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 "callchain.h" 28 #include "thread.h" 29 #include "session.h" 30 #include "perf_regs.h" 31 #include "unwind.h" 32 #include "symbol.h" 33 #include "util.h" 34 #include "debug.h" 35 36 extern int 37 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as, 38 unw_word_t ip, 39 unw_dyn_info_t *di, 40 unw_proc_info_t *pi, 41 int need_unwind_info, void *arg); 42 43 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table) 44 45 extern int 46 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug, 47 unw_word_t ip, 48 unw_word_t segbase, 49 const char *obj_name, unw_word_t start, 50 unw_word_t end); 51 52 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame) 53 54 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */ 55 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */ 56 57 /* Pointer-encoding formats: */ 58 #define DW_EH_PE_omit 0xff 59 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */ 60 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */ 61 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */ 62 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */ 63 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */ 64 65 /* Pointer-encoding application: */ 66 #define DW_EH_PE_absptr 0x00 /* absolute value */ 67 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */ 68 69 /* 70 * The following are not documented by LSB v1.3, yet they are used by 71 * GCC, presumably they aren't documented by LSB since they aren't 72 * used on Linux: 73 */ 74 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */ 75 #define DW_EH_PE_aligned 0x50 /* aligned pointer */ 76 77 /* Flags intentionaly not handled, since they're not needed: 78 * #define DW_EH_PE_indirect 0x80 79 * #define DW_EH_PE_uleb128 0x01 80 * #define DW_EH_PE_udata2 0x02 81 * #define DW_EH_PE_sleb128 0x09 82 * #define DW_EH_PE_sdata2 0x0a 83 * #define DW_EH_PE_textrel 0x20 84 * #define DW_EH_PE_datarel 0x30 85 */ 86 87 struct unwind_info { 88 struct perf_sample *sample; 89 struct machine *machine; 90 struct thread *thread; 91 }; 92 93 #define dw_read(ptr, type, end) ({ \ 94 type *__p = (type *) ptr; \ 95 type __v; \ 96 if ((__p + 1) > (type *) end) \ 97 return -EINVAL; \ 98 __v = *__p++; \ 99 ptr = (typeof(ptr)) __p; \ 100 __v; \ 101 }) 102 103 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, 104 u8 encoding) 105 { 106 u8 *cur = *p; 107 *val = 0; 108 109 switch (encoding) { 110 case DW_EH_PE_omit: 111 *val = 0; 112 goto out; 113 case DW_EH_PE_ptr: 114 *val = dw_read(cur, unsigned long, end); 115 goto out; 116 default: 117 break; 118 } 119 120 switch (encoding & DW_EH_PE_APPL_MASK) { 121 case DW_EH_PE_absptr: 122 break; 123 case DW_EH_PE_pcrel: 124 *val = (unsigned long) cur; 125 break; 126 default: 127 return -EINVAL; 128 } 129 130 if ((encoding & 0x07) == 0x00) 131 encoding |= DW_EH_PE_udata4; 132 133 switch (encoding & DW_EH_PE_FORMAT_MASK) { 134 case DW_EH_PE_sdata4: 135 *val += dw_read(cur, s32, end); 136 break; 137 case DW_EH_PE_udata4: 138 *val += dw_read(cur, u32, end); 139 break; 140 case DW_EH_PE_sdata8: 141 *val += dw_read(cur, s64, end); 142 break; 143 case DW_EH_PE_udata8: 144 *val += dw_read(cur, u64, end); 145 break; 146 default: 147 return -EINVAL; 148 } 149 150 out: 151 *p = cur; 152 return 0; 153 } 154 155 #define dw_read_encoded_value(ptr, end, enc) ({ \ 156 u64 __v; \ 157 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ 158 return -EINVAL; \ 159 } \ 160 __v; \ 161 }) 162 163 static u64 elf_section_offset(int fd, const char *name) 164 { 165 Elf *elf; 166 GElf_Ehdr ehdr; 167 GElf_Shdr shdr; 168 u64 offset = 0; 169 170 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 171 if (elf == NULL) 172 return 0; 173 174 do { 175 if (gelf_getehdr(elf, &ehdr) == NULL) 176 break; 177 178 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL)) 