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
44extern int
45UNW_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
53extern int
54UNW_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
95struct 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
112static 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
172static 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;
192out_err:
193 elf_end(elf);
194 return ret;
195}
196
197#ifndef NO_LIBUNWIND_DEBUG_FRAME
198static 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: &address, offset: &offset))
203 return 0;
204
205 return offset;
206}
207#endif
208
209static 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
232static 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
246out:
247 elf_end(elf);
248 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
249 return retval;
250}
251#endif
252
253struct table_entry {
254 u32 start_ip_offset;
255 u32 fde_offset;
256};
257
258struct 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
284static 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 data: (u8 *) &hdr, size: 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
305static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
306 u64 *table_data, u64 *segbase,
307 u64 *fde_count)
308{
309 struct map_rb_node *map_node;
310 u64 base_addr = UINT64_MAX;
311 int ret, fd;
312
313 if (dso->data.eh_frame_hdr_offset == 0) {
314 fd = dso__data_get_fd(dso, machine: ui->machine);
315 if (fd < 0)
316 return -EINVAL;
317
318 /* Check the .eh_frame section for unwinding info */
319 ret = elf_section_address_and_offset(fd, name: ".eh_frame_hdr",
320 address: &dso->data.eh_frame_hdr_addr,
321 offset: &dso->data.eh_frame_hdr_offset);
322 dso->data.elf_base_addr = elf_base_address(fd);
323 dso__data_put_fd(dso);
324 if (ret || dso->data.eh_frame_hdr_offset == 0)
325 return -EINVAL;
326 }
327
328 maps__for_each_entry(thread__maps(ui->thread), map_node) {
329 struct map *map = map_node->map;
330 u64 start = map__start(map);
331
332 if (map__dso(map) == dso && start < base_addr)
333 base_addr = start;
334 }
335 base_addr -= dso->data.elf_base_addr;
336 /* Address of .eh_frame_hdr */
337 *segbase = base_addr + dso->data.eh_frame_hdr_addr;
338 ret = unwind_spec_ehframe(dso, machine: ui->machine, offset: dso->data.eh_frame_hdr_offset,
339 table_data_offset: table_data, fde_count);
340 if (ret)
341 return ret;
342 /* binary_search_table offset plus .eh_frame_hdr address */
343 *table_data += *segbase;
344 return 0;
345}
346
347#ifndef NO_LIBUNWIND_DEBUG_FRAME
348static int read_unwind_spec_debug_frame(struct dso *dso,
349 struct machine *machine, u64 *offset)
350{
351 int fd;
352 u64 ofs = dso->data.debug_frame_offset;
353
354 /* debug_frame can reside in:
355 * - dso
356 * - debug pointed by symsrc_filename
357 * - gnu_debuglink, which doesn't necessary
358 * has to be pointed by symsrc_filename
359 */
360 if (ofs == 0) {
361 fd = dso__data_get_fd(dso, machine);
362 if (fd >= 0) {
363 ofs = elf_section_offset(fd, name: ".debug_frame");
364 dso__data_put_fd(dso);
365 }
366
367 if (ofs <= 0) {
368 fd = open(dso->symsrc_filename, O_RDONLY);
369 if (fd >= 0) {
370 ofs = elf_section_offset(fd, name: ".debug_frame");
371 close(fd);
372 }
373 }
374
375 if (ofs <= 0) {
376 char *debuglink = malloc(PATH_MAX);
377 int ret = 0;
378
379 ret = dso__read_binary_type_filename(
380 dso, type: DSO_BINARY_TYPE__DEBUGLINK,
381 root_dir: machine->root_dir, filename: debuglink, PATH_MAX);
382 if (!ret) {
383 fd = open(debuglink, O_RDONLY);
384 if (fd >= 0) {
385 ofs = elf_section_offset(fd,
386 name: ".debug_frame");
