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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 | ||
f0f70adb | 75 | #define func_for_each_insn(file, func, insn) \ |
13810435 JP |
76 | for (insn = find_insn(file, func->sec, func->offset); \ |
77 | insn; \ | |
78 | insn = next_insn_same_func(file, insn)) | |
79 | ||
dbf4aeb0 PZ |
80 | #define sym_for_each_insn(file, sym, insn) \ |
81 | for (insn = find_insn(file, sym->sec, sym->offset); \ | |
dcc914f4 | 82 | insn && &insn->list != &file->insn_list && \ |
dbf4aeb0 PZ |
83 | insn->sec == sym->sec && \ |
84 | insn->offset < sym->offset + sym->len; \ | |
dcc914f4 JP |
85 | insn = list_next_entry(insn, list)) |
86 | ||
dbf4aeb0 | 87 | #define sym_for_each_insn_continue_reverse(file, sym, insn) \ |
dcc914f4 JP |
88 | for (insn = list_prev_entry(insn, list); \ |
89 | &insn->list != &file->insn_list && \ | |
dbf4aeb0 | 90 | insn->sec == sym->sec && insn->offset >= sym->offset; \ |
dcc914f4 JP |
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 | 172 | |
f0f70adb | 173 | func_for_each_insn(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 | */ | |
f0f70adb | 188 | func_for_each_insn(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; | |
1e11f3fd | 242 | unsigned long nr_insns = 0; |
dcc914f4 JP |
243 | int ret; |
244 | ||
baa41469 | 245 | for_each_sec(file, sec) { |
dcc914f4 JP |
246 | |
247 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
248 | continue; | |
249 | ||
627fce14 JP |
250 | if (strcmp(sec->name, ".altinstr_replacement") && |
251 | strcmp(sec->name, ".altinstr_aux") && | |
252 | strncmp(sec->name, ".discard.", 9)) | |
253 | sec->text = true; | |
254 | ||
dcc914f4 JP |
255 | for (offset = 0; offset < sec->len; offset += insn->len) { |
256 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
257 | if (!insn) { |
258 | WARN("malloc failed"); | |
259 | return -1; | |
260 | } | |
dcc914f4 | 261 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 262 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
263 | clear_insn_state(&insn->state); |
264 | ||
dcc914f4 JP |
265 | insn->sec = sec; |
266 | insn->offset = offset; | |
267 | ||
268 | ret = arch_decode_instruction(file->elf, sec, offset, | |
269 | sec->len - offset, | |
270 | &insn->len, &insn->type, | |
baa41469 JP |
271 | &insn->immediate, |
272 | &insn->stack_op); | |
dcc914f4 | 273 | if (ret) |
b7037983 | 274 | goto err; |
dcc914f4 | 275 | |
dcc914f4 JP |
276 | hash_add(file->insn_hash, &insn->hash, insn->offset); |
277 | list_add_tail(&insn->list, &file->insn_list); | |
1e11f3fd | 278 | nr_insns++; |
dcc914f4 JP |
279 | } |
280 | ||
281 | list_for_each_entry(func, &sec->symbol_list, list) { | |
e10cd8fe | 282 | if (func->type != STT_FUNC || func->alias != func) |
dcc914f4 JP |
283 | continue; |
284 | ||
285 | if (!find_insn(file, sec, func->offset)) { | |
286 | WARN("%s(): can't find starting instruction", | |
287 | func->name); | |
288 | return -1; | |
289 | } | |
290 | ||
dbf4aeb0 | 291 | sym_for_each_insn(file, func, insn) |
e10cd8fe | 292 | insn->func = func; |
dcc914f4 JP |
293 | } |
294 | } | |
295 | ||
1e11f3fd PZ |
296 | if (stats) |
297 | printf("nr_insns: %lu\n", nr_insns); | |
298 | ||
dcc914f4 | 299 | return 0; |
b7037983 KB |
300 | |
301 | err: | |
302 | free(insn); | |
303 | return ret; | |
dcc914f4 JP |
304 | } |
305 | ||
306 | /* | |
649ea4d5 | 307 | * Mark "ud2" instructions and manually annotated dead ends. |
dcc914f4 JP |
308 | */ |
309 | static int add_dead_ends(struct objtool_file *file) | |
310 | { | |
311 | struct section *sec; | |
312 | struct rela *rela; | |
313 | struct instruction *insn; | |
314 | bool found; | |
315 | ||
649ea4d5 JP |
316 | /* |
317 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
318 | * GCC 7 inserts it for certain divide-by-zero cases. | |
319 | */ | |
320 | for_each_insn(file, insn) | |
321 | if (insn->type == INSN_BUG) | |
322 | insn->dead_end = true; | |
323 | ||
324 | /* | |
325 | * Check for manually annotated dead ends. | |
326 | */ | |
dcc914f4 JP |
327 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
328 | if (!sec) | |
649ea4d5 | 329 | goto reachable; |
dcc914f4 JP |
330 | |
331 | list_for_each_entry(rela, &sec->rela_list, list) { | |
332 | if (rela->sym->type != STT_SECTION) { | |
333 | WARN("unexpected relocation symbol type in %s", sec->name); | |
334 | return -1; | |
335 | } | |
336 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
337 | if (insn) | |
338 | insn = list_prev_entry(insn, list); | |
339 | else if (rela->addend == rela->sym->sec->len) { | |
340 | found = false; | |
341 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
342 | if (insn->sec == rela->sym->sec) { | |
343 | found = true; | |
344 | break; | |
345 | } | |
346 | } | |
347 | ||
348 | if (!found) { | |
349 | WARN("can't find unreachable insn at %s+0x%x", | |
350 | rela->sym->sec->name, rela->addend); | |
351 | return -1; | |
352 | } | |
353 | } else { | |
354 | WARN("can't find unreachable insn at %s+0x%x", | |
355 | rela->sym->sec->name, rela->addend); | |
356 | return -1; | |
357 | } | |
358 | ||
359 | insn->dead_end = true; | |
360 | } | |
361 | ||
649ea4d5 JP |
362 | reachable: |
363 | /* | |
364 | * These manually annotated reachable checks are needed for GCC 4.4, | |
365 | * where the Linux unreachable() macro isn't supported. In that case | |
366 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
367 | * not a dead end. | |
368 | */ | |
369 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
370 | if (!sec) | |
371 | return 0; | |
372 | ||
373 | list_for_each_entry(rela, &sec->rela_list, list) { | |
374 | if (rela->sym->type != STT_SECTION) { | |
375 | WARN("unexpected relocation symbol type in %s", sec->name); | |
376 | return -1; | |
377 | } | |
378 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
379 | if (insn) | |
380 | insn = list_prev_entry(insn, list); | |
381 | else if (rela->addend == rela->sym->sec->len) { | |
382 | found = false; | |
383 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
384 | if (insn->sec == rela->sym->sec) { | |
385 | found = true; | |
386 | break; | |
387 | } | |
388 | } | |
389 | ||
390 | if (!found) { | |
391 | WARN("can't find reachable insn at %s+0x%x", | |
392 | rela->sym->sec->name, rela->addend); | |
393 | return -1; | |
394 | } | |
395 | } else { | |
396 | WARN("can't find reachable insn at %s+0x%x", | |
397 | rela->sym->sec->name, rela->addend); | |
398 | return -1; | |
399 | } | |
400 | ||
401 | insn->dead_end = false; | |
402 | } | |
403 | ||
dcc914f4 JP |
404 | return 0; |
405 | } | |
406 | ||
407 | /* | |
408 | * Warnings shouldn't be reported for ignored functions. | |
409 | */ | |
410 | static void add_ignores(struct objtool_file *file) | |
411 | { | |
412 | struct instruction *insn; | |
413 | struct section *sec; | |
414 | struct symbol *func; | |
aaf5c623 | 415 | struct rela *rela; |
dcc914f4 | 416 | |
aaf5c623 PZ |
417 | sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); |
418 | if (!sec) | |
419 | return; | |
dcc914f4 | 420 | |
aaf5c623 PZ |
421 | list_for_each_entry(rela, &sec->rela_list, list) { |
422 | switch (rela->sym->type) { | |
423 | case STT_FUNC: | |
424 | func = rela->sym; | |
425 | break; | |
426 | ||
427 | case STT_SECTION: | |
7acfe531 JP |
428 | func = find_func_by_offset(rela->sym->sec, rela->addend); |
429 | if (!func) | |
dcc914f4 | 430 | continue; |
aaf5c623 | 431 | break; |
dcc914f4 | 432 | |
aaf5c623 PZ |
433 | default: |
434 | WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type); | |
435 | continue; | |
dcc914f4 | 436 | } |
aaf5c623 | 437 | |
f0f70adb | 438 | func_for_each_insn(file, func, insn) |
aaf5c623 | 439 | insn->ignore = true; |
dcc914f4 JP |
440 | } |
441 | } | |
442 | ||
ea24213d PZ |
443 | /* |
444 | * This is a whitelist of functions that is allowed to be called with AC set. | |
445 | * The list is meant to be minimal and only contains compiler instrumentation | |
446 | * ABI and a few functions used to implement *_{to,from}_user() functions. | |
447 | * | |
448 | * These functions must not directly change AC, but may PUSHF/POPF. | |
449 | */ | |
450 | static const char *uaccess_safe_builtin[] = { | |
451 | /* KASAN */ | |
452 | "kasan_report", | |
453 | "check_memory_region", | |
454 | /* KASAN out-of-line */ | |
455 | "__asan_loadN_noabort", | |
456 | "__asan_load1_noabort", | |
457 | "__asan_load2_noabort", | |
458 | "__asan_load4_noabort", | |
459 | "__asan_load8_noabort", | |
460 | "__asan_load16_noabort", | |
461 | "__asan_storeN_noabort", | |
462 | "__asan_store1_noabort", | |
463 | "__asan_store2_noabort", | |
464 | "__asan_store4_noabort", | |
465 | "__asan_store8_noabort", | |
466 | "__asan_store16_noabort", | |
467 | /* KASAN in-line */ | |
468 | "__asan_report_load_n_noabort", | |
469 | "__asan_report_load1_noabort", | |
470 | "__asan_report_load2_noabort", | |
471 | "__asan_report_load4_noabort", | |
472 | "__asan_report_load8_noabort", | |
473 | "__asan_report_load16_noabort", | |
474 | "__asan_report_store_n_noabort", | |
475 | "__asan_report_store1_noabort", | |
476 | "__asan_report_store2_noabort", | |
477 | "__asan_report_store4_noabort", | |
478 | "__asan_report_store8_noabort", | |
479 | "__asan_report_store16_noabort", | |
480 | /* KCOV */ | |
481 | "write_comp_data", | |
482 | "__sanitizer_cov_trace_pc", | |
483 | "__sanitizer_cov_trace_const_cmp1", | |
484 | "__sanitizer_cov_trace_const_cmp2", | |
485 | "__sanitizer_cov_trace_const_cmp4", | |
486 | "__sanitizer_cov_trace_const_cmp8", | |
487 | "__sanitizer_cov_trace_cmp1", | |
488 | "__sanitizer_cov_trace_cmp2", | |
489 | "__sanitizer_cov_trace_cmp4", | |
490 | "__sanitizer_cov_trace_cmp8", | |
491 | /* UBSAN */ | |
492 | "ubsan_type_mismatch_common", | |
493 | "__ubsan_handle_type_mismatch", | |
494 | "__ubsan_handle_type_mismatch_v1", | |
9a50dcaf | 495 | "__ubsan_handle_shift_out_of_bounds", |
