tools/perf/util/unwind.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 "thread.h"
  28 #include "session.h"
  29 #include "perf_regs.h"
  30 #include "unwind.h"
  31 #include "util.h"
  32
  33 extern int
  34 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
  35                                     unw_word_t ip,
  36                                     unw_dyn_info_t *di,
  37                                     unw_proc_info_t *pi,
  38                                     int need_unwind_info, void *arg);
  39
  40 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
  41
  42 extern int
  43 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
  44                                  unw_word_t ip,
  45                                  unw_word_t segbase,
  46                                  const char *obj_name, unw_word_t start,
  47                                  unw_word_t end);
  48
  49 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
  50
  51 #define DW_EH_PE_FORMAT_MASK    0x0f    /* format of the encoded value */
  52 #define DW_EH_PE_APPL_MASK      0x70    /* how the value is to be applied */
  53
  54 /* Pointer-encoding formats: */
  55 #define DW_EH_PE_omit           0xff
  56 #define DW_EH_PE_ptr            0x00    /* pointer-sized unsigned value */
  57 #define DW_EH_PE_udata4         0x03    /* unsigned 32-bit value */
  58 #define DW_EH_PE_udata8         0x04    /* unsigned 64-bit value */
  59 #define DW_EH_PE_sdata4         0x0b    /* signed 32-bit value */
  60 #define DW_EH_PE_sdata8         0x0c    /* signed 64-bit value */
  61
  62 /* Pointer-encoding application: */
  63 #define DW_EH_PE_absptr         0x00    /* absolute value */
  64 #define DW_EH_PE_pcrel          0x10    /* rel. to addr. of encoded value */
  65
  66 /*
  67  * The following are not documented by LSB v1.3, yet they are used by
  68  * GCC, presumably they aren't documented by LSB since they aren't
  69  * used on Linux:
  70  */
  71 #define DW_EH_PE_funcrel        0x40    /* start-of-procedure-relative */
  72 #define DW_EH_PE_aligned        0x50    /* aligned pointer */
  73
  74 /* Flags intentionaly not handled, since they're not needed:
  75  * #define DW_EH_PE_indirect      0x80
  76  * #define DW_EH_PE_uleb128       0x01
  77  * #define DW_EH_PE_udata2        0x02
  78  * #define DW_EH_PE_sleb128       0x09
  79  * #define DW_EH_PE_sdata2        0x0a
  80  * #define DW_EH_PE_textrel       0x20
  81  * #define DW_EH_PE_datarel       0x30
  82  */
  83
  84 struct unwind_info {
  85         struct perf_sample      *sample;
  86         struct machine          *machine;
  87         struct thread           *thread;
  88         u64                     sample_uregs;
  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 Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
 162                                     GElf_Shdr *shp, const char *name)
 163 {
 164         Elf_Scn *sec = NULL;
 165
 166         while ((sec = elf_nextscn(elf, sec)) != NULL) {
 167                 char *str;
 168
 169                 gelf_getshdr(sec, shp);
 170                 str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
 171                 if (!strcmp(name, str))
 172                         break;
 173         }
 174
 175         return sec;
 176 }
 177
 178 static u64 elf_section_offset(int fd, const char *name)
 179 {
 180         Elf *elf;
 181         GElf_Ehdr ehdr;
 182         GElf_Shdr shdr;
 183         u64 offset = 0;
 184
 185         elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 186         if (elf == NULL)
 187                 return 0;
 188
 189         do {
 190                 if (gelf_getehdr(elf, &ehdr) == NULL)
 191                         break;
 192
 193                 if (!elf_section_by_name(elf, &ehdr, &shdr, name))
 194                         break;
 195
 196                 offset = shdr.sh_offset;
 197         } while (0);
 198
 199         elf_end(elf);
 200         return offset;
 201 }
 202
 203 struct table_entry {
 204         u32 start_ip_offset;
 205         u32 fde_offset;
 206 };
 207
 208 struct eh_frame_hdr {
 209         unsigned char version;
 210         unsigned char eh_frame_ptr_enc;
 211         unsigned char fde_count_enc;
 212         unsigned char table_enc;
 213
 214         /*
 215          * The rest of the header is variable-length and consists of the
 216          * following members:
 217          *
 218          *      encoded_t eh_frame_ptr;
 219          *      encoded_t fde_count;
