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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", | |
36b1c700 | 491 | "__sanitizer_cov_trace_switch", |
ea24213d PZ |
492 | /* UBSAN */ |
493 | "ubsan_type_mismatch_common", | |
494 | "__ubsan_handle_type_mismatch", | |
495 | "__ubsan_handle_type_mismatch_v1", | |
9a50dcaf | 496 | "__ubsan_handle_shift_out_of_bounds", |
ea24213d PZ |
497 | /* misc */ |
498 | "csum_partial_copy_generic", | |
499 | "__memcpy_mcsafe", | |
a7e47f26 | 500 | "mcsafe_handle_tail", |
ea24213d PZ |
501 | "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ |
502 | NULL | |
503 | }; | |
504 | ||
505 | static void add_uaccess_safe(struct objtool_file *file) | |
506 | { | |
507 | struct symbol *func; | |
508 | const char **name; | |
509 | ||
510 | if (!uaccess) | |
511 | return; | |
512 | ||
513 | for (name = uaccess_safe_builtin; *name; name++) { | |
514 | func = find_symbol_by_name(file->elf, *name); | |
515 | if (!func) | |
516 | continue; | |
517 | ||
e10cd8fe | 518 | func->uaccess_safe = true; |
dcc914f4 JP |
519 | } |
520 | } | |
521 | ||
258c7605 JP |
522 | /* |
523 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
524 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
525 | * But it at least allows objtool to understand the control flow *around* the | |
526 | * retpoline. | |
527 | */ | |
ff05ab23 | 528 | static int add_ignore_alternatives(struct objtool_file *file) |
258c7605 JP |
529 | { |
530 | struct section *sec; | |
531 | struct rela *rela; | |
532 | struct instruction *insn; | |
533 | ||
ff05ab23 | 534 | sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); |
258c7605 JP |
535 | if (!sec) |
536 | return 0; | |
537 | ||
538 | list_for_each_entry(rela, &sec->rela_list, list) { | |
539 | if (rela->sym->type != STT_SECTION) { | |
540 | WARN("unexpected relocation symbol type in %s", sec->name); | |
541 | return -1; | |
542 | } | |
543 | ||
544 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
545 | if (!insn) { | |
ff05ab23 | 546 | WARN("bad .discard.ignore_alts entry"); |
258c7605 JP |
547 | return -1; |
548 | } | |
549 | ||
550 | insn->ignore_alts = true; | |
551 | } | |
552 | ||
553 | return 0; | |
554 | } | |
555 | ||
dcc914f4 JP |
556 | /* |
557 | * Find the destination instructions for all jumps. | |
558 | */ | |
559 | static int add_jump_destinations(struct objtool_file *file) | |
560 | { | |
561 | struct instruction *insn; | |
562 | struct rela *rela; | |
563 | struct section *dest_sec; | |
564 | unsigned long dest_off; | |
565 | ||
566 | for_each_insn(file, insn) { | |
a2296140 | 567 | if (!is_static_jump(insn)) |
dcc914f4 JP |
568 | continue; |
569 | ||
e6da9567 | 570 | if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET) |
dcc914f4 JP |
571 | continue; |
572 | ||
8b5fa6bc PZ |
573 | rela = find_rela_by_dest_range(file->elf, insn->sec, |
574 | insn->offset, insn->len); | |
dcc914f4 JP |
575 | if (!rela) { |
576 | dest_sec = insn->sec; | |
577 | dest_off = insn->offset + insn->len + insn->immediate; | |
578 | } else if (rela->sym->type == STT_SECTION) { | |
579 | dest_sec = rela->sym->sec; | |
580 | dest_off = rela->addend + 4; | |
581 | } else if (rela->sym->sec->idx) { | |
582 | dest_sec = rela->sym->sec; | |
583 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
584 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
585 | /* | |
586 | * Retpoline jumps are really dynamic jumps in | |
587 | * disguise, so convert them accordingly. | |
588 | */ | |
b68b9907 JP |
589 | if (insn->type == INSN_JUMP_UNCONDITIONAL) |
590 | insn->type = INSN_JUMP_DYNAMIC; | |
591 | else | |
592 | insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; | |
593 | ||
b5bc2231 | 594 | insn->retpoline_safe = true; |
39b73533 | 595 | continue; |
dcc914f4 | 596 | } else { |
0c1ddd33 | 597 | /* external sibling call */ |
54262aa2 | 598 | insn->call_dest = rela->sym; |
dcc914f4 JP |
599 | continue; |
600 | } | |
601 | ||
602 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
603 | if (!insn->jump_dest) { | |
604 | ||
605 | /* | |
606 | * This is a special case where an alt instruction | |
607 | * jumps past the end of the section. These are | |
608 | * handled later in handle_group_alt(). | |
609 | */ | |
610 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
611 | continue; | |
612 | ||
613 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
614 | insn->sec, insn->offset, dest_sec->name, | |
615 | dest_off); | |
616 | return -1; | |
617 | } | |
cd77849a JP |
618 | |
619 | /* | |
54262aa2 | 620 | * Cross-function jump. |
cd77849a JP |
621 | */ |
622 | if (insn->func && insn->jump_dest->func && | |
54262aa2 PZ |
623 | insn->func != insn->jump_dest->func) { |
624 | ||
625 | /* | |
626 | * For GCC 8+, create parent/child links for any cold | |
627 | * subfunctions. This is _mostly_ redundant with a | |
628 | * similar initialization in read_symbols(). | |
629 | * | |
630 | * If a function has aliases, we want the *first* such | |
631 | * function in the symbol table to be the subfunction's | |
632 | * parent. In that case we overwrite the | |
633 | * initialization done in read_symbols(). | |
634 | * | |
635 | * However this code can't completely replace the | |
636 | * read_symbols() code because this doesn't detect the | |
637 | * case where the parent function's only reference to a | |
e7c2bc37 | 638 | * subfunction is through a jump table. |
54262aa2 PZ |
639 | */ |
640 | if (!strstr(insn->func->name, ".cold.") && | |
641 | strstr(insn->jump_dest->func->name, ".cold.")) { | |
642 | insn->func->cfunc = insn->jump_dest->func; | |
643 | insn->jump_dest->func->pfunc = insn->func; | |
644 | ||
645 | } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && | |
646 | insn->jump_dest->offset == insn->jump_dest->func->offset) { | |
647 | ||
0c1ddd33 | 648 | /* internal sibling call */ |
54262aa2 | 649 | insn->call_dest = insn->jump_dest->func; |
54262aa2 | 650 | } |
cd77849a | 651 | } |
dcc914f4 JP |
652 | } |
653 | ||
654 | return 0; | |
655 | } | |
656 | ||
657 | /* | |
658 | * Find the destination instructions for all calls. | |
659 | */ | |
660 | static int add_call_destinations(struct objtool_file *file) | |
661 | { | |
662 | struct instruction *insn; | |
663 | unsigned long dest_off; | |
664 | struct rela *rela; | |
665 | ||
666 | for_each_insn(file, insn) { | |
667 | if (insn->type != INSN_CALL) | |
668 | continue; | |
669 | ||
8b5fa6bc PZ |
670 | rela = find_rela_by_dest_range(file->elf, insn->sec, |
671 | insn->offset, insn->len); | |
dcc914f4 JP |
672 | if (!rela) { |
673 | dest_off = insn->offset + insn->len + insn->immediate; | |
7acfe531 JP |
674 | insn->call_dest = find_func_by_offset(insn->sec, dest_off); |
675 | if (!insn->call_dest) | |
676 | insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); | |
a845c7cf | 677 | |
7acfe531 JP |
678 | if (insn->ignore) |
679 | continue; | |
680 | ||
681 | if (!insn->call_dest) { | |
a845c7cf JP |
682 | WARN_FUNC("unsupported intra-function call", |
683 | insn->sec, insn->offset); | |
b5bc2231 PZ |
684 | if (retpoline) |
685 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
686 | return -1; |
687 | } | |
a845c7cf | 688 | |
7acfe531 JP |
689 | if (insn->func && insn->call_dest->type != STT_FUNC) { |
690 | WARN_FUNC("unsupported call to non-function", | |
691 | insn->sec, insn->offset); | |
692 | return -1; | |
693 | } | |
694 | ||
dcc914f4 | 695 | } else if (rela->sym->type == STT_SECTION) { |
7acfe531 JP |
696 | insn->call_dest = find_func_by_offset(rela->sym->sec, |
697 | rela->addend+4); | |
698 | if (!insn->call_dest) { | |
dcc914f4 JP |
699 | WARN_FUNC("can't find call dest symbol at %s+0x%x", |
700 | insn->sec, insn->offset, | |
701 | rela->sym->sec->name, | |
702 | rela->addend + 4); | |
703 | return -1; | |
704 | } | |
705 | } else | |
706 | insn->call_dest = rela->sym; | |
707 | } | |
708 | ||
709 | return 0; | |
710 | } | |
711 | ||
712 | /* | |
713 | * The .alternatives section requires some extra special care, over and above | |
714 | * what other special sections require: | |
715 | * | |
716 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
717 | * instruction at the end so that validate_branch() skips all the original | |
718 | * replaced instructions when validating the new instruction path. | |
719 | * | |
720 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
721 | * that case the old instructions are replaced with noops. We simulate that | |
722 | * by creating a fake jump as the only new instruction. | |
723 | * | |
724 | * 3. In some cases, the alternative section includes an instruction which | |
725 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
726 | * jumps' destinations to point back to .text rather than the end of the | |
