1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
4 *
5 * Lots of this code have been borrowed or heavily inspired from parts of
6 * the libunwind 0.99 code which are (amongst other contributors I may have
7 * forgotten):
8 *
9 * Copyright (C) 2002-2007 Hewlett-Packard Co
10 * Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
11 *
12 * And the bugs have been added by:
13 *
14 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
15 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
16 *
17 */
18
19 #include <elf.h>
20 #include <errno.h>
21 #include <gelf.h>
22 #include <fcntl.h>
23 #include <inttypes.h>
24 #include <string.h>
25 #include <unistd.h>
26 #include <sys/mman.h>
27 #include <linux/list.h>
28 #include <linux/zalloc.h>
29 #ifndef REMOTE_UNWIND_LIBUNWIND
30 #include <libunwind.h>
31 #include <libunwind-ptrace.h>
32 #endif
33 #include "callchain.h"
34 #include "thread.h"
35 #include "session.h"
36 #include "perf_regs.h"
37 #include "unwind.h"
38 #include "map.h"
39 #include "symbol.h"
40 #include "debug.h"
41 #include "asm/bug.h"
42 #include "dso.h"
43
44 extern int
45 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
46 unw_word_t ip,
47 unw_dyn_info_t *di,
48 unw_proc_info_t *pi,
49 int need_unwind_info, void *arg);
50
51 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
52
53 extern int
54 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
55 unw_word_t ip,
56 unw_word_t segbase,
57 const char *obj_name, unw_word_t start,
58 unw_word_t end);
59
60 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
61
62 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
63 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
64
65 /* Pointer-encoding formats: */
66 #define DW_EH_PE_omit 0xff
67 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
68 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
69 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
70 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
71 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
72
73 /* Pointer-encoding application: */
74 #define DW_EH_PE_absptr 0x00 /* absolute value */
75 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
76
77 /*
78 * The following are not documented by LSB v1.3, yet they are used by
79 * GCC, presumably they aren't documented by LSB since they aren't
80 * used on Linux:
81 */
82 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
83 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
84
85 /* Flags intentionally not handled, since they're not needed:
86 * #define DW_EH_PE_indirect 0x80
87 * #define DW_EH_PE_uleb128 0x01
88 * #define DW_EH_PE_udata2 0x02
89 * #define DW_EH_PE_sleb128 0x09
90 * #define DW_EH_PE_sdata2 0x0a
91 * #define DW_EH_PE_textrel 0x20
92 * #define DW_EH_PE_datarel 0x30
93 */
94
95 struct unwind_info {
96 struct perf_sample *sample;
97 struct machine *machine;
98 struct thread *thread;
99 bool best_effort;
100 };
101
102 #define dw_read(ptr, type, end) ({ \
103 type *__p = (type *) ptr; \
104 type __v; \
105 if ((__p + 1) > (type *) end) \
106 return -EINVAL; \
107 __v = *__p++; \
108 ptr = (typeof(ptr)) __p; \
109 __v; \
110 })
111
112 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
113 u8 encoding)
114 {
115 u8 *cur = *p;
116 *val = 0;
117
118 switch (encoding) {
119 case DW_EH_PE_omit:
120 *val = 0;
121 goto out;
122 case DW_EH_PE_ptr:
123 *val = dw_read(cur, unsigned long, end);
124 goto out;
125 default:
126 break;
127 }
128
129 switch (encoding & DW_EH_PE_APPL_MASK) {
