Loading...
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#ifndef REMOTE_UNWIND_LIBUNWIND
29#include <libunwind.h>
30#include <libunwind-ptrace.h>
31#endif
32#include "callchain.h"
33#include "thread.h"
34#include "session.h"
35#include "perf_regs.h"
36#include "unwind.h"
37#include "symbol.h"
38#include "util.h"
39#include "debug.h"
40#include "asm/bug.h"
41#include "dso.h"
42
43extern int
44UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
45 unw_word_t ip,
46 unw_dyn_info_t *di,
47 unw_proc_info_t *pi,
48 int need_unwind_info, void *arg);
49
50#define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
51
52extern int
53UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
54 unw_word_t ip,
55 unw_word_t segbase,
56 const char *obj_name, unw_word_t start,
57 unw_word_t end);
58
59#define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
60
61#define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
62#define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
63
64/* Pointer-encoding formats: */
65#define DW_EH_PE_omit 0xff
66#define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
67#define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
68#define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
69#define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
70#define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
71
72/* Pointer-encoding application: */
73#define DW_EH_PE_absptr 0x00 /* absolute value */
74#define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
75
76/*
77 * The following are not documented by LSB v1.3, yet they are used by
78 * GCC, presumably they aren't documented by LSB since they aren't
79 * used on Linux:
80 */
81#define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
82#define DW_EH_PE_aligned 0x50 /* aligned pointer */
83
84/* Flags intentionaly not handled, since they're not needed:
85 * #define DW_EH_PE_indirect 0x80
86 * #define DW_EH_PE_uleb128 0x01
87 * #define DW_EH_PE_udata2 0x02
88 * #define DW_EH_PE_sleb128 0x09
89 * #define DW_EH_PE_sdata2 0x0a
90 * #define DW_EH_PE_textrel 0x20
91 * #define DW_EH_PE_datarel 0x30
92 */
93
94struct unwind_info {
95 struct perf_sample *sample;
96 struct machine *machine;
97 struct thread *thread;
98};
99
100#define dw_read(ptr, type, end) ({ \
101 type *__p = (type *) ptr; \
102 type __v; \
103 if ((__p + 1) > (type *) end) \
104 return -EINVAL; \
105 __v = *__p++; \
106 ptr = (typeof(ptr)) __p; \
107 __v; \
108 })
109
110static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
111 u8 encoding)
112{
113 u8 *cur = *p;
114 *val = 0;
115
116 switch (encoding) {
117 case DW_EH_PE_omit:
118 *val = 0;
119 goto out;
120 case DW_EH_PE_ptr:
121 *val = dw_read(cur, unsigned long, end);
122 goto out;
123 default:
124 break;
125 }
126
127 switch (encoding & DW_EH_PE_APPL_MASK) {
128 case DW_EH_PE_absptr:
129 break;
130 case DW_EH_PE_pcrel:
131 *val = (unsigned long) cur;
132 break;
133 default:
134 return -EINVAL;
135 }
136
137 if ((encoding & 0x07) == 0x00)
138 encoding |= DW_EH_PE_udata4;
139
140 switch (encoding & DW_EH_PE_FORMAT_MASK) {
141 case DW_EH_PE_sdata4:
142 *val += dw_read(cur, s32, end);
143 break;
144 case DW_EH_PE_udata4:
145 *val += dw_read(cur, u32, end);
146 break;
147 case DW_EH_PE_sdata8:
148 *val += dw_read(cur, s64, end);
149 break;
150 case DW_EH_PE_udata8:
151 *val += dw_read(cur, u64, end);
152 break;
153 default:
154 return -EINVAL;
155 }
156
157 out:
158 *p = cur;
159 return 0;
160}
161
162#define dw_read_encoded_value(ptr, end, enc) ({ \
163 u64 __v; \
164 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
165 return -EINVAL; \
166 } \
167 __v; \
168 })
169
170static u64 elf_section_offset(int fd, const char *name)
171{
172 Elf *elf;
173 GElf_Ehdr ehdr;
174 GElf_Shdr shdr;
175 u64 offset = 0;
176
177 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
178 if (elf == NULL)
179 return 0;
180
181 do {
182 if (gelf_getehdr(elf, &ehdr) == NULL)
183 break;
184
185 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
186 break;
187
188 offset = shdr.sh_offset;
189 } while (0);
190
191 elf_end(elf);
192 return offset;
193}
194
195#ifndef NO_LIBUNWIND_DEBUG_FRAME
196static int elf_is_exec(int fd, const char *name)