179 break; 180 181 offset = shdr.sh_offset; 182 } while (0); 183 184 elf_end(elf); 185 return offset; 186 } 187 188 #ifndef NO_LIBUNWIND_DEBUG_FRAME 189 static int elf_is_exec(int fd, const char *name) 190 { 191 Elf *elf; 192 GElf_Ehdr ehdr; 193 int retval = 0; 194 195 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 196 if (elf == NULL) 197 return 0; 198 if (gelf_getehdr(elf, &ehdr) == NULL) 199 goto out; 200 201 retval = (ehdr.e_type == ET_EXEC); 202 203 out: 204 elf_end(elf); 205 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval); 206 return retval; 207 } 208 #endif 209 210 struct table_entry { 211 u32 start_ip_offset; 212 u32 fde_offset; 213 }; 214 215 struct eh_frame_hdr { 216 unsigned char version; 217 unsigned char eh_frame_ptr_enc; 218 unsigned char fde_count_enc; 219 unsigned char table_enc; 220 221 /* 222 * The rest of the header is variable-length and consists of the 223 * following members: 224 * 225 * encoded_t eh_frame_ptr; 226 * encoded_t fde_count; 227 */ 228 229 /* A single encoded pointer should not be more than 8 bytes. */ 230 u64 enc[2]; 231 232 /* 233 * struct { 234 * encoded_t start_ip; 235 * encoded_t fde_addr; 236 * } binary_search_table[fde_count]; 237 */ 238 char data[0]; 239 } __packed; 240 241 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, 242 u64 offset, u64 *table_data, u64 *segbase, 243 u64 *fde_count) 244 { 245 struct eh_frame_hdr hdr; 246 u8 *enc = (u8 *) &hdr.enc; 247 u8 *end = (u8 *) &hdr.data; 248 ssize_t r; 249 250 r = dso__data_read_offset(dso, machine, offset, 251 (u8 *) &hdr, sizeof(hdr)); 252 if (r != sizeof(hdr)) 253 return -EINVAL; 254 255 /* We dont need eh_frame_ptr, just skip it. */ 256 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); 257 258 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); 259 *segbase = offset; 260 *table_data = (enc - (u8 *) &hdr) + offset; 261 return 0; 262 } 263 264 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine, 265 u64 *table_data, u64 *segbase, 266 u64 *fde_count) 267 { 268 int ret = -EINVAL, fd; 269 u64 offset; 270 271 fd = dso__data_fd(dso, machine); 272 if (fd < 0) 273 return -EINVAL; 274 275 /* Check the .eh_frame section for unwinding info */ 276 offset = elf_section_offset(fd, ".eh_frame_hdr"); 277 278 if (offset) 279 ret = unwind_spec_ehframe(dso, machine, offset, 280 table_data, segbase, 281 fde_count); 282 283 return ret; 284 } 285 286 #ifndef NO_LIBUNWIND_DEBUG_FRAME 287 static int read_unwind_spec_debug_frame(struct dso *dso, 288 struct machine *machine, u64 *offset) 289 { 290 int fd = dso__data_fd(dso, machine); 291 292 if (fd < 0) 293 return -EINVAL; 294 295 /* Check the .debug_frame section for unwinding info */ 296 *offset = elf_section_offset(fd, ".debug_frame"); 297 298 if (*offset) 299 return 0; 300 301 return -EINVAL; 302 } 303 #endif 304 305 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 306 { 307 struct addr_location al; 308 309 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 310 MAP__FUNCTION, ip, &al); 311 return al.map; 312 } 313 314 static int 315 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 316 int need_unwind_info, void *arg) 317 { 318 struct unwind_info *ui = arg; 319 struct map *map; 320 unw_dyn_info_t di; 321 u64 table_data, segbase, fde_count; 322 323 map = find_map(ip, ui); 324 if (!map || !map->dso) 325 return -EINVAL; 326 327 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); 328 329 /* Check the .eh_frame section for unwinding info */ 330 if (!read_unwind_spec_eh_frame(map->dso, ui->machine, 331 &table_data, &segbase, &fde_count)) { 332 memset(&di, 0, sizeof(di)); 333 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 334 di.start_ip = map->start; 335 di.end_ip = map->end; 336 di.u.rti.segbase = map->start + segbase; 337 di.u.rti.table_data = map->start + table_data; 338 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 339 / sizeof(unw_word_t); 340 return dwarf_search_unwind_table(as, ip, &di, pi, 341 need_unwind_info, arg); 342 } 343 344 #ifndef NO_LIBUNWIND_DEBUG_FRAME 345 /* Check the .debug_frame section for unwinding info */ 346 if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) { 347 int fd = dso__data_fd(map->dso, ui->machine); 348 int is_exec = elf_is_exec(fd, map->dso->name); 349 unw_word_t base = is_exec ? 