387 close(fd);
388 }
389 }
390 if (ofs > 0) {
391 if (dso->symsrc_filename != NULL) {
392 pr_warning(
393 "%s: overwrite symsrc(%s,%s)\n",
394 __func__,
395 dso->symsrc_filename,
396 debuglink);
397 zfree(&dso->symsrc_filename);
398 }
399 dso->symsrc_filename = debuglink;
400 } else {
401 free(debuglink);
402 }
403 }
404
405 dso->data.debug_frame_offset = ofs;
406 }
407
408 *offset = ofs;
409 if (*offset)
410 return 0;
411
412 return -EINVAL;
413}
414#endif
415
416static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
417{
418 struct addr_location al;
419 struct map *ret;
420
421 addr_location__init(al: &al);
422 thread__find_map(thread: ui->thread, PERF_RECORD_MISC_USER, addr: ip, al: &al);
423 ret = map__get(map: al.map);
424 addr_location__exit(al: &al);
425 return ret;
426}
427
428static int
429find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
430 int need_unwind_info, void *arg)
431{
432 struct unwind_info *ui = arg;
433 struct map *map;
434 struct dso *dso;
435 unw_dyn_info_t di;
436 u64 table_data, segbase, fde_count;
437 int ret = -EINVAL;
438
439 map = find_map(ip, ui);
440 if (!map)
441 return -EINVAL;
442
443 dso = map__dso(map);
444 if (!dso) {
445 map__put(map);
446 return -EINVAL;
447 }
448
449 pr_debug("unwind: find_proc_info dso %s\n", dso->name);
450
451 /* Check the .eh_frame section for unwinding info */
452 if (!read_unwind_spec_eh_frame(dso, ui, table_data: &table_data, segbase: &segbase, fde_count: &fde_count)) {
453 memset(&di, 0, sizeof(di));
454 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
455 di.start_ip = map__start(map);
456 di.end_ip = map__end(map);
457 di.u.rti.segbase = segbase;
458 di.u.rti.table_data = table_data;
459 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
460 / sizeof(unw_word_t);
461 ret = dwarf_search_unwind_table(as, ip, &di, pi,
462 need_unwind_info, arg);
463 }
464
465#ifndef NO_LIBUNWIND_DEBUG_FRAME
466 /* Check the .debug_frame section for unwinding info */
467 if (ret < 0 &&
468 !read_unwind_spec_debug_frame(dso, machine: ui->machine, offset: &segbase)) {
469 int fd = dso__data_get_fd(dso, machine: ui->machine);
470 int is_exec = elf_is_exec(fd, name: dso->name);
471 u64 start = map__start(map);
472 unw_word_t base = is_exec ? 0 : start;
473 const char *symfile;
474
475 if (fd >= 0)
476 dso__data_put_fd(dso);
477
478 symfile = dso->symsrc_filename ?: dso->name;
479
480 memset(&di, 0, sizeof(di));
481 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
482 ret = dwarf_search_unwind_table(as, ip, &di, pi,
483 need_unwind_info, arg);
484 }
485#endif
486 map__put(map);
487 return ret;
488}
489
490static int access_fpreg(unw_addr_space_t __maybe_unused as,
491 unw_regnum_t __maybe_unused num,
492 unw_fpreg_t __maybe_unused *val,
493 int __maybe_unused __write,
494 void __maybe_unused *arg)
495{
496 pr_err("unwind: access_fpreg unsupported\n");
497 return -UNW_EINVAL;
498}
499
500static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
501 unw_word_t __maybe_unused *dil_addr,
502 void __maybe_unused *arg)
503{
504 return -UNW_ENOINFO;
505}
506
507static int resume(unw_addr_space_t __maybe_unused as,
508 unw_cursor_t __maybe_unused *cu,
509 void __maybe_unused *arg)
510{
511 pr_err("unwind: resume unsupported\n");
512 return -UNW_EINVAL;
513}
514
515static int
516get_proc_name(unw_addr_space_t __maybe_unused as,
517 unw_word_t __maybe_unused addr,
518 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
519 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
520{
521 pr_err("unwind: get_proc_name unsupported\n");
522 return -UNW_EINVAL;
523}
524
525static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