ea24213d PZ |
496 | /* misc */ |
497 | "csum_partial_copy_generic", | |
498 | "__memcpy_mcsafe", | |
a7e47f26 | 499 | "mcsafe_handle_tail", |
ea24213d PZ |
500 | "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ |
501 | NULL | |
502 | }; | |
503 | ||
504 | static void add_uaccess_safe(struct objtool_file *file) | |
505 | { | |
506 | struct symbol *func; | |
507 | const char **name; | |
508 | ||
509 | if (!uaccess) | |
510 | return; | |
511 | ||
512 | for (name = uaccess_safe_builtin; *name; name++) { | |
513 | func = find_symbol_by_name(file->elf, *name); | |
514 | if (!func) | |
515 | continue; | |
516 | ||
e10cd8fe | 517 | func->uaccess_safe = true; |
dcc914f4 JP |
518 | } |
519 | } | |
520 | ||
258c7605 JP |
521 | /* |
522 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
523 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
524 | * But it at least allows objtool to understand the control flow *around* the | |
525 | * retpoline. | |
526 | */ | |
ff05ab23 | 527 | static int add_ignore_alternatives(struct objtool_file *file) |
258c7605 JP |
528 | { |
529 | struct section *sec; | |
530 | struct rela *rela; | |
531 | struct instruction *insn; | |
532 | ||
ff05ab23 | 533 | sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); |
258c7605 JP |
534 | if (!sec) |
535 | return 0; | |
536 | ||
537 | list_for_each_entry(rela, &sec->rela_list, list) { | |
538 | if (rela->sym->type != STT_SECTION) { | |
539 | WARN("unexpected relocation symbol type in %s", sec->name); | |
540 | return -1; | |
541 | } | |
542 | ||
543 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
544 | if (!insn) { | |
ff05ab23 | 545 | WARN("bad .discard.ignore_alts entry"); |
258c7605 JP |
546 | return -1; |
547 | } | |
548 | ||
549 | insn->ignore_alts = true; | |
550 | } | |
551 | ||
552 | return 0; | |
553 | } | |
554 | ||
dcc914f4 JP |
555 | /* |
556 | * Find the destination instructions for all jumps. | |
557 | */ | |
558 | static int add_jump_destinations(struct objtool_file *file) | |
559 | { | |
560 | struct instruction *insn; | |
561 | struct rela *rela; | |
562 | struct section *dest_sec; | |
563 | unsigned long dest_off; | |
564 | ||
565 | for_each_insn(file, insn) { | |
a2296140 | 566 | if (!is_static_jump(insn)) |
dcc914f4 JP |
567 | continue; |
568 | ||
e6da9567 | 569 | if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET) |
dcc914f4 JP |
570 | continue; |
571 | ||
8b5fa6bc PZ |
572 | rela = find_rela_by_dest_range(file->elf, insn->sec, |
573 | insn->offset, insn->len); | |
dcc914f4 JP |
574 | if (!rela) { |
575 | dest_sec = insn->sec; | |
576 | dest_off = insn->offset + insn->len + insn->immediate; | |
577 | } else if (rela->sym->type == STT_SECTION) { | |
578 | dest_sec = rela->sym->sec; | |
579 | dest_off = rela->addend + 4; | |
580 | } else if (rela->sym->sec->idx) { | |
581 | dest_sec = rela->sym->sec; | |
582 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
583 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
584 | /* | |
585 | * Retpoline jumps are really dynamic jumps in | |
586 | * disguise, so convert them accordingly. | |
587 | */ | |
b68b9907 JP |
588 | if (insn->type == INSN_JUMP_UNCONDITIONAL) |
589 | insn->type = INSN_JUMP_DYNAMIC; | |
590 | else | |
591 | insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; | |
592 | ||
b5bc2231 | 593 | insn->retpoline_safe = true; |
39b73533 | 594 | continue; |
dcc914f4 | 595 | } else { |
0c1ddd33 | 596 | /* external sibling call */ |
54262aa2 | 597 | insn->call_dest = rela->sym; |
dcc914f4 JP |
598 | continue; |
599 | } | |
600 | ||
601 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
602 | if (!insn->jump_dest) { | |
603 | ||
604 | /* | |
605 | * This is a special case where an alt instruction | |
606 | * jumps past the end of the section. These are | |
607 | * handled later in handle_group_alt(). | |
608 | */ | |
609 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
610 | continue; | |
611 | ||
612 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
613 | insn->sec, insn->offset, dest_sec->name, | |
614 | dest_off); | |
615 | return -1; | |
616 | } | |
cd77849a JP |
617 | |
618 | /* | |
54262aa2 | 619 | * Cross-function jump. |
cd77849a JP |
620 | */ |
621 | if (insn->func && insn->jump_dest->func && | |
54262aa2 PZ |
622 | insn->func != insn->jump_dest->func) { |
623 | ||
624 | /* | |
625 | * For GCC 8+, create parent/child links for any cold | |
626 | * subfunctions. This is _mostly_ redundant with a | |
627 | * similar initialization in read_symbols(). | |
628 | * | |
629 | * If a function has aliases, we want the *first* such | |
630 | * function in the symbol table to be the subfunction's | |
631 | * parent. In that case we overwrite the | |
632 | * initialization done in read_symbols(). | |
633 | * | |
634 | * However this code can't completely replace the | |
635 | * read_symbols() code because this doesn't detect the | |
636 | * case where the parent function's only reference to a | |
e7c2bc37 | 637 | * subfunction is through a jump table. |
54262aa2 PZ |
638 | */ |
639 | if (!strstr(insn->func->name, ".cold.") && | |
640 | strstr(insn->jump_dest->func->name, ".cold.")) { | |
641 | insn->func->cfunc = insn->jump_dest->func; | |
642 | insn->jump_dest->func->pfunc = insn->func; | |
643 | ||
644 | } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && | |
645 | insn->jump_dest->offset == insn->jump_dest->func->offset) { | |
646 | ||
0c1ddd33 | 647 | /* internal sibling call */ |
54262aa2 | 648 | insn->call_dest = insn->jump_dest->func; |
54262aa2 | 649 | } |
cd77849a | 650 | } |
dcc914f4 JP |
651 | } |
652 | ||
653 | return 0; | |
654 | } | |
655 | ||
656 | /* | |
657 | * Find the destination instructions for all calls. | |
658 | */ | |
659 | static int add_call_destinations(struct objtool_file *file) | |
660 | { | |
661 | struct instruction *insn; | |
662 | unsigned long dest_off; | |
663 | struct rela *rela; | |
664 | ||
665 | for_each_insn(file, insn) { | |
666 | if (insn->type != INSN_CALL) | |
667 | continue; | |
668 | ||
8b5fa6bc PZ |
669 | rela = find_rela_by_dest_range(file->elf, insn->sec, |
670 | insn->offset, insn->len); | |
dcc914f4 JP |
671 | if (!rela) { |
672 | dest_off = insn->offset + insn->len + insn->immediate; | |
7acfe531 JP |
673 | insn->call_dest = find_func_by_offset(insn->sec, dest_off); |
674 | if (!insn->call_dest) | |
675 | insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); | |
a845c7cf | 676 | |
7acfe531 JP |
677 | if (insn->ignore) |
678 | continue; | |
679 | ||
680 | if (!insn->call_dest) { | |
a845c7cf JP |
681 | WARN_FUNC("unsupported intra-function call", |
682 | insn->sec, insn->offset); | |
b5bc2231 PZ |
683 | if (retpoline) |
684 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
685 | return -1; |
686 | } | |
a845c7cf | 687 | |
7acfe531 JP |
688 | if (insn->func && insn->call_dest->type != STT_FUNC) { |
689 | WARN_FUNC("unsupported call to non-function", | |
690 | insn->sec, insn->offset); | |
691 | return -1; | |
692 | } | |
693 | ||
dcc914f4 | 694 | } else if (rela->sym->type == STT_SECTION) { |
7acfe531 JP |
695 | insn->call_dest = find_func_by_offset(rela->sym->sec, |
696 | rela->addend+4); | |
697 | if (!insn->call_dest) { | |
dcc914f4 JP |
698 | WARN_FUNC("can't find call dest symbol at %s+0x%x", |
699 | insn->sec, insn->offset, | |
700 | rela->sym->sec->name, | |
701 | rela->addend + 4); | |
702 | return -1; | |
703 | } | |
704 | } else | |
705 | insn->call_dest = rela->sym; | |
706 | } | |
707 | ||
708 | return 0; | |
709 | } | |
710 | ||
711 | /* | |
712 | * The .alternatives section requires some extra special care, over and above | |
713 | * what other special sections require: | |
714 | * | |
715 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
716 | * instruction at the end so that validate_branch() skips all the original | |
717 | * replaced instructions when validating the new instruction path. | |
718 | * | |
719 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
720 | * that case the old instructions are replaced with noops. We simulate that | |
721 | * by creating a fake jump as the only new instruction. | |
722 | * | |
723 | * 3. In some cases, the alternative section includes an instruction which | |
724 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
725 | * jumps' destinations to point back to .text rather than the end of the | |
726 | * entry in .altinstr_replacement. | |
dcc914f4 JP |
727 | */ |
728 | static int handle_group_alt(struct objtool_file *file, | |
729 | struct special_alt *special_alt, | |
730 | struct instruction *orig_insn, | |
731 | struct instruction **new_insn) | |
732 | { | |
17bc3391 | 733 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
734 | unsigned long dest_off; |
735 | ||
736 | last_orig_insn = NULL; | |
737 | insn = orig_insn; | |
738 | sec_for_each_insn_from(file, insn) { | |
739 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
740 | break; | |
741 | ||
dcc914f4 JP |
742 | insn->alt_group = true; |
743 | last_orig_insn = insn; | |
744 | } | |
745 | ||
17bc3391 JP |
746 | if (next_insn_same_sec(file, last_orig_insn)) { |
747 | fake_jump = malloc(sizeof(*fake_jump)); | |
748 | if (!fake_jump) { | |
749 | WARN("malloc failed"); | |
750 | return -1; | |
751 | } | |
752 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
753 | INIT_LIST_HEAD(&fake_jump->alts); | |
754 | clear_insn_state(&fake_jump->state); | |
755 | ||
756 | fake_jump->sec = special_alt->new_sec; | |
e6da9567 | 757 | fake_jump->offset = FAKE_JUMP_OFFSET; |
17bc3391 JP |
758 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; |
759 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
e6da9567 | 760 | fake_jump->func = orig_insn->func; |
dcc914f4 | 761 | } |
dcc914f4 JP |
762 | |
763 | if (!special_alt->new_len) { | |
17bc3391 JP |
764 | if (!fake_jump) { |
