tools/perf/util/unwind-libunwind-local.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
   4  *
   5  * Lots of this code have been borrowed or heavily inspired from parts of
   6  * the libunwind 0.99 code which are (amongst other contributors I may have
   7  * forgotten):
   8  *
   9  * Copyright (C) 2002-2007 Hewlett-Packard Co
  10  *      Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
  11  *
  12  * And the bugs have been added by:
  13  *
  14  * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
  15  * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
  16  *
  17  */
  18
  19 #include <elf.h>
  20 #include <errno.h>
  21 #include <gelf.h>
  22 #include <fcntl.h>
  23 #include <inttypes.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <sys/mman.h>
  27 #include <linux/list.h>
  28 #include <linux/zalloc.h>
  29 #ifndef REMOTE_UNWIND_LIBUNWIND
  30 #include <libunwind.h>
  31 #include <libunwind-ptrace.h>
  32 #endif
  33 #include "callchain.h"
  34 #include "thread.h"
  35 #include "session.h"
  36 #include "perf_regs.h"
  37 #include "unwind.h"
  38 #include "map.h"
  39 #include "symbol.h"
  40 #include "debug.h"
  41 #include "asm/bug.h"
  42 #include "dso.h"
  43
  44 extern int
  45 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
  46                                     unw_word_t ip,
  47                                     unw_dyn_info_t *di,
  48                                     unw_proc_info_t *pi,
  49                                     int need_unwind_info, void *arg);
  50
  51 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
  52
  53 extern int
  54 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
  55                                  unw_word_t ip,
  56                                  unw_word_t segbase,
  57                                  const char *obj_name, unw_word_t start,
  58                                  unw_word_t end);
  59
  60 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
  61
  62 #define DW_EH_PE_FORMAT_MASK    0x0f    /* format of the encoded value */
  63 #define DW_EH_PE_APPL_MASK      0x70    /* how the value is to be applied */
  64
  65 /* Pointer-encoding formats: */
  66 #define DW_EH_PE_omit           0xff
  67 #define DW_EH_PE_ptr            0x00    /* pointer-sized unsigned value */
  68 #define DW_EH_PE_udata4         0x03    /* unsigned 32-bit value */
  69 #define DW_EH_PE_udata8         0x04    /* unsigned 64-bit value */
  70 #define DW_EH_PE_sdata4         0x0b    /* signed 32-bit value */
  71 #define DW_EH_PE_sdata8         0x0c    /* signed 64-bit value */
  72
  73 /* Pointer-encoding application: */
  74 #define DW_EH_PE_absptr         0x00    /* absolute value */
  75 #define DW_EH_PE_pcrel          0x10    /* rel. to addr. of encoded value */
  76
  77 /*
  78  * The following are not documented by LSB v1.3, yet they are used by
  79  * GCC, presumably they aren't documented by LSB since they aren't
  80  * used on Linux:
  81  */
  82 #define DW_EH_PE_funcrel        0x40    /* start-of-procedure-relative */
  83 #define DW_EH_PE_aligned        0x50    /* aligned pointer */
  84
  85 /* Flags intentionally not handled, since they're not needed:
  86  * #define DW_EH_PE_indirect      0x80
  87  * #define DW_EH_PE_uleb128       0x01
  88  * #define DW_EH_PE_udata2        0x02
  89  * #define DW_EH_PE_sleb128       0x09
  90  * #define DW_EH_PE_sdata2        0x0a
  91  * #define DW_EH_PE_textrel       0x20
  92  * #define DW_EH_PE_datarel       0x30
  93  */
  94
  95 struct unwind_info {
  96         struct perf_sample      *sample;
  97         struct machine          *machine;
  98         struct thread           *thread;
  99         bool                     best_effort;
 100 };
 101
 102 #define dw_read(ptr, type, end) ({      \
 103         type *__p = (type *) ptr;       \
 104         type  __v;                      \
 105         if ((__p + 1) > (type *) end)   \
 106                 return -EINVAL;         \
 107         __v = *__p++;                   \
 108         ptr = (typeof(ptr)) __p;        \
 109         __v;                            \
 110         })
 111
 112 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
 113                                    u8 encoding)
 114 {
 115         u8 *cur = *p;
 116         *val = 0;
 117
 118         switch (encoding) {
 119         case DW_EH_PE_omit:
 120                 *val = 0;
 121                 goto out;
 122         case DW_EH_PE_ptr:
 123                 *val = dw_read(cur, unsigned long, end);
 124                 goto out;
 125         default:
 126                 break;
 127         }
 128
 129         switch (encoding & DW_EH_PE_APPL_MASK) {
 130         case DW_EH_PE_absptr:
 131                 break;
 132         case DW_EH_PE_pcrel:
 133                 *val = (unsigned long) cur;
 134                 break;
 135         default:
 136                 return -EINVAL;
 137         }
 138
 139         if ((encoding & 0x07) == 0x00)
 140                 encoding |= DW_EH_PE_udata4;
 141
 142         switch (encoding & DW_EH_PE_FORMAT_MASK) {
 143         case DW_EH_PE_sdata4:
 144                 *val += dw_read(cur, s32, end);
 145                 break;
 146         case DW_EH_PE_udata4:
 147                 *val += dw_read(cur, u32, end);
 148                 break;
 149         case DW_EH_PE_sdata8:
 150                 *val += dw_read(cur, s64, end);
 151                 break;
 152         case DW_EH_PE_udata8:
 153                 *val += dw_read(cur, u64, end);
 154                 break;
 155         default:
 156                 return -EINVAL;
 157         }
 158
 159  out:
 160         *p = cur;
 161         return 0;
 162 }
 163
 164 #define dw_read_encoded_value(ptr, end, enc) ({                 \
 165         u64 __v;                                                \
 166         if (__dw_read_encoded_value(&ptr, end, &__v, enc)) {    \
 167                 return -EINVAL;                                 \
 168         }                                                       \
 169         __v;                                                    \
 170         })
 171
 172 static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
 173 {
 174         Elf *elf;
 175         GElf_Ehdr ehdr;
 176         GElf_Shdr shdr;
 177         int ret = -1;
 178
 179         elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 180         if (elf == NULL)
 181                 return -1;
 182
 183         if (gelf_getehdr(elf, &ehdr) == NULL)
 184                 goto out_err;
 185
 186         if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
 187                 goto out_err;
 188
 189         *address = shdr.sh_addr;
 190         *offset = shdr.sh_offset;
 191         ret = 0;
 192 out_err:
 193         elf_end(elf);
 194         return ret;
 195 }
 196
 197 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 198 static u64 elf_section_offset(int fd, const char *name)
 199 {
 200         u64 address, offset = 0;
 201
 202         if (elf_section_address_and_offset(fd, name, &address, &offset))
 203                 return 0;
 204
 205         return offset;
 206 }
 207 #endif
 208
 209 static u64 elf_base_address(int fd)
 210 {
 211         Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 212         GElf_Phdr phdr;
 213         u64 retval = 0;
 214         size_t i, phdrnum = 0;
 215
 216         if (elf == NULL)
 217                 return 0;
 218         (void)elf_getphdrnum(elf, &phdrnum);
 219         /* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */
 220         for (i = 0; i < phdrnum; i++) {
 221                 if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) {
 222                         retval = phdr.p_vaddr & -getpagesize();
 223                         break;
 224                 }
 225         }
 226
 227         elf_end(elf);
 228         return retval;
 229 }
 230
 231 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 232 static int elf_is_exec(int fd, const char *name)
 233 {
 234         Elf *elf;
 235         GElf_Ehdr ehdr;
 236         int retval = 0;
 237
 238         elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
 239         if (elf == NULL)
 240                 return 0;
 241         if (gelf_getehdr(elf, &ehdr) == NULL)
 242                 goto out;
 243
 244         retval = (ehdr.e_type == ET_EXEC);
 245
 246 out:
 247         elf_end(elf);
 248         pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
 249         return retval;
 250 }
 251 #endif
 252
 253 struct table_entry {
 254         u32 start_ip_offset;
 255         u32 fde_offset;
 256 };
 257
 258 struct eh_frame_hdr {
 259         unsigned char version;
 260         unsigned char eh_frame_ptr_enc;
 261         unsigned char fde_count_enc;
 262         unsigned char table_enc;
 263
 264         /*
 265          * The rest of the header is variable-length and consists of the
 266          * following members:
 267          *
 268          *      encoded_t eh_frame_ptr;
 269          *      encoded_t fde_count;
 270          */
 271
 272         /* A single encoded pointer should not be more than 8 bytes. */
 273         u64 enc[2];
 274
 275         /*
 276          * struct {
 277          *    encoded_t start_ip;
 278          *    encoded_t fde_addr;
 279          * } binary_search_table[fde_count];
 280          */
 281         char data[];
 282 } __packed;
 283
 284 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
 285                                u64 offset, u64 *table_data_offset, u64 *fde_count)
 286 {
 287         struct eh_frame_hdr hdr;
 288         u8 *enc = (u8 *) &hdr.enc;
 289         u8 *end = (u8 *) &hdr.data;
 290         ssize_t r;
 291
 292         r = dso__data_read_offset(dso, machine, offset,