0 : map->start; 350 351 memset(&di, 0, sizeof(di)); 352 if (dwarf_find_debug_frame(0, &di, ip, base, map->dso->name, 353 map->start, map->end)) 354 return dwarf_search_unwind_table(as, ip, &di, pi, 355 need_unwind_info, arg); 356 } 357 #endif 358 359 return -EINVAL; 360 } 361 362 static int access_fpreg(unw_addr_space_t __maybe_unused as, 363 unw_regnum_t __maybe_unused num, 364 unw_fpreg_t __maybe_unused *val, 365 int __maybe_unused __write, 366 void __maybe_unused *arg) 367 { 368 pr_err("unwind: access_fpreg unsupported\n"); 369 return -UNW_EINVAL; 370 } 371 372 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 373 unw_word_t __maybe_unused *dil_addr, 374 void __maybe_unused *arg) 375 { 376 return -UNW_ENOINFO; 377 } 378 379 static int resume(unw_addr_space_t __maybe_unused as, 380 unw_cursor_t __maybe_unused *cu, 381 void __maybe_unused *arg) 382 { 383 pr_err("unwind: resume unsupported\n"); 384 return -UNW_EINVAL; 385 } 386 387 static int 388 get_proc_name(unw_addr_space_t __maybe_unused as, 389 unw_word_t __maybe_unused addr, 390 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 391 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 392 { 393 pr_err("unwind: get_proc_name unsupported\n"); 394 return -UNW_EINVAL; 395 } 396 397 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 398 unw_word_t *data) 399 { 400 struct addr_location al; 401 ssize_t size; 402 403 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 404 MAP__FUNCTION, addr, &al); 405 if (!al.map) { 406 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 407 return -1; 408 } 409 410 if (!al.map->dso) 411 return -1; 412 413 size = dso__data_read_addr(al.map->dso, al.map, ui->machine, 414 addr, (u8 *) data, sizeof(*data)); 415 416 return !(size == sizeof(*data)); 417 } 418 419 static int access_mem(unw_addr_space_t __maybe_unused as, 420 unw_word_t addr, unw_word_t *valp, 421 int __write, void *arg) 422 { 423 struct unwind_info *ui = arg; 424 struct stack_dump *stack = &ui->sample->user_stack; 425 u64 start, end; 426 int offset; 427 int ret; 428 429 /* Don't support write, probably not needed. */ 430 if (__write || !stack || !ui->sample->user_regs.regs) { 431 *valp = 0; 432 return 0; 433 } 434 435 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 436 if (ret) 437 return ret; 438 439 end = start + stack->size; 440 441 /* Check overflow. */ 442 if (addr + sizeof(unw_word_t) < addr) 443 return -EINVAL; 444 445 if (addr < start || addr + sizeof(unw_word_t) >= end) { 446 ret = access_dso_mem(ui, addr, valp); 447 if (ret) { 448 pr_debug("unwind: access_mem %p not inside range" 449 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 450 (void *) addr, start, end); 451 *valp = 0; 452 return ret; 453 } 454 return 0; 455 } 456 457 offset = addr - start; 458 *valp = *(unw_word_t *)&stack->data[offset]; 459 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 460 (void *) addr, (unsigned long)*valp, offset); 461 return 0; 462 } 463 464 static int access_reg(unw_addr_space_t __maybe_unused as, 465 unw_regnum_t regnum, unw_word_t *valp, 466 int __write, void *arg) 467 { 468 struct unwind_info *ui = arg; 469 int id, ret; 470 u64 val; 471 472 /* Don't support write, I suspect we don't need it. */ 473 if (__write) { 474 pr_err("unwind: access_reg w %d\n", regnum); 475 return 0; 476 } 477 478 if (!ui->sample->user_regs.regs) { 479 *valp = 0; 480 