xref: /openbmc/linux/tools/perf/util/build-id.c (revision 51c7b447)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * build-id.c
4  *
5  * build-id support
6  *
7  * Copyright (C) 2009, 2010 Red Hat Inc.
8  * Copyright (C) 2009, 2010 Arnaldo Carvalho de Melo <acme@redhat.com>
9  */
10 #include "util.h"
11 #include <dirent.h>
12 #include <errno.h>
13 #include <stdio.h>
14 #include <sys/stat.h>
15 #include <sys/types.h>
16 #include "build-id.h"
17 #include "event.h"
18 #include "namespaces.h"
19 #include "map.h"
20 #include "symbol.h"
21 #include "thread.h"
22 #include <linux/kernel.h>
23 #include "debug.h"
24 #include "session.h"
25 #include "tool.h"
26 #include "header.h"
27 #include "vdso.h"
28 #include "path.h"
29 #include "probe-file.h"
30 #include "strlist.h"
31 
32 #include "sane_ctype.h"
33 
34 static bool no_buildid_cache;
35 
36 int build_id__mark_dso_hit(struct perf_tool *tool __maybe_unused,
37 			   union perf_event *event,
38 			   struct perf_sample *sample,
39 			   struct perf_evsel *evsel __maybe_unused,
40 			   struct machine *machine)
41 {
42 	struct addr_location al;
43 	struct thread *thread = machine__findnew_thread(machine, sample->pid,
44 							sample->tid);
45 
46 	if (thread == NULL) {
47 		pr_err("problem processing %d event, skipping it.\n",
48 			event->header.type);
49 		return -1;
50 	}
51 
52 	if (thread__find_map(thread, sample->cpumode, sample->ip, &al))
53 		al.map->dso->hit = 1;
54 
55 	thread__put(thread);
56 	return 0;
57 }
58 
59 static int perf_event__exit_del_thread(struct perf_tool *tool __maybe_unused,
60 				       union perf_event *event,
61 				       struct perf_sample *sample
62 				       __maybe_unused,
63 				       struct machine *machine)
64 {
65 	struct thread *thread = machine__findnew_thread(machine,
66 							event->fork.pid,
67 							event->fork.tid);
68 
69 	dump_printf("(%d:%d):(%d:%d)\n", event->fork.pid, event->fork.tid,
70 		    event->fork.ppid, event->fork.ptid);
71 
72 	if (thread) {
73 		machine__remove_thread(machine, thread);
74 		thread__put(thread);
75 	}
76 
77 	return 0;
78 }
79 
80 struct perf_tool build_id__mark_dso_hit_ops = {
81 	.sample	= build_id__mark_dso_hit,
82 	.mmap	= perf_event__process_mmap,
83 	.mmap2	= perf_event__process_mmap2,
84 	.fork	= perf_event__process_fork,
85 	.exit	= perf_event__exit_del_thread,
86 	.attr		 = perf_event__process_attr,
87 	.build_id	 = perf_event__process_build_id,
88 	.ordered_events	 = true,
89 };
90 
91 int build_id__sprintf(const u8 *build_id, int len, char *bf)
92 {
93 	char *bid = bf;
94 	const u8 *raw = build_id;
95 	int i;
96 
97 	for (i = 0; i < len; ++i) {
98 		sprintf(bid, "%02x", *raw);
99 		++raw;
100 		bid += 2;
101 	}
102 
103 	return (bid - bf) + 1;
104 }
105 
106 int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id)
107 {
108 	char notes[PATH_MAX];
109 	u8 build_id[BUILD_ID_SIZE];
110 	int ret;
111 
112 	if (!root_dir)
113 		root_dir = "";
114 
115 	scnprintf(notes, sizeof(notes), "%s/sys/kernel/notes", root_dir);
116 
117 	ret = sysfs__read_build_id(notes, build_id, sizeof(build_id));
118 	if (ret < 0)
119 		return ret;
120 
121 	return build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
122 }
123 
124 int filename__sprintf_build_id(const char *pathname, char *sbuild_id)
125 {
126 	u8 build_id[BUILD_ID_SIZE];
127 	int ret;
128 
129 	ret = filename__read_build_id(pathname, build_id, sizeof(build_id));
130 	if (ret < 0)
131 		return ret;
132 	else if (ret != sizeof(build_id))
133 		return -EINVAL;
134 
135 	return build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
136 }
137 
138 /* asnprintf consolidates asprintf and snprintf */
139 static int asnprintf(char **strp, size_t size, const char *fmt, ...)