 293                                   (u8 *) &hdr, sizeof(hdr));
 294         if (r != sizeof(hdr))
 295                 return -EINVAL;
 296
 297         /* We dont need eh_frame_ptr, just skip it. */
 298         dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 299
 300         *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
 301         *table_data_offset = enc - (u8 *) &hdr;
 302         return 0;
 303 }
 304
 305 static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
 306                                      u64 *table_data, u64 *segbase,
 307                                      u64 *fde_count)
 308 {
 309         struct map_rb_node *map_node;
 310         u64 base_addr = UINT64_MAX;
 311         int ret, fd;
 312
 313         if (dso->data.eh_frame_hdr_offset == 0) {
 314                 fd = dso__data_get_fd(dso, ui->machine);
 315                 if (fd < 0)
 316                         return -EINVAL;
 317
 318                 /* Check the .eh_frame section for unwinding info */
 319                 ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
 320                                                      &dso->data.eh_frame_hdr_addr,
 321                                                      &dso->data.eh_frame_hdr_offset);
 322                 dso->data.elf_base_addr = elf_base_address(fd);
 323                 dso__data_put_fd(dso);
 324                 if (ret || dso->data.eh_frame_hdr_offset == 0)
 325                         return -EINVAL;
 326         }
 327
 328         maps__for_each_entry(thread__maps(ui->thread), map_node) {
 329                 struct map *map = map_node->map;
 330                 u64 start = map__start(map);
 331
 332                 if (map__dso(map) == dso && start < base_addr)
 333                         base_addr = start;
 334         }
 335         base_addr -= dso->data.elf_base_addr;
 336         /* Address of .eh_frame_hdr */
 337         *segbase = base_addr + dso->data.eh_frame_hdr_addr;
 338         ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
 339                                    table_data, fde_count);
 340         if (ret)
 341                 return ret;
 342         /* binary_search_table offset plus .eh_frame_hdr address */
 343         *table_data += *segbase;
 344         return 0;
 345 }
 346
 347 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 348 static int read_unwind_spec_debug_frame(struct dso *dso,
 349                                         struct machine *machine, u64 *offset)
 350 {
 351         int fd;
 352         u64 ofs = dso->data.debug_frame_offset;
 353
 354         /* debug_frame can reside in:
 355          *  - dso
 356          *  - debug pointed by symsrc_filename
 357          *  - gnu_debuglink, which doesn't necessary
 358          *    has to be pointed by symsrc_filename
 359          */
 360         if (ofs == 0) {
 361                 fd = dso__data_get_fd(dso, machine);
 362                 if (fd >= 0) {
 363                         ofs = elf_section_offset(fd, ".debug_frame");
 364                         dso__data_put_fd(dso);
 365                 }
 366
 367                 if (ofs <= 0) {
 368                         fd = open(dso->symsrc_filename, O_RDONLY);
 369                         if (fd >= 0) {
 370                                 ofs = elf_section_offset(fd, ".debug_frame");
 371                                 close(fd);
 372                         }
 373                 }
 374
 375                 if (ofs <= 0) {
 376                         char *debuglink = malloc(PATH_MAX);
 377                         int ret = 0;
 378
 379                         ret = dso__read_binary_type_filename(
 380                                 dso, DSO_BINARY_TYPE__DEBUGLINK,
 381                                 machine->root_dir, debuglink, PATH_MAX);
 382                         if (!ret) {
 383                                 fd = open(debuglink, O_RDONLY);
 384                                 if (fd >= 0) {
 385                                         ofs = elf_section_offset(fd,
 386                                                         ".debug_frame");
 387                                         close(fd);
 388                                 }
 389                         }
 390                         if (ofs > 0) {
 391                                 if (dso->symsrc_filename != NULL) {
 392                                         pr_warning(
 393                                                 "%s: overwrite symsrc(%s,%s)\n",
 394                                                         __func__,
 395                                                         dso->symsrc_filename,
 396                                                         debuglink);
 397                                         zfree(&dso->symsrc_filename);
 398                                 }
