Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : #include <linux/objtool.h>
3 : #include <linux/module.h>
4 : #include <linux/sort.h>
5 : #include <asm/ptrace.h>
6 : #include <asm/stacktrace.h>
7 : #include <asm/unwind.h>
8 : #include <asm/orc_types.h>
9 : #include <asm/orc_lookup.h>
10 :
11 : #define orc_warn(fmt, ...) \
12 : printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
13 :
14 : #define orc_warn_current(args...) \
15 : ({ \
16 : if (state->task == current && !state->error) \
17 : orc_warn(args); \
18 : })
19 :
20 : extern int __start_orc_unwind_ip[];
21 : extern int __stop_orc_unwind_ip[];
22 : extern struct orc_entry __start_orc_unwind[];
23 : extern struct orc_entry __stop_orc_unwind[];
24 :
25 : static bool orc_init __ro_after_init;
26 : static unsigned int lookup_num_blocks __ro_after_init;
27 :
28 432627535 : static inline unsigned long orc_ip(const int *ip)
29 : {
30 432627535 : return (unsigned long)ip + *ip;
31 : }
32 :
33 139654669 : static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
34 : unsigned int num_entries, unsigned long ip)
35 : {
36 139654669 : int *first = ip_table;
37 139654669 : int *last = ip_table + num_entries - 1;
38 139654669 : int *mid = first, *found = first;
39 :
40 139654669 : if (!num_entries)
41 : return NULL;
42 :
43 : /*
44 : * Do a binary range search to find the rightmost duplicate of a given
45 : * starting address. Some entries are section terminators which are
46 : * "weak" entries for ensuring there are no gaps. They should be
47 : * ignored when they conflict with a real entry.
48 : */
49 572282204 : while (first <= last) {
50 432627535 : mid = first + ((last - first) / 2);
51 :
52 432627535 : if (orc_ip(mid) <= ip) {
53 259673671 : found = mid;
54 259673671 : first = mid + 1;
55 : } else
56 172953864 : last = mid - 1;
57 : }
58 :
59 139654669 : return u_table + (found - ip_table);
60 : }
61 :
62 : #ifdef CONFIG_MODULES
63 : static struct orc_entry *orc_module_find(unsigned long ip)
64 : {
65 : struct module *mod;
66 :
67 : mod = __module_address(ip);
68 : if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
69 : return NULL;
70 : return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
71 : mod->arch.num_orcs, ip);
72 : }
73 : #else
74 0 : static struct orc_entry *orc_module_find(unsigned long ip)
75 : {
76 0 : return NULL;
77 : }
78 : #endif
79 :
80 : #ifdef CONFIG_DYNAMIC_FTRACE
81 : static struct orc_entry *orc_find(unsigned long ip);
82 :
83 : /*
84 : * Ftrace dynamic trampolines do not have orc entries of their own.
85 : * But they are copies of the ftrace entries that are static and
86 : * defined in ftrace_*.S, which do have orc entries.
87 : *
88 : * If the unwinder comes across a ftrace trampoline, then find the
89 : * ftrace function that was used to create it, and use that ftrace
90 : * function's orc entry, as the placement of the return code in
91 : * the stack will be identical.
92 : */
93 : static struct orc_entry *orc_ftrace_find(unsigned long ip)
94 : {
95 : struct ftrace_ops *ops;
96 : unsigned long caller;
97 :
98 : ops = ftrace_ops_trampoline(ip);
99 : if (!ops)
100 : return NULL;
101 :
102 : if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
103 : caller = (unsigned long)ftrace_regs_call;
104 : else
105 : caller = (unsigned long)ftrace_call;
106 :
107 : /* Prevent unlikely recursion */
108 : if (ip == caller)
109 : return NULL;
110 :
111 : return orc_find(caller);
112 : }
113 : #else
114 : static struct orc_entry *orc_ftrace_find(unsigned long ip)
115 : {
116 : return NULL;
117 : }
118 : #endif
119 :
120 : /*
121 : * If we crash with IP==0, the last successfully executed instruction
122 : * was probably an indirect function call with a NULL function pointer,
123 : * and we don't have unwind information for NULL.
124 : * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
125 : * pointer into its parent and then continue normally from there.
