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1// SPDX-License-Identifier: GPL-2.0
2#include "unwind.h"
3#include "dso.h"
4#include "map.h"
5#include "thread.h"
6#include "session.h"
7#include "debug.h"
8#include "env.h"
9#include "callchain.h"
10
11struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops;
12struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops;
13struct unwind_libunwind_ops __weak *arm64_unwind_libunwind_ops;
14
15static void unwind__register_ops(struct maps *maps, struct unwind_libunwind_ops *ops)
16{
17 RC_CHK_ACCESS(maps)->unwind_libunwind_ops = ops;
18}
19
20int unwind__prepare_access(struct maps *maps, struct map *map, bool *initialized)
21{
22 const char *arch;
23 enum dso_type dso_type;
24 struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops;
25 struct dso *dso = map__dso(map);
26 struct machine *machine;
27 int err;
28
29 if (!dwarf_callchain_users)
30 return 0;
31
32 if (maps__addr_space(maps)) {
33 pr_debug("unwind: thread map already set, dso=%s\n", dso->name);
34 if (initialized)
35 *initialized = true;
36 return 0;
37 }
38
39 machine = maps__machine(maps);
40 /* env->arch is NULL for live-mode (i.e. perf top) */
41 if (!machine->env || !machine->env->arch)
42 goto out_register;
43
44 dso_type = dso__type(dso, machine);
45 if (dso_type == DSO__TYPE_UNKNOWN)
46 return 0;
47
48 arch = perf_env__arch(machine->env);
49
50 if (!strcmp(arch, "x86")) {
51 if (dso_type != DSO__TYPE_64BIT)
52 ops = x86_32_unwind_libunwind_ops;
53 } else if (!strcmp(arch, "arm64") || !strcmp(arch, "arm")) {
54 if (dso_type == DSO__TYPE_64BIT)
55 ops = arm64_unwind_libunwind_ops;
56 }
57
58 if (!ops) {
59 pr_warning_once("unwind: target platform=%s is not supported\n", arch);
60 return 0;
61 }
62out_register:
63 unwind__register_ops(maps, ops);
64
65 err = maps__unwind_libunwind_ops(maps)->prepare_access(maps);
66 if (initialized)
67 *initialized = err ? false : true;
68 return err;
69}
70
71void unwind__flush_access(struct maps *maps)
72{
73 const struct unwind_libunwind_ops *ops = maps__unwind_libunwind_ops(maps);
74
75 if (ops)
76 ops->flush_access(maps);
77}
78
79void unwind__finish_access(struct maps *maps)
80{
81 const struct unwind_libunwind_ops *ops = maps__unwind_libunwind_ops(maps);
82
83 if (ops)
84 ops->finish_access(maps);
85}
86
87int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
88 struct thread *thread,
89 struct perf_sample *data, int max_stack,
90 bool best_effort)
91{
92 const struct unwind_libunwind_ops *ops = maps__unwind_libunwind_ops(thread__maps(thread));
93
94 if (ops)
95 return ops->get_entries(cb, arg, thread, data, max_stack, best_effort);
96 return 0;
97}
1/*
2 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
3 *
4 * Lots of this code have been borrowed or heavily inspired from parts of
5 * the libunwind 0.99 code which are (amongst other contributors I may have
6 * forgotten):
7 *
8 * Copyright (C) 2002-2007 Hewlett-Packard Co
9 * Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
10 *
11 * And the bugs have been added by:
12 *
13 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
14 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
15 *
16 */
17
18#include <elf.h>
19#include <gelf.h>
20#include <fcntl.h>
21#include <string.h>
22#include <unistd.h>
23#include <sys/mman.h>
24#include <linux/list.h>
25#include <libunwind.h>
26#include <libunwind-ptrace.h>
27#include "callchain.h"
28#include "thread.h"
29#include "session.h"
30#include "perf_regs.h"
31#include "unwind.h"
32#include "symbol.h"
33#include "util.h"