727 | * entry in .altinstr_replacement. | |
dcc914f4 JP |
728 | */ |
729 | static int handle_group_alt(struct objtool_file *file, | |
730 | struct special_alt *special_alt, | |
731 | struct instruction *orig_insn, | |
732 | struct instruction **new_insn) | |
733 | { | |
17bc3391 | 734 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
735 | unsigned long dest_off; |
736 | ||
737 | last_orig_insn = NULL; | |
738 | insn = orig_insn; | |
739 | sec_for_each_insn_from(file, insn) { | |
740 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
741 | break; | |
742 | ||
dcc914f4 JP |
743 | insn->alt_group = true; |
744 | last_orig_insn = insn; | |
745 | } | |
746 | ||
17bc3391 JP |
747 | if (next_insn_same_sec(file, last_orig_insn)) { |
748 | fake_jump = malloc(sizeof(*fake_jump)); | |
749 | if (!fake_jump) { | |
750 | WARN("malloc failed"); | |
751 | return -1; | |
752 | } | |
753 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
754 | INIT_LIST_HEAD(&fake_jump->alts); | |
755 | clear_insn_state(&fake_jump->state); | |
756 | ||
757 | fake_jump->sec = special_alt->new_sec; | |
e6da9567 | 758 | fake_jump->offset = FAKE_JUMP_OFFSET; |
17bc3391 JP |
759 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; |
760 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
e6da9567 | 761 | fake_jump->func = orig_insn->func; |
dcc914f4 | 762 | } |
dcc914f4 JP |
763 | |
764 | if (!special_alt->new_len) { | |
17bc3391 JP |
765 | if (!fake_jump) { |
766 | WARN("%s: empty alternative at end of section", | |
767 | special_alt->orig_sec->name); | |
768 | return -1; | |
769 | } | |
770 | ||
dcc914f4 JP |
771 | *new_insn = fake_jump; |
772 | return 0; | |
773 | } | |
774 | ||
775 | last_new_insn = NULL; | |
776 | insn = *new_insn; | |
777 | sec_for_each_insn_from(file, insn) { | |
778 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
779 | break; | |
780 | ||
781 | last_new_insn = insn; | |
782 | ||
a845c7cf | 783 | insn->ignore = orig_insn->ignore_alts; |
a4d09dde | 784 | insn->func = orig_insn->func; |
a845c7cf | 785 | |
dc419723 JP |
786 | /* |
787 | * Since alternative replacement code is copy/pasted by the | |
788 | * kernel after applying relocations, generally such code can't | |
789 | * have relative-address relocation references to outside the | |
790 | * .altinstr_replacement section, unless the arch's | |
791 | * alternatives code can adjust the relative offsets | |
792 | * accordingly. | |
793 | * | |
794 | * The x86 alternatives code adjusts the offsets only when it | |
795 | * encounters a branch instruction at the very beginning of the | |
796 | * replacement group. | |
797 | */ | |
798 | if ((insn->offset != special_alt->new_off || | |
799 | (insn->type != INSN_CALL && !is_static_jump(insn))) && | |
8b5fa6bc | 800 | find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) { |
dc419723 JP |
801 | |
802 | WARN_FUNC("unsupported relocation in alternatives section", | |
803 | insn->sec, insn->offset); | |
804 | return -1; | |
805 | } | |
806 | ||
a2296140 | 807 | if (!is_static_jump(insn)) |
dcc914f4 JP |
808 | continue; |
809 | ||
810 | if (!insn->immediate) | |
811 | continue; | |
812 | ||
813 | dest_off = insn->offset + insn->len + insn->immediate; | |
17bc3391 JP |
814 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
815 | if (!fake_jump) { | |
816 | WARN("%s: alternative jump to end of section", | |
817 | special_alt->orig_sec->name); | |
818 | return -1; | |
819 | } | |
dcc914f4 | 820 | insn->jump_dest = fake_jump; |
17bc3391 | 821 | } |
dcc914f4 JP |
822 | |
823 | if (!insn->jump_dest) { | |
824 | WARN_FUNC("can't find alternative jump destination", | |
825 | insn->sec, insn->offset); | |
826 | return -1; | |
827 | } | |
828 | } | |
829 | ||
830 | if (!last_new_insn) { | |
831 | WARN_FUNC("can't find last new alternative instruction", | |
832 | special_alt->new_sec, special_alt->new_off); | |
833 | return -1; | |
834 | } | |
835 | ||
17bc3391 JP |
836 | if (fake_jump) |
837 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
838 | |
839 | return 0; | |
840 | } | |
841 | ||
842 | /* | |
843 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
844 | * If the original instruction is a jump, make the alt entry an effective nop | |
845 | * by just skipping the original instruction. | |
846 | */ | |
847 | static int handle_jump_alt(struct objtool_file *file, | |
848 | struct special_alt *special_alt, | |
849 | struct instruction *orig_insn, | |
850 | struct instruction **new_insn) | |
851 | { | |
852 | if (orig_insn->type == INSN_NOP) | |
853 | return 0; | |
854 | ||
855 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
856 | WARN_FUNC("unsupported instruction at jump label", | |
857 | orig_insn->sec, orig_insn->offset); | |
858 | return -1; | |
859 | } | |
860 | ||
861 | *new_insn = list_next_entry(orig_insn, list); | |
862 | return 0; | |
863 | } | |
864 | ||
865 | /* | |
866 | * Read all the special sections which have alternate instructions which can be | |
867 | * patched in or redirected to at runtime. Each instruction having alternate | |
868 | * instruction(s) has them added to its insn->alts list, which will be | |
869 | * traversed in validate_branch(). | |
870 | */ | |
871 | static int add_special_section_alts(struct objtool_file *file) | |
872 | { | |
873 | struct list_head special_alts; | |
874 | struct instruction *orig_insn, *new_insn; | |
875 | struct special_alt *special_alt, *tmp; | |
876 | struct alternative *alt; | |
877 | int ret; | |
878 | ||
879 | ret = special_get_alts(file->elf, &special_alts); | |
880 | if (ret) | |
881 | return ret; | |
882 | ||
883 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
884 | |
885 | orig_insn = find_insn(file, special_alt->orig_sec, | |
886 | special_alt->orig_off); | |
887 | if (!orig_insn) { | |
888 | WARN_FUNC("special: can't find orig instruction", | |
889 | special_alt->orig_sec, special_alt->orig_off); | |
890 | ret = -1; | |
891 | goto out; | |
892 | } | |
893 | ||
894 | new_insn = NULL; | |
895 | if (!special_alt->group || special_alt->new_len) { | |
896 | new_insn = find_insn(file, special_alt->new_sec, | |
897 | special_alt->new_off); | |
898 | if (!new_insn) { | |
899 | WARN_FUNC("special: can't find new instruction", | |
900 | special_alt->new_sec, | |
901 | special_alt->new_off); | |
902 | ret = -1; | |
903 | goto out; | |
904 | } | |
905 | } | |
906 | ||
907 | if (special_alt->group) { | |
908 | ret = handle_group_alt(file, special_alt, orig_insn, | |
909 | &new_insn); | |
910 | if (ret) | |
911 | goto out; | |
912 | } else if (special_alt->jump_or_nop) { | |
913 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
914 | &new_insn); | |
915 | if (ret) | |
916 | goto out; | |
917 | } | |
918 | ||
258c7605 JP |
919 | alt = malloc(sizeof(*alt)); |
920 | if (!alt) { | |
921 | WARN("malloc failed"); | |
922 | ret = -1; | |
923 | goto out; | |
924 | } | |
925 | ||
dcc914f4 | 926 | alt->insn = new_insn; |
764eef4b | 927 | alt->skip_orig = special_alt->skip_orig; |
ea24213d | 928 | orig_insn->ignore_alts |= special_alt->skip_alt; |
dcc914f4 JP |
929 | list_add_tail(&alt->list, &orig_insn->alts); |
930 | ||
931 | list_del(&special_alt->list); | |
932 | free(special_alt); | |
933 | } | |
934 | ||
935 | out: | |
936 | return ret; | |
937 | } | |
938 | ||
e7c2bc37 | 939 | static int add_jump_table(struct objtool_file *file, struct instruction *insn, |
bd98c813 | 940 | struct rela *table) |
dcc914f4 JP |
941 | { |
942 | struct rela *rela = table; | |
e7c2bc37 | 943 | struct instruction *dest_insn; |
dcc914f4 | 944 | struct alternative *alt; |
fd35c88b JP |
945 | struct symbol *pfunc = insn->func->pfunc; |
946 | unsigned int prev_offset = 0; | |
dcc914f4 | 947 | |
e7c2bc37 JP |
948 | /* |
949 | * Each @rela is a switch table relocation which points to the target | |
950 | * instruction. | |
951 | */ | |
952 | list_for_each_entry_from(rela, &table->sec->rela_list, list) { | |
bd98c813 JH |
953 | |
954 | /* Check for the end of the table: */ | |
955 | if (rela != table && rela->jump_table_start) | |
dcc914f4 JP |
956 | break; |
957 | ||
e7c2bc37 | 958 | /* Make sure the table entries are consecutive: */ |
fd35c88b JP |
959 | if (prev_offset && rela->offset != prev_offset + 8) |
960 | break; | |
961 | ||
962 | /* Detect function pointers from contiguous objects: */ | |
963 | if (rela->sym->sec == pfunc->sec && | |
964 | rela->addend == pfunc->offset) | |
965 | break; | |
966 | ||
e7c2bc37 JP |
967 | dest_insn = find_insn(file, rela->sym->sec, rela->addend); |
968 | if (!dest_insn) | |
dcc914f4 JP |
969 | break; |
970 | ||
e7c2bc37 | 971 | /* Make sure the destination is in the same function: */ |
e65050b9 | 972 | if (!dest_insn->func || dest_insn->func->pfunc != pfunc) |
13810435 | 973 | break; |
dcc914f4 JP |