return 0; 481 } 482 483 id = libunwind__arch_reg_id(regnum); 484 if (id < 0) 485 return -EINVAL; 486 487 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 488 if (ret) { 489 pr_err("unwind: can't read reg %d\n", regnum); 490 return ret; 491 } 492 493 *valp = (unw_word_t) val; 494 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 495 return 0; 496 } 497 498 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 499 unw_proc_info_t *pi __maybe_unused, 500 void *arg __maybe_unused) 501 { 502 pr_debug("unwind: put_unwind_info called\n"); 503 } 504 505 static int entry(u64 ip, struct thread *thread, 506 unwind_entry_cb_t cb, void *arg) 507 { 508 struct unwind_entry e; 509 struct addr_location al; 510 511 thread__find_addr_location(thread, PERF_RECORD_MISC_USER, 512 MAP__FUNCTION, ip, &al); 513 514 e.ip = ip; 515 e.map = al.map; 516 e.sym = al.sym; 517 518 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 519 al.sym ? al.sym->name : "''", 520 ip, 521 al.map ? al.map->map_ip(al.map, ip) : (u64) 0); 522 523 return cb(&e, arg); 524 } 525 526 static void display_error(int err) 527 { 528 switch (err) { 529 case UNW_EINVAL: 530 pr_err("unwind: Only supports local.\n"); 531 break; 532 case UNW_EUNSPEC: 533 pr_err("unwind: Unspecified error.\n"); 534 break; 535 case UNW_EBADREG: 536 pr_err("unwind: Register unavailable.\n"); 537 break; 538 default: 539 break; 540 } 541 } 542 543 static unw_accessors_t accessors = { 544 .find_proc_info = find_proc_info, 545 .put_unwind_info = put_unwind_info, 546 .get_dyn_info_list_addr = get_dyn_info_list_addr, 547 .access_mem = access_mem, 548 .access_reg = access_reg, 549 .access_fpreg = access_fpreg, 550 .resume = resume, 551 .get_proc_name = get_proc_name, 552 }; 553 554 int unwind__prepare_access(struct thread *thread) 555 { 556 unw_addr_space_t addr_space; 557 558 if (callchain_param.record_mode != CALLCHAIN_DWARF) 559 return 0; 560 561 addr_space = unw_create_addr_space(&accessors, 0); 562 if (!addr_space) { 563 pr_err("unwind: Can't create unwind address space.\n"); 564 return -ENOMEM; 565 } 566 567 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL); 568 thread__set_priv(thread, addr_space); 569 570 return 0; 571 } 572 573 void unwind__flush_access(struct thread *thread) 574 { 575 unw_addr_space_t addr_space; 576 577 if (callchain_param.record_mode != CALLCHAIN_DWARF) 578 return; 579 580 addr_space = thread__priv(thread); 581 unw_flush_cache(addr_space, 0, 0); 582 } 583 584 void unwind__finish_access(struct thread *thread) 585 { 586 unw_addr_space_t addr_space; 587 588 if (callchain_param.record_mode != CALLCHAIN_DWARF) 589 return; 590 591 addr_space = thread__priv(thread); 592 unw_destroy_addr_space(addr_space); 593 } 594 595 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 596 void *arg, int max_stack) 597 { 598 unw_addr_space_t addr_space; 599 unw_cursor_t c; 600 int ret; 601 602 addr_space = thread__priv(ui->thread); 603 if (addr_space == NULL) 604 return -1; 605 606 ret = unw_init_remote(&c, addr_space, ui); 607 if (ret) 608 display_error(ret); 609 610 while (!ret && (unw_step(&c) > 0) && max_stack--) { 611 unw_word_t ip; 612 613 unw_get_reg(&c, UNW_REG_IP, &ip); 614 ret = ip ? entry(ip, ui->thread, cb, arg) : 0; 615 } 616 617 return ret; 618 } 619 620 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 621 struct thread *thread, 622 struct perf_sample *data, int max_stack) 623 { 624 u64 ip; 625 struct unwind_info ui = { 626 .sample = data, 627 .thread = thread, 628 .machine = thread->mg->machine, 629 }; 630 int ret; 631 632 if (!data->user_regs.regs) 633 return -EINVAL; 634 635 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP); 636 if (ret) 637 return ret; 638 639 ret = entry(ip, thread, cb, arg); 640 if (ret) 641 return -ENOMEM; 642 643 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0; 644 } 645