |
628 | * | |
629 | * However this code can't completely replace the | |
630 | * read_symbols() code because this doesn't detect the | |
631 | * case where the parent function's only reference to a | |
e7c2bc37 | 632 | * subfunction is through a jump table. |
54262aa2 PZ |
633 | */ |
634 | if (!strstr(insn->func->name, ".cold.") && | |
635 | strstr(insn->jump_dest->func->name, ".cold.")) { | |
636 | insn->func->cfunc = insn->jump_dest->func; | |
637 | insn->jump_dest->func->pfunc = insn->func; | |
638 | ||
639 | } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && | |
640 | insn->jump_dest->offset == insn->jump_dest->func->offset) { | |
641 | ||
0c1ddd33 | 642 | /* internal sibling call */ |
54262aa2 | 643 | insn->call_dest = insn->jump_dest->func; |
54262aa2 | 644 | } |
cd77849a | 645 | } |
dcc914f4 JP |
646 | } |
647 | ||
648 | return 0; | |
649 | } | |
650 | ||
651 | /* | |
652 | * Find the destination instructions for all calls. | |
653 | */ | |
654 | static int add_call_destinations(struct objtool_file *file) | |
655 | { | |
656 | struct instruction *insn; | |
657 | unsigned long dest_off; | |
658 | struct rela *rela; | |
659 | ||
660 | for_each_insn(file, insn) { | |
661 | if (insn->type != INSN_CALL) | |
662 | continue; | |
663 | ||
664 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
665 | insn->len); | |
666 | if (!rela) { | |
667 | dest_off = insn->offset + insn->len + insn->immediate; | |
668 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
669 | dest_off); | |
a845c7cf JP |
670 | |
671 | if (!insn->call_dest && !insn->ignore) { | |
672 | WARN_FUNC("unsupported intra-function call", | |
673 | insn->sec, insn->offset); | |
b5bc2231 PZ |
674 | if (retpoline) |
675 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
676 | return -1; |
677 | } | |
a845c7cf | 678 | |
dcc914f4 JP |
679 | } else if (rela->sym->type == STT_SECTION) { |
680 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
681 | rela->addend+4); | |
682 | if (!insn->call_dest || | |
683 | insn->call_dest->type != STT_FUNC) { | |
684 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
685 | insn->sec, insn->offset, | |
686 | rela->sym->sec->name, | |
687 | rela->addend + 4); | |
688 | return -1; | |
689 | } | |
690 | } else | |
691 | insn->call_dest = rela->sym; | |
692 | } | |
693 | ||
694 | return 0; | |
695 | } | |
696 | ||
697 | /* | |
698 | * The .alternatives section requires some extra special care, over and above | |
699 | * what other special sections require: | |
700 | * | |
701 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
702 | * instruction at the end so that validate_branch() skips all the original | |
703 | * replaced instructions when validating the new instruction path. | |
704 | * | |
705 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
706 | * that case the old instructions are replaced with noops. We simulate that | |
707 | * by creating a fake jump as the only new instruction. | |
708 | * | |
709 | * 3. In some cases, the alternative section includes an instruction which | |
710 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
711 | * jumps' destinations to point back to .text rather than the end of the | |
712 | * entry in .altinstr_replacement. | |
dcc914f4 JP |
713 | */ |
714 | static int handle_group_alt(struct objtool_file *file, | |
715 | struct special_alt *special_alt, | |
716 | struct instruction *orig_insn, | |
717 | struct instruction **new_insn) | |
718 | { | |
17bc3391 | 719 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
720 | unsigned long dest_off; |
721 | ||
722 | last_orig_insn = NULL; | |
723 | insn = orig_insn; | |
724 | sec_for_each_insn_from(file, insn) { | |
725 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
726 | break; | |
727 | ||
dcc914f4 JP |
728 | insn->alt_group = true; |
729 | last_orig_insn = insn; | |
730 | } | |
731 | ||
17bc3391 JP |
732 | if (next_insn_same_sec(file, last_orig_insn)) { |
733 | fake_jump = malloc(sizeof(*fake_jump)); | |
734 | if (!fake_jump) { | |
735 | WARN("malloc failed"); | |
736 | return -1; | |
737 | } | |
738 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
739 | INIT_LIST_HEAD(&fake_jump->alts); | |
740 | clear_insn_state(&fake_jump->state); | |
741 | ||
742 | fake_jump->sec = special_alt->new_sec; | |
e6da9567 | 743 | fake_jump->offset = FAKE_JUMP_OFFSET; |
17bc3391 JP |
744 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; |
745 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
e6da9567 | 746 | fake_jump->func = orig_insn->func; |
dcc914f4 | 747 | } |
dcc914f4 JP |
748 | |
749 | if (!special_alt->new_len) { | |
17bc3391 JP |
750 | if (!fake_jump) { |
751 | WARN("%s: empty alternative at end of section", | |
752 | special_alt->orig_sec->name); | |
753 | return -1; | |
754 | } | |
755 | ||
dcc914f4 JP |
756 | *new_insn = fake_jump; |
757 | return 0; | |
758 | } | |
759 | ||
760 | last_new_insn = NULL; | |
761 | insn = *new_insn; | |
762 | sec_for_each_insn_from(file, insn) { | |
763 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
764 | break; | |
765 | ||
766 | last_new_insn = insn; | |
767 | ||
a845c7cf | 768 | insn->ignore = orig_insn->ignore_alts; |
a4d09dde | 769 | insn->func = orig_insn->func; |
a845c7cf | 770 | |
dc419723 JP |
771 | /* |
772 | * Since alternative replacement code is copy/pasted by the | |
773 | * kernel after applying relocations, generally such code can't | |
774 | * have relative-address relocation references to outside the | |
775 | * .altinstr_replacement section, unless the arch's | |
776 | * alternatives code can adjust the relative offsets | |
777 | * accordingly. | |
778 | * | |
779 | * The x86 alternatives code adjusts the offsets only when it | |
780 | * encounters a branch instruction at the very beginning of the | |
781 | * replacement group. | |
782 | */ | |
783 | if ((insn->offset != special_alt->new_off || | |
784 | (insn->type != INSN_CALL && !is_static_jump(insn))) && | |
785 | find_rela_by_dest_range(insn->sec, insn->offset, insn->len)) { | |
786 | ||
787 | WARN_FUNC("unsupported relocation in alternatives section", | |
788 | insn->sec, insn->offset); | |
789 | return -1; | |
790 | } | |
791 | ||
a2296140 | 792 | if (!is_static_jump(insn)) |
dcc914f4 JP |
793 | continue; |
794 | ||
795 | if (!insn->immediate) | |
796 | continue; | |
797 | ||
798 | dest_off = insn->offset + insn->len + insn->immediate; | |
17bc3391 JP |
799 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
800 | if (!fake_jump) { | |
801 | WARN("%s: alternative jump to end of section", | |
802 | special_alt->orig_sec->name); | |
803 | return -1; | |
804 | } | |
dcc914f4 | 805 | insn->jump_dest = fake_jump; |
17bc3391 | 806 | } |
dcc914f4 JP |
807 | |
808 | if (!insn->jump_dest) { | |
809 | WARN_FUNC("can't find alternative jump destination", | |
810 | insn->sec, insn->offset); | |
811 | return -1; | |
812 | } | |
813 | } | |
814 | ||
815 | if (!last_new_insn) { | |
816 | WARN_FUNC("can't find last new alternative instruction", | |
817 | special_alt->new_sec, special_alt->new_off); | |
818 | return -1; | |
819 | } | |
820 | ||
17bc3391 JP |
821 | if (fake_jump) |
822 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
823 | |
824 | return 0; | |
825 | } | |
826 | ||
827 | /* | |
828 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
829 | * If the original instruction is a jump, make the alt entry an effective nop | |
830 | * by just skipping the original instruction. | |
831 | */ | |
832 | static int handle_jump_alt(struct objtool_file *file, | |
833 | struct special_alt *special_alt, | |
834 | struct instruction *orig_insn, | |
835 | struct instruction **new_insn) | |
836 | { | |
837 | if (orig_insn->type == INSN_NOP) | |
838 | return 0; | |
839 | ||
840 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
841 | WARN_FUNC("unsupported instruction at jump label", | |
842 | orig_insn->sec, orig_insn->offset); | |
843 | return -1; | |
844 | } | |
845 | ||
