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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 "thread.h"
28#include "session.h"
29#include "perf_regs.h"
30#include "unwind.h"
31#include "symbol.h"
32#include "util.h"
33
34extern int
35UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
36 unw_word_t ip,
37 unw_dyn_info_t *di,
38 unw_proc_info_t *pi,
39 int need_unwind_info, void *arg);
40
41#define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
42
43extern int
44UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
45 unw_word_t ip,
46 unw_word_t segbase,
47 const char *obj_name, unw_word_t start,
48 unw_word_t end);
49
50#define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
51
52#define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
53#define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
54
55/* Pointer-encoding formats: */
56#define DW_EH_PE_omit 0xff
57#define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
58#define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
59#define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
60#define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
61#define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
62
63/* Pointer-encoding application: */
64#define DW_EH_PE_absptr 0x00 /* absolute value */
65#define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
66
67/*
68 * The following are not documented by LSB v1.3, yet they are used by
69 * GCC, presumably they aren't documented by LSB since they aren't
70 * used on Linux:
71 */
72#define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
73#define DW_EH_PE_aligned 0x50 /* aligned pointer */
74
75/* Flags intentionaly not handled, since they're not needed:
76 * #define DW_EH_PE_indirect 0x80
77 * #define DW_EH_PE_uleb128 0x01
78 * #define DW_EH_PE_udata2 0x02
79 * #define DW_EH_PE_sleb128 0x09
80 * #define DW_EH_PE_sdata2 0x0a
81 * #define DW_EH_PE_textrel 0x20
82 * #define DW_EH_PE_datarel 0x30
83 */
84
85struct unwind_info {
86 struct perf_sample *sample;
87 struct machine *machine;
88 struct thread *thread;
89};
90
91#define dw_read(ptr, type, end) ({ \
92 type *__p = (type *) ptr; \
93 type __v; \
94 if ((__p + 1) > (type *) end) \
95 return -EINVAL; \
96 __v = *__p++; \
97 ptr = (typeof(ptr)) __p; \
98 __v; \
99 })
100
101static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
102 u8 encoding)
103{
104 u8 *cur = *p;
105 *val = 0;
106
107 switch (encoding) {
108 case DW_EH_PE_omit:
109 *val = 0;
110 goto out;
111 case DW_EH_PE_ptr:
112 *val = dw_read(cur, unsigned long, end);
113 goto out;
114 default:
115 break;
116 }
117
118 switch (encoding & DW_EH_PE_APPL_MASK) {
119 case DW_EH_PE_absptr:
120 break;
121 case DW_EH_PE_pcrel:
122 *val = (unsigned long) cur;
123 break;
124 default:
125 return -EINVAL;
126 }
127
128 if ((encoding & 0x07) == 0x00)
129 encoding |= DW_EH_PE_udata4;
130
131 switch (encoding & DW_EH_PE_FORMAT_MASK) {
132 case DW_EH_PE_sdata4:
133 *val += dw_read(cur, s32, end);
134 break;
135 case DW_EH_PE_udata4:
136 *val += dw_read(cur, u32, end);
137 break;
138 case DW_EH_PE_sdata8:
139 *val += dw_read(cur, s64, end);
140 break;
141 case DW_EH_PE_udata8:
142 *val += dw_read(cur, u64, end);
143 break;
144 default:
145 return -EINVAL;
146 }
147
148 out:
149 *p = cur;
150 return 0;
151}
152
153#define dw_read_encoded_value(ptr, end, enc) ({ \
154 u64 __v; \
155 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
156 return -EINVAL; \
157 } \
158 __v; \
159 })
160
161static u64 elf_section_offset(int fd, const char *name)
162{
163 Elf *elf;
164 GElf_Ehdr ehdr;
165 GElf_Shdr shdr;
166 u64 offset = 0;
167
168 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
169 if (elf == NULL)
170 return 0;
171
172 do {
173 if (gelf_getehdr(elf, &ehdr) == NULL)
174 break;
175
176 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
177 break;
178
179 offset = shdr.sh_offset;
180 } while (0);