126 : */
127 : static struct orc_entry null_orc_entry = {
128 : .sp_offset = sizeof(long),
129 : .sp_reg = ORC_REG_SP,
130 : .bp_reg = ORC_REG_UNDEFINED,
131 : .type = UNWIND_HINT_TYPE_CALL
132 : };
133 :
134 : /* Fake frame pointer entry -- used as a fallback for generated code */
135 : static struct orc_entry orc_fp_entry = {
136 : .type = UNWIND_HINT_TYPE_CALL,
137 : .sp_reg = ORC_REG_BP,
138 : .sp_offset = 16,
139 : .bp_reg = ORC_REG_PREV_SP,
140 : .bp_offset = -16,
141 : .end = 0,
142 : };
143 :
144 138432498 : static struct orc_entry *orc_find(unsigned long ip)
145 : {
146 138432498 : static struct orc_entry *orc;
147 :
148 138432498 : if (ip == 0)
149 : return &null_orc_entry;
150 :
151 : /* For non-init vmlinux addresses, use the fast lookup table: */
152 138432498 : if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
153 137599867 : unsigned int idx, start, stop;
154 :
155 137599867 : idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
156 :
157 137599867 : if (unlikely((idx >= lookup_num_blocks-1))) {
158 0 : orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
159 : idx, lookup_num_blocks, (void *)ip);
160 0 : return NULL;
161 : }
162 :
163 137599867 : start = orc_lookup[idx];
164 137599867 : stop = orc_lookup[idx + 1] + 1;
165 :
166 137599867 : if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
167 : (__start_orc_unwind + stop > __stop_orc_unwind))) {
168 0 : orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
169 : idx, lookup_num_blocks, start, stop, (void *)ip);
170 0 : return NULL;
171 : }
172 :
173 137599867 : return __orc_find(__start_orc_unwind_ip + start,
174 : __start_orc_unwind + start, stop - start, ip);
175 : }
176 :
177 : /* vmlinux .init slow lookup: */
178 832631 : if (init_kernel_text(ip))
179 1072635 : return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
180 1072635 : __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
181 :
182 : /* Module lookup: */
183 0 : orc = orc_module_find(ip);
184 0 : if (orc)
185 : return orc;
186 :
187 139580854 : return orc_ftrace_find(ip);
188 : }
189 :
190 : #ifdef CONFIG_MODULES
191 :
192 : static DEFINE_MUTEX(sort_mutex);
193 : static int *cur_orc_ip_table = __start_orc_unwind_ip;
194 : static struct orc_entry *cur_orc_table = __start_orc_unwind;
195 :
196 : static void orc_sort_swap(void *_a, void *_b, int size)
197 : {
198 : struct orc_entry *orc_a, *orc_b;
199 : struct orc_entry orc_tmp;
200 : int *a = _a, *b = _b, tmp;
201 : int delta = _b - _a;
202 :
203 : /* Swap the .orc_unwind_ip entries: */
204 : tmp = *a;
205 : *a = *b + delta;
206 : *b = tmp - delta;
207 :
208 : /* Swap the corresponding .orc_unwind entries: */
209 : orc_a = cur_orc_table + (a - cur_orc_ip_table);
210 : orc_b = cur_orc_table + (b - cur_orc_ip_table);
211 : orc_tmp = *orc_a;
212 : *orc_a = *orc_b;
213 : *orc_b = orc_tmp;
214 : }
215 :
216 : static int orc_sort_cmp(const void *_a, const void *_b)
217 : {
218 : struct orc_entry *orc_a;
219 : const int *a = _a, *b = _b;
220 : unsigned long a_val = orc_ip(a);
221 : unsigned long b_val = orc_ip(b);
222 :
223 : if (a_val > b_val)
224 : return 1;
225 : if (a_val < b_val)
226 : return -1;
227 :
228 : /*
229 : * The "weak" section terminator entries need to always be on the left
230 : * to ensure the lookup code skips them in favor of real entries.
231 : * These terminator entries exist to handle any gaps created by
232 : * whitelisted .o files which didn't get objtool generation.
