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71ad0f5e JO |
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 "util.h" | |
32 | ||
33 | extern int | |
34 | UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as, | |
35 | unw_word_t ip, | |
36 | unw_dyn_info_t *di, | |
37 | unw_proc_info_t *pi, | |
38 | int need_unwind_info, void *arg); | |
39 | ||
40 | #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table) | |
41 | ||
42 | #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */ | |
43 | #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */ | |
44 | ||
45 | /* Pointer-encoding formats: */ | |
46 | #define DW_EH_PE_omit 0xff | |
47 | #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */ | |
48 | #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */ | |
49 | #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */ | |
50 | #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */ | |
51 | #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */ | |
52 | ||
53 | /* Pointer-encoding application: */ | |
54 | #define DW_EH_PE_absptr 0x00 /* absolute value */ | |
55 | #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */ | |
56 | ||
57 | /* | |
58 | * The following are not documented by LSB v1.3, yet they are used by | |
59 | * GCC, presumably they aren't documented by LSB since they aren't | |
60 | * used on Linux: | |
61 | */ | |
62 | #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */ | |
63 | #define DW_EH_PE_aligned 0x50 /* aligned pointer */ | |
64 | ||
65 | /* Flags intentionaly not handled, since they're not needed: | |
66 | * #define DW_EH_PE_indirect 0x80 | |
67 | * #define DW_EH_PE_uleb128 0x01 | |
68 | * #define DW_EH_PE_udata2 0x02 | |
69 | * #define DW_EH_PE_sleb128 0x09 | |
70 | * #define DW_EH_PE_sdata2 0x0a | |
71 | * #define DW_EH_PE_textrel 0x20 | |
72 | * #define DW_EH_PE_datarel 0x30 | |
73 | */ | |
74 | ||
75 | struct unwind_info { | |
76 | struct perf_sample *sample; | |
77 | struct machine *machine; | |
78 | struct thread *thread; | |
79 | u64 sample_uregs; | |
80 | }; | |
81 | ||
82 | #define dw_read(ptr, type, end) ({ \ | |
83 | type *__p = (type *) ptr; \ | |
84 | type __v; \ | |
85 | if ((__p + 1) > (type *) end) \ | |
86 | return -EINVAL; \ | |
87 | __v = *__p++; \ | |
88 | ptr = (typeof(ptr)) __p; \ | |
89 | __v; \ | |
90 | }) | |
91 | ||
92 | static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, | |
93 | u8 encoding) | |
94 | { | |
95 | u8 *cur = *p; | |
96 | *val = 0; | |
97 | ||
98 | switch (encoding) { | |
99 | case DW_EH_PE_omit: | |
100 | *val = 0; | |
101 | goto out; | |
102 | case DW_EH_PE_ptr: | |
103 | *val = dw_read(cur, unsigned long, end); | |
104 | goto out; | |
105 | default: | |
106 | break; | |
107 | } | |
108 | ||
109 | switch (encoding & DW_EH_PE_APPL_MASK) { | |
110 | case DW_EH_PE_absptr: | |
111 | break; | |
112 | case DW_EH_PE_pcrel: | |
113 | *val = (unsigned long) cur; | |
114 | break; | |
115 | default: | |
116 | return -EINVAL; | |
117 | } | |
118 | ||
119 | if ((encoding & 0x07) == 0x00) | |
120 | encoding |= DW_EH_PE_udata4; | |
121 | ||
122 | switch (encoding & DW_EH_PE_FORMAT_MASK) { | |
123 | case DW_EH_PE_sdata4: | |
124 | *val += dw_read(cur, s32, end); | |
125 | break; | |
126 | case DW_EH_PE_udata4: | |
127 | *val += dw_read(cur, u32, end); | |
