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 bool best_effort; 100 }; 101 102 #define dw_read(ptr, type, end) ({ \ 103 type *__p = (type *) ptr; \ 104 type __v; \ 105 if ((__p + 1) > (type *) end) \ 106 return -EINVAL; \ 107 __v = *__p++; \ 108 ptr = (typeof(ptr)) __p; \ 109 __v; \ 110 }) 111 112 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, 113 u8 encoding) 114 { 115 u8 *cur = *p; 116 *val = 0; 117 118 switch (encoding) { 119 case DW_EH_PE_omit: 120 *val = 0; 121 goto out; 122 case DW_EH_PE_ptr: 123 *val = dw_read(cur, unsigned long, end); 124 goto out; 125 default: 126 break; 127 } 128 129 switch (encoding & DW_EH_PE_APPL_MASK) { 130 case DW_EH_PE_absptr: 131 break; 132 case DW_EH_PE_pcrel: 133 *val = (unsigned long) cur; 134 break; 135 default: 136 return -EINVAL; 137 } 138 139 if ((encoding & 0x07) == 0x00) 140 encoding |= DW_EH_PE_udata4; 141 142 switch (encoding & DW_EH_PE_FORMAT_MASK) { 143 case DW_EH_PE_sdata4: 144 *val += dw_read(cur, s32, end); 145 break; 146 case DW_EH_PE_udata4: 147 *val += dw_read(cur, u32, end); 148 break; 149 case DW_EH_PE_sdata8: 150 *val += dw_read(cur, s64, end); 151 break; 152 case DW_EH_PE_udata8: 153 *val += dw_read(cur, u64, end); 154 break; 155 default: 156 return -EINVAL; 157 } 158 159 out: 160 *p = cur; 161 return 0; 162 } 163 164 #define dw_read_encoded_value(ptr, end, enc) ({ \ 165 u64 __v; \ 166 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ 167 return -EINVAL; \ 168 } \ 169 __v; \ 170 }) 171 172 static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset) 173 { 174 Elf *elf; 175 GElf_Ehdr ehdr; 176 GElf_Shdr shdr; 177 int ret = -1; 178 179 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 180 if (elf == NULL) 181 return -1; 182 183 if (gelf_getehdr(elf, &ehdr) == NULL) 184 goto out_err; 185 186 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL)) 187 goto out_err; 188 189 *address = shdr.sh_addr; 190 *offset = shdr.sh_offset; 191 ret = 0; 192 out_err: 193 elf_end(elf); 194 return ret; 195 } 196 197 #ifndef NO_LIBUNWIND_DEBUG_FRAME 198 static u64 elf_section_offset(int fd, const char *name) 199 { 200 u64 address, offset = 0; 201 202 if (elf_section_address_and_offset(fd, name, &address, &offset)) 203 return 0; 204 205 return offset; 206 } 207 #endif 208 209 static u64 elf_base_address(int fd) 210 { 211 Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 212 GElf_Phdr phdr; 213 u64 retval = 0; 214 size_t i, phdrnum = 0; 215 216 if (elf == NULL) 217 return 0; 218 (void)elf_getphdrnum(elf, &phdrnum); 219 /* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */ 220 for (i = 0; i < phdrnum; i++) { 221 if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) { 222 retval = phdr.p_vaddr & -getpagesize(); 223 break; 224 } 225 } 226 227 elf_end(elf); 228 return retval; 229 } 230 231 #ifndef NO_LIBUNWIND_DEBUG_FRAME 232 static int elf_is_exec(int fd, const char *name) 233 { 234 Elf *elf; 235 GElf_Ehdr ehdr; 236 int retval = 0; 237 238 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 239 if (elf == NULL) 240 return 0; 241 if (gelf_getehdr(elf, &ehdr) == NULL) 242 goto out; 243 244 retval = (ehdr.e_type == ET_EXEC); 245 246 out: 247 elf_end(elf); 248 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval); 249 return retval; 250 } 251 #endif 252 253 struct table_entry { 254 u32 start_ip_offset; 255 u32 fde_offset; 256 }; 257 258 struct eh_frame_hdr { 259 unsigned char version; 260 unsigned char eh_frame_ptr_enc; 261 unsigned char fde_count_enc; 262 unsigned char table_enc; 263 264 /* 265 * The rest of the header is variable-length