140 {
141 	va_list ap;
142 	int ret;
143 
144 	if (!strp)
145 		return -EINVAL;
146 
147 	va_start(ap, fmt);
148 	if (*strp)
149 		ret = vsnprintf(*strp, size, fmt, ap);
150 	else
151 		ret = vasprintf(strp, fmt, ap);
152 	va_end(ap);
153 
154 	return ret;
155 }
156 
157 char *build_id_cache__kallsyms_path(const char *sbuild_id, char *bf,
158 				    size_t size)
159 {
160 	bool retry_old = true;
161 
162 	snprintf(bf, size, "%s/%s/%s/kallsyms",
163 		 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
164 retry:
165 	if (!access(bf, F_OK))
166 		return bf;
167 	if (retry_old) {
168 		/* Try old style kallsyms cache */
169 		snprintf(bf, size, "%s/%s/%s",
170 			 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
171 		retry_old = false;
172 		goto retry;
173 	}
174 
175 	return NULL;
176 }
177 
178 char *build_id_cache__linkname(const char *sbuild_id, char *bf, size_t size)
179 {
180 	char *tmp = bf;
181 	int ret = asnprintf(&bf, size, "%s/.build-id/%.2s/%s", buildid_dir,
182 			    sbuild_id, sbuild_id + 2);
183 	if (ret < 0 || (tmp && size < (unsigned int)ret))
184 		return NULL;
185 	return bf;
186 }
187 
188 /* The caller is responsible to free the returned buffer. */
189 char *build_id_cache__origname(const char *sbuild_id)
190 {
191 	char *linkname;
192 	char buf[PATH_MAX];
193 	char *ret = NULL, *p;
194 	size_t offs = 5;	/* == strlen("../..") */
195 	ssize_t len;
196 
197 	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
198 	if (!linkname)
199 		return NULL;
200 
201 	len = readlink(linkname, buf, sizeof(buf) - 1);
202 	if (len <= 0)
203 		goto out;
204 	buf[len] = '\0';
205 
206 	/* The link should be "../..<origpath>/<sbuild_id>" */
207 	p = strrchr(buf, '/');	/* Cut off the "/<sbuild_id>" */
208 	if (p && (p > buf + offs)) {
209 		*p = '\0';
210 		if (buf[offs + 1] == '[')
211 			offs++;	/*
212 				 * This is a DSO name, like [kernel.kallsyms].
213 				 * Skip the first '/', since this is not the
214 				 * cache of a regular file.
215 				 */
216 		ret = strdup(buf + offs);	/* Skip "../..[/]" */
217 	}
218 out:
219 	free(linkname);
220 	return ret;
221 }
222 
223 /* Check if the given build_id cache is valid on current running system */
224 static bool build_id_cache__valid_id(char *sbuild_id)
225 {
226 	char real_sbuild_id[SBUILD_ID_SIZE] = "";
227 	char *pathname;
228 	int ret = 0;
229 	bool result = false;
230 
231 	pathname = build_id_cache__origname(sbuild_id);
232 	if (!pathname)
233 		return false;
234 
235 	if (!strcmp(pathname, DSO__NAME_KALLSYMS))
236 		ret = sysfs__sprintf_build_id("/", real_sbuild_id);
237 	else if (pathname[0] == '/')
238 		ret = filename__sprintf_build_id(pathname, real_sbuild_id);
239 	else
240 		ret = -EINVAL;	/* Should we support other special DSO cache? */
241 	if (ret >= 0)
242 		result = (strcmp(sbuild_id, real_sbuild_id) == 0);
243 	free(pathname);
244 
245 	return result;
246 }
247 
248 static const char *build_id_cache__basename(bool is_kallsyms, bool is_vdso,
249 					    bool is_debug)
250 {
251 	return is_kallsyms ? "kallsyms" : (is_vdso ? "vdso" : (is_debug ?