34#include "debug.h"
35
36extern int
37UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
38 unw_word_t ip,
39 unw_dyn_info_t *di,
40 unw_proc_info_t *pi,
41 int need_unwind_info, void *arg);
42
43#define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
44
45extern int
46UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
47 unw_word_t ip,
48 unw_word_t segbase,
49 const char *obj_name, unw_word_t start,
50 unw_word_t end);
51
52#define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
53
54#define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
55#define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
56
57/* Pointer-encoding formats: */
58#define DW_EH_PE_omit 0xff
59#define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
60#define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
61#define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
62#define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
63#define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
64
65/* Pointer-encoding application: */
66#define DW_EH_PE_absptr 0x00 /* absolute value */
67#define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
68
69/*
70 * The following are not documented by LSB v1.3, yet they are used by
71 * GCC, presumably they aren't documented by LSB since they aren't
72 * used on Linux:
73 */
74#define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
75#define DW_EH_PE_aligned 0x50 /* aligned pointer */
76
77/* Flags intentionaly not handled, since they're not needed:
78 * #define DW_EH_PE_indirect 0x80
79 * #define DW_EH_PE_uleb128 0x01
80 * #define DW_EH_PE_udata2 0x02
81 * #define DW_EH_PE_sleb128 0x09
82 * #define DW_EH_PE_sdata2 0x0a
83 * #define DW_EH_PE_textrel 0x20
84 * #define DW_EH_PE_datarel 0x30
85 */
86
87struct unwind_info {
88 struct perf_sample *sample;
89 struct machine *machine;
90 struct thread *thread;
91};
92
93#define dw_read(ptr, type, end) ({ \
94 type *__p = (type *) ptr; \
95 type __v; \
96 if ((__p + 1) > (type *) end) \
97 return -EINVAL; \
98 __v = *__p++; \
99 ptr = (typeof(ptr)) __p; \
100 __v; \
101 })
102
103static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
104 u8 encoding)
105{
106 u8 *cur = *p;
107 *val = 0;
108
109 switch (encoding) {
110 case DW_EH_PE_omit:
111 *val = 0;
112 goto out;
113 case DW_EH_PE_ptr:
114 *val = dw_read(cur, unsigned long, end);
115 goto out;
116 default:
117 break;
118 }
119
120 switch (encoding & DW_EH_PE_APPL_MASK) {
121 case DW_EH_PE_absptr:
122 break;
123 case DW_EH_PE_pcrel:
124 *val = (unsigned long) cur;
125 break;
126 default:
127 return -EINVAL;
128 }
129
130 if ((encoding & 0x07) == 0x00)
131 encoding |= DW_EH_PE_udata4;
132
133 switch (encoding & DW_EH_PE_FORMAT_MASK) {
134 case DW_EH_PE_sdata4:
135 *val += dw_read(cur, s32, end);
136 break;
137 case DW_EH_PE_udata4:
138 *val += dw_read(cur, u32, end);
139 break;
140 case DW_EH_PE_sdata8:
141 *val += dw_read(cur, s64, end);
142 break;
143 case DW_EH_PE_udata8:
144 *val += dw_read(cur, u64, end);
145 break;
146 default:
147 return -EINVAL;
148 }
149
150 out:
151 *p = cur;
152 return 0;
153}
154
155#define dw_read_encoded_value(ptr, end, enc) ({ \
156 u64 __v; \
157 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
158 return -EINVAL; \
159 } \
160 __v; \
161 })
162
163static u64 elf_section_offset(int fd, const char *name)
164{
165 Elf *elf;
166 GElf_Ehdr ehdr;
167 GElf_Shdr shdr;
168 u64 offset = 0;
169
170 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
171 if (elf == NULL)
172 return 0;
173
174 do {
