tools/perf/util/unwind-libunwind-local.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 #ifndef REMOTE_UNWIND_LIBUNWIND
  26 #include <libunwind.h>
  27 #include <libunwind-ptrace.h>
  28 #endif
  29 #include "callchain.h"
  30 #include "thread.h"
  31 #include "session.h"
  32 #include "perf_regs.h"
  33 #include "unwind.h"
  34 #include "symbol.h"
  35 #include "util.h"
  36 #include "debug.h"
  37 #include "asm/bug.h"
  38 #include "dso.h"
  39
  40 extern int
  41 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
  42                                     unw_word_t ip,
  43                                     unw_dyn_info_t *di,
  44                                     unw_proc_info_t *pi,
  45                                     int need_unwind_info, void *arg);
  46
  47 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
  48
  49 extern int
  50 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
  51                                  unw_word_t ip,
  52                                  unw_word_t segbase,
  53                                  const char *obj_name, unw_word_t start,
  54                                  unw_word_t end);
  55
  56 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
  57
  58 #define DW_EH_PE_FORMAT_MASK    0x0f    /* format of the encoded value */
  59 #define DW_EH_PE_APPL_MASK      0x70    /* how the value is to be applied */
  60
  61 /* Pointer-encoding formats: */
  62 #define DW_EH_PE_omit           0xff
  63 #define DW_EH_PE_ptr            0x00    /* pointer-sized unsigned value */
  64 #define DW_EH_PE_udata4         0x03    /* unsigned 32-bit value */
  65 #define DW_EH_PE_udata8         0x04    /* unsigned 64-bit value */
  66 #define DW_EH_PE_sdata4         0x0b    /* signed 32-bit value */
  67 #define DW_EH_PE_sdata8         0x0c    /* signed 64-bit value */
  68
  69 /* Pointer-encoding application: */
  70 #define DW_EH_PE_absptr         0x00    /* absolute value */
  71 #define DW_EH_PE_pcrel          0x10    /* rel. to addr. of encoded value */
  72
  73 /*
  74  * The following are not documented by LSB v1.3, yet they are used by
  75  * GCC, presumably they aren't documented by LSB since they aren't
  76  * used on Linux:
  77  */
  78 #define DW_EH_PE_funcrel        0x40    /* start-of-procedure-relative */
  79 #define DW_EH_PE_aligned        0x50    /* aligned pointer */
  80
  81 /* Flags intentionaly not handled, since they're not needed:
  82  * #define DW_EH_PE_indirect      0x80
  83  * #define DW_EH_PE_uleb128       0x01
  84  * #define DW_EH_PE_udata2        0x02
  85  * #define DW_EH_PE_sleb128       0x09
  86  * #define DW_EH_PE_sdata2        0x0a
  87  * #define DW_EH_PE_textrel       0x20
  88  * #define DW_EH_PE_datarel       0x30
  89  */
  90
  91 struct unwind_info {
  92         struct perf_sample      *sample;
  93         struct machine          *machine;
  94         struct thread           *thread;
  95 };
  96
  97 #define dw_read(ptr, type, end) ({      \
  98         type *__p = (type *) ptr;       \
  99         type  __v;                      \
 100         if ((__p + 1) > (type *) end)   \
 101                 return -EINVAL;         \
 102         __v = *__p++;                   \
 103         ptr = (typeof(ptr)) __p;        \
 104         __v;                            \
 105         })
 106
 107 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
 108                                    u8 encoding)
 109 {
 110         u8 *cur = *p;
 111         *val = 0;
 112
 113         switch (encoding) {
 114         case DW_EH_PE_omit:
 115                 *val = 0;
 116                 goto out;
 117         case DW_EH_PE_ptr:
 118                 *val = dw_read(cur, unsigned long, end);
 119                 goto out;
 120         default:
 121                 break;
 122         }
 123
 124         switch (encoding & DW_EH_PE_APPL_MASK) {
 125         case DW_EH_PE_absptr:
 126                 break;
 127         case DW_EH_PE_pcrel:
 128                 *val = (unsigned long) cur;
 129                 break;
 130         default:
 131                 return -EINVAL;
 132         }
 133
 134         if ((encoding & 0x07) == 0x00)
 135                 encoding |= DW_EH_PE_udata4;
 136
 137         switch (encoding & DW_EH_PE_FORMAT_MASK) {