252 	    "debug" : "elf"));
253 }
254 
255 char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
256 			     bool is_debug)
257 {
258 	bool is_kallsyms = dso__is_kallsyms((struct dso *)dso);
259 	bool is_vdso = dso__is_vdso((struct dso *)dso);
260 	char sbuild_id[SBUILD_ID_SIZE];
261 	char *linkname;
262 	bool alloc = (bf == NULL);
263 	int ret;
264 
265 	if (!dso->has_build_id)
266 		return NULL;
267 
268 	build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
269 	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
270 	if (!linkname)
271 		return NULL;
272 
273 	/* Check if old style build_id cache */
274 	if (is_regular_file(linkname))
275 		ret = asnprintf(&bf, size, "%s", linkname);
276 	else
277 		ret = asnprintf(&bf, size, "%s/%s", linkname,
278 			 build_id_cache__basename(is_kallsyms, is_vdso,
279 						  is_debug));
280 	if (ret < 0 || (!alloc && size < (unsigned int)ret))
281 		bf = NULL;
282 	free(linkname);
283 
284 	return bf;
285 }
286 
287 #define dsos__for_each_with_build_id(pos, head)	\
288 	list_for_each_entry(pos, head, node)	\
289 		if (!pos->has_build_id)		\
290 			continue;		\
291 		else
292 
293 static int write_buildid(const char *name, size_t name_len, u8 *build_id,
294 			 pid_t pid, u16 misc, struct feat_fd *fd)
295 {
296 	int err;
297 	struct build_id_event b;
298 	size_t len;
299 
300 	len = name_len + 1;
301 	len = PERF_ALIGN(len, NAME_ALIGN);
302 
303 	memset(&b, 0, sizeof(b));
304 	memcpy(&b.build_id, build_id, BUILD_ID_SIZE);
305 	b.pid = pid;
306 	b.header.misc = misc;
307 	b.header.size = sizeof(b) + len;
308 
309 	err = do_write(fd, &b, sizeof(b));
310 	if (err < 0)
311 		return err;
312 
313 	return write_padded(fd, name, name_len + 1, len);
314 }
315 
316 static int machine__write_buildid_table(struct machine *machine,
317 					struct feat_fd *fd)
318 {
319 	int err = 0;
320 	struct dso *pos;
321 	u16 kmisc = PERF_RECORD_MISC_KERNEL,
322 	    umisc = PERF_RECORD_MISC_USER;
323 
324 	if (!machine__is_host(machine)) {
325 		kmisc = PERF_RECORD_MISC_GUEST_KERNEL;
326 		umisc = PERF_RECORD_MISC_GUEST_USER;
327 	}
328 
329 	dsos__for_each_with_build_id(pos, &machine->dsos.head) {
330 		const char *name;
331 		size_t name_len;
332 		bool in_kernel = false;
333 
334 		if (!pos->hit && !dso__is_vdso(pos))
335 			continue;
336 
337 		if (dso__is_vdso(pos)) {
338 			name = pos->short_name;
339 			name_len = pos->short_name_len;
340 		} else if (dso__is_kcore(pos)) {
341 			name = machine->mmap_name;
342 			name_len = strlen(name);
343 		} else {
344 			name = pos->long_name;
345 			name_len = pos->long_name_len;
346 		}
347 
348 		in_kernel = pos->kernel ||
349 				is_kernel_module(name,
350 					PERF_RECORD_MISC_CPUMODE_UNKNOWN);
351 		err = write_buildid(name, name_len, pos->build_id, machine->pid,
352 				    in_kernel ? kmisc : umisc, fd);
353 		if (err)
354 			break;
355 	}
356 
357 	return err;
358 }
359 
360 int perf_session__write_buildid_table(struct perf_session *session,
361 				      struct feat_fd *fd)
362 {
363 	struct rb_node *nd;
364 	int err = machine__write_buildid_table(&session->machines.host, fd);
365 
366 	if (err)
367 		return err;
368 
369 	for (nd = rb_first_cached(&session->machines.guests); nd;
370 	     nd = rb_next(nd)) {
371 		struct machine *pos = rb_entry(nd, struct machine, rb_node);
372 		err = machine__write_buildid_table(pos, fd);
373 		if (err)
374 			break;
375 	}
376 	return err;