233 : */
234 : orc_a = cur_orc_table + (a - cur_orc_ip_table);
235 : return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
236 : }
237 :
238 : void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
239 : void *_orc, size_t orc_size)
240 : {
241 : int *orc_ip = _orc_ip;
242 : struct orc_entry *orc = _orc;
243 : unsigned int num_entries = orc_ip_size / sizeof(int);
244 :
245 : WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
246 : orc_size % sizeof(*orc) != 0 ||
247 : num_entries != orc_size / sizeof(*orc));
248 :
249 : /*
250 : * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
251 : * associate an .orc_unwind_ip table entry with its corresponding
252 : * .orc_unwind entry so they can both be swapped.
253 : */
254 : mutex_lock(&sort_mutex);
255 : cur_orc_ip_table = orc_ip;
256 : cur_orc_table = orc;
257 : sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
258 : mutex_unlock(&sort_mutex);
259 :
260 : mod->arch.orc_unwind_ip = orc_ip;
261 : mod->arch.orc_unwind = orc;
262 : mod->arch.num_orcs = num_entries;
263 : }
264 : #endif
265 :
266 1 : void __init unwind_init(void)
267 : {
268 1 : size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
269 1 : size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
270 1 : size_t num_entries = orc_ip_size / sizeof(int);
271 1 : struct orc_entry *orc;
272 1 : int i;
273 :
274 1 : if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
275 1 : orc_size % sizeof(struct orc_entry) != 0 ||
276 1 : num_entries != orc_size / sizeof(struct orc_entry)) {
277 0 : orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
278 0 : return;
279 : }
280 :
281 : /*
282 : * Note, the orc_unwind and orc_unwind_ip tables were already
283 : * sorted at build time via the 'sorttable' tool.
284 : * It's ready for binary search straight away, no need to sort it.
285 : */
286 :
287 : /* Initialize the fast lookup table: */
288 1 : lookup_num_blocks = orc_lookup_end - orc_lookup;
289 81956 : for (i = 0; i < lookup_num_blocks-1; i++) {
290 163910 : orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
291 : num_entries,
292 81955 : LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
293 81955 : if (!orc) {
294 0 : orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
295 0 : return;
296 : }
297 :
298 81955 : orc_lookup[i] = orc - __start_orc_unwind;
299 : }
300 :
301 : /* Initialize the ending block: */
302 1 : orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
303 : LOOKUP_STOP_IP);
304 1 : if (!orc) {
305 0 : orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
306 0 : return;
307 : }
308 1 : orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
309 :
310 1 : orc_init = true;
311 : }
312 :
313 129441792 : unsigned long unwind_get_return_address(struct unwind_state *state)
314 : {
315 129441792 : if (unwind_done(state))
316 : return 0;
317 :
318 129496481 : return __kernel_text_address(state->ip) ? state->ip : 0;
319 : }
320 : EXPORT_SYMBOL_GPL(unwind_get_return_address);
321 :
322 231 : unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
323 : {
324 231 : if (unwind_done(state))
325 : return NULL;
326 :
327 231 : if (state->regs)
328 21 : return &state->regs->ip;
329 :
330 210 : if (state->sp)
331 210 : return (unsigned long *)state->sp - 1;
332 :
333 : return NULL;
334 : }
335 :
336 223726238 : static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
337 : size_t len)
338 : {
339 223726238 : struct stack_info *info = &state->stack_info;
340 223726238 : void *addr = (void *)_addr;
341 :
342 224576443 : if (!on_stack(info, addr, len) &&
343 850582 : (get_stack_info(addr, state->task, info, &state->stack_mask)))
344 0 : return false;
345 :
346 : return true;
347 : }
348 :
349 217804992 : static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
350 : unsigned long *val)
351 : {
352 217804992 : if (!stack_access_ok(state, addr, sizeof(long)))
353 : return false;
354 :
355 218273571 : *val = READ_ONCE_NOCHECK(*(unsigned long *)addr);
356 218270211 : return true;
357 : }
358 :
359 6327349 : static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
360 : unsigned long *ip, unsigned long *sp)
361 : {
362 6327349 : struct pt_regs *regs = (struct pt_regs *)addr;
363 :
364 : /* x86-32 support will be more complicated due to the ®s->sp hack */
365 6327349 : BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32));
366 :
367 6327349 : if (!stack_access_ok(state, addr, sizeof(struct pt_regs)))
368 : return false;
369 :
370 6327560 : *ip = READ_ONCE_NOCHECK(regs->ip);
371 6327474 : *sp = READ_ONCE_NOCHECK(regs->sp);
372 6327548 : return true;
373 : }
374 :
375 0 : static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr,
376 : unsigned long *ip, unsigned long *sp)
377 : {
378 0 : struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET;
379 :
380 0 : if (!stack_access_ok(state, addr, IRET_FRAME_SIZE))
381 : return false;
382 :
383 0 : *ip = READ_ONCE_NOCHECK(regs->ip);
384 0 : *sp = READ_ONCE_NOCHECK(regs->sp);
385 0 : return true;
386 : }
387 :
388 : /*
389 : * If state->regs is non-NULL, and points to a full pt_regs, just get the reg
390 : * value from state->regs.