846 | *new_insn = list_next_entry(orig_insn, list); | |
847 | return 0; | |
848 | } | |
849 | ||
850 | /* | |
851 | * Read all the special sections which have alternate instructions which can be | |
852 | * patched in or redirected to at runtime. Each instruction having alternate | |
853 | * instruction(s) has them added to its insn->alts list, which will be | |
854 | * traversed in validate_branch(). | |
855 | */ | |
856 | static int add_special_section_alts(struct objtool_file *file) | |
857 | { | |
858 | struct list_head special_alts; | |
859 | struct instruction *orig_insn, *new_insn; | |
860 | struct special_alt *special_alt, *tmp; | |
861 | struct alternative *alt; | |
862 | int ret; | |
863 | ||
864 | ret = special_get_alts(file->elf, &special_alts); | |
865 | if (ret) | |
866 | return ret; | |
867 | ||
868 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
869 | |
870 | orig_insn = find_insn(file, special_alt->orig_sec, | |
871 | special_alt->orig_off); | |
872 | if (!orig_insn) { | |
873 | WARN_FUNC("special: can't find orig instruction", | |
874 | special_alt->orig_sec, special_alt->orig_off); | |
875 | ret = -1; | |
876 | goto out; | |
877 | } | |
878 | ||
879 | new_insn = NULL; | |
880 | if (!special_alt->group || special_alt->new_len) { | |
881 | new_insn = find_insn(file, special_alt->new_sec, | |
882 | special_alt->new_off); | |
883 | if (!new_insn) { | |
884 | WARN_FUNC("special: can't find new instruction", | |
885 | special_alt->new_sec, | |
886 | special_alt->new_off); | |
887 | ret = -1; | |
888 | goto out; | |
889 | } | |
890 | } | |
891 | ||
892 | if (special_alt->group) { | |
893 | ret = handle_group_alt(file, special_alt, orig_insn, | |
894 | &new_insn); | |
895 | if (ret) | |
896 | goto out; | |
897 | } else if (special_alt->jump_or_nop) { | |
898 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
899 | &new_insn); | |
900 | if (ret) | |
901 | goto out; | |
902 | } | |
903 | ||
258c7605 JP |
904 | alt = malloc(sizeof(*alt)); |
905 | if (!alt) { | |
906 | WARN("malloc failed"); | |
907 | ret = -1; | |
908 | goto out; | |
909 | } | |
910 | ||
dcc914f4 | 911 | alt->insn = new_insn; |
764eef4b | 912 | alt->skip_orig = special_alt->skip_orig; |
ea24213d | 913 | orig_insn->ignore_alts |= special_alt->skip_alt; |
dcc914f4 JP |
914 | list_add_tail(&alt->list, &orig_insn->alts); |
915 | ||
916 | list_del(&special_alt->list); | |
917 | free(special_alt); | |
918 | } | |
919 | ||
920 | out: | |
921 | return ret; | |
922 | } | |
923 | ||
e7c2bc37 | 924 | static int add_jump_table(struct objtool_file *file, struct instruction *insn, |
bd98c813 | 925 | struct rela *table) |
dcc914f4 JP |
926 | { |
927 | struct rela *rela = table; | |
e7c2bc37 | 928 | struct instruction *dest_insn; |
dcc914f4 | 929 | struct alternative *alt; |
fd35c88b JP |
930 | struct symbol *pfunc = insn->func->pfunc; |
931 | unsigned int prev_offset = 0; | |
dcc914f4 | 932 | |
e7c2bc37 JP |
933 | /* |
934 | * Each @rela is a switch table relocation which points to the target | |
935 | * instruction. | |
936 | */ | |
937 | list_for_each_entry_from(rela, &table->sec->rela_list, list) { | |
bd98c813 JH |
938 | |
939 | /* Check for the end of the table: */ | |
940 | if (rela != table && rela->jump_table_start) | |
dcc914f4 JP |
941 | break; |
942 | ||
e7c2bc37 | 943 | /* Make sure the table entries are consecutive: */ |
fd35c88b JP |
944 | if (prev_offset && rela->offset != prev_offset + 8) |
945 | break; | |
946 | ||
947 | /* Detect function pointers from contiguous objects: */ | |
948 | if (rela->sym->sec == pfunc->sec && | |
949 | rela->addend == pfunc->offset) | |
950 | break; | |
951 | ||
e7c2bc37 JP |
952 | dest_insn = find_insn(file, rela->sym->sec, rela->addend); |
953 | if (!dest_insn) | |
dcc914f4 JP |
954 | break; |
955 | ||
e7c2bc37 | 956 | /* Make sure the destination is in the same function: */ |
e65050b9 | 957 | if (!dest_insn->func || dest_insn->func->pfunc != pfunc) |
13810435 | 958 | break; |
dcc914f4 JP |
959 | |
960 | alt = malloc(sizeof(*alt)); | |
961 | if (!alt) { | |
962 | WARN("malloc failed"); | |
963 | return -1; | |
964 | } | |
965 | ||
e7c2bc37 | 966 | alt->insn = dest_insn; |
dcc914f4 | 967 | list_add_tail(&alt->list, &insn->alts); |
fd35c88b JP |
968 | prev_offset = rela->offset; |
969 | } | |
970 | ||
971 | if (!prev_offset) { | |
972 | WARN_FUNC("can't find switch jump table", | |
973 | insn->sec, insn->offset); | |
974 | return -1; | |
dcc914f4 JP |
975 | } |
976 | ||
977 | return 0; | |
978 | } | |
979 | ||
980 | /* | |
e7c2bc37 | 981 | * find_jump_table() - Given a dynamic jump, find the switch jump table in |
dcc914f4 JP |
982 | * .rodata associated with it. |
983 | * | |
984 | * There are 3 basic patterns: | |
985 | * | |
986 | * 1. jmpq *[rodata addr](,%reg,8) | |
987 | * | |
988 | * This is the most common case by far. It jumps to an address in a simple | |
989 | * jump table which is stored in .rodata. | |
990 | * | |
991 | * 2. jmpq *[rodata addr](%rip) | |
992 | * | |
993 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
994 | * functions in the kernel, only with certain obscure non-distro configs. | |
995 | * | |
996 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
997 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
998 | * jump) to use a single entry in the table. The rest of the jump table and | |
999 | * some of its jump targets remain as dead code. | |
1000 | * | |
1001 | * In such a case we can just crudely ignore all unreachable instruction | |
1002 | * warnings for the entire object file. Ideally we would just ignore them | |
1003 | * for the function, but that would require redesigning the code quite a | |
1004 | * bit. And honestly that's just not worth doing: unreachable instruction | |
1005 | * warnings are of questionable value anyway, and this is such a rare issue. | |
1006 | * | |
1007 | * 3. mov [rodata addr],%reg1 | |
1008 | * ... some instructions ... | |
1009 | * jmpq *(%reg1,%reg2,8) | |
1010 | * | |
1011 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
1012 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
1013 | * | |
99ce7962 PZ |
1014 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
1015 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
1016 | * and jmpq uses .rodata itself, which can confuse things. | |
1017 | * | |
dcc914f4 JP |
1018 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
1019 | * ensure the same register is used in the mov and jump instructions. | |
99ce7962 PZ |
1020 | * |
1021 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 | 1022 | */ |
e7c2bc37 | 1023 | static struct rela *find_jump_table(struct objtool_file *file, |
dcc914f4 JP |
1024 | struct symbol *func, |
1025 | struct instruction *insn) | |
1026 | { | |
e7c2bc37 | 1027 | struct rela *text_rela, *table_rela; |
dcc914f4 | 1028 | struct instruction *orig_insn = insn; |
e7c2bc37 | 1029 | struct section *table_sec; |
6f5ec299 | 1030 | unsigned long table_offset; |
dcc914f4 | 1031 | |
99ce7962 PZ |
1032 | /* |
1033 | * Backward search using the @first_jump_src links, these help avoid | |
1034 | * much of the 'in between' code. Which avoids us getting confused by | |
1035 | * it. | |
1036 | */ | |
7dec80cc | 1037 | for (; |
99ce7962 PZ |
1038 | &insn->list != &file->insn_list && |
1039 | insn->sec == func->sec && | |
1040 | insn->offset >= func->offset; | |
1041 | ||
1042 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { | |
1043 | ||
7dec80cc | 1044 | if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) |
dcc914f4 JP |
1045 | break; |
1046 | ||
1047 | /* allow small jumps within the range */ | |
1048 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
1049 | insn->jump_dest && | |
1050 | (insn->jump_dest->offset <= insn->offset || | |
1051 | insn->jump_dest->offset > orig_insn->offset)) | |
1052 | break; | |
1053 | ||
1054 | /* look for a relocation which references .rodata */ | |
1055 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