181
182 elf_end(elf);
183 return offset;
184}
185
186struct table_entry {
187 u32 start_ip_offset;
188 u32 fde_offset;
189};
190
191struct eh_frame_hdr {
192 unsigned char version;
193 unsigned char eh_frame_ptr_enc;
194 unsigned char fde_count_enc;
195 unsigned char table_enc;
196
197 /*
198 * The rest of the header is variable-length and consists of the
199 * following members:
200 *
201 * encoded_t eh_frame_ptr;
202 * encoded_t fde_count;
203 */
204
205 /* A single encoded pointer should not be more than 8 bytes. */
206 u64 enc[2];
207
208 /*
209 * struct {
210 * encoded_t start_ip;
211 * encoded_t fde_addr;
212 * } binary_search_table[fde_count];
213 */
214 char data[0];
215} __packed;
216
217static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
218 u64 offset, u64 *table_data, u64 *segbase,
219 u64 *fde_count)
220{
221 struct eh_frame_hdr hdr;
222 u8 *enc = (u8 *) &hdr.enc;
223 u8 *end = (u8 *) &hdr.data;
224 ssize_t r;
225
226 r = dso__data_read_offset(dso, machine, offset,
227 (u8 *) &hdr, sizeof(hdr));
228 if (r != sizeof(hdr))
229 return -EINVAL;
230
231 /* We dont need eh_frame_ptr, just skip it. */
232 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
233
234 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
235 *segbase = offset;
236 *table_data = (enc - (u8 *) &hdr) + offset;
237 return 0;
238}
239
240static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
241 u64 *table_data, u64 *segbase,
242 u64 *fde_count)
243{
244 int ret = -EINVAL, fd;
245 u64 offset;
246
247 fd = dso__data_fd(dso, machine);
248 if (fd < 0)
249 return -EINVAL;
250
251 /* Check the .eh_frame section for unwinding info */
252 offset = elf_section_offset(fd, ".eh_frame_hdr");
253 close(fd);
254
255 if (offset)
256 ret = unwind_spec_ehframe(dso, machine, offset,
257 table_data, segbase,
258 fde_count);
259
260 return ret;
261}
262
263#ifndef NO_LIBUNWIND_DEBUG_FRAME
264static int read_unwind_spec_debug_frame(struct dso *dso,
265 struct machine *machine, u64 *offset)
266{
267 int fd = dso__data_fd(dso, machine);
268
269 if (fd < 0)
270 return -EINVAL;
271
272 /* Check the .debug_frame section for unwinding info */
273 *offset = elf_section_offset(fd, ".debug_frame");
274 close(fd);
275
276 if (*offset)
277 return 0;
278
279 return -EINVAL;
280}
281#endif
282
283static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
284{
285 struct addr_location al;
286
287 thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
288 MAP__FUNCTION, ip, &al);
289 return al.map;
290}
291
292static int
293find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
294 int need_unwind_info, void *arg)
295{
296 struct unwind_info *ui = arg;
297 struct map *map;
298 unw_dyn_info_t di;
299 u64 table_data, segbase, fde_count;
300
301 map = find_map(ip, ui);
302 if (!map || !map->dso)
303 return -EINVAL;
304
305 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
306
307 /* Check the .eh_frame section for unwinding info */
308 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
309 &table_data, &segbase, &fde_count)) {
310 memset(&di, 0, sizeof(di));
311 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
312 di.start_ip = map->start;
313 di.end_ip = map->end;
314 di.u.rti.segbase = map->start + segbase;
315 di.u.rti.table_data = map->start + table_data;
316 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
317 / sizeof(unw_word_t);
318 return dwarf_search_unwind_table(as, ip, &di, pi,
319 need_unwind_info, arg);
320 }
321
322#ifndef NO_LIBUNWIND_DEBUG_FRAME
323 /* Check the .debug_frame section for unwinding info */
324 if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
325 memset(&di, 0, sizeof(di));
326 if (dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name,
327 map->start, map->end))
328 return dwarf_search_unwind_table(as, ip, &di, pi,
329 need_unwind_info, arg);
330 }
331#endif
332
333 return -EINVAL;
334}
335