130 case DW_EH_PE_absptr:
131 break;
132 case DW_EH_PE_pcrel:
133 *val = (unsigned long) cur;
134 break;
135 default:
136 return -EINVAL;
137 }
138
139 if ((encoding & 0x07) == 0x00)
140 encoding |= DW_EH_PE_udata4;
141
142 switch (encoding & DW_EH_PE_FORMAT_MASK) {
143 case DW_EH_PE_sdata4:
144 *val += dw_read(cur, s32, end);
145 break;
146 case DW_EH_PE_udata4:
147 *val += dw_read(cur, u32, end);
148 break;
149 case DW_EH_PE_sdata8:
150 *val += dw_read(cur, s64, end);
151 break;
152 case DW_EH_PE_udata8:
153 *val += dw_read(cur, u64, end);
154 break;
155 default:
156 return -EINVAL;
157 }
158
159 out:
160 *p = cur;
161 return 0;
162 }
163
164 #define dw_read_encoded_value(ptr, end, enc) ({ \
165 u64 __v; \
166 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
167 return -EINVAL; \
168 } \
169 __v; \
170 })
171
172 static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
173 {
174 Elf *elf;
175 GElf_Ehdr ehdr;
176 GElf_Shdr shdr;
177 int ret = -1;
178
179 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
180 if (elf == NULL)
181 return -1;
182
183 if (gelf_getehdr(elf, &ehdr) == NULL)
184 goto out_err;
185
186 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
187 goto out_err;
188
189 *address = shdr.sh_addr;
190 *offset = shdr.sh_offset;
191 ret = 0;
192 out_err:
193 elf_end(elf);
194 return ret;
195 }
196
197 #ifndef NO_LIBUNWIND_DEBUG_FRAME
198 static u64 elf_section_offset(int fd, const char *name)
199 {
200 u64 address, offset = 0;
201
202 if (elf_section_address_and_offset(fd, name, &address, &offset))
203 return 0;
204
205 return offset;
206 }
207 #endif
208
209 static u64 elf_base_address(int fd)
210 {
211 Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
212 GElf_Phdr phdr;
213 u64 retval = 0;
214 size_t i, phdrnum = 0;
215
216 if (elf == NULL)
217 return 0;
218 (void)elf_getphdrnum(elf, &phdrnum);
219 /* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */
220 for (i = 0; i < phdrnum; i++) {
221 if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) {
222 retval = phdr.p_vaddr & -getpagesize();
223 break;
224 }
225 }
226
227 elf_end(elf);
228 return retval;
229 }
230
231 #ifndef NO_LIBUNWIND_DEBUG_FRAME
232 static int elf_is_exec(int fd, const char *name)
233 {
234 Elf *elf;
235 GElf_Ehdr ehdr;
236 int retval = 0;
237
238 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
239 if (elf == NULL)
240 return 0;
241 if (gelf_getehdr(elf, &ehdr) == NULL)
242 goto out;
243
244 retval = (ehdr.e_type == ET_EXEC);
245
246 out:
247 elf_end(elf);
248 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
249 return retval;
250 }
251 #endif
252
253 struct table_entry {
254 u32 start_ip_offset;
255 u32 fde_offset;
256 };
257
258 struct eh_frame_hdr {
259 unsigned char version;
260 unsigned char eh_frame_ptr_enc;
261 unsigned char fde_count_enc;
262 unsigned char table_enc;
263
264 /*
265 * The rest of the header is variable-length and consists of the
266 * following members:
267 *
268 * encoded_t eh_frame_ptr;
269 * encoded_t fde_count;
270 */
271
272 /* A single encoded pointer should not be more than 8 bytes. */
273 u64 enc[2];
274
275 /*
276 * struct {
277 * encoded_t start_ip;
278 * encoded_t fde_addr;
279 * } binary_search_table[fde_count];
280 */
281 char data[];
282 } __packed;
283
284 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
285 u64 offset, u64 *table_data_offset, u64 *fde_count)
286 {
287 struct eh_frame_hdr hdr;
288 u8 *enc = (u8 *) &hdr.enc;
289 u8 *end = (u8 *) &hdr.data;