and consists of the 266 * following members: 267 * 268 * encoded_t eh_frame_ptr; 269 * encoded_t fde_count; 270 */ 271 272 /* A single encoded pointer should not be more than 8 bytes. */ 273 u64 enc[2]; 274 275 /* 276 * struct { 277 * encoded_t start_ip; 278 * encoded_t fde_addr; 279 * } binary_search_table[fde_count]; 280 */ 281 char data[]; 282 } __packed; 283 284 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, 285 u64 offset, u64 *table_data_offset, u64 *fde_count) 286 { 287 struct eh_frame_hdr hdr; 288 u8 *enc = (u8 *) &hdr.enc; 289 u8 *end = (u8 *) &hdr.data; 290 ssize_t r; 291 292 r = dso__data_read_offset(dso, machine, offset, 293 (u8 *) &hdr, sizeof(hdr)); 294 if (r != sizeof(hdr)) 295 return -EINVAL; 296 297 /* We dont need eh_frame_ptr, just skip it. */ 298 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); 299 300 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); 301 *table_data_offset = enc - (u8 *) &hdr; 302 return 0; 303 } 304 305 struct read_unwind_spec_eh_frame_maps_cb_args { 306 struct dso *dso; 307 u64 base_addr; 308 }; 309 310 static int read_unwind_spec_eh_frame_maps_cb(struct map *map, void *data) 311 { 312 313 struct read_unwind_spec_eh_frame_maps_cb_args *args = data; 314 315 if (map__dso(map) == args->dso && map__start(map) - map__pgoff(map) < args->base_addr) 316 args->base_addr = map__start(map) - map__pgoff(map); 317 318 return 0; 319 } 320 321 322 static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui, 323 u64 *table_data, u64 *segbase, 324 u64 *fde_count) 325 { 326 struct read_unwind_spec_eh_frame_maps_cb_args args = { 327 .dso = dso, 328 .base_addr = UINT64_MAX, 329 }; 330 int ret, fd; 331 332 if (dso->data.eh_frame_hdr_offset == 0) { 333 fd = dso__data_get_fd(dso, ui->machine); 334 if (fd < 0) 335 return -EINVAL; 336 337 /* Check the .eh_frame section for unwinding info */ 338 ret = elf_section_address_and_offset(fd, ".eh_frame_hdr", 339 &dso->data.eh_frame_hdr_addr, 340 &dso->data.eh_frame_hdr_offset); 341 dso->data.elf_base_addr = elf_base_address(fd); 342 dso__data_put_fd(dso); 343 if (ret || dso->data.eh_frame_hdr_offset == 0) 344 return -EINVAL; 345 } 346 347 maps__for_each_map(thread__maps(ui->thread), read_unwind_spec_eh_frame_maps_cb, &args); 348 349 args.base_addr -= dso->data.elf_base_addr; 350 /* Address of .eh_frame_hdr */ 351 *segbase = args.base_addr + dso->data.eh_frame_hdr_addr; 352 ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset, 353 table_data, fde_count); 354 if (ret) 355 return ret; 356 /* binary_search_table offset plus .eh_frame_hdr address */ 357 *table_data += *segbase; 358 return 0; 359 } 360 361 #ifndef NO_LIBUNWIND_DEBUG_FRAME 362 static int read_unwind_spec_debug_frame(struct dso *dso, 363 struct machine *machine, u64 *offset) 364 { 365 int fd; 366 u64 ofs = dso->data.debug_frame_offset; 367 368 /* debug_frame can reside in: 369 * - dso 370 * - debug pointed by symsrc_filename 371 * - gnu_debuglink, which doesn't necessary 372 * has to be pointed by symsrc_filename 373 */ 374 if (ofs == 0) { 375 fd = dso__data_get_fd(dso, machine); 376 if (fd >= 0) { 377 ofs = elf_section_offset(fd, ".debug_frame"); 378 dso__data_put_fd(dso); 379 } 380 381 if (ofs <= 0) { 382 fd = open(dso->symsrc_filename, O_RDONLY); 383 if (fd >= 0) { 384 ofs = elf_section_offset(fd, ".debug_frame"); 385 close(fd); 386 } 387 } 388 389 if (ofs <= 0) { 390 char *debuglink = malloc(PATH_MAX); 391 int ret = 0; 392 393 ret = dso__read_binary_type_filename( 394 dso, DSO_BINARY_TYPE__DEBUGLINK, 395 machine->root_dir, debuglink, PATH_MAX); 396 if (!ret) { 