 138         case DW_EH_PE_sdata4:
 139                 *val += dw_read(cur, s32, end);
 140                 break;
 141         case DW_EH_PE_udata4:
 142                 *val += dw_read(cur, u32, end);
 143                 break;
 144         case DW_EH_PE_sdata8:
 145                 *val += dw_read(cur, s64, end);
 146                 break;
 147         case DW_EH_PE_udata8:
 148                 *val += dw_read(cur, u64, end);
 149                 break;
 150         default:
 151                 return -EINVAL;
 152         }
 153
 154  out:
 155         *p = cur;
 156         return 0;
 157 }
 158
 159 #define dw_read_encoded_value(ptr, end, enc) ({                 \
 160         u64 __v;                                                \
 161         if (__dw_read_encoded_value(&ptr, end, &__v, enc)) {    \
 162                 return -EINVAL;                                 \
 163         }                                                       \
 164         __v;                                                    \
 165         })
 166
 167 static u64 elf_section_offset(int fd, const char *name)
 168 {
 169         Elf *elf;
 170         GElf_Ehdr ehdr;
 171         GElf_Shdr shdr;
 172         u64 offset = 0;
 173
 174         elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 175         if (elf == NULL)
 176                 return 0;
 177
 178         do {
 179                 if (gelf_getehdr(elf, &ehdr) == NULL)
 180                         break;
 181
 182                 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
 183                         break;
 184
 185                 offset = shdr.sh_offset;
 186         } while (0);
 187
 188         elf_end(elf);
 189         return offset;
 190 }
 191
 192 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 193 static int elf_is_exec(int fd, const char *name)
 194 {
 195         Elf *elf;
 196         GElf_Ehdr ehdr;
 197         int retval = 0;
 198
 199         elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 200         if (elf == NULL)
 201                 return 0;
 202         if (gelf_getehdr(elf, &ehdr) == NULL)
 203                 goto out;
 204
 205         retval = (ehdr.e_type == ET_EXEC);
 206
 207 out:
 208         elf_end(elf);
 209         pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
 210         return retval;
 211 }
 212 #endif
 213
 214 struct table_entry {
 215         u32 start_ip_offset;
 216         u32 fde_offset;
 217 };
 218
 219 struct eh_frame_hdr {
 220         unsigned char version;
 221         unsigned char eh_frame_ptr_enc;
 222         unsigned char fde_count_enc;
 223         unsigned char table_enc;
 224
 225         /*
 226          * The rest of the header is variable-length and consists of the
 227          * following members:
 228          *
 229          *      encoded_t eh_frame_ptr;
 230          *      encoded_t fde_count;
 231          */
 232
 233         /* A single encoded pointer should not be more than 8 bytes. */
 234         u64 enc[2];
 235
 236         /*
 237          * struct {
 238          *    encoded_t start_ip;
 239          *    encoded_t fde_addr;
 240          * } binary_search_table[fde_count];
 241          */
 242         char data[0];
 243 } __packed;
 244
 245 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
 246                                u64 offset, u64 *table_data, u64 *segbase,
 247                                u64 *fde_count)
 248 {
 249         struct eh_frame_hdr hdr;
 250         u8 *enc = (u8 *) &hdr.enc;
 251         u8 *end = (u8 *) &hdr.data;
 252         ssize_t r;
 253
 254         r = dso__data_read_offset(dso, machine, offset,
 255                                   (u8 *) &hdr, sizeof(hdr));
 256         if (r != sizeof(hdr))
 257                 return -EINVAL;
 258
 259         /* We dont need eh_frame_ptr, just skip it. */
 260         dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 261
 262         *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
 263         *segbase    = offset;
 264         *table_data = (enc - (u8 *) &hdr) + offset;
 265         return 0;
 266 }
 267
 268 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
 269                                      u64 *table_data, u64 *segbase,
 270                                      u64 *fde_count)