974 | |
975 | alt = malloc(sizeof(*alt)); | |
976 | if (!alt) { | |
977 | WARN("malloc failed"); | |
978 | return -1; | |
979 | } | |
980 | ||
e7c2bc37 | 981 | alt->insn = dest_insn; |
dcc914f4 | 982 | list_add_tail(&alt->list, &insn->alts); |
fd35c88b JP |
983 | prev_offset = rela->offset; |
984 | } | |
985 | ||
986 | if (!prev_offset) { | |
987 | WARN_FUNC("can't find switch jump table", | |
988 | insn->sec, insn->offset); | |
989 | return -1; | |
dcc914f4 JP |
990 | } |
991 | ||
992 | return 0; | |
993 | } | |
994 | ||
995 | /* | |
e7c2bc37 | 996 | * find_jump_table() - Given a dynamic jump, find the switch jump table in |
dcc914f4 JP |
997 | * .rodata associated with it. |
998 | * | |
999 | * There are 3 basic patterns: | |
1000 | * | |
1001 | * 1. jmpq *[rodata addr](,%reg,8) | |
1002 | * | |
1003 | * This is the most common case by far. It jumps to an address in a simple | |
1004 | * jump table which is stored in .rodata. | |
1005 | * | |
1006 | * 2. jmpq *[rodata addr](%rip) | |
1007 | * | |
1008 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
1009 | * functions in the kernel, only with certain obscure non-distro configs. | |
1010 | * | |
1011 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
1012 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
1013 | * jump) to use a single entry in the table. The rest of the jump table and | |
1014 | * some of its jump targets remain as dead code. | |
1015 | * | |
1016 | * In such a case we can just crudely ignore all unreachable instruction | |
1017 | * warnings for the entire object file. Ideally we would just ignore them | |
1018 | * for the function, but that would require redesigning the code quite a | |
1019 | * bit. And honestly that's just not worth doing: unreachable instruction | |
1020 | * warnings are of questionable value anyway, and this is such a rare issue. | |
1021 | * | |
1022 | * 3. mov [rodata addr],%reg1 | |
1023 | * ... some instructions ... | |
1024 | * jmpq *(%reg1,%reg2,8) | |
1025 | * | |
1026 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
1027 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
1028 | * | |
99ce7962 PZ |
1029 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
1030 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
1031 | * and jmpq uses .rodata itself, which can confuse things. | |
1032 | * | |
dcc914f4 JP |
1033 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
1034 | * ensure the same register is used in the mov and jump instructions. | |
99ce7962 PZ |
1035 | * |
1036 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 | 1037 | */ |
e7c2bc37 | 1038 | static struct rela *find_jump_table(struct objtool_file *file, |
dcc914f4 JP |
1039 | struct symbol *func, |
1040 | struct instruction *insn) | |
1041 | { | |
e7c2bc37 | 1042 | struct rela *text_rela, *table_rela; |
113d4bc9 | 1043 | struct instruction *dest_insn, *orig_insn = insn; |
e7c2bc37 | 1044 | struct section *table_sec; |
6f5ec299 | 1045 | unsigned long table_offset; |
dcc914f4 | 1046 | |
99ce7962 PZ |
1047 | /* |
1048 | * Backward search using the @first_jump_src links, these help avoid | |
1049 | * much of the 'in between' code. Which avoids us getting confused by | |
1050 | * it. | |
1051 | */ | |
7dec80cc | 1052 | for (; |
b401efc1 | 1053 | &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func; |
99ce7962 PZ |
1054 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { |
1055 | ||
7dec80cc | 1056 | if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) |
dcc914f4 JP |
1057 | break; |
1058 | ||
1059 | /* allow small jumps within the range */ | |
1060 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
1061 | insn->jump_dest && | |
1062 | (insn->jump_dest->offset <= insn->offset || | |
1063 | insn->jump_dest->offset > orig_insn->offset)) | |
1064 | break; | |
1065 | ||
1066 | /* look for a relocation which references .rodata */ | |
8b5fa6bc PZ |
1067 | text_rela = find_rela_by_dest_range(file->elf, insn->sec, |
1068 | insn->offset, insn->len); | |
4a60aa05 AX |
1069 | if (!text_rela || text_rela->sym->type != STT_SECTION || |
1070 | !text_rela->sym->sec->rodata) | |
dcc914f4 JP |
1071 | continue; |
1072 | ||
6f5ec299 | 1073 | table_offset = text_rela->addend; |
e7c2bc37 | 1074 | table_sec = text_rela->sym->sec; |
4a60aa05 | 1075 | |
6f5ec299 JP |
1076 | if (text_rela->type == R_X86_64_PC32) |
1077 | table_offset += 4; | |
1078 | ||
dcc914f4 JP |
1079 | /* |
1080 | * Make sure the .rodata address isn't associated with a | |
87b512de JP |
1081 | * symbol. GCC jump tables are anonymous data. |
1082 | * | |
1083 | * Also support C jump tables which are in the same format as | |
1084 | * switch jump tables. For objtool to recognize them, they | |
1085 | * need to be placed in the C_JUMP_TABLE_SECTION section. They | |
1086 | * have symbols associated with them. | |
dcc914f4 | 1087 | */ |
e7c2bc37 JP |
1088 | if (find_symbol_containing(table_sec, table_offset) && |
1089 | strcmp(table_sec->name, C_JUMP_TABLE_SECTION)) | |
1402fd8e JP |
1090 | continue; |
1091 | ||
113d4bc9 JP |
1092 | /* |
1093 | * Each table entry has a rela associated with it. The rela | |
1094 | * should reference text in the same function as the original | |
1095 | * instruction. | |
1096 | */ | |
8b5fa6bc | 1097 | table_rela = find_rela_by_dest(file->elf, table_sec, table_offset); |
e7c2bc37 JP |
1098 | if (!table_rela) |
1099 | continue; | |
113d4bc9 JP |
1100 | dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend); |
1101 | if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) | |
1102 | continue; | |
7dec80cc | 1103 | |
e7c2bc37 JP |
1104 | /* |
1105 | * Use of RIP-relative switch jumps is quite rare, and | |
1106 | * indicates a rare GCC quirk/bug which can leave dead code | |
1107 | * behind. | |
1108 | */ | |
1109 | if (text_rela->type == R_X86_64_PC32) | |
1110 | file->ignore_unreachables = true; | |
1111 | ||
1112 | return table_rela; | |
dcc914f4 JP |
1113 | } |
1114 | ||
1115 | return NULL; | |
1116 | } | |
1117 | ||
bd98c813 JH |
1118 | /* |
1119 | * First pass: Mark the head of each jump table so that in the next pass, | |
1120 | * we know when a given jump table ends and the next one starts. | |
1121 | */ | |
1122 | static void mark_func_jump_tables(struct objtool_file *file, | |
1123 | struct symbol *func) | |
dcc914f4 | 1124 | { |
bd98c813 JH |
1125 | struct instruction *insn, *last = NULL; |
1126 | struct rela *rela; | |
dcc914f4 | 1127 | |
f0f70adb | 1128 | func_for_each_insn(file, func, insn) { |
99ce7962 PZ |
1129 | if (!last) |
1130 | last = insn; | |
1131 | ||
1132 | /* | |
1133 | * Store back-pointers for unconditional forward jumps such | |
e7c2bc37 | 1134 | * that find_jump_table() can back-track using those and |
99ce7962 PZ |
1135 | * avoid some potentially confusing code. |
1136 | */ | |
1137 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
1138 | insn->offset > last->offset && | |
1139 | insn->jump_dest->offset > insn->offset && | |
1140 | !insn->jump_dest->first_jump_src) { | |
1141 | ||
1142 | insn->jump_dest->first_jump_src = insn; | |
1143 | last = insn->jump_dest; | |
1144 | } | |
1145 | ||
dcc914f4 JP |
1146 | if (insn->type != INSN_JUMP_DYNAMIC) |
1147 | continue; | |
1148 | ||
e7c2bc37 | 1149 | rela = find_jump_table(file, func, insn); |
bd98c813 JH |
1150 | if (rela) { |
1151 | rela->jump_table_start = true; | |
1152 | insn->jump_table = rela; | |
dcc914f4 | 1153 | } |
dcc914f4 | 1154 | } |
bd98c813 JH |
1155 | } |
1156 | ||
1157 | static int add_func_jump_tables(struct objtool_file *file, | |
1158 | struct symbol *func) | |
1159 | { | |
1160 | struct instruction *insn; | |
1161 | int ret; | |
1162 | ||
f0f70adb | 1163 | func_for_each_insn(file, func, insn) { |
bd98c813 JH |
1164 | if (!insn->jump_table) |
1165 | continue; | |
dcc914f4 | 1166 | |
bd98c813 | 1167 | ret = add_jump_table(file, insn, insn->jump_table); |
dcc914f4 JP |
1168 | if (ret) |
1169 | return ret; | |
1170 | } | |
1171 | ||
1172 | return 0; | |
1173 | } | |
1174 | ||
1175 | /* | |
1176 | * For some switch statements, gcc generates a jump table in the .rodata | |
1177 | * section which contains a list of addresses within the function to jump to. | |
1178 | * This finds these jump tables and adds them to the insn->alts lists. | |
1179 | */ | |
e7c2bc37 | 1180 | static int add_jump_table_alts(struct objtool_file *file) |
dcc914f4 JP |
1181 | { |
1182 | struct section *sec; | |
1183 | struct symbol *func; | |
1184 | int ret; | |
1185 | ||
4a60aa05 | 1186 | if (!file->rodata) |
dcc914f4 JP |
1187 | return 0; |
1188 | ||
baa41469 | 1189 | for_each_sec(file, sec) { |
dcc914f4 JP |
1190 | list_for_each_entry(func, &sec->symbol_list, list) { |
1191 | if (func->type != STT_FUNC) | |
1192 | continue; | |
1193 | ||