197{
198 Elf *elf;
199 GElf_Ehdr ehdr;
200 int retval = 0;
201
202 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
203 if (elf == NULL)
204 return 0;
205 if (gelf_getehdr(elf, &ehdr) == NULL)
206 goto out;
207
208 retval = (ehdr.e_type == ET_EXEC);
209
210out:
211 elf_end(elf);
212 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
213 return retval;
214}
215#endif
216
217struct table_entry {
218 u32 start_ip_offset;
219 u32 fde_offset;
220};
221
222struct eh_frame_hdr {
223 unsigned char version;
224 unsigned char eh_frame_ptr_enc;
225 unsigned char fde_count_enc;
226 unsigned char table_enc;
227
228 /*
229 * The rest of the header is variable-length and consists of the
230 * following members:
231 *
232 * encoded_t eh_frame_ptr;
233 * encoded_t fde_count;
234 */
235
236 /* A single encoded pointer should not be more than 8 bytes. */
237 u64 enc[2];
238
239 /*
240 * struct {
241 * encoded_t start_ip;
242 * encoded_t fde_addr;
243 * } binary_search_table[fde_count];
244 */
245 char data[0];
246} __packed;
247
248static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
249 u64 offset, u64 *table_data, u64 *segbase,
250 u64 *fde_count)
251{
252 struct eh_frame_hdr hdr;
253 u8 *enc = (u8 *) &hdr.enc;
254 u8 *end = (u8 *) &hdr.data;
255 ssize_t r;
256
257 r = dso__data_read_offset(dso, machine, offset,
258 (u8 *) &hdr, sizeof(hdr));
259 if (r != sizeof(hdr))
260 return -EINVAL;
261
262 /* We dont need eh_frame_ptr, just skip it. */
263 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
264
265 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
266 *segbase = offset;
267 *table_data = (enc - (u8 *) &hdr) + offset;
268 return 0;
269}
270
271static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
272 u64 *table_data, u64 *segbase,
273 u64 *fde_count)
274{
275 int ret = -EINVAL, fd;
276 u64 offset = dso->data.eh_frame_hdr_offset;
277
278 if (offset == 0) {
279 fd = dso__data_get_fd(dso, machine);
280 if (fd < 0)
281 return -EINVAL;
282
283 /* Check the .eh_frame section for unwinding info */
284 offset = elf_section_offset(fd, ".eh_frame_hdr");
285 dso->data.eh_frame_hdr_offset = offset;
286 dso__data_put_fd(dso);
287 }
288
289 if (offset)
290 ret = unwind_spec_ehframe(dso, machine, offset,
291 table_data, segbase,
292 fde_count);
293
294 return ret;
295}
296
297#ifndef NO_LIBUNWIND_DEBUG_FRAME
298static int read_unwind_spec_debug_frame(struct dso *dso,
299 struct machine *machine, u64 *offset)
300{
301 int fd;
302 u64 ofs = dso->data.debug_frame_offset;
303
304 /* debug_frame can reside in:
305 * - dso
306 * - debug pointed by symsrc_filename
307 * - gnu_debuglink, which doesn't necessary
308 * has to be pointed by symsrc_filename
309 */
310 if (ofs == 0) {
311 fd = dso__data_get_fd(dso, machine);
312 if (fd >= 0) {
313 ofs = elf_section_offset(fd, ".debug_frame");
314 dso__data_put_fd(dso);
315 }
316
317 if (ofs <= 0) {
318 fd = open(dso->symsrc_filename, O_RDONLY);
319 if (fd >= 0) {
320 ofs = elf_section_offset(fd, ".debug_frame");
321 close(fd);
322 }
323 }
324
325 if (ofs <= 0) {
326 char *debuglink = malloc(PATH_MAX);
327 int ret = 0;
328
329 ret = dso__read_binary_type_filename(
330 dso, DSO_BINARY_TYPE__DEBUGLINK,
331 machine->root_dir, debuglink, PATH_MAX);
332 if (!ret) {
333 fd = open(debuglink, O_RDONLY);
334 if (fd >= 0) {
335 ofs = elf_section_offset(fd,
336 ".debug_frame");
337 close(fd);
338 }
339 }
340 if (ofs > 0) {
341 if (dso->symsrc_filename != NULL) {
342 pr_warning(
343 "%s: overwrite symsrc(%s,%s)\n",
344 __func__,
345 dso->symsrc_filename,
346 debuglink);
347 free(dso->symsrc_filename);
348 }
349 dso->symsrc_filename = debuglink;
350 } else {
351 free(debuglink);
352 }
353 }
354
355 dso->data.debug_frame_offset = ofs;
356 }
357
358 *offset = ofs;
359 if (*offset)
360 return 0;
361
362 return -EINVAL;
363}
364#endif
365
366static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
367{
368 struct addr_location al;
369
370 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
371 MAP__FUNCTION, ip, &al);
372 if (!al.map) {
373 /*
374 * We've seen cases (softice) where DWARF unwinder went
375 * through non executable mmaps, which we need to lookup
376 * in MAP__VARIABLE tree.
