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