765 | WARN("%s: empty alternative at end of section", | |
766 | special_alt->orig_sec->name); | |
767 | return -1; | |
768 | } | |
769 | ||
dcc914f4 JP |
770 | *new_insn = fake_jump; |
771 | return 0; | |
772 | } | |
773 | ||
774 | last_new_insn = NULL; | |
775 | insn = *new_insn; | |
776 | sec_for_each_insn_from(file, insn) { | |
777 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
778 | break; | |
779 | ||
780 | last_new_insn = insn; | |
781 | ||
a845c7cf | 782 | insn->ignore = orig_insn->ignore_alts; |
a4d09dde | 783 | insn->func = orig_insn->func; |
a845c7cf | 784 | |
dc419723 JP |
785 | /* |
786 | * Since alternative replacement code is copy/pasted by the | |
787 | * kernel after applying relocations, generally such code can't | |
788 | * have relative-address relocation references to outside the | |
789 | * .altinstr_replacement section, unless the arch's | |
790 | * alternatives code can adjust the relative offsets | |
791 | * accordingly. | |
792 | * | |
793 | * The x86 alternatives code adjusts the offsets only when it | |
794 | * encounters a branch instruction at the very beginning of the | |
795 | * replacement group. | |
796 | */ | |
797 | if ((insn->offset != special_alt->new_off || | |
798 | (insn->type != INSN_CALL && !is_static_jump(insn))) && | |
8b5fa6bc | 799 | find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) { |
dc419723 JP |
800 | |
801 | WARN_FUNC("unsupported relocation in alternatives section", | |
802 | insn->sec, insn->offset); | |
803 | return -1; | |
804 | } | |
805 | ||
a2296140 | 806 | if (!is_static_jump(insn)) |
dcc914f4 JP |
807 | continue; |
808 | ||
809 | if (!insn->immediate) | |
810 | continue; | |
811 | ||
812 | dest_off = insn->offset + insn->len + insn->immediate; | |
17bc3391 JP |
813 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
814 | if (!fake_jump) { | |
815 | WARN("%s: alternative jump to end of section", | |
816 | special_alt->orig_sec->name); | |
817 | return -1; | |
818 | } | |
dcc914f4 | 819 | insn->jump_dest = fake_jump; |
17bc3391 | 820 | } |
dcc914f4 JP |
821 | |
822 | if (!insn->jump_dest) { | |
823 | WARN_FUNC("can't find alternative jump destination", | |
824 | insn->sec, insn->offset); | |
825 | return -1; | |
826 | } | |
827 | } | |
828 | ||
829 | if (!last_new_insn) { | |
830 | WARN_FUNC("can't find last new alternative instruction", | |
831 | special_alt->new_sec, special_alt->new_off); | |
832 | return -1; | |
833 | } | |
834 | ||
17bc3391 JP |
835 | if (fake_jump) |
836 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
837 | |
838 | return 0; | |
839 | } | |
840 | ||
841 | /* | |
842 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
843 | * If the original instruction is a jump, make the alt entry an effective nop | |
844 | * by just skipping the original instruction. | |
845 | */ | |
846 | static int handle_jump_alt(struct objtool_file *file, | |
847 | struct special_alt *special_alt, | |
848 | struct instruction *orig_insn, | |
849 | struct instruction **new_insn) | |
850 | { | |
851 | if (orig_insn->type == INSN_NOP) | |
852 | return 0; | |
853 | ||
854 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
855 | WARN_FUNC("unsupported instruction at jump label", | |
856 | orig_insn->sec, orig_insn->offset); | |
857 | return -1; | |
858 | } | |
859 | ||
860 | *new_insn = list_next_entry(orig_insn, list); | |
861 | return 0; | |
862 | } | |
863 | ||
864 | /* | |
865 | * Read all the special sections which have alternate instructions which can be | |
866 | * patched in or redirected to at runtime. Each instruction having alternate | |
867 | * instruction(s) has them added to its insn->alts list, which will be | |
868 | * traversed in validate_branch(). | |
869 | */ | |
870 | static int add_special_section_alts(struct objtool_file *file) | |
871 | { | |
872 | struct list_head special_alts; | |
873 | struct instruction *orig_insn, *new_insn; | |
874 | struct special_alt *special_alt, *tmp; | |
875 | struct alternative *alt; | |
876 | int ret; | |
877 | ||
878 | ret = special_get_alts(file->elf, &special_alts); | |
879 | if (ret) | |
880 | return ret; | |
881 | ||
882 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
883 | |
884 | orig_insn = find_insn(file, special_alt->orig_sec, | |
885 | special_alt->orig_off); | |
886 | if (!orig_insn) { | |
887 | WARN_FUNC("special: can't find orig instruction", | |
888 | special_alt->orig_sec, special_alt->orig_off); | |
889 | ret = -1; | |
890 | goto out; | |
891 | } | |
892 | ||
893 | new_insn = NULL; | |
894 | if (!special_alt->group || special_alt->new_len) { | |
895 | new_insn = find_insn(file, special_alt->new_sec, | |
896 | special_alt->new_off); | |
897 | if (!new_insn) { | |
898 | WARN_FUNC("special: can't find new instruction", | |
899 | special_alt->new_sec, | |
900 | special_alt->new_off); | |
901 | ret = -1; | |
902 | goto out; | |
903 | } | |
904 | } | |
905 | ||
906 | if (special_alt->group) { | |
907 | ret = handle_group_alt(file, special_alt, orig_insn, | |
908 | &new_insn); | |
909 | if (ret) | |
910 | goto out; | |
911 | } else if (special_alt->jump_or_nop) { | |
912 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
913 | &new_insn); | |
914 | if (ret) | |
915 | goto out; | |
916 | } | |
917 | ||
258c7605 JP |
918 | alt = malloc(sizeof(*alt)); |
919 | if (!alt) { | |
920 | WARN("malloc failed"); | |
921 | ret = -1; | |
922 | goto out; | |
923 | } | |
924 | ||
dcc914f4 | 925 | alt->insn = new_insn; |
764eef4b | 926 | alt->skip_orig = special_alt->skip_orig; |
ea24213d | 927 | orig_insn->ignore_alts |= special_alt->skip_alt; |
dcc914f4 JP |
928 | list_add_tail(&alt->list, &orig_insn->alts); |
929 | ||
930 | list_del(&special_alt->list); | |
931 | free(special_alt); | |
932 | } | |
933 | ||
934 | out: | |
935 | return ret; | |
936 | } | |
937 | ||
e7c2bc37 | 938 | static int add_jump_table(struct objtool_file *file, struct instruction *insn, |
bd98c813 | 939 | struct rela *table) |
dcc914f4 JP |
940 | { |
941 | struct rela *rela = table; | |
e7c2bc37 | 942 | struct instruction *dest_insn; |
dcc914f4 | 943 | struct alternative *alt; |
fd35c88b JP |
944 | struct symbol *pfunc = insn->func->pfunc; |
945 | unsigned int prev_offset = 0; | |
dcc914f4 | 946 | |
e7c2bc37 JP |
947 | /* |
948 | * Each @rela is a switch table relocation which points to the target | |
949 | * instruction. | |
950 | */ | |
951 | list_for_each_entry_from(rela, &table->sec->rela_list, list) { | |
bd98c813 JH |
952 | |
953 | /* Check for the end of the table: */ | |
954 | if (rela != table && rela->jump_table_start) | |
dcc914f4 JP |
955 | break; |
956 | ||
e7c2bc37 | 957 | /* Make sure the table entries are consecutive: */ |
fd35c88b JP |
958 | if (prev_offset && rela->offset != prev_offset + 8) |
959 | break; | |
960 | ||
961 | /* Detect function pointers from contiguous objects: */ | |
962 | if (rela->sym->sec == pfunc->sec && | |
963 | rela->addend == pfunc->offset) | |
964 | break; | |
965 | ||
e7c2bc37 JP |
966 | dest_insn = find_insn(file, rela->sym->sec, rela->addend); |
967 | if (!dest_insn) | |
dcc914f4 JP |
968 | break; |
969 | ||
e7c2bc37 | 970 | /* Make sure the destination is in the same function: */ |
e65050b9 | 971 | if (!dest_insn->func || dest_insn->func->pfunc != pfunc) |
13810435 | 972 | break; |
dcc914f4 JP |
973 | |
974 | alt = malloc(sizeof(*alt)); | |
975 | if (!alt) { | |
976 | WARN("malloc failed"); | |
977 | return -1; | |
978 | } | |
979 | ||
e7c2bc37 | 980 | alt->insn = dest_insn; |
dcc914f4 | 981 | list_add_tail(&alt->list, &insn->alts); |
fd35c88b JP |
982 | prev_offset = rela->offset; |
983 | } | |
984 | ||
985 | if (!prev_offset) { | |
986 | WARN_FUNC("can't find switch jump table", | |
987 | insn->sec, insn->offset); | |
988 | return -1; | |
dcc914f4 JP |
989 | } |
990 | ||
991 | return 0; | |
992 | } | |
993 | ||
994 | /* | |
e7c2bc37 | 995 | * find_jump_table() - Given a dynamic jump, find the switch jump table in |
dcc914f4 JP |
996 | * .rodata associated with it. |
997 | * | |
998 | * There are 3 basic patterns: | |
999 | * | |
1000 | * 1. jmpq *[rodata addr](,%reg,8) | |
1001 | * | |
1002 | * This is the most common case by far. It jumps to an address in a simple | |
1003 | * jump table which is stored in .rodata. | |
1004 | * | |
1005 | * 2. jmpq *[rodata addr](%rip) | |
1006 | * | |
1007 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
1008 | * functions in the kernel, only with certain obscure non-distro configs. | |
1009 | * | |
1010 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
1011 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
1012 | * jump) to use a single entry in the table. The rest of the jump table and | |
1013 | * some of its jump targets remain as dead code. | |
1014 | * | |
1015 | * In such a case we can just crudely ignore all unreachable instruction | |
1016 | * warnings for the entire object file. Ideally we would just ignore them | |
1017 | * for the function, but that would require redesigning the code quite a | |
1018 | * bit. And honestly that's just not worth doing: unreachable instruction | |
1019 | * warnings are of questionable value anyway, and this is such a rare issue. | |
1020 | * | |
1021 | * 3. mov [rodata addr],%reg1 | |
1022 | * ... some instructions ... | |
1023 | * jmpq *(%reg1,%reg2,8) | |
1024 | * | |
1025 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
1026 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
1027 | * | |
99ce7962 PZ |
1028 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
1029 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
1030 | * and jmpq uses .rodata itself, which can confuse things. | |
1031 | * | |
dcc914f4 JP |
1032 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
1033 | * ensure the same register is used in the mov and jump instructions. | |
99ce7962 PZ |
1034 | * |