377 */
378 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
379 MAP__VARIABLE, ip, &al);
380 }
381 return al.map;
382}
383
384static int
385find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
386 int need_unwind_info, void *arg)
387{
388 struct unwind_info *ui = arg;
389 struct map *map;
390 unw_dyn_info_t di;
391 u64 table_data, segbase, fde_count;
392 int ret = -EINVAL;
393
394 map = find_map(ip, ui);
395 if (!map || !map->dso)
396 return -EINVAL;
397
398 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
399
400 /* Check the .eh_frame section for unwinding info */
401 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
402 &table_data, &segbase, &fde_count)) {
403 memset(&di, 0, sizeof(di));
404 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
405 di.start_ip = map->start;
406 di.end_ip = map->end;
407 di.u.rti.segbase = map->start + segbase - map->pgoff;
408 di.u.rti.table_data = map->start + table_data - map->pgoff;
409 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
410 / sizeof(unw_word_t);
411 ret = dwarf_search_unwind_table(as, ip, &di, pi,
412 need_unwind_info, arg);
413 }
414
415#ifndef NO_LIBUNWIND_DEBUG_FRAME
416 /* Check the .debug_frame section for unwinding info */
417 if (ret < 0 &&
418 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
419 int fd = dso__data_get_fd(map->dso, ui->machine);
420 int is_exec = elf_is_exec(fd, map->dso->name);
421 unw_word_t base = is_exec ? 0 : map->start;
422 const char *symfile;
423
424 if (fd >= 0)
425 dso__data_put_fd(map->dso);
426
427 symfile = map->dso->symsrc_filename ?: map->dso->name;
428
429 memset(&di, 0, sizeof(di));
430 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
431 map->start, map->end))
432 return dwarf_search_unwind_table(as, ip, &di, pi,
433 need_unwind_info, arg);
434 }
435#endif
436
437 return ret;
438}
439
440static int access_fpreg(unw_addr_space_t __maybe_unused as,
441 unw_regnum_t __maybe_unused num,
442 unw_fpreg_t __maybe_unused *val,
443 int __maybe_unused __write,
444 void __maybe_unused *arg)
445{
446 pr_err("unwind: access_fpreg unsupported\n");
447 return -UNW_EINVAL;
448}
449
450static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
451 unw_word_t __maybe_unused *dil_addr,
452 void __maybe_unused *arg)
453{
454 return -UNW_ENOINFO;
455}
456
457static int resume(unw_addr_space_t __maybe_unused as,
458 unw_cursor_t __maybe_unused *cu,
459 void __maybe_unused *arg)
460{
461 pr_err("unwind: resume unsupported\n");
462 return -UNW_EINVAL;
463}
464
465static int
466get_proc_name(unw_addr_space_t __maybe_unused as,
467 unw_word_t __maybe_unused addr,
468 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
469 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
470{
471 pr_err("unwind: get_proc_name unsupported\n");
472 return -UNW_EINVAL;
473}
474
475static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
476 unw_word_t *data)
477{
478 struct map *map;
479 ssize_t size;
480
481 map = find_map(addr, ui);
482 if (!map) {
483 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
484 return -1;
485 }
486
487 if (!map->dso)
488 return -1;
489
490 size = dso__data_read_addr(map->dso, map, ui->machine,
491 addr, (u8 *) data, sizeof(*data));
492
493 return !(size == sizeof(*data));
494}
495
496static int access_mem(unw_addr_space_t __maybe_unused as,
497 unw_word_t addr, unw_word_t *valp,
498 int __write, void *arg)
499{
500 struct unwind_info *ui = arg;
501 struct stack_dump *stack = &ui->sample->user_stack;
502 u64 start, end;
503 int offset;
504 int ret;
505
506 /* Don't support write, probably not needed. */
507 if (__write || !stack || !ui->sample->user_regs.regs) {
508 *valp = 0;
509 return 0;
510 }
511
512 ret = perf_reg_value(&start, &ui->sample->user_regs,
513 LIBUNWIND__ARCH_REG_SP);
514 if (ret)
515 return ret;
516
517 end = start + stack->size;
518
519 /* Check overflow. */
520 if (addr + sizeof(unw_word_t) < addr)
521 return -EINVAL;
522
523 if (addr < start || addr + sizeof(unw_word_t) >= end) {
524 ret = access_dso_mem(ui, addr, valp);
525 if (ret) {
526 pr_debug("unwind: access_mem %p not inside range"
527 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
528 (void *) (uintptr_t) addr, start, end);
529 *valp = 0;
530 return ret;
531 }
532 return 0;
533 }
534
535 offset = addr - start;