bd98c813 | 1194 | mark_func_jump_tables(file, func); |
e7c2bc37 | 1195 | ret = add_func_jump_tables(file, func); |
dcc914f4 JP |
1196 | if (ret) |
1197 | return ret; | |
1198 | } | |
1199 | } | |
1200 | ||
1201 | return 0; | |
1202 | } | |
1203 | ||
39358a03 JP |
1204 | static int read_unwind_hints(struct objtool_file *file) |
1205 | { | |
1206 | struct section *sec, *relasec; | |
1207 | struct rela *rela; | |
1208 | struct unwind_hint *hint; | |
1209 | struct instruction *insn; | |
1210 | struct cfi_reg *cfa; | |
1211 | int i; | |
1212 | ||
1213 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1214 | if (!sec) | |
1215 | return 0; | |
1216 | ||
1217 | relasec = sec->rela; | |
1218 | if (!relasec) { | |
1219 | WARN("missing .rela.discard.unwind_hints section"); | |
1220 | return -1; | |
1221 | } | |
1222 | ||
1223 | if (sec->len % sizeof(struct unwind_hint)) { | |
1224 | WARN("struct unwind_hint size mismatch"); | |
1225 | return -1; | |
1226 | } | |
1227 | ||
1228 | file->hints = true; | |
1229 | ||
1230 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1231 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1232 | ||
8b5fa6bc | 1233 | rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint)); |
39358a03 JP |
1234 | if (!rela) { |
1235 | WARN("can't find rela for unwind_hints[%d]", i); | |
1236 | return -1; | |
1237 | } | |
1238 | ||
1239 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1240 | if (!insn) { | |
1241 | WARN("can't find insn for unwind_hints[%d]", i); | |
1242 | return -1; | |
1243 | } | |
1244 | ||
1245 | cfa = &insn->state.cfa; | |
1246 | ||
1247 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1248 | insn->save = true; | |
1249 | continue; | |
1250 | ||
1251 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1252 | insn->restore = true; | |
1253 | insn->hint = true; | |
1254 | continue; | |
1255 | } | |
1256 | ||
1257 | insn->hint = true; | |
1258 | ||
1259 | switch (hint->sp_reg) { | |
1260 | case ORC_REG_UNDEFINED: | |
1261 | cfa->base = CFI_UNDEFINED; | |
1262 | break; | |
1263 | case ORC_REG_SP: | |
1264 | cfa->base = CFI_SP; | |
1265 | break; | |
1266 | case ORC_REG_BP: | |
1267 | cfa->base = CFI_BP; | |
1268 | break; | |
1269 | case ORC_REG_SP_INDIRECT: | |
1270 | cfa->base = CFI_SP_INDIRECT; | |
1271 | break; | |
1272 | case ORC_REG_R10: | |
1273 | cfa->base = CFI_R10; | |
1274 | break; | |
1275 | case ORC_REG_R13: | |
1276 | cfa->base = CFI_R13; | |
1277 | break; | |
1278 | case ORC_REG_DI: | |
1279 | cfa->base = CFI_DI; | |
1280 | break; | |
1281 | case ORC_REG_DX: | |
1282 | cfa->base = CFI_DX; | |
1283 | break; | |
1284 | default: | |
1285 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1286 | insn->sec, insn->offset, hint->sp_reg); | |
1287 | return -1; | |
1288 | } | |
1289 | ||
1290 | cfa->offset = hint->sp_offset; | |
1291 | insn->state.type = hint->type; | |
d31a5802 | 1292 | insn->state.end = hint->end; |
39358a03 JP |
1293 | } |
1294 | ||
1295 | return 0; | |
1296 | } | |
1297 | ||
b5bc2231 PZ |
1298 | static int read_retpoline_hints(struct objtool_file *file) |
1299 | { | |
63474dc4 | 1300 | struct section *sec; |
b5bc2231 PZ |
1301 | struct instruction *insn; |
1302 | struct rela *rela; | |
b5bc2231 | 1303 | |
63474dc4 | 1304 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
b5bc2231 PZ |
1305 | if (!sec) |
1306 | return 0; | |
1307 | ||
63474dc4 JP |
1308 | list_for_each_entry(rela, &sec->rela_list, list) { |
1309 | if (rela->sym->type != STT_SECTION) { | |
1310 | WARN("unexpected relocation symbol type in %s", sec->name); | |
b5bc2231 PZ |
1311 | return -1; |
1312 | } | |
1313 | ||
1314 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1315 | if (!insn) { | |
63474dc4 | 1316 | WARN("bad .discard.retpoline_safe entry"); |
b5bc2231 PZ |
1317 | return -1; |
1318 | } | |
1319 | ||
1320 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1321 | insn->type != INSN_CALL_DYNAMIC) { | |
63474dc4 | 1322 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
b5bc2231 PZ |
1323 | insn->sec, insn->offset); |
1324 | return -1; | |
1325 | } | |
1326 | ||
1327 | insn->retpoline_safe = true; | |
1328 | } | |
1329 | ||
1330 | return 0; | |
1331 | } | |
1332 | ||
4a60aa05 AX |
1333 | static void mark_rodata(struct objtool_file *file) |
1334 | { | |
1335 | struct section *sec; | |
1336 | bool found = false; | |
1337 | ||
1338 | /* | |
87b512de JP |
1339 | * Search for the following rodata sections, each of which can |
1340 | * potentially contain jump tables: | |
1341 | * | |
1342 | * - .rodata: can contain GCC switch tables | |
1343 | * - .rodata.<func>: same, if -fdata-sections is being used | |
1344 | * - .rodata..c_jump_table: contains C annotated jump tables | |
1345 | * | |
1346 | * .rodata.str1.* sections are ignored; they don't contain jump tables. | |
4a60aa05 AX |
1347 | */ |
1348 | for_each_sec(file, sec) { | |
87b512de JP |
1349 | if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) || |
1350 | !strcmp(sec->name, C_JUMP_TABLE_SECTION)) { | |
4a60aa05 AX |
1351 | sec->rodata = true; |
1352 | found = true; | |
1353 | } | |
1354 | } | |
1355 | ||
1356 | file->rodata = found; | |
1357 | } | |
1358 | ||
dcc914f4 JP |
1359 | static int decode_sections(struct objtool_file *file) |
1360 | { | |
1361 | int ret; | |
1362 | ||
4a60aa05 AX |
1363 | mark_rodata(file); |
1364 | ||
dcc914f4 JP |
1365 | ret = decode_instructions(file); |
1366 | if (ret) | |
1367 | return ret; | |
1368 | ||
1369 | ret = add_dead_ends(file); | |
1370 | if (ret) | |
1371 | return ret; | |
1372 | ||
1373 | add_ignores(file); | |
ea24213d | 1374 | add_uaccess_safe(file); |
dcc914f4 | 1375 | |
ff05ab23 | 1376 | ret = add_ignore_alternatives(file); |
258c7605 JP |
1377 | if (ret) |
1378 | return ret; | |
1379 | ||
dcc914f4 JP |
1380 | ret = add_jump_destinations(file); |
1381 | if (ret) | |
1382 | return ret; | |
1383 | ||
a845c7cf | 1384 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1385 | if (ret) |
1386 | return ret; | |
1387 | ||
a845c7cf | 1388 | ret = add_call_destinations(file); |
dcc914f4 JP |
1389 | if (ret) |
1390 | return ret; | |
1391 | ||
e7c2bc37 | 1392 | ret = add_jump_table_alts(file); |
dcc914f4 JP |
1393 | if (ret) |
1394 | return ret; | |
1395 | ||
39358a03 JP |
1396 | ret = read_unwind_hints(file); |
1397 | if (ret) | |
1398 | return ret; | |
1399 | ||
b5bc2231 PZ |
1400 | ret = read_retpoline_hints(file); |
1401 | if (ret) | |
1402 | return ret; | |
1403 | ||
dcc914f4 JP |
1404 | return 0; |
1405 | } | |
1406 | ||
1407 | static bool is_fentry_call(struct instruction *insn) | |
1408 | { | |
1409 | if (insn->type == INSN_CALL && | |
1410 | insn->call_dest->type == STT_NOTYPE && | |
1411 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1412 | return true; | |
1413 | ||
1414 | return false; | |
1415 | } | |
1416 | ||
baa41469 | 1417 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1418 | { |
baa41469 JP |
1419 | int i; |
1420 | ||
1421 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1422 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1423 | state->stack_size != initial_func_cfi.cfa.offset || | |
1424 | state->drap) | |
1425 | return true; | |
1426 | ||
1427 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1428 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1429 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1430 | return true; | |
1431 | ||
1432 | return false; | |
1433 | } | |
1434 | ||
1435 | static bool has_valid_stack_frame(struct insn_state *state) | |
1436 | { | |
1437 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1438 | state->regs[CFI_BP].offset == -16) | |
1439 | return true; | |
1440 | ||
1441 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1442 | return true; | |
1443 | ||
1444 | return false; | |
dcc914f4 JP |
1445 | } |
1446 | ||
627fce14 JP |
1447 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1448 | { | |
1449 | struct cfi_reg *cfa = &state->cfa; | |
1450 | struct stack_op *op = &insn->stack_op; | |
1451 | ||
1452 | if (cfa->base != CFI_SP) | |
1453 | return 0; | |
1454 | ||
1455 | /* push */ | |
ea24213d | 1456 | if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) |
627fce14 JP |
1457 | cfa->offset += 8; |
1458 | ||
1459 | /* pop */ | |
ea24213d | 1460 | if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) |
627fce14 JP |
1461 | cfa->offset -= 8; |
1462 | ||
1463 | /* add immediate to sp */ | |
1464 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1465 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1466 | cfa->offset -= op->src.offset; | |
1467 | ||
1468 | return 0; | |
1469 | } | |
1470 | ||
baa41469 JP |
1471 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1472 | int offset) | |
dcc914f4 | 1473 | { |