 399                                 dso->symsrc_filename = debuglink;
 400                         } else {
 401                                 free(debuglink);
 402                         }
 403                 }
 404
 405                 dso->data.debug_frame_offset = ofs;
 406         }
 407
 408         *offset = ofs;
 409         if (*offset)
 410                 return 0;
 411
 412         return -EINVAL;
 413 }
 414 #endif
 415
 416 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
 417 {
 418         struct addr_location al;
 419         struct map *ret;
 420
 421         addr_location__init(&al);
 422         thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
 423         ret = map__get(al.map);
 424         addr_location__exit(&al);
 425         return ret;
 426 }
 427
 428 static int
 429 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 430                int need_unwind_info, void *arg)
 431 {
 432         struct unwind_info *ui = arg;
 433         struct map *map;
 434         struct dso *dso;
 435         unw_dyn_info_t di;
 436         u64 table_data, segbase, fde_count;
 437         int ret = -EINVAL;
 438
 439         map = find_map(ip, ui);
 440         if (!map)
 441                 return -EINVAL;
 442
 443         dso = map__dso(map);
 444         if (!dso) {
 445                 map__put(map);
 446                 return -EINVAL;
 447         }
 448
 449         pr_debug("unwind: find_proc_info dso %s\n", dso->name);
 450
 451         /* Check the .eh_frame section for unwinding info */
 452         if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) {
 453                 memset(&di, 0, sizeof(di));
 454                 di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 455                 di.start_ip = map__start(map);
 456                 di.end_ip   = map__end(map);
 457                 di.u.rti.segbase    = segbase;
 458                 di.u.rti.table_data = table_data;
 459                 di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 460                                       / sizeof(unw_word_t);
 461                 ret = dwarf_search_unwind_table(as, ip, &di, pi,
 462                                                 need_unwind_info, arg);
 463         }
 464
 465 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 466         /* Check the .debug_frame section for unwinding info */
 467         if (ret < 0 &&
 468             !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) {
 469                 int fd = dso__data_get_fd(dso, ui->machine);
 470                 int is_exec = elf_is_exec(fd, dso->name);
 471                 u64 start = map__start(map);
 472                 unw_word_t base = is_exec ? 0 : start;
 473                 const char *symfile;
 474
 475                 if (fd >= 0)
 476                         dso__data_put_fd(dso);
 477
 478                 symfile = dso->symsrc_filename ?: dso->name;
 479
 480                 memset(&di, 0, sizeof(di));
 481                 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
 482                         ret = dwarf_search_unwind_table(as, ip, &di, pi,
 483                                                         need_unwind_info, arg);
 484         }
 485 #endif
 486         map__put(map);
 487         return ret;
 488 }
 489
 490 static int access_fpreg(unw_addr_space_t __maybe_unused as,
 491                         unw_regnum_t __maybe_unused num,
 492                         unw_fpreg_t __maybe_unused *val,
 493                         int __maybe_unused __write,
 494                         void __maybe_unused *arg)
 495 {
 496         pr_err("unwind: access_fpreg unsupported\n");
 497         return -UNW_EINVAL;
 498 }
 499
 500 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
 501                                   unw_word_t __maybe_unused *dil_addr,
 502                                   void __maybe_unused *arg)
 503 {
 504         return -UNW_ENOINFO;
 505 }
 506
 507 static int resume(unw_addr_space_t __maybe_unused as,
 508                   unw_cursor_t __maybe_unused *cu,
 509                   void __maybe_unused *arg)
 510 {
 511         pr_err("unwind: resume unsupported\n");
 512         return -UNW_EINVAL;
 513 }
 514
 515 static int
 516 get_proc_name(unw_addr_space_t __maybe_unused as,
 517               unw_word_t __maybe_unused addr,
 518                 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
 519                 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
 520 {
 521         pr_err("unwind: get_proc_name unsupported\n");
 522         return -UNW_EINVAL;
 523 }
 524
 525 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
 526                           unw_word_t *data)
 527 {
 528         struct map *map;
 529         struct dso *dso;
 530         ssize_t size;
 531
 532         map = find_map(addr, ui);
 533         if (!map) {