397 fd = open(debuglink, O_RDONLY); 398 if (fd >= 0) { 399 ofs = elf_section_offset(fd, 400 ".debug_frame"); 401 close(fd); 402 } 403 } 404 if (ofs > 0) { 405 if (dso->symsrc_filename != NULL) { 406 pr_warning( 407 "%s: overwrite symsrc(%s,%s)\n", 408 __func__, 409 dso->symsrc_filename, 410 debuglink); 411 zfree(&dso->symsrc_filename); 412 } 413 dso->symsrc_filename = debuglink; 414 } else { 415 free(debuglink); 416 } 417 } 418 419 dso->data.debug_frame_offset = ofs; 420 } 421 422 *offset = ofs; 423 if (*offset) 424 return 0; 425 426 return -EINVAL; 427 } 428 #endif 429 430 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 431 { 432 struct addr_location al; 433 struct map *ret; 434 435 addr_location__init(&al); 436 thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al); 437 ret = map__get(al.map); 438 addr_location__exit(&al); 439 return ret; 440 } 441 442 static int 443 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 444 int need_unwind_info, void *arg) 445 { 446 struct unwind_info *ui = arg; 447 struct map *map; 448 struct dso *dso; 449 unw_dyn_info_t di; 450 u64 table_data, segbase, fde_count; 451 int ret = -EINVAL; 452 453 map = find_map(ip, ui); 454 if (!map) 455 return -EINVAL; 456 457 dso = map__dso(map); 458 if (!dso) { 459 map__put(map); 460 return -EINVAL; 461 } 462 463 pr_debug("unwind: find_proc_info dso %s\n", dso->name); 464 465 /* Check the .eh_frame section for unwinding info */ 466 if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) { 467 memset(&di, 0, sizeof(di)); 468 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 469 di.start_ip = map__start(map); 470 di.end_ip = map__end(map); 471 di.u.rti.segbase = segbase; 472 di.u.rti.table_data = table_data; 473 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 474 / sizeof(unw_word_t); 475 ret = dwarf_search_unwind_table(as, ip, &di, pi, 476 need_unwind_info, arg); 477 } 478 479 #ifndef NO_LIBUNWIND_DEBUG_FRAME 480 /* Check the .debug_frame section for unwinding info */ 481 if (ret < 0 && 482 !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) { 483 int fd = dso__data_get_fd(dso, ui->machine); 484 int is_exec = elf_is_exec(fd, dso->name); 485 u64 start = map__start(map); 486 unw_word_t base = is_exec ? 0 : start; 487 const char *symfile; 488 489 if (fd >= 0) 490 dso__data_put_fd(dso); 491 492 symfile = dso->symsrc_filename ?: dso->name; 493 494 memset(&di, 0, sizeof(di)); 495 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map))) 496 ret = dwarf_search_unwind_table(as, ip, &di, pi, 497 need_unwind_info, arg); 498 } 499 #endif 500 map__put(map); 501 return ret; 502 } 503 504 static int access_fpreg(unw_addr_space_t __maybe_unused as, 505 unw_regnum_t __maybe_unused num, 506 unw_fpreg_t __maybe_unused *val, 507 int __maybe_unused __write, 508 void __maybe_unused *arg) 509 { 510 pr_err("unwind: access_fpreg unsupported\n"); 511 return -UNW_EINVAL; 512 } 513 514 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 515 unw_word_t __maybe_unused *dil_addr, 516 void __maybe_unused *arg) 517 { 518 return -UNW_ENOINFO; 519 } 520 521 static int resume(unw_addr_space_t __maybe_unused as, 522 unw_cursor_t __maybe_unused *cu, 523 void __maybe_unused *arg) 524 { 525 pr_err("unwind: resume unsupported\n"); 526 return -UNW_EINVAL; 527 } 528 529 static int 530 get_proc_name(unw_addr_space_t __maybe_unused as, 531 unw_word_t __maybe_unused addr, 532 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 533 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 534 { 535 pr_err("unwind: get_proc_name unsupported\n"); 536 return -UNW_EINVAL; 537 } 538 539 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 540 unw_word_t *data) 541 { 542 struct map *map; 543 struct dso *dso; 544 ssize_t size; 545 546 map = find_map(addr, ui); 547 if (!map) { 548 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 549 return -1; 550 } 551 552 dso = map__dso(map); 553 554 if (!dso) { 555 map__put(map); 556 return -1; 557 } 558 559 size = dso__data_read_addr(dso, map, ui->machine, 560 addr, (u8 *) data, sizeof(*data)); 561 map__put(map); 562 return !