128 | break; | |
129 | case DW_EH_PE_sdata8: | |
130 | *val += dw_read(cur, s64, end); | |
131 | break; | |
132 | case DW_EH_PE_udata8: | |
133 | *val += dw_read(cur, u64, end); | |
134 | break; | |
135 | default: | |
136 | return -EINVAL; | |
137 | } | |
138 | ||
139 | out: | |
140 | *p = cur; | |
141 | return 0; | |
142 | } | |
143 | ||
144 | #define dw_read_encoded_value(ptr, end, enc) ({ \ | |
145 | u64 __v; \ | |
146 | if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ | |
147 | return -EINVAL; \ | |
148 | } \ | |
149 | __v; \ | |
150 | }) | |
151 | ||
152 | static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep, | |
153 | GElf_Shdr *shp, const char *name) | |
154 | { | |
155 | Elf_Scn *sec = NULL; | |
156 | ||
157 | while ((sec = elf_nextscn(elf, sec)) != NULL) { | |
158 | char *str; | |
159 | ||
160 | gelf_getshdr(sec, shp); | |
161 | str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name); | |
162 | if (!strcmp(name, str)) | |
163 | break; | |
164 | } | |
165 | ||
166 | return sec; | |
167 | } | |
168 | ||
169 | static u64 elf_section_offset(int fd, const char *name) | |
170 | { | |
171 | Elf *elf; | |
172 | GElf_Ehdr ehdr; | |
173 | GElf_Shdr shdr; | |
174 | u64 offset = 0; | |
175 | ||
176 | elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); | |
177 | if (elf == NULL) | |
178 | return 0; | |
179 | ||
180 | do { | |
181 | if (gelf_getehdr(elf, &ehdr) == NULL) | |
182 | break; | |
183 | ||
184 | if (!elf_section_by_name(elf, &ehdr, &shdr, name)) | |
185 | break; | |
186 | ||
187 | offset = shdr.sh_offset; | |
188 | } while (0); | |
189 | ||
190 | elf_end(elf); | |
191 | return offset; | |
192 | } | |
193 | ||
194 | struct table_entry { | |
195 | u32 start_ip_offset; | |
196 | u32 fde_offset; | |
197 | }; | |
198 | ||
199 | struct eh_frame_hdr { | |
200 | unsigned char version; | |
201 | unsigned char eh_frame_ptr_enc; | |
202 | unsigned char fde_count_enc; | |
203 | unsigned char table_enc; | |
204 | ||
205 | /* | |
206 | * The rest of the header is variable-length and consists of the | |
207 | * following members: | |
208 | * | |
209 | * encoded_t eh_frame_ptr; | |
210 | * encoded_t fde_count; | |
211 | */ | |
212 | ||
213 | /* A single encoded pointer should not be more than 8 bytes. */ | |
214 | u64 enc[2]; | |
215 | ||
216 | /* | |
217 | * struct { | |
218 | * encoded_t start_ip; | |
219 | * encoded_t fde_addr; | |
220 | * } binary_search_table[fde_count]; | |
221 | */ | |
222 | char data[0]; | |
223 | } __packed; | |
224 | ||
225 | static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, | |
226 | u64 offset, u64 *table_data, u64 *segbase, | |
227 | u64 *fde_count) | |
228 | { | |
229 | struct eh_frame_hdr hdr; | |
230 | u8 *enc = (u8 *) &hdr.enc; | |
231 | u8 *end = (u8 *) &hdr.data; | |
232 | ssize_t r; | |
233 | ||
234 | r = dso__data_read_offset(dso, machine, offset, | |
235 | (u8 *) &hdr, sizeof(hdr)); | |
236 | if (r != sizeof(hdr)) | |
237 | return -EINVAL; | |
238 | ||
239 | /* We dont need eh_frame_ptr, just skip it. */ | |
240 | dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); | |
241 | ||
242 | *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); | |
243 | *segbase = offset; | |
244 | *table_data = (enc - (u8 *) &hdr) + offset; | |
245 | return 0; | |
