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 #include "debug.h" 34 35 extern int 36 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as, 37 unw_word_t ip, 38 unw_dyn_info_t *di, 39 unw_proc_info_t *pi, 40 int need_unwind_info, void *arg); 41 42 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table) 43 44 extern int 45 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug, 46 unw_word_t ip, 47 unw_word_t segbase, 48 const char *obj_name, unw_word_t start, 49 unw_word_t end); 50 51 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame) 52 53 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */ 54 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */ 55 56 /* Pointer-encoding formats: */ 57 #define DW_EH_PE_omit 0xff 58 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */ 59 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */ 60 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */ 61 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */ 62 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */ 63 64 /* Pointer-encoding application: */ 65 #define DW_EH_PE_absptr 0x00 /* absolute value */ 66 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */ 67 68 /* 69 * The following are not documented by LSB v1.3, yet they are used by 70 * GCC, presumably they aren't documented by LSB since they aren't 71 * used on Linux: 72 */ 73 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */ 74 #define DW_EH_PE_aligned 0x50 /* aligned pointer */ 75 76 /* Flags intentionaly not handled, since they're not needed: 77 * #define DW_EH_PE_indirect 0x80 78 * #define DW_EH_PE_uleb128 0x01 79 * #define DW_EH_PE_udata2 0x02 80 * #define DW_EH_PE_sleb128 0x09 81 * #define DW_EH_PE_sdata2 0x0a 82 * #define DW_EH_PE_textrel 0x20 83 * #define DW_EH_PE_datarel 0x30 84 */ 85 86 struct unwind_info { 87 struct perf_sample *sample; 88 struct machine *machine; 89 struct thread *thread; 90 }; 91 92 #define dw_read(ptr, type, end) ({ \ 93 type *__p = (type *) ptr; \ 94 type __v; \ 95 if ((__p + 1) > (type *) end) \ 96 return -EINVAL; \ 97 __v = *__p++; \ 98 ptr = (typeof(ptr)) __p; \ 99 __v; \ 100 }) 101 102 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, 103 u8 encoding) 104 { 105 u8 *cur = *p; 106 *val = 0; 107 108 switch (encoding) { 109 case DW_EH_PE_omit: 110 *val = 0; 111 goto out; 112 case DW_EH_PE_ptr: 113 *val = dw_read(cur, unsigned long, end); 114 goto out; 115 default: 116 break; 117 } 118 119 switch (encoding & DW_EH_PE_APPL_MASK) { 120 case DW_EH_PE_absptr: 121 break; 122 case DW_EH_PE_pcrel: 123 *val = (unsigned long) cur; 124 break; 125 default: 126 return -EINVAL; 127 } 128 129 if ((encoding & 0x07) == 0x00) 130 encoding |= DW_EH_PE_udata4; 131 132 switch (encoding & DW_EH_PE_FORMAT_MASK) { 133 case DW_EH_PE_sdata4: 134 *val += dw_read(cur, s32, end); 135 break; 136 case DW_EH_PE_udata4: 137 *val += dw_read(cur, u32, end); 138 break; 139 case DW_EH_PE_sdata8: 140 *val += dw_read(cur, s64, end); 141 break; 142 case DW_EH_PE_udata8: 143 *val += dw_read(cur, u64, end); 144 break; 145 default: 146 return -EINVAL; 147 } 148 149 out: 150 *p = cur; 151 return 0; 152 } 153 154 #define dw_read_encoded_value(ptr, end, enc) ({ \ 155 u64 __v; \ 156 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ 157 return -EINVAL; \ 158 } \ 159 __v; \ 160 }) 161 162 static u64 elf_section_offset(int fd, const char *name) 163 { 164 Elf *elf; 165 GElf_Ehdr ehdr; 166 GElf_Shdr shdr; 167 u64 offset = 0; 168 169 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); 170 if (elf == NULL) 171 return 0; 172 173 do { 174 if (gelf_getehdr(elf, &ehdr) == NULL) 175 break; 176 177 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL)) 178 break; 179 180 offset = shdr.sh_offset; 181 } while (0); 182 183 elf_end(elf); 184 return offset; 185 } 186 187 struct table_entry { 188 u32 start_ip_offset; 189 u32 fde_offset; 190 }; 191 192 struct eh_frame_hdr { 193 unsigned char version; 194 unsigned char eh_frame_ptr_enc; 195 unsigned char fde_count_enc; 196 unsigned char table_enc; 197 198 /* 199 * The rest of the header is variable-length and consists