377 }
378 
379 static int __dsos__hit_all(struct list_head *head)
380 {
381 	struct dso *pos;
382 
383 	list_for_each_entry(pos, head, node)
384 		pos->hit = true;
385 
386 	return 0;
387 }
388 
389 static int machine__hit_all_dsos(struct machine *machine)
390 {
391 	return __dsos__hit_all(&machine->dsos.head);
392 }
393 
394 int dsos__hit_all(struct perf_session *session)
395 {
396 	struct rb_node *nd;
397 	int err;
398 
399 	err = machine__hit_all_dsos(&session->machines.host);
400 	if (err)
401 		return err;
402 
403 	for (nd = rb_first_cached(&session->machines.guests); nd;
404 	     nd = rb_next(nd)) {
405 		struct machine *pos = rb_entry(nd, struct machine, rb_node);
406 
407 		err = machine__hit_all_dsos(pos);
408 		if (err)
409 			return err;
410 	}
411 
412 	return 0;
413 }
414 
415 void disable_buildid_cache(void)
416 {
417 	no_buildid_cache = true;
418 }
419 
420 static bool lsdir_bid_head_filter(const char *name __maybe_unused,
421 				  struct dirent *d)
422 {
423 	return (strlen(d->d_name) == 2) &&
424 		isxdigit(d->d_name[0]) && isxdigit(d->d_name[1]);
425 }
426 
427 static bool lsdir_bid_tail_filter(const char *name __maybe_unused,
428 				  struct dirent *d)
429 {
430 	int i = 0;
431 	while (isxdigit(d->d_name[i]) && i < SBUILD_ID_SIZE - 3)
432 		i++;
433 	return (i == SBUILD_ID_SIZE - 3) && (d->d_name[i] == '\0');
434 }
435 
436 struct strlist *build_id_cache__list_all(bool validonly)
437 {
438 	struct strlist *toplist, *linklist = NULL, *bidlist;
439 	struct str_node *nd, *nd2;
440 	char *topdir, *linkdir = NULL;
441 	char sbuild_id[SBUILD_ID_SIZE];
442 
443 	/* for filename__ functions */
444 	if (validonly)
445 		symbol__init(NULL);
446 
447 	/* Open the top-level directory */
448 	if (asprintf(&topdir, "%s/.build-id/", buildid_dir) < 0)
449 		return NULL;
450 
451 	bidlist = strlist__new(NULL, NULL);
452 	if (!bidlist)
453 		goto out;
454 
455 	toplist = lsdir(topdir, lsdir_bid_head_filter);
456 	if (!toplist) {
457 		pr_debug("Error in lsdir(%s): %d\n", topdir, errno);
458 		/* If there is no buildid cache, return an empty list */
459 		if (errno == ENOENT)
460 			goto out;
461 		goto err_out;
462 	}
463 
464 	strlist__for_each_entry(nd, toplist) {
465 		if (asprintf(&linkdir, "%s/%s", topdir, nd->s) < 0)
466 			goto err_out;
467 		/* Open the lower-level directory */
468 		linklist = lsdir(linkdir, lsdir_bid_tail_filter);
469 		if (!linklist) {
470 			pr_debug("Error in lsdir(%s): %d\n", linkdir, errno);
471 			goto err_out;
472 		}
473 		strlist__for_each_entry(nd2, linklist) {
474 			if (snprintf(sbuild_id, SBUILD_ID_SIZE, "%s%s",
475 				     nd->s, nd2->s) != SBUILD_ID_SIZE - 1)
476 				goto err_out;
477 			if (validonly && !build_id_cache__valid_id(sbuild_id))
478 				continue;
479 			if (strlist__add(bidlist, sbuild_id) < 0)
480 				goto err_out;
481 		}
482 		strlist__delete(linklist);
483 		zfree(&linkdir);
484 	}
485 
486 out_free:
487 	strlist__delete(toplist);
488 out:
489 	free(topdir);
490 
491 	return bidlist;
492 
493 err_out:
494 	strlist__delete(linklist);
495 	zfree(&linkdir);
496 	strlist__delete(bidlist);
497 	bidlist = NULL;
498 	goto out_free;
499 }
500 
501 static bool str_is_build_id(const char *maybe_sbuild_id, size_t len)
502 {
503 	size_t i;
504 
505 	for (i = 0; i < len; i++) {
506 		if (!isxdigit(maybe_sbuild_id[i]))
507 			return false;
508 	}
509 	return true;
510 }
511 
512 /* Return the valid complete build-id */
