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 static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui, 306 u64 *table_data, u64 *segbase, 307 u64 *fde_count) 308 { 309 struct map_rb_node *map_node; 310 u64 base_addr = UINT64_MAX; 311 int ret, fd; 312 313 if (dso->data.eh_frame_hdr_offset == 0) { 314 fd = dso__data_get_fd(dso, ui->machine); 315 if (fd < 0) 316 return -EINVAL; 317 318 /* Check the .eh_frame section for unwinding info */ 319 ret = elf_section_address_and_offset(fd, ".eh_frame_hdr", 320 &dso->data.eh_frame_hdr_addr, 321 &dso->data.eh_frame_hdr_offset); 322 dso->data.elf_base_addr = elf_base_address(fd); 323 dso__data_put_fd(dso); 324 if (ret || dso->data.eh_frame_hdr_offset == 0) 325 return -EINVAL; 326 } 327 328 maps__for_each_entry(thread__maps(ui->thread), map_node) { 329 struct map *map = map_node->map; 330 u64 start = map__start(map); 331 332 if (map__dso(map) == dso && start < base_addr) 333 base_addr = start; 334 } 335 base_addr -= dso->data.elf_base_addr; 336 /* Address of .eh_frame_hdr */ 337 *segbase = base_addr + dso->data.eh_frame_hdr_addr; 338 ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset, 339 table_data, fde_count); 340 if (ret) 341 return ret; 342 /* binary_search_table offset plus .eh_frame_hdr address */ 343 *table_data += *segbase; 344 return 0; 345 } 346 347 #ifndef NO_LIBUNWIND_DEBUG_FRAME 348 static int read_unwind_spec_debug_frame(struct dso *dso, 349 struct machine *machine, u64 *offset) 350 { 351 int fd; 352 u64 ofs = dso->data.debug_frame_offset; 353 354 /* debug_frame can reside in: 355 * - dso 356 * - debug pointed by symsrc_filename 357 * - gnu_debuglink, which doesn't necessary 358 * has to be pointed by symsrc_filename 359 */ 360 if (ofs == 0) { 361 fd = dso__data_get_fd(dso, machine); 362 if (fd >= 0) { 363 ofs = elf_section_offset(fd, ".debug_frame"); 364 dso__data_put_fd(dso); 365 } 366 367 if (ofs <= 0) { 368 fd = open(dso->symsrc_filename, O_RDONLY); 369 if (fd >= 0) { 370 ofs = elf_section_offset(fd, ".debug_frame"); 371 close(fd); 372 } 373 } 374 375 if (ofs <= 0) { 376 char *debuglink = malloc(PATH_MAX); 377 int ret = 0; 378 379 ret = dso__read_binary_type_filename( 380 dso, DSO_BINARY_TYPE__DEBUGLINK, 381 machine->root_dir, debuglink, PATH_MAX); 382 if (!ret) { 383 fd = open(debuglink, O_RDONLY); 384 if (fd >= 0) { 385 ofs = elf_section_offset(fd, 386 ".debug_frame"); 387 close(fd); 388 } 389 } 390 if (ofs > 0) { 391 if (dso->symsrc_filename != NULL) { 392 pr_warning( 393 "%s: overwrite symsrc(%s,%s)\n", 394 __func__, 395 dso->symsrc_filename, 396 debuglink); 397 zfree(&dso->symsrc_filename); 398 } 399 dso->symsrc_filename = debuglink; 400 } else { 401 free(debuglink); 402 } 403 } 404 405 dso->data.debug_frame_offset = ofs; 406 } 407 408 *offset = ofs; 409 if (*offset) 410 return 0; 411 412 return -EINVAL; 413 } 414 #endif 415 416 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 417 { 418 struct addr_location al; 419 struct map *ret; 420 421 addr_location__init(&al); 422 ret = thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al); 423 addr_location__exit(&al); 424 return ret; 425 } 426 427 static int 428 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 429 int need_unwind_info, void *arg) 430 { 431 struct unwind_info *ui = arg; 432 struct map *map; 433 struct dso *dso; 434 unw_dyn_info_t di; 435 u64 table_data, segbase, fde_count; 436 int ret = -EINVAL; 437 438 map = find_map(ip, ui); 439 if (!map) 440 return -EINVAL; 441 442 dso = map__dso(map); 443 if (!dso) 444 return -EINVAL; 445 446 pr_debug("unwind: find_proc_info dso %s\n", dso->name); 447 448 /* Check the .eh_frame section for unwinding info */ 449 if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) { 450 memset(&di, 0, sizeof(di)); 451 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 452 di.start_ip = map__start(map); 453 di.end_ip = map__end(map); 454 di.u.rti.segbase = segbase; 455 di.u.rti.table_data = table_data; 456 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 457 / sizeof(unw_word_t); 458 ret = dwarf_search_unwind_table(as, ip, &di, pi, 459 need_unwind_info, arg); 460 } 461 462 #ifndef NO_LIBUNWIND_DEBUG_FRAME 463 /* Check the .debug_frame section for unwinding info */ 464 if (ret < 0 && 465 !