 534                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 535                 return -1;
 536         }
 537
 538         dso = map__dso(map);
 539
 540         if (!dso) {
 541                 map__put(map);
 542                 return -1;
 543         }
 544
 545         size = dso__data_read_addr(dso, map, ui->machine,
 546                                    addr, (u8 *) data, sizeof(*data));
 547         map__put(map);
 548         return !(size == sizeof(*data));
 549 }
 550
 551 static int access_mem(unw_addr_space_t __maybe_unused as,
 552                       unw_word_t addr, unw_word_t *valp,
 553                       int __write, void *arg)
 554 {
 555         struct unwind_info *ui = arg;
 556         const char *arch = perf_env__arch(ui->machine->env);
 557         struct stack_dump *stack = &ui->sample->user_stack;
 558         u64 start, end;
 559         int offset;
 560         int ret;
 561
 562         /* Don't support write, probably not needed. */
 563         if (__write || !stack || !ui->sample->user_regs.regs) {
 564                 *valp = 0;
 565                 return 0;
 566         }
 567
 568         ret = perf_reg_value(&start, &ui->sample->user_regs,
 569                              perf_arch_reg_sp(arch));
 570         if (ret)
 571                 return ret;
 572
 573         end = start + stack->size;
 574
 575         /* Check overflow. */
 576         if (addr + sizeof(unw_word_t) < addr)
 577                 return -EINVAL;
 578
 579         if (addr < start || addr + sizeof(unw_word_t) >= end) {
 580                 ret = access_dso_mem(ui, addr, valp);
 581                 if (ret) {
 582                         pr_debug("unwind: access_mem %p not inside range"
 583                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 584                                  (void *) (uintptr_t) addr, start, end);
 585                         *valp = 0;
 586                         return ret;
 587                 }
 588                 return 0;
 589         }
 590
 591         offset = addr - start;
 592         *valp  = *(unw_word_t *)&stack->data[offset];
 593         pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
 594                  (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
 595         return 0;
 596 }
 597
 598 static int access_reg(unw_addr_space_t __maybe_unused as,
 599                       unw_regnum_t regnum, unw_word_t *valp,
 600                       int __write, void *arg)
 601 {
 602         struct unwind_info *ui = arg;
 603         int id, ret;
 604         u64 val;
 605
 606         /* Don't support write, I suspect we don't need it. */
 607         if (__write) {
 608                 pr_err("unwind: access_reg w %d\n", regnum);
 609                 return 0;
 610         }
 611
 612         if (!ui->sample->user_regs.regs) {
 613                 *valp = 0;
 614                 return 0;
 615         }
 616
 617         id = LIBUNWIND__ARCH_REG_ID(regnum);
 618         if (id < 0)
 619                 return -EINVAL;
 620
 621         ret = perf_reg_value(&val, &ui->sample->user_regs, id);
 622         if (ret) {
 623                 if (!ui->best_effort)
 624                         pr_err("unwind: can't read reg %d\n", regnum);
 625                 return ret;
 626         }
 627
 628         *valp = (unw_word_t) val;
 629         pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
 630         return 0;
 631 }
 632
 633 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
 634                             unw_proc_info_t *pi __maybe_unused,
 635                             void *arg __maybe_unused)
 636 {
 637         pr_debug("unwind: put_unwind_info called\n");
 638 }
 639
 640 static int entry(u64 ip, struct thread *thread,
 641                  unwind_entry_cb_t cb, void *arg)
 642 {
 643         struct unwind_entry e;
 644         struct addr_location al;
 645         int ret;
 646
 647         addr_location__init(&al);
 648         e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
 649         e.ip     = ip;
 650         e.ms.map = al.map;
 651         e.ms.maps = al.maps;
 652
 653         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 654                  al.sym ? al.sym->name : "''",
 655                  ip,
 656                  al.map ? map__map_ip(al.map, ip) : (u64) 0);
 657
 658         ret = cb(&e, arg);
 659         addr_location__exit(&al);
 660         return ret;
 661 }
 662
 663 static void display_error(int err)
 664 {
 665         switch (err) {
 666         case UNW_EINVAL:
 667                 pr_err("unwind: Only supports local.\n");
 668                 break;
 669         case UNW_EUNSPEC:
 670                 pr_err("unwind: Unspecified error.\n");
 671                 break;
 672         case UNW_EBADREG:
 673                 pr_err("unwind: Register unavailable.\n");
