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 struct table_entry { 189 u32 start_ip_offset; 190 u32 fde_offset; 191 }; 192 193 struct eh_frame_hdr { 194 unsigned char version; 195 unsigned char eh_frame_ptr_enc; 196 unsigned char fde_count_enc; 197 unsigned char table_enc; 198 199 /* 200 * The rest of the header is variable-length and consists of the 201 * following members: 202 * 203 * encoded_t eh_frame_ptr; 204 * encoded_t fde_count; 205 */ 206 207 /* A single encoded pointer should not be more than 8 bytes. */ 208 u64 enc[2]; 209 210 /* 211 * struct { 212 * encoded_t start_ip; 213 * encoded_t fde_addr; 214 * } binary_search_table[fde_count]; 215 */ 216 char data[0]; 217 } __packed; 218 219 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, 220 u64 offset, u64 *table_data, u64 *segbase, 221 u64 *fde_count) 222 { 223 struct eh_frame_hdr hdr; 224 u8 *enc = (u8 *) &hdr.enc; 225 u8 *end = (u8 *) &hdr.data; 226 ssize_t r; 227 228 r = dso__data_read_offset(dso, machine, offset, 229 (u8 *) &hdr, sizeof(hdr)); 230 if (r != sizeof(hdr)) 231 return -EINVAL; 232 233 /* We dont need eh_frame_ptr, just skip it. */ 234 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); 235 236 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); 237 *segbase = offset; 238 *table_data = (enc - (u8 *) &hdr) + offset; 239 return 0; 240 } 241 242 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine, 243 u64 *table_data, u64 *segbase, 244 u64 *fde_count) 245 { 246 int ret = -EINVAL, fd; 247 u64 offset; 248 249 fd = dso__data_fd(dso, machine); 250 if (fd < 0) 251 return -EINVAL; 252 253 /* Check the .eh_frame section for unwinding info */ 254 offset = elf_section_offset(fd, ".eh_frame_hdr"); 255 256 if (offset) 257 ret = unwind_spec_ehframe(dso, machine, offset, 258 table_data, segbase, 259 fde_count); 260 261 return ret; 262 } 263 264 #ifndef NO_LIBUNWIND_DEBUG_FRAME 265 static int read_unwind_spec_debug_frame(struct dso *dso, 266 struct machine *machine, u64 *offset) 267 { 268 int fd = dso__data_fd(dso, machine); 269 270 if (fd < 0) 271 return -EINVAL; 272 273 /* Check the .debug_frame section for unwinding info */ 274 *offset = elf_section_offset(fd, ".debug_frame"); 275 276 if (*offset) 277 return 0; 278 279 return -EINVAL; 280 } 281 #endif 282 283 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 284 { 285 struct addr_location al; 286 287 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 288 MAP__FUNCTION, ip, &al); 289 return al.map; 290 } 291 292 static int 293 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 294 int need_unwind_info, void *arg) 295 { 296 struct unwind_info *ui = arg; 297 struct map *map; 298 unw_dyn_info_t di; 299 u64 table_data, segbase, fde_count; 300 301 map = find_map(ip, ui); 302 if (!map || !map->dso) 303 return -EINVAL; 304 305 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); 306 307 /* Check the .eh_frame section for unwinding info */ 308 if (!read_unwind_spec_eh_frame(map->dso, ui->machine, 309 &table_data, &segbase, &fde_count)) { 310 memset(&di, 0, sizeof(di)); 311 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 312 di.start_ip = map->start; 313 di.end_ip = map->end; 314 di.u.rti.segbase = map->start + segbase; 315 di.u.rti.table_data = map->start + table_data; 316 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 317 / sizeof(unw_word_t); 318 return dwarf_search_unwind_table(as, ip, &di, pi, 319 need_unwind_info, arg); 320 } 321 322 #ifndef NO_LIBUNWIND_DEBUG_FRAME 323 /* Check the .debug_frame section for unwinding info */ 324 if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) { 