(size == sizeof(*data)); 563 } 564 565 static int access_mem(unw_addr_space_t __maybe_unused as, 566 unw_word_t addr, unw_word_t *valp, 567 int __write, void *arg) 568 { 569 struct unwind_info *ui = arg; 570 const char *arch = perf_env__arch(ui->machine->env); 571 struct stack_dump *stack = &ui->sample->user_stack; 572 u64 start, end; 573 int offset; 574 int ret; 575 576 /* Don't support write, probably not needed. */ 577 if (__write || !stack || !ui->sample->user_regs.regs) { 578 *valp = 0; 579 return 0; 580 } 581 582 ret = perf_reg_value(&start, &ui->sample->user_regs, 583 perf_arch_reg_sp(arch)); 584 if (ret) 585 return ret; 586 587 end = start + stack->size; 588 589 /* Check overflow. */ 590 if (addr + sizeof(unw_word_t) < addr) 591 return -EINVAL; 592 593 if (addr < start || addr + sizeof(unw_word_t) >= end) { 594 ret = access_dso_mem(ui, addr, valp); 595 if (ret) { 596 pr_debug("unwind: access_mem %p not inside range" 597 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 598 (void *) (uintptr_t) addr, start, end); 599 *valp = 0; 600 return ret; 601 } 602 return 0; 603 } 604 605 offset = addr - start; 606 *valp = *(unw_word_t *)&stack->data[offset]; 607 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 608 (void *) (uintptr_t) addr, (unsigned long)*valp, offset); 609 return 0; 610 } 611 612 static int access_reg(unw_addr_space_t __maybe_unused as, 613 unw_regnum_t regnum, unw_word_t *valp, 614 int __write, void *arg) 615 { 616 struct unwind_info *ui = arg; 617 int id, ret; 618 u64 val; 619 620 /* Don't support write, I suspect we don't need it. */ 621 if (__write) { 622 pr_err("unwind: access_reg w %d\n", regnum); 623 return 0; 624 } 625 626 if (!ui->sample->user_regs.regs) { 627 *valp = 0; 628 return 0; 629 } 630 631 id = LIBUNWIND__ARCH_REG_ID(regnum); 632 if (id < 0) 633 return -EINVAL; 634 635 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 636 if (ret) { 637 if (!ui->best_effort) 638 pr_err("unwind: can't read reg %d\n", regnum); 639 return ret; 640 } 641 642 *valp = (unw_word_t) val; 643 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 644 return 0; 645 } 646 647 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 648 unw_proc_info_t *pi __maybe_unused, 649 void *arg __maybe_unused) 650 { 651 pr_debug("unwind: put_unwind_info called\n"); 652 } 653 654 static int entry(u64 ip, struct thread *thread, 655 unwind_entry_cb_t cb, void *arg) 656 { 657 struct unwind_entry e; 658 struct addr_location al; 659 int ret; 660 661 addr_location__init(&al); 662 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al); 663 e.ip = ip; 664 e.ms.map = al.map; 665 e.ms.maps = al.maps; 666 667 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 668 al.sym ? al.sym->name : "''", 669 ip, 670 al.map ? map__map_ip(al.map, ip) : (u64) 0); 671 672 ret = cb(&e, arg); 673 addr_location__exit(&al); 674 return ret; 675 } 676 677 static void display_error(int err) 678 { 679 switch (err) { 680 case UNW_EINVAL: 681 pr_err("unwind: Only supports local.\n"); 682 break; 683 case UNW_EUNSPEC: 684 pr_err("unwind: Unspecified error.