536 *valp = *(unw_word_t *)&stack->data[offset];
537 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
538 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
539 return 0;
540}
541
542static int access_reg(unw_addr_space_t __maybe_unused as,
543 unw_regnum_t regnum, unw_word_t *valp,
544 int __write, void *arg)
545{
546 struct unwind_info *ui = arg;
547 int id, ret;
548 u64 val;
549
550 /* Don't support write, I suspect we don't need it. */
551 if (__write) {
552 pr_err("unwind: access_reg w %d\n", regnum);
553 return 0;
554 }
555
556 if (!ui->sample->user_regs.regs) {
557 *valp = 0;
558 return 0;
559 }
560
561 id = LIBUNWIND__ARCH_REG_ID(regnum);
562 if (id < 0)
563 return -EINVAL;
564
565 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
566 if (ret) {
567 pr_err("unwind: can't read reg %d\n", regnum);
568 return ret;
569 }
570
571 *valp = (unw_word_t) val;
572 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
573 return 0;
574}
575
576static void put_unwind_info(unw_addr_space_t __maybe_unused as,
577 unw_proc_info_t *pi __maybe_unused,
578 void *arg __maybe_unused)
579{
580 pr_debug("unwind: put_unwind_info called\n");
581}
582
583static int entry(u64 ip, struct thread *thread,
584 unwind_entry_cb_t cb, void *arg)
585{
586 struct unwind_entry e;
587 struct addr_location al;
588
589 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
590 MAP__FUNCTION, ip, &al);
591
592 e.ip = al.addr;
593 e.map = al.map;
594 e.sym = al.sym;
595
596 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
597 al.sym ? al.sym->name : "''",
598 ip,
599 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
600
601 return cb(&e, arg);
602}
603
604static void display_error(int err)
605{
606 switch (err) {
607 case UNW_EINVAL:
608 pr_err("unwind: Only supports local.\n");
609 break;
610 case UNW_EUNSPEC:
611 pr_err("unwind: Unspecified error.\n");
612 break;
613 case UNW_EBADREG:
614 pr_err("unwind: Register unavailable.\n");
615 break;
616 default:
617 break;
618 }
619}
620
621static unw_accessors_t accessors = {
622 .find_proc_info = find_proc_info,
623 .put_unwind_info = put_unwind_info,
624 .get_dyn_info_list_addr = get_dyn_info_list_addr,
625 .access_mem = access_mem,
626 .access_reg = access_reg,
627 .access_fpreg = access_fpreg,
628 .resume = resume,
629 .get_proc_name = get_proc_name,
630};
631
632static int _unwind__prepare_access(struct thread *thread)
633{
634 if (!dwarf_callchain_users)
635 return 0;
636 thread->addr_space = unw_create_addr_space(&accessors, 0);
637 if (!thread->addr_space) {
638 pr_err("unwind: Can't create unwind address space.\n");
639 return -ENOMEM;
640 }
641
642 unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
643 return 0;
644}
645
646static void _unwind__flush_access(struct thread *thread)
647{
648 if (!dwarf_callchain_users)
649 return;
650 unw_flush_cache(thread->addr_space, 0, 0);
651}
652
653static void _unwind__finish_access(struct thread *thread)
654{
655 if (!dwarf_callchain_users)
656 return;
657 unw_destroy_addr_space(thread->addr_space);
658}
659
660static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
661 void *arg, int max_stack)
662{
663 u64 val;
664 unw_word_t ips[max_stack];
665 unw_addr_space_t addr_space;
666 unw_cursor_t c;
667 int ret, i = 0;
668
669 ret = perf_reg_value(&val, &ui->sample->user_regs,
670 LIBUNWIND__ARCH_REG_IP);
671 if (ret)
672 return ret;
673
674 ips[i++] = (unw_word_t) val;
675
676 /*
677 * If we need more than one entry, do the DWARF
678 * unwind itself.
679 */
680 if (max_stack - 1 > 0) {
681 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
682 addr_space = ui->thread->addr_space;
683
684 if (addr_space == NULL)
685 return -1;
686
687 ret = unw_init_remote(&c, addr_space, ui);
688 if (ret)
689 display_error(ret);
690
691 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
692 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
693
694 /*
695 * Decrement the IP for any non-activation frames.
696 * this is required to properly find the srcline
697 * for caller frames.
698 * See also the documentation for dwfl_frame_pc(),
699 * which this code tries to replicate.
700 */
701 if (unw_is_signal_frame(&c) <= 0)
702 --ips[i];
703
704 ++i;
705 }
706
707 max_stack = i;
708 }
709
710 /*
711 * Display what we got based on the order setup.