513 char *build_id_cache__complement(const char *incomplete_sbuild_id)
514 {
515 	struct strlist *bidlist;
516 	struct str_node *nd, *cand = NULL;
517 	char *sbuild_id = NULL;
518 	size_t len = strlen(incomplete_sbuild_id);
519 
520 	if (len >= SBUILD_ID_SIZE ||
521 	    !str_is_build_id(incomplete_sbuild_id, len))
522 		return NULL;
523 
524 	bidlist = build_id_cache__list_all(true);
525 	if (!bidlist)
526 		return NULL;
527 
528 	strlist__for_each_entry(nd, bidlist) {
529 		if (strncmp(nd->s, incomplete_sbuild_id, len) != 0)
530 			continue;
531 		if (cand) {	/* Error: There are more than 2 candidates. */
532 			cand = NULL;
533 			break;
534 		}
535 		cand = nd;
536 	}
537 	if (cand)
538 		sbuild_id = strdup(cand->s);
539 	strlist__delete(bidlist);
540 
541 	return sbuild_id;
542 }
543 
544 char *build_id_cache__cachedir(const char *sbuild_id, const char *name,
545 			       struct nsinfo *nsi, bool is_kallsyms,
546 			       bool is_vdso)
547 {
548 	char *realname = (char *)name, *filename;
549 	bool slash = is_kallsyms || is_vdso;
550 
551 	if (!slash) {
552 		realname = nsinfo__realpath(name, nsi);
553 		if (!realname)
554 			return NULL;
555 	}
556 
557 	if (asprintf(&filename, "%s%s%s%s%s", buildid_dir, slash ? "/" : "",
558 		     is_vdso ? DSO__NAME_VDSO : realname,
559 		     sbuild_id ? "/" : "", sbuild_id ?: "") < 0)
560 		filename = NULL;
561 
562 	if (!slash)
563 		free(realname);
564 
565 	return filename;
566 }
567 
568 int build_id_cache__list_build_ids(const char *pathname, struct nsinfo *nsi,
569 				   struct strlist **result)
570 {
571 	char *dir_name;
572 	int ret = 0;
573 
574 	dir_name = build_id_cache__cachedir(NULL, pathname, nsi, false, false);
575 	if (!dir_name)
576 		return -ENOMEM;
577 
578 	*result = lsdir(dir_name, lsdir_no_dot_filter);
579 	if (!*result)
580 		ret = -errno;
581 	free(dir_name);
582 
583 	return ret;
584 }
585 
586 #if defined(HAVE_LIBELF_SUPPORT) && defined(HAVE_GELF_GETNOTE_SUPPORT)
587 static int build_id_cache__add_sdt_cache(const char *sbuild_id,
588 					  const char *realname,
589 					  struct nsinfo *nsi)
590 {
591 	struct probe_cache *cache;
592 	int ret;
593 	struct nscookie nsc;
594 
595 	cache = probe_cache__new(sbuild_id, nsi);
596 	if (!cache)
597 		return -1;
598 
599 	nsinfo__mountns_enter(nsi, &nsc);
600 	ret = probe_cache__scan_sdt(cache, realname);
601 	nsinfo__mountns_exit(&nsc);
602 	if (ret >= 0) {
603 		pr_debug4("Found %d SDTs in %s\n", ret, realname);
604 		if (probe_cache__commit(cache) < 0)
605 			ret = -1;
606 	}
607 	probe_cache__delete(cache);
608 	return ret;
609 }
610 #else
611 #define build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) (0)
612 #endif
613 
614 static char *build_id_cache__find_debug(const char *sbuild_id,
615 					struct nsinfo *nsi)
616 {
617 	char *realname = NULL;
618 	char *debugfile;
619 	struct nscookie nsc;
620 	size_t len = 0;
621 
622 	debugfile = calloc(1, PATH_MAX);
623 	if (!debugfile)
624 		goto out;
625 
626 	len = __symbol__join_symfs(debugfile, PATH_MAX,
627 				   "/usr/lib/debug/.build-id/");
628 	snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
629 		 sbuild_id + 2);
630 
631 	nsinfo__mountns_enter(nsi, &nsc);
632 	realname = realpath(debugfile, NULL);
633 	if (realname && access(realname, R_OK))
634 		zfree(&realname);
635 	nsinfo__mountns_exit(&nsc);
636 out:
637 	free(debugfile);
638 	return realname;
