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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, &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 (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
305struct read_unwind_spec_eh_frame_maps_cb_args {
306 struct dso *dso;
307 u64 base_addr;
308};
309
310static 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
322static 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.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.eh_frame_hdr_addr,
340 &dso->data.eh_frame_hdr_offset);
341 dso->data.elf_base_addr = elf_base_address(fd);
342 dso__data_put_fd(dso);
343 if (ret || dso->data.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.elf_base_addr;
350 /* Address of .eh_frame_hdr */
351 *segbase = args.base_addr + dso->data.eh_frame_hdr_addr;
352 ret = unwind_spec_ehframe(dso, ui->machine, dso->data.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
362static int read_unwind_spec_debug_frame(struct dso *dso,
363 struct machine *machine, u64 *offset)
364{
365 int fd;
366 u64 ofs = dso->data.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, 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 ret = dso__read_binary_type_filename(
394 dso, DSO_BINARY_TYPE__DEBUGLINK,
395 machine->root_dir, debuglink, PATH_MAX);
396 if (!ret) {
397 fd = open(debuglink, O_RDONLY);
398 if (fd >= 0) {
399 ofs = elf_section_offset(fd,
400 ".debug_frame");
401 close(fd);
402 }
403 }
404 if (ofs > 0) {
405 if (dso->symsrc_filename != NULL) {
406 pr_warning(
407 "%s: overwrite symsrc(%s,%s)\n",
408 __func__,
409 dso->symsrc_filename,
410 debuglink);
411 zfree(&dso->symsrc_filename);
412 }
413 dso->symsrc_filename = debuglink;
414 } else {
415 free(debuglink);
416 }
417 }
418
419 dso->data.debug_frame_offset = ofs;
420 }
421
422 *offset = ofs;
423 if (*offset)
424 return 0;
425
426 return -EINVAL;
427}
428#endif
429
430static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
431{
432 struct addr_location al;
433 struct map *ret;
434
435 addr_location__init(&al);
436 thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
437 ret = map__get(al.map);
438 addr_location__exit(&al);
439 return ret;
440}
441
442static int
443find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
444 int need_unwind_info, void *arg)
445{
446 struct unwind_info *ui = arg;
447 struct map *map;
448 struct dso *dso;
449 unw_dyn_info_t di;
450 u64 table_data, segbase, fde_count;
451 int ret = -EINVAL;
452
453 map = find_map(ip, ui);
454 if (!map)
455 return -EINVAL;
456
457 dso = map__dso(map);
458 if (!dso) {
459 map__put(map);
460 return -EINVAL;
461 }
462
463 pr_debug("unwind: find_proc_info dso %s\n", dso->name);
464
465 /* Check the .eh_frame section for unwinding info */
466 if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) {
467 memset(&di, 0, sizeof(di));
468 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
469 di.start_ip = map__start(map);
470 di.end_ip = map__end(map);
471 di.u.rti.segbase = segbase;
472 di.u.rti.table_data = table_data;
473 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
474 / sizeof(unw_word_t);
475 ret = dwarf_search_unwind_table(as, ip, &di, pi,
476 need_unwind_info, arg);
477 }
478
479#ifndef NO_LIBUNWIND_DEBUG_FRAME
480 /* Check the .debug_frame section for unwinding info */
481 if (ret < 0 &&
482 !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) {
483 int fd = dso__data_get_fd(dso, ui->machine);
484 int is_exec = elf_is_exec(fd, dso->name);
485 u64 start = map__start(map);
486 unw_word_t base = is_exec ? 0 : start;
487 const char *symfile;
488
489 if (fd >= 0)
490 dso__data_put_fd(dso);
491
492 symfile = dso->symsrc_filename ?: dso->name;
493
494 memset(&di, 0, sizeof(di));
495 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
496 ret = dwarf_search_unwind_table(as, ip, &di, pi,
497 need_unwind_info, arg);
498 }
499#endif
500 map__put(map);
501 return ret;
502}
503
504static int access_fpreg(unw_addr_space_t __maybe_unused as,