\n"); 685 break; 686 case UNW_EBADREG: 687 pr_err("unwind: Register unavailable.\n"); 688 break; 689 default: 690 break; 691 } 692 } 693 694 static unw_accessors_t accessors = { 695 .find_proc_info = find_proc_info, 696 .put_unwind_info = put_unwind_info, 697 .get_dyn_info_list_addr = get_dyn_info_list_addr, 698 .access_mem = access_mem, 699 .access_reg = access_reg, 700 .access_fpreg = access_fpreg, 701 .resume = resume, 702 .get_proc_name = get_proc_name, 703 }; 704 705 static int _unwind__prepare_access(struct maps *maps) 706 { 707 void *addr_space = unw_create_addr_space(&accessors, 0); 708 709 maps__set_addr_space(maps, addr_space); 710 if (!addr_space) { 711 pr_err("unwind: Can't create unwind address space.\n"); 712 return -ENOMEM; 713 } 714 715 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL); 716 return 0; 717 } 718 719 static void _unwind__flush_access(struct maps *maps) 720 { 721 unw_flush_cache(maps__addr_space(maps), 0, 0); 722 } 723 724 static void _unwind__finish_access(struct maps *maps) 725 { 726 unw_destroy_addr_space(maps__addr_space(maps)); 727 } 728 729 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 730 void *arg, int max_stack) 731 { 732 const char *arch = perf_env__arch(ui->machine->env); 733 u64 val; 734 unw_word_t ips[max_stack]; 735 unw_addr_space_t addr_space; 736 unw_cursor_t c; 737 int ret, i = 0; 738 739 ret = perf_reg_value(&val, &ui->sample->user_regs, 740 perf_arch_reg_ip(arch)); 741 if (ret) 742 return ret; 743 744 ips[i++] = (unw_word_t) val; 745 746 /* 747 * If we need more than one entry, do the DWARF 748 * unwind itself. 749 */ 750 if (max_stack - 1 > 0) { 751 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL"); 752 addr_space = maps__addr_space(thread__maps(ui->thread)); 753 754 if (addr_space == NULL) 755 return -1; 756 757 ret = unw_init_remote(&c, addr_space, ui); 758 if (ret && !ui->best_effort) 759 display_error(ret); 760 761 while (!ret && (unw_step(&c) > 0) && i < max_stack) { 762 unw_get_reg(&c, UNW_REG_IP, &ips[i]); 763 764 /* 765 * Decrement the IP for any non-activation frames. 766 * this is required to properly find the srcline 767 * for caller frames. 768 * See also the documentation for dwfl_frame_pc(), 769 * which this code tries to replicate. 770 */ 771 if (unw_is_signal_frame(&c) <= 0) 772 --ips[i]; 773 774 ++i; 775 } 776 777 max_stack = i; 778 } 779 780 /* 781 * Display what we got based on the order setup. 782 */ 783 for (i = 0; i < max_stack && !ret; i++) { 784 int j = i; 785 786 if (callchain_param.order == ORDER_CALLER) 787 j = max_stack - i - 1; 788 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; 789 } 790 791 return ret; 792 } 793 794 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, 795 struct thread *thread, 796 struct perf_sample *data, int max_stack, 797 bool best_effort) 798 { 799 struct unwind_info ui = { 800 .sample = data, 801 .thread = thread, 802 .machine = maps__machine(thread__maps(thread)), 803 .best_effort = best_effort 804 }; 805 806 if (!data->user_regs.regs) 807 return -EINVAL; 808 809 if (max_stack <= 0) 810 return -EINVAL; 811 812 return get_entries(&ui, cb, arg, max_stack); 813 } 814 815 static struct unwind_libunwind_ops 816 _unwind_libunwind_ops = { 817 .prepare_access = _unwind__prepare_access, 818 .flush_access = _unwind__flush_access, 819 .finish_access = _unwind__finish_access, 820 .get_entries = _unwind__get_entries, 821 }; 822 823 #ifndef REMOTE_UNWIND_LIBUNWIND 824 struct unwind_libunwind_ops * 825 local_unwind_libunwind_ops = &_unwind_libunwind_ops; 826 #endif 827