bf4d1a83 | 1474 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1475 | state->regs[reg].base == CFI_UNDEFINED) { |
1476 | state->regs[reg].base = base; | |
1477 | state->regs[reg].offset = offset; | |
1478 | } | |
dcc914f4 JP |
1479 | } |
1480 | ||
baa41469 | 1481 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1482 | { |
baa41469 JP |
1483 | state->regs[reg].base = CFI_UNDEFINED; |
1484 | state->regs[reg].offset = 0; | |
1485 | } | |
1486 | ||
1487 | /* | |
1488 | * A note about DRAP stack alignment: | |
1489 | * | |
1490 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1491 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1492 | * register. The typical DRAP pattern is: | |
1493 | * | |
1494 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1495 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1496 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1497 | * 55 push %rbp | |
1498 | * 48 89 e5 mov %rsp,%rbp | |
1499 | * (more pushes) | |
1500 | * 41 52 push %r10 | |
1501 | * ... | |
1502 | * 41 5a pop %r10 | |
1503 | * (more pops) | |
1504 | * 5d pop %rbp | |
1505 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1506 | * c3 retq | |
1507 | * | |
1508 | * There are some variations in the epilogues, like: | |
1509 | * | |
1510 | * 5b pop %rbx | |
1511 | * 41 5a pop %r10 | |
1512 | * 41 5c pop %r12 | |
1513 | * 41 5d pop %r13 | |
1514 | * 41 5e pop %r14 | |
1515 | * c9 leaveq | |
1516 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1517 | * c3 retq | |
1518 | * | |
1519 | * and: | |
1520 | * | |
1521 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1522 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1523 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1524 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1525 | * c9 leaveq | |
1526 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1527 | * c3 retq | |
1528 | * | |
1529 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1530 | * restored beforehand: | |
1531 | * | |
1532 | * 41 55 push %r13 | |
1533 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1534 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1535 | * ... | |
1536 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1537 | * 41 5d pop %r13 | |
1538 | * c3 retq | |
1539 | */ | |
1540 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1541 | { | |
1542 | struct stack_op *op = &insn->stack_op; | |
1543 | struct cfi_reg *cfa = &state->cfa; | |
1544 | struct cfi_reg *regs = state->regs; | |
1545 | ||
1546 | /* stack operations don't make sense with an undefined CFA */ | |
1547 | if (cfa->base == CFI_UNDEFINED) { | |
1548 | if (insn->func) { | |
1549 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1550 | return -1; | |
1551 | } | |
1552 | return 0; | |
1553 | } | |
1554 | ||
627fce14 JP |
1555 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1556 | return update_insn_state_regs(insn, state); | |
1557 | ||
baa41469 JP |
1558 | switch (op->dest.type) { |
1559 | ||
1560 | case OP_DEST_REG: | |
1561 | switch (op->src.type) { | |
1562 | ||
1563 | case OP_SRC_REG: | |
0d0970ee JP |
1564 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1565 | cfa->base == CFI_SP && | |
1566 | regs[CFI_BP].base == CFI_CFA && | |
1567 | regs[CFI_BP].offset == -cfa->offset) { | |
1568 | ||
1569 | /* mov %rsp, %rbp */ | |
1570 | cfa->base = op->dest.reg; | |
1571 | state->bp_scratch = false; | |
1572 | } | |
dd88a0a0 | 1573 | |
0d0970ee JP |
1574 | else if (op->src.reg == CFI_SP && |
1575 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1576 | |
0d0970ee JP |
1577 | /* drap: mov %rsp, %rbp */ |
1578 | regs[CFI_BP].base = CFI_BP; | |
1579 | regs[CFI_BP].offset = -state->stack_size; | |
1580 | state->bp_scratch = false; | |
1581 | } | |
dd88a0a0 | 1582 | |
0d0970ee JP |
1583 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1584 | ||
1585 | /* | |
1586 | * mov %rsp, %reg | |
1587 | * | |
1588 | * This is needed for the rare case where GCC | |
1589 | * does: | |
1590 | * | |
1591 | * mov %rsp, %rax | |
1592 | * ... | |
1593 | * mov %rax, %rsp | |
1594 | */ | |
1595 | state->vals[op->dest.reg].base = CFI_CFA; | |
1596 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1597 | } |
1598 | ||
3c1f0583 JP |
1599 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
1600 | cfa->base == CFI_BP) { | |
1601 | ||
1602 | /* | |
1603 | * mov %rbp, %rsp | |
1604 | * | |
1605 | * Restore the original stack pointer (Clang). | |
1606 | */ | |
1607 | state->stack_size = -state->regs[CFI_BP].offset; | |
1608 | } | |
1609 | ||
dd88a0a0 JP |
1610 | else if (op->dest.reg == cfa->base) { |
1611 | ||
1612 | /* mov %reg, %rsp */ | |
1613 | if (cfa->base == CFI_SP && | |
1614 | state->vals[op->src.reg].base == CFI_CFA) { | |
1615 | ||
1616 | /* | |
1617 | * This is needed for the rare case | |
1618 | * where GCC does something dumb like: | |
1619 | * | |
1620 | * lea 0x8(%rsp), %rcx | |
1621 | * ... | |
1622 | * mov %rcx, %rsp | |
1623 | */ | |
1624 | cfa->offset = -state->vals[op->src.reg].offset; | |
1625 | state->stack_size = cfa->offset; | |
1626 | ||
1627 | } else { | |
1628 | cfa->base = CFI_UNDEFINED; | |
1629 | cfa->offset = 0; | |
1630 | } | |
baa41469 JP |
1631 | } |
1632 | ||
1633 | break; | |
1634 | ||
1635 | case OP_SRC_ADD: | |
1636 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1637 | ||
1638 | /* add imm, %rsp */ | |
1639 | state->stack_size -= op->src.offset; | |
1640 | if (cfa->base == CFI_SP) | |
1641 | cfa->offset -= op->src.offset; | |
1642 | break; | |
1643 | } | |
1644 | ||
1645 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1646 | ||
1647 | /* lea disp(%rbp), %rsp */ | |
1648 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1649 | break; | |
1650 | } | |
1651 | ||
dd88a0a0 | 1652 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1653 | |
1654 | /* drap: lea disp(%rsp), %drap */ | |
1655 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1656 | |
1657 | /* | |
1658 | * lea disp(%rsp), %reg | |
1659 | * | |
1660 | * This is needed for the rare case where GCC | |
1661 | * does something dumb like: | |
1662 | * | |
1663 | * lea 0x8(%rsp), %rcx | |
1664 | * ... | |
1665 | * mov %rcx, %rsp | |
1666 | */ | |
1667 | state->vals[op->dest.reg].base = CFI_CFA; | |
1668 | state->vals[op->dest.reg].offset = \ | |
1669 | -state->stack_size + op->src.offset; | |
1670 | ||
baa41469 JP |
1671 | break; |
1672 | } | |
1673 | ||
1674 | if (state->drap && op->dest.reg == CFI_SP && | |
1675 | op->src.reg == state->drap_reg) { | |
1676 | ||
1677 | /* drap: lea disp(%drap), %rsp */ | |
1678 | cfa->base = CFI_SP; | |
1679 | cfa->offset = state->stack_size = -op->src.offset; | |
1680 | state->drap_reg = CFI_UNDEFINED; | |
1681 | state->drap = false; | |
1682 | break; | |
1683 | } | |
1684 | ||
1685 | if (op->dest.reg == state->cfa.base) { | |
1686 | WARN_FUNC("unsupported stack register modification", | |
1687 | insn->sec, insn->offset); | |
1688 | return -1; | |
1689 | } | |
1690 | ||
1691 | break; | |
1692 | ||
1693 | case OP_SRC_AND: | |
1694 | if (op->dest.reg != CFI_SP || | |
1695 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1696 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1697 | WARN_FUNC("unsupported stack pointer realignment", | |
1698 | insn->sec, insn->offset); | |
1699 | return -1; | |
1700 | } | |
1701 | ||
1702 | if (state->drap_reg != CFI_UNDEFINED) { | |
1703 | /* drap: and imm, %rsp */ | |
1704 | cfa->base = state->drap_reg; | |
1705 | cfa->offset = state->stack_size = 0; | |
1706 | state->drap = true; | |
baa41469 JP |
1707 | } |
1708 | ||
1709 | /* | |
1710 | * Older versions of GCC (4.8ish) realign the stack | |
1711 | * without DRAP, with a frame pointer. | |
1712 | */ | |
1713 | ||
1714 | break; | |
1715 | ||
1716 | case OP_SRC_POP: | |
ea24213d | 1717 | case OP_SRC_POPF: |
baa41469 JP |
1718 | if (!state->drap && op->dest.type == OP_DEST_REG && |
1719 | op->dest.reg == cfa->base) { | |
1720 | ||
1721 | /* pop %rbp */ | |
1722 | cfa->base = CFI_SP; | |
1723 | } | |
1724 | ||
bf4d1a83 JP |
1725 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1726 | op->dest.type == OP_DEST_REG && | |
1727 | op->dest.reg == state->drap_reg && | |
1728 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1729 | |
bf4d1a83 JP |
1730 | /* drap: pop %drap */ |
1731 | cfa->base = state->drap_reg; | |
1732 | cfa->offset = 0; | |
1733 | state->drap_offset = -1; | |
baa41469 | 1734 | |
bf4d1a83 | 1735 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1736 | |
bf4d1a83 | 1737 | /* pop %reg */ |
baa41469 JP |
1738 | restore_reg(state, op->dest.reg); |
1739 | } | |
1740 | ||
1741 | state->stack_size -= 8; | |
1742 | if (cfa->base == CFI_SP) | |
1743 | cfa->offset -= 8; | |
1744 | ||
1745 | break; | |
1746 | ||