246 | } | |
247 | ||
248 | static int read_unwind_spec(struct dso *dso, struct machine *machine, | |
249 | u64 *table_data, u64 *segbase, u64 *fde_count) | |
250 | { | |
251 | int ret = -EINVAL, fd; | |
252 | u64 offset; | |
253 | ||
254 | fd = dso__data_fd(dso, machine); | |
255 | if (fd < 0) | |
256 | return -EINVAL; | |
257 | ||
258 | offset = elf_section_offset(fd, ".eh_frame_hdr"); | |
259 | close(fd); | |
260 | ||
261 | if (offset) | |
262 | ret = unwind_spec_ehframe(dso, machine, offset, | |
263 | table_data, segbase, | |
264 | fde_count); | |
265 | ||
266 | /* TODO .debug_frame check if eh_frame_hdr fails */ | |
267 | return ret; | |
268 | } | |
269 | ||
270 | static struct map *find_map(unw_word_t ip, struct unwind_info *ui) | |
271 | { | |
272 | struct addr_location al; | |
273 | ||
274 | thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, | |
275 | MAP__FUNCTION, ip, &al); | |
276 | return al.map; | |
277 | } | |
278 | ||
279 | static int | |
280 | find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, | |
281 | int need_unwind_info, void *arg) | |
282 | { | |
283 | struct unwind_info *ui = arg; | |
284 | struct map *map; | |
285 | unw_dyn_info_t di; | |
286 | u64 table_data, segbase, fde_count; | |
287 | ||
288 | map = find_map(ip, ui); | |
289 | if (!map || !map->dso) | |
290 | return -EINVAL; | |
291 | ||
292 | pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); | |
293 | ||
294 | if (read_unwind_spec(map->dso, ui->machine, | |
295 | &table_data, &segbase, &fde_count)) | |
296 | return -EINVAL; | |
297 | ||
298 | memset(&di, 0, sizeof(di)); | |
299 | di.format = UNW_INFO_FORMAT_REMOTE_TABLE; | |
300 | di.start_ip = map->start; | |
301 | di.end_ip = map->end; | |
302 | di.u.rti.segbase = map->start + segbase; | |
303 | di.u.rti.table_data = map->start + table_data; | |
304 | di.u.rti.table_len = fde_count * sizeof(struct table_entry) | |
305 | / sizeof(unw_word_t); | |
306 | return dwarf_search_unwind_table(as, ip, &di, pi, | |
307 | need_unwind_info, arg); | |
308 | } | |
309 | ||
310 | static int access_fpreg(unw_addr_space_t __used as, unw_regnum_t __used num, | |
311 | unw_fpreg_t __used *val, int __used __write, | |
312 | void __used *arg) | |
313 | { | |
314 | pr_err("unwind: access_fpreg unsupported\n"); | |
315 | return -UNW_EINVAL; | |
316 | } | |
317 | ||
318 | static int get_dyn_info_list_addr(unw_addr_space_t __used as, | |
319 | unw_word_t __used *dil_addr, | |
320 | void __used *arg) | |
321 | { | |
322 | return -UNW_ENOINFO; | |
323 | } | |
324 | ||
325 | static int resume(unw_addr_space_t __used as, unw_cursor_t __used *cu, | |
326 | void __used *arg) | |
327 | { | |
328 | pr_err("unwind: resume unsupported\n"); | |
329 | return -UNW_EINVAL; | |
330 | } | |
331 | ||
332 | static int | |
333 | get_proc_name(unw_addr_space_t __used as, unw_word_t __used addr, | |
334 | char __used *bufp, size_t __used buf_len, | |
335 | unw_word_t __used *offp, void __used *arg) | |
336 | { | |
337 | pr_err("unwind: get_proc_name unsupported\n"); | |
338 | return -UNW_EINVAL; | |
339 | } | |
340 | ||
341 | static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, | |
342 | unw_word_t *data) | |
343 | { | |
344 | struct addr_location al; | |
345 | ssize_t size; | |
346 | ||
