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 "thread.h" 28 #include "session.h" 29 #include "perf_regs.h" 30 #include "unwind.h" 31 #include "symbol.h" 32 #include "util.h" 33 34 extern int 35 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as, 36 unw_word_t ip, 37 unw_dyn_info_t *di, 38 unw_proc_info_t *pi, 39 int need_unwind_info, void *arg); 40 41 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table) 42 43 extern int 44 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug, 45 unw_word_t ip, 46 unw_word_t segbase, 47 const char *obj_name, unw_word_t start, 48 unw_word_t end); 49 50 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame) 51 52 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */ 53 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */ 54 55 /* Pointer-encoding formats: */ 56 #define DW_EH_PE_omit 0xff 57 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */ 58 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */ 59 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */ 60 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */ 61 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */ 62 63 /* Pointer-encoding application: */ 64 #define DW_EH_PE_absptr 0x00 /* absolute value */ 65 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */ 66 67 /* 68 * The following are not documented by LSB v1.3, yet they are used by 69 * GCC, presumably they aren't documented by LSB since they aren't 70 * used on Linux: 71 */ 72 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */ 73 #define DW_EH_PE_aligned 0x50 /* aligned pointer */ 74 75 /* Flags intentionaly not handled, since they're not needed: 76 * #define DW_EH_PE_indirect 0x80 77 * #define DW_EH_PE_uleb128 0x01 78 * #define DW_EH_PE_udata2 0x02 79 * #define DW_EH_PE_sleb128 0x09 80 * #define DW_EH_PE_sdata2 0x0a 81 * #define DW_EH_PE_textrel 0x20 82 * #define DW_EH_PE_datarel 0x30 83 */ 84 85 struct unwind_info { 86 struct perf_sample *sample; 87 struct machine *machine; 88 struct thread *thread; 89 }; 90 91 #define dw_read(ptr, type, end) ({ \ 92 type *__p = (type *) ptr; \ 93 type __v; \ 94 if ((__p + 1) > (type *) end) \ 95 return -EINVAL; \ 96 __v = *__p++; \ 97 ptr = (typeof(ptr)) __p; \ 98 __v; \ 99 }) 100 101 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, 102 u8 encoding) 103 { 104 u8 *cur = *p; 105 *val = 0; 106 107 switch (encoding) { 108 case DW_EH_PE_omit: 109 *val = 0; 110 goto out; 111 case DW_EH_PE_ptr: 112 *val = dw_read(cur, unsigned long, end); 113 goto out; 114 default: 115 break; 116 } 117 118 switch (encoding & DW_EH_PE_APPL_MASK) { 119 case DW_EH_PE_absptr: 120 break; 121 case DW_EH_PE_pcrel: 122 *val = (unsigned long) cur; 123 break; 124 default: 125 return -EINVAL; 126 } 127 128 if ((encoding & 0x07) == 0x00) 129 encoding |= DW_EH_PE_udata4; 130 131 switch (encoding & DW_EH_PE_FORMAT_MASK) { 132 case DW_EH_PE_sdata4: 133 *val += dw_read(cur, s32, end); 134 break; 135 case DW_EH_PE_udata4: 136 *val += dw_read(cur, u32, end); 137 break; 138 case DW_EH_PE_sdata8: 139 *val += dw_read(cur, s64, end); 140 break; 141 case DW_EH_PE_udata8: 142 *val += dw_read(cur, u64, end); 143 break; 144 default: 145 return -EINVAL; 146 } 147 148 out: 149 *p = cur; 150 return 0; 151 } 152 153 #define dw_read_encoded_value(ptr, end, enc) ({ \ 154 u64 __v; \ 155 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ 156 return -EINVAL; \ 157 } \ 158 __v; \ 159 }) 160 161 static u64 elf_section_offset(int fd, const char *name) 162 { 163 Elf *elf; 164 GElf_Ehdr ehdr; 165 GElf_Shdr shdr; 166 u64 offset = 0; 167 168 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 169 if (elf == NULL) 170 return 0; 171 172 do { 173 if (gelf_getehdr(elf, &ehdr) == NULL) 