1747 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1748 | if (state->drap && op->src.reg == CFI_BP && |
1749 | op->src.offset == state->drap_offset) { | |
1750 | ||
1751 | /* drap: mov disp(%rbp), %drap */ | |
1752 | cfa->base = state->drap_reg; | |
1753 | cfa->offset = 0; | |
1754 | state->drap_offset = -1; | |
1755 | } | |
1756 | ||
baa41469 JP |
1757 | if (state->drap && op->src.reg == CFI_BP && |
1758 | op->src.offset == regs[op->dest.reg].offset) { | |
1759 | ||
1760 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1761 | restore_reg(state, op->dest.reg); |
1762 | ||
1763 | } else if (op->src.reg == cfa->base && | |
1764 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1765 | ||
1766 | /* mov disp(%rbp), %reg */ | |
1767 | /* mov disp(%rsp), %reg */ | |
1768 | restore_reg(state, op->dest.reg); | |
1769 | } | |
1770 | ||
1771 | break; | |
1772 | ||
1773 | default: | |
1774 | WARN_FUNC("unknown stack-related instruction", | |
1775 | insn->sec, insn->offset); | |
1776 | return -1; | |
1777 | } | |
1778 | ||
1779 | break; | |
1780 | ||
1781 | case OP_DEST_PUSH: | |
ea24213d | 1782 | case OP_DEST_PUSHF: |
baa41469 JP |
1783 | state->stack_size += 8; |
1784 | if (cfa->base == CFI_SP) | |
1785 | cfa->offset += 8; | |
1786 | ||
1787 | if (op->src.type != OP_SRC_REG) | |
1788 | break; | |
1789 | ||
1790 | if (state->drap) { | |
1791 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1792 | ||
1793 | /* drap: push %drap */ | |
1794 | cfa->base = CFI_BP_INDIRECT; | |
1795 | cfa->offset = -state->stack_size; | |
1796 | ||
bf4d1a83 JP |
1797 | /* save drap so we know when to restore it */ |
1798 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1799 | |
1800 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1801 | ||
1802 | /* drap: push %rbp */ | |
1803 | state->stack_size = 0; | |
1804 | ||
1805 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1806 | ||
1807 | /* drap: push %reg */ | |
1808 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1809 | } | |
1810 | ||
1811 | } else { | |
1812 | ||
1813 | /* push %reg */ | |
1814 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1815 | } | |
1816 | ||
1817 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1818 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1819 | cfa->base != CFI_BP) |
1820 | state->bp_scratch = true; | |
1821 | break; | |
1822 | ||
1823 | case OP_DEST_REG_INDIRECT: | |
1824 | ||
1825 | if (state->drap) { | |
1826 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1827 | ||
1828 | /* drap: mov %drap, disp(%rbp) */ | |
1829 | cfa->base = CFI_BP_INDIRECT; | |
1830 | cfa->offset = op->dest.offset; | |
1831 | ||
bf4d1a83 JP |
1832 | /* save drap offset so we know when to restore it */ |
1833 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1834 | } |
1835 | ||
1836 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1837 | ||
1838 | /* drap: mov reg, disp(%rbp) */ | |
1839 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1840 | } | |
1841 | ||
1842 | } else if (op->dest.reg == cfa->base) { | |
1843 | ||
1844 | /* mov reg, disp(%rbp) */ | |
1845 | /* mov reg, disp(%rsp) */ | |
1846 | save_reg(state, op->src.reg, CFI_CFA, | |
1847 | op->dest.offset - state->cfa.offset); | |
1848 | } | |
1849 | ||
1850 | break; | |
1851 | ||
1852 | case OP_DEST_LEAVE: | |
1853 | if ((!state->drap && cfa->base != CFI_BP) || | |
1854 | (state->drap && cfa->base != state->drap_reg)) { | |
1855 | WARN_FUNC("leave instruction with modified stack frame", | |
1856 | insn->sec, insn->offset); | |
1857 | return -1; | |
1858 | } | |
1859 | ||
1860 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1861 | ||
1862 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1863 | restore_reg(state, CFI_BP); | |
1864 | ||
1865 | if (!state->drap) { | |
1866 | cfa->base = CFI_SP; | |
1867 | cfa->offset -= 8; | |
1868 | } | |
1869 | ||
1870 | break; | |
1871 | ||
1872 | case OP_DEST_MEM: | |
ea24213d | 1873 | if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { |
baa41469 JP |
1874 | WARN_FUNC("unknown stack-related memory operation", |
1875 | insn->sec, insn->offset); | |
1876 | return -1; | |
1877 | } | |
1878 | ||
1879 | /* pop mem */ | |
1880 | state->stack_size -= 8; | |
1881 | if (cfa->base == CFI_SP) | |
1882 | cfa->offset -= 8; | |
1883 | ||
1884 | break; | |
1885 | ||
1886 | default: | |
1887 | WARN_FUNC("unknown stack-related instruction", | |
1888 | insn->sec, insn->offset); | |
1889 | return -1; | |
1890 | } | |
1891 | ||
1892 | return 0; | |
1893 | } | |
1894 | ||
1895 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1896 | { | |
1897 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1898 | int i; | |
1899 | ||
1900 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1901 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1902 | insn->sec, insn->offset, | |
1903 | state1->cfa.base, state1->cfa.offset, | |
1904 | state2->cfa.base, state2->cfa.offset); | |
1905 | ||
1906 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1907 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1908 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1909 | sizeof(struct cfi_reg))) | |
1910 | continue; | |
1911 | ||
1912 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1913 | insn->sec, insn->offset, | |
1914 | i, state1->regs[i].base, state1->regs[i].offset, | |
1915 | i, state2->regs[i].base, state2->regs[i].offset); | |
1916 | break; | |
1917 | } | |
1918 | ||
627fce14 JP |
1919 | } else if (state1->type != state2->type) { |
1920 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1921 | insn->sec, insn->offset, state1->type, state2->type); | |
1922 | ||
baa41469 | 1923 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1924 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1925 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1926 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1927 | insn->sec, insn->offset, |
bf4d1a83 JP |
1928 | state1->drap, state1->drap_reg, state1->drap_offset, |
1929 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1930 | |
1931 | } else | |
1932 | return true; | |
1933 | ||
1934 | return false; | |
dcc914f4 JP |
1935 | } |
1936 | ||
ea24213d PZ |
1937 | static inline bool func_uaccess_safe(struct symbol *func) |
1938 | { | |
1939 | if (func) | |
e10cd8fe | 1940 | return func->uaccess_safe; |
ea24213d PZ |
1941 | |
1942 | return false; | |
1943 | } | |
1944 | ||
0c1ddd33 | 1945 | static inline const char *call_dest_name(struct instruction *insn) |
ea24213d PZ |
1946 | { |
1947 | if (insn->call_dest) | |
1948 | return insn->call_dest->name; | |
1949 | ||
1950 | return "{dynamic}"; | |
1951 | } | |
1952 | ||
1953 | static int validate_call(struct instruction *insn, struct insn_state *state) | |
1954 | { | |
1955 | if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { | |
1956 | WARN_FUNC("call to %s() with UACCESS enabled", | |
0c1ddd33 | 1957 | insn->sec, insn->offset, call_dest_name(insn)); |
ea24213d PZ |
1958 | return 1; |
1959 | } | |
1960 | ||
2f0f9e9a PZ |
1961 | if (state->df) { |
1962 | WARN_FUNC("call to %s() with DF set", | |
0c1ddd33 | 1963 | insn->sec, insn->offset, call_dest_name(insn)); |
2f0f9e9a PZ |
1964 | return 1; |
1965 | } | |
1966 | ||
ea24213d PZ |
1967 | return 0; |
1968 | } | |
1969 | ||
54262aa2 PZ |
1970 | static int validate_sibling_call(struct instruction *insn, struct insn_state *state) |
1971 | { | |
1972 | if (has_modified_stack_frame(state)) { | |
1973 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
1974 | insn->sec, insn->offset); | |
1975 | return 1; | |
1976 | } | |
1977 | ||
ea24213d | 1978 | return validate_call(insn, state); |
54262aa2 PZ |
1979 | } |
1980 | ||
a92e92d1 PZ |
1981 | static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) |
1982 | { | |
1983 | if (state->uaccess && !func_uaccess_safe(func)) { | |
1984 | WARN_FUNC("return with UACCESS enabled", | |
1985 | insn->sec, insn->offset); | |
1986 | return 1; | |
1987 | } | |
1988 | ||
1989 | if (!state->uaccess && func_uaccess_safe(func)) { | |
1990 | WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", | |
1991 | insn->sec, insn->offset); | |
1992 | return 1; | |
1993 | } | |
1994 | ||
1995 | if (state->df) { | |
1996 | WARN_FUNC("return with DF set", | |
1997 | insn->sec, insn->offset); | |
1998 | return 1; | |
1999 | } | |
2000 | ||
2001 | if (func && has_modified_stack_frame(state)) { | |
2002 | WARN_FUNC("return with modified stack frame", | |
2003 | insn->sec, insn->offset); | |
2004 | return 1; | |
2005 | } | |
2006 | ||
2007 | if (state->bp_scratch) { | |
2008 | WARN("%s uses BP as a scratch register", | |
2009 | func->name); | |
2010 | return 1; | |
2011 | } | |
2012 | ||
2013 | return 0; | |
2014 | } | |
2015 | ||
dcc914f4 JP |
2016 | /* |
