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