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 = dso->data.eh_frame_hdr_offset; 270 271 if (offset == 0) { 272 fd = dso__data_get_fd(dso, machine); 273 if (fd < 0) 274 return -EINVAL; 275 276 /* Check the .eh_frame section for unwinding info */ 277 offset = elf_section_offset(fd, ".eh_frame_hdr"); 278 dso->data.eh_frame_hdr_offset = offset; 279 dso__data_put_fd(dso); 280 } 281 282 if (offset) 283 ret = unwind_spec_ehframe(dso, machine, offset, 284 table_data, segbase, 285 fde_count); 286 287 return ret; 288 } 289 290 #ifndef NO_LIBUNWIND_DEBUG_FRAME 291 static int read_unwind_spec_debug_frame(struct dso *dso, 292 struct machine *machine, u64 *offset) 293 { 294 int fd; 295 u64 ofs = dso->data.debug_frame_offset; 296 297 if (ofs == 0) { 298 fd = dso__data_get_fd(dso, machine); 299 if (fd < 0) 300 return -EINVAL; 301 302 /* Check the .debug_frame section for unwinding info */ 303 ofs = elf_section_offset(fd, ".debug_frame"); 304 dso->data.debug_frame_offset = ofs; 305 dso__data_put_fd(dso); 306 } 307 308 *offset = ofs; 309 if (*offset) 310 return 0; 311 312 return -EINVAL; 313 } 314 #endif 315 316 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 317 { 318 struct addr_location al; 319 320 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 321 MAP__FUNCTION, ip, &al); 322 return al.map; 323 } 324 325 static int 326 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 327 int need_unwind_info, void *arg) 328 { 329 struct unwind_info *ui = arg; 330 struct map *map; 331 unw_dyn_info_t di; 332 u64 table_data, segbase, fde_count; 333 int ret = -EINVAL; 334 335 map = find_map(ip, ui); 336 if (!map || !map->dso) 337 return -EINVAL; 338 339 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); 340 341 /* Check the .eh_frame section for unwinding info */ 342 if (!read_unwind_spec_eh_frame(map->dso, ui->machine, 343 &table_data, &segbase, &fde_count)) { 344 memset(&di, 0, sizeof(di)); 345 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 346 di.start_ip = map->start; 347 di.end_ip = map->end; 348 di.u.rti.segbase = map->start + segbase; 349 di.u.rti.table_data = map->start + table_data; 350 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 351 / sizeof(unw_word_t); 352 ret = dwarf_search_unwind_table(as, ip, &di, pi, 353 need_unwind_info, arg); 354 } 355 356 #ifndef NO_LIBUNWIND_DEBUG_FRAME 357 /* Check the .debug_frame section for unwinding info */ 358 if (ret < 0 && 359 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) { 360 int fd = dso__data_get_fd(map->dso, ui->machine); 361 int is_exec = elf_is_exec(fd, map->dso->name); 362 unw_word_t base = is_exec ? 0 : map->start; 363 const char *symfile; 364 365 if (fd >= 0) 366 dso__data_put_fd(map->dso); 367 368 symfile = map->dso->symsrc_filename ?: map->dso->name; 369 370 memset(&di, 0, sizeof(di)); 371 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, 372 map->start, map->end)) 373 return dwarf_search_unwind_table(as, ip, &di, pi, 374 need_unwind_info, arg); 375 } 376 #endif 377 378 return ret; 379 } 380 381 static int access_fpreg(unw_addr_space_t __maybe_unused as, 382 unw_regnum_t __maybe_unused num, 383 unw_fpreg_t __maybe_unused *val, 384 int __maybe_unused __write, 385 void __maybe_unused *arg) 386 { 387 pr_err("unwind: access_fpreg unsupported\n"); 388 return -UNW_EINVAL; 389 } 390 391 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 392 unw_word_t __maybe_unused *dil_addr, 393 void __maybe_unused *arg) 394 { 395 