granicus.if.org Git - strace/blob - unwind.c

   1 /*
   2  * Copyright (c) 2013 Luca Clementi <luca.clementi@gmail.com>
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The name of the author may not be used to endorse or promote products
  13  *    derived from this software without specific prior written permission.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "defs.h"
  28 #include <limits.h>
  29 #include <libunwind-ptrace.h>
  30
  31 #ifdef _LARGEFILE64_SOURCE
  32 # ifdef HAVE_FOPEN64
  33 #  define fopen_for_input fopen64
  34 # else
  35 #  define fopen_for_input fopen
  36 # endif
  37 #else
  38 # define fopen_for_input fopen
  39 #endif
  40
  41 #define DPRINTF(F, A, ...) if (debug_flag) error_msg("[unwind(" A ")] " F, __VA_ARGS__)
  42
  43 /*
  44  * Кeep a sorted array of cache entries,
  45  * so that we can binary search through it.
  46  */
  47 struct mmap_cache_t {
  48         /**
  49          * example entry:
  50          * 7fabbb09b000-7fabbb09f000 r-xp 00179000 fc:00 1180246 /lib/libc-2.11.1.so
  51          *
  52          * start_addr  is 0x7fabbb09b000
  53          * end_addr    is 0x7fabbb09f000
  54          * mmap_offset is 0x179000
  55          * binary_filename is "/lib/libc-2.11.1.so"
  56          */
  57         unsigned long start_addr;
  58         unsigned long end_addr;
  59         unsigned long mmap_offset;
  60         char *binary_filename;
  61 };
  62
  63 /*
  64  * Type used in stacktrace walker
  65  */
  66 typedef void (*call_action_fn)(void *data,
  67                                const char *binary_filename,
  68                                const char *symbol_name,
  69                                unw_word_t function_offset,
  70                                unsigned long true_offset);
  71 typedef void (*error_action_fn)(void *data,
  72                                 const char *error,
  73                                 unsigned long true_offset);
  74
  75 /*
  76  * Type used in stacktrace capturing
  77  */
  78 struct call_t {
  79        struct call_t* next;
  80        char *output_line;
  81 };
  82
  83 struct queue_t {
  84        struct call_t *tail;
  85        struct call_t *head;
  86 };
  87
  88 static void queue_print(struct queue_t *queue);
  89 static void delete_mmap_cache(struct tcb *tcp, const char *caller);
  90
  91 static unw_addr_space_t libunwind_as;
  92 static unsigned int mmap_cache_generation;
  93
  94 void
  95 unwind_init(void)
  96 {
  97         libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
  98         if (!libunwind_as)
  99                 error_msg_and_die("failed to create address space for stack tracing");
 100         unw_set_caching_policy(libunwind_as, UNW_CACHE_GLOBAL);
 101 }
 102
 103 void
 104 unwind_tcb_init(struct tcb *tcp)
 105 {
 106         if (tcp->libunwind_ui)
 107                 return;
 108
 109         tcp->libunwind_ui = _UPT_create(tcp->pid);
 110         if (!tcp->libunwind_ui)
 111                 die_out_of_memory();
 112
 113         tcp->queue = xmalloc(sizeof(*tcp->queue));
 114         tcp->queue->head = NULL;
 115         tcp->queue->tail = NULL;
 116 }
 117
 118 void
 119 unwind_tcb_fin(struct tcb *tcp)
 120 {
 121         queue_print(tcp->queue);
 122         free(tcp->queue);
 123         tcp->queue = NULL;
 124
 125         delete_mmap_cache(tcp, __FUNCTION__);
 126
 127         _UPT_destroy(tcp->libunwind_ui);
 128         tcp->libunwind_ui = NULL;
 129 }
 130
 131 /*
 132  * caching of /proc/ID/maps for each process to speed up stack tracing
 133  *
 134  * The cache must be refreshed after syscalls that affect memory mappings,
 135  * e.g. mmap, mprotect, munmap, execve.
