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