return -UNW_ENOINFO; 396 } 397 398 static int resume(unw_addr_space_t __maybe_unused as, 399 unw_cursor_t __maybe_unused *cu, 400 void __maybe_unused *arg) 401 { 402 pr_err("unwind: resume unsupported\n"); 403 return -UNW_EINVAL; 404 } 405 406 static int 407 get_proc_name(unw_addr_space_t __maybe_unused as, 408 unw_word_t __maybe_unused addr, 409 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 410 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 411 { 412 pr_err("unwind: get_proc_name unsupported\n"); 413 return -UNW_EINVAL; 414 } 415 416 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 417 unw_word_t *data) 418 { 419 struct addr_location al; 420 ssize_t size; 421 422 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 423 MAP__FUNCTION, addr, &al); 424 if (!al.map) { 425 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 426 return -1; 427 } 428 429 if (!al.map->dso) 430 return -1; 431 432 size = dso__data_read_addr(al.map->dso, al.map, ui->machine, 433 addr, (u8 *) data, sizeof(*data)); 434 435 return !(size == sizeof(*data)); 436 } 437 438 static int access_mem(unw_addr_space_t __maybe_unused as, 439 unw_word_t addr, unw_word_t *valp, 440 int __write, void *arg) 441 { 442 struct unwind_info *ui = arg; 443 struct stack_dump *stack = &ui->sample->user_stack; 444 u64 start, end; 445 int offset; 446 int ret; 447 448 /* Don't support write, probably not needed. */ 449 if (__write || !stack || !ui->sample->user_regs.regs) { 450 *valp = 0; 451 return 0; 452 } 453 454 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 455 if (ret) 456 return ret; 457 458 end = start + stack->size; 459 460 /* Check overflow. */ 461 if (addr + sizeof(unw_word_t) < addr) 462 return -EINVAL; 463 464 if (addr < start || addr + sizeof(unw_word_t) >= end) { 465 ret = access_dso_mem(ui, addr, valp); 466 if (ret) { 467 pr_debug("unwind: access_mem %p not inside range" 468 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 469 (void *) (uintptr_t) addr, start, end); 470 *valp = 0; 471 return ret; 472 } 473 return 0; 474 } 475 476 offset = addr - start; 477 *valp = *(unw_word_t *)&stack->data[offset]; 478 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 479 (void *) (uintptr_t) addr, (unsigned long)*valp, offset); 480 return 0; 481 } 482 483 static int access_reg(unw_addr_space_t __maybe_unused as, 484 unw_regnum_t regnum, unw_word_t *valp, 485 int __write, void *arg) 486 { 487 struct unwind_info *ui = arg; 488 int id, ret; 489 u64 val; 490 491 /* Don't support write, I suspect we don't need it. */ 492 if (__write) { 493 pr_err("unwind: access_reg w %d\n", regnum); 494 return 0; 495 } 496 497 if (!ui->sample->user_regs.regs) { 498 *valp = 0; 499 return 0; 500 } 501 502 id = libunwind__arch_reg_id(regnum); 503 if (id < 0) 504 return -EINVAL; 505 506 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 507 if (ret) { 508 pr_err("unwind: can't read reg %d\n", regnum); 509 return ret; 510 } 511 512 *valp = (unw_word_t) val; 513 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 514 return 0; 515 } 516 517 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 518 unw_proc_info_t *pi __maybe_unused, 519 void *arg __maybe_unused) 520 { 521 pr_debug("unwind: put_unwind_info called\n"); 522 } 523 524 static int entry(u64 ip, struct thread *thread, 525 unwind_entry_cb_t cb, void *arg) 526 { 527 struct unwind_entry e; 528 struct addr_location al; 529 530 thread__find_addr_location(thread, PERF_RECORD_MISC_USER, 531 MAP__FUNCTION, ip, &al); 532 533 e.ip = ip; 534 e.map = al.map; 535 e.sym = al.sym; 536 537 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 538 al.sym ? al.sym->name : "''", 539 ip, 540 al.map ? al.map->map_ip(al.map, ip) : (u64) 0); 541 542 return cb(&e, arg); 543 } 544 545 static void display_error(int err) 546 { 547 switch (err) { 548 case UNW_EINVAL: 549 pr_err("unwind: Only supports local.