2017 | * Follow the branch starting at the given instruction, and recursively follow | |
2018 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
2019 | * each instruction and validate all the rules described in | |
2020 | * tools/objtool/Documentation/stack-validation.txt. | |
2021 | */ | |
c705cecc JP |
2022 | static int validate_branch(struct objtool_file *file, struct symbol *func, |
2023 | struct instruction *first, struct insn_state state) | |
dcc914f4 JP |
2024 | { |
2025 | struct alternative *alt; | |
39358a03 | 2026 | struct instruction *insn, *next_insn; |
dcc914f4 | 2027 | struct section *sec; |
882a0db9 | 2028 | u8 visited; |
dcc914f4 JP |
2029 | int ret; |
2030 | ||
2031 | insn = first; | |
2032 | sec = insn->sec; | |
dcc914f4 JP |
2033 | |
2034 | if (insn->alt_group && list_empty(&insn->alts)) { | |
2035 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
2036 | sec, insn->offset); | |
12b25729 | 2037 | return 1; |
dcc914f4 JP |
2038 | } |
2039 | ||
2040 | while (1) { | |
39358a03 JP |
2041 | next_insn = next_insn_same_sec(file, insn); |
2042 | ||
13810435 | 2043 | if (file->c_file && func && insn->func && func != insn->func->pfunc) { |
ee97638b JP |
2044 | WARN("%s() falls through to next function %s()", |
2045 | func->name, insn->func->name); | |
2046 | return 1; | |
dcc914f4 JP |
2047 | } |
2048 | ||
4855022a JP |
2049 | if (func && insn->ignore) { |
2050 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
2051 | sec, insn->offset); | |
12b25729 | 2052 | return 1; |
4855022a JP |
2053 | } |
2054 | ||
882a0db9 | 2055 | visited = 1 << state.uaccess; |
dcc914f4 | 2056 | if (insn->visited) { |
39358a03 | 2057 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 2058 | return 1; |
dcc914f4 | 2059 | |
882a0db9 | 2060 | if (insn->visited & visited) |
ea24213d | 2061 | return 0; |
dcc914f4 JP |
2062 | } |
2063 | ||
39358a03 JP |
2064 | if (insn->hint) { |
2065 | if (insn->restore) { | |
2066 | struct instruction *save_insn, *i; | |
2067 | ||
2068 | i = insn; | |
2069 | save_insn = NULL; | |
dbf4aeb0 | 2070 | sym_for_each_insn_continue_reverse(file, func, i) { |
39358a03 JP |
2071 | if (i->save) { |
2072 | save_insn = i; | |
2073 | break; | |
2074 | } | |
2075 | } | |
2076 | ||
2077 | if (!save_insn) { | |
2078 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
2079 | sec, insn->offset); | |
2080 | return 1; | |
2081 | } | |
2082 | ||
2083 | if (!save_insn->visited) { | |
2084 | /* | |
2085 | * Oops, no state to copy yet. | |
2086 | * Hopefully we can reach this | |
2087 | * instruction from another branch | |
2088 | * after the save insn has been | |
2089 | * visited. | |
2090 | */ | |
2091 | if (insn == first) | |
2092 | return 0; | |
2093 | ||
2094 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
2095 | sec, insn->offset); | |
2096 | return 1; | |
2097 | } | |
2098 | ||
2099 | insn->state = save_insn->state; | |
2100 | } | |
2101 | ||
2102 | state = insn->state; | |
2103 | ||
2104 | } else | |
2105 | insn->state = state; | |
dcc914f4 | 2106 | |
882a0db9 | 2107 | insn->visited |= visited; |
baa41469 | 2108 | |
a845c7cf | 2109 | if (!insn->ignore_alts) { |
764eef4b PZ |
2110 | bool skip_orig = false; |
2111 | ||
a845c7cf | 2112 | list_for_each_entry(alt, &insn->alts, list) { |
764eef4b PZ |
2113 | if (alt->skip_orig) |
2114 | skip_orig = true; | |
2115 | ||
c705cecc | 2116 | ret = validate_branch(file, func, alt->insn, state); |
7697eee3 PZ |
2117 | if (ret) { |
2118 | if (backtrace) | |
2119 | BT_FUNC("(alt)", insn); | |
2120 | return ret; | |
2121 | } | |
a845c7cf | 2122 | } |
764eef4b PZ |
2123 | |
2124 | if (skip_orig) | |
2125 | return 0; | |
dcc914f4 JP |
2126 | } |
2127 | ||
2128 | switch (insn->type) { | |
2129 | ||
dcc914f4 | 2130 | case INSN_RETURN: |
a92e92d1 | 2131 | return validate_return(func, insn, &state); |
dcc914f4 JP |
2132 | |
2133 | case INSN_CALL: | |
ea24213d PZ |
2134 | case INSN_CALL_DYNAMIC: |
2135 | ret = validate_call(insn, &state); | |
2136 | if (ret) | |
2137 | return ret; | |
dcc914f4 | 2138 | |
c9bab22b JP |
2139 | if (!no_fp && func && !is_fentry_call(insn) && |
2140 | !has_valid_stack_frame(&state)) { | |
dcc914f4 JP |
2141 | WARN_FUNC("call without frame pointer save/setup", |
2142 | sec, insn->offset); | |
2143 | return 1; | |
2144 | } | |
c9bab22b JP |
2145 | |
2146 | if (dead_end_function(file, insn->call_dest)) | |
2147 | return 0; | |
2148 | ||
dcc914f4 JP |
2149 | break; |
2150 | ||
2151 | case INSN_JUMP_CONDITIONAL: | |
2152 | case INSN_JUMP_UNCONDITIONAL: | |
0c1ddd33 | 2153 | if (func && is_sibling_call(insn)) { |
54262aa2 | 2154 | ret = validate_sibling_call(insn, &state); |
dcc914f4 | 2155 | if (ret) |
54262aa2 | 2156 | return ret; |
4855022a | 2157 | |
0c1ddd33 | 2158 | } else if (insn->jump_dest) { |
c705cecc JP |
2159 | ret = validate_branch(file, func, |
2160 | insn->jump_dest, state); | |
7697eee3 PZ |
2161 | if (ret) { |
2162 | if (backtrace) | |
2163 | BT_FUNC("(branch)", insn); | |
2164 | return ret; | |
2165 | } | |
4855022a | 2166 | } |
dcc914f4 JP |
2167 | |
2168 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
2169 | return 0; | |
2170 | ||
2171 | break; | |
2172 | ||
2173 | case INSN_JUMP_DYNAMIC: | |
b68b9907 | 2174 | case INSN_JUMP_DYNAMIC_CONDITIONAL: |
0c1ddd33 | 2175 | if (func && is_sibling_call(insn)) { |
54262aa2 PZ |
2176 | ret = validate_sibling_call(insn, &state); |
2177 | if (ret) | |
2178 | return ret; | |
dcc914f4 JP |
2179 | } |
2180 | ||
b68b9907 JP |
2181 | if (insn->type == INSN_JUMP_DYNAMIC) |
2182 | return 0; | |
2183 | ||
2184 | break; | |
dcc914f4 | 2185 | |
39358a03 JP |
2186 | case INSN_CONTEXT_SWITCH: |
2187 | if (func && (!next_insn || !next_insn->hint)) { | |
2188 | WARN_FUNC("unsupported instruction in callable function", | |
2189 | sec, insn->offset); | |
2190 | return 1; | |
2191 | } | |
2192 | return 0; | |
2193 | ||
baa41469 JP |
2194 | case INSN_STACK: |
2195 | if (update_insn_state(insn, &state)) | |
12b25729 | 2196 | return 1; |
baa41469 | 2197 | |
ea24213d PZ |
2198 | if (insn->stack_op.dest.type == OP_DEST_PUSHF) { |
2199 | if (!state.uaccess_stack) { | |
2200 | state.uaccess_stack = 1; | |
2201 | } else if (state.uaccess_stack >> 31) { | |
2202 | WARN_FUNC("PUSHF stack exhausted", sec, insn->offset); | |
2203 | return 1; | |
2204 | } | |
2205 | state.uaccess_stack <<= 1; | |
2206 | state.uaccess_stack |= state.uaccess; | |
2207 | } | |
2208 | ||
2209 | if (insn->stack_op.src.type == OP_SRC_POPF) { | |
2210 | if (state.uaccess_stack) { | |
2211 | state.uaccess = state.uaccess_stack & 1; | |
2212 | state.uaccess_stack >>= 1; | |
2213 | if (state.uaccess_stack == 1) | |
2214 | state.uaccess_stack = 0; | |
2215 | } | |
2216 | } | |
2217 | ||
2218 | break; | |
2219 | ||
2220 | case INSN_STAC: | |
2221 | if (state.uaccess) { | |
2222 | WARN_FUNC("recursive UACCESS enable", sec, insn->offset); | |
2223 | return 1; | |
2224 | } | |
2225 | ||
2226 | state.uaccess = true; | |
2227 | break; | |
2228 | ||
2229 | case INSN_CLAC: | |
c705cecc | 2230 | if (!state.uaccess && func) { |
ea24213d PZ |
2231 | WARN_FUNC("redundant UACCESS disable", sec, insn->offset); |
2232 | return 1; | |
2233 | } | |
2234 | ||
2235 | if (func_uaccess_safe(func) && !state.uaccess_stack) { | |
2236 | WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); | |
2237 | return 1; | |
2238 | } | |
2239 | ||
2240 | state.uaccess = false; | |
baa41469 JP |
2241 | break; |
2242 | ||
2f0f9e9a PZ |
2243 | case INSN_STD: |
2244 | if (state.df) | |
2245 | WARN_FUNC("recursive STD", sec, insn->offset); | |
2246 | ||
2247 | state.df = true; | |
2248 | break; | |
2249 | ||
2250 | case INSN_CLD: | |
c705cecc | 2251 | if (!state.df && func) |
2f0f9e9a PZ |
2252 | WARN_FUNC("redundant CLD", sec, insn->offset); |
2253 | ||
2254 | state.df = false; | |
baa41469 JP |
2255 | break; |
2256 | ||
dcc914f4 JP |
2257 | default: |
2258 | break; | |
2259 | } | |
2260 | ||
2261 | if (insn->dead_end) | |
2262 | return 0; | |
2263 | ||
00d96180 JP |
2264 | if (!next_insn) { |
2265 | if (state.cfa.base == CFI_UNDEFINED) | |
2266 | return 0; | |
dcc914f4 JP |
2267 | WARN("%s: unexpected end of section", sec->name); |
2268 | return 1; | |
2269 | } | |
00d96180 JP |
2270 | |
2271 | insn = next_insn; | |
dcc914f4 JP |
2272 | } |
2273 | ||
2274 | return 0; | |
2275 | } | |
2276 | ||
39358a03 JP |
2277 | static int validate_unwind_hints(struct objtool_file *file) |
2278 | { | |
2279 | struct instruction *insn; | |
2280 | int ret, warnings = 0; | |
2281 | struct insn_state state; | |
2282 | ||
2283 | if (!file->hints) | |
2284 | return 0; | |
2285 | ||
2286 | clear_insn_state(&state); | |
2287 | ||
2288 | for_each_insn(file, insn) { | |
2289 | if (insn->hint && !insn->visited) { | |
c705cecc | 2290 | ret = validate_branch(file, insn->func, insn, state); |