1056 | insn->len); | |
4a60aa05 AX |
1057 | if (!text_rela || text_rela->sym->type != STT_SECTION || |
1058 | !text_rela->sym->sec->rodata) | |
dcc914f4 JP |
1059 | continue; |
1060 | ||
6f5ec299 | 1061 | table_offset = text_rela->addend; |
e7c2bc37 | 1062 | table_sec = text_rela->sym->sec; |
4a60aa05 | 1063 | |
6f5ec299 JP |
1064 | if (text_rela->type == R_X86_64_PC32) |
1065 | table_offset += 4; | |
1066 | ||
dcc914f4 JP |
1067 | /* |
1068 | * Make sure the .rodata address isn't associated with a | |
87b512de JP |
1069 | * symbol. GCC jump tables are anonymous data. |
1070 | * | |
1071 | * Also support C jump tables which are in the same format as | |
1072 | * switch jump tables. For objtool to recognize them, they | |
1073 | * need to be placed in the C_JUMP_TABLE_SECTION section. They | |
1074 | * have symbols associated with them. | |
dcc914f4 | 1075 | */ |
e7c2bc37 JP |
1076 | if (find_symbol_containing(table_sec, table_offset) && |
1077 | strcmp(table_sec->name, C_JUMP_TABLE_SECTION)) | |
1402fd8e JP |
1078 | continue; |
1079 | ||
e7c2bc37 JP |
1080 | /* Each table entry has a rela associated with it. */ |
1081 | table_rela = find_rela_by_dest(table_sec, table_offset); | |
1082 | if (!table_rela) | |
1083 | continue; | |
7dec80cc | 1084 | |
e7c2bc37 JP |
1085 | /* |
1086 | * Use of RIP-relative switch jumps is quite rare, and | |
1087 | * indicates a rare GCC quirk/bug which can leave dead code | |
1088 | * behind. | |
1089 | */ | |
1090 | if (text_rela->type == R_X86_64_PC32) | |
1091 | file->ignore_unreachables = true; | |
1092 | ||
1093 | return table_rela; | |
dcc914f4 JP |
1094 | } |
1095 | ||
1096 | return NULL; | |
1097 | } | |
1098 | ||
bd98c813 JH |
1099 | /* |
1100 | * First pass: Mark the head of each jump table so that in the next pass, | |
1101 | * we know when a given jump table ends and the next one starts. | |
1102 | */ | |
1103 | static void mark_func_jump_tables(struct objtool_file *file, | |
1104 | struct symbol *func) | |
dcc914f4 | 1105 | { |
bd98c813 JH |
1106 | struct instruction *insn, *last = NULL; |
1107 | struct rela *rela; | |
dcc914f4 | 1108 | |
13810435 | 1109 | func_for_each_insn_all(file, func, insn) { |
99ce7962 PZ |
1110 | if (!last) |
1111 | last = insn; | |
1112 | ||
1113 | /* | |
1114 | * Store back-pointers for unconditional forward jumps such | |
e7c2bc37 | 1115 | * that find_jump_table() can back-track using those and |
99ce7962 PZ |
1116 | * avoid some potentially confusing code. |
1117 | */ | |
1118 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
1119 | insn->offset > last->offset && | |
1120 | insn->jump_dest->offset > insn->offset && | |
1121 | !insn->jump_dest->first_jump_src) { | |
1122 | ||
1123 | insn->jump_dest->first_jump_src = insn; | |
1124 | last = insn->jump_dest; | |
1125 | } | |
1126 | ||
dcc914f4 JP |
1127 | if (insn->type != INSN_JUMP_DYNAMIC) |
1128 | continue; | |
1129 | ||
e7c2bc37 | 1130 | rela = find_jump_table(file, func, insn); |
bd98c813 JH |
1131 | if (rela) { |
1132 | rela->jump_table_start = true; | |
1133 | insn->jump_table = rela; | |
dcc914f4 | 1134 | } |
dcc914f4 | 1135 | } |
bd98c813 JH |
1136 | } |
1137 | ||
1138 | static int add_func_jump_tables(struct objtool_file *file, | |
1139 | struct symbol *func) | |
1140 | { | |
1141 | struct instruction *insn; | |
1142 | int ret; | |
1143 | ||
1144 | func_for_each_insn_all(file, func, insn) { | |
1145 | if (!insn->jump_table) | |
1146 | continue; | |
dcc914f4 | 1147 | |
bd98c813 | 1148 | ret = add_jump_table(file, insn, insn->jump_table); |
dcc914f4 JP |
1149 | if (ret) |
1150 | return ret; | |
1151 | } | |
1152 | ||
1153 | return 0; | |
1154 | } | |
1155 | ||
1156 | /* | |
1157 | * For some switch statements, gcc generates a jump table in the .rodata | |
1158 | * section which contains a list of addresses within the function to jump to. | |
1159 | * This finds these jump tables and adds them to the insn->alts lists. | |
1160 | */ | |
e7c2bc37 | 1161 | static int add_jump_table_alts(struct objtool_file *file) |
dcc914f4 JP |
1162 | { |
1163 | struct section *sec; | |
1164 | struct symbol *func; | |
1165 | int ret; | |
1166 | ||
4a60aa05 | 1167 | if (!file->rodata) |
dcc914f4 JP |
1168 | return 0; |
1169 | ||
baa41469 | 1170 | for_each_sec(file, sec) { |
dcc914f4 JP |
1171 | list_for_each_entry(func, &sec->symbol_list, list) { |
1172 | if (func->type != STT_FUNC) | |
1173 | continue; | |
1174 | ||
bd98c813 | 1175 | mark_func_jump_tables(file, func); |
e7c2bc37 | 1176 | ret = add_func_jump_tables(file, func); |
dcc914f4 JP |
1177 | if (ret) |
1178 | return ret; | |
1179 | } | |
1180 | } | |
1181 | ||
1182 | return 0; | |
1183 | } | |
1184 | ||
39358a03 JP |
1185 | static int read_unwind_hints(struct objtool_file *file) |
1186 | { | |
1187 | struct section *sec, *relasec; | |
1188 | struct rela *rela; | |
1189 | struct unwind_hint *hint; | |
1190 | struct instruction *insn; | |
1191 | struct cfi_reg *cfa; | |
1192 | int i; | |
1193 | ||
1194 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1195 | if (!sec) | |
1196 | return 0; | |
1197 | ||
1198 | relasec = sec->rela; | |
1199 | if (!relasec) { | |
1200 | WARN("missing .rela.discard.unwind_hints section"); | |
1201 | return -1; | |
1202 | } | |
1203 | ||
1204 | if (sec->len % sizeof(struct unwind_hint)) { | |
1205 | WARN("struct unwind_hint size mismatch"); | |
1206 | return -1; | |
1207 | } | |
1208 | ||
1209 | file->hints = true; | |
1210 | ||
1211 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1212 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1213 | ||
1214 | rela = find_rela_by_dest(sec, i * sizeof(*hint)); | |
1215 | if (!rela) { | |
1216 | WARN("can't find rela for unwind_hints[%d]", i); | |
1217 | return -1; | |
1218 | } | |
1219 | ||
1220 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1221 | if (!insn) { | |
1222 | WARN("can't find insn for unwind_hints[%d]", i); | |
1223 | return -1; | |
1224 | } | |
1225 | ||
1226 | cfa = &insn->state.cfa; | |
1227 | ||
1228 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1229 | insn->save = true; | |
1230 | continue; | |
1231 | ||
1232 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1233 | insn->restore = true; | |
1234 | insn->hint = true; | |
1235 | continue; | |
1236 | } | |
1237 | ||
1238 | insn->hint = true; | |
1239 | ||
1240 | switch (hint->sp_reg) { | |
1241 | case ORC_REG_UNDEFINED: | |
1242 | cfa->base = CFI_UNDEFINED; | |
1243 | break; | |
1244 | case ORC_REG_SP: | |
1245 | cfa->base = CFI_SP; | |
1246 | break; | |
1247 | case ORC_REG_BP: | |
1248 | cfa->base = CFI_BP; | |
1249 | break; | |
1250 | case ORC_REG_SP_INDIRECT: | |
1251 | cfa->base = CFI_SP_INDIRECT; | |
1252 | break; | |
1253 | case ORC_REG_R10: | |
1254 | cfa->base = CFI_R10; | |
1255 | break; | |
1256 | case ORC_REG_R13: | |
1257 | cfa->base = CFI_R13; | |
1258 | break; | |
1259 | case ORC_REG_DI: | |
1260 | cfa->base = CFI_DI; | |
1261 | break; | |
1262 | case ORC_REG_DX: | |
1263 | cfa->base = CFI_DX; | |
1264 | break; | |
1265 | default: | |
1266 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1267 | insn->sec, insn->offset, hint->sp_reg); | |
1268 | return -1; | |
1269 | } | |
1270 | ||
1271 | cfa->offset = hint->sp_offset; | |
1272 | insn->state.type = hint->type; | |
d31a5802 | 1273 | insn->state.end = hint->end; |
39358a03 JP |
1274 | } |
1275 | ||
1276 | return 0; | |
1277 | } | |
1278 | ||
b5bc2231 PZ |
1279 | static int read_retpoline_hints(struct objtool_file *file) |
1280 | { | |
63474dc4 | 1281 | struct section *sec; |
b5bc2231 PZ |
1282 | struct instruction *insn; |
1283 | struct rela *rela; | |
b5bc2231 | 1284 | |
63474dc4 | 1285 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
b5bc2231 PZ |
1286 | if (!sec) |
1287 | return 0; | |
1288 | ||
63474dc4 JP |
1289 | list_for_each_entry(rela, &sec->rela_list, list) { |
1290 | if (rela->sym->type != STT_SECTION) { | |
1291 | WARN("unexpected relocation symbol type in %s", sec->name); | |