1035 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 | 1036 | */ |
e7c2bc37 | 1037 | static struct rela *find_jump_table(struct objtool_file *file, |
dcc914f4 JP |
1038 | struct symbol *func, |
1039 | struct instruction *insn) | |
1040 | { | |
e7c2bc37 | 1041 | struct rela *text_rela, *table_rela; |
113d4bc9 | 1042 | struct instruction *dest_insn, *orig_insn = insn; |
e7c2bc37 | 1043 | struct section *table_sec; |
6f5ec299 | 1044 | unsigned long table_offset; |
dcc914f4 | 1045 | |
99ce7962 PZ |
1046 | /* |
1047 | * Backward search using the @first_jump_src links, these help avoid | |
1048 | * much of the 'in between' code. Which avoids us getting confused by | |
1049 | * it. | |
1050 | */ | |
7dec80cc | 1051 | for (; |
99ce7962 PZ |
1052 | &insn->list != &file->insn_list && |
1053 | insn->sec == func->sec && | |
1054 | insn->offset >= func->offset; | |
1055 | ||
1056 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { | |
1057 | ||
7dec80cc | 1058 | if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) |
dcc914f4 JP |
1059 | break; |
1060 | ||
1061 | /* allow small jumps within the range */ | |
1062 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
1063 | insn->jump_dest && | |
1064 | (insn->jump_dest->offset <= insn->offset || | |
1065 | insn->jump_dest->offset > orig_insn->offset)) | |
1066 | break; | |
1067 | ||
1068 | /* look for a relocation which references .rodata */ | |
8b5fa6bc PZ |
1069 | text_rela = find_rela_by_dest_range(file->elf, insn->sec, |
1070 | insn->offset, insn->len); | |
4a60aa05 AX |
1071 | if (!text_rela || text_rela->sym->type != STT_SECTION || |
1072 | !text_rela->sym->sec->rodata) | |
dcc914f4 JP |
1073 | continue; |
1074 | ||
6f5ec299 | 1075 | table_offset = text_rela->addend; |
e7c2bc37 | 1076 | table_sec = text_rela->sym->sec; |
4a60aa05 | 1077 | |
6f5ec299 JP |
1078 | if (text_rela->type == R_X86_64_PC32) |
1079 | table_offset += 4; | |
1080 | ||
dcc914f4 JP |
1081 | /* |
1082 | * Make sure the .rodata address isn't associated with a | |
87b512de JP |
1083 | * symbol. GCC jump tables are anonymous data. |
1084 | * | |
1085 | * Also support C jump tables which are in the same format as | |
1086 | * switch jump tables. For objtool to recognize them, they | |
1087 | * need to be placed in the C_JUMP_TABLE_SECTION section. They | |
1088 | * have symbols associated with them. | |
dcc914f4 | 1089 | */ |
e7c2bc37 JP |
1090 | if (find_symbol_containing(table_sec, table_offset) && |
1091 | strcmp(table_sec->name, C_JUMP_TABLE_SECTION)) | |
1402fd8e JP |
1092 | continue; |
1093 | ||
113d4bc9 JP |
1094 | /* |
1095 | * Each table entry has a rela associated with it. The rela | |
1096 | * should reference text in the same function as the original | |
1097 | * instruction. | |
1098 | */ | |
8b5fa6bc | 1099 | table_rela = find_rela_by_dest(file->elf, table_sec, table_offset); |
e7c2bc37 JP |
1100 | if (!table_rela) |
1101 | continue; | |
113d4bc9 JP |
1102 | dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend); |
1103 | if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) | |
1104 | continue; | |
7dec80cc | 1105 | |
e7c2bc37 JP |
1106 | /* |
1107 | * Use of RIP-relative switch jumps is quite rare, and | |
1108 | * indicates a rare GCC quirk/bug which can leave dead code | |
1109 | * behind. | |
1110 | */ | |
1111 | if (text_rela->type == R_X86_64_PC32) | |
1112 | file->ignore_unreachables = true; | |
1113 | ||
1114 | return table_rela; | |
dcc914f4 JP |
1115 | } |
1116 | ||
1117 | return NULL; | |
1118 | } | |
1119 | ||
bd98c813 JH |
1120 | /* |
1121 | * First pass: Mark the head of each jump table so that in the next pass, | |
1122 | * we know when a given jump table ends and the next one starts. | |
1123 | */ | |
1124 | static void mark_func_jump_tables(struct objtool_file *file, | |
1125 | struct symbol *func) | |
dcc914f4 | 1126 | { |
bd98c813 JH |
1127 | struct instruction *insn, *last = NULL; |
1128 | struct rela *rela; | |
dcc914f4 | 1129 | |
f0f70adb | 1130 | func_for_each_insn(file, func, insn) { |
99ce7962 PZ |
1131 | if (!last) |
1132 | last = insn; | |
1133 | ||
1134 | /* | |
1135 | * Store back-pointers for unconditional forward jumps such | |
e7c2bc37 | 1136 | * that find_jump_table() can back-track using those and |
99ce7962 PZ |
1137 | * avoid some potentially confusing code. |
1138 | */ | |
1139 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
1140 | insn->offset > last->offset && | |
1141 | insn->jump_dest->offset > insn->offset && | |
1142 | !insn->jump_dest->first_jump_src) { | |
1143 | ||
1144 | insn->jump_dest->first_jump_src = insn; | |
1145 | last = insn->jump_dest; | |
1146 | } | |
1147 | ||
dcc914f4 JP |
1148 | if (insn->type != INSN_JUMP_DYNAMIC) |
1149 | continue; | |
1150 | ||
e7c2bc37 | 1151 | rela = find_jump_table(file, func, insn); |
bd98c813 JH |
1152 | if (rela) { |
1153 | rela->jump_table_start = true; | |
1154 | insn->jump_table = rela; | |
dcc914f4 | 1155 | } |
dcc914f4 | 1156 | } |
bd98c813 JH |
1157 | } |
1158 | ||
1159 | static int add_func_jump_tables(struct objtool_file *file, | |
1160 | struct symbol *func) | |
1161 | { | |
1162 | struct instruction *insn; | |
1163 | int ret; | |
1164 | ||
f0f70adb | 1165 | func_for_each_insn(file, func, insn) { |
bd98c813 JH |
1166 | if (!insn->jump_table) |
1167 | continue; | |
dcc914f4 | 1168 | |
bd98c813 | 1169 | ret = add_jump_table(file, insn, insn->jump_table); |
dcc914f4 JP |
1170 | if (ret) |
1171 | return ret; | |
1172 | } | |
1173 | ||
1174 | return 0; | |
1175 | } | |
1176 | ||
1177 | /* | |
1178 | * For some switch statements, gcc generates a jump table in the .rodata | |
1179 | * section which contains a list of addresses within the function to jump to. | |
1180 | * This finds these jump tables and adds them to the insn->alts lists. | |
1181 | */ | |
e7c2bc37 | 1182 | static int add_jump_table_alts(struct objtool_file *file) |
dcc914f4 JP |
1183 | { |
1184 | struct section *sec; | |
1185 | struct symbol *func; | |
1186 | int ret; | |
1187 | ||
4a60aa05 | 1188 | if (!file->rodata) |
dcc914f4 JP |
1189 | return 0; |
1190 | ||
baa41469 | 1191 | for_each_sec(file, sec) { |
dcc914f4 JP |
1192 | list_for_each_entry(func, &sec->symbol_list, list) { |
1193 | if (func->type != STT_FUNC) | |
1194 | continue; | |
1195 | ||
bd98c813 | 1196 | mark_func_jump_tables(file, func); |
e7c2bc37 | 1197 | ret = add_func_jump_tables(file, func); |
dcc914f4 JP |
1198 | if (ret) |
1199 | return ret; | |
1200 | } | |
1201 | } | |
1202 | ||
1203 | return 0; | |
1204 | } | |
1205 | ||
39358a03 JP |
1206 | static int read_unwind_hints(struct objtool_file *file) |
1207 | { | |
1208 | struct section *sec, *relasec; | |
1209 | struct rela *rela; | |
1210 | struct unwind_hint *hint; | |
1211 | struct instruction *insn; | |
1212 | struct cfi_reg *cfa; | |
1213 | int i; | |
1214 | ||
1215 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1216 | if (!sec) | |
1217 | return 0; | |
1218 | ||
1219 | relasec = sec->rela; | |
1220 | if (!relasec) { | |
1221 | WARN("missing .rela.discard.unwind_hints section"); | |
1222 | return -1; | |
1223 | } | |
1224 | ||
1225 | if (sec->len % sizeof(struct unwind_hint)) { | |
1226 | WARN("struct unwind_hint size mismatch"); | |
1227 | return -1; | |
1228 | } | |
1229 | ||
1230 | file->hints = true; | |
1231 | ||
1232 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1233 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1234 | ||
8b5fa6bc | 1235 | rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint)); |
39358a03 JP |
1236 | if (!rela) { |
1237 | WARN("can't find rela for unwind_hints[%d]", i); | |
1238 | return -1; | |
1239 | } | |
1240 | ||
1241 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1242 | if (!insn) { | |
1243 | WARN("can't find insn for unwind_hints[%d]", i); | |
1244 | return -1; | |
1245 | } | |
1246 | ||
1247 | cfa = &insn->state.cfa; | |
1248 | ||
1249 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1250 | insn->save = true; | |
1251 | continue; | |
1252 | ||
1253 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1254 | insn->restore = true; | |
1255 | insn->hint = true; | |
1256 | continue; | |
1257 | } | |
1258 | ||
1259 | insn->hint = true; | |
1260 | ||
1261 | switch (hint->sp_reg) { | |
1262 | case ORC_REG_UNDEFINED: | |
1263 | cfa->base = CFI_UNDEFINED; | |
1264 | break; | |
1265 | case ORC_REG_SP: | |
1266 | cfa->base = CFI_SP; | |
1267 | break; | |
1268 | case ORC_REG_BP: | |
1269 | cfa->base = CFI_BP; | |
1270 | break; | |
1271 | case ORC_REG_SP_INDIRECT: | |
1272 | cfa->base = CFI_SP_INDIRECT; | |
1273 | break; | |
1274 | case ORC_REG_R10: | |
1275 | cfa->base = CFI_R10; | |
1276 | break; | |
1277 | case ORC_REG_R13: | |
1278 | cfa->base = CFI_R13; | |
1279 | break; | |
1280 | case ORC_REG_DI: | |
1281 | cfa->base = CFI_DI; | |
1282 | break; | |
1283 | case ORC_REG_DX: | |
1284 | cfa->base = CFI_DX; | |
1285 | break; | |
1286 | default: | |
1287 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1288 | insn->sec, insn->offset, hint->sp_reg); | |
1289 | return -1; | |
1290 | } | |
1291 | ||
1292 | cfa->offset = hint->sp_offset; | |
1293 | insn->state.type = hint->type; | |
d31a5802 | 1294 | insn->state.end = hint->end; |
39358a03 JP |
1295 | } |
1296 | ||
1297 | return 0; | |
1298 | } | |
1299 | ||
b5bc2231 PZ |
1300 | static int read_retpoline_hints(struct objtool_file *file) |
1301 | { | |
63474dc4 | 1302 | struct section *sec; |
b5bc2231 PZ |
1303 | struct instruction *insn; |
1304 | struct rela *rela; | |
b5bc2231 | 1305 | |
63474dc4 | 1306 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
b5bc2231 PZ |
1307 | if (!sec) |
1308 | return 0; | |
1309 | ||
63474dc4 JP |
1310 | list_for_each_entry(rela, &sec->rela_list, list) { |
1311 | if (rela->sym->type != STT_SECTION) { | |
1312 | WARN("unexpected relocation symbol type in %s", sec->name); | |