175 if (gelf_getehdr(elf, &ehdr) == NULL)
176 break;
177
178 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
179 break;
180
181 offset = shdr.sh_offset;
182 } while (0);
183
184 elf_end(elf);
185 return offset;
186}
187
188#ifndef NO_LIBUNWIND_DEBUG_FRAME
189static int elf_is_exec(int fd, const char *name)
190{
191 Elf *elf;
192 GElf_Ehdr ehdr;
193 int retval = 0;
194
195 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
196 if (elf == NULL)
197 return 0;
198 if (gelf_getehdr(elf, &ehdr) == NULL)
199 goto out;
200
201 retval = (ehdr.e_type == ET_EXEC);
202
203out:
204 elf_end(elf);
205 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
206 return retval;
207}
208#endif
209
210struct table_entry {
211 u32 start_ip_offset;
212 u32 fde_offset;
213};
214
215struct eh_frame_hdr {
216 unsigned char version;
217 unsigned char eh_frame_ptr_enc;
218 unsigned char fde_count_enc;
219 unsigned char table_enc;
220
221 /*
222 * The rest of the header is variable-length and consists of the
223 * following members:
224 *
225 * encoded_t eh_frame_ptr;
226 * encoded_t fde_count;
227 */
228
229 /* A single encoded pointer should not be more than 8 bytes. */
230 u64 enc[2];
231
232 /*
233 * struct {
234 * encoded_t start_ip;
235 * encoded_t fde_addr;
236 * } binary_search_table[fde_count];
237 */
238 char data[0];
239} __packed;
240
241static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
242 u64 offset, u64 *table_data, u64 *segbase,
243 u64 *fde_count)
244{
245 struct eh_frame_hdr hdr;
246 u8 *enc = (u8 *) &hdr.enc;
247 u8 *end = (u8 *) &hdr.data;
248 ssize_t r;
249
250 r = dso__data_read_offset(dso, machine, offset,
251 (u8 *) &hdr, sizeof(hdr));
252 if (r != sizeof(hdr))
253 return -EINVAL;
254
255 /* We dont need eh_frame_ptr, just skip it. */
256 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
257
258 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
259 *segbase = offset;
260 *table_data = (enc - (u8 *) &hdr) + offset;
261 return 0;
262}
263
264static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
265 u64 *table_data, u64 *segbase,
266 u64 *fde_count)
267{
268 int ret = -EINVAL, fd;
269 u64 offset = dso->data.eh_frame_hdr_offset;
270
271 if (offset == 0) {
272 fd = dso__data_get_fd(dso, machine);
273 if (fd < 0)
274 return -EINVAL;
275
276 /* Check the .eh_frame section for unwinding info */
277 offset = elf_section_offset(fd, ".eh_frame_hdr");
278 dso->data.eh_frame_hdr_offset = offset;
279 dso__data_put_fd(dso);
280 }
281
282 if (offset)
283 ret = unwind_spec_ehframe(dso, machine, offset,
284 table_data, segbase,
285 fde_count);
286
287 return ret;
288}
289
290#ifndef NO_LIBUNWIND_DEBUG_FRAME
291static int read_unwind_spec_debug_frame(struct dso *dso,
292 struct machine *machine, u64 *offset)
293{
294 int fd;
295 u64 ofs = dso->data.debug_frame_offset;
296
297 if (ofs == 0) {
298 fd = dso__data_get_fd(dso, machine);
299 if (fd < 0)
300 return -EINVAL;
301
302 /* Check the .debug_frame section for unwinding info */
303 ofs = elf_section_offset(fd, ".debug_frame");
304 dso->data.debug_frame_offset = ofs;
305 dso__data_put_fd(dso);
306 }
307
308 *offset = ofs;
309 if (*offset)
310 return 0;
311
312 return -EINVAL;
313}
314#endif
315
316static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
317{
318 struct addr_location al;
319
320 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
321 MAP__FUNCTION, ip, &al);
322 if (!al.map) {
323 /*
324 * We've seen cases (softice) where DWARF unwinder went
325 * through non executable mmaps, which we need to lookup
326 * in MAP__VARIABLE tree.