526 unw_word_t *data)
527{
528 struct map *map;
529 struct dso *dso;
530 ssize_t size;
531
532 map = find_map(addr, ui);
533 if (!map) {
534 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
535 return -1;
536 }
537
538 dso = map__dso(map);
539
540 if (!dso) {
541 map__put(map);
542 return -1;
543 }
544
545 size = dso__data_read_addr(dso, map, machine: ui->machine,
546 addr: addr, data: (u8 *) data, size: sizeof(*data));
547 map__put(map);
548 return !(size == sizeof(*data));
549}
550
551static int access_mem(unw_addr_space_t __maybe_unused as,
552 unw_word_t addr, unw_word_t *valp,
553 int __write, void *arg)
554{
555 struct unwind_info *ui = arg;
556 const char *arch = perf_env__arch(env: ui->machine->env);
557 struct stack_dump *stack = &ui->sample->user_stack;
558 u64 start, end;
559 int offset;
560 int ret;
561
562 /* Don't support write, probably not needed. */
563 if (__write || !stack || !ui->sample->user_regs.regs) {
564 *valp = 0;
565 return 0;
566 }
567
568 ret = perf_reg_value(regs: &start, idx: &ui->sample->user_regs,
569 perf_arch_reg_sp(arch));
570 if (ret)
571 return ret;
572
573 end = start + stack->size;
574
575 /* Check overflow. */
576 if (addr + sizeof(unw_word_t) < addr)
577 return -EINVAL;
578
579 if (addr < start || addr + sizeof(unw_word_t) >= end) {
580 ret = access_dso_mem(ui, addr, valp);
581 if (ret) {
582 pr_debug("unwind: access_mem %p not inside range"
583 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
584 (void *) (uintptr_t) addr, start, end);
585 *valp = 0;
586 return ret;
587 }
588 return 0;
589 }
590
591 offset = addr - start;
592 *valp = *(unw_word_t *)&stack->data[offset];
593 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
594 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
595 return 0;
596}
597
598static int access_reg(unw_addr_space_t __maybe_unused as,
599 unw_regnum_t regnum, unw_word_t *valp,
600 int __write, void *arg)
601{
602 struct unwind_info *ui = arg;
603 int id, ret;
604 u64 val;
605
606 /* Don't support write, I suspect we don't need it. */
607 if (__write) {
608 pr_err("unwind: access_reg w %d\n", regnum);
609 return 0;
610 }
611
612 if (!ui->sample->user_regs.regs) {
613 *valp = 0;
614 return 0;
615 }
616
617 id = LIBUNWIND__ARCH_REG_ID(regnum);
618 if (id < 0)
619 return -EINVAL;
620
621 ret = perf_reg_value(regs: &val, idx: &ui->sample->user_regs, id);
622 if (ret) {
623 if (!ui->best_effort)
624 pr_err("unwind: can't read reg %d\n", regnum);
625 return ret;
626 }
627
628 *valp = (unw_word_t) val;
629 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
630 return 0;
631}
632
633static void put_unwind_info(unw_addr_space_t __maybe_unused as,
634 unw_proc_info_t *pi __maybe_unused,
635 void *arg __maybe_unused)
636{
637 pr_debug("unwind: put_unwind_info called\n");
638}
639
640static int entry(u64 ip, struct thread *thread,
641 unwind_entry_cb_t cb, void *arg)
642{
643 struct unwind_entry e;
644 struct addr_location al;
645 int ret;
646
647 addr_location__init(al: &al);
648 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, addr: ip, al: &al);
649 e.ip = ip;
650 e.ms.map = al.map;
651 e.ms.maps = al.maps;
652
653 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
654 al.sym ? al.sym->name : "''",
655 ip,
656 al.map ? map__map_ip(al.map, ip) : (u64) 0);
657
658 ret = cb(&e, arg);
659 addr_location__exit(al: &al);
660 return ret;
661}
662
663static void display_error(int err)
664{
665 switch (err) {
666 case UNW_EINVAL:
667 pr_err("unwind: Only supports local.\n");
668 break;
669 case UNW_EUNSPEC:
670 pr_err("unwind: Unspecified error.\n");
671 break;