 136  */
 137 static void
 138 build_mmap_cache(struct tcb* tcp)
 139 {
 140         FILE *fp;
 141         struct mmap_cache_t *cache_head;
 142         /* start with a small dynamically-allocated array and then expand it */
 143         size_t cur_array_size = 10;
 144         char filename[sizeof("/proc/4294967296/maps")];
 145         char buffer[PATH_MAX + 80];
 146
 147         unw_flush_cache(libunwind_as, 0, 0);
 148
 149         sprintf(filename, "/proc/%u/maps", tcp->pid);
 150         fp = fopen_for_input(filename, "r");
 151         if (!fp) {
 152                 perror_msg("fopen: %s", filename);
 153                 return;
 154         }
 155
 156         cache_head = xcalloc(cur_array_size, sizeof(*cache_head));
 157
 158         while (fgets(buffer, sizeof(buffer), fp) != NULL) {
 159                 struct mmap_cache_t *entry;
 160                 unsigned long start_addr, end_addr, mmap_offset;
 161                 char exec_bit;
 162                 char binary_path[PATH_MAX];
 163
 164                 if (sscanf(buffer, "%lx-%lx %*c%*c%c%*c %lx %*x:%*x %*d %[^\n]",
 165                            &start_addr, &end_addr, &exec_bit,
 166                            &mmap_offset, binary_path) != 5)
 167                         continue;
 168
 169                 /* ignore mappings that have no PROT_EXEC bit set */
 170                 if (exec_bit != 'x')
 171                         continue;
 172
 173                 if (end_addr < start_addr) {
 174                         error_msg("%s: unrecognized file format", filename);
 175                         break;
 176                 }
 177
 178                 /*
 179                  * sanity check to make sure that we're storing
 180                  * non-overlapping regions in ascending order
 181                  */
 182                 if (tcp->mmap_cache_size > 0) {
 183                         entry = &cache_head[tcp->mmap_cache_size - 1];
 184                         if (entry->start_addr == start_addr &&
 185                             entry->end_addr == end_addr) {
 186                                 /* duplicate entry, e.g. [vsyscall] */
 187                                 continue;
 188                         }
 189                         if (start_addr <= entry->start_addr ||
 190                             start_addr < entry->end_addr) {
 191                                 error_msg("%s: overlapping memory region",
 192                                           filename);
 193                                 continue;
 194                         }
 195                 }
 196
 197                 if (tcp->mmap_cache_size >= cur_array_size) {
 198                         cur_array_size *= 2;
 199                         cache_head = xreallocarray(cache_head, cur_array_size,
 200                                                    sizeof(*cache_head));
 201                 }
 202
 203                 entry = &cache_head[tcp->mmap_cache_size];
 204                 entry->start_addr = start_addr;
 205                 entry->end_addr = end_addr;
 206                 entry->mmap_offset = mmap_offset;
 207                 entry->binary_filename = xstrdup(binary_path);
 208                 tcp->mmap_cache_size++;
 209         }
 210         fclose(fp);
 211         tcp->mmap_cache = cache_head;
 212         tcp->mmap_cache_generation = mmap_cache_generation;
 213
 214         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p",
 215                 "cache-build",
 216                 tcp->mmap_cache_generation,
 217                 mmap_cache_generation,
 218                 tcp, tcp->mmap_cache);
 219 }
 220
 221 /* deleting the cache */
 222 static void
 223 delete_mmap_cache(struct tcb *tcp, const char *caller)
 224 {
 225         unsigned int i;
 226
 227         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p, caller=%s",
 228                 "cache-delete",
 229                 tcp->mmap_cache_generation,
 230                 mmap_cache_generation,
 231                 tcp, tcp->mmap_cache, caller);
 232
 233         for (i = 0; i < tcp->mmap_cache_size; i++) {
 234                 free(tcp->mmap_cache[i].binary_filename);
 235                 tcp->mmap_cache[i].binary_filename = NULL;
 236         }
 237         free(tcp->mmap_cache);
 238         tcp->mmap_cache = NULL;
 239         tcp->mmap_cache_size = 0;
 240 }
 241
 242 static bool
 243 rebuild_cache_if_invalid(struct tcb *tcp, const char *caller)
 244 {
 245         if ((tcp->mmap_cache_generation != mmap_cache_generation)
 246             && tcp->mmap_cache)
 247                 delete_mmap_cache(tcp, caller);
 248
 249         if (!tcp->mmap_cache)
 250                 build_mmap_cache(tcp);
 251
 252         if (!tcp->mmap_cache || !tcp->mmap_cache_size)
 253                 return false;
 254         else
 255                 return true;
 256 }
 257
 258 void
 259 unwind_cache_invalidate(struct tcb* tcp)
 260 {
 261 #if SUPPORTED_PERSONALITIES > 1
 262         if (tcp->currpers != DEFAULT_PERSONALITY) {
 263                 /* disable strack trace */
 264                 return;