327 */
328 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
329 MAP__VARIABLE, ip, &al);
330 }
331 return al.map;
332}
333
334static int
335find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
336 int need_unwind_info, void *arg)
337{
338 struct unwind_info *ui = arg;
339 struct map *map;
340 unw_dyn_info_t di;
341 u64 table_data, segbase, fde_count;
342 int ret = -EINVAL;
343
344 map = find_map(ip, ui);
345 if (!map || !map->dso)
346 return -EINVAL;
347
348 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
349
350 /* Check the .eh_frame section for unwinding info */
351 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
352 &table_data, &segbase, &fde_count)) {
353 memset(&di, 0, sizeof(di));
354 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
355 di.start_ip = map->start;
356 di.end_ip = map->end;
357 di.u.rti.segbase = map->start + segbase;
358 di.u.rti.table_data = map->start + table_data;
359 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
360 / sizeof(unw_word_t);
361 ret = dwarf_search_unwind_table(as, ip, &di, pi,
362 need_unwind_info, arg);
363 }
364
365#ifndef NO_LIBUNWIND_DEBUG_FRAME
366 /* Check the .debug_frame section for unwinding info */
367 if (ret < 0 &&
368 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
369 int fd = dso__data_get_fd(map->dso, ui->machine);
370 int is_exec = elf_is_exec(fd, map->dso->name);
371 unw_word_t base = is_exec ? 0 : map->start;
372 const char *symfile;
373
374 if (fd >= 0)
375 dso__data_put_fd(map->dso);
376
377 symfile = map->dso->symsrc_filename ?: map->dso->name;
378
379 memset(&di, 0, sizeof(di));
380 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
381 map->start, map->end))
382 return dwarf_search_unwind_table(as, ip, &di, pi,
383 need_unwind_info, arg);
384 }
385#endif
386
387 return ret;
388}
389
390static int access_fpreg(unw_addr_space_t __maybe_unused as,
391 unw_regnum_t __maybe_unused num,
392 unw_fpreg_t __maybe_unused *val,
393 int __maybe_unused __write,
394 void __maybe_unused *arg)
395{
396 pr_err("unwind: access_fpreg unsupported\n");
397 return -UNW_EINVAL;
398}
399
400static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
401 unw_word_t __maybe_unused *dil_addr,
402 void __maybe_unused *arg)
403{
404 return -UNW_ENOINFO;
405}
406
407static int resume(unw_addr_space_t __maybe_unused as,
408 unw_cursor_t __maybe_unused *cu,
409 void __maybe_unused *arg)
410{
411 pr_err("unwind: resume unsupported\n");
412 return -UNW_EINVAL;
413}
414
415static int
416get_proc_name(unw_addr_space_t __maybe_unused as,
417 unw_word_t __maybe_unused addr,
418 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
419 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
420{
421 pr_err("unwind: get_proc_name unsupported\n");
422 return -UNW_EINVAL;
423}
424
425static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
426 unw_word_t *data)
427{
428 struct map *map;
429 ssize_t size;
430
431 map = find_map(addr, ui);
432 if (!map) {
433 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
434 return -1;
435 }
436
437 if (!map->dso)
438 return -1;
439
440 size = dso__data_read_addr(map->dso, map, ui->machine,
441 addr, (u8 *) data, sizeof(*data));
442
443 return !(size == sizeof(*data));
444}
445
446static int access_mem(unw_addr_space_t __maybe_unused as,
447 unw_word_t addr, unw_word_t *valp,
448 int __write, void *arg)
449{
450 struct unwind_info *ui = arg;
451 struct stack_dump *stack = &ui->sample->user_stack;
452 u64 start, end;
453 int offset;
454 int ret;
455
456 /* Don't support write, probably not needed. */
457 if (__write || !stack || !ui->sample->user_regs.regs) {
458 *valp = 0;
459 return 0;
460 }
461
462 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
463 if (ret)
464 return ret;
465
466 end = start + stack->size;
467
468 /* Check overflow. */
469 if (addr + sizeof(unw_word_t) < addr)
470 return -EINVAL;
471
472 if (addr < start || addr + sizeof(unw_word_t) >= end) {
473 ret = access_dso_mem(ui, addr, valp);
474 if (ret) {
475 pr_debug("unwind: access_mem %p not inside range"
476 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
477 (void *) (uintptr_t) addr, start, end);
478 *valp = 0;
479 return ret;
480 }
481 return 0;
482 }
483
484 offset = addr - start;
485 *valp = *(unw_word_t *)&stack->data[offset];
486 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
487 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
488 return 0;
489}
490
491static int access_reg(unw_addr_space_t __maybe_unused as,
492 unw_regnum_t regnum, unw_word_t *valp,