 220          */
 221
 222         /* A single encoded pointer should not be more than 8 bytes. */
 223         u64 enc[2];
 224
 225         /*
 226          * struct {
 227          *    encoded_t start_ip;
 228          *    encoded_t fde_addr;
 229          * } binary_search_table[fde_count];
 230          */
 231         char data[0];
 232 } __packed;
 233
 234 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
 235                                u64 offset, u64 *table_data, u64 *segbase,
 236                                u64 *fde_count)
 237 {
 238         struct eh_frame_hdr hdr;
 239         u8 *enc = (u8 *) &hdr.enc;
 240         u8 *end = (u8 *) &hdr.data;
 241         ssize_t r;
 242
 243         r = dso__data_read_offset(dso, machine, offset,
 244                                   (u8 *) &hdr, sizeof(hdr));
 245         if (r != sizeof(hdr))
 246                 return -EINVAL;
 247
 248         /* We dont need eh_frame_ptr, just skip it. */
 249         dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 250
 251         *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
 252         *segbase    = offset;
 253         *table_data = (enc - (u8 *) &hdr) + offset;
 254         return 0;
 255 }
 256
 257 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
 258                                      u64 *table_data, u64 *segbase,
 259                                      u64 *fde_count)
 260 {
 261         int ret = -EINVAL, fd;
 262         u64 offset;
 263
 264         fd = dso__data_fd(dso, machine);
 265         if (fd < 0)
 266                 return -EINVAL;
 267
 268         /* Check the .eh_frame section for unwinding info */
 269         offset = elf_section_offset(fd, ".eh_frame_hdr");
 270         close(fd);
 271
 272         if (offset)
 273                 ret = unwind_spec_ehframe(dso, machine, offset,
 274                                           table_data, segbase,
 275                                           fde_count);
 276
 277         return ret;
 278 }
 279
 280 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 281 static int read_unwind_spec_debug_frame(struct dso *dso,
 282                                         struct machine *machine, u64 *offset)
 283 {
 284         int fd = dso__data_fd(dso, machine);
 285
 286         if (fd < 0)
 287                 return -EINVAL;
 288
 289         /* Check the .debug_frame section for unwinding info */
 290         *offset = elf_section_offset(fd, ".debug_frame");
 291         close(fd);
 292
 293         if (*offset)
 294                 return 0;
 295
 296         return -EINVAL;
 297 }
 298 #endif
 299
 300 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
 301 {
 302         struct addr_location al;
 303
 304         thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
 305                               MAP__FUNCTION, ip, &al);
 306         return al.map;
 307 }
 308
 309 static int
 310 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 311                int need_unwind_info, void *arg)
 312 {
 313         struct unwind_info *ui = arg;
 314         struct map *map;
 315         unw_dyn_info_t di;
 316         u64 table_data, segbase, fde_count;
 317
 318         map = find_map(ip, ui);
 319         if (!map || !map->dso)
 320                 return -EINVAL;
 321
 322         pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 323
 324         /* Check the .eh_frame section for unwinding info */
 325         if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
 326                                        &table_data, &segbase, &fde_count)) {
 327                 memset(&di, 0, sizeof(di));
 328                 di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 329                 di.start_ip = map->start;
 330                 di.end_ip   = map->end;
 331                 di.u.rti.segbase    = map->start + segbase;
 332                 di.u.rti.table_data = map->start + table_data;
 333                 di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 334                                       / sizeof(unw_word_t);
 335                 return dwarf_search_unwind_table(as, ip, &di, pi,
 336                                                  need_unwind_info, arg);
 337         }
 338
 339 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 340         /* Check the .debug_frame section for unwinding info */
 341         if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
 342                 memset(&di, 0, sizeof(di));