b5bc2231 PZ |
1313 | return -1; |
1314 | } | |
1315 | ||
1316 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1317 | if (!insn) { | |
63474dc4 | 1318 | WARN("bad .discard.retpoline_safe entry"); |
b5bc2231 PZ |
1319 | return -1; |
1320 | } | |
1321 | ||
1322 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1323 | insn->type != INSN_CALL_DYNAMIC) { | |
63474dc4 | 1324 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
b5bc2231 PZ |
1325 | insn->sec, insn->offset); |
1326 | return -1; | |
1327 | } | |
1328 | ||
1329 | insn->retpoline_safe = true; | |
1330 | } | |
1331 | ||
1332 | return 0; | |
1333 | } | |
1334 | ||
4a60aa05 AX |
1335 | static void mark_rodata(struct objtool_file *file) |
1336 | { | |
1337 | struct section *sec; | |
1338 | bool found = false; | |
1339 | ||
1340 | /* | |
87b512de JP |
1341 | * Search for the following rodata sections, each of which can |
1342 | * potentially contain jump tables: | |
1343 | * | |
1344 | * - .rodata: can contain GCC switch tables | |
1345 | * - .rodata.<func>: same, if -fdata-sections is being used | |
1346 | * - .rodata..c_jump_table: contains C annotated jump tables | |
1347 | * | |
1348 | * .rodata.str1.* sections are ignored; they don't contain jump tables. | |
4a60aa05 AX |
1349 | */ |
1350 | for_each_sec(file, sec) { | |
87b512de JP |
1351 | if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) || |
1352 | !strcmp(sec->name, C_JUMP_TABLE_SECTION)) { | |
4a60aa05 AX |
1353 | sec->rodata = true; |
1354 | found = true; | |
1355 | } | |
1356 | } | |
1357 | ||
1358 | file->rodata = found; | |
1359 | } | |
1360 | ||
dcc914f4 JP |
1361 | static int decode_sections(struct objtool_file *file) |
1362 | { | |
1363 | int ret; | |
1364 | ||
4a60aa05 AX |
1365 | mark_rodata(file); |
1366 | ||
dcc914f4 JP |
1367 | ret = decode_instructions(file); |
1368 | if (ret) | |
1369 | return ret; | |
1370 | ||
1371 | ret = add_dead_ends(file); | |
1372 | if (ret) | |
1373 | return ret; | |
1374 | ||
1375 | add_ignores(file); | |
ea24213d | 1376 | add_uaccess_safe(file); |
dcc914f4 | 1377 | |
ff05ab23 | 1378 | ret = add_ignore_alternatives(file); |
258c7605 JP |
1379 | if (ret) |
1380 | return ret; | |
1381 | ||
dcc914f4 JP |
1382 | ret = add_jump_destinations(file); |
1383 | if (ret) | |
1384 | return ret; | |
1385 | ||
a845c7cf | 1386 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1387 | if (ret) |
1388 | return ret; | |
1389 | ||
a845c7cf | 1390 | ret = add_call_destinations(file); |
dcc914f4 JP |
1391 | if (ret) |
1392 | return ret; | |
1393 | ||
e7c2bc37 | 1394 | ret = add_jump_table_alts(file); |
dcc914f4 JP |
1395 | if (ret) |
1396 | return ret; | |
1397 | ||
39358a03 JP |
1398 | ret = read_unwind_hints(file); |
1399 | if (ret) | |
1400 | return ret; | |
1401 | ||
b5bc2231 PZ |
1402 | ret = read_retpoline_hints(file); |
1403 | if (ret) | |
1404 | return ret; | |
1405 | ||
dcc914f4 JP |
1406 | return 0; |
1407 | } | |
1408 | ||
1409 | static bool is_fentry_call(struct instruction *insn) | |
1410 | { | |
1411 | if (insn->type == INSN_CALL && | |
1412 | insn->call_dest->type == STT_NOTYPE && | |
1413 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1414 | return true; | |
1415 | ||
1416 | return false; | |
1417 | } | |
1418 | ||
baa41469 | 1419 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1420 | { |
baa41469 JP |
1421 | int i; |
1422 | ||
1423 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1424 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1425 | state->stack_size != initial_func_cfi.cfa.offset || | |
1426 | state->drap) | |
1427 | return true; | |
1428 | ||
1429 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1430 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1431 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1432 | return true; | |
1433 | ||
1434 | return false; | |
1435 | } | |
1436 | ||
1437 | static bool has_valid_stack_frame(struct insn_state *state) | |
1438 | { | |
1439 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1440 | state->regs[CFI_BP].offset == -16) | |
1441 | return true; | |
1442 | ||
1443 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1444 | return true; | |
1445 | ||
1446 | return false; | |
dcc914f4 JP |
1447 | } |
1448 | ||
627fce14 JP |
1449 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1450 | { | |
1451 | struct cfi_reg *cfa = &state->cfa; | |
1452 | struct stack_op *op = &insn->stack_op; | |
1453 | ||
1454 | if (cfa->base != CFI_SP) | |
1455 | return 0; | |
1456 | ||
1457 | /* push */ | |
ea24213d | 1458 | if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) |
627fce14 JP |
1459 | cfa->offset += 8; |
1460 | ||
1461 | /* pop */ | |
ea24213d | 1462 | if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) |
627fce14 JP |
1463 | cfa->offset -= 8; |
1464 | ||
1465 | /* add immediate to sp */ | |
1466 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1467 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1468 | cfa->offset -= op->src.offset; | |
1469 | ||
1470 | return 0; | |
1471 | } | |
1472 | ||
baa41469 JP |
1473 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1474 | int offset) | |
dcc914f4 | 1475 | { |
bf4d1a83 | 1476 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1477 | state->regs[reg].base == CFI_UNDEFINED) { |
1478 | state->regs[reg].base = base; | |
1479 | state->regs[reg].offset = offset; | |
1480 | } | |
dcc914f4 JP |
1481 | } |
1482 | ||
baa41469 | 1483 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1484 | { |
baa41469 JP |
1485 | state->regs[reg].base = CFI_UNDEFINED; |
1486 | state->regs[reg].offset = 0; | |
1487 | } | |
1488 | ||
1489 | /* | |
1490 | * A note about DRAP stack alignment: | |
1491 | * | |
1492 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1493 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1494 | * register. The typical DRAP pattern is: | |
1495 | * | |
1496 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1497 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1498 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1499 | * 55 push %rbp | |
1500 | * 48 89 e5 mov %rsp,%rbp | |
1501 | * (more pushes) | |
1502 | * 41 52 push %r10 | |
1503 | * ... | |
1504 | * 41 5a pop %r10 | |
1505 | * (more pops) | |
1506 | * 5d pop %rbp | |
1507 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1508 | * c3 retq | |
1509 | * | |
1510 | * There are some variations in the epilogues, like: | |
1511 | * | |
1512 | * 5b pop %rbx | |
1513 | * 41 5a pop %r10 | |
1514 | * 41 5c pop %r12 | |
1515 | * 41 5d pop %r13 | |
1516 | * 41 5e pop %r14 | |
1517 | * c9 leaveq | |
1518 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1519 | * c3 retq | |
1520 | * | |
1521 | * and: | |
1522 | * | |
1523 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1524 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1525 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1526 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1527 | * c9 leaveq | |
1528 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1529 | * c3 retq | |
1530 | * | |
1531 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1532 | * restored beforehand: | |
1533 | * | |
1534 | * 41 55 push %r13 | |
1535 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1536 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1537 | * ... | |
1538 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1539 | * 41 5d pop %r13 | |
1540 | * c3 retq | |
1541 | */ | |
1542 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1543 | { | |
1544 | struct stack_op *op = &insn->stack_op; | |
1545 | struct cfi_reg *cfa = &state->cfa; | |
1546 | struct cfi_reg *regs = state->regs; | |
1547 | ||
1548 | /* stack operations don't make sense with an undefined CFA */ | |
1549 | if (cfa->base == CFI_UNDEFINED) { | |
1550 | if (insn->func) { | |
1551 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1552 | return -1; | |
1553 | } | |
1554 | return 0; | |
1555 | } | |
1556 | ||
627fce14 JP |
1557 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1558 | return update_insn_state_regs(insn, state); | |
1559 | ||
baa41469 JP |
1560 | switch (op->dest.type) { |
1561 | ||
1562 | case OP_DEST_REG: | |
1563 | switch (op->src.type) { | |
1564 | ||
1565 | case OP_SRC_REG: | |
0d0970ee JP |
1566 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1567 | cfa->base == CFI_SP && | |
1568 | regs[CFI_BP].base == CFI_CFA && | |
1569 | regs[CFI_BP].offset == -cfa->offset) { | |
1570 | ||
1571 | /* mov %rsp, %rbp */ | |
1572 | cfa->base = op->dest.reg; | |
1573 | state->bp_scratch = false; | |
1574 | } | |
dd88a0a0 | 1575 | |
0d0970ee JP |
1576 | else if (op->src.reg == CFI_SP && |
1577 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1578 | |
0d0970ee JP |
1579 | /* drap: mov %rsp, %rbp */ |
1580 | regs[CFI_BP].base = CFI_BP; | |
1581 | regs[CFI_BP].offset = -state->stack_size; | |
1582 | state->bp_scratch = false; | |
1583 | } | |
dd88a0a0 | 1584 | |
0d0970ee JP |
1585 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1586 | ||
1587 | /* | |
1588 | * mov %rsp, %reg | |
1589 | * | |
1590 | * This is needed for the rare case where GCC | |
1591 | * does: | |
1592 | * | |
1593 | * mov %rsp, %rax | |
1594 | * ... | |
1595 | * mov %rax, %rsp | |
1596 | */ | |
1597 | state->vals[op->dest.reg].base = CFI_CFA; | |
1598 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1599 | } |
1600 | ||
3c1f0583 JP |
1601 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
1602 | cfa->base == CFI_BP) { | |
1603 | ||
1604 | /* | |
1605 | * mov %rbp, %rsp | |
1606 | * | |
1607 | * Restore the original stack pointer (Clang). | |
1608 | */ | |
1609 | state->stack_size = -state->regs[CFI_BP].offset; | |
1610 | } | |
1611 | ||
dd88a0a0 JP |
1612 | else if (op->dest.reg == cfa->base) { |
1613 | ||
1614 | /* mov %reg, %rsp */ | |
1615 | if (cfa->base == CFI_SP && | |