174 break; 175 176 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL)) 177 break; 178 179 offset = shdr.sh_offset; 180 } while (0); 181 182 elf_end(elf); 183 return offset; 184 } 185 186 struct table_entry { 187 u32 start_ip_offset; 188 u32 fde_offset; 189 }; 190 191 struct eh_frame_hdr { 192 unsigned char version; 193 unsigned char eh_frame_ptr_enc; 194 unsigned char fde_count_enc; 195 unsigned char table_enc; 196 197 /* 198 * The rest of the header is variable-length and consists of the 199 * following members: 200 * 201 * encoded_t eh_frame_ptr; 202 * encoded_t fde_count; 203 */ 204 205 /* A single encoded pointer should not be more than 8 bytes. */ 206 u64 enc[2]; 207 208 /* 209 * struct { 210 * encoded_t start_ip; 211 * encoded_t fde_addr; 212 * } binary_search_table[fde_count]; 213 */ 214 char data[0]; 215 } __packed; 216 217 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, 218 u64 offset, u64 *table_data, u64 *segbase, 219 u64 *fde_count) 220 { 221 struct eh_frame_hdr hdr; 222 u8 *enc = (u8 *) &hdr.enc; 223 u8 *end = (u8 *) &hdr.data; 224 ssize_t r; 225 226 r = dso__data_read_offset(dso, machine, offset, 227 (u8 *) &hdr, sizeof(hdr)); 228 if (r != sizeof(hdr)) 229 return -EINVAL; 230 231 /* We dont need eh_frame_ptr, just skip it. */ 232 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); 233 234 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); 235 *segbase = offset; 236 *table_data = (enc - (u8 *) &hdr) + offset; 237 return 0; 238 } 239 240 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine, 241 u64 *table_data, u64 *segbase, 242 u64 *fde_count) 243 { 244 int ret = -EINVAL, fd; 245 u64 offset; 246 247 fd = dso__data_fd(dso, machine); 248 if (fd < 0) 249 return -EINVAL; 250 251 /* Check the .eh_frame section for unwinding info */ 252 offset = elf_section_offset(fd, ".eh_frame_hdr"); 253 close(fd); 254 255 if (offset) 256 ret = unwind_spec_ehframe(dso, machine, offset, 257 table_data, segbase, 258 fde_count); 259 260 return ret; 261 } 262 263 #ifndef NO_LIBUNWIND_DEBUG_FRAME 264 static int read_unwind_spec_debug_frame(struct dso *dso, 265 struct machine *machine, u64 *offset) 266 { 267 int fd = dso__data_fd(dso, machine); 268 269 if (fd < 0) 270 return -EINVAL; 271 272 /* Check the .debug_frame section for unwinding info */ 273 *offset = elf_section_offset(fd, ".debug_frame"); 274 close(fd); 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, ui->machine, 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, ui->machine, 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 reg_value(unw_word_t *valp, struct regs_dump *regs, int id) 394 { 395 int i, idx = 0; 396 u64 mask = regs->mask; 397 398 if (!(mask & (1 << id))) 399 return -EINVAL; 400 401 for (i = 0; i < id; i++) { 402 if (mask & (1 << i)) 403 idx++; 404 } 405 406 *valp = regs->regs[idx]; 407 return 0; 408 } 409 410 static int access_mem(unw_addr_space_t __maybe_unused as, 411 unw_word_t addr, unw_word_t *valp, 412 int __write, void *arg) 413 { 414 struct unwind_info *ui = arg; 415 struct stack_dump *stack = &ui->sample->user_stack; 416 unw_word_t start, end; 417 int offset; 418 int ret; 419 420 /* Don't support write, probably not needed. */ 421 if (__write || !stack || !ui->sample->user_regs.regs) { 422 *valp = 0; 423 return 0; 424 } 425 426 ret = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 427 if (ret) 428 return ret; 429 430 end = start + stack->size; 431 432 /* Check overflow. */ 433 if (addr + sizeof(unw_word_t) < addr) 434 return -EINVAL; 435 436 if (addr < start || addr + sizeof(unw_word_t) >= end) { 437 ret = access_dso_mem(ui, addr, valp); 438 if (ret) { 439 pr_debug("unwind: access_mem %p not inside range %p-%p\n", 440 (void *)addr, (void *)start, (void *)end); 441 *valp = 0; 442 return ret; 443 } 444 return 0; 445 } 446 447 offset = addr - start; 448 *valp = *(unw_word_t *)&stack->data[offset]; 449 pr_debug("unwind: access_mem addr %p, val %lx, offset %d\n", 450 (void *)addr, (unsigned long)*valp, offset); 451 return 0; 452 } 453 454 static int access_reg(unw_addr_space_t __maybe_unused as, 455 unw_regnum_t regnum, unw_word_t *valp, 456 int __write, void *arg) 457 { 458 struct unwind_info *ui = arg; 459 int id, ret; 460 461 /* Don't support write, I suspect we don't need it. */ 462 if (__write) { 463 pr_err("unwind: access_reg w %d\n", regnum); 464 return 0; 465 } 466 467 if (!ui->sample->user_regs.regs) { 468 *valp = 0; 469 return 0; 470 } 471 472 id = unwind__arch_reg_id(regnum); 473 if (id < 0) 474 return -EINVAL; 475 476 ret = reg_value(valp, &ui->sample->user_regs, id); 477 if (ret) { 478 pr_err("unwind: can't read reg %d\n", regnum); 479 return ret; 480 } 481 482 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 483 return 0; 484 } 485 486 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 487 unw_proc_info_t *pi __maybe_unused, 488 void *arg __maybe_unused) 489 { 490 pr_debug("unwind: put_unwind_info called\n"); 491 } 492 493 static int entry(u64 ip, struct thread *thread, struct machine *machine, 494 unwind_entry_cb_t cb, void *arg) 495 { 496 struct unwind_entry e; 497 struct addr_location al; 498 499 thread__find_addr_location(thread, machine, 500 PERF_RECORD_MISC_USER, 501 MAP__FUNCTION, ip, &al); 502 503 e.ip = ip; 504 e.map = al.map; 505 e.sym = al.sym; 506 507 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 508 al.sym ? al.sym->name : "''", 509 ip, 510 al.map ? al.map->map_ip(al.map, ip) : (u64) 0); 511 512 return cb(&e, arg); 513 } 514 515 static void display_error(int err) 516 { 517 switch (err) { 518 case UNW_EINVAL: 519 pr_err("unwind: Only supports local.\n"); 520 break; 521 case UNW_EUNSPEC: 522 pr_err("unwind: Unspecified error.\n"); 523 break; 524 case UNW_EBADREG: 525 pr_err("unwind: Register unavailable.\n"); 526 break; 527 default: 528 break; 529 } 530 } 531 532 static unw_accessors_t accessors = { 533 .find_proc_info = find_proc_info, 534 .put_unwind_info = put_unwind_info, 535 .get_dyn_info_list_addr = get_dyn_info_list_addr, 536 .access_mem = access_mem, 537 .access_reg = access_reg, 538 .access_fpreg = access_fpreg, 539 .resume = resume, 540 .get_proc_name = get_proc_name, 541 }; 542 543 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 544 void *arg, int max_stack) 545 { 546 unw_addr_space_t addr_space; 547 unw_cursor_t c; 548 int ret; 549 550 addr_space = unw_create_addr_space(&accessors, 0); 551 if (!addr_space) { 552 pr_err("unwind: Can't create unwind address space.\n"); 553 return -ENOMEM; 554 } 555 556 ret = unw_init_remote(&c, addr_space, ui); 557 if (ret) 558 display_error(ret); 559 560 while (!ret && (unw_step(&c) > 0) && max_stack--) { 561 unw_word_t ip; 562 563 unw_get_reg(&c, UNW_REG_IP, &ip); 564 ret = ip ? entry(ip, ui->thread, ui->machine, cb, arg) : 0; 565 } 566 567 unw_destroy_addr_space(addr_space); 568 return ret; 569 } 570 571 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 572 struct machine *machine, struct thread *thread, 573 struct perf_sample *data, int max_stack) 574 { 575 unw_word_t ip; 576 struct unwind_info ui = { 577 .sample = data, 578 .thread = thread, 579 .machine = machine, 580 }; 581 int ret; 582 583 if (!data->user_regs.regs) 584 return -EINVAL; 585 586 ret = reg_value(&ip, &data->user_regs, PERF_REG_IP); 587 if (ret) 588 return ret; 589 590 ret = entry(ip, thread, machine, cb, arg); 591 if (ret) 592 return -ENOMEM; 593 594 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0; 595 } 596