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