505 unw_regnum_t __maybe_unused num,
506 unw_fpreg_t __maybe_unused *val,
507 int __maybe_unused __write,
508 void __maybe_unused *arg)
509{
510 pr_err("unwind: access_fpreg unsupported\n");
511 return -UNW_EINVAL;
512}
513
514static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
515 unw_word_t __maybe_unused *dil_addr,
516 void __maybe_unused *arg)
517{
518 return -UNW_ENOINFO;
519}
520
521static int resume(unw_addr_space_t __maybe_unused as,
522 unw_cursor_t __maybe_unused *cu,
523 void __maybe_unused *arg)
524{
525 pr_err("unwind: resume unsupported\n");
526 return -UNW_EINVAL;
527}
528
529static int
530get_proc_name(unw_addr_space_t __maybe_unused as,
531 unw_word_t __maybe_unused addr,
532 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
533 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
534{
535 pr_err("unwind: get_proc_name unsupported\n");
536 return -UNW_EINVAL;
537}
538
539static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
540 unw_word_t *data)
541{
542 struct map *map;
543 struct dso *dso;
544 ssize_t size;
545
546 map = find_map(addr, ui);
547 if (!map) {
548 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
549 return -1;
550 }
551
552 dso = map__dso(map);
553
554 if (!dso) {
555 map__put(map);
556 return -1;
557 }
558
559 size = dso__data_read_addr(dso, map, ui->machine,
560 addr, (u8 *) data, sizeof(*data));
561 map__put(map);
562 return !(size == sizeof(*data));
563}
564
565static int access_mem(unw_addr_space_t __maybe_unused as,
566 unw_word_t addr, unw_word_t *valp,
567 int __write, void *arg)
568{
569 struct unwind_info *ui = arg;
570 const char *arch = perf_env__arch(ui->machine->env);
571 struct stack_dump *stack = &ui->sample->user_stack;
572 u64 start, end;
573 int offset;
574 int ret;
575
576 /* Don't support write, probably not needed. */
577 if (__write || !stack || !ui->sample->user_regs.regs) {
578 *valp = 0;
579 return 0;
580 }
581
582 ret = perf_reg_value(&start, &ui->sample->user_regs,
583 perf_arch_reg_sp(arch));
584 if (ret)
585 return ret;
586
587 end = start + stack->size;
588
589 /* Check overflow. */
590 if (addr + sizeof(unw_word_t) < addr)
591 return -EINVAL;
592
593 if (addr < start || addr + sizeof(unw_word_t) >= end) {
594 ret = access_dso_mem(ui, addr, valp);
595 if (ret) {
596 pr_debug("unwind: access_mem %p not inside range"
597 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
598 (void *) (uintptr_t) addr, start, end);
599 *valp = 0;
600 return ret;
601 }
602 return 0;
603 }
604
605 offset = addr - start;
606 *valp = *(unw_word_t *)&stack->data[offset];
607 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
608 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
609 return 0;
610}
611
612static int access_reg(unw_addr_space_t __maybe_unused as,
613 unw_regnum_t regnum, unw_word_t *valp,
614 int __write, void *arg)
615{
616 struct unwind_info *ui = arg;
617 int id, ret;
618 u64 val;
619
620 /* Don't support write, I suspect we don't need it. */
621 if (__write) {
622 pr_err("unwind: access_reg w %d\n", regnum);
623 return 0;
624 }
625
626 if (!ui->sample->user_regs.regs) {
627 *valp = 0;
628 return 0;
629 }
630
631 id = LIBUNWIND__ARCH_REG_ID(regnum);
632 if (id < 0)
633 return -EINVAL;
634
635 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
636 if (ret) {
637 if (!ui->best_effort)
638 pr_err("unwind: can't read reg %d\n", regnum);
639 return ret;
640 }
641
642 *valp = (unw_word_t) val;
643 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
644 return 0;
645}
646
647static void put_unwind_info(unw_addr_space_t __maybe_unused as,
648 unw_proc_info_t *pi __maybe_unused,
649 void *arg __maybe_unused)
650{
651 pr_debug("unwind: put_unwind_info called\n");
652}
653
654static int entry(u64 ip, struct thread *thread,
655 unwind_entry_cb_t cb, void *arg)
656{
657 struct unwind_entry e;
658 struct addr_location al;
659 int ret;
660
661 addr_location__init(&al);
662 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
663 e.ip = ip;
664 e.ms.map = al.map;