347 | thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, | |
348 | MAP__FUNCTION, addr, &al); | |
349 | if (!al.map) { | |
350 | pr_debug("unwind: no map for %lx\n", (unsigned long)addr); | |
351 | return -1; | |
352 | } | |
353 | ||
354 | if (!al.map->dso) | |
355 | return -1; | |
356 | ||
357 | size = dso__data_read_addr(al.map->dso, al.map, ui->machine, | |
358 | addr, (u8 *) data, sizeof(*data)); | |
359 | ||
360 | return !(size == sizeof(*data)); | |
361 | } | |
362 | ||
363 | static int reg_value(unw_word_t *valp, struct regs_dump *regs, int id, | |
364 | u64 sample_regs) | |
365 | { | |
366 | int i, idx = 0; | |
367 | ||
368 | if (!(sample_regs & (1 << id))) | |
369 | return -EINVAL; | |
370 | ||
371 | for (i = 0; i < id; i++) { | |
372 | if (sample_regs & (1 << i)) | |
373 | idx++; | |
374 | } | |
375 | ||
376 | *valp = regs->regs[idx]; | |
377 | return 0; | |
378 | } | |
379 | ||
380 | static int access_mem(unw_addr_space_t __used as, | |
381 | unw_word_t addr, unw_word_t *valp, | |
382 | int __write, void *arg) | |
383 | { | |
384 | struct unwind_info *ui = arg; | |
385 | struct stack_dump *stack = &ui->sample->user_stack; | |
386 | unw_word_t start, end; | |
387 | int offset; | |
388 | int ret; | |
389 | ||
390 | /* Don't support write, probably not needed. */ | |
391 | if (__write || !stack || !ui->sample->user_regs.regs) { | |
392 | *valp = 0; | |
393 | return 0; | |
394 | } | |
395 | ||
396 | ret = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP, | |
397 | ui->sample_uregs); | |
398 | if (ret) | |
399 | return ret; | |
400 | ||
401 | end = start + stack->size; | |
402 | ||
403 | /* Check overflow. */ | |
404 | if (addr + sizeof(unw_word_t) < addr) | |
405 | return -EINVAL; | |
406 | ||
407 | if (addr < start || addr + sizeof(unw_word_t) >= end) { | |
408 | ret = access_dso_mem(ui, addr, valp); | |
409 | if (ret) { | |
410 | pr_debug("unwind: access_mem %p not inside range %p-%p\n", | |
411 | (void *)addr, (void *)start, (void *)end); | |
412 | *valp = 0; | |
413 | return ret; | |
414 | } | |
415 | return 0; | |
416 | } | |
417 | ||
418 | offset = addr - start; | |
419 | *valp = *(unw_word_t *)&stack->data[offset]; | |
420 | pr_debug("unwind: access_mem addr %p, val %lx, offset %d\n", | |
421 | (void *)addr, (unsigned long)*valp, offset); | |
422 | return 0; | |
423 | } | |
424 | ||
425 | static int access_reg(unw_addr_space_t __used as, | |
426 | unw_regnum_t regnum, unw_word_t *valp, | |
427 | int __write, void *arg) | |
428 | { | |
429 | struct unwind_info *ui = arg; | |
430 | int id, ret; | |
431 | ||
432 | /* Don't support write, I suspect we don't need it. */ | |
433 | if (__write) { | |
434 | pr_err("unwind: access_reg w %d\n", regnum); | |
435 | return 0; | |
436 | } | |
437 | ||
438 | if (!ui->sample->user_regs.regs) { | |
439 | *valp = 0; | |
440 | return 0; | |
441 | } | |
442 | ||
443 | id = unwind__arch_reg_id(regnum); | |
444 | if (id < 0) | |
445 | return -EINVAL; | |
446 | ||
447 | ret = reg_value(valp, &ui->sample->user_regs, id, ui->sample_uregs); | |
448 | if (ret) { | |
449 | pr_err("unwind: can't read reg %d\n", regnum); | |
450 | return ret; | |
451 | } | |
452 | ||
453 | pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); | |
454 | return 0; | |
455 | } | |
456 | ||