 265         }
 266 #endif
 267         mmap_cache_generation++;
 268         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p", "increment",
 269                 tcp->mmap_cache_generation,
 270                 mmap_cache_generation,
 271                 tcp,
 272                 tcp->mmap_cache);
 273 }
 274
 275 static void
 276 get_symbol_name(unw_cursor_t *cursor, char **name,
 277                 size_t *size, unw_word_t *offset)
 278 {
 279         for (;;) {
 280                 int rc = unw_get_proc_name(cursor, *name, *size, offset);
 281                 if (rc == 0)
 282                         break;
 283                 if (rc != -UNW_ENOMEM) {
 284                         **name = '\0';
 285                         *offset = 0;
 286                         break;
 287                 }
 288                 *name = xreallocarray(*name, 2, *size);
 289                 *size *= 2;
 290         }
 291 }
 292
 293 static int
 294 print_stack_frame(struct tcb *tcp,
 295                   call_action_fn call_action,
 296                   error_action_fn error_action,
 297                   void *data,
 298                   unw_cursor_t *cursor,
 299                   char **symbol_name,
 300                   size_t *symbol_name_size)
 301 {
 302         unw_word_t ip;
 303         int lower = 0;
 304         int upper = (int) tcp->mmap_cache_size - 1;
 305
 306         if (unw_get_reg(cursor, UNW_REG_IP, &ip) < 0) {
 307                 perror_msg("Can't walk the stack of process %d", tcp->pid);
 308                 return -1;
 309         }
 310
 311         while (lower <= upper) {
 312                 struct mmap_cache_t *cur_mmap_cache;
 313                 int mid = (upper + lower) / 2;
 314
 315                 cur_mmap_cache = &tcp->mmap_cache[mid];
 316
 317                 if (ip >= cur_mmap_cache->start_addr &&
 318                     ip < cur_mmap_cache->end_addr) {
 319                         unsigned long true_offset;
 320                         unw_word_t function_offset;
 321
 322                         get_symbol_name(cursor, symbol_name, symbol_name_size,
 323                                         &function_offset);
 324                         true_offset = ip - cur_mmap_cache->start_addr +
 325                                 cur_mmap_cache->mmap_offset;
 326                         call_action(data,
 327                                     cur_mmap_cache->binary_filename,
 328                                     *symbol_name,
 329                                     function_offset,
 330                                     true_offset);
 331                         return 0;
 332                 }
 333                 else if (ip < cur_mmap_cache->start_addr)
 334                         upper = mid - 1;
 335                 else
 336                         lower = mid + 1;
 337         }
 338
 339         /*
 340          * there is a bug in libunwind >= 1.0
 341          * after a set_tid_address syscall
 342          * unw_get_reg returns IP == 0
 343          */
 344         if(ip)
 345                 error_action(data, "unexpected_backtracing_error", ip);
 346         return -1;
 347 }
 348
 349 /*
 350  * walking the stack
 351  */
 352 static void
 353 stacktrace_walk(struct tcb *tcp,
 354                 call_action_fn call_action,
 355                 error_action_fn error_action,
 356                 void *data)
 357 {
 358         char *symbol_name;
 359         size_t symbol_name_size = 40;
 360         unw_cursor_t cursor;
 361         int stack_depth;
 362
 363         if (!tcp->mmap_cache)
 364                 error_msg_and_die("bug: mmap_cache is NULL");
 365         if (tcp->mmap_cache_size == 0)
 366                 error_msg_and_die("bug: mmap_cache is empty");
 367
 368         symbol_name = xmalloc(symbol_name_size);
 369
 370         if (unw_init_remote(&cursor, libunwind_as, tcp->libunwind_ui) < 0)
 371                 perror_msg_and_die("Can't initiate libunwind");
 372
 373         for (stack_depth = 0; stack_depth < 256; ++stack_depth) {
 374                 if (print_stack_frame(tcp, call_action, error_action, data,
 375                                 &cursor, &symbol_name, &symbol_name_size) < 0)
 376                         break;
 377                 if (unw_step(&cursor) <= 0)
 378                         break;
 379         }
 380         if (stack_depth >= 256)
 381                 error_action(data, "too many stack frames", 0);
 382
 383         free(symbol_name);
 384 }
 385
 386 /*
 387  * printing an entry in stack to stream or buffer
 388  */
 389 /*
 390  * we want to keep the format used by backtrace_symbols from the glibc
 391  *
 392  * ./a.out() [0x40063d]
 393  * ./a.out() [0x4006bb]
 394  * ./a.out() [0x4006c6]
 395  * /lib64/libc.so.6(__libc_start_main+0xed) [0x7fa2f8a5976d]
 396  * ./a.out() [0x400569]
 397  */
 398 #define STACK_ENTRY_SYMBOL_FMT                  \
 399         " > %s(%s+0x%lx) [0x%lx]\n",            \
 400         binary_filename,                        \
 401         symbol_name,                            \
