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
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, 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, ".eh_frame_hdr",
320						     &dso->data.eh_frame_hdr_addr,
321						     &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) - map__pgoff(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, ui->machine, dso->data.eh_frame_hdr_offset,
339				   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, ".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, ".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, DSO_BINARY_TYPE__DEBUGLINK,
381				machine->root_dir, debuglink, PATH_MAX);
382			if (!ret) {
383				fd = open(debuglink, O_RDONLY);
384				if (fd >= 0) {
385					ofs = elf_section_offset(fd,
386							".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);
422	thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
423	ret = map__get(al.map);
424	addr_location__exit(&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, &segbase, &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, ui->machine, &segbase)) {
469		int fd = dso__data_get_fd(dso, ui->machine);
470		int is_exec = elf_is_exec(fd, 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, ui->machine,
546				   addr, (u8 *) data, 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(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(&start, &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(&val, &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);
648	e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &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);
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(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(&val, &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(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(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, 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