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 44 extern int 45 UNW_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 53 extern int 54 UNW_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 intentionally 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 95 struct 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 }) 110 111 static 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 }) 170 171 static 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 197 static 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); 210 211 out: 212 elf_end(elf); 213 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval); 214 return retval; 215 } 216 #endif 217 218 struct table_entry { 219 u32 start_ip_offset; 220 u32 fde_offset; 221 }; 222 223 struct 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[]; 247 } __packed; 248 249 static 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 } 271 272 static 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 299 static 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 366 367 static 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 } 372 373 static int 374 find_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 } 428 429 static 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 } 438 439 static 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 } 445 446 static 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 } 453 454 static int 455 get_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 } 463 464 static 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 } 484 485 static 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 } 530 531 static 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 } 564 565 static 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 } 571 572 static 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.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al); 579 e.ip = ip; 580 e.ms.map = al.map; 581 e.ms.maps = al.maps; 582 583 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 584 al.sym ? al.sym->name : "''", 585 ip, 586 al.map ? al.map->map_ip(al.map, ip) : (u64) 0); 587 588 return cb(&e, arg); 589 } 590 591 static void display_error(int err) 592 { 593 switch (err) { 594 case UNW_EINVAL: 595 pr_err("unwind: Only supports local.\n"); 596 break; 597 case UNW_EUNSPEC: 598 pr_err("unwind: Unspecified error.\n"); 599 break; 600 case UNW_EBADREG: 601 pr_err("unwind: Register unavailable.\n"); 602 break; 603 default: 604 break; 605 } 606 } 607 608 static unw_accessors_t accessors = { 609 .find_proc_info = find_proc_info, 610 .put_unwind_info = put_unwind_info, 611 .get_dyn_info_list_addr = get_dyn_info_list_addr, 612 .access_mem = access_mem, 613 .access_reg = access_reg, 614 .access_fpreg = access_fpreg, 615 .resume = resume, 616 .get_proc_name = get_proc_name, 617 }; 618 619 static int _unwind__prepare_access(struct maps *maps) 620 { 621 maps->addr_space = unw_create_addr_space(&accessors, 0); 622 if (!maps->addr_space) { 623 pr_err("unwind: Can't create unwind address space.\n"); 624 return -ENOMEM; 625 } 626 627 unw_set_caching_policy(maps->addr_space, UNW_CACHE_GLOBAL); 628 return 0; 629 } 630 631 static void _unwind__flush_access(struct maps *maps) 632 { 633 unw_flush_cache(maps->addr_space, 0, 0); 634 } 635 636 static void _unwind__finish_access(struct maps *maps) 637 { 638 unw_destroy_addr_space(maps->addr_space); 639 } 640 641 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 642 void *arg, int max_stack) 643 { 644 u64 val; 645 unw_word_t ips[max_stack]; 646 unw_addr_space_t addr_space; 647 unw_cursor_t c; 648 int ret, i = 0; 649 650 ret = perf_reg_value(&val, &ui->sample->user_regs, 651 LIBUNWIND__ARCH_REG_IP); 652 if (ret) 653 return ret; 654 655 ips[i++] = (unw_word_t) val; 656 657 /* 658 * If we need more than one entry, do the DWARF 659 * unwind itself. 660 */ 661 if (max_stack - 1 > 0) { 662 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL"); 663 addr_space = ui->thread->maps->addr_space; 664 665 if (addr_space == NULL) 666 return -1; 667 668 ret = unw_init_remote(&c, addr_space, ui); 669 if (ret) 670 display_error(ret); 671 672 while (!ret && (unw_step(&c) > 0) && i < max_stack) { 673 unw_get_reg(&c, UNW_REG_IP, &ips[i]); 674 675 /* 676 * Decrement the IP for any non-activation frames. 677 * this is required to properly find the srcline 678 * for caller frames. 679 * See also the documentation for dwfl_frame_pc(), 680 * which this code tries to replicate. 681 */ 682 if (unw_is_signal_frame(&c) <= 0) 683 --ips[i]; 684 685 ++i; 686 } 687 688 max_stack = i; 689 } 690 691 /* 692 * Display what we got based on the order setup. 693 */ 694 for (i = 0; i < max_stack && !ret; i++) { 695 int j = i; 696 697 if (callchain_param.order == ORDER_CALLER) 698 j = max_stack - i - 1; 699 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; 700 } 701 702 return ret; 703 } 704 705 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, 706 struct thread *thread, 707 struct perf_sample *data, int max_stack) 708 { 709 struct unwind_info ui = { 710 .sample = data, 711 .thread = thread, 712 .machine = thread->maps->machine, 713 }; 714 715 if (!data->user_regs.regs) 716 return -EINVAL; 717 718 if (max_stack <= 0) 719 return -EINVAL; 720 721 return get_entries(&ui, cb, arg, max_stack); 722 } 723 724 static struct unwind_libunwind_ops 725 _unwind_libunwind_ops = { 726 .prepare_access = _unwind__prepare_access, 727 .flush_access = _unwind__flush_access, 728 .finish_access = _unwind__finish_access, 729 .get_entries = _unwind__get_entries, 730 }; 731 732 #ifndef REMOTE_UNWIND_LIBUNWIND 733 struct unwind_libunwind_ops * 734 local_unwind_libunwind_ops = &_unwind_libunwind_ops; 735 #endif 736