639 }
640 
641 int build_id_cache__add_s(const char *sbuild_id, const char *name,
642 			  struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
643 {
644 	const size_t size = PATH_MAX;
645 	char *realname = NULL, *filename = NULL, *dir_name = NULL,
646 	     *linkname = zalloc(size), *tmp;
647 	char *debugfile = NULL;
648 	int err = -1;
649 
650 	if (!is_kallsyms) {
651 		if (!is_vdso)
652 			realname = nsinfo__realpath(name, nsi);
653 		else
654 			realname = realpath(name, NULL);
655 		if (!realname)
656 			goto out_free;
657 	}
658 
659 	dir_name = build_id_cache__cachedir(sbuild_id, name, nsi, is_kallsyms,
660 					    is_vdso);
661 	if (!dir_name)
662 		goto out_free;
663 
664 	/* Remove old style build-id cache */
665 	if (is_regular_file(dir_name))
666 		if (unlink(dir_name))
667 			goto out_free;
668 
669 	if (mkdir_p(dir_name, 0755))
670 		goto out_free;
671 
672 	/* Save the allocated buildid dirname */
673 	if (asprintf(&filename, "%s/%s", dir_name,
674 		     build_id_cache__basename(is_kallsyms, is_vdso,
675 		     false)) < 0) {
676 		filename = NULL;
677 		goto out_free;
678 	}
679 
680 	if (access(filename, F_OK)) {
681 		if (is_kallsyms) {
682 			if (copyfile("/proc/kallsyms", filename))
683 				goto out_free;
684 		} else if (nsi && nsi->need_setns) {
685 			if (copyfile_ns(name, filename, nsi))
686 				goto out_free;
687 		} else if (link(realname, filename) && errno != EEXIST &&
688 				copyfile(name, filename))
689 			goto out_free;
690 	}
691 
692 	/* Some binaries are stripped, but have .debug files with their symbol
693 	 * table.  Check to see if we can locate one of those, since the elf
694 	 * file itself may not be very useful to users of our tools without a
695 	 * symtab.
696 	 */
697 	if (!is_kallsyms && !is_vdso &&
698 	    strncmp(".ko", name + strlen(name) - 3, 3)) {
699 		debugfile = build_id_cache__find_debug(sbuild_id, nsi);
700 		if (debugfile) {
701 			zfree(&filename);
702 			if (asprintf(&filename, "%s/%s", dir_name,
703 			    build_id_cache__basename(false, false, true)) < 0) {
704 				filename = NULL;
705 				goto out_free;
706 			}
707 			if (access(filename, F_OK)) {
708 				if (nsi && nsi->need_setns) {
709 					if (copyfile_ns(debugfile, filename,
710 							nsi))
711 						goto out_free;
712 				} else if (link(debugfile, filename) &&
713 						errno != EEXIST &&
714 						copyfile(debugfile, filename))
715 					goto out_free;
716 			}
717 		}
718 	}
719 
720 	if (!build_id_cache__linkname(sbuild_id, linkname, size))
721 		goto out_free;
722 	tmp = strrchr(linkname, '/');
723 	*tmp = '\0';
724 
725 	if (access(linkname, X_OK) && mkdir_p(linkname, 0755))
726 		goto out_free;
727 
728 	*tmp = '/';
729 	tmp = dir_name + strlen(buildid_dir) - 5;
730 	memcpy(tmp, "../..", 5);
731 
732 	if (symlink(tmp, linkname) == 0)
733 		err = 0;
734 
735 	/* Update SDT cache : error is just warned */
736 	if (realname &&
737 	    build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) < 0)
738 		pr_debug4("Failed to update/scan SDT cache for %s\n", realname);
739 
740 out_free:
741 	if (!is_kallsyms)
742 		free(realname);
743 	free(filename);
744 	free(debugfile);
745 	free(dir_name);
746 	free(linkname);
747 	return err;
748 }
749 
750 static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
751 				 const char *name, struct nsinfo *nsi,
752 				 bool is_kallsyms, bool is_vdso)
753 {
754 	char sbuild_id[SBUILD_ID_SIZE];
