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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
116static struct orc_entry *orc_find(unsigned long ip)
117{
118 static struct orc_entry *orc;
119
120 if (!orc_init)
121 return NULL;
122
123 /* For non-init vmlinux addresses, use the fast lookup table: */
124 if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
125 unsigned int idx, start, stop;
126
127 idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
128
129 if (unlikely((idx >= lookup_num_blocks-1))) {
130 orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
131 idx, lookup_num_blocks, (void *)ip);
132 return NULL;
133 }
134
135 start = orc_lookup[idx];
136 stop = orc_lookup[idx + 1] + 1;
137
138 if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
139 (__start_orc_unwind + stop > __stop_orc_unwind))) {
140 orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
141 idx, lookup_num_blocks, start, stop, (void *)ip);
142 return NULL;
143 }
144
145 return __orc_find(__start_orc_unwind_ip + start,
146 __start_orc_unwind + start, stop - start, ip);
147 }
148
149 /* vmlinux .init slow lookup: */
150 if (init_kernel_text(ip))
151 return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
152 __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
153
154 /* Module lookup: */
155 orc = orc_module_find(ip);
156 if (orc)
157 return orc;
158
159 return orc_ftrace_find(ip);
160}
161
162static void orc_sort_swap(void *_a, void *_b, int size)
163{
164 struct orc_entry *orc_a, *orc_b;
165 struct orc_entry orc_tmp;
166 int *a = _a, *b = _b, tmp;
167 int delta = _b - _a;
168
169 /* Swap the .orc_unwind_ip entries: */
170 tmp = *a;
171 *a = *b + delta;
172 *b = tmp - delta;
173
174 /* Swap the corresponding .orc_unwind entries: */
175 orc_a = cur_orc_table + (a - cur_orc_ip_table);
176 orc_b = cur_orc_table + (b - cur_orc_ip_table);
177 orc_tmp = *orc_a;
178 *orc_a = *orc_b;
179 *orc_b = orc_tmp;
180}
181
182static int orc_sort_cmp(const void *_a, const void *_b)
183{
184 struct orc_entry *orc_a;
185 const int *a = _a, *b = _b;
186 unsigned long a_val = orc_ip(a);
187 unsigned long b_val = orc_ip(b);
188
189 if (a_val > b_val)
190 return 1;
191 if (a_val < b_val)
192 return -1;
193
194 /*
195 * The "weak" section terminator entries need to always be on the left
196 * to ensure the lookup code skips them in favor of real entries.
197 * These terminator entries exist to handle any gaps created by
198 * whitelisted .o files which didn't get objtool generation.
199 */
200 orc_a = cur_orc_table + (a - cur_orc_ip_table);
201 return orc_a->sp_reg == ORC_REG_UNDEFINED ? -1 : 1;
202}
203
204#ifdef CONFIG_MODULES
205void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
206 void *_orc, size_t orc_size)
207{
208 int *orc_ip = _orc_ip;
209 struct orc_entry *orc = _orc;
210 unsigned int num_entries = orc_ip_size / sizeof(int);
211
212 WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
213 orc_size % sizeof(*orc) != 0 ||
214 num_entries != orc_size / sizeof(*orc));
215
216 /*
217 * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
218 * associate an .orc_unwind_ip table entry with its corresponding
219 * .orc_unwind entry so they can both be swapped.
220 */
221 mutex_lock(&sort_mutex);
222 cur_orc_ip_table = orc_ip;
223 cur_orc_table = orc;
224 sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
225 mutex_unlock(&sort_mutex);
226
227 mod->arch.orc_unwind_ip = orc_ip;
228 mod->arch.orc_unwind = orc;
229 mod->arch.num_orcs = num_entries;
230}
231#endif
232
233void __init unwind_init(void)
234{
235 size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
236 size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
237 size_t num_entries = orc_ip_size / sizeof(int);
238 struct orc_entry *orc;
239 int i;
240
241 if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
242 orc_size % sizeof(struct orc_entry) != 0 ||
243 num_entries != orc_size / sizeof(struct orc_entry)) {
244 orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
245 return;
246 }
247
248 /* Sort the .orc_unwind and .orc_unwind_ip tables: */
249 sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
250 orc_sort_swap);
251
252 /* Initialize the fast lookup table: */
253 lookup_num_blocks = orc_lookup_end - orc_lookup;
254 for (i = 0; i < lookup_num_blocks-1; i++) {
255 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
256 num_entries,
257 LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
258 if (!orc) {
259 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