 343                 dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name,
 344                                        map->start, map->end);
 345                 return dwarf_search_unwind_table(as, ip, &di, pi,
 346                                                  need_unwind_info, arg);
 347         }
 348 #endif
 349
 350         return -EINVAL;
 351 }
 352
 353 static int access_fpreg(unw_addr_space_t __maybe_unused as,
 354                         unw_regnum_t __maybe_unused num,
 355                         unw_fpreg_t __maybe_unused *val,
 356                         int __maybe_unused __write,
 357                         void __maybe_unused *arg)
 358 {
 359         pr_err("unwind: access_fpreg unsupported\n");
 360         return -UNW_EINVAL;
 361 }
 362
 363 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
 364                                   unw_word_t __maybe_unused *dil_addr,
 365                                   void __maybe_unused *arg)
 366 {
 367         return -UNW_ENOINFO;
 368 }
 369
 370 static int resume(unw_addr_space_t __maybe_unused as,
 371                   unw_cursor_t __maybe_unused *cu,
 372                   void __maybe_unused *arg)
 373 {
 374         pr_err("unwind: resume unsupported\n");
 375         return -UNW_EINVAL;
 376 }
 377
 378 static int
 379 get_proc_name(unw_addr_space_t __maybe_unused as,
 380               unw_word_t __maybe_unused addr,
 381                 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
 382                 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
 383 {
 384         pr_err("unwind: get_proc_name unsupported\n");
 385         return -UNW_EINVAL;
 386 }
 387
 388 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
 389                           unw_word_t *data)
 390 {
 391         struct addr_location al;
 392         ssize_t size;
 393
 394         thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
 395                               MAP__FUNCTION, addr, &al);
 396         if (!al.map) {
 397                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 398                 return -1;
 399         }
 400
 401         if (!al.map->dso)
 402                 return -1;
 403
 404         size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
 405                                    addr, (u8 *) data, sizeof(*data));
 406
 407         return !(size == sizeof(*data));
 408 }
 409
 410 static int reg_value(unw_word_t *valp, struct regs_dump *regs, int id,
 411                      u64 sample_regs)
 412 {
 413         int i, idx = 0;
 414
 415         if (!(sample_regs & (1 << id)))
 416                 return -EINVAL;
 417
 418         for (i = 0; i < id; i++) {
 419                 if (sample_regs & (1 << i))
 420                         idx++;
 421         }
 422
 423         *valp = regs->regs[idx];
 424         return 0;
 425 }
 426
 427 static int access_mem(unw_addr_space_t __maybe_unused as,
 428                       unw_word_t addr, unw_word_t *valp,
 429                       int __write, void *arg)
 430 {
 431         struct unwind_info *ui = arg;
 432         struct stack_dump *stack = &ui->sample->user_stack;
 433         unw_word_t start, end;
 434         int offset;
 435         int ret;
 436
 437         /* Don't support write, probably not needed. */
 438         if (__write || !stack || !ui->sample->user_regs.regs) {
 439                 *valp = 0;
 440                 return 0;
 441         }
 442
 443         ret = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP,
 444                         ui->sample_uregs);
 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 %p-%p\n",
 458                                 (void *)addr, (void *)start, (void *)end);
 459                         *valp = 0;
 460                         return ret;
 461                 }
 462                 return 0;
 463         }
 464
 465         offset = addr - start;
 466         *valp  = *(unw_word_t *)&stack->data[offset];
 467         pr_debug("unwind: access_mem addr %p, val %lx, offset %d\n",
 468                  (void *)addr, (unsigned long)*valp, offset);
 469         return 0;
 470 }
 471
 472 static int access_reg(unw_addr_space_t __maybe_unused as,
 473                       unw_regnum_t regnum, unw_word_t *valp,
 474                       int __write, void *arg)
 475 {
 476         struct unwind_info *ui = arg;
 477         int id, ret;
 478
 479         /* Don't support write, I suspect we don't need it. */