b5bc2231 PZ |
1292 | return -1; |
1293 | } | |
1294 | ||
1295 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1296 | if (!insn) { | |
63474dc4 | 1297 | WARN("bad .discard.retpoline_safe entry"); |
b5bc2231 PZ |
1298 | return -1; |
1299 | } | |
1300 | ||
1301 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1302 | insn->type != INSN_CALL_DYNAMIC) { | |
63474dc4 | 1303 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
b5bc2231 PZ |
1304 | insn->sec, insn->offset); |
1305 | return -1; | |
1306 | } | |
1307 | ||
1308 | insn->retpoline_safe = true; | |
1309 | } | |
1310 | ||
1311 | return 0; | |
1312 | } | |
1313 | ||
4a60aa05 AX |
1314 | static void mark_rodata(struct objtool_file *file) |
1315 | { | |
1316 | struct section *sec; | |
1317 | bool found = false; | |
1318 | ||
1319 | /* | |
87b512de JP |
1320 | * Search for the following rodata sections, each of which can |
1321 | * potentially contain jump tables: | |
1322 | * | |
1323 | * - .rodata: can contain GCC switch tables | |
1324 | * - .rodata.<func>: same, if -fdata-sections is being used | |
1325 | * - .rodata..c_jump_table: contains C annotated jump tables | |
1326 | * | |
1327 | * .rodata.str1.* sections are ignored; they don't contain jump tables. | |
4a60aa05 AX |
1328 | */ |
1329 | for_each_sec(file, sec) { | |
87b512de JP |
1330 | if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) || |
1331 | !strcmp(sec->name, C_JUMP_TABLE_SECTION)) { | |
4a60aa05 AX |
1332 | sec->rodata = true; |
1333 | found = true; | |
1334 | } | |
1335 | } | |
1336 | ||
1337 | file->rodata = found; | |
1338 | } | |
1339 | ||
dcc914f4 JP |
1340 | static int decode_sections(struct objtool_file *file) |
1341 | { | |
1342 | int ret; | |
1343 | ||
4a60aa05 AX |
1344 | mark_rodata(file); |
1345 | ||
dcc914f4 JP |
1346 | ret = decode_instructions(file); |
1347 | if (ret) | |
1348 | return ret; | |
1349 | ||
1350 | ret = add_dead_ends(file); | |
1351 | if (ret) | |
1352 | return ret; | |
1353 | ||
1354 | add_ignores(file); | |
ea24213d | 1355 | add_uaccess_safe(file); |
dcc914f4 | 1356 | |
ff05ab23 | 1357 | ret = add_ignore_alternatives(file); |
258c7605 JP |
1358 | if (ret) |
1359 | return ret; | |
1360 | ||
dcc914f4 JP |
1361 | ret = add_jump_destinations(file); |
1362 | if (ret) | |
1363 | return ret; | |
1364 | ||
a845c7cf | 1365 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1366 | if (ret) |
1367 | return ret; | |
1368 | ||
a845c7cf | 1369 | ret = add_call_destinations(file); |
dcc914f4 JP |
1370 | if (ret) |
1371 | return ret; | |
1372 | ||
e7c2bc37 | 1373 | ret = add_jump_table_alts(file); |
dcc914f4 JP |
1374 | if (ret) |
1375 | return ret; | |
1376 | ||
39358a03 JP |
1377 | ret = read_unwind_hints(file); |
1378 | if (ret) | |
1379 | return ret; | |
1380 | ||
b5bc2231 PZ |
1381 | ret = read_retpoline_hints(file); |
1382 | if (ret) | |
1383 | return ret; | |
1384 | ||
dcc914f4 JP |
1385 | return 0; |
1386 | } | |
1387 | ||
1388 | static bool is_fentry_call(struct instruction *insn) | |
1389 | { | |
1390 | if (insn->type == INSN_CALL && | |
1391 | insn->call_dest->type == STT_NOTYPE && | |
1392 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1393 | return true; | |
1394 | ||
1395 | return false; | |
1396 | } | |
1397 | ||
baa41469 | 1398 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1399 | { |
baa41469 JP |
1400 | int i; |
1401 | ||
1402 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1403 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1404 | state->stack_size != initial_func_cfi.cfa.offset || | |
1405 | state->drap) | |
1406 | return true; | |
1407 | ||
1408 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1409 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1410 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1411 | return true; | |
1412 | ||
1413 | return false; | |
1414 | } | |
1415 | ||
1416 | static bool has_valid_stack_frame(struct insn_state *state) | |
1417 | { | |
1418 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1419 | state->regs[CFI_BP].offset == -16) | |
1420 | return true; | |
1421 | ||
1422 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1423 | return true; | |
1424 | ||
1425 | return false; | |
dcc914f4 JP |
1426 | } |
1427 | ||
627fce14 JP |
1428 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1429 | { | |
1430 | struct cfi_reg *cfa = &state->cfa; | |
1431 | struct stack_op *op = &insn->stack_op; | |
1432 | ||
1433 | if (cfa->base != CFI_SP) | |
1434 | return 0; | |
1435 | ||
1436 | /* push */ | |
ea24213d | 1437 | if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) |
627fce14 JP |
1438 | cfa->offset += 8; |
1439 | ||
1440 | /* pop */ | |
ea24213d | 1441 | if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) |
627fce14 JP |
1442 | cfa->offset -= 8; |
1443 | ||
1444 | /* add immediate to sp */ | |
1445 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1446 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1447 | cfa->offset -= op->src.offset; | |
1448 | ||
1449 | return 0; | |
1450 | } | |
1451 | ||
baa41469 JP |
1452 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1453 | int offset) | |
dcc914f4 | 1454 | { |
bf4d1a83 | 1455 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1456 | state->regs[reg].base == CFI_UNDEFINED) { |
1457 | state->regs[reg].base = base; | |
1458 | state->regs[reg].offset = offset; | |
1459 | } | |
dcc914f4 JP |
1460 | } |
1461 | ||
baa41469 | 1462 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1463 | { |
baa41469 JP |
1464 | state->regs[reg].base = CFI_UNDEFINED; |
1465 | state->regs[reg].offset = 0; | |
1466 | } | |
1467 | ||
1468 | /* | |
1469 | * A note about DRAP stack alignment: | |
1470 | * | |
1471 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1472 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1473 | * register. The typical DRAP pattern is: | |
1474 | * | |
1475 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1476 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1477 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1478 | * 55 push %rbp | |
1479 | * 48 89 e5 mov %rsp,%rbp | |
1480 | * (more pushes) | |
1481 | * 41 52 push %r10 | |
1482 | * ... | |
1483 | * 41 5a pop %r10 | |
1484 | * (more pops) | |
1485 | * 5d pop %rbp | |
1486 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1487 | * c3 retq | |
1488 | * | |
1489 | * There are some variations in the epilogues, like: | |
1490 | * | |
1491 | * 5b pop %rbx | |
1492 | * 41 5a pop %r10 | |
1493 | * 41 5c pop %r12 | |
1494 | * 41 5d pop %r13 | |
1495 | * 41 5e pop %r14 | |
1496 | * c9 leaveq | |
1497 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1498 | * c3 retq | |
1499 | * | |
1500 | * and: | |
1501 | * | |
1502 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1503 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1504 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1505 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1506 | * c9 leaveq | |
1507 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1508 | * c3 retq | |
1509 | * | |
1510 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1511 | * restored beforehand: | |
1512 | * | |
1513 | * 41 55 push %r13 | |
1514 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1515 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1516 | * ... | |
1517 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1518 | * 41 5d pop %r13 | |
1519 | * c3 retq | |
1520 | */ | |
1521 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1522 | { | |
1523 | struct stack_op *op = &insn->stack_op; | |
1524 | struct cfi_reg *cfa = &state->cfa; | |
1525 | struct cfi_reg *regs = state->regs; | |
1526 | ||
1527 | /* stack operations don't make sense with an undefined CFA */ | |
1528 | if (cfa->base == CFI_UNDEFINED) { | |
1529 | if (insn->func) { | |
1530 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1531 | return -1; | |
1532 | } | |
1533 | return 0; | |
1534 | } | |