 674                 break;
 675         default:
 676                 break;
 677         }
 678 }
 679
 680 static unw_accessors_t accessors = {
 681         .find_proc_info         = find_proc_info,
 682         .put_unwind_info        = put_unwind_info,
 683         .get_dyn_info_list_addr = get_dyn_info_list_addr,
 684         .access_mem             = access_mem,
 685         .access_reg             = access_reg,
 686         .access_fpreg           = access_fpreg,
 687         .resume                 = resume,
 688         .get_proc_name          = get_proc_name,
 689 };
 690
 691 static int _unwind__prepare_access(struct maps *maps)
 692 {
 693         void *addr_space = unw_create_addr_space(&accessors, 0);
 694
 695         RC_CHK_ACCESS(maps)->addr_space = addr_space;
 696         if (!addr_space) {
 697                 pr_err("unwind: Can't create unwind address space.\n");
 698                 return -ENOMEM;
 699         }
 700
 701         unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
 702         return 0;
 703 }
 704
 705 static void _unwind__flush_access(struct maps *maps)
 706 {
 707         unw_flush_cache(maps__addr_space(maps), 0, 0);
 708 }
 709
 710 static void _unwind__finish_access(struct maps *maps)
 711 {
 712         unw_destroy_addr_space(maps__addr_space(maps));
 713 }
 714
 715 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 716                        void *arg, int max_stack)
 717 {
 718         const char *arch = perf_env__arch(ui->machine->env);
 719         u64 val;
 720         unw_word_t ips[max_stack];
 721         unw_addr_space_t addr_space;
 722         unw_cursor_t c;
 723         int ret, i = 0;
 724
 725         ret = perf_reg_value(&val, &ui->sample->user_regs,
 726                              perf_arch_reg_ip(arch));
 727         if (ret)
 728                 return ret;
 729
 730         ips[i++] = (unw_word_t) val;
 731
 732         /*
 733          * If we need more than one entry, do the DWARF
 734          * unwind itself.
 735          */
 736         if (max_stack - 1 > 0) {
 737                 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
 738                 addr_space = maps__addr_space(thread__maps(ui->thread));
 739
 740                 if (addr_space == NULL)
 741                         return -1;
 742
 743                 ret = unw_init_remote(&c, addr_space, ui);
 744                 if (ret && !ui->best_effort)
 745                         display_error(ret);
 746
 747                 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
 748                         unw_get_reg(&c, UNW_REG_IP, &ips[i]);
 749
 750                         /*
 751                          * Decrement the IP for any non-activation frames.
 752                          * this is required to properly find the srcline
 753                          * for caller frames.
 754                          * See also the documentation for dwfl_frame_pc(),
 755                          * which this code tries to replicate.
 756                          */
 757                         if (unw_is_signal_frame(&c) <= 0)
 758                                 --ips[i];
 759
 760                         ++i;
 761                 }
 762
 763                 max_stack = i;
 764         }
 765
 766         /*
 767          * Display what we got based on the order setup.
 768          */
 769         for (i = 0; i < max_stack && !ret; i++) {
 770                 int j = i;
 771
 772                 if (callchain_param.order == ORDER_CALLER)
 773                         j = max_stack - i - 1;
 774                 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
 775         }
 776
 777         return ret;
 778 }
 779
 780 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 781                         struct thread *thread,
 782                         struct perf_sample *data, int max_stack,
 783                         bool best_effort)
 784 {
 785         struct unwind_info ui = {
 786                 .sample       = data,
 787                 .thread       = thread,
 788                 .machine      = maps__machine(thread__maps(thread)),
 789                 .best_effort  = best_effort
 790         };
 791
 792         if (!data->user_regs.regs)
 793                 return -EINVAL;
 794
 795         if (max_stack <= 0)
 796                 return -EINVAL;
 797
 798         return get_entries(&ui, cb, arg, max_stack);
 799 }
 800
 801 static struct unwind_libunwind_ops
 802 _unwind_libunwind_ops = {
 803         .prepare_access = _unwind__prepare_access,
 804         .flush_access   = _unwind__flush_access,
 805         .finish_access  = _unwind__finish_access,
 806         .get_entries    = _unwind__get_entries,
 807 };
 808
 809 #ifndef REMOTE_UNWIND_LIBUNWIND
 810 struct unwind_libunwind_ops *
 811 local_unwind_libunwind_ops = &_unwind_libunwind_ops;
 812 #endif