260 return;
261 }
262
263 orc_lookup[i] = orc - __start_orc_unwind;
264 }
265
266 /* Initialize the ending block: */
267 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
268 LOOKUP_STOP_IP);
269 if (!orc) {
270 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
271 return;
272 }
273 orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
274
275 orc_init = true;
276}
277
278unsigned long unwind_get_return_address(struct unwind_state *state)
279{
280 if (unwind_done(state))
281 return 0;
282
283 return __kernel_text_address(state->ip) ? state->ip : 0;
284}
285EXPORT_SYMBOL_GPL(unwind_get_return_address);
286
287unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
288{
289 if (unwind_done(state))
290 return NULL;
291
292 if (state->regs)
293 return &state->regs->ip;
294
295 if (state->sp)
296 return (unsigned long *)state->sp - 1;
297
298 return NULL;
299}
300
301static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
302 size_t len)
303{
304 struct stack_info *info = &state->stack_info;
305 void *addr = (void *)_addr;
306
307 if (!on_stack(info, addr, len) &&
308 (get_stack_info(addr, state->task, info, &state->stack_mask)))
309 return false;
310
311 return true;
312}
313
314static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
315 unsigned long *val)
316{
317 if (!stack_access_ok(state, addr, sizeof(long)))
318 return false;
319
320 *val = READ_ONCE_NOCHECK(*(unsigned long *)addr);
321 return true;
322}
323
324static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
325 unsigned long *ip, unsigned long *sp)
326{
327 struct pt_regs *regs = (struct pt_regs *)addr;
328
329 /* x86-32 support will be more complicated due to the ®s->sp hack */
330 BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32));
331
332 if (!stack_access_ok(state, addr, sizeof(struct pt_regs)))
333 return false;
334
335 *ip = regs->ip;
336 *sp = regs->sp;
337 return true;
338}
339
340static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr,
341 unsigned long *ip, unsigned long *sp)
342{
343 struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET;
344
345 if (!stack_access_ok(state, addr, IRET_FRAME_SIZE))
346 return false;
347
348 *ip = regs->ip;
349 *sp = regs->sp;
350 return true;
351}
352
353bool unwind_next_frame(struct unwind_state *state)
354{
355 unsigned long ip_p, sp, orig_ip, prev_sp = state->sp;
356 enum stack_type prev_type = state->stack_info.type;
357 struct orc_entry *orc;
358 bool indirect = false;
359
360 if (unwind_done(state))
361 return false;
362
363 /* Don't let modules unload while we're reading their ORC data. */
364 preempt_disable();
365
366 /* Have we reached the end? */
367 if (state->regs && user_mode(state->regs))
368 goto done;
369
370 /*
371 * Find the orc_entry associated with the text address.
372 *
373 * Decrement call return addresses by one so they work for sibling
374 * calls and calls to noreturn functions.
375 */
376 orc = orc_find(state->signal ? state->ip : state->ip - 1);
377 if (!orc || orc->sp_reg == ORC_REG_UNDEFINED)
378 goto done;
379 orig_ip = state->ip;
380
381 /* Find the previous frame's stack: */
382 switch (orc->sp_reg) {
383 case ORC_REG_SP:
384 sp = state->sp + orc->sp_offset;
385 break;
386
387 case ORC_REG_BP:
388 sp = state->bp + orc->sp_offset;
389 break;
390
391 case ORC_REG_SP_INDIRECT:
392 sp = state->sp + orc->sp_offset;
393 indirect = true;
394 break;
395
396 case ORC_REG_BP_INDIRECT:
397 sp = state->bp + orc->sp_offset;
398 indirect = true;
399 break;
400
401 case ORC_REG_R10:
402 if (!state->regs || !state->full_regs) {
403 orc_warn("missing regs for base reg R10 at ip %pB\n",
404 (void *)state->ip);
405 goto done;
406 }
407 sp = state->regs->r10;
408 break;
409
410 case ORC_REG_R13:
411 if (!state->regs || !state->full_regs) {
412 orc_warn("missing regs for base reg R13 at ip %pB\n",
413 (void *)state->ip);
414 goto done;
415 }
416 sp = state->regs->r13;
417 break;
418
419 case ORC_REG_DI:
420 if (!state->regs || !state->full_regs) {
421 orc_warn("missing regs for base reg DI at ip %pB\n",
422 (void *)state->ip);
423 goto done;
424 }
425 sp = state->regs->di;
426 break;
427
428 case ORC_REG_DX:
429 if (!state->regs || !state->full_regs) {
430 orc_warn("missing regs for base reg DX at ip %pB\n",
431 (void *)state->ip);
432 goto done;
433 }
434 sp = state->regs->dx;
435 break;
436
437 default:
438 orc_warn("unknown SP base reg %d for ip %pB\n",
439 orc->sp_reg, (void *)state->ip);
440 goto done;
441 }
442
443 if (indirect) {
444 if (!deref_stack_reg(state, sp, &sp))
445 goto done;