1535 | ||
627fce14 JP |
1536 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1537 | return update_insn_state_regs(insn, state); | |
1538 | ||
baa41469 JP |
1539 | switch (op->dest.type) { |
1540 | ||
1541 | case OP_DEST_REG: | |
1542 | switch (op->src.type) { | |
1543 | ||
1544 | case OP_SRC_REG: | |
0d0970ee JP |
1545 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1546 | cfa->base == CFI_SP && | |
1547 | regs[CFI_BP].base == CFI_CFA && | |
1548 | regs[CFI_BP].offset == -cfa->offset) { | |
1549 | ||
1550 | /* mov %rsp, %rbp */ | |
1551 | cfa->base = op->dest.reg; | |
1552 | state->bp_scratch = false; | |
1553 | } | |
dd88a0a0 | 1554 | |
0d0970ee JP |
1555 | else if (op->src.reg == CFI_SP && |
1556 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1557 | |
0d0970ee JP |
1558 | /* drap: mov %rsp, %rbp */ |
1559 | regs[CFI_BP].base = CFI_BP; | |
1560 | regs[CFI_BP].offset = -state->stack_size; | |
1561 | state->bp_scratch = false; | |
1562 | } | |
dd88a0a0 | 1563 | |
0d0970ee JP |
1564 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1565 | ||
1566 | /* | |
1567 | * mov %rsp, %reg | |
1568 | * | |
1569 | * This is needed for the rare case where GCC | |
1570 | * does: | |
1571 | * | |
1572 | * mov %rsp, %rax | |
1573 | * ... | |
1574 | * mov %rax, %rsp | |
1575 | */ | |
1576 | state->vals[op->dest.reg].base = CFI_CFA; | |
1577 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1578 | } |
1579 | ||
3c1f0583 JP |
1580 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
1581 | cfa->base == CFI_BP) { | |
1582 | ||
1583 | /* | |
1584 | * mov %rbp, %rsp | |
1585 | * | |
1586 | * Restore the original stack pointer (Clang). | |
1587 | */ | |
1588 | state->stack_size = -state->regs[CFI_BP].offset; | |
1589 | } | |
1590 | ||
dd88a0a0 JP |
1591 | else if (op->dest.reg == cfa->base) { |
1592 | ||
1593 | /* mov %reg, %rsp */ | |
1594 | if (cfa->base == CFI_SP && | |
1595 | state->vals[op->src.reg].base == CFI_CFA) { | |
1596 | ||
1597 | /* | |
1598 | * This is needed for the rare case | |
1599 | * where GCC does something dumb like: | |
1600 | * | |
1601 | * lea 0x8(%rsp), %rcx | |
1602 | * ... | |
1603 | * mov %rcx, %rsp | |
1604 | */ | |
1605 | cfa->offset = -state->vals[op->src.reg].offset; | |
1606 | state->stack_size = cfa->offset; | |
1607 | ||
1608 | } else { | |
1609 | cfa->base = CFI_UNDEFINED; | |
1610 | cfa->offset = 0; | |
1611 | } | |
baa41469 JP |
1612 | } |
1613 | ||
1614 | break; | |
1615 | ||
1616 | case OP_SRC_ADD: | |
1617 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1618 | ||
1619 | /* add imm, %rsp */ | |
1620 | state->stack_size -= op->src.offset; | |
1621 | if (cfa->base == CFI_SP) | |
1622 | cfa->offset -= op->src.offset; | |
1623 | break; | |
1624 | } | |
1625 | ||
1626 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1627 | ||
1628 | /* lea disp(%rbp), %rsp */ | |
1629 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1630 | break; | |
1631 | } | |
1632 | ||
dd88a0a0 | 1633 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1634 | |
1635 | /* drap: lea disp(%rsp), %drap */ | |
1636 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1637 | |
1638 | /* | |
1639 | * lea disp(%rsp), %reg | |
1640 | * | |
1641 | * This is needed for the rare case where GCC | |
1642 | * does something dumb like: | |
1643 | * | |
1644 | * lea 0x8(%rsp), %rcx | |
1645 | * ... | |
1646 | * mov %rcx, %rsp | |
1647 | */ | |
1648 | state->vals[op->dest.reg].base = CFI_CFA; | |
1649 | state->vals[op->dest.reg].offset = \ | |
1650 | -state->stack_size + op->src.offset; | |
1651 | ||
baa41469 JP |
1652 | break; |
1653 | } | |
1654 | ||
1655 | if (state->drap && op->dest.reg == CFI_SP && | |
1656 | op->src.reg == state->drap_reg) { | |
1657 | ||
1658 | /* drap: lea disp(%drap), %rsp */ | |
1659 | cfa->base = CFI_SP; | |
1660 | cfa->offset = state->stack_size = -op->src.offset; | |
1661 | state->drap_reg = CFI_UNDEFINED; | |
1662 | state->drap = false; | |
1663 | break; | |
1664 | } | |
1665 | ||
1666 | if (op->dest.reg == state->cfa.base) { | |
1667 | WARN_FUNC("unsupported stack register modification", | |
1668 | insn->sec, insn->offset); | |
1669 | return -1; | |
1670 | } | |
1671 | ||
1672 | break; | |
1673 | ||
1674 | case OP_SRC_AND: | |
1675 | if (op->dest.reg != CFI_SP || | |
1676 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1677 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1678 | WARN_FUNC("unsupported stack pointer realignment", | |
1679 | insn->sec, insn->offset); | |
1680 | return -1; | |
1681 | } | |
1682 | ||
1683 | if (state->drap_reg != CFI_UNDEFINED) { | |
1684 | /* drap: and imm, %rsp */ | |
1685 | cfa->base = state->drap_reg; | |
1686 | cfa->offset = state->stack_size = 0; | |
1687 | state->drap = true; | |
baa41469 JP |
1688 | } |
1689 | ||
1690 | /* | |
1691 | * Older versions of GCC (4.8ish) realign the stack | |
1692 | * without DRAP, with a frame pointer. | |
1693 | */ | |
1694 | ||
1695 | break; | |
1696 | ||
1697 | case OP_SRC_POP: | |
ea24213d | 1698 | case OP_SRC_POPF: |
baa41469 JP |
1699 | if (!state->drap && op->dest.type == OP_DEST_REG && |
1700 | op->dest.reg == cfa->base) { | |
1701 | ||
1702 | /* pop %rbp */ | |
1703 | cfa->base = CFI_SP; | |
1704 | } | |
1705 | ||
bf4d1a83 JP |
1706 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1707 | op->dest.type == OP_DEST_REG && | |
1708 | op->dest.reg == state->drap_reg && | |
1709 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1710 | |
bf4d1a83 JP |
1711 | /* drap: pop %drap */ |
1712 | cfa->base = state->drap_reg; | |
1713 | cfa->offset = 0; | |
1714 | state->drap_offset = -1; | |
baa41469 | 1715 | |
bf4d1a83 | 1716 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1717 | |
bf4d1a83 | 1718 | /* pop %reg */ |
baa41469 JP |
1719 | restore_reg(state, op->dest.reg); |
1720 | } | |
1721 | ||
1722 | state->stack_size -= 8; | |
1723 | if (cfa->base == CFI_SP) | |
1724 | cfa->offset -= 8; | |
1725 | ||
1726 | break; | |
1727 | ||
1728 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1729 | if (state->drap && op->src.reg == CFI_BP && |
1730 | op->src.offset == state->drap_offset) { | |
1731 | ||
1732 | /* drap: mov disp(%rbp), %drap */ | |
1733 | cfa->base = state->drap_reg; | |
1734 | cfa->offset = 0; | |
1735 | state->drap_offset = -1; | |
1736 | } | |
1737 | ||
baa41469 JP |
1738 | if (state->drap && op->src.reg == CFI_BP && |
1739 | op->src.offset == regs[op->dest.reg].offset) { | |
1740 | ||
1741 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1742 | restore_reg(state, op->dest.reg); |
1743 | ||
1744 | } else if (op->src.reg == cfa->base && | |
1745 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1746 | ||
1747 | /* mov disp(%rbp), %reg */ | |
1748 | /* mov disp(%rsp), %reg */ | |
1749 | restore_reg(state, op->dest.reg); | |
1750 | } | |
1751 | ||
1752 | break; | |
1753 | ||
1754 | default: | |
1755 | WARN_FUNC("unknown stack-related instruction", | |
1756 | insn->sec, insn->offset); | |
1757 | return -1; | |
1758 | } | |
1759 | ||
1760 | break; | |
1761 | ||
1762 | case OP_DEST_PUSH: | |
ea24213d | 1763 | case OP_DEST_PUSHF: |
baa41469 JP |
1764 | state->stack_size += 8; |
1765 | if (cfa->base == CFI_SP) | |
1766 | cfa->offset += 8; | |
1767 | ||
1768 | if (op->src.type != OP_SRC_REG) | |
1769 | break; | |
1770 | ||
1771 | if (state->drap) { | |
1772 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1773 | ||
1774 | /* drap: push %drap */ | |
1775 | cfa->base = CFI_BP_INDIRECT; | |
1776 | cfa->offset = -state->stack_size; | |
1777 | ||
bf4d1a83 JP |
1778 | /* save drap so we know when to restore it */ |
1779 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1780 | |
1781 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1782 | ||
1783 | /* drap: push %rbp */ | |
1784 | state->stack_size = 0; | |
1785 | ||
1786 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1787 | ||
1788 | /* drap: push %reg */ | |
1789 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1790 | } | |