391 : *
392 : * Otherwise, if state->regs just points to IRET regs, and the previous frame
393 : * had full regs, it's safe to get the value from the previous regs. This can
394 : * happen when early/late IRQ entry code gets interrupted by an NMI.
395 : */
396 49158271 : static bool get_reg(struct unwind_state *state, unsigned int reg_off,
397 : unsigned long *val)
398 : {
399 49158271 : unsigned int reg = reg_off/8;
400 :
401 49158271 : if (!state->regs)
402 : return false;
403 :
404 6326968 : if (state->full_regs) {
405 6326968 : *val = READ_ONCE_NOCHECK(((unsigned long *)state->regs)[reg]);
406 6326221 : return true;
407 : }
408 :
409 0 : if (state->prev_regs) {
410 0 : *val = READ_ONCE_NOCHECK(((unsigned long *)state->prev_regs)[reg]);
411 0 : return true;
412 : }
413 :
414 : return false;
415 : }
416 :
417 137893596 : bool unwind_next_frame(struct unwind_state *state)
418 : {
419 137893596 : unsigned long ip_p, sp, tmp, orig_ip = state->ip, prev_sp = state->sp;
420 137893596 : enum stack_type prev_type = state->stack_info.type;
421 137893596 : struct orc_entry *orc;
422 137893596 : bool indirect = false;
423 :
424 137893596 : if (unwind_done(state))
425 : return false;
426 :
427 : /* Don't let modules unload while we're reading their ORC data. */
428 137893596 : preempt_disable();
429 :
430 : /* End-of-stack check for user tasks: */
431 138478586 : if (state->regs && user_mode(state->regs))
432 0 : goto the_end;
433 :
434 : /*
435 : * Find the orc_entry associated with the text address.
436 : *
437 : * For a call frame (as opposed to a signal frame), state->ip points to
438 : * the instruction after the call. That instruction's stack layout
439 : * could be different from the call instruction's layout, for example
440 : * if the call was to a noreturn function. So get the ORC data for the
441 : * call instruction itself.
442 : */
443 138478586 : orc = orc_find(state->signal ? state->ip : state->ip - 1);
444 139666787 : if (!orc) {
445 : /*
446 : * As a fallback, try to assume this code uses a frame pointer.
447 : * This is useful for generated code, like BPF, which ORC
448 : * doesn't know about. This is just a guess, so the rest of
449 : * the unwind is no longer considered reliable.