 271 {
 272         int ret = -EINVAL, fd;
 273         u64 offset = dso->data.eh_frame_hdr_offset;
 274
 275         if (offset == 0) {
 276                 fd = dso__data_get_fd(dso, machine);
 277                 if (fd < 0)
 278                         return -EINVAL;
 279
 280                 /* Check the .eh_frame section for unwinding info */
 281                 offset = elf_section_offset(fd, ".eh_frame_hdr");
 282                 dso->data.eh_frame_hdr_offset = offset;
 283                 dso__data_put_fd(dso);
 284         }
 285
 286         if (offset)
 287                 ret = unwind_spec_ehframe(dso, machine, offset,
 288                                           table_data, segbase,
 289                                           fde_count);
 290
 291         return ret;
 292 }
 293
 294 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 295 static int read_unwind_spec_debug_frame(struct dso *dso,
 296                                         struct machine *machine, u64 *offset)
 297 {
 298         int fd;
 299         u64 ofs = dso->data.debug_frame_offset;
 300
 301         /* debug_frame can reside in:
 302          *  - dso
 303          *  - debug pointed by symsrc_filename
 304          *  - gnu_debuglink, which doesn't necessary
 305          *    has to be pointed by symsrc_filename
 306          */
 307         if (ofs == 0) {
 308                 fd = dso__data_get_fd(dso, machine);
 309                 if (fd >= 0) {
 310                         ofs = elf_section_offset(fd, ".debug_frame");
 311                         dso__data_put_fd(dso);
 312                 }
 313
 314                 if (ofs <= 0) {
 315                         fd = open(dso->symsrc_filename, O_RDONLY);
 316                         if (fd >= 0) {
 317                                 ofs = elf_section_offset(fd, ".debug_frame");
 318                                 close(fd);
 319                         }
 320                 }
 321
 322                 if (ofs <= 0) {
 323                         char *debuglink = malloc(PATH_MAX);
 324                         int ret = 0;
 325
 326                         ret = dso__read_binary_type_filename(
 327                                 dso, DSO_BINARY_TYPE__DEBUGLINK,
 328                                 machine->root_dir, debuglink, PATH_MAX);
 329                         if (!ret) {
 330                                 fd = open(debuglink, O_RDONLY);
 331                                 if (fd >= 0) {
 332                                         ofs = elf_section_offset(fd,
 333                                                         ".debug_frame");
 334                                         close(fd);
 335                                 }
 336                         }
 337                         if (ofs > 0) {
 338                                 if (dso->symsrc_filename != NULL) {
 339                                         pr_warning(
 340                                                 "%s: overwrite symsrc(%s,%s)\n",
 341                                                         __func__,
 342                                                         dso->symsrc_filename,
 343                                                         debuglink);
 344                                         free(dso->symsrc_filename);
 345                                 }
 346                                 dso->symsrc_filename = debuglink;
 347                         } else {
 348                                 free(debuglink);
 349                         }
 350                 }
 351
 352                 dso->data.debug_frame_offset = ofs;
 353         }
 354
 355         *offset = ofs;
 356         if (*offset)
 357                 return 0;
 358
 359         return -EINVAL;
 360 }
 361 #endif
 362
 363 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
 364 {
 365         struct addr_location al;
 366
 367         thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
 368                               MAP__FUNCTION, ip, &al);
 369         if (!al.map) {
 370                 /*
 371                  * We've seen cases (softice) where DWARF unwinder went
 372                  * through non executable mmaps, which we need to lookup
 373                  * in MAP__VARIABLE tree.