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) { 466 int fd = dso__data_get_fd(dso, ui->machine); 467 int is_exec = elf_is_exec(fd, dso->name); 468 u64 start = map__start(map); 469 unw_word_t base = is_exec ? 0 : start; 470 const char *symfile; 471 472 if (fd >= 0) 473 dso__data_put_fd(dso); 474 475 symfile = dso->symsrc_filename ?: dso->name; 476 477 memset(&di, 0, sizeof(di)); 478 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map))) 479 return dwarf_search_unwind_table(as, ip, &di, pi, 480 need_unwind_info, arg); 481 } 482 #endif 483 484 return ret; 485 } 486 487 static int access_fpreg(unw_addr_space_t __maybe_unused as, 488 unw_regnum_t __maybe_unused num, 489 unw_fpreg_t __maybe_unused *val, 490 int __maybe_unused __write, 491 void __maybe_unused *arg) 492 { 493 pr_err("unwind: access_fpreg unsupported\n"); 494 return -UNW_EINVAL; 495 } 496 497 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 498 unw_word_t __maybe_unused *dil_addr, 499 void __maybe_unused *arg) 500 { 501 return -UNW_ENOINFO; 502 } 503 504 static int resume(unw_addr_space_t __maybe_unused as, 505 unw_cursor_t __maybe_unused *cu, 506 void __maybe_unused *arg) 507 { 508 pr_err("unwind: resume unsupported\n"); 509 return -UNW_EINVAL; 510 } 511 512 static int 513 get_proc_name(unw_addr_space_t __maybe_unused as, 514 unw_word_t __maybe_unused addr, 515 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 516 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 517 { 518 pr_err("unwind: get_proc_name unsupported\n"); 519 return -UNW_EINVAL; 520 } 521 522 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 523 unw_word_t *data) 524 { 525 struct map *map; 526 struct dso *dso; 527 ssize_t size; 528 529 map = find_map(addr, ui); 530 if (!map) { 531 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 532 return -1; 533 } 534 535 dso = map__dso(map); 536 537 if (!dso) 538 return -1; 539 540 size = dso__data_read_addr(dso, map, ui->machine, 541 addr, (u8 *) data, sizeof(*data)); 542 543 return !(size == sizeof(*data)); 544 } 545 546 static int access_mem(unw_addr_space_t __maybe_unused as, 547 unw_word_t addr, unw_word_t *valp, 548 int __write, void *arg) 549 { 550 struct unwind_info *ui = arg; 551 struct stack_dump *stack = &ui->sample->user_stack; 552 u64 start, end; 553 int offset; 554 int ret; 555 556 /* Don't support write, probably not needed. */ 557 if (__write || !stack || !ui->sample->user_regs.regs) { 558 *valp = 0; 559 return 0; 560 } 561 562 ret = perf_reg_value(&start, &ui->sample->user_regs, 563 LIBUNWIND__ARCH_REG_SP); 564 if (ret) 565 return ret; 566 567 end = start + stack->size; 568 569 /* Check overflow. */ 570 if (addr + sizeof(unw_word_t) < addr) 571 return -EINVAL; 572 573 if (addr < start || addr + sizeof(unw_word_t) >= end) { 574 ret = access_dso_mem(ui, addr, valp); 575 if (ret) { 576 pr_debug("unwind: access_mem %p not inside range" 577 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 578 (void *) (uintptr_t) addr, start, end); 579 *valp = 0; 580 return ret; 581 } 582 return 0; 583 } 584 585 offset = addr - start; 586 *valp = *(unw_word_t *)&stack->data[offset]; 587 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 588 (void *) (uintptr_t) addr, (unsigned long)*valp, offset); 589 return 0; 590 } 591 592 static int access_reg(unw_addr_space_t __maybe_unused as, 593 unw_regnum_t regnum, unw_word_t *valp, 594 int __write, void *arg) 595 { 596 struct unwind_info *ui = arg; 597 int id, ret; 598 u64 val; 599 600 /* Don't support write, I suspect we don't need it. */ 601 if (__write) { 602 pr_err("unwind: access_reg w %d\n", regnum); 603 return 0; 604 } 605 606 if (!ui->sample->user_regs.regs) { 607 *valp = 0; 608 return 0; 609 } 610 611 id = LIBUNWIND__ARCH_REG_ID(regnum); 612 if (id < 0) 613 return -EINVAL; 614 615 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 616 if (ret) { 617 if (!ui->best_effort) 618 pr_err("unwind: can't read reg %d\n", regnum); 619 return ret; 620 } 621 622 *valp = (unw_word_t) val; 623 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 624 return 0; 625 } 626 627 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 628 unw_proc_info_t *pi __maybe_unused, 629 void *arg __maybe_unused) 630 { 631 pr_debug("unwind: put_unwind_info called\n"); 632 } 633 