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