1791 | ||
1792 | } else { | |
1793 | ||
1794 | /* push %reg */ | |
1795 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1796 | } | |
1797 | ||
1798 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1799 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1800 | cfa->base != CFI_BP) |
1801 | state->bp_scratch = true; | |
1802 | break; | |
1803 | ||
1804 | case OP_DEST_REG_INDIRECT: | |
1805 | ||
1806 | if (state->drap) { | |
1807 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1808 | ||
1809 | /* drap: mov %drap, disp(%rbp) */ | |
1810 | cfa->base = CFI_BP_INDIRECT; | |
1811 | cfa->offset = op->dest.offset; | |
1812 | ||
bf4d1a83 JP |
1813 | /* save drap offset so we know when to restore it */ |
1814 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1815 | } |
1816 | ||
1817 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1818 | ||
1819 | /* drap: mov reg, disp(%rbp) */ | |
1820 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1821 | } | |
1822 | ||
1823 | } else if (op->dest.reg == cfa->base) { | |
1824 | ||
1825 | /* mov reg, disp(%rbp) */ | |
1826 | /* mov reg, disp(%rsp) */ | |
1827 | save_reg(state, op->src.reg, CFI_CFA, | |
1828 | op->dest.offset - state->cfa.offset); | |
1829 | } | |
1830 | ||
1831 | break; | |
1832 | ||
1833 | case OP_DEST_LEAVE: | |
1834 | if ((!state->drap && cfa->base != CFI_BP) || | |
1835 | (state->drap && cfa->base != state->drap_reg)) { | |
1836 | WARN_FUNC("leave instruction with modified stack frame", | |
1837 | insn->sec, insn->offset); | |
1838 | return -1; | |
1839 | } | |
1840 | ||
1841 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1842 | ||
1843 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1844 | restore_reg(state, CFI_BP); | |
1845 | ||
1846 | if (!state->drap) { | |
1847 | cfa->base = CFI_SP; | |
1848 | cfa->offset -= 8; | |
1849 | } | |
1850 | ||
1851 | break; | |
1852 | ||
1853 | case OP_DEST_MEM: | |
ea24213d | 1854 | if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { |
baa41469 JP |
1855 | WARN_FUNC("unknown stack-related memory operation", |
1856 | insn->sec, insn->offset); | |
1857 | return -1; | |
1858 | } | |
1859 | ||
1860 | /* pop mem */ | |
1861 | state->stack_size -= 8; | |
1862 | if (cfa->base == CFI_SP) | |
1863 | cfa->offset -= 8; | |
1864 | ||
1865 | break; | |
1866 | ||
1867 | default: | |
1868 | WARN_FUNC("unknown stack-related instruction", | |
1869 | insn->sec, insn->offset); | |
1870 | return -1; | |
1871 | } | |
1872 | ||
1873 | return 0; | |
1874 | } | |
1875 | ||
1876 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1877 | { | |
1878 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1879 | int i; | |
1880 | ||
1881 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1882 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1883 | insn->sec, insn->offset, | |
1884 | state1->cfa.base, state1->cfa.offset, | |
1885 | state2->cfa.base, state2->cfa.offset); | |
1886 | ||
1887 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1888 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1889 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1890 | sizeof(struct cfi_reg))) | |
1891 | continue; | |
1892 | ||
1893 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1894 | insn->sec, insn->offset, | |
1895 | i, state1->regs[i].base, state1->regs[i].offset, | |
1896 | i, state2->regs[i].base, state2->regs[i].offset); | |
1897 | break; | |
1898 | } | |
1899 | ||
627fce14 JP |
1900 | } else if (state1->type != state2->type) { |
1901 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1902 | insn->sec, insn->offset, state1->type, state2->type); | |
1903 | ||
baa41469 | 1904 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1905 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1906 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1907 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1908 | insn->sec, insn->offset, |
bf4d1a83 JP |
1909 | state1->drap, state1->drap_reg, state1->drap_offset, |
1910 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1911 | |
1912 | } else | |
1913 | return true; | |
1914 | ||
1915 | return false; | |
dcc914f4 JP |
1916 | } |
1917 | ||
ea24213d PZ |
1918 | static inline bool func_uaccess_safe(struct symbol *func) |
1919 | { | |
1920 | if (func) | |
e10cd8fe | 1921 | return func->uaccess_safe; |
ea24213d PZ |
1922 | |
1923 | return false; | |
1924 | } | |
1925 | ||
0c1ddd33 | 1926 | static inline const char *call_dest_name(struct instruction *insn) |
ea24213d PZ |
1927 | { |
1928 | if (insn->call_dest) | |
1929 | return insn->call_dest->name; | |
1930 | ||
1931 | return "{dynamic}"; | |
1932 | } | |
1933 | ||
1934 | static int validate_call(struct instruction *insn, struct insn_state *state) | |
1935 | { | |
1936 | if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { | |
1937 | WARN_FUNC("call to %s() with UACCESS enabled", | |
0c1ddd33 | 1938 | insn->sec, insn->offset, call_dest_name(insn)); |
ea24213d PZ |
1939 | return 1; |
1940 | } | |
1941 | ||
2f0f9e9a PZ |
1942 | if (state->df) { |
1943 | WARN_FUNC("call to %s() with DF set", | |
0c1ddd33 | 1944 | insn->sec, insn->offset, call_dest_name(insn)); |
2f0f9e9a PZ |
1945 | return 1; |
1946 | } | |
1947 | ||
ea24213d PZ |
1948 | return 0; |
1949 | } | |
1950 | ||
54262aa2 PZ |
1951 | static int validate_sibling_call(struct instruction *insn, struct insn_state *state) |
1952 | { | |
1953 | if (has_modified_stack_frame(state)) { | |
1954 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
1955 | insn->sec, insn->offset); | |
1956 | return 1; | |
1957 | } | |
1958 | ||
ea24213d | 1959 | return validate_call(insn, state); |
54262aa2 PZ |
1960 | } |
1961 | ||
dcc914f4 JP |
1962 | /* |
1963 | * Follow the branch starting at the given instruction, and recursively follow | |
1964 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
1965 | * each instruction and validate all the rules described in | |
1966 | * tools/objtool/Documentation/stack-validation.txt. | |
1967 | */ | |
c705cecc JP |
1968 | static int validate_branch(struct objtool_file *file, struct symbol *func, |
1969 | struct instruction *first, struct insn_state state) | |
dcc914f4 JP |
1970 | { |
1971 | struct alternative *alt; | |
39358a03 | 1972 | struct instruction *insn, *next_insn; |
dcc914f4 | 1973 | struct section *sec; |
882a0db9 | 1974 | u8 visited; |
dcc914f4 JP |
1975 | int ret; |
1976 | ||
1977 | insn = first; | |
1978 | sec = insn->sec; | |
dcc914f4 JP |
1979 | |
1980 | if (insn->alt_group && list_empty(&insn->alts)) { | |
1981 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
1982 | sec, insn->offset); | |
12b25729 | 1983 | return 1; |
dcc914f4 JP |
1984 | } |
1985 | ||
1986 | while (1) { | |
39358a03 JP |
1987 | next_insn = next_insn_same_sec(file, insn); |
1988 | ||
13810435 | 1989 | if (file->c_file && func && insn->func && func != insn->func->pfunc) { |
ee97638b JP |
1990 | WARN("%s() falls through to next function %s()", |
1991 | func->name, insn->func->name); | |
1992 | return 1; | |
dcc914f4 JP |
1993 | } |
1994 | ||
4855022a JP |
1995 | if (func && insn->ignore) { |
1996 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
1997 | sec, insn->offset); | |
12b25729 | 1998 | return 1; |
4855022a JP |
1999 | } |
2000 | ||
882a0db9 | 2001 | visited = 1 << state.uaccess; |
dcc914f4 | 2002 | if (insn->visited) { |
39358a03 | 2003 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 2004 | return 1; |
dcc914f4 | 2005 | |
882a0db9 | 2006 | if (insn->visited & visited) |
ea24213d | 2007 | return 0; |
dcc914f4 JP |
2008 | } |
2009 | ||
39358a03 JP |
2010 | if (insn->hint) { |
2011 | if (insn->restore) { | |
2012 | struct instruction *save_insn, *i; | |
2013 | ||
2014 | i = insn; | |
2015 | save_insn = NULL; | |
c705cecc | 2016 | func_for_each_insn_continue_reverse(file, func, i) { |
39358a03 JP |
2017 | if (i->save) { |
2018 | save_insn = i; | |
2019 | break; | |
2020 | } | |
2021 | } | |