\n"); 550 break; 551 case UNW_EUNSPEC: 552 pr_err("unwind: Unspecified error.\n"); 553 break; 554 case UNW_EBADREG: 555 pr_err("unwind: Register unavailable.\n"); 556 break; 557 default: 558 break; 559 } 560 } 561 562 static unw_accessors_t accessors = { 563 .find_proc_info = find_proc_info, 564 .put_unwind_info = put_unwind_info, 565 .get_dyn_info_list_addr = get_dyn_info_list_addr, 566 .access_mem = access_mem, 567 .access_reg = access_reg, 568 .access_fpreg = access_fpreg, 569 .resume = resume, 570 .get_proc_name = get_proc_name, 571 }; 572 573 int unwind__prepare_access(struct thread *thread) 574 { 575 unw_addr_space_t addr_space; 576 577 if (callchain_param.record_mode != CALLCHAIN_DWARF) 578 return 0; 579 580 addr_space = unw_create_addr_space(&accessors, 0); 581 if (!addr_space) { 582 pr_err("unwind: Can't create unwind address space.\n"); 583 return -ENOMEM; 584 } 585 586 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL); 587 thread__set_priv(thread, addr_space); 588 589 return 0; 590 } 591 592 void unwind__flush_access(struct thread *thread) 593 { 594 unw_addr_space_t addr_space; 595 596 if (callchain_param.record_mode != CALLCHAIN_DWARF) 597 return; 598 599 addr_space = thread__priv(thread); 600 unw_flush_cache(addr_space, 0, 0); 601 } 602 603 void unwind__finish_access(struct thread *thread) 604 { 605 unw_addr_space_t addr_space; 606 607 if (callchain_param.record_mode != CALLCHAIN_DWARF) 608 return; 609 610 addr_space = thread__priv(thread); 611 unw_destroy_addr_space(addr_space); 612 } 613 614 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 615 void *arg, int max_stack) 616 { 617 u64 val; 618 unw_word_t ips[max_stack]; 619 unw_addr_space_t addr_space; 620 unw_cursor_t c; 621 int ret, i = 0; 622 623 ret = perf_reg_value(&val, &ui->sample->user_regs, PERF_REG_IP); 624 if (ret) 625 return ret; 626 627 ips[i++] = (unw_word_t) val; 628 629 /* 630 * If we need more than one entry, do the DWARF 631 * unwind itself. 632 */ 633 if (max_stack - 1 > 0) { 634 addr_space = thread__priv(ui->thread); 635 if (addr_space == NULL) 636 return -1; 637 638 ret = unw_init_remote(&c, addr_space, ui); 639 if (ret) 640 display_error(ret); 641 642 while (!ret && (unw_step(&c) > 0) && i < max_stack) { 643 unw_get_reg(&c, UNW_REG_IP, &ips[i]); 644 ++i; 645 } 646 647 max_stack = i; 648 } 649 650 /* 651 * Display what we got based on the order setup. 652 */ 653 for (i = 0; i < max_stack && !ret; i++) { 654 int j = i; 655 656 if (callchain_param.order == ORDER_CALLER) 657 j = max_stack - i - 1; 658 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; 659 } 660 661 return ret; 662 } 663 664 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 665 struct thread *thread, 666 struct perf_sample *data, int max_stack) 667 { 668 struct unwind_info ui = { 669 .sample = data, 670 .thread = thread, 671 .machine = thread->mg->machine, 672 }; 673 674 if (!data->user_regs.regs) 675 return -EINVAL; 676 677 if (max_stack <= 0) 678 return -EINVAL; 679 680 return get_entries(&ui, cb, arg, max_stack); 681 } 682