672 case UNW_EBADREG:
673 pr_err("unwind: Register unavailable.\n");
674 break;
675 default:
676 break;
677 }
678}
679
680static unw_accessors_t accessors = {
681 .find_proc_info = find_proc_info,
682 .put_unwind_info = put_unwind_info,
683 .get_dyn_info_list_addr = get_dyn_info_list_addr,
684 .access_mem = access_mem,
685 .access_reg = access_reg,
686 .access_fpreg = access_fpreg,
687 .resume = resume,
688 .get_proc_name = get_proc_name,
689};
690
691static int _unwind__prepare_access(struct maps *maps)
692{
693 void *addr_space = unw_create_addr_space(&accessors, 0);
694
695 RC_CHK_ACCESS(maps)->addr_space = addr_space;
696 if (!addr_space) {
697 pr_err("unwind: Can't create unwind address space.\n");
698 return -ENOMEM;
699 }
700
701 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
702 return 0;
703}
704
705static void _unwind__flush_access(struct maps *maps)
706{
707 unw_flush_cache(maps__addr_space(maps), 0, 0);
708}
709
710static void _unwind__finish_access(struct maps *maps)
711{
712 unw_destroy_addr_space(maps__addr_space(maps));
713}
714
715static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
716 void *arg, int max_stack)
717{
718 const char *arch = perf_env__arch(env: ui->machine->env);
719 u64 val;
720 unw_word_t ips[max_stack];
721 unw_addr_space_t addr_space;
722 unw_cursor_t c;
723 int ret, i = 0;
724
725 ret = perf_reg_value(regs: &val, idx: &ui->sample->user_regs,
726 perf_arch_reg_ip(arch));
727 if (ret)
728 return ret;
729
730 ips[i++] = (unw_word_t) val;
731
732 /*
733 * If we need more than one entry, do the DWARF
734 * unwind itself.
735 */
736 if (max_stack - 1 > 0) {
737 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
738 addr_space = maps__addr_space(thread__maps(ui->thread));
739
740 if (addr_space == NULL)
741 return -1;
742
743 ret = unw_init_remote(&c, addr_space, ui);
744 if (ret && !ui->best_effort)
745 display_error(err: ret);
746
747 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
748 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
749
750 /*
751 * Decrement the IP for any non-activation frames.
752 * this is required to properly find the srcline
753 * for caller frames.
754 * See also the documentation for dwfl_frame_pc(),
755 * which this code tries to replicate.
756 */
757 if (unw_is_signal_frame(&c) <= 0)
758 --ips[i];
759
760 ++i;
761 }
762
763 max_stack = i;
764 }
765
766 /*
767 * Display what we got based on the order setup.
768 */
769 for (i = 0; i < max_stack && !ret; i++) {
770 int j = i;
771
772 if (callchain_param.order == ORDER_CALLER)
773 j = max_stack - i - 1;
774 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
775 }
776
777 return ret;
778}
779
780static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
781 struct thread *thread,
782 struct perf_sample *data, int max_stack,
783 bool best_effort)
784{
785 struct unwind_info ui = {
786 .sample = data,
787 .thread = thread,
788 .machine = maps__machine(maps: thread__maps(thread)),
789 .best_effort = best_effort
790 };
791
792 if (!data->user_regs.regs)
793 return -EINVAL;
794
795 if (max_stack <= 0)
796 return -EINVAL;
797
798 return get_entries(ui: &ui, cb, arg, max_stack);
799}
800
801static struct unwind_libunwind_ops
802_unwind_libunwind_ops = {
803 .prepare_access = _unwind__prepare_access,
804 .flush_access = _unwind__flush_access,
805 .finish_access = _unwind__finish_access,
806 .get_entries = _unwind__get_entries,
807};
808
809#ifndef REMOTE_UNWIND_LIBUNWIND
810struct unwind_libunwind_ops *
811local_unwind_libunwind_ops = &_unwind_libunwind_ops;
812#endif
813

source code of linux/tools/perf/util/unwind-libunwind-local.c