457 | static void put_unwind_info(unw_addr_space_t __used as, | |
458 | unw_proc_info_t *pi __used, | |
459 | void *arg __used) | |
460 | { | |
461 | pr_debug("unwind: put_unwind_info called\n"); | |
462 | } | |
463 | ||
464 | static int entry(u64 ip, struct thread *thread, struct machine *machine, | |
465 | unwind_entry_cb_t cb, void *arg) | |
466 | { | |
467 | struct unwind_entry e; | |
468 | struct addr_location al; | |
469 | ||
470 | thread__find_addr_location(thread, machine, | |
471 | PERF_RECORD_MISC_USER, | |
472 | MAP__FUNCTION, ip, &al, NULL); | |
473 | ||
474 | e.ip = ip; | |
475 | e.map = al.map; | |
476 | e.sym = al.sym; | |
477 | ||
478 | pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", | |
479 | al.sym ? al.sym->name : "''", | |
480 | ip, | |
481 | al.map ? al.map->map_ip(al.map, ip) : (u64) 0); | |
482 | ||
483 | return cb(&e, arg); | |
484 | } | |
485 | ||
486 | static void display_error(int err) | |
487 | { | |
488 | switch (err) { | |
489 | case UNW_EINVAL: | |
490 | pr_err("unwind: Only supports local.\n"); | |
491 | break; | |
492 | case UNW_EUNSPEC: | |
493 | pr_err("unwind: Unspecified error.\n"); | |
494 | break; | |
495 | case UNW_EBADREG: | |
496 | pr_err("unwind: Register unavailable.\n"); | |
497 | break; | |
498 | default: | |
499 | break; | |
500 | } | |
501 | } | |
502 | ||
503 | static unw_accessors_t accessors = { | |
504 | .find_proc_info = find_proc_info, | |
505 | .put_unwind_info = put_unwind_info, | |
506 | .get_dyn_info_list_addr = get_dyn_info_list_addr, | |
507 | .access_mem = access_mem, | |
508 | .access_reg = access_reg, | |
509 | .access_fpreg = access_fpreg, | |
510 | .resume = resume, | |
511 | .get_proc_name = get_proc_name, | |
512 | }; | |
513 | ||
514 | static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, | |
515 | void *arg) | |
516 | { | |
517 | unw_addr_space_t addr_space; | |
518 | unw_cursor_t c; | |
519 | int ret; | |
520 | ||
521 | addr_space = unw_create_addr_space(&accessors, 0); | |
522 | if (!addr_space) { | |
523 | pr_err("unwind: Can't create unwind address space.\n"); | |
524 | return -ENOMEM; | |
525 | } | |
526 | ||
527 | ret = unw_init_remote(&c, addr_space, ui); | |
528 | if (ret) | |
529 | display_error(ret); | |
530 | ||
531 | while (!ret && (unw_step(&c) > 0)) { | |
532 | unw_word_t ip; | |
533 | ||
534 | unw_get_reg(&c, UNW_REG_IP, &ip); | |
535 | ret = entry(ip, ui->thread, ui->machine, cb, arg); | |
536 | } | |
537 | ||
538 | unw_destroy_addr_space(addr_space); | |
539 | return ret; | |
540 | } | |
541 | ||
542 | int unwind__get_entries(unwind_entry_cb_t cb, void *arg, | |
543 | struct machine *machine, struct thread *thread, | |
544 | u64 sample_uregs, struct perf_sample *data) | |
545 | { | |
546 | unw_word_t ip; | |
547 | struct unwind_info ui = { | |
548 | .sample = data, | |
549 | .sample_uregs = sample_uregs, | |
550 | .thread = thread, | |
551 | .machine = machine, | |
552 | }; | |
553 | int ret; | |
554 | ||
555 | if (!data->user_regs.regs) | |
556 | return -EINVAL; | |
557 | ||
558 | ret = reg_value(&ip, &data->user_regs, PERF_REG_IP, sample_uregs); | |
559 | if (ret) | |
560 | return ret; | |
561 | ||
562 | ret = entry(ip, thread, machine, cb, arg); | |
563 | if (ret) | |
564 | return -ENOMEM; | |
565 | ||
566 | return get_entries(&ui, cb, arg); | |
567 | } |