446 }
447
448 /* Find IP, SP and possibly regs: */
449 switch (orc->type) {
450 case ORC_TYPE_CALL:
451 ip_p = sp - sizeof(long);
452
453 if (!deref_stack_reg(state, ip_p, &state->ip))
454 goto done;
455
456 state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
457 state->ip, (void *)ip_p);
458
459 state->sp = sp;
460 state->regs = NULL;
461 state->signal = false;
462 break;
463
464 case ORC_TYPE_REGS:
465 if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
466 orc_warn("can't dereference registers at %p for ip %pB\n",
467 (void *)sp, (void *)orig_ip);
468 goto done;
469 }
470
471 state->regs = (struct pt_regs *)sp;
472 state->full_regs = true;
473 state->signal = true;
474 break;
475
476 case ORC_TYPE_REGS_IRET:
477 if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
478 orc_warn("can't dereference iret registers at %p for ip %pB\n",
479 (void *)sp, (void *)orig_ip);
480 goto done;
481 }
482
483 state->regs = (void *)sp - IRET_FRAME_OFFSET;
484 state->full_regs = false;
485 state->signal = true;
486 break;
487
488 default:
489 orc_warn("unknown .orc_unwind entry type %d for ip %pB\n",
490 orc->type, (void *)orig_ip);
491 break;
492 }
493
494 /* Find BP: */
495 switch (orc->bp_reg) {
496 case ORC_REG_UNDEFINED:
497 if (state->regs && state->full_regs)
498 state->bp = state->regs->bp;
499 break;
500
501 case ORC_REG_PREV_SP:
502 if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
503 goto done;
504 break;
505
506 case ORC_REG_BP:
507 if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
508 goto done;
509 break;
510
511 default:
512 orc_warn("unknown BP base reg %d for ip %pB\n",
513 orc->bp_reg, (void *)orig_ip);
514 goto done;
515 }
516
517 /* Prevent a recursive loop due to bad ORC data: */
518 if (state->stack_info.type == prev_type &&
519 on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
520 state->sp <= prev_sp) {
521 orc_warn("stack going in the wrong direction? ip=%pB\n",
522 (void *)orig_ip);
523 goto done;
524 }
525
526 preempt_enable();
527 return true;
528
529done:
530 preempt_enable();
531 state->stack_info.type = STACK_TYPE_UNKNOWN;
532 return false;
533}
534EXPORT_SYMBOL_GPL(unwind_next_frame);
535
536void __unwind_start(struct unwind_state *state, struct task_struct *task,
537 struct pt_regs *regs, unsigned long *first_frame)
538{
539 memset(state, 0, sizeof(*state));
540 state->task = task;
541
542 /*
543 * Refuse to unwind the stack of a task while it's executing on another
544 * CPU. This check is racy, but that's ok: the unwinder has other
545 * checks to prevent it from going off the rails.
546 */
547 if (task_on_another_cpu(task))
548 goto done;
549
550 if (regs) {
551 if (user_mode(regs))
552 goto done;
553
554 state->ip = regs->ip;
555 state->sp = kernel_stack_pointer(regs);
556 state->bp = regs->bp;
557 state->regs = regs;
558 state->full_regs = true;
559 state->signal = true;
560
561 } else if (task == current) {
562 asm volatile("lea (%%rip), %0\n\t"
563 "mov %%rsp, %1\n\t"
564 "mov %%rbp, %2\n\t"
565 : "=r" (state->ip), "=r" (state->sp),
566 "=r" (state->bp));
567
568 } else {
569 struct inactive_task_frame *frame = (void *)task->thread.sp;
570
571 state->sp = task->thread.sp;
572 state->bp = READ_ONCE_NOCHECK(frame->bp);
573 state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
574 }
575
576 if (get_stack_info((unsigned long *)state->sp, state->task,
577 &state->stack_info, &state->stack_mask)) {
578 /*
579 * We weren't on a valid stack. It's possible that
580 * we overflowed a valid stack into a guard page.
581 * See if the next page up is valid so that we can
582 * generate some kind of backtrace if this happens.
583 */
584 void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
585 if (get_stack_info(next_page, state->task, &state->stack_info,
586 &state->stack_mask))
587 return;
588 }
589
590 /*
591 * The caller can provide the address of the first frame directly
592 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
593 * to start unwinding at. Skip ahead until we reach it.
594 */
595
596 /* When starting from regs, skip the regs frame: */
597 if (regs) {
598 unwind_next_frame(state);
599 return;
600 }
601
602 /* Otherwise, skip ahead to the user-specified starting frame: */
603 while (!unwind_done(state) &&
604 (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
605 state->sp <= (unsigned long)first_frame))
606 unwind_next_frame(state);
607
608 return;
609
610done:
611 state->stack_info.type = STACK_TYPE_UNKNOWN;
612 return;
613}
614EXPORT_SYMBOL_GPL(__unwind_start);