of the 200 * following members: 201 * 202 * encoded_t eh_frame_ptr; 203 * encoded_t fde_count; 204 */ 205 206 /* A single encoded pointer should not be more than 8 bytes. */ 207 u64 enc[2]; 208 209 /* 210 * struct { 211 * encoded_t start_ip; 212 * encoded_t fde_addr; 213 * } binary_search_table[fde_count]; 214 */ 215 char data[0]; 216 } __packed; 217 218 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, 219 u64 offset, u64 *table_data, u64 *segbase, 220 u64 *fde_count) 221 { 222 struct eh_frame_hdr hdr; 223 u8 *enc = (u8 *) &hdr.enc; 224 u8 *end = (u8 *) &hdr.data; 225 ssize_t r; 226 227 r = dso__data_read_offset(dso, machine, offset, 228 (u8 *) &hdr, sizeof(hdr)); 229 if (r != sizeof(hdr)) 230 return -EINVAL; 231 232 /* We dont need eh_frame_ptr, just skip it. */ 233 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); 234 235 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); 236 *segbase = offset; 237 *table_data = (enc - (u8 *) &hdr) + offset; 238 return 0; 239 } 240 241 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine, 242 u64 *table_data, u64 *segbase, 243 u64 *fde_count) 244 { 245 int ret = -EINVAL, fd; 246 u64 offset; 247 248 fd = dso__data_fd(dso, machine); 249 if (fd < 0) 250 return -EINVAL; 251 252 /* Check the .eh_frame section for unwinding info */ 253 offset = elf_section_offset(fd, ".eh_frame_hdr"); 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"); 274 275 if (*offset) 276 return 0; 277 278 return -EINVAL; 279 } 280 #endif 281 282 static struct map *find_map(unw_word_t ip, struct unwind_info *ui) 283 { 284 struct addr_location al; 285 286 thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, 287 MAP__FUNCTION, ip, &al); 288 return al.map; 289 } 290 291 static int 292 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, 293 int need_unwind_info, void *arg) 294 { 295 struct unwind_info *ui = arg; 296 struct map *map; 297 unw_dyn_info_t di; 298 u64 table_data, segbase, fde_count; 299 300 map = find_map(ip, ui); 301 if (!map || !map->dso) 302 return -EINVAL; 303 304 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); 305 306 /* Check the .eh_frame section for unwinding info */ 307 if (!read_unwind_spec_eh_frame(map->dso, ui->machine, 308 &table_data, &segbase, &fde_count)) { 309 memset(&di, 0, sizeof(di)); 310 di.format = UNW_INFO_FORMAT_REMOTE_TABLE; 311 di.start_ip = map->start; 312 di.end_ip = map->end; 313 di.u.rti.segbase = map->start + segbase; 314 di.u.rti.table_data = map->start + table_data; 315 di.u.rti.table_len = fde_count * sizeof(struct table_entry) 316 / sizeof(unw_word_t); 317 return dwarf_search_unwind_table(as, ip, &di, pi, 318 need_unwind_info, arg); 319 } 320 321 #ifndef NO_LIBUNWIND_DEBUG_FRAME 322 /* Check the .debug_frame section for unwinding info */ 323 if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) { 324 memset(&di, 0, sizeof(di)); 325 if (dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name, 326 map->start, map->end)) 327 return dwarf_search_unwind_table(as, ip, &di, pi, 328 need_unwind_info, arg); 329 } 330 #endif 331 332 return -EINVAL; 333 } 334 335 static int access_fpreg(unw_addr_space_t __maybe_unused as, 336 unw_regnum_t __maybe_unused num, 337 unw_fpreg_t __maybe_unused *val, 338 int __maybe_unused __write, 339 void __maybe_unused *arg) 340 { 341 pr_err("unwind: access_fpreg unsupported\n"); 342 return -UNW_EINVAL; 343 } 344 345 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, 346 unw_word_t __maybe_unused *dil_addr, 347 void __maybe_unused *arg) 348 { 349 return -UNW_ENOINFO; 350 } 351 352 static int resume(unw_addr_space_t __maybe_unused as, 353 unw_cursor_t __maybe_unused *cu, 354 void __maybe_unused *arg) 355 { 356 pr_err("unwind: resume unsupported\n"); 357 return -UNW_EINVAL; 358 } 359 360 static int 361 get_proc_name(unw_addr_space_t __maybe_unused as, 362 unw_word_t __maybe_unused addr, 363 char __maybe_unused *bufp, size_t __maybe_unused buf_len, 364 unw_word_t __maybe_unused *offp, void __maybe_unused *arg) 365 { 366 pr_err("unwind: get_proc_name unsupported\n"); 367 return -UNW_EINVAL; 368 } 369 370 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, 371 unw_word_t *data) 372 { 373 struct addr_location al; 374 ssize_t size; 375 376 thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, 377 MAP__FUNCTION, addr, &al); 378 if (!al.map) { 379 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 380 return -1; 381 } 382 383 if (!al.map->dso) 384 return -1; 385 386 size = dso__data_read_addr(al.map->dso, al.map, ui->machine, 387 addr, (u8 *) data, sizeof(*data)); 388 389 return !