712 */
713 for (i = 0; i < max_stack && !ret; i++) {
714 int j = i;
715
716 if (callchain_param.order == ORDER_CALLER)
717 j = max_stack - i - 1;
718 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
719 }
720
721 return ret;
722}
723
724static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
725 struct thread *thread,
726 struct perf_sample *data, int max_stack)
727{
728 struct unwind_info ui = {
729 .sample = data,
730 .thread = thread,
731 .machine = thread->mg->machine,
732 };
733
734 if (!data->user_regs.regs)
735 return -EINVAL;
736
737 if (max_stack <= 0)
738 return -EINVAL;
739
740 return get_entries(&ui, cb, arg, max_stack);
741}
742
743static struct unwind_libunwind_ops
744_unwind_libunwind_ops = {
745 .prepare_access = _unwind__prepare_access,
746 .flush_access = _unwind__flush_access,
747 .finish_access = _unwind__finish_access,
748 .get_entries = _unwind__get_entries,
749};
750
751#ifndef REMOTE_UNWIND_LIBUNWIND
752struct unwind_libunwind_ops *
753local_unwind_libunwind_ops = &_unwind_libunwind_ops;
754#endif
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 intentionaly 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};
100
101#define dw_read(ptr, type, end) ({ \
102 type *__p = (type *) ptr; \
103 type __v; \
104 if ((__p + 1) > (type *) end) \
105 return -EINVAL; \
106 __v = *__p++; \
107 ptr = (typeof(ptr)) __p; \
108 __v; \
109 })
110
111static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
112 u8 encoding)
113{
114 u8 *cur = *p;
115 *val = 0;
116
117 switch (encoding) {
118 case DW_EH_PE_omit:
119 *val = 0;
120 goto out;
121 case DW_EH_PE_ptr:
122 *val = dw_read(cur, unsigned long, end);
123 goto out;
124 default:
125 break;
126 }
127
128 switch (encoding & DW_EH_PE_APPL_MASK) {
129 case DW_EH_PE_absptr:
130 break;
131 case DW_EH_PE_pcrel:
132 *val = (unsigned long) cur;
133 break;
134 default:
135 return -EINVAL;
136 }
137
138 if ((encoding & 0x07) == 0x00)
139 encoding |= DW_EH_PE_udata4;
140
141 switch (encoding & DW_EH_PE_FORMAT_MASK) {
142 case DW_EH_PE_sdata4:
143 *val += dw_read(cur, s32, end);
144 break;
145 case DW_EH_PE_udata4:
146 *val += dw_read(cur, u32, end);
147 break;
148 case DW_EH_PE_sdata8:
149 *val += dw_read(cur, s64, end);
150 break;
151 case DW_EH_PE_udata8:
152 *val += dw_read(cur, u64, end);
153 break;
154 default:
155 return -EINVAL;
156 }
157
158 out:
159 *p = cur;
160 return 0;
161}
162
163#define dw_read_encoded_value(ptr, end, enc) ({ \
164 u64 __v; \
165 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
166 return -EINVAL; \
167 } \
168 __v; \
169 })
170
171static u64 elf_section_offset(int fd, const char *name)
172{
173 Elf *elf;
174 GElf_Ehdr ehdr;
175 GElf_Shdr shdr;
176 u64 offset = 0;
177
178 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
179 if (elf == NULL)
180 return 0;
181
182 do {
183 if (gelf_getehdr(elf, &ehdr) == NULL)
184 break;
185
186 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
187 break;
188
189 offset = shdr.sh_offset;
190 } while (0);
191
192 elf_end(elf);
193 return offset;
194}
195
196#ifndef NO_LIBUNWIND_DEBUG_FRAME
197static int elf_is_exec(int fd, const char *name)
198{
199 Elf *elf;
200 GElf_Ehdr ehdr;
201 int retval = 0;
202
203 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
204 if (elf == NULL)
205 return 0;
206 if (gelf_getehdr(elf, &ehdr) == NULL)
207 goto out;
208
209 retval = (ehdr.e_type == ET_EXEC);
210
211out:
212 elf_end(elf);
213 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
214 return retval;
215}
216#endif
217
218struct table_entry {
219 u32 start_ip_offset;
220 u32 fde_offset;
221};
222
223struct eh_frame_hdr {
224 unsigned char version;
225 unsigned char eh_frame_ptr_enc;
226 unsigned char fde_count_enc;
227 unsigned char table_enc;
228
229 /*
230 * The rest of the header is variable-length and consists of the
231 * following members:
232 *
233 * encoded_t eh_frame_ptr;
234 * encoded_t fde_count;
235 */
236
237 /* A single encoded pointer should not be more than 8 bytes. */
238 u64 enc[2];
239
240 /*
241 * struct {
242 * encoded_t start_ip;
243 * encoded_t fde_addr;
244 * } binary_search_table[fde_count];