325 memset(&di, 0, sizeof(di)); 326 if (dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name, 327 map->start, map->end)) 328 return dwarf_search_unwind_table(as, ip, &di, pi, 329 need_unwind_info, arg); 330 } 331 #endif 332 333 return -EINVAL; 334 } 335 336 static int access_fpreg(unw_addr_space_t __maybe_unused as, 337 unw_regnum_t __maybe_unused num, 338 unw_fpreg_t __maybe_unused *val, 339 int __maybe_unused __write, 340 void __maybe_unused *arg) 341 { 342 pr_err("unwind: access_fpreg unsupported\n"); 343 return -UNW_EINVAL; 344 } 345 346 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 347 unw_word_t __maybe_unused *dil_addr, 348 void __maybe_unused *arg) 349 { 350 return -UNW_ENOINFO; 351 } 352 353 static int resume(unw_addr_space_t __maybe_unused as, 354 unw_cursor_t __maybe_unused *cu, 355 void __maybe_unused *arg) 356 { 357 pr_err("unwind: resume unsupported\n"); 358 return -UNW_EINVAL; 359 } 360 361 static int 362 get_proc_name(unw_addr_space_t __maybe_unused as, 363 unw_word_t __maybe_unused addr, 364 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 365 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 366 { 367 pr_err("unwind: get_proc_name unsupported\n"); 368 return -UNW_EINVAL; 369 } 370 371 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 372 unw_word_t *data) 373 { 374 struct addr_location al; 375 ssize_t size; 376 377 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER, 378 MAP__FUNCTION, addr, &al); 379 if (!al.map) { 380 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 381 return -1; 382 } 383 384 if (!al.map->dso) 385 return -1; 386 387 size = dso__data_read_addr(al.map->dso, al.map, ui->machine, 388 addr, (u8 *) data, sizeof(*data)); 389 390 return !(size == sizeof(*data)); 391 } 392 393 static int access_mem(unw_addr_space_t __maybe_unused as, 394 unw_word_t addr, unw_word_t *valp, 395 int __write, void *arg) 396 { 397 struct unwind_info *ui = arg; 398 struct stack_dump *stack = &ui->sample->user_stack; 399 u64 start, end; 400 int offset; 401 int ret; 402 403 /* Don't support write, probably not needed. */ 404 if (__write || !stack || !ui->sample->user_regs.regs) { 405 *valp = 0; 406 return 0; 407 } 408 409 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 410 if (ret) 411 return ret; 412 413 end = start + stack->size; 414 415 /* Check overflow. */ 416 if (addr + sizeof(unw_word_t) < addr) 417 return -EINVAL; 418 419 if (addr < start || addr + sizeof(unw_word_t) >= end) { 420 ret = access_dso_mem(ui, addr, valp); 421 if (ret) { 422 pr_debug("unwind: access_mem %p not inside range" 423 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 424 (void *) addr, start, end); 425 *valp = 0; 426 return ret; 427 } 428 return 0; 429 } 430 431 offset = addr - start; 432 *valp = *(unw_word_t *)&stack->data[offset]; 433 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 434 (void *) addr, (unsigned long)*valp, offset); 435 return 0; 436 } 437 438 static int access_reg(unw_addr_space_t __maybe_unused as, 439 unw_regnum_t regnum, unw_word_t *valp, 440 int __write, void *arg) 441 { 442 struct unwind_info *ui = arg; 443 int id, ret; 444 u64 val; 445 446 /* Don't support write, I suspect we don't need it. */ 447 if (__write) { 448 pr_err("unwind: access_reg w %d\n", regnum); 449 return 0; 450 } 451 452 if (!ui->sample->user_regs.regs) { 453 *valp = 0; 454 return 0; 455 } 456 457 id = libunwind__arch_reg_id(regnum); 458 if (id < 0) 459 return -EINVAL; 460 461 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 462 if (ret) { 463 pr_err("unwind: can't read reg %d\n", regnum); 464 return ret; 