 480         if (__write) {
 481                 pr_err("unwind: access_reg w %d\n", regnum);
 482                 return 0;
 483         }
 484
 485         if (!ui->sample->user_regs.regs) {
 486                 *valp = 0;
 487                 return 0;
 488         }
 489
 490         id = unwind__arch_reg_id(regnum);
 491         if (id < 0)
 492                 return -EINVAL;
 493
 494         ret = reg_value(valp, &ui->sample->user_regs, id, ui->sample_uregs);
 495         if (ret) {
 496                 pr_err("unwind: can't read reg %d\n", regnum);
 497                 return ret;
 498         }
 499
 500         pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
 501         return 0;
 502 }
 503
 504 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
 505                             unw_proc_info_t *pi __maybe_unused,
 506                             void *arg __maybe_unused)
 507 {
 508         pr_debug("unwind: put_unwind_info called\n");
 509 }
 510
 511 static int entry(u64 ip, struct thread *thread, struct machine *machine,
 512                  unwind_entry_cb_t cb, void *arg)
 513 {
 514         struct unwind_entry e;
 515         struct addr_location al;
 516
 517         thread__find_addr_location(thread, machine,
 518                                    PERF_RECORD_MISC_USER,
 519                                    MAP__FUNCTION, ip, &al);
 520
 521         e.ip = ip;
 522         e.map = al.map;
 523         e.sym = al.sym;
 524
 525         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 526                  al.sym ? al.sym->name : "''",
 527                  ip,
 528                  al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
 529
 530         return cb(&e, arg);
 531 }
 532
 533 static void display_error(int err)
 534 {
 535         switch (err) {
 536         case UNW_EINVAL:
 537                 pr_err("unwind: Only supports local.\n");
 538                 break;
 539         case UNW_EUNSPEC:
 540                 pr_err("unwind: Unspecified error.\n");
 541                 break;
 542         case UNW_EBADREG:
 543                 pr_err("unwind: Register unavailable.\n");
 544                 break;
 545         default:
 546                 break;
 547         }
 548 }
 549
 550 static unw_accessors_t accessors = {
 551         .find_proc_info         = find_proc_info,
 552         .put_unwind_info        = put_unwind_info,
 553         .get_dyn_info_list_addr = get_dyn_info_list_addr,
 554         .access_mem             = access_mem,
 555         .access_reg             = access_reg,
 556         .access_fpreg           = access_fpreg,
 557         .resume                 = resume,
 558         .get_proc_name          = get_proc_name,
 559 };
 560
 561 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 562                        void *arg)
 563 {
 564         unw_addr_space_t addr_space;
 565         unw_cursor_t c;
 566         int ret;
 567
 568         addr_space = unw_create_addr_space(&accessors, 0);
 569         if (!addr_space) {
 570                 pr_err("unwind: Can't create unwind address space.\n");
 571                 return -ENOMEM;
 572         }
 573
 574         ret = unw_init_remote(&c, addr_space, ui);
 575         if (ret)
 576                 display_error(ret);
 577
 578         while (!ret && (unw_step(&c) > 0)) {
 579                 unw_word_t ip;
 580
 581                 unw_get_reg(&c, UNW_REG_IP, &ip);
 582                 ret = entry(ip, ui->thread, ui->machine, cb, arg);
 583         }
 584
 585         unw_destroy_addr_space(addr_space);
 586         return ret;
 587 }
 588
 589 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 590                         struct machine *machine, struct thread *thread,
 591                         u64 sample_uregs, struct perf_sample *data)
 592 {
 593         unw_word_t ip;
 594         struct unwind_info ui = {
 595                 .sample       = data,
 596                 .sample_uregs = sample_uregs,
 597                 .thread       = thread,
 598                 .machine      = machine,
 599         };
 600         int ret;
 601
 602         if (!data->user_regs.regs)
 603                 return -EINVAL;
 604
 605         ret = reg_value(&ip, &data->user_regs, PERF_REG_IP, sample_uregs);
 606         if (ret)
 607                 return ret;
 608
 609         ret = entry(ip, thread, machine, cb, arg);
 610         if (ret)
 611                 return -ENOMEM;
 612
 613         return get_entries(&ui, cb, arg);
 614 }