(size == sizeof(*data)); 390 } 391 392 static int access_mem(unw_addr_space_t __maybe_unused as, 393 unw_word_t addr, unw_word_t *valp, 394 int __write, void *arg) 395 { 396 struct unwind_info *ui = arg; 397 struct stack_dump *stack = &ui->sample->user_stack; 398 u64 start, end; 399 int offset; 400 int ret; 401 402 /* Don't support write, probably not needed. */ 403 if (__write || !stack || !ui->sample->user_regs.regs) { 404 *valp = 0; 405 return 0; 406 } 407 408 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 409 if (ret) 410 return ret; 411 412 end = start + stack->size; 413 414 /* Check overflow. */ 415 if (addr + sizeof(unw_word_t) < addr) 416 return -EINVAL; 417 418 if (addr < start || addr + sizeof(unw_word_t) >= end) { 419 ret = access_dso_mem(ui, addr, valp); 420 if (ret) { 421 pr_debug("unwind: access_mem %p not inside range" 422 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 423 (void *) addr, start, end); 424 *valp = 0; 425 return ret; 426 } 427 return 0; 428 } 429 430 offset = addr - start; 431 *valp = *(unw_word_t *)&stack->data[offset]; 432 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", 433 (void *) addr, (unsigned long)*valp, offset); 434 return 0; 435 } 436 437 static int access_reg(unw_addr_space_t __maybe_unused as, 438 unw_regnum_t regnum, unw_word_t *valp, 439 int __write, void *arg) 440 { 441 struct unwind_info *ui = arg; 442 int id, ret; 443 u64 val; 444 445 /* Don't support write, I suspect we don't need it. */ 446 if (__write) { 447 pr_err("unwind: access_reg w %d\n", regnum); 448 return 0; 449 } 450 451 if (!ui->sample->user_regs.regs) { 452 *valp = 0; 453 return 0; 454 } 455 456 id = libunwind__arch_reg_id(regnum); 457 if (id < 0) 458 return -EINVAL; 459 460 ret = perf_reg_value(&val, &ui->sample->user_regs, id); 461 if (ret) { 462 pr_err("unwind: can't read reg %d\n", regnum); 463 return ret; 464 } 465 466 *valp = (unw_word_t) val; 467 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); 468 return 0; 469 } 470 471 static void put_unwind_info(unw_addr_space_t __maybe_unused as, 472 unw_proc_info_t *pi __maybe_unused, 473 void *arg __maybe_unused) 474 { 475 pr_debug("unwind: put_unwind_info called\n"); 476 } 477 478 static int entry(u64 ip, struct thread *thread, struct machine *machine, 479 unwind_entry_cb_t cb, void *arg) 480 { 481 struct unwind_entry e; 482 struct addr_location al; 483 484 thread__find_addr_location(thread, machine, 485 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 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, 529 void *arg, int max_stack) 530 { 531 unw_addr_space_t addr_space; 532 unw_cursor_t c; 533 int ret; 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 ret = unw_init_remote(&c, addr_space, ui); 542 if (ret) 543 display_error(ret); 544 545 while (!ret && (unw_step(&c) > 0) && max_stack--) { 546 unw_word_t ip; 547 548 unw_get_reg(&c, UNW_REG_IP, &ip); 549 ret = ip ? entry(ip, ui->thread, ui->machine, cb, arg) : 0; 550 } 551 552 unw_destroy_addr_space(addr_space); 553 return ret; 554 } 555 556 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 557 struct machine *machine, struct thread *thread, 558 struct perf_sample *data, int max_stack) 559 { 560 u64 ip; 561 struct unwind_info ui = { 562 .sample = data, 563 .thread = thread, 564 .machine = machine, 565 }; 566 int ret; 567 568 if (!data->user_regs.regs) 569 return -EINVAL; 570 571 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP); 572 if (ret) 573 return ret; 574 575 ret = entry(ip, thread, machine, cb, arg); 576 if (ret) 577 return -ENOMEM; 578 579 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0; 580 } 581