465 } 466 467 *valp = (unw_word_t) val; 468 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 469 return 0; 470 } 471 472 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 473 unw_proc_info_t *pi __maybe_unused, 474 void *arg __maybe_unused) 475 { 476 pr_debug("unwind: put_unwind_info called\n"); 477 } 478 479 static int entry(u64 ip, struct thread *thread, 480 unwind_entry_cb_t cb, void *arg) 481 { 482 struct unwind_entry e; 483 struct addr_location al; 484 485 thread__find_addr_location(thread, PERF_RECORD_MISC_USER, 486 MAP__FUNCTION, ip, &al); 487 488 e.ip = ip; 489 e.map = al.map; 490 e.sym = al.sym; 491 492 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 493 al.sym ? al.sym->name : "''", 494 ip, 495 al.map ? al.map->map_ip(al.map, ip) : (u64) 0); 496 497 return cb(&e, arg); 498 } 499 500 static void display_error(int err) 501 { 502 switch (err) { 503 case UNW_EINVAL: 504 pr_err("unwind: Only supports local.\n"); 505 break; 506 case UNW_EUNSPEC: 507 pr_err("unwind: Unspecified error.\n"); 508 break; 509 case UNW_EBADREG: 510 pr_err("unwind: Register unavailable.\n"); 511 break; 512 default: 513 break; 514 } 515 } 516 517 static unw_accessors_t accessors = { 518 .find_proc_info = find_proc_info, 519 .put_unwind_info = put_unwind_info, 520 .get_dyn_info_list_addr = get_dyn_info_list_addr, 521 .access_mem = access_mem, 522 .access_reg = access_reg, 523 .access_fpreg = access_fpreg, 524 .resume = resume, 525 .get_proc_name = get_proc_name, 526 }; 527 528 int unwind__prepare_access(struct thread *thread) 529 { 530 unw_addr_space_t addr_space; 531 532 if (callchain_param.record_mode != CALLCHAIN_DWARF) 533 return 0; 534 535 addr_space = unw_create_addr_space(&accessors, 0); 536 if (!addr_space) { 537 pr_err("unwind: Can't create unwind address space.\n"); 538 return -ENOMEM; 539 } 540 541 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL); 542 thread__set_priv(thread, addr_space); 543 544 return 0; 545 } 546 547 void unwind__flush_access(struct thread *thread) 548 { 549 unw_addr_space_t addr_space; 550 551 if (callchain_param.record_mode != CALLCHAIN_DWARF) 552 return; 553 554 addr_space = thread__priv(thread); 555 unw_flush_cache(addr_space, 0, 0); 556 } 557 558 void unwind__finish_access(struct thread *thread) 559 { 560 unw_addr_space_t addr_space; 561 562 if (callchain_param.record_mode != CALLCHAIN_DWARF) 563 return; 564 565 addr_space = thread__priv(thread); 566 unw_destroy_addr_space(addr_space); 567 } 568 569 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 570 void *arg, int max_stack) 571 { 572 unw_addr_space_t addr_space; 573 unw_cursor_t c; 574 int ret; 575 576 addr_space = thread__priv(ui->thread); 577 if (addr_space == NULL) 578 return -1; 579 580 ret = unw_init_remote(&c, addr_space, ui); 581 if (ret) 582 display_error(ret); 583 584 while (!ret && (unw_step(&c) > 0) && max_stack--) { 585 unw_word_t ip; 586 587 unw_get_reg(&c, UNW_REG_IP, &ip); 588 ret = ip ? entry(ip, ui->thread, cb, arg) : 0; 589 } 590 591 return ret; 592 } 593 594 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 595 struct machine *machine, struct thread *thread, 596 struct perf_sample *data, int max_stack) 597 { 598 u64 ip; 599 struct unwind_info ui = { 600 .sample = data, 601 .thread = thread, 602 .machine = machine, 603 }; 604 int ret; 605 606 if (!data->user_regs.regs) 607 return -EINVAL; 608 609 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP); 610 if (ret) 611 return ret; 612 613 ret = entry(ip, thread, cb, arg); 614 if (ret) 615 return -ENOMEM; 616 617 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0; 618 } 619