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