tools/perf/util/unwind-libunwind.c

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