1616 | state->vals[op->src.reg].base == CFI_CFA) { | |
1617 | ||
1618 | /* | |
1619 | * This is needed for the rare case | |
1620 | * where GCC does something dumb like: | |
1621 | * | |
1622 | * lea 0x8(%rsp), %rcx | |
1623 | * ... | |
1624 | * mov %rcx, %rsp | |
1625 | */ | |
1626 | cfa->offset = -state->vals[op->src.reg].offset; | |
1627 | state->stack_size = cfa->offset; | |
1628 | ||
1629 | } else { | |
1630 | cfa->base = CFI_UNDEFINED; | |
1631 | cfa->offset = 0; | |
1632 | } | |
baa41469 JP |
1633 | } |
1634 | ||
1635 | break; | |
1636 | ||
1637 | case OP_SRC_ADD: | |
1638 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1639 | ||
1640 | /* add imm, %rsp */ | |
1641 | state->stack_size -= op->src.offset; | |
1642 | if (cfa->base == CFI_SP) | |
1643 | cfa->offset -= op->src.offset; | |
1644 | break; | |
1645 | } | |
1646 | ||
1647 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1648 | ||
1649 | /* lea disp(%rbp), %rsp */ | |
1650 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1651 | break; | |
1652 | } | |
1653 | ||
dd88a0a0 | 1654 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1655 | |
1656 | /* drap: lea disp(%rsp), %drap */ | |
1657 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1658 | |
1659 | /* | |
1660 | * lea disp(%rsp), %reg | |
1661 | * | |
1662 | * This is needed for the rare case where GCC | |
1663 | * does something dumb like: | |
1664 | * | |
1665 | * lea 0x8(%rsp), %rcx | |
1666 | * ... | |
1667 | * mov %rcx, %rsp | |
1668 | */ | |
1669 | state->vals[op->dest.reg].base = CFI_CFA; | |
1670 | state->vals[op->dest.reg].offset = \ | |
1671 | -state->stack_size + op->src.offset; | |
1672 | ||
baa41469 JP |
1673 | break; |
1674 | } | |
1675 | ||
1676 | if (state->drap && op->dest.reg == CFI_SP && | |
1677 | op->src.reg == state->drap_reg) { | |
1678 | ||
1679 | /* drap: lea disp(%drap), %rsp */ | |
1680 | cfa->base = CFI_SP; | |
1681 | cfa->offset = state->stack_size = -op->src.offset; | |
1682 | state->drap_reg = CFI_UNDEFINED; | |
1683 | state->drap = false; | |
1684 | break; | |
1685 | } | |
1686 | ||
1687 | if (op->dest.reg == state->cfa.base) { | |
1688 | WARN_FUNC("unsupported stack register modification", | |
1689 | insn->sec, insn->offset); | |
1690 | return -1; | |
1691 | } | |
1692 | ||
1693 | break; | |
1694 | ||
1695 | case OP_SRC_AND: | |
1696 | if (op->dest.reg != CFI_SP || | |
1697 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1698 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1699 | WARN_FUNC("unsupported stack pointer realignment", | |
1700 | insn->sec, insn->offset); | |
1701 | return -1; | |
1702 | } | |
1703 | ||
1704 | if (state->drap_reg != CFI_UNDEFINED) { | |
1705 | /* drap: and imm, %rsp */ | |
1706 | cfa->base = state->drap_reg; | |
1707 | cfa->offset = state->stack_size = 0; | |
1708 | state->drap = true; | |
baa41469 JP |
1709 | } |
1710 | ||
1711 | /* | |
1712 | * Older versions of GCC (4.8ish) realign the stack | |
1713 | * without DRAP, with a frame pointer. | |
1714 | */ | |
1715 | ||
1716 | break; | |
1717 | ||
1718 | case OP_SRC_POP: | |
ea24213d | 1719 | case OP_SRC_POPF: |
baa41469 JP |
1720 | if (!state->drap && op->dest.type == OP_DEST_REG && |
1721 | op->dest.reg == cfa->base) { | |
1722 | ||
1723 | /* pop %rbp */ | |
1724 | cfa->base = CFI_SP; | |
1725 | } | |
1726 | ||
bf4d1a83 JP |
1727 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1728 | op->dest.type == OP_DEST_REG && | |
1729 | op->dest.reg == state->drap_reg && | |
1730 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1731 | |
bf4d1a83 JP |
1732 | /* drap: pop %drap */ |
1733 | cfa->base = state->drap_reg; | |
1734 | cfa->offset = 0; | |
1735 | state->drap_offset = -1; | |
baa41469 | 1736 | |
bf4d1a83 | 1737 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1738 | |
bf4d1a83 | 1739 | /* pop %reg */ |
baa41469 JP |
1740 | restore_reg(state, op->dest.reg); |
1741 | } | |
1742 | ||
1743 | state->stack_size -= 8; | |
1744 | if (cfa->base == CFI_SP) | |
1745 | cfa->offset -= 8; | |
1746 | ||
1747 | break; | |
1748 | ||
1749 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1750 | if (state->drap && op->src.reg == CFI_BP && |
1751 | op->src.offset == state->drap_offset) { | |
1752 | ||
1753 | /* drap: mov disp(%rbp), %drap */ | |
1754 | cfa->base = state->drap_reg; | |
1755 | cfa->offset = 0; | |
1756 | state->drap_offset = -1; | |
1757 | } | |
1758 | ||
baa41469 JP |
1759 | if (state->drap && op->src.reg == CFI_BP && |
1760 | op->src.offset == regs[op->dest.reg].offset) { | |
1761 | ||
1762 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1763 | restore_reg(state, op->dest.reg); |
1764 | ||
1765 | } else if (op->src.reg == cfa->base && | |
1766 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1767 | ||
1768 | /* mov disp(%rbp), %reg */ | |
1769 | /* mov disp(%rsp), %reg */ | |
1770 | restore_reg(state, op->dest.reg); | |
1771 | } | |
1772 | ||
1773 | break; | |
1774 | ||
1775 | default: | |
1776 | WARN_FUNC("unknown stack-related instruction", | |
1777 | insn->sec, insn->offset); | |
1778 | return -1; | |
1779 | } | |
1780 | ||
1781 | break; | |
1782 | ||
1783 | case OP_DEST_PUSH: | |
ea24213d | 1784 | case OP_DEST_PUSHF: |
baa41469 JP |
1785 | state->stack_size += 8; |
1786 | if (cfa->base == CFI_SP) | |
1787 | cfa->offset += 8; | |
1788 | ||
1789 | if (op->src.type != OP_SRC_REG) | |
1790 | break; | |
1791 | ||
1792 | if (state->drap) { | |
1793 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1794 | ||
1795 | /* drap: push %drap */ | |
1796 | cfa->base = CFI_BP_INDIRECT; | |
1797 | cfa->offset = -state->stack_size; | |
1798 | ||
bf4d1a83 JP |
1799 | /* save drap so we know when to restore it */ |
1800 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1801 | |
1802 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1803 | ||
1804 | /* drap: push %rbp */ | |
1805 | state->stack_size = 0; | |
1806 | ||
1807 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1808 | ||
1809 | /* drap: push %reg */ | |
1810 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1811 | } | |
1812 | ||
1813 | } else { | |
1814 | ||
1815 | /* push %reg */ | |
1816 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1817 | } | |
1818 | ||
1819 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1820 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1821 | cfa->base != CFI_BP) |
1822 | state->bp_scratch = true; | |
1823 | break; | |
1824 | ||
1825 | case OP_DEST_REG_INDIRECT: | |
1826 | ||
1827 | if (state->drap) { | |
1828 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1829 | ||
1830 | /* drap: mov %drap, disp(%rbp) */ | |
1831 | cfa->base = CFI_BP_INDIRECT; | |
1832 | cfa->offset = op->dest.offset; | |
1833 | ||
bf4d1a83 JP |
1834 | /* save drap offset so we know when to restore it */ |
1835 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1836 | } |
1837 | ||
1838 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1839 | ||
1840 | /* drap: mov reg, disp(%rbp) */ | |
1841 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1842 | } | |
1843 | ||
1844 | } else if (op->dest.reg == cfa->base) { | |
1845 | ||
1846 | /* mov reg, disp(%rbp) */ | |
1847 | /* mov reg, disp(%rsp) */ | |
1848 | save_reg(state, op->src.reg, CFI_CFA, | |
1849 | op->dest.offset - state->cfa.offset); | |
1850 | } | |
1851 | ||
1852 | break; | |
1853 | ||
1854 | case OP_DEST_LEAVE: | |
1855 | if ((!state->drap && cfa->base != CFI_BP) || | |
1856 | (state->drap && cfa->base != state->drap_reg)) { | |
1857 | WARN_FUNC("leave instruction with modified stack frame", | |
1858 | insn->sec, insn->offset); | |
1859 | return -1; | |
1860 | } | |
1861 | ||
1862 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1863 | ||
1864 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1865 | restore_reg(state, CFI_BP); | |
1866 | ||
1867 | if (!state->drap) { | |
1868 | cfa->base = CFI_SP; | |
1869 | cfa->offset -= 8; | |
1870 | } | |
1871 | ||
1872 | break; | |
1873 | ||
1874 | case OP_DEST_MEM: | |
ea24213d | 1875 | if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { |
baa41469 JP |
1876 | WARN_FUNC("unknown stack-related memory operation", |
1877 | insn->sec, insn->offset); | |
1878 | return -1; | |
1879 | } | |
1880 | ||
1881 | /* pop mem */ | |
1882 | state->stack_size -= 8; | |
1883 | if (cfa->base == CFI_SP) | |
1884 | cfa->offset -= 8; | |
1885 | ||
1886 | break; | |
1887 | ||
1888 | default: | |
1889 | WARN_FUNC("unknown stack-related instruction", | |
1890 | insn->sec, insn->offset); | |
1891 | return -1; | |
1892 | } | |
1893 | ||
1894 | return 0; | |
1895 | } | |
1896 | ||
1897 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1898 | { | |
1899 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1900 | int i; | |
1901 | ||
1902 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1903 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1904 | insn->sec, insn->offset, | |
1905 | state1->cfa.base, state1->cfa.offset, | |
1906 | state2->cfa.base, state2->cfa.offset); | |
1907 | ||
1908 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1909 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1910 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1911 | sizeof(struct cfi_reg))) | |
1912 | continue; | |
1913 | ||
1914 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1915 | insn->sec, insn->offset, | |
1916 | i, state1->regs[i].base, state1->regs[i].offset, | |
1917 | i, state2->regs[i].base, state2->regs[i].offset); | |
1918 | break; | |
1919 | } | |
1920 | ||
627fce14 JP |
1921 | } else if (state1->type != state2->type) { |
1922 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1923 | insn->sec, insn->offset, state1->type, state2->type); | |
1924 | ||