245 */
246 char data[0];
247} __packed;
248
249static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
250 u64 offset, u64 *table_data, u64 *segbase,
251 u64 *fde_count)
252{
253 struct eh_frame_hdr hdr;
254 u8 *enc = (u8 *) &hdr.enc;
255 u8 *end = (u8 *) &hdr.data;
256 ssize_t r;
257
258 r = dso__data_read_offset(dso, machine, offset,
259 (u8 *) &hdr, sizeof(hdr));
260 if (r != sizeof(hdr))
261 return -EINVAL;
262
263 /* We dont need eh_frame_ptr, just skip it. */
264 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
265
266 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
267 *segbase = offset;
268 *table_data = (enc - (u8 *) &hdr) + offset;
269 return 0;
270}
271
272static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
273 u64 *table_data, u64 *segbase,
274 u64 *fde_count)
275{
276 int ret = -EINVAL, fd;
277 u64 offset = dso->data.eh_frame_hdr_offset;
278
279 if (offset == 0) {
280 fd = dso__data_get_fd(dso, machine);
281 if (fd < 0)
282 return -EINVAL;
283
284 /* Check the .eh_frame section for unwinding info */
285 offset = elf_section_offset(fd, ".eh_frame_hdr");
286 dso->data.eh_frame_hdr_offset = offset;
287 dso__data_put_fd(dso);
288 }
289
290 if (offset)
291 ret = unwind_spec_ehframe(dso, machine, offset,
292 table_data, segbase,
293 fde_count);
294
295 return ret;
296}
297
298#ifndef NO_LIBUNWIND_DEBUG_FRAME
299static int read_unwind_spec_debug_frame(struct dso *dso,
300 struct machine *machine, u64 *offset)
301{
302 int fd;
303 u64 ofs = dso->data.debug_frame_offset;
304
305 /* debug_frame can reside in:
306 * - dso
307 * - debug pointed by symsrc_filename
308 * - gnu_debuglink, which doesn't necessary
309 * has to be pointed by symsrc_filename
310 */
311 if (ofs == 0) {
312 fd = dso__data_get_fd(dso, machine);
313 if (fd >= 0) {
314 ofs = elf_section_offset(fd, ".debug_frame");
315 dso__data_put_fd(dso);
316 }
317
318 if (ofs <= 0) {
319 fd = open(dso->symsrc_filename, O_RDONLY);
320 if (fd >= 0) {
321 ofs = elf_section_offset(fd, ".debug_frame");
322 close(fd);
323 }
324 }
325
326 if (ofs <= 0) {
327 char *debuglink = malloc(PATH_MAX);
328 int ret = 0;
329
330 ret = dso__read_binary_type_filename(
331 dso, DSO_BINARY_TYPE__DEBUGLINK,
332 machine->root_dir, debuglink, PATH_MAX);
333 if (!ret) {
334 fd = open(debuglink, O_RDONLY);
335 if (fd >= 0) {
336 ofs = elf_section_offset(fd,
337 ".debug_frame");
338 close(fd);
339 }
340 }
341 if (ofs > 0) {
342 if (dso->symsrc_filename != NULL) {
343 pr_warning(
344 "%s: overwrite symsrc(%s,%s)\n",
345 __func__,
346 dso->symsrc_filename,
347 debuglink);
348 zfree(&dso->symsrc_filename);
349 }
350 dso->symsrc_filename = debuglink;
351 } else {
352 free(debuglink);
353 }
354 }
355
356 dso->data.debug_frame_offset = ofs;
357 }
358
359 *offset = ofs;
360 if (*offset)
361 return 0;
362
363 return -EINVAL;
364}
365#endif
366
367static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
368{
369 struct addr_location al;
370 return thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
371}
372
373static int
374find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
375 int need_unwind_info, void *arg)
376{
377 struct unwind_info *ui = arg;
378 struct map *map;
379 unw_dyn_info_t di;
380 u64 table_data, segbase, fde_count;
381 int ret = -EINVAL;
382
383 map = find_map(ip, ui);
384 if (!map || !map->dso)
385 return -EINVAL;
386
387 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
388
389 /* Check the .eh_frame section for unwinding info */
390 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
391 &table_data, &segbase, &fde_count)) {
392 memset(&di, 0, sizeof(di));
393 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
394 di.start_ip = map->start;
395 di.end_ip = map->end;
396 di.u.rti.segbase = map->start + segbase - map->pgoff;
397 di.u.rti.table_data = map->start + table_data - map->pgoff;
398 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
399 / sizeof(unw_word_t);
400 ret = dwarf_search_unwind_table(as, ip, &di, pi,
401 need_unwind_info, arg);
402 }
403
404#ifndef NO_LIBUNWIND_DEBUG_FRAME
405 /* Check the .debug_frame section for unwinding info */
