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