baa41469 | 1925 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1926 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1927 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1928 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1929 | insn->sec, insn->offset, |
bf4d1a83 JP |
1930 | state1->drap, state1->drap_reg, state1->drap_offset, |
1931 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1932 | |
1933 | } else | |
1934 | return true; | |
1935 | ||
1936 | return false; | |
dcc914f4 JP |
1937 | } |
1938 | ||
ea24213d PZ |
1939 | static inline bool func_uaccess_safe(struct symbol *func) |
1940 | { | |
1941 | if (func) | |
e10cd8fe | 1942 | return func->uaccess_safe; |
ea24213d PZ |
1943 | |
1944 | return false; | |
1945 | } | |
1946 | ||
0c1ddd33 | 1947 | static inline const char *call_dest_name(struct instruction *insn) |
ea24213d PZ |
1948 | { |
1949 | if (insn->call_dest) | |
1950 | return insn->call_dest->name; | |
1951 | ||
1952 | return "{dynamic}"; | |
1953 | } | |
1954 | ||
1955 | static int validate_call(struct instruction *insn, struct insn_state *state) | |
1956 | { | |
1957 | if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { | |
1958 | WARN_FUNC("call to %s() with UACCESS enabled", | |
0c1ddd33 | 1959 | insn->sec, insn->offset, call_dest_name(insn)); |
ea24213d PZ |
1960 | return 1; |
1961 | } | |
1962 | ||
2f0f9e9a PZ |
1963 | if (state->df) { |
1964 | WARN_FUNC("call to %s() with DF set", | |
0c1ddd33 | 1965 | insn->sec, insn->offset, call_dest_name(insn)); |
2f0f9e9a PZ |
1966 | return 1; |
1967 | } | |
1968 | ||
ea24213d PZ |
1969 | return 0; |
1970 | } | |
1971 | ||
54262aa2 PZ |
1972 | static int validate_sibling_call(struct instruction *insn, struct insn_state *state) |
1973 | { | |
1974 | if (has_modified_stack_frame(state)) { | |
1975 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
1976 | insn->sec, insn->offset); | |
1977 | return 1; | |
1978 | } | |
1979 | ||
ea24213d | 1980 | return validate_call(insn, state); |
54262aa2 PZ |
1981 | } |
1982 | ||
a92e92d1 PZ |
1983 | static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) |
1984 | { | |
1985 | if (state->uaccess && !func_uaccess_safe(func)) { | |
1986 | WARN_FUNC("return with UACCESS enabled", | |
1987 | insn->sec, insn->offset); | |
1988 | return 1; | |
1989 | } | |
1990 | ||
1991 | if (!state->uaccess && func_uaccess_safe(func)) { | |
1992 | WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", | |
1993 | insn->sec, insn->offset); | |
1994 | return 1; | |
1995 | } | |
1996 | ||
1997 | if (state->df) { | |
1998 | WARN_FUNC("return with DF set", | |
1999 | insn->sec, insn->offset); | |
2000 | return 1; | |
2001 | } | |
2002 | ||
2003 | if (func && has_modified_stack_frame(state)) { | |
2004 | WARN_FUNC("return with modified stack frame", | |
2005 | insn->sec, insn->offset); | |
2006 | return 1; | |
2007 | } | |
2008 | ||
2009 | if (state->bp_scratch) { | |
2010 | WARN("%s uses BP as a scratch register", | |
2011 | func->name); | |
2012 | return 1; | |
2013 | } | |
2014 | ||
2015 | return 0; | |
2016 | } | |
2017 | ||
dcc914f4 JP |
2018 | /* |
2019 | * Follow the branch starting at the given instruction, and recursively follow | |
2020 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
2021 | * each instruction and validate all the rules described in | |
2022 | * tools/objtool/Documentation/stack-validation.txt. | |
2023 | */ | |
c705cecc JP |
2024 | static int validate_branch(struct objtool_file *file, struct symbol *func, |
2025 | struct instruction *first, struct insn_state state) | |
dcc914f4 JP |
2026 | { |
2027 | struct alternative *alt; | |
39358a03 | 2028 | struct instruction *insn, *next_insn; |
dcc914f4 | 2029 | struct section *sec; |
882a0db9 | 2030 | u8 visited; |
dcc914f4 JP |
2031 | int ret; |
2032 | ||
2033 | insn = first; | |
2034 | sec = insn->sec; | |
dcc914f4 JP |
2035 | |
2036 | if (insn->alt_group && list_empty(&insn->alts)) { | |
2037 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
2038 | sec, insn->offset); | |
12b25729 | 2039 | return 1; |
dcc914f4 JP |
2040 | } |
2041 | ||
2042 | while (1) { | |
39358a03 JP |
2043 | next_insn = next_insn_same_sec(file, insn); |
2044 | ||
13810435 | 2045 | if (file->c_file && func && insn->func && func != insn->func->pfunc) { |
ee97638b JP |
2046 | WARN("%s() falls through to next function %s()", |
2047 | func->name, insn->func->name); | |
2048 | return 1; | |
dcc914f4 JP |
2049 | } |
2050 | ||
4855022a JP |
2051 | if (func && insn->ignore) { |
2052 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
2053 | sec, insn->offset); | |
12b25729 | 2054 | return 1; |
4855022a JP |
2055 | } |
2056 | ||
882a0db9 | 2057 | visited = 1 << state.uaccess; |
dcc914f4 | 2058 | if (insn->visited) { |
39358a03 | 2059 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 2060 | return 1; |
dcc914f4 | 2061 | |
882a0db9 | 2062 | if (insn->visited & visited) |
ea24213d | 2063 | return 0; |
dcc914f4 JP |
2064 | } |
2065 | ||
39358a03 JP |
2066 | if (insn->hint) { |
2067 | if (insn->restore) { | |
2068 | struct instruction *save_insn, *i; | |
2069 | ||
2070 | i = insn; | |
2071 | save_insn = NULL; | |
dbf4aeb0 | 2072 | sym_for_each_insn_continue_reverse(file, func, i) { |
39358a03 JP |
2073 | if (i->save) { |
2074 | save_insn = i; | |
2075 | break; | |
2076 | } | |
2077 | } | |
2078 | ||
2079 | if (!save_insn) { | |
2080 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
2081 | sec, insn->offset); | |
2082 | return 1; | |
2083 | } | |
2084 | ||
2085 | if (!save_insn->visited) { | |
2086 | /* | |
2087 | * Oops, no state to copy yet. | |
2088 | * Hopefully we can reach this | |
2089 | * instruction from another branch | |
2090 | * after the save insn has been | |
2091 | * visited. | |
2092 | */ | |
2093 | if (insn == first) | |
2094 | return 0; | |
2095 | ||
2096 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
2097 | sec, insn->offset); | |
2098 | return 1; | |
2099 | } | |
2100 | ||
2101 | insn->state = save_insn->state; | |
2102 | } | |
2103 | ||
2104 | state = insn->state; | |
2105 | ||
2106 | } else | |
2107 | insn->state = state; | |
dcc914f4 | 2108 | |
882a0db9 | 2109 | insn->visited |= visited; |
baa41469 | 2110 | |
a845c7cf | 2111 | if (!insn->ignore_alts) { |
764eef4b PZ |
2112 | bool skip_orig = false; |
2113 | ||
a845c7cf | 2114 | list_for_each_entry(alt, &insn->alts, list) { |
764eef4b PZ |
2115 | if (alt->skip_orig) |
2116 | skip_orig = true; | |
2117 | ||
c705cecc | 2118 | ret = validate_branch(file, func, alt->insn, state); |
7697eee3 PZ |
2119 | if (ret) { |
2120 | if (backtrace) | |
2121 | BT_FUNC("(alt)", insn); | |
2122 | return ret; | |
2123 | } | |
a845c7cf | 2124 | } |
764eef4b PZ |
2125 | |
2126 | if (skip_orig) | |
2127 | return 0; | |
dcc914f4 JP |
2128 | } |
2129 | ||
2130 | switch (insn->type) { | |
2131 | ||
dcc914f4 | 2132 | case INSN_RETURN: |
a92e92d1 | 2133 | return validate_return(func, insn, &state); |
dcc914f4 JP |
2134 | |
2135 | case INSN_CALL: | |
ea24213d PZ |
2136 | case INSN_CALL_DYNAMIC: |
2137 | ret = validate_call(insn, &state); | |
2138 | if (ret) | |
2139 | return ret; | |
dcc914f4 | 2140 | |
c9bab22b JP |
2141 | if (!no_fp && func && !is_fentry_call(insn) && |
2142 | !has_valid_stack_frame(&state)) { | |
dcc914f4 JP |
2143 | WARN_FUNC("call without frame pointer save/setup", |
2144 | sec, insn->offset); | |
2145 | return 1; | |
2146 | } | |
c9bab22b JP |
2147 | |
2148 | if (dead_end_function(file, insn->call_dest)) | |
2149 | return 0; | |
2150 | ||
dcc914f4 JP |
2151 | break; |
2152 | ||
2153 | case INSN_JUMP_CONDITIONAL: | |
2154 | case INSN_JUMP_UNCONDITIONAL: | |
0c1ddd33 | 2155 | if (func && is_sibling_call(insn)) { |
54262aa2 | 2156 | ret = validate_sibling_call(insn, &state); |
dcc914f4 | 2157 | if (ret) |
54262aa2 | 2158 | return ret; |
4855022a | 2159 | |
0c1ddd33 | 2160 | } else if (insn->jump_dest) { |
c705cecc JP |
2161 | ret = validate_branch(file, func, |
2162 | insn->jump_dest, state); | |
7697eee3 PZ |
2163 | if (ret) { |
2164 | if (backtrace) | |
2165 | BT_FUNC("(branch)", insn); | |
2166 | return ret; | |
2167 | } | |
4855022a | 2168 | } |
dcc914f4 JP |
2169 | |
2170 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
2171 | return 0; | |
2172 | ||
2173 | break; | |
2174 | ||
2175 | case INSN_JUMP_DYNAMIC: | |
b68b9907 | 2176 | case INSN_JUMP_DYNAMIC_CONDITIONAL: |
0c1ddd33 | 2177 | if (func && is_sibling_call(insn)) { |
54262aa2 PZ |
2178 | ret = validate_sibling_call(insn, &state); |
2179 | if (ret) | |
2180 | return ret; | |
dcc914f4 JP |
2181 | } |
2182 | ||
b68b9907 JP |
2183 | if (insn->type == INSN_JUMP_DYNAMIC) |
2184 | return 0; | |
2185 | ||
2186 | break; | |
dcc914f4 | 2187 | |
39358a03 JP |
2188 | case INSN_CONTEXT_SWITCH: |
2189 | if (func && (!next_insn || !next_insn->hint)) { | |
2190 | WARN_FUNC("unsupported instruction in callable function", | |
2191 | sec, insn->offset); | |
2192 | return 1; | |
2193 | } | |
2194 | return 0; | |
2195 | ||
baa41469 JP |
2196 | case INSN_STACK: |
2197 | if (update_insn_state(insn, &state)) | |
12b25729 | 2198 | return 1; |
baa41469 | 2199 | |
ea24213d PZ |
2200 | if (insn->stack_op.dest.type == OP_DEST_PUSHF) { |
2201 | if (!state.uaccess_stack) { | |
2202 | state.uaccess_stack = 1; | |
2203 | } else if (state.uaccess_stack >> 31) { | |
2204 | WARN_FUNC("PUSHF stack exhausted", sec, insn->offset); | |
2205 | return 1; | |
2206 | } | |
2207 | state.uaccess_stack <<= 1; | |
2208 | state.uaccess_stack |= state.uaccess; | |
2209 | } | |
2210 | ||
2211 | if (insn->stack_op.src.type == OP_SRC_POPF) { | |
2212 | if (state.uaccess_stack) { | |
2213 | state.uaccess = state.uaccess_stack & 1; | |
2214 | state.uaccess_stack >>= 1; | |
2215 | if (state.uaccess_stack == 1) | |
2216 | state.uaccess_stack = 0; | |
2217 | } | |
2218 | } | |
2219 | ||
2220 | break; | |
2221 | ||
2222 | case INSN_STAC: | |
2223 | if (state.uaccess) { | |
2224 | WARN_FUNC("recursive UACCESS enable", sec, insn->offset); | |