 374                  */
 375                 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
 376                                       MAP__VARIABLE, ip, &al);
 377         }
 378         return al.map;
 379 }
 380
 381 static int
 382 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 383                int need_unwind_info, void *arg)
 384 {
 385         struct unwind_info *ui = arg;
 386         struct map *map;
 387         unw_dyn_info_t di;
 388         u64 table_data, segbase, fde_count;
 389         int ret = -EINVAL;
 390
 391         map = find_map(ip, ui);
 392         if (!map || !map->dso)
 393                 return -EINVAL;
 394
 395         pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 396
 397         /* Check the .eh_frame section for unwinding info */
 398         if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
 399                                        &table_data, &segbase, &fde_count)) {
 400                 memset(&di, 0, sizeof(di));
 401                 di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 402                 di.start_ip = map->start;
 403                 di.end_ip   = map->end;
 404                 di.u.rti.segbase    = map->start + segbase - map->pgoff;
 405                 di.u.rti.table_data = map->start + table_data - map->pgoff;
 406                 di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 407                                       / sizeof(unw_word_t);
 408                 ret = dwarf_search_unwind_table(as, ip, &di, pi,
 409                                                 need_unwind_info, arg);
 410         }
 411
 412 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 413         /* Check the .debug_frame section for unwinding info */
 414         if (ret < 0 &&
 415             !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
 416                 int fd = dso__data_get_fd(map->dso, ui->machine);
 417                 int is_exec = elf_is_exec(fd, map->dso->name);
 418                 unw_word_t base = is_exec ? 0 : map->start;
 419                 const char *symfile;
 420
 421                 if (fd >= 0)
 422                         dso__data_put_fd(map->dso);
 423
 424                 symfile = map->dso->symsrc_filename ?: map->dso->name;
 425
 426                 memset(&di, 0, sizeof(di));
 427                 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
 428                                            map->start, map->end))
 429                         return dwarf_search_unwind_table(as, ip, &di, pi,
 430                                                          need_unwind_info, arg);
 431         }
 432 #endif
 433
 434         return ret;
 435 }
 436
 437 static int access_fpreg(unw_addr_space_t __maybe_unused as,
 438                         unw_regnum_t __maybe_unused num,
 439                         unw_fpreg_t __maybe_unused *val,
 440                         int __maybe_unused __write,
 441                         void __maybe_unused *arg)
 442 {
 443         pr_err("unwind: access_fpreg unsupported\n");
 444         return -UNW_EINVAL;
 445 }
 446
 447 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
 448                                   unw_word_t __maybe_unused *dil_addr,
 449                                   void __maybe_unused *arg)
 450 {
 451         return -UNW_ENOINFO;
 452 }
 453
 454 static int resume(unw_addr_space_t __maybe_unused as,
 455                   unw_cursor_t __maybe_unused *cu,
 456                   void __maybe_unused *arg)
 457 {
 458         pr_err("unwind: resume unsupported\n");
 459         return -UNW_EINVAL;
 460 }
 461
 462 static int
 463 get_proc_name(unw_addr_space_t __maybe_unused as,
 464               unw_word_t __maybe_unused addr,
 465                 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
 466                 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
 467 {
 468         pr_err("unwind: get_proc_name unsupported\n");
 469         return -UNW_EINVAL;
 470 }
 471
 472 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
 473                           unw_word_t *data)
 474 {
 475         struct map *map;
 476         ssize_t size;
 477
 478         map = find_map(addr, ui);
 479         if (!map) {
 480                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 481                 return -1;
 482         }
 483
 484         if (!map->dso)