290 ssize_t r;
291
292 r = dso__data_read_offset(dso, machine, offset,
293 (u8 *) &hdr, sizeof(hdr));
294 if (r != sizeof(hdr))
295 return -EINVAL;
296
297 /* We dont need eh_frame_ptr, just skip it. */
298 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
299
300 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
301 *table_data_offset = enc - (u8 *) &hdr;
302 return 0;
303 }
304
305 struct read_unwind_spec_eh_frame_maps_cb_args {
306 struct dso *dso;
307 u64 base_addr;
308 };
309
310 static int read_unwind_spec_eh_frame_maps_cb(struct map *map, void *data)
311 {
312
313 struct read_unwind_spec_eh_frame_maps_cb_args *args = data;
314
315 if (map__dso(map) == args->dso && map__start(map) - map__pgoff(map) < args->base_addr)
316 args->base_addr = map__start(map) - map__pgoff(map);
317
318 return 0;
319 }
320
321
322 static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
323 u64 *table_data, u64 *segbase,
324 u64 *fde_count)
325 {
326 struct read_unwind_spec_eh_frame_maps_cb_args args = {
327 .dso = dso,
328 .base_addr = UINT64_MAX,
329 };
330 int ret, fd;
331
332 if (dso__data(dso)->eh_frame_hdr_offset == 0) {
333 fd = dso__data_get_fd(dso, ui->machine);
334 if (fd < 0)
335 return -EINVAL;
336
337 /* Check the .eh_frame section for unwinding info */
338 ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
339 &dso__data(dso)->eh_frame_hdr_addr,
340 &dso__data(dso)->eh_frame_hdr_offset);
341 dso__data(dso)->elf_base_addr = elf_base_address(fd);
342 dso__data_put_fd(dso);
343 if (ret || dso__data(dso)->eh_frame_hdr_offset == 0)
344 return -EINVAL;
345 }
346
347 maps__for_each_map(thread__maps(ui->thread), read_unwind_spec_eh_frame_maps_cb, &args);
348
349 args.base_addr -= dso__data(dso)->elf_base_addr;
350 /* Address of .eh_frame_hdr */
351 *segbase = args.base_addr + dso__data(dso)->eh_frame_hdr_addr;
352 ret = unwind_spec_ehframe(dso, ui->machine, dso__data(dso)->eh_frame_hdr_offset,
353 table_data, fde_count);
354 if (ret)
355 return ret;
356 /* binary_search_table offset plus .eh_frame_hdr address */
357 *table_data += *segbase;
358 return 0;
359 }
360
361 #ifndef NO_LIBUNWIND_DEBUG_FRAME
362 static int read_unwind_spec_debug_frame(struct dso *dso,
363 struct machine *machine, u64 *offset)
364 {
365 int fd;
366 u64 ofs = dso__data(dso)->debug_frame_offset;
367
368 /* debug_frame can reside in:
369 * - dso
370 * - debug pointed by symsrc_filename
371 * - gnu_debuglink, which doesn't necessary
372 * has to be pointed by symsrc_filename
373 */
374 if (ofs == 0) {
375 fd = dso__data_get_fd(dso, machine);
376 if (fd >= 0) {
377 ofs = elf_section_offset(fd, ".debug_frame");
378 dso__data_put_fd(dso);
379 }
380
381 if (ofs <= 0) {
382 fd = open(dso__symsrc_filename(dso), O_RDONLY);
383 if (fd >= 0) {
384 ofs = elf_section_offset(fd, ".debug_frame");
385 close(fd);
386 }
387 }
388
389 if (ofs <= 0) {
390 char *debuglink = malloc(PATH_MAX);
391 int ret = 0;
392
393 if (debuglink == NULL) {
394 pr_err("unwind: Can't read unwind spec debug frame.\n");
395 return -ENOMEM;
396 }
397
398 ret = dso__read_binary_type_filename(
399 dso, DSO_BINARY_TYPE__DEBUGLINK,
400 machine->root_dir, debuglink, PATH_MAX);
401 if (!ret) {
402 fd = open(debuglink, O_RDONLY);
403 if (fd >= 0) {
404 ofs = elf_section_offset(fd,
405 ".debug_frame");
406 close(fd);
407 }
408 }
409 if (ofs > 0) {
410 if (dso__symsrc_filename(dso) != NULL) {
411 pr_warning(
412 "%s: overwrite symsrc(%s,%s)\n",
413 __func__,
414 dso__symsrc_filename(dso),
415 debuglink);