2225 | return 1; | |
2226 | } | |
2227 | ||
2228 | state.uaccess = true; | |
2229 | break; | |
2230 | ||
2231 | case INSN_CLAC: | |
c705cecc | 2232 | if (!state.uaccess && func) { |
ea24213d PZ |
2233 | WARN_FUNC("redundant UACCESS disable", sec, insn->offset); |
2234 | return 1; | |
2235 | } | |
2236 | ||
2237 | if (func_uaccess_safe(func) && !state.uaccess_stack) { | |
2238 | WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); | |
2239 | return 1; | |
2240 | } | |
2241 | ||
2242 | state.uaccess = false; | |
baa41469 JP |
2243 | break; |
2244 | ||
2f0f9e9a PZ |
2245 | case INSN_STD: |
2246 | if (state.df) | |
2247 | WARN_FUNC("recursive STD", sec, insn->offset); | |
2248 | ||
2249 | state.df = true; | |
2250 | break; | |
2251 | ||
2252 | case INSN_CLD: | |
c705cecc | 2253 | if (!state.df && func) |
2f0f9e9a PZ |
2254 | WARN_FUNC("redundant CLD", sec, insn->offset); |
2255 | ||
2256 | state.df = false; | |
baa41469 JP |
2257 | break; |
2258 | ||
dcc914f4 JP |
2259 | default: |
2260 | break; | |
2261 | } | |
2262 | ||
2263 | if (insn->dead_end) | |
2264 | return 0; | |
2265 | ||
00d96180 JP |
2266 | if (!next_insn) { |
2267 | if (state.cfa.base == CFI_UNDEFINED) | |
2268 | return 0; | |
dcc914f4 JP |
2269 | WARN("%s: unexpected end of section", sec->name); |
2270 | return 1; | |
2271 | } | |
00d96180 JP |
2272 | |
2273 | insn = next_insn; | |
dcc914f4 JP |
2274 | } |
2275 | ||
2276 | return 0; | |
2277 | } | |
2278 | ||
39358a03 JP |
2279 | static int validate_unwind_hints(struct objtool_file *file) |
2280 | { | |
2281 | struct instruction *insn; | |
2282 | int ret, warnings = 0; | |
2283 | struct insn_state state; | |
2284 | ||
2285 | if (!file->hints) | |
2286 | return 0; | |
2287 | ||
2288 | clear_insn_state(&state); | |
2289 | ||
2290 | for_each_insn(file, insn) { | |
2291 | if (insn->hint && !insn->visited) { | |
c705cecc | 2292 | ret = validate_branch(file, insn->func, insn, state); |
7697eee3 PZ |
2293 | if (ret && backtrace) |
2294 | BT_FUNC("<=== (hint)", insn); | |
39358a03 JP |
2295 | warnings += ret; |
2296 | } | |
2297 | } | |
2298 | ||
2299 | return warnings; | |
2300 | } | |
2301 | ||
b5bc2231 PZ |
2302 | static int validate_retpoline(struct objtool_file *file) |
2303 | { | |
2304 | struct instruction *insn; | |
2305 | int warnings = 0; | |
2306 | ||
2307 | for_each_insn(file, insn) { | |
2308 | if (insn->type != INSN_JUMP_DYNAMIC && | |
2309 | insn->type != INSN_CALL_DYNAMIC) | |
2310 | continue; | |
2311 | ||
2312 | if (insn->retpoline_safe) | |
2313 | continue; | |
2314 | ||
ca41b97e PZ |
2315 | /* |
2316 | * .init.text code is ran before userspace and thus doesn't | |
2317 | * strictly need retpolines, except for modules which are | |
2318 | * loaded late, they very much do need retpoline in their | |
2319 | * .init.text | |
2320 | */ | |
2321 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
2322 | continue; | |
2323 | ||
b5bc2231 PZ |
2324 | WARN_FUNC("indirect %s found in RETPOLINE build", |
2325 | insn->sec, insn->offset, | |
2326 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
2327 | ||
2328 | warnings++; | |
2329 | } | |
2330 | ||
2331 | return warnings; | |
2332 | } | |
2333 | ||
dcc914f4 JP |
2334 | static bool is_kasan_insn(struct instruction *insn) |
2335 | { | |
2336 | return (insn->type == INSN_CALL && | |
2337 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
2338 | } | |
2339 | ||
2340 | static bool is_ubsan_insn(struct instruction *insn) | |
2341 | { | |
2342 | return (insn->type == INSN_CALL && | |
2343 | !strcmp(insn->call_dest->name, | |
2344 | "__ubsan_handle_builtin_unreachable")); | |
2345 | } | |
2346 | ||
baa41469 | 2347 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
2348 | { |
2349 | int i; | |
2350 | ||
baa41469 JP |
2351 | if (insn->ignore || insn->type == INSN_NOP) |
2352 | return true; | |
2353 | ||
2354 | /* | |
2355 | * Ignore any unused exceptions. This can happen when a whitelisted | |
2356 | * function has an exception table entry. | |
0e2bb2bc JP |
2357 | * |
2358 | * Also ignore alternative replacement instructions. This can happen | |
2359 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 2360 | */ |
0e2bb2bc JP |
2361 | if (!strcmp(insn->sec->name, ".fixup") || |
2362 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
2363 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2364 | return true; |
2365 | ||
2366 | /* | |
2367 | * Check if this (or a subsequent) instruction is related to | |
2368 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2369 | * | |
2370 | * End the search at 5 instructions to avoid going into the weeds. | |
2371 | */ | |
baa41469 JP |
2372 | if (!insn->func) |
2373 | return false; | |
dcc914f4 JP |
2374 | for (i = 0; i < 5; i++) { |
2375 | ||
2376 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2377 | return true; | |
2378 | ||
fe24e271 JP |
2379 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2380 | if (insn->jump_dest && | |
2381 | insn->jump_dest->func == insn->func) { | |
2382 | insn = insn->jump_dest; | |
2383 | continue; | |
2384 | } | |
2385 | ||
2386 | break; | |
dcc914f4 JP |
2387 | } |
2388 | ||
baa41469 | 2389 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2390 | break; |
fe24e271 | 2391 | |
dcc914f4 JP |
2392 | insn = list_next_entry(insn, list); |
2393 | } | |
2394 | ||
2395 | return false; | |
2396 | } | |
2397 | ||
2398 | static int validate_functions(struct objtool_file *file) | |
2399 | { | |
2400 | struct section *sec; | |
2401 | struct symbol *func; | |
2402 | struct instruction *insn; | |
baa41469 | 2403 | struct insn_state state; |
dcc914f4 JP |
2404 | int ret, warnings = 0; |
2405 | ||
baa41469 JP |
2406 | clear_insn_state(&state); |
2407 | ||
2408 | state.cfa = initial_func_cfi.cfa; | |
2409 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2410 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2411 | state.stack_size = initial_func_cfi.cfa.offset; | |
2412 | ||
2413 | for_each_sec(file, sec) { | |
dcc914f4 | 2414 | list_for_each_entry(func, &sec->symbol_list, list) { |
e10cd8fe JP |
2415 | if (func->type != STT_FUNC) |
2416 | continue; | |
2417 | ||
61e9b75a JP |
2418 | if (!func->len) { |
2419 | WARN("%s() is missing an ELF size annotation", | |
2420 | func->name); | |
2421 | warnings++; | |
2422 | } | |
2423 | ||
e10cd8fe | 2424 | if (func->pfunc != func || func->alias != func) |
dcc914f4 JP |
2425 | continue; |
2426 | ||
2427 | insn = find_insn(file, sec, func->offset); | |
c705cecc | 2428 | if (!insn || insn->ignore || insn->visited) |
dcc914f4 JP |
2429 | continue; |
2430 | ||
e10cd8fe | 2431 | state.uaccess = func->uaccess_safe; |
ea24213d | 2432 | |
c705cecc | 2433 | ret = validate_branch(file, func, insn, state); |
7697eee3 PZ |
2434 | if (ret && backtrace) |
2435 | BT_FUNC("<=== (func)", insn); | |
dcc914f4 JP |
2436 | warnings += ret; |
2437 | } | |
2438 | } | |
2439 | ||
dcc914f4 JP |
2440 | return warnings; |
2441 | } | |
2442 | ||
baa41469 | 2443 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2444 | { |
2445 | struct instruction *insn; | |
baa41469 JP |
2446 | |
2447 | if (file->ignore_unreachables) | |
2448 | return 0; | |
dcc914f4 JP |
2449 | |
2450 | for_each_insn(file, insn) { | |
baa41469 JP |
2451 | if (insn->visited || ignore_unreachable_insn(insn)) |
2452 | continue; | |
2453 | ||
baa41469 JP |
2454 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2455 | return 1; | |
dcc914f4 JP |
2456 | } |
2457 | ||
baa41469 | 2458 | return 0; |
dcc914f4 JP |
2459 | } |
2460 | ||
0c671812 JP |
2461 | static struct objtool_file file; |
2462 | ||
43a4525f | 2463 | int check(const char *_objname, bool orc) |
dcc914f4 | 2464 | { |
dcc914f4 JP |
2465 | int ret, warnings = 0; |
2466 | ||
2467 | objname = _objname; | |
dcc914f4 | 2468 | |
8e144797 | 2469 | file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2470 | if (!file.elf) |
dcc914f4 | 2471 | return 1; |
dcc914f4 JP |
2472 | |
2473 | INIT_LIST_HEAD(&file.insn_list); | |
2474 | hash_init(file.insn_hash); | |
dcc914f4 | 2475 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2476 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2477 | file.hints = false; |
dcc914f4 | 2478 | |
baa41469 JP |
2479 | arch_initial_func_cfi_state(&initial_func_cfi); |
2480 | ||
dcc914f4 JP |
2481 | ret = decode_sections(&file); |
2482 | if (ret < 0) | |
2483 | goto out; | |
2484 | warnings += ret; | |
2485 | ||
baa41469 | 2486 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2487 | goto out; |
dcc914f4 | 2488 | |
b5bc2231 PZ |
2489 | if (retpoline) { |
2490 | ret = validate_retpoline(&file); | |
2491 | if (ret < 0) | |
2492 | return ret; | |
2493 | warnings += ret; | |
2494 | } | |
2495 | ||
baa41469 | 2496 | ret = validate_functions(&file); |
dcc914f4 JP |
2497 | if (ret < 0) |
2498 | goto out; | |
2499 | warnings += ret; | |
2500 | ||
39358a03 JP |
2501 | ret = validate_unwind_hints(&file); |
2502 | if (ret < 0) | |
2503 | goto out; | |
2504 | warnings += ret; | |
2505 | ||
baa41469 JP |
2506 | if (!warnings) { |
2507 | ret = validate_reachable_instructions(&file); | |
2508 | if (ret < 0) | |
2509 | goto out; | |
2510 | warnings += ret; | |
2511 | } | |
2512 | ||
627fce14 JP |
2513 | if (orc) { |
2514 | ret = create_orc(&file); | |
2515 | if (ret < 0) | |
2516 | goto out; | |
2517 | ||
2518 | ret = create_orc_sections(&file); | |
2519 | if (ret < 0) | |
2520 | goto out; | |
2521 | ||
2522 | ret = elf_write(file.elf); | |
2523 | if (ret < 0) | |
2524 | goto out; | |
2525 | } | |
2526 | ||
dcc914f4 | 2527 | out: |
644592d3 JP |
2528 | if (ret < 0) { |
2529 | /* | |
2530 | * Fatal error. The binary is corrupt or otherwise broken in | |
2531 | * some way, or objtool itself is broken. Fail the kernel | |
2532 | * build. | |
2533 | */ | |
2534 | return ret; | |
2535 | } | |
2536 | ||
dcc914f4 JP |
2537 | return 0; |
2538 | } |