493 int __write, void *arg)
494{
495 struct unwind_info *ui = arg;
496 int id, ret;
497 u64 val;
498
499 /* Don't support write, I suspect we don't need it. */
500 if (__write) {
501 pr_err("unwind: access_reg w %d\n", regnum);
502 return 0;
503 }
504
505 if (!ui->sample->user_regs.regs) {
506 *valp = 0;
507 return 0;
508 }
509
510 id = libunwind__arch_reg_id(regnum);
511 if (id < 0)
512 return -EINVAL;
513
514 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
515 if (ret) {
516 pr_err("unwind: can't read reg %d\n", regnum);
517 return ret;
518 }
519
520 *valp = (unw_word_t) val;
521 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
522 return 0;
523}
524
525static void put_unwind_info(unw_addr_space_t __maybe_unused as,
526 unw_proc_info_t *pi __maybe_unused,
527 void *arg __maybe_unused)
528{
529 pr_debug("unwind: put_unwind_info called\n");
530}
531
532static int entry(u64 ip, struct thread *thread,
533 unwind_entry_cb_t cb, void *arg)
534{
535 struct unwind_entry e;
536 struct addr_location al;
537
538 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
539 MAP__FUNCTION, ip, &al);
540
541 e.ip = ip;
542 e.map = al.map;
543 e.sym = al.sym;
544
545 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
546 al.sym ? al.sym->name : "''",
547 ip,
548 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
549
550 return cb(&e, arg);
551}
552
553static void display_error(int err)
554{
555 switch (err) {
556 case UNW_EINVAL:
557 pr_err("unwind: Only supports local.\n");
558 break;
559 case UNW_EUNSPEC:
560 pr_err("unwind: Unspecified error.\n");
561 break;
562 case UNW_EBADREG:
563 pr_err("unwind: Register unavailable.\n");
564 break;
565 default:
566 break;
567 }
568}
569
570static unw_accessors_t accessors = {
571 .find_proc_info = find_proc_info,
572 .put_unwind_info = put_unwind_info,
573 .get_dyn_info_list_addr = get_dyn_info_list_addr,
574 .access_mem = access_mem,
575 .access_reg = access_reg,
576 .access_fpreg = access_fpreg,
577 .resume = resume,
578 .get_proc_name = get_proc_name,
579};
580
581int unwind__prepare_access(struct thread *thread)
582{
583 unw_addr_space_t addr_space;
584
585 if (callchain_param.record_mode != CALLCHAIN_DWARF)
586 return 0;
587
588 addr_space = unw_create_addr_space(&accessors, 0);
589 if (!addr_space) {
590 pr_err("unwind: Can't create unwind address space.\n");
591 return -ENOMEM;
592 }
593
594 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
595 thread__set_priv(thread, addr_space);
596
597 return 0;
598}
599
600void unwind__flush_access(struct thread *thread)
601{
602 unw_addr_space_t addr_space;
603
604 if (callchain_param.record_mode != CALLCHAIN_DWARF)
605 return;
606
607 addr_space = thread__priv(thread);
608 unw_flush_cache(addr_space, 0, 0);
609}
610
611void unwind__finish_access(struct thread *thread)
612{
613 unw_addr_space_t addr_space;
614
615 if (callchain_param.record_mode != CALLCHAIN_DWARF)
616 return;
617
618 addr_space = thread__priv(thread);
619 unw_destroy_addr_space(addr_space);
620}
621
622static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
623 void *arg, int max_stack)
624{
625 u64 val;
626 unw_word_t ips[max_stack];
627 unw_addr_space_t addr_space;
628 unw_cursor_t c;
629 int ret, i = 0;
630
631 ret = perf_reg_value(&val, &ui->sample->user_regs, PERF_REG_IP);
632 if (ret)
633 return ret;
634
635 ips[i++] = (unw_word_t) val;
636
637 /*
638 * If we need more than one entry, do the DWARF
639 * unwind itself.
640 */
641 if (max_stack - 1 > 0) {
642 addr_space = thread__priv(ui->thread);
643 if (addr_space == NULL)
644 return -1;
645
646 ret = unw_init_remote(&c, addr_space, ui);
647 if (ret)
648 display_error(ret);
649
650 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
651 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
652 ++i;
653 }
654
655 max_stack = i;
656 }
657
658 /*
659 * Display what we got based on the order setup.
660 */
661 for (i = 0; i < max_stack && !ret; i++) {
662 int j = i;
663
664 if (callchain_param.order == ORDER_CALLER)
665 j = max_stack - i - 1;
666 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
667 }
668
669 return ret;
670}
671
672int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
673 struct thread *thread,
674 struct perf_sample *data, int max_stack)
675{
676 struct unwind_info ui = {
677 .sample = data,
678 .thread = thread,
679 .machine = thread->mg->machine,
680 };
681
682 if (!data->user_regs.regs)
683 return -EINVAL;
684
685 if (max_stack <= 0)
686 return -EINVAL;
687
688 return get_entries(&ui, cb, arg, max_stack);
689}