755 
756 	build_id__sprintf(build_id, build_id_size, sbuild_id);
757 
758 	return build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
759 				     is_vdso);
760 }
761 
762 bool build_id_cache__cached(const char *sbuild_id)
763 {
764 	bool ret = false;
765 	char *filename = build_id_cache__linkname(sbuild_id, NULL, 0);
766 
767 	if (filename && !access(filename, F_OK))
768 		ret = true;
769 	free(filename);
770 
771 	return ret;
772 }
773 
774 int build_id_cache__remove_s(const char *sbuild_id)
775 {
776 	const size_t size = PATH_MAX;
777 	char *filename = zalloc(size),
778 	     *linkname = zalloc(size), *tmp;
779 	int err = -1;
780 
781 	if (filename == NULL || linkname == NULL)
782 		goto out_free;
783 
784 	if (!build_id_cache__linkname(sbuild_id, linkname, size))
785 		goto out_free;
786 
787 	if (access(linkname, F_OK))
788 		goto out_free;
789 
790 	if (readlink(linkname, filename, size - 1) < 0)
791 		goto out_free;
792 
793 	if (unlink(linkname))
794 		goto out_free;
795 
796 	/*
797 	 * Since the link is relative, we must make it absolute:
798 	 */
799 	tmp = strrchr(linkname, '/') + 1;
800 	snprintf(tmp, size - (tmp - linkname), "%s", filename);
801 
802 	if (rm_rf(linkname))
803 		goto out_free;
804 
805 	err = 0;
806 out_free:
807 	free(filename);
808 	free(linkname);
809 	return err;
810 }
811 
812 static int dso__cache_build_id(struct dso *dso, struct machine *machine)
813 {
814 	bool is_kallsyms = dso__is_kallsyms(dso);
815 	bool is_vdso = dso__is_vdso(dso);
816 	const char *name = dso->long_name;
817 
818 	if (dso__is_kcore(dso)) {
819 		is_kallsyms = true;
820 		name = machine->mmap_name;
821 	}
822 	return build_id_cache__add_b(dso->build_id, sizeof(dso->build_id), name,
823 				     dso->nsinfo, is_kallsyms, is_vdso);
824 }
825 
826 static int __dsos__cache_build_ids(struct list_head *head,
827 				   struct machine *machine)
828 {
829 	struct dso *pos;
830 	int err = 0;
831 
832 	dsos__for_each_with_build_id(pos, head)
833 		if (dso__cache_build_id(pos, machine))
834 			err = -1;
835 
836 	return err;
837 }
838 
839 static int machine__cache_build_ids(struct machine *machine)
840 {
841 	return __dsos__cache_build_ids(&machine->dsos.head, machine);
842 }
843 
844 int perf_session__cache_build_ids(struct perf_session *session)
845 {
846 	struct rb_node *nd;
847 	int ret;
848 
849 	if (no_buildid_cache)
850 		return 0;
851 
852 	if (mkdir(buildid_dir, 0755) != 0 && errno != EEXIST)
853 		return -1;
854 
855 	ret = machine__cache_build_ids(&session->machines.host);
856 
857 	for (nd = rb_first_cached(&session->machines.guests); nd;
858 	     nd = rb_next(nd)) {
859 		struct machine *pos = rb_entry(nd, struct machine, rb_node);
860 		ret |= machine__cache_build_ids(pos);
861 	}
862 	return ret ? -1 : 0;
863 }
864 
865 static bool machine__read_build_ids(struct machine *machine, bool with_hits)
866 {
867 	return __dsos__read_build_ids(&machine->dsos.head, with_hits);
868 }
869 
870 bool perf_session__read_build_ids(struct perf_session *session, bool with_hits)
871 {
872 	struct rb_node *nd;
873 	bool ret = machine__read_build_ids(&session->machines.host, with_hits);
874 
875 	for (nd = rb_first_cached(&session->machines.guests); nd;
876 	     nd = rb_next(nd)) {
877 		struct machine *pos = rb_entry(nd, struct machine, rb_node);
878 		ret |= machine__read_build_ids(pos, with_hits);
879 	}
880 
881 	return ret;
882 }
883