406 if (ret < 0 &&
407 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
408 int fd = dso__data_get_fd(map->dso, ui->machine);
409 int is_exec = elf_is_exec(fd, map->dso->name);
410 unw_word_t base = is_exec ? 0 : map->start;
411 const char *symfile;
412
413 if (fd >= 0)
414 dso__data_put_fd(map->dso);
415
416 symfile = map->dso->symsrc_filename ?: map->dso->name;
417
418 memset(&di, 0, sizeof(di));
419 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
420 map->start, map->end))
421 return dwarf_search_unwind_table(as, ip, &di, pi,
422 need_unwind_info, arg);
423 }
424#endif
425
426 return ret;
427}
428
429static int access_fpreg(unw_addr_space_t __maybe_unused as,
430 unw_regnum_t __maybe_unused num,
431 unw_fpreg_t __maybe_unused *val,
432 int __maybe_unused __write,
433 void __maybe_unused *arg)
434{
435 pr_err("unwind: access_fpreg unsupported\n");
436 return -UNW_EINVAL;
437}
438
439static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
440 unw_word_t __maybe_unused *dil_addr,
441 void __maybe_unused *arg)
442{
443 return -UNW_ENOINFO;
444}
445
446static int resume(unw_addr_space_t __maybe_unused as,
447 unw_cursor_t __maybe_unused *cu,
448 void __maybe_unused *arg)
449{
450 pr_err("unwind: resume unsupported\n");
451 return -UNW_EINVAL;
452}
453
454static int
455get_proc_name(unw_addr_space_t __maybe_unused as,
456 unw_word_t __maybe_unused addr,
457 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
458 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
459{
460 pr_err("unwind: get_proc_name unsupported\n");
461 return -UNW_EINVAL;
462}
463
464static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
465 unw_word_t *data)
466{
467 struct map *map;
468 ssize_t size;
469
470 map = find_map(addr, ui);
471 if (!map) {
472 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
473 return -1;
474 }
475
476 if (!map->dso)
477 return -1;
478
479 size = dso__data_read_addr(map->dso, map, ui->machine,
480 addr, (u8 *) data, sizeof(*data));
481
482 return !(size == sizeof(*data));
483}
484
485static int access_mem(unw_addr_space_t __maybe_unused as,
486 unw_word_t addr, unw_word_t *valp,
487 int __write, void *arg)
488{
489 struct unwind_info *ui = arg;
490 struct stack_dump *stack = &ui->sample->user_stack;
491 u64 start, end;
492 int offset;
493 int ret;
494
495 /* Don't support write, probably not needed. */
496 if (__write || !stack || !ui->sample->user_regs.regs) {
497 *valp = 0;
498 return 0;
499 }
500
501 ret = perf_reg_value(&start, &ui->sample->user_regs,
502 LIBUNWIND__ARCH_REG_SP);
503 if (ret)
504 return ret;
505
506 end = start + stack->size;
507
508 /* Check overflow. */
509 if (addr + sizeof(unw_word_t) < addr)
510 return -EINVAL;
511
512 if (addr < start || addr + sizeof(unw_word_t) >= end) {
513 ret = access_dso_mem(ui, addr, valp);
514 if (ret) {
515 pr_debug("unwind: access_mem %p not inside range"
516 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
517 (void *) (uintptr_t) addr, start, end);
518 *valp = 0;
519 return ret;
520 }
521 return 0;
522 }
523
524 offset = addr - start;
525 *valp = *(unw_word_t *)&stack->data[offset];
526 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
527 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
528 return 0;
529}
530
531static int access_reg(unw_addr_space_t __maybe_unused as,
532 unw_regnum_t regnum, unw_word_t *valp,
533 int __write, void *arg)
534{
535 struct unwind_info *ui = arg;
536 int id, ret;
537 u64 val;
538
539 /* Don't support write, I suspect we don't need it. */
540 if (__write) {
541 pr_err("unwind: access_reg w %d\n", regnum);
542 return 0;
543 }
544
545 if (!ui->sample->user_regs.regs) {
546 *valp = 0;
547 return 0;
548 }
549
550 id = LIBUNWIND__ARCH_REG_ID(regnum);
551 if (id < 0)
552 return -EINVAL;
553
554 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
555 if (ret) {
556 pr_err("unwind: can't read reg %d\n", regnum);
557 return ret;
558 }
559
560 *valp = (unw_word_t) val;
561 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
562 return 0;
563}
564
565static void put_unwind_info(unw_addr_space_t __maybe_unused as,