416 dso__free_symsrc_filename(dso);
417 }
418 dso__set_symsrc_filename(dso, debuglink);
419 } else {
420 free(debuglink);
421 }
422 }
423
424 dso__data(dso)->debug_frame_offset = ofs;
425 }
426
427 *offset = ofs;
428 if (*offset)
429 return 0;
430
431 return -EINVAL;
432 }
433 #endif
434
435 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
436 {
437 struct addr_location al;
438 struct map *ret;
439
440 addr_location__init(&al);
441 thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
442 ret = map__get(al.map);
443 addr_location__exit(&al);
444 return ret;
445 }
446
447 static int
448 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
449 int need_unwind_info, void *arg)
450 {
451 struct unwind_info *ui = arg;
452 struct map *map;
453 struct dso *dso;
454 unw_dyn_info_t di;
455 u64 table_data, segbase, fde_count;
456 int ret = -EINVAL;
457
458 map = find_map(ip, ui);
459 if (!map)
460 return -EINVAL;
461
462 dso = map__dso(map);
463 if (!dso) {
464 map__put(map);
465 return -EINVAL;
466 }
467
468 pr_debug("unwind: find_proc_info dso %s\n", dso__name(dso));
469
470 /* Check the .eh_frame section for unwinding info */
471 if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) {
472 memset(&di, 0, sizeof(di));
473 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
474 di.start_ip = map__start(map);
475 di.end_ip = map__end(map);
476 di.u.rti.segbase = segbase;
477 di.u.rti.table_data = table_data;
478 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
479 / sizeof(unw_word_t);
480 ret = dwarf_search_unwind_table(as, ip, &di, pi,
481 need_unwind_info, arg);
482 }
483
484 #ifndef NO_LIBUNWIND_DEBUG_FRAME
485 /* Check the .debug_frame section for unwinding info */
486 if (ret < 0 &&
487 !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) {
488 int fd = dso__data_get_fd(dso, ui->machine);
489 int is_exec = elf_is_exec(fd, dso__name(dso));
490 u64 start = map__start(map);
491 unw_word_t base = is_exec ? 0 : start;
492 const char *symfile;
493
494 if (fd >= 0)
495 dso__data_put_fd(dso);
496
497 symfile = dso__symsrc_filename(dso) ?: dso__name(dso);
498
499 memset(&di, 0, sizeof(di));
500 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
501 ret = dwarf_search_unwind_table(as, ip, &di, pi,
502 need_unwind_info, arg);
503 }
504 #endif
505 map__put(map);
506 return ret;
507 }
508
509 static int access_fpreg(unw_addr_space_t __maybe_unused as,
510 unw_regnum_t __maybe_unused num,
511 unw_fpreg_t __maybe_unused *val,
512 int __maybe_unused __write,
513 void __maybe_unused *arg)
514 {
515 pr_err("unwind: access_fpreg unsupported\n");
516 return -UNW_EINVAL;
517 }
518
519 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
520 unw_word_t __maybe_unused *dil_addr,
521 void __maybe_unused *arg)
522 {
523 return -UNW_ENOINFO;
524 }
525
526 static int resume(unw_addr_space_t __maybe_unused as,
527 unw_cursor_t __maybe_unused *cu,
528 void __maybe_unused *arg)
529 {
530 pr_err("unwind: resume unsupported\n");
531 return -UNW_EINVAL;
532 }
533
534 static int
535 get_proc_name(unw_addr_space_t __maybe_unused as,
536 unw_word_t __maybe_unused addr,
537 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
538 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
539 {
540 pr_err("unwind: get_proc_name unsupported\n");
541 return -UNW_EINVAL;
542 }
543
544 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
545 unw_word_t *data)
546 {
547 struct map *map;
548 struct dso *dso;
549 ssize_t size;
550
551 map = find_map(addr, ui);