634 static int entry(u64 ip, struct thread *thread, 635 unwind_entry_cb_t cb, void *arg) 636 { 637 struct unwind_entry e; 638 struct addr_location al; 639 int ret; 640 641 addr_location__init(&al); 642 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al); 643 e.ip = ip; 644 e.ms.map = al.map; 645 e.ms.maps = al.maps; 646 647 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 648 al.sym ? al.sym->name : "''", 649 ip, 650 al.map ? map__map_ip(al.map, ip) : (u64) 0); 651 652 ret = cb(&e, arg); 653 addr_location__exit(&al); 654 return ret; 655 } 656 657 static void display_error(int err) 658 { 659 switch (err) { 660 case UNW_EINVAL: 661 pr_err("unwind: Only supports local.\n"); 662 break; 663 case UNW_EUNSPEC: 664 pr_err("unwind: Unspecified error.\n"); 665 break; 666 case UNW_EBADREG: 667 pr_err("unwind: Register unavailable.\n"); 668 break; 669 default: 670 break; 671 } 672 } 673 674 static unw_accessors_t accessors = { 675 .find_proc_info = find_proc_info, 676 .put_unwind_info = put_unwind_info, 677 .get_dyn_info_list_addr = get_dyn_info_list_addr, 678 .access_mem = access_mem, 679 .access_reg = access_reg, 680 .access_fpreg = access_fpreg, 681 .resume = resume, 682 .get_proc_name = get_proc_name, 683 }; 684 685 static int _unwind__prepare_access(struct maps *maps) 686 { 687 void *addr_space = unw_create_addr_space(&accessors, 0); 688 689 RC_CHK_ACCESS(maps)->addr_space = addr_space; 690 if (!addr_space) { 691 pr_err("unwind: Can't create unwind address space.\n"); 692 return -ENOMEM; 693 } 694 695 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL); 696 return 0; 697 } 698 699 static void _unwind__flush_access(struct maps *maps) 700 { 701 unw_flush_cache(maps__addr_space(maps), 0, 0); 702 } 703 704 static void _unwind__finish_access(struct maps *maps) 705 { 706 unw_destroy_addr_space(maps__addr_space(maps)); 707 } 708 709 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 710 void *arg, int max_stack) 711 { 712 u64 val; 713 unw_word_t ips[max_stack]; 714 unw_addr_space_t addr_space; 715 unw_cursor_t c; 716 int ret, i = 0; 717 718 ret = perf_reg_value(&val, &ui->sample->user_regs, 719 LIBUNWIND__ARCH_REG_IP); 720 if (ret) 721 return ret; 722 723 ips[i++] = (unw_word_t) val; 724 725 /* 726 * If we need more than one entry, do the DWARF 727 * unwind itself. 728 */ 729 if (max_stack - 1 > 0) { 730 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL"); 731 addr_space = maps__addr_space(thread__maps(ui->thread)); 732 733 if (addr_space == NULL) 734 return -1; 735 736 ret = unw_init_remote(&c, addr_space, ui); 737 if (ret && !ui->best_effort) 738 display_error(ret); 739 740 while (!ret && (unw_step(&c) > 0) && i < max_stack) { 741 unw_get_reg(&c, UNW_REG_IP, &ips[i]); 742 743 /* 744 * Decrement the IP for any non-activation frames. 745 * this is required to properly find the srcline 746 * for caller frames. 747 * See also the documentation for dwfl_frame_pc(), 748 * which this code tries to replicate. 749 */ 750 if (unw_is_signal_frame(&c) <= 0) 751 --ips[i]; 752 753 ++i; 754 } 755 756 max_stack = i; 757 } 758 759 /* 760 * Display what we got based on the order setup. 761 */ 762 for (i = 0; i < max_stack && !ret; i++) { 763 int j = i; 764 765 if (callchain_param.order == ORDER_CALLER) 766 j = max_stack - i - 1; 767 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; 768 } 769 770 return ret; 771 } 772 773 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, 774 struct thread *thread, 775 struct perf_sample *data, int max_stack, 776 bool best_effort) 777 { 778 struct unwind_info ui = { 779 .sample = data, 780 .thread = thread, 781 .machine = maps__machine(thread__maps(thread)), 782 .best_effort = best_effort 783 }; 784 785 if (!data->user_regs.regs) 786 return -EINVAL; 787 788 if (max_stack <= 0) 789 return -EINVAL; 790 791 return get_entries(&ui, cb, arg, max_stack); 792 } 793 794 static struct unwind_libunwind_ops 795 _unwind_libunwind_ops = { 796 .prepare_access = _unwind__prepare_access, 797 .flush_access = _unwind__flush_access, 798 .finish_access = _unwind__finish_access, 799 .get_entries = _unwind__get_entries, 800 }; 801 802 #ifndef REMOTE_UNWIND_LIBUNWIND 803 struct unwind_libunwind_ops * 804 local_unwind_libunwind_ops = &_unwind_libunwind_ops; 805 #endif 806