 485                 return -1;
 486
 487         size = dso__data_read_addr(map->dso, map, ui->machine,
 488                                    addr, (u8 *) data, sizeof(*data));
 489
 490         return !(size == sizeof(*data));
 491 }
 492
 493 static int access_mem(unw_addr_space_t __maybe_unused as,
 494                       unw_word_t addr, unw_word_t *valp,
 495                       int __write, void *arg)
 496 {
 497         struct unwind_info *ui = arg;
 498         struct stack_dump *stack = &ui->sample->user_stack;
 499         u64 start, end;
 500         int offset;
 501         int ret;
 502
 503         /* Don't support write, probably not needed. */
 504         if (__write || !stack || !ui->sample->user_regs.regs) {
 505                 *valp = 0;
 506                 return 0;
 507         }
 508
 509         ret = perf_reg_value(&start, &ui->sample->user_regs,
 510                              LIBUNWIND__ARCH_REG_SP);
 511         if (ret)
 512                 return ret;
 513
 514         end = start + stack->size;
 515
 516         /* Check overflow. */
 517         if (addr + sizeof(unw_word_t) < addr)
 518                 return -EINVAL;
 519
 520         if (addr < start || addr + sizeof(unw_word_t) >= end) {
 521                 ret = access_dso_mem(ui, addr, valp);
 522                 if (ret) {
 523                         pr_debug("unwind: access_mem %p not inside range"
 524                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 525                                  (void *) (uintptr_t) addr, start, end);
 526                         *valp = 0;
 527                         return ret;
 528                 }
 529                 return 0;
 530         }
 531
 532         offset = addr - start;
 533         *valp  = *(unw_word_t *)&stack->data[offset];
 534         pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
 535                  (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
 536         return 0;
 537 }
 538
 539 static int access_reg(unw_addr_space_t __maybe_unused as,
 540                       unw_regnum_t regnum, unw_word_t *valp,
 541                       int __write, void *arg)
 542 {
 543         struct unwind_info *ui = arg;
 544         int id, ret;
 545         u64 val;
 546
 547         /* Don't support write, I suspect we don't need it. */
 548         if (__write) {
 549                 pr_err("unwind: access_reg w %d\n", regnum);
 550                 return 0;
 551         }
 552
 553         if (!ui->sample->user_regs.regs) {
 554                 *valp = 0;
 555                 return 0;
 556         }
 557
 558         id = LIBUNWIND__ARCH_REG_ID(regnum);
 559         if (id < 0)
 560                 return -EINVAL;
 561
 562         ret = perf_reg_value(&val, &ui->sample->user_regs, id);
 563         if (ret) {
 564                 pr_err("unwind: can't read reg %d\n", regnum);
 565                 return ret;
 566         }
 567
 568         *valp = (unw_word_t) val;
 569         pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
 570         return 0;
 571 }
 572
 573 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
 574                             unw_proc_info_t *pi __maybe_unused,
 575                             void *arg __maybe_unused)
 576 {
 577         pr_debug("unwind: put_unwind_info called\n");
 578 }
 579
 580 static int entry(u64 ip, struct thread *thread,
 581                  unwind_entry_cb_t cb, void *arg)
 582 {
 583         struct unwind_entry e;
 584         struct addr_location al;
 585
 586         thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
 587                                    MAP__FUNCTION, ip, &al);
 588
 589         e.ip = al.addr;
 590         e.map = al.map;
 591         e.sym = al.sym;
 592
 593         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 594                  al.sym ? al.sym->name : "''",
 595                  ip,
 596                  al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
 597
 598         return cb(&e, arg);
 599 }
 600
 601 static void display_error(int err)
 602 {
 603         switch (err) {
 604         case UNW_EINVAL:
 605                 pr_err("unwind: Only supports local.\n");
 606                 break;
 607         case UNW_EUNSPEC:
 608                 pr_err("unwind: Unspecified error.\n");
 609                 break;
 610         case UNW_EBADREG:
 611                 pr_err("unwind: Register unavailable.\n");
 612                 break;
 613         default:
 614                 break;
 615         }
 616 }
 617
 618 static unw_accessors_t accessors = {
 619         .find_proc_info         = find_proc_info,
 620         .put_unwind_info        = put_unwind_info,
 621         .get_dyn_info_list_addr = get_dyn_info_list_addr,
 622         .access_mem             = access_mem,
 623         .access_reg             = access_reg,
 624         .access_fpreg           = access_fpreg,
 625         .resume                 = resume,
 626         .get_proc_name          = get_proc_name,
 627 };
 628
 629 static int _unwind__prepare_access(struct thread *thread)
 630 {
 631         if (callchain_param.record_mode != CALLCHAIN_DWARF)
 632                 return 0;
 633
 634         thread->addr_space = unw_create_addr_space(&accessors, 0);
 635         if (!thread->addr_space) {
 636                 pr_err("unwind: Can't create unwind address space.\n");
 637                 return -ENOMEM;
 638         }
 639
 640         unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
 641         return 0;
 642 }
 643
 644 static void _unwind__flush_access(struct thread *thread)
 645 {
 646         if (callchain_param.record_mode != CALLCHAIN_DWARF)
 647                 return;
 648
 649         unw_flush_cache(thread->addr_space, 0, 0);
 650 }
 651
 652 static void _unwind__finish_access(struct thread *thread)
 653 {
 654         if (callchain_param.record_mode != CALLCHAIN_DWARF)
 655                 return;
 656
 657         unw_destroy_addr_space(thread->addr_space);
 658 }
 659
 660 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 661                        void *arg, int max_stack)
 662 {
 663         u64 val;
 664         unw_word_t ips[max_stack];
 665         unw_addr_space_t addr_space;
 666         unw_cursor_t c;
 667         int ret, i = 0;
 668
 669         ret = perf_reg_value(&val, &ui->sample->user_regs,
 670                              LIBUNWIND__ARCH_REG_IP);
 671         if (ret)
 672                 return ret;
 673
 674         ips[i++] = (unw_word_t) val;
 675
 676         /*
 677          * If we need more than one entry, do the DWARF
 678          * unwind itself.
 679          */
 680         if (max_stack - 1 > 0) {
 681                 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
 682                 addr_space = ui->thread->addr_space;
 683
 684                 if (addr_space == NULL)
 685                         return -1;
 686
 687                 ret = unw_init_remote(&c, addr_space, ui);
 688                 if (ret)
 689                         display_error(ret);
 690
 691                 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
 692                         unw_get_reg(&c, UNW_REG_IP, &ips[i]);
 693                         ++i;
 694                 }
 695
 696                 max_stack = i;
 697         }
 698
 699         /*
 700          * Display what we got based on the order setup.
 701          */
 702         for (i = 0; i < max_stack && !ret; i++) {
 703                 int j = i;
 704
 705                 if (callchain_param.order == ORDER_CALLER)
 706                         j = max_stack - i - 1;
 707                 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
 708         }
 709
 710         return ret;
 711 }
 712
 713 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 714                         struct thread *thread,
 715                         struct perf_sample *data, int max_stack)
 716 {
 717         struct unwind_info ui = {
 718                 .sample       = data,
 719                 .thread       = thread,
 720                 .machine      = thread->mg->machine,
 721         };
 722
 723         if (!data->user_regs.regs)
 724                 return -EINVAL;
 725
 726         if (max_stack <= 0)
 727                 return -EINVAL;
 728
 729         return get_entries(&ui, cb, arg, max_stack);
 730 }
 731
 732 static struct unwind_libunwind_ops
 733 _unwind_libunwind_ops = {
 734         .prepare_access = _unwind__prepare_access,
 735         .flush_access   = _unwind__flush_access,
 736         .finish_access  = _unwind__finish_access,
 737         .get_entries    = _unwind__get_entries,
 738 };
 739
 740 #ifndef REMOTE_UNWIND_LIBUNWIND
 741 struct unwind_libunwind_ops *
 742 local_unwind_libunwind_ops = &_unwind_libunwind_ops;
 743 #endif