566 unw_proc_info_t *pi __maybe_unused,
567 void *arg __maybe_unused)
568{
569 pr_debug("unwind: put_unwind_info called\n");
570}
571
572static int entry(u64 ip, struct thread *thread,
573 unwind_entry_cb_t cb, void *arg)
574{
575 struct unwind_entry e;
576 struct addr_location al;
577
578 e.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
579 e.ip = ip;
580 e.map = al.map;
581
582 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
583 al.sym ? al.sym->name : "''",
584 ip,
585 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
586
587 return cb(&e, arg);
588}
589
590static void display_error(int err)
591{
592 switch (err) {
593 case UNW_EINVAL:
594 pr_err("unwind: Only supports local.\n");
595 break;
596 case UNW_EUNSPEC:
597 pr_err("unwind: Unspecified error.\n");
598 break;
599 case UNW_EBADREG:
600 pr_err("unwind: Register unavailable.\n");
601 break;
602 default:
603 break;
604 }
605}
606
607static unw_accessors_t accessors = {
608 .find_proc_info = find_proc_info,
609 .put_unwind_info = put_unwind_info,
610 .get_dyn_info_list_addr = get_dyn_info_list_addr,
611 .access_mem = access_mem,
612 .access_reg = access_reg,
613 .access_fpreg = access_fpreg,
614 .resume = resume,
615 .get_proc_name = get_proc_name,
616};
617
618static int _unwind__prepare_access(struct map_groups *mg)
619{
620 mg->addr_space = unw_create_addr_space(&accessors, 0);
621 if (!mg->addr_space) {
622 pr_err("unwind: Can't create unwind address space.\n");
623 return -ENOMEM;
624 }
625
626 unw_set_caching_policy(mg->addr_space, UNW_CACHE_GLOBAL);
627 return 0;
628}
629
630static void _unwind__flush_access(struct map_groups *mg)
631{
632 unw_flush_cache(mg->addr_space, 0, 0);
633}
634
635static void _unwind__finish_access(struct map_groups *mg)
636{
637 unw_destroy_addr_space(mg->addr_space);
638}
639
640static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
641 void *arg, int max_stack)
642{
643 u64 val;
644 unw_word_t ips[max_stack];
645 unw_addr_space_t addr_space;
646 unw_cursor_t c;
647 int ret, i = 0;
648
649 ret = perf_reg_value(&val, &ui->sample->user_regs,
650 LIBUNWIND__ARCH_REG_IP);
651 if (ret)
652 return ret;
653
654 ips[i++] = (unw_word_t) val;
655
656 /*
657 * If we need more than one entry, do the DWARF
658 * unwind itself.
659 */
660 if (max_stack - 1 > 0) {
661 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
662 addr_space = ui->thread->mg->addr_space;
663
664 if (addr_space == NULL)
665 return -1;
666
667 ret = unw_init_remote(&c, addr_space, ui);
668 if (ret)
669 display_error(ret);
670
671 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
672 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
673
674 /*
675 * Decrement the IP for any non-activation frames.
676 * this is required to properly find the srcline
677 * for caller frames.
678 * See also the documentation for dwfl_frame_pc(),
679 * which this code tries to replicate.
680 */
681 if (unw_is_signal_frame(&c) <= 0)
682 --ips[i];
683
684 ++i;
685 }
686
687 max_stack = i;
688 }
689
690 /*
691 * Display what we got based on the order setup.
692 */
693 for (i = 0; i < max_stack && !ret; i++) {
694 int j = i;
695
696 if (callchain_param.order == ORDER_CALLER)
697 j = max_stack - i - 1;
698 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
699 }
700
701 return ret;
702}
703
704static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
705 struct thread *thread,
706 struct perf_sample *data, int max_stack)
707{
708 struct unwind_info ui = {
709 .sample = data,
710 .thread = thread,
711 .machine = thread->mg->machine,
712 };
713
714 if (!data->user_regs.regs)
715 return -EINVAL;
716
717 if (max_stack <= 0)
718 return -EINVAL;
719
720 return get_entries(&ui, cb, arg, max_stack);
721}
722
723static struct unwind_libunwind_ops
724_unwind_libunwind_ops = {
725 .prepare_access = _unwind__prepare_access,
726 .flush_access = _unwind__flush_access,
727 .finish_access = _unwind__finish_access,
728 .get_entries = _unwind__get_entries,
729};
730
731#ifndef REMOTE_UNWIND_LIBUNWIND
732struct unwind_libunwind_ops *
733local_unwind_libunwind_ops = &_unwind_libunwind_ops;
734#endif