336static int access_fpreg(unw_addr_space_t __maybe_unused as,
337 unw_regnum_t __maybe_unused num,
338 unw_fpreg_t __maybe_unused *val,
339 int __maybe_unused __write,
340 void __maybe_unused *arg)
341{
342 pr_err("unwind: access_fpreg unsupported\n");
343 return -UNW_EINVAL;
344}
345
346static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
347 unw_word_t __maybe_unused *dil_addr,
348 void __maybe_unused *arg)
349{
350 return -UNW_ENOINFO;
351}
352
353static int resume(unw_addr_space_t __maybe_unused as,
354 unw_cursor_t __maybe_unused *cu,
355 void __maybe_unused *arg)
356{
357 pr_err("unwind: resume unsupported\n");
358 return -UNW_EINVAL;
359}
360
361static int
362get_proc_name(unw_addr_space_t __maybe_unused as,
363 unw_word_t __maybe_unused addr,
364 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
365 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
366{
367 pr_err("unwind: get_proc_name unsupported\n");
368 return -UNW_EINVAL;
369}
370
371static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
372 unw_word_t *data)
373{
374 struct addr_location al;
375 ssize_t size;
376
377 thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
378 MAP__FUNCTION, addr, &al);
379 if (!al.map) {
380 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
381 return -1;
382 }
383
384 if (!al.map->dso)
385 return -1;
386
387 size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
388 addr, (u8 *) data, sizeof(*data));
389
390 return !(size == sizeof(*data));
391}
392
393static int access_mem(unw_addr_space_t __maybe_unused as,
394 unw_word_t addr, unw_word_t *valp,
395 int __write, void *arg)
396{
397 struct unwind_info *ui = arg;
398 struct stack_dump *stack = &ui->sample->user_stack;
399 u64 start, end;
400 int offset;
401 int ret;
402
403 /* Don't support write, probably not needed. */
404 if (__write || !stack || !ui->sample->user_regs.regs) {
405 *valp = 0;
406 return 0;
407 }
408
409 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
410 if (ret)
411 return ret;
412
413 end = start + stack->size;
414
415 /* Check overflow. */
416 if (addr + sizeof(unw_word_t) < addr)
417 return -EINVAL;
418
419 if (addr < start || addr + sizeof(unw_word_t) >= end) {
420 ret = access_dso_mem(ui, addr, valp);
421 if (ret) {
422 pr_debug("unwind: access_mem %p not inside range"
423 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
424 (void *) addr, start, end);
425 *valp = 0;
426 return ret;
427 }
428 return 0;
429 }
430
431 offset = addr - start;
432 *valp = *(unw_word_t *)&stack->data[offset];
433 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
434 (void *) addr, (unsigned long)*valp, offset);
435 return 0;
436}
437
438static int access_reg(unw_addr_space_t __maybe_unused as,
439 unw_regnum_t regnum, unw_word_t *valp,
440 int __write, void *arg)
441{
442 struct unwind_info *ui = arg;
443 int id, ret;
444 u64 val;
445
446 /* Don't support write, I suspect we don't need it. */
447 if (__write) {
448 pr_err("unwind: access_reg w %d\n", regnum);
449 return 0;
450 }
451
452 if (!ui->sample->user_regs.regs) {
453 *valp = 0;
454 return 0;
455 }
456
457 id = libunwind__arch_reg_id(regnum);
458 if (id < 0)
459 return -EINVAL;
460
461 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
462 if (ret) {
463 pr_err("unwind: can't read reg %d\n", regnum);
464 return ret;
465 }
466
467 *valp = (unw_word_t) val;
468 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
469 return 0;
470}
471
472static void put_unwind_info(unw_addr_space_t __maybe_unused as,
473 unw_proc_info_t *pi __maybe_unused,
474 void *arg __maybe_unused)
475{
476 pr_debug("unwind: put_unwind_info called\n");
477}
478
479static int entry(u64 ip, struct thread *thread, struct machine *machine,
480 unwind_entry_cb_t cb, void *arg)
481{
482 struct unwind_entry e;
483 struct addr_location al;
484
485 thread__find_addr_location(thread, machine,
486 PERF_RECORD_MISC_USER,
487 MAP__FUNCTION, ip, &al);
488
489 e.ip = ip;