665 e.ms.maps = al.maps;
666
667 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
668 al.sym ? al.sym->name : "''",
669 ip,
670 al.map ? map__map_ip(al.map, ip) : (u64) 0);
671
672 ret = cb(&e, arg);
673 addr_location__exit(&al);
674 return ret;
675}
676
677static void display_error(int err)
678{
679 switch (err) {
680 case UNW_EINVAL:
681 pr_err("unwind: Only supports local.\n");
682 break;
683 case UNW_EUNSPEC:
684 pr_err("unwind: Unspecified error.\n");
685 break;
686 case UNW_EBADREG:
687 pr_err("unwind: Register unavailable.\n");
688 break;
689 default:
690 break;
691 }
692}
693
694static unw_accessors_t accessors = {
695 .find_proc_info = find_proc_info,
696 .put_unwind_info = put_unwind_info,
697 .get_dyn_info_list_addr = get_dyn_info_list_addr,
698 .access_mem = access_mem,
699 .access_reg = access_reg,
700 .access_fpreg = access_fpreg,
701 .resume = resume,
702 .get_proc_name = get_proc_name,
703};
704
705static int _unwind__prepare_access(struct maps *maps)
706{
707 void *addr_space = unw_create_addr_space(&accessors, 0);
708
709 RC_CHK_ACCESS(maps)->addr_space = addr_space;
710 if (!addr_space) {
711 pr_err("unwind: Can't create unwind address space.\n");
712 return -ENOMEM;
713 }
714
715 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
716 return 0;
717}
718
719static void _unwind__flush_access(struct maps *maps)
720{
721 unw_flush_cache(maps__addr_space(maps), 0, 0);
722}
723
724static void _unwind__finish_access(struct maps *maps)
725{
726 unw_destroy_addr_space(maps__addr_space(maps));
727}
728
729static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
730 void *arg, int max_stack)
731{
732 const char *arch = perf_env__arch(ui->machine->env);
733 u64 val;
734 unw_word_t ips[max_stack];
735 unw_addr_space_t addr_space;
736 unw_cursor_t c;
737 int ret, i = 0;
738
739 ret = perf_reg_value(&val, &ui->sample->user_regs,
740 perf_arch_reg_ip(arch));
741 if (ret)
742 return ret;
743
744 ips[i++] = (unw_word_t) val;
745
746 /*
747 * If we need more than one entry, do the DWARF
748 * unwind itself.
749 */
750 if (max_stack - 1 > 0) {
751 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
752 addr_space = maps__addr_space(thread__maps(ui->thread));
753
754 if (addr_space == NULL)
755 return -1;
756
757 ret = unw_init_remote(&c, addr_space, ui);
758 if (ret && !ui->best_effort)
759 display_error(ret);
760
761 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
762 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
763
764 /*
765 * Decrement the IP for any non-activation frames.
766 * this is required to properly find the srcline
767 * for caller frames.
768 * See also the documentation for dwfl_frame_pc(),
769 * which this code tries to replicate.
770 */
771 if (unw_is_signal_frame(&c) <= 0)
772 --ips[i];
773
774 ++i;
775 }
776
777 max_stack = i;
778 }
779
780 /*
781 * Display what we got based on the order setup.
782 */
783 for (i = 0; i < max_stack && !ret; i++) {
784 int j = i;
785
786 if (callchain_param.order == ORDER_CALLER)
787 j = max_stack - i - 1;
788 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
789 }
790
791 return ret;
792}
793
794static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
795 struct thread *thread,
796 struct perf_sample *data, int max_stack,
797 bool best_effort)
798{
799 struct unwind_info ui = {
800 .sample = data,
801 .thread = thread,
802 .machine = maps__machine(thread__maps(thread)),
803 .best_effort = best_effort
804 };
805
806 if (!data->user_regs.regs)
807 return -EINVAL;
808
809 if (max_stack <= 0)
810 return -EINVAL;
811
812 return get_entries(&ui, cb, arg, max_stack);
813}
814
815static struct unwind_libunwind_ops
816_unwind_libunwind_ops = {
817 .prepare_access = _unwind__prepare_access,
818 .flush_access = _unwind__flush_access,
819 .finish_access = _unwind__finish_access,
820 .get_entries = _unwind__get_entries,
821};
822
823#ifndef REMOTE_UNWIND_LIBUNWIND
824struct unwind_libunwind_ops *
825local_unwind_libunwind_ops = &_unwind_libunwind_ops;
826#endif