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