490 e.map = al.map;
491 e.sym = al.sym;
492
493 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
494 al.sym ? al.sym->name : "''",
495 ip,
496 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
497
498 return cb(&e, arg);
499}
500
501static void display_error(int err)
502{
503 switch (err) {
504 case UNW_EINVAL:
505 pr_err("unwind: Only supports local.\n");
506 break;
507 case UNW_EUNSPEC:
508 pr_err("unwind: Unspecified error.\n");
509 break;
510 case UNW_EBADREG:
511 pr_err("unwind: Register unavailable.\n");
512 break;
513 default:
514 break;
515 }
516}
517
518static unw_accessors_t accessors = {
519 .find_proc_info = find_proc_info,
520 .put_unwind_info = put_unwind_info,
521 .get_dyn_info_list_addr = get_dyn_info_list_addr,
522 .access_mem = access_mem,
523 .access_reg = access_reg,
524 .access_fpreg = access_fpreg,
525 .resume = resume,
526 .get_proc_name = get_proc_name,
527};
528
529static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
530 void *arg, int max_stack)
531{
532 unw_addr_space_t addr_space;
533 unw_cursor_t c;
534 int ret;
535
536 addr_space = unw_create_addr_space(&accessors, 0);
537 if (!addr_space) {
538 pr_err("unwind: Can't create unwind address space.\n");
539 return -ENOMEM;
540 }
541
542 ret = unw_init_remote(&c, addr_space, ui);
543 if (ret)
544 display_error(ret);
545
546 while (!ret && (unw_step(&c) > 0) && max_stack--) {
547 unw_word_t ip;
548
549 unw_get_reg(&c, UNW_REG_IP, &ip);
550 ret = ip ? entry(ip, ui->thread, ui->machine, cb, arg) : 0;
551 }
552
553 unw_destroy_addr_space(addr_space);
554 return ret;
555}
556
557int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
558 struct machine *machine, struct thread *thread,
559 struct perf_sample *data, int max_stack)
560{
561 u64 ip;
562 struct unwind_info ui = {
563 .sample = data,
564 .thread = thread,
565 .machine = machine,
566 };
567 int ret;
568
569 if (!data->user_regs.regs)
570 return -EINVAL;
571
572 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
573 if (ret)
574 return ret;
575
576 ret = entry(ip, thread, machine, cb, arg);
577 if (ret)
578 return -ENOMEM;
579
580 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0;
581}
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 map_groups *mg,
16 struct unwind_libunwind_ops *ops)
17{
18 mg->unwind_libunwind_ops = ops;
19}
20
21int unwind__prepare_access(struct map_groups *mg, struct map *map,
22 bool *initialized)
23{
24 const char *arch;
25 enum dso_type dso_type;
26 struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops;
27 int err;
28
29 if (!dwarf_callchain_users)
30 return 0;
31
32 if (mg->addr_space) {
33 pr_debug("unwind: thread map already set, dso=%s\n",
34 map->dso->name);
35 if (initialized)
36 *initialized = true;
37 return 0;
38 }
39
40 /* env->arch is NULL for live-mode (i.e. perf top) */
41 if (!mg->machine->env || !mg->machine->env->arch)
42 goto out_register;
43
44 dso_type = dso__type(map->dso, mg->machine);
45 if (dso_type == DSO__TYPE_UNKNOWN)
46 return 0;
47
48 arch = perf_env__arch(mg->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_err("unwind: target platform=%s is not supported\n", arch);
60 return 0;
61 }
62out_register:
63 unwind__register_ops(mg, ops);
64
65 err = mg->unwind_libunwind_ops->prepare_access(mg);
66 if (initialized)
67 *initialized = err ? false : true;
68 return err;
69}
70
71void unwind__flush_access(struct map_groups *mg)
72{
73 if (mg->unwind_libunwind_ops)
74 mg->unwind_libunwind_ops->flush_access(mg);
75}
76
77void unwind__finish_access(struct map_groups *mg)
78{
79 if (mg->unwind_libunwind_ops)
80 mg->unwind_libunwind_ops->finish_access(mg);
81}
82
83int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
84 struct thread *thread,
85 struct perf_sample *data, int max_stack)
86{
87 if (thread->mg->unwind_libunwind_ops)
88 return thread->mg->unwind_libunwind_ops->get_entries(cb, arg, thread, data, max_stack);
89 return 0;
90}