2022 | ||
2023 | if (!save_insn) { | |
2024 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
2025 | sec, insn->offset); | |
2026 | return 1; | |
2027 | } | |
2028 | ||
2029 | if (!save_insn->visited) { | |
2030 | /* | |
2031 | * Oops, no state to copy yet. | |
2032 | * Hopefully we can reach this | |
2033 | * instruction from another branch | |
2034 | * after the save insn has been | |
2035 | * visited. | |
2036 | */ | |
2037 | if (insn == first) | |
2038 | return 0; | |
2039 | ||
2040 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
2041 | sec, insn->offset); | |
2042 | return 1; | |
2043 | } | |
2044 | ||
2045 | insn->state = save_insn->state; | |
2046 | } | |
2047 | ||
2048 | state = insn->state; | |
2049 | ||
2050 | } else | |
2051 | insn->state = state; | |
dcc914f4 | 2052 | |
882a0db9 | 2053 | insn->visited |= visited; |
baa41469 | 2054 | |
a845c7cf | 2055 | if (!insn->ignore_alts) { |
764eef4b PZ |
2056 | bool skip_orig = false; |
2057 | ||
a845c7cf | 2058 | list_for_each_entry(alt, &insn->alts, list) { |
764eef4b PZ |
2059 | if (alt->skip_orig) |
2060 | skip_orig = true; | |
2061 | ||
c705cecc | 2062 | ret = validate_branch(file, func, alt->insn, state); |
7697eee3 PZ |
2063 | if (ret) { |
2064 | if (backtrace) | |
2065 | BT_FUNC("(alt)", insn); | |
2066 | return ret; | |
2067 | } | |
a845c7cf | 2068 | } |
764eef4b PZ |
2069 | |
2070 | if (skip_orig) | |
2071 | return 0; | |
dcc914f4 JP |
2072 | } |
2073 | ||
2074 | switch (insn->type) { | |
2075 | ||
dcc914f4 | 2076 | case INSN_RETURN: |
ea24213d PZ |
2077 | if (state.uaccess && !func_uaccess_safe(func)) { |
2078 | WARN_FUNC("return with UACCESS enabled", sec, insn->offset); | |
2079 | return 1; | |
2080 | } | |
2081 | ||
2082 | if (!state.uaccess && func_uaccess_safe(func)) { | |
2083 | WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset); | |
2084 | return 1; | |
2085 | } | |
2086 | ||
2f0f9e9a PZ |
2087 | if (state.df) { |
2088 | WARN_FUNC("return with DF set", sec, insn->offset); | |
2089 | return 1; | |
2090 | } | |
2091 | ||
baa41469 JP |
2092 | if (func && has_modified_stack_frame(&state)) { |
2093 | WARN_FUNC("return with modified stack frame", | |
dcc914f4 JP |
2094 | sec, insn->offset); |
2095 | return 1; | |
2096 | } | |
baa41469 JP |
2097 | |
2098 | if (state.bp_scratch) { | |
2099 | WARN("%s uses BP as a scratch register", | |
c705cecc | 2100 | func->name); |
baa41469 JP |
2101 | return 1; |
2102 | } | |
2103 | ||
dcc914f4 JP |
2104 | return 0; |
2105 | ||
2106 | case INSN_CALL: | |
ea24213d PZ |
2107 | case INSN_CALL_DYNAMIC: |
2108 | ret = validate_call(insn, &state); | |
2109 | if (ret) | |
2110 | return ret; | |
dcc914f4 | 2111 | |
c9bab22b JP |
2112 | if (!no_fp && func && !is_fentry_call(insn) && |
2113 | !has_valid_stack_frame(&state)) { | |
dcc914f4 JP |
2114 | WARN_FUNC("call without frame pointer save/setup", |
2115 | sec, insn->offset); | |
2116 | return 1; | |
2117 | } | |
c9bab22b JP |
2118 | |
2119 | if (dead_end_function(file, insn->call_dest)) | |
2120 | return 0; | |
2121 | ||
dcc914f4 JP |
2122 | break; |
2123 | ||
2124 | case INSN_JUMP_CONDITIONAL: | |
2125 | case INSN_JUMP_UNCONDITIONAL: | |
0c1ddd33 | 2126 | if (func && is_sibling_call(insn)) { |
54262aa2 | 2127 | ret = validate_sibling_call(insn, &state); |
dcc914f4 | 2128 | if (ret) |
54262aa2 | 2129 | return ret; |
4855022a | 2130 | |
0c1ddd33 | 2131 | } else if (insn->jump_dest) { |
c705cecc JP |
2132 | ret = validate_branch(file, func, |
2133 | insn->jump_dest, state); | |
7697eee3 PZ |
2134 | if (ret) { |
2135 | if (backtrace) | |
2136 | BT_FUNC("(branch)", insn); | |
2137 | return ret; | |
2138 | } | |
4855022a | 2139 | } |
dcc914f4 JP |
2140 | |
2141 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
2142 | return 0; | |
2143 | ||
2144 | break; | |
2145 | ||
2146 | case INSN_JUMP_DYNAMIC: | |
b68b9907 | 2147 | case INSN_JUMP_DYNAMIC_CONDITIONAL: |
0c1ddd33 | 2148 | if (func && is_sibling_call(insn)) { |
54262aa2 PZ |
2149 | ret = validate_sibling_call(insn, &state); |
2150 | if (ret) | |
2151 | return ret; | |
dcc914f4 JP |
2152 | } |
2153 | ||
b68b9907 JP |
2154 | if (insn->type == INSN_JUMP_DYNAMIC) |
2155 | return 0; | |
2156 | ||
2157 | break; | |
dcc914f4 | 2158 | |
39358a03 JP |
2159 | case INSN_CONTEXT_SWITCH: |
2160 | if (func && (!next_insn || !next_insn->hint)) { | |
2161 | WARN_FUNC("unsupported instruction in callable function", | |
2162 | sec, insn->offset); | |
2163 | return 1; | |
2164 | } | |
2165 | return 0; | |
2166 | ||
baa41469 JP |
2167 | case INSN_STACK: |
2168 | if (update_insn_state(insn, &state)) | |
12b25729 | 2169 | return 1; |
baa41469 | 2170 | |
ea24213d PZ |
2171 | if (insn->stack_op.dest.type == OP_DEST_PUSHF) { |
2172 | if (!state.uaccess_stack) { | |
2173 | state.uaccess_stack = 1; | |
2174 | } else if (state.uaccess_stack >> 31) { | |
2175 | WARN_FUNC("PUSHF stack exhausted", sec, insn->offset); | |
2176 | return 1; | |
2177 | } | |
2178 | state.uaccess_stack <<= 1; | |
2179 | state.uaccess_stack |= state.uaccess; | |
2180 | } | |
2181 | ||
2182 | if (insn->stack_op.src.type == OP_SRC_POPF) { | |
2183 | if (state.uaccess_stack) { | |
2184 | state.uaccess = state.uaccess_stack & 1; | |
2185 | state.uaccess_stack >>= 1; | |
2186 | if (state.uaccess_stack == 1) | |
2187 | state.uaccess_stack = 0; | |
2188 | } | |
2189 | } | |
2190 | ||
2191 | break; | |
2192 | ||
2193 | case INSN_STAC: | |
2194 | if (state.uaccess) { | |
2195 | WARN_FUNC("recursive UACCESS enable", sec, insn->offset); | |
2196 | return 1; | |
2197 | } | |
2198 | ||
2199 | state.uaccess = true; | |
2200 | break; | |
2201 | ||
2202 | case INSN_CLAC: | |
c705cecc | 2203 | if (!state.uaccess && func) { |
ea24213d PZ |
2204 | WARN_FUNC("redundant UACCESS disable", sec, insn->offset); |
2205 | return 1; | |
2206 | } | |
2207 | ||
2208 | if (func_uaccess_safe(func) && !state.uaccess_stack) { | |
2209 | WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); | |
2210 | return 1; | |
2211 | } | |
2212 | ||
2213 | state.uaccess = false; | |
baa41469 JP |
2214 | break; |
2215 | ||
2f0f9e9a PZ |
2216 | case INSN_STD: |
2217 | if (state.df) | |
2218 | WARN_FUNC("recursive STD", sec, insn->offset); | |
2219 | ||
2220 | state.df = true; | |
2221 | break; | |
2222 | ||
2223 | case INSN_CLD: | |
c705cecc | 2224 | if (!state.df && func) |
2f0f9e9a PZ |
2225 | WARN_FUNC("redundant CLD", sec, insn->offset); |
2226 | ||
2227 | state.df = false; | |
baa41469 JP |
2228 | break; |
2229 | ||
dcc914f4 JP |
2230 | default: |
2231 | break; | |
2232 | } | |
2233 | ||
2234 | if (insn->dead_end) | |
2235 | return 0; | |
2236 | ||
00d96180 JP |
2237 | if (!next_insn) { |
2238 | if (state.cfa.base == CFI_UNDEFINED) | |
2239 | return 0; | |
dcc914f4 JP |
2240 | WARN("%s: unexpected end of section", sec->name); |
2241 | return 1; | |
2242 | } | |
00d96180 JP |
2243 | |
2244 | insn = next_insn; | |
dcc914f4 JP |
2245 | } |
2246 | ||
2247 | return 0; | |
2248 | } | |
2249 | ||
39358a03 JP |
2250 | static int validate_unwind_hints(struct objtool_file *file) |
2251 | { | |
2252 | struct instruction *insn; | |
2253 | int ret, warnings = 0; | |
2254 | struct insn_state state; | |
2255 | ||
2256 | if (!file->hints) | |
2257 | return 0; | |
2258 | ||
2259 | clear_insn_state(&state); | |
2260 | ||
2261 | for_each_insn(file, insn) { | |
2262 | if (insn->hint && !insn->visited) { | |
c705cecc | 2263 | ret = validate_branch(file, insn->func, insn, state); |
7697eee3 PZ |
2264 | if (ret && backtrace) |
2265 | BT_FUNC("<=== (hint)", insn); | |
39358a03 JP |
2266 | warnings += ret; |
2267 | } | |
2268 | } | |
2269 | ||
2270 | return warnings; | |
2271 | } | |
2272 | ||
b5bc2231 PZ |
2273 | static int validate_retpoline(struct objtool_file *file) |
2274 | { | |
2275 | struct instruction *insn; | |
2276 | int warnings = 0; | |
2277 | ||
2278 | for_each_insn(file, insn) { | |
2279 | if (insn->type != INSN_JUMP_DYNAMIC && | |
2280 | insn->type != INSN_CALL_DYNAMIC) | |