7697eee3 PZ |
2291 | if (ret && backtrace) |
2292 | BT_FUNC("<=== (hint)", insn); | |
39358a03 JP |
2293 | warnings += ret; |
2294 | } | |
2295 | } | |
2296 | ||
2297 | return warnings; | |
2298 | } | |
2299 | ||
b5bc2231 PZ |
2300 | static int validate_retpoline(struct objtool_file *file) |
2301 | { | |
2302 | struct instruction *insn; | |
2303 | int warnings = 0; | |
2304 | ||
2305 | for_each_insn(file, insn) { | |
2306 | if (insn->type != INSN_JUMP_DYNAMIC && | |
2307 | insn->type != INSN_CALL_DYNAMIC) | |
2308 | continue; | |
2309 | ||
2310 | if (insn->retpoline_safe) | |
2311 | continue; | |
2312 | ||
ca41b97e PZ |
2313 | /* |
2314 | * .init.text code is ran before userspace and thus doesn't | |
2315 | * strictly need retpolines, except for modules which are | |
2316 | * loaded late, they very much do need retpoline in their | |
2317 | * .init.text | |
2318 | */ | |
2319 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
2320 | continue; | |
2321 | ||
b5bc2231 PZ |
2322 | WARN_FUNC("indirect %s found in RETPOLINE build", |
2323 | insn->sec, insn->offset, | |
2324 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
2325 | ||
2326 | warnings++; | |
2327 | } | |
2328 | ||
2329 | return warnings; | |
2330 | } | |
2331 | ||
dcc914f4 JP |
2332 | static bool is_kasan_insn(struct instruction *insn) |
2333 | { | |
2334 | return (insn->type == INSN_CALL && | |
2335 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
2336 | } | |
2337 | ||
2338 | static bool is_ubsan_insn(struct instruction *insn) | |
2339 | { | |
2340 | return (insn->type == INSN_CALL && | |
2341 | !strcmp(insn->call_dest->name, | |
2342 | "__ubsan_handle_builtin_unreachable")); | |
2343 | } | |
2344 | ||
baa41469 | 2345 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
2346 | { |
2347 | int i; | |
2348 | ||
baa41469 JP |
2349 | if (insn->ignore || insn->type == INSN_NOP) |
2350 | return true; | |
2351 | ||
2352 | /* | |
2353 | * Ignore any unused exceptions. This can happen when a whitelisted | |
2354 | * function has an exception table entry. | |
0e2bb2bc JP |
2355 | * |
2356 | * Also ignore alternative replacement instructions. This can happen | |
2357 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 2358 | */ |
0e2bb2bc JP |
2359 | if (!strcmp(insn->sec->name, ".fixup") || |
2360 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
2361 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2362 | return true; |
2363 | ||
bd841d61 JP |
2364 | if (!insn->func) |
2365 | return false; | |
2366 | ||
2367 | /* | |
2368 | * CONFIG_UBSAN_TRAP inserts a UD2 when it sees | |
2369 | * __builtin_unreachable(). The BUG() macro has an unreachable() after | |
2370 | * the UD2, which causes GCC's undefined trap logic to emit another UD2 | |
2371 | * (or occasionally a JMP to UD2). | |
2372 | */ | |
2373 | if (list_prev_entry(insn, list)->dead_end && | |
2374 | (insn->type == INSN_BUG || | |
2375 | (insn->type == INSN_JUMP_UNCONDITIONAL && | |
2376 | insn->jump_dest && insn->jump_dest->type == INSN_BUG))) | |
2377 | return true; | |
2378 | ||
dcc914f4 JP |
2379 | /* |
2380 | * Check if this (or a subsequent) instruction is related to | |
2381 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2382 | * | |
2383 | * End the search at 5 instructions to avoid going into the weeds. | |
2384 | */ | |
2385 | for (i = 0; i < 5; i++) { | |
2386 | ||
2387 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2388 | return true; | |
2389 | ||
fe24e271 JP |
2390 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2391 | if (insn->jump_dest && | |
2392 | insn->jump_dest->func == insn->func) { | |
2393 | insn = insn->jump_dest; | |
2394 | continue; | |
2395 | } | |
2396 | ||
2397 | break; | |
dcc914f4 JP |
2398 | } |
2399 | ||
baa41469 | 2400 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2401 | break; |
fe24e271 | 2402 | |
dcc914f4 JP |
2403 | insn = list_next_entry(insn, list); |
2404 | } | |
2405 | ||
2406 | return false; | |
2407 | } | |
2408 | ||
350994bf | 2409 | static int validate_section(struct objtool_file *file, struct section *sec) |
dcc914f4 | 2410 | { |
dcc914f4 JP |
2411 | struct symbol *func; |
2412 | struct instruction *insn; | |
baa41469 | 2413 | struct insn_state state; |
dcc914f4 JP |
2414 | int ret, warnings = 0; |
2415 | ||
baa41469 JP |
2416 | clear_insn_state(&state); |
2417 | ||
2418 | state.cfa = initial_func_cfi.cfa; | |
2419 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2420 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2421 | state.stack_size = initial_func_cfi.cfa.offset; | |
2422 | ||
350994bf PZ |
2423 | list_for_each_entry(func, &sec->symbol_list, list) { |
2424 | if (func->type != STT_FUNC) | |
2425 | continue; | |
e10cd8fe | 2426 | |
350994bf PZ |
2427 | if (!func->len) { |
2428 | WARN("%s() is missing an ELF size annotation", | |
2429 | func->name); | |
2430 | warnings++; | |
2431 | } | |
61e9b75a | 2432 | |
350994bf PZ |
2433 | if (func->pfunc != func || func->alias != func) |
2434 | continue; | |
dcc914f4 | 2435 | |
350994bf PZ |
2436 | insn = find_insn(file, sec, func->offset); |
2437 | if (!insn || insn->ignore || insn->visited) | |
2438 | continue; | |
dcc914f4 | 2439 | |
350994bf | 2440 | state.uaccess = func->uaccess_safe; |
ea24213d | 2441 | |
350994bf PZ |
2442 | ret = validate_branch(file, func, insn, state); |
2443 | if (ret && backtrace) | |
2444 | BT_FUNC("<=== (func)", insn); | |
2445 | warnings += ret; | |
dcc914f4 JP |
2446 | } |
2447 | ||
dcc914f4 JP |
2448 | return warnings; |
2449 | } | |
2450 | ||
350994bf PZ |
2451 | static int validate_functions(struct objtool_file *file) |
2452 | { | |
2453 | struct section *sec; | |
2454 | int warnings = 0; | |
2455 | ||
2456 | for_each_sec(file, sec) | |
2457 | warnings += validate_section(file, sec); | |
2458 | ||
2459 | return warnings; | |
2460 | } | |
2461 | ||
baa41469 | 2462 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2463 | { |
2464 | struct instruction *insn; | |
baa41469 JP |
2465 | |
2466 | if (file->ignore_unreachables) | |
2467 | return 0; | |
dcc914f4 JP |
2468 | |
2469 | for_each_insn(file, insn) { | |
baa41469 JP |
2470 | if (insn->visited || ignore_unreachable_insn(insn)) |
2471 | continue; | |
2472 | ||
baa41469 JP |
2473 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2474 | return 1; | |
dcc914f4 JP |
2475 | } |
2476 | ||
baa41469 | 2477 | return 0; |
dcc914f4 JP |
2478 | } |
2479 | ||
0c671812 JP |
2480 | static struct objtool_file file; |
2481 | ||
43a4525f | 2482 | int check(const char *_objname, bool orc) |
dcc914f4 | 2483 | { |
dcc914f4 JP |
2484 | int ret, warnings = 0; |
2485 | ||
2486 | objname = _objname; | |
dcc914f4 | 2487 | |
8e144797 | 2488 | file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2489 | if (!file.elf) |
dcc914f4 | 2490 | return 1; |
dcc914f4 JP |
2491 | |
2492 | INIT_LIST_HEAD(&file.insn_list); | |
2493 | hash_init(file.insn_hash); | |
dcc914f4 | 2494 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2495 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2496 | file.hints = false; |
dcc914f4 | 2497 | |
baa41469 JP |
2498 | arch_initial_func_cfi_state(&initial_func_cfi); |
2499 | ||
dcc914f4 JP |
2500 | ret = decode_sections(&file); |
2501 | if (ret < 0) | |
2502 | goto out; | |
2503 | warnings += ret; | |
2504 | ||
baa41469 | 2505 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2506 | goto out; |
dcc914f4 | 2507 | |
b5bc2231 PZ |
2508 | if (retpoline) { |
2509 | ret = validate_retpoline(&file); | |
2510 | if (ret < 0) | |
2511 | return ret; | |
2512 | warnings += ret; | |
2513 | } | |
2514 | ||
baa41469 | 2515 | ret = validate_functions(&file); |
dcc914f4 JP |
2516 | if (ret < 0) |
2517 | goto out; | |
2518 | warnings += ret; | |
2519 | ||
39358a03 JP |
2520 | ret = validate_unwind_hints(&file); |
2521 | if (ret < 0) | |
2522 | goto out; | |
2523 | warnings += ret; | |
2524 | ||
baa41469 JP |
2525 | if (!warnings) { |
2526 | ret = validate_reachable_instructions(&file); | |
2527 | if (ret < 0) | |
2528 | goto out; | |
2529 | warnings += ret; | |
2530 | } | |
2531 | ||
627fce14 JP |
2532 | if (orc) { |
2533 | ret = create_orc(&file); | |
2534 | if (ret < 0) | |
2535 | goto out; | |
2536 | ||
2537 | ret = create_orc_sections(&file); | |
2538 | if (ret < 0) | |
2539 | goto out; | |
2540 | ||
2541 | ret = elf_write(file.elf); | |
2542 | if (ret < 0) | |
2543 | goto out; | |
2544 | } | |
2545 | ||
dcc914f4 | 2546 | out: |
644592d3 JP |
2547 | if (ret < 0) { |
2548 | /* | |
2549 | * Fatal error. The binary is corrupt or otherwise broken in | |
2550 | * some way, or objtool itself is broken. Fail the kernel | |
2551 | * build. | |
2552 | */ | |
2553 | return ret; | |
2554 | } | |
2555 | ||
dcc914f4 JP |
2556 | return 0; |
2557 | } |