552 if (!map) {
553 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
554 return -1;
555 }
556
557 dso = map__dso(map);
558
559 if (!dso) {
560 map__put(map);
561 return -1;
562 }
563
564 size = dso__data_read_addr(dso, map, ui->machine,
565 addr, (u8 *) data, sizeof(*data));
566 map__put(map);
567 return !(size == sizeof(*data));
568 }
569
570 static int access_mem(unw_addr_space_t __maybe_unused as,
571 unw_word_t addr, unw_word_t *valp,
572 int __write, void *arg)
573 {
574 struct unwind_info *ui = arg;
575 const char *arch = perf_env__arch(ui->machine->env);
576 struct stack_dump *stack = &ui->sample->user_stack;
577 u64 start, end;
578 int offset;
579 int ret;
580
581 /* Don't support write, probably not needed. */
582 if (__write || !stack || !ui->sample->user_regs.regs) {
583 *valp = 0;
584 return 0;
585 }
586
587 ret = perf_reg_value(&start, &ui->sample->user_regs,
588 perf_arch_reg_sp(arch));
589 if (ret)
590 return ret;
591
592 end = start + stack->size;
593
594 /* Check overflow. */
595 if (addr + sizeof(unw_word_t) < addr)
596 return -EINVAL;
597
598 if (addr < start || addr + sizeof(unw_word_t) >= end) {
599 ret = access_dso_mem(ui, addr, valp);
600 if (ret) {
601 pr_debug("unwind: access_mem %p not inside range"
602 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
603 (void *) (uintptr_t) addr, start, end);
604 *valp = 0;
605 return ret;
606 }
607 return 0;
608 }
609
610 offset = addr - start;
611 *valp = *(unw_word_t *)&stack->data[offset];
612 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
613 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
614 return 0;
615 }
616
617 static int access_reg(unw_addr_space_t __maybe_unused as,
618 unw_regnum_t regnum, unw_word_t *valp,
619 int __write, void *arg)
620 {
621 struct unwind_info *ui = arg;
622 int id, ret;
623 u64 val;
624
625 /* Don't support write, I suspect we don't need it. */
626 if (__write) {
627 pr_err("unwind: access_reg w %d\n", regnum);
628 return 0;
629 }
630
631 if (!ui->sample->user_regs.regs) {
632 *valp = 0;
633 return 0;
634 }
635
636 id = LIBUNWIND__ARCH_REG_ID(regnum);
637 if (id < 0)
638 return -EINVAL;
639
640 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
641 if (ret) {
642 if (!ui->best_effort)
643 pr_err("unwind: can't read reg %d\n", regnum);
644 return ret;
645 }
646
647 *valp = (unw_word_t) val;
648 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
649 return 0;
650 }
651
652 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
653 unw_proc_info_t *pi __maybe_unused,
654 void *arg __maybe_unused)
655 {
656 pr_debug("unwind: put_unwind_info called\n");
657 }
658
659 static int entry(u64 ip, struct thread *thread,
660 unwind_entry_cb_t cb, void *arg)
661 {
662 struct unwind_entry e;
663 struct addr_location al;
664 int ret;
665
666 addr_location__init(&al);
667 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
668 e.ip = ip;
669 e.ms.map = al.map;
670 e.ms.maps = al.maps;
671
672 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
673 al.sym ? al.sym->name : "''",
674 ip,
675 al.map ? map__map_ip(al.map, ip) : (u64) 0);
676
677 ret = cb(&e, arg);
678 addr_location__exit(&al);
679 return ret;
680 }
681
682 static void display_error(int err)
683 {
684 switch (err) {
685 case UNW_EINVAL:
686 pr_err("unwind: Only supports local.\n");
687 break;
688 case UNW_EUNSPEC:
689 pr_err("unwind: Unspecified error.\n");
690 break;
691 case UNW_EBADREG:
692 pr_err("unwind: Register unavailable.\n");
693 break;
694 default:
695 break;
696 }
697 }
698
699 static unw_accessors_t accessors = {
700 .find_proc_info = find_proc_info,
701 .put_unwind_info = put_unwind_info,
702 .get_dyn_info_list_addr = get_dyn_info_list_addr,
703 .access_mem = access_mem,
704 .access_reg = access_reg,
705 .access_fpreg = access_fpreg,
706 .resume = resume,
707 .get_proc_name = get_proc_name,
708 };
709
710 static int _unwind__prepare_access(struct maps *maps)
711 {
712 void *addr_space = unw_create_addr_space(&accessors, 0);
713
714 maps__set_addr_space(maps, addr_space);
715 if (!addr_space) {
716 pr_err("unwind: Can't create unwind address space.\n");
717 return -ENOMEM;
718 }
719
720 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
721 return 0;
722 }
723
724 static void _unwind__flush_access(struct maps *maps)
725 {
726 unw_flush_cache(maps__addr_space(maps), 0, 0);
727 }
728
729 static void _unwind__finish_access(struct maps *maps)
730 {
731 unw_destroy_addr_space(maps__addr_space(maps));
732 }
733
734 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
735 void *arg, int max_stack)
736 {
737 const char *arch = perf_env__arch(ui->machine->env);
738 u64 val;
739 unw_word_t ips[max_stack];
740 unw_addr_space_t addr_space;
741 unw_cursor_t c;
742 int ret, i = 0;
743
744 ret = perf_reg_value(&val, &ui->sample->user_regs,
745 perf_arch_reg_ip(arch));
746 if (ret)
747 return ret;
748
749 ips[i++] = (unw_word_t) val;
750
751 /*
752 * If we need more than one entry, do the DWARF
753 * unwind itself.
754 */
755 if (max_stack - 1 > 0) {
756 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
757 addr_space = maps__addr_space(thread__maps(ui->thread));
758
759 if (addr_space == NULL)
760 return -1;
761
762 ret = unw_init_remote(&c, addr_space, ui);
763 if (ret && !ui->best_effort)
764 display_error(ret);
765
766 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
767 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
768
769 /*
770 * Decrement the IP for any non-activation frames.
771 * this is required to properly find the srcline
772 * for caller frames.
773 * See also the documentation for dwfl_frame_pc(),
774 * which this code tries to replicate.
775 */
776 if (unw_is_signal_frame(&c) <= 0)
777 --ips[i];
778
779 ++i;
780 }
781
782 max_stack = i;
783 }
784
785 /*
786 * Display what we got based on the order setup.
787 */
788 for (i = 0; i < max_stack && !ret; i++) {
789 int j = i;
790
791 if (callchain_param.order == ORDER_CALLER)
792 j = max_stack - i - 1;
793 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
794 }
795
796 return ret;
797 }
798
799 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
800 struct thread *thread,
801 struct perf_sample *data, int max_stack,
802 bool best_effort)
803 {
804 struct unwind_info ui = {
805 .sample = data,
806 .thread = thread,
807 .machine = maps__machine(thread__maps(thread)),
808 .best_effort = best_effort
809 };
810
811 if (!data->user_regs.regs)
812 return -EINVAL;
813
814 if (max_stack <= 0)
815 return -EINVAL;
816
817 return get_entries(&ui, cb, arg, max_stack);
818 }
819
820 static struct unwind_libunwind_ops
821 _unwind_libunwind_ops = {
822 .prepare_access = _unwind__prepare_access,
823 .flush_access = _unwind__flush_access,
824 .finish_access = _unwind__finish_access,
825 .get_entries = _unwind__get_entries,
826 };
827
828 #ifndef REMOTE_UNWIND_LIBUNWIND
829 struct unwind_libunwind_ops *
830 local_unwind_libunwind_ops = &_unwind_libunwind_ops;
831 #endif
832
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