2281 | continue; | |
2282 | ||
2283 | if (insn->retpoline_safe) | |
2284 | continue; | |
2285 | ||
ca41b97e PZ |
2286 | /* |
2287 | * .init.text code is ran before userspace and thus doesn't | |
2288 | * strictly need retpolines, except for modules which are | |
2289 | * loaded late, they very much do need retpoline in their | |
2290 | * .init.text | |
2291 | */ | |
2292 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
2293 | continue; | |
2294 | ||
b5bc2231 PZ |
2295 | WARN_FUNC("indirect %s found in RETPOLINE build", |
2296 | insn->sec, insn->offset, | |
2297 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
2298 | ||
2299 | warnings++; | |
2300 | } | |
2301 | ||
2302 | return warnings; | |
2303 | } | |
2304 | ||
dcc914f4 JP |
2305 | static bool is_kasan_insn(struct instruction *insn) |
2306 | { | |
2307 | return (insn->type == INSN_CALL && | |
2308 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
2309 | } | |
2310 | ||
2311 | static bool is_ubsan_insn(struct instruction *insn) | |
2312 | { | |
2313 | return (insn->type == INSN_CALL && | |
2314 | !strcmp(insn->call_dest->name, | |
2315 | "__ubsan_handle_builtin_unreachable")); | |
2316 | } | |
2317 | ||
baa41469 | 2318 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
2319 | { |
2320 | int i; | |
2321 | ||
baa41469 JP |
2322 | if (insn->ignore || insn->type == INSN_NOP) |
2323 | return true; | |
2324 | ||
2325 | /* | |
2326 | * Ignore any unused exceptions. This can happen when a whitelisted | |
2327 | * function has an exception table entry. | |
0e2bb2bc JP |
2328 | * |
2329 | * Also ignore alternative replacement instructions. This can happen | |
2330 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 2331 | */ |
0e2bb2bc JP |
2332 | if (!strcmp(insn->sec->name, ".fixup") || |
2333 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
2334 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2335 | return true; |
2336 | ||
2337 | /* | |
2338 | * Check if this (or a subsequent) instruction is related to | |
2339 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2340 | * | |
2341 | * End the search at 5 instructions to avoid going into the weeds. | |
2342 | */ | |
baa41469 JP |
2343 | if (!insn->func) |
2344 | return false; | |
dcc914f4 JP |
2345 | for (i = 0; i < 5; i++) { |
2346 | ||
2347 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2348 | return true; | |
2349 | ||
fe24e271 JP |
2350 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2351 | if (insn->jump_dest && | |
2352 | insn->jump_dest->func == insn->func) { | |
2353 | insn = insn->jump_dest; | |
2354 | continue; | |
2355 | } | |
2356 | ||
2357 | break; | |
dcc914f4 JP |
2358 | } |
2359 | ||
baa41469 | 2360 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2361 | break; |
fe24e271 | 2362 | |
dcc914f4 JP |
2363 | insn = list_next_entry(insn, list); |
2364 | } | |
2365 | ||
2366 | return false; | |
2367 | } | |
2368 | ||
2369 | static int validate_functions(struct objtool_file *file) | |
2370 | { | |
2371 | struct section *sec; | |
2372 | struct symbol *func; | |
2373 | struct instruction *insn; | |
baa41469 | 2374 | struct insn_state state; |
dcc914f4 JP |
2375 | int ret, warnings = 0; |
2376 | ||
baa41469 JP |
2377 | clear_insn_state(&state); |
2378 | ||
2379 | state.cfa = initial_func_cfi.cfa; | |
2380 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2381 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2382 | state.stack_size = initial_func_cfi.cfa.offset; | |
2383 | ||
2384 | for_each_sec(file, sec) { | |
dcc914f4 | 2385 | list_for_each_entry(func, &sec->symbol_list, list) { |
e10cd8fe JP |
2386 | if (func->type != STT_FUNC) |
2387 | continue; | |
2388 | ||
61e9b75a JP |
2389 | if (!func->len) { |
2390 | WARN("%s() is missing an ELF size annotation", | |
2391 | func->name); | |
2392 | warnings++; | |
2393 | } | |
2394 | ||
e10cd8fe | 2395 | if (func->pfunc != func || func->alias != func) |
dcc914f4 JP |
2396 | continue; |
2397 | ||
2398 | insn = find_insn(file, sec, func->offset); | |
c705cecc | 2399 | if (!insn || insn->ignore || insn->visited) |
dcc914f4 JP |
2400 | continue; |
2401 | ||
e10cd8fe | 2402 | state.uaccess = func->uaccess_safe; |
ea24213d | 2403 | |
c705cecc | 2404 | ret = validate_branch(file, func, insn, state); |
7697eee3 PZ |
2405 | if (ret && backtrace) |
2406 | BT_FUNC("<=== (func)", insn); | |
dcc914f4 JP |
2407 | warnings += ret; |
2408 | } | |
2409 | } | |
2410 | ||
dcc914f4 JP |
2411 | return warnings; |
2412 | } | |
2413 | ||
baa41469 | 2414 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2415 | { |
2416 | struct instruction *insn; | |
baa41469 JP |
2417 | |
2418 | if (file->ignore_unreachables) | |
2419 | return 0; | |
dcc914f4 JP |
2420 | |
2421 | for_each_insn(file, insn) { | |
baa41469 JP |
2422 | if (insn->visited || ignore_unreachable_insn(insn)) |
2423 | continue; | |
2424 | ||
baa41469 JP |
2425 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2426 | return 1; | |
dcc914f4 JP |
2427 | } |
2428 | ||
baa41469 | 2429 | return 0; |
dcc914f4 JP |
2430 | } |
2431 | ||
2432 | static void cleanup(struct objtool_file *file) | |
2433 | { | |
2434 | struct instruction *insn, *tmpinsn; | |
2435 | struct alternative *alt, *tmpalt; | |
2436 | ||
2437 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { | |
2438 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { | |
2439 | list_del(&alt->list); | |
2440 | free(alt); | |
2441 | } | |
2442 | list_del(&insn->list); | |
2443 | hash_del(&insn->hash); | |
2444 | free(insn); | |
2445 | } | |
2446 | elf_close(file->elf); | |
2447 | } | |
2448 | ||
0c671812 JP |
2449 | static struct objtool_file file; |
2450 | ||
43a4525f | 2451 | int check(const char *_objname, bool orc) |
dcc914f4 | 2452 | { |
dcc914f4 JP |
2453 | int ret, warnings = 0; |
2454 | ||
2455 | objname = _objname; | |
dcc914f4 | 2456 | |
8e144797 | 2457 | file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2458 | if (!file.elf) |
dcc914f4 | 2459 | return 1; |
dcc914f4 JP |
2460 | |
2461 | INIT_LIST_HEAD(&file.insn_list); | |
2462 | hash_init(file.insn_hash); | |
dcc914f4 | 2463 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2464 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2465 | file.hints = false; |
dcc914f4 | 2466 | |
baa41469 JP |
2467 | arch_initial_func_cfi_state(&initial_func_cfi); |
2468 | ||
dcc914f4 JP |
2469 | ret = decode_sections(&file); |
2470 | if (ret < 0) | |
2471 | goto out; | |
2472 | warnings += ret; | |
2473 | ||
baa41469 | 2474 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2475 | goto out; |
dcc914f4 | 2476 | |
b5bc2231 PZ |
2477 | if (retpoline) { |
2478 | ret = validate_retpoline(&file); | |
2479 | if (ret < 0) | |
2480 | return ret; | |
2481 | warnings += ret; | |
2482 | } | |
2483 | ||
baa41469 | 2484 | ret = validate_functions(&file); |
dcc914f4 JP |
2485 | if (ret < 0) |
2486 | goto out; | |
2487 | warnings += ret; | |
2488 | ||
39358a03 JP |
2489 | ret = validate_unwind_hints(&file); |
2490 | if (ret < 0) | |
2491 | goto out; | |
2492 | warnings += ret; | |
2493 | ||
baa41469 JP |
2494 | if (!warnings) { |
2495 | ret = validate_reachable_instructions(&file); | |
2496 | if (ret < 0) | |
2497 | goto out; | |
2498 | warnings += ret; | |
2499 | } | |
2500 | ||
627fce14 JP |
2501 | if (orc) { |
2502 | ret = create_orc(&file); | |
2503 | if (ret < 0) | |
2504 | goto out; | |
2505 | ||
2506 | ret = create_orc_sections(&file); | |
2507 | if (ret < 0) | |
2508 | goto out; | |
2509 | ||
2510 | ret = elf_write(file.elf); | |
2511 | if (ret < 0) | |
2512 | goto out; | |
2513 | } | |
2514 | ||
dcc914f4 JP |
2515 | out: |
2516 | cleanup(&file); | |
2517 | ||
644592d3 JP |
2518 | if (ret < 0) { |
2519 | /* | |
2520 | * Fatal error. The binary is corrupt or otherwise broken in | |
2521 | * some way, or objtool itself is broken. Fail the kernel | |
2522 | * build. | |
2523 | */ | |
2524 | return ret; | |
2525 | } | |
2526 | ||
dcc914f4 JP |
2527 | return 0; |
2528 | } |