450 : */
451 0 : orc = &orc_fp_entry;
452 0 : state->error = true;
453 : }
454 :
455 : /* End-of-stack check for kernel threads: */
456 139666787 : if (orc->sp_reg == ORC_REG_UNDEFINED) {
457 1448026 : if (!orc->end)
458 11 : goto err;
459 :
460 1448015 : goto the_end;
461 : }
462 :
463 : /* Find the previous frame's stack: */
464 138218761 : switch (orc->sp_reg) {
465 126760380 : case ORC_REG_SP:
466 126760380 : sp = state->sp + orc->sp_offset;
467 126760380 : break;
468 :
469 10600252 : case ORC_REG_BP:
470 10600252 : sp = state->bp + orc->sp_offset;
471 10600252 : break;
472 :
473 850756 : case ORC_REG_SP_INDIRECT:
474 850756 : sp = state->sp;
475 850756 : indirect = true;
476 850756 : break;
477 :
478 7373 : case ORC_REG_BP_INDIRECT:
479 7373 : sp = state->bp + orc->sp_offset;
480 7373 : indirect = true;
481 7373 : break;
482 :
483 0 : case ORC_REG_R10:
484 0 : if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) {
485 0 : orc_warn_current("missing R10 value at %pB\n",
486 : (void *)state->ip);
487 0 : goto err;
488 : }
489 : break;
490 :
491 0 : case ORC_REG_R13:
492 0 : if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
493 0 : orc_warn_current("missing R13 value at %pB\n",
494 : (void *)state->ip);
495 0 : goto err;
496 : }
497 : break;
498 :
499 0 : case ORC_REG_DI:
500 0 : if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
501 0 : orc_warn_current("missing RDI value at %pB\n",
502 : (void *)state->ip);
503 0 : goto err;
504 : }
505 : break;
506 :
507 0 : case ORC_REG_DX:
508 0 : if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) {
509 0 : orc_warn_current("missing DX value at %pB\n",
510 : (void *)state->ip);
511 0 : goto err;
512 : }
513 : break;
514 :
515 0 : default:
516 0 : orc_warn("unknown SP base reg %d at %pB\n",
517 : orc->sp_reg, (void *)state->ip);
518 0 : goto err;
519 : }
520 :
521 138218761 : if (indirect) {
522 858129 : if (!deref_stack_reg(state, sp, &sp))
523 0 : goto err;
524 :
525 858016 : if (orc->sp_reg == ORC_REG_SP_INDIRECT)
526 850700 : sp += orc->sp_offset;
527 : }
528 :
529 : /* Find IP, SP and possibly regs: */
530 138218648 : switch (orc->type) {
531 131639519 : case UNWIND_HINT_TYPE_CALL:
532 131639519 : ip_p = sp - sizeof(long);
533 :
534 131639519 : if (!deref_stack_reg(state, ip_p, &state->ip))
535 0 : goto err;
536 :
537 131333178 : state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
538 : state->ip, (void *)ip_p);
539 :
540 131333178 : state->sp = sp;
541 131333178 : state->regs = NULL;
542 131333178 : state->prev_regs = NULL;
543 131333178 : state->signal = false;
544 131333178 : break;
545 :
546 6327432 : case UNWIND_HINT_TYPE_REGS:
547 6327432 : if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
548 0 : orc_warn_current("can't access registers at %pB\n",
549 : (void *)orig_ip);
550 0 : goto err;
551 : }
552 :
553 6327504 : state->regs = (struct pt_regs *)sp;
554 6327504 : state->prev_regs = NULL;
555 6327504 : state->full_regs = true;
556 6327504 : state->signal = true;
557 6327504 : break;
558 :
559 0 : case UNWIND_HINT_TYPE_REGS_PARTIAL:
560 0 : if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
561 0 : orc_warn_current("can't access iret registers at %pB\n",
562 : (void *)orig_ip);
563 0 : goto err;
564 : }
565 :
566 789662 : if (state->full_regs)
567 0 : state->prev_regs = state->regs;
568 789662 : state->regs = (void *)sp - IRET_FRAME_OFFSET;
569 789662 : state->full_regs = false;
570 789662 : state->signal = true;
571 789662 : break;
572 :
573 251697 : default:
574 251697 : orc_warn("unknown .orc_unwind entry type %d at %pB\n",
575 : orc->type, (void *)orig_ip);
576 251697 : goto err;
577 : }
578 :
579 : /* Find BP: */
580 138450344 : switch (orc->bp_reg) {
581 49080425 : case ORC_REG_UNDEFINED:
582 49080425 : if (get_reg(state, offsetof(struct pt_regs, bp), &tmp))
583 6326827 : state->bp = tmp;
584 : break;
585 :
586 89362546 : case ORC_REG_PREV_SP:
587 89362546 : if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
588 0 : goto err;
589 : break;
590 :
591 7373 : case ORC_REG_BP:
592 7373 : if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
593 0 : goto err;
594 : break;
595 :
596 0 : default:
597 0 : orc_warn("unknown BP base reg %d for ip %pB\n",
598 : orc->bp_reg, (void *)orig_ip);
599 0 : goto err;
600 : }
601 :
602 : /* Prevent a recursive loop due to bad ORC data: */
603 138113166 : if (state->stack_info.type == prev_type &&
604 135207455 : on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
605 : state->sp <= prev_sp) {
606 0 : orc_warn_current("stack going in the wrong direction? at %pB\n",
607 : (void *)orig_ip);
608 0 : goto err;
609 : }
610 :
611 138113166 : preempt_enable();
612 136364081 : return true;
613 :
614 251708 : err:
615 251708 : state->error = true;
616 :
617 1699723 : the_end:
618 1699723 : preempt_enable();
619 1447795 : state->stack_info.type = STACK_TYPE_UNKNOWN;
620 1447795 : return false;
621 : }
622 : EXPORT_SYMBOL_GPL(unwind_next_frame);
623 :
624 7000192 : void __unwind_start(struct unwind_state *state, struct task_struct *task,
625 : struct pt_regs *regs, unsigned long *first_frame)
626 : {
627 7000192 : memset(state, 0, sizeof(*state));
628 7000192 : state->task = task;
629 :
630 7000192 : if (!orc_init)
631 370 : goto err;
632 :
633 : /*
634 : * Refuse to unwind the stack of a task while it's executing on another
635 : * CPU. This check is racy, but that's ok: the unwinder has other
636 : * checks to prevent it from going off the rails.
637 : */
638 13999644 : if (task_on_another_cpu(task))
639 0 : goto err;
640 :
641 6999822 : if (regs) {
642 1 : if (user_mode(regs))
643 0 : goto the_end;
644 :
645 1 : state->ip = regs->ip;
646 1 : state->sp = regs->sp;
647 1 : state->bp = regs->bp;
648 1 : state->regs = regs;
649 1 : state->full_regs = true;
650 1 : state->signal = true;
651 :
652 6999821 : } else if (task == current) {
653 6999821 : asm volatile("lea (%%rip), %0\n\t"
654 : "mov %%rsp, %1\n\t"
655 : "mov %%rbp, %2\n\t"
656 : : "=r" (state->ip), "=r" (state->sp),
657 : "=r" (state->bp));
658 :
659 : } else {
660 0 : struct inactive_task_frame *frame = (void *)task->thread.sp;
661 :
662 0 : state->sp = task->thread.sp + sizeof(*frame);
663 0 : state->bp = READ_ONCE_NOCHECK(frame->bp);
664 0 : state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
665 0 : state->signal = (void *)state->ip == ret_from_fork;
666 : }
667 :
668 6999651 : if (get_stack_info((unsigned long *)state->sp, state->task,
669 : &state->stack_info, &state->stack_mask)) {
670 : /*
671 : * We weren't on a valid stack. It's possible that
672 : * we overflowed a valid stack into a guard page.
673 : * See if the next page up is valid so that we can
674 : * generate some kind of backtrace if this happens.
675 : */
676 0 : void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
677 0 : state->error = true;
678 0 : if (get_stack_info(next_page, state->task, &state->stack_info,
679 : &state->stack_mask))
680 : return;
681 : }
682 :
683 : /*
684 : * The caller can provide the address of the first frame directly
685 : * (first_frame) or indirectly (regs->sp) to indicate which stack frame
686 : * to start unwinding at. Skip ahead until we reach it.
687 : */
688 :
689 : /* When starting from regs, skip the regs frame: */
690 6991142 : if (regs) {
691 1 : unwind_next_frame(state);
692 1 : return;
693 : }
694 :
695 : /* Otherwise, skip ahead to the user-specified starting frame: */
696 20925736 : while (!unwind_done(state) &&
697 20925736 : (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
698 20925736 : state->sp < (unsigned long)first_frame))
699 13926964 : unwind_next_frame(state);
700 :
701 : return;
702 :
703 370 : err:
704 370 : state->error = true;
705 : the_end:
706 : state->stack_info.type = STACK_TYPE_UNKNOWN;
707 : }
708 : EXPORT_SYMBOL_GPL(__unwind_start);
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