 402         (unsigned long) function_offset,        \
 403         true_offset
 404 #define STACK_ENTRY_NOSYMBOL_FMT                \
 405         " > %s() [0x%lx]\n",                    \
 406         binary_filename, true_offset
 407 #define STACK_ENTRY_BUG_FMT                     \
 408         " > BUG IN %s\n"
 409 #define STACK_ENTRY_ERROR_WITH_OFFSET_FMT       \
 410         " > %s [0x%lx]\n", error, true_offset
 411 #define STACK_ENTRY_ERROR_FMT                   \
 412         " > %s\n", error
 413
 414 static void
 415 print_call_cb(void *dummy,
 416               const char *binary_filename,
 417               const char *symbol_name,
 418               unw_word_t function_offset,
 419               unsigned long true_offset)
 420 {
 421         if (symbol_name && (symbol_name[0] != '\0'))
 422                 tprintf(STACK_ENTRY_SYMBOL_FMT);
 423         else if (binary_filename)
 424                 tprintf(STACK_ENTRY_NOSYMBOL_FMT);
 425         else
 426                 tprintf(STACK_ENTRY_BUG_FMT, __FUNCTION__);
 427
 428         line_ended();
 429 }
 430
 431 static void
 432 print_error_cb(void *dummy,
 433                const char *error,
 434                unsigned long true_offset)
 435 {
 436         if (true_offset)
 437                 tprintf(STACK_ENTRY_ERROR_WITH_OFFSET_FMT);
 438         else
 439                 tprintf(STACK_ENTRY_ERROR_FMT);
 440
 441         line_ended();
 442 }
 443
 444 static char *
 445 sprint_call_or_error(const char *binary_filename,
 446                      const char *symbol_name,
 447                      unw_word_t function_offset,
 448                      unsigned long true_offset,
 449                      const char *error)
 450 {
 451        char *output_line = NULL;
 452        int n;
 453
 454        if (symbol_name)
 455                n = asprintf(&output_line, STACK_ENTRY_SYMBOL_FMT);
 456        else if (binary_filename)
 457                n = asprintf(&output_line, STACK_ENTRY_NOSYMBOL_FMT);
 458        else if (error)
 459                n = true_offset
 460                        ? asprintf(&output_line, STACK_ENTRY_ERROR_WITH_OFFSET_FMT)
 461                        : asprintf(&output_line, STACK_ENTRY_ERROR_FMT);
 462        else
 463                n = asprintf(&output_line, STACK_ENTRY_BUG_FMT, __FUNCTION__);
 464
 465        if (n < 0)
 466                error_msg_and_die("error in asprintf");
 467
 468        return output_line;
 469 }
 470
 471 /*
 472  * queue manipulators
 473  */
 474 static void
 475 queue_put(struct queue_t *queue,
 476           const char *binary_filename,
 477           const char *symbol_name,
 478           unw_word_t function_offset,
 479           unsigned long true_offset,
 480           const char *error)
 481 {
 482         struct call_t *call;
 483
 484         call = xmalloc(sizeof(*call));
 485         call->output_line = sprint_call_or_error(binary_filename,
 486                                                  symbol_name,
 487                                                  function_offset,
 488                                                  true_offset,
 489                                                  error);
 490         call->next = NULL;
 491
 492         if (!queue->head) {
 493                 queue->head = call;
 494                 queue->tail = call;
 495         } else {
 496                 queue->tail->next = call;
 497                 queue->tail = call;
 498         }
 499 }
 500
 501 static void
 502 queue_put_call(void *queue,
 503                const char *binary_filename,
 504                const char *symbol_name,
 505                unw_word_t function_offset,
 506                unsigned long true_offset)
 507 {
 508         queue_put(queue,
 509                   binary_filename,
 510                   symbol_name,
 511                   function_offset,
 512                   true_offset,
 513                   NULL);
 514 }
 515
 516 static void
 517 queue_put_error(void *queue,
 518                 const char *error,
 519                 unsigned long ip)
 520 {
 521         queue_put(queue, NULL, NULL, 0, ip, error);
 522 }
 523
 524 static void
 525 queue_print(struct queue_t *queue)
 526 {
 527         struct call_t *call, *tmp;
 528
 529         queue->tail = NULL;
 530         call = queue->head;
 531         queue->head = NULL;
 532         while (call) {
 533                 tmp = call;
 534                 call = call->next;
 535
 536                 tprints(tmp->output_line);
 537                 line_ended();
 538
 539                 free(tmp->output_line);
 540                 tmp->output_line = NULL;
 541                 tmp->next = NULL;
 542                 free(tmp);
 543         }
 544 }
 545
 546 /*
 547  * printing stack
 548  */
 549 void
 550 unwind_print_stacktrace(struct tcb* tcp)
 551 {
 552 #if SUPPORTED_PERSONALITIES > 1
 553         if (tcp->currpers != DEFAULT_PERSONALITY) {
 554                 /* disable strack trace */
 555                 return;
 556         }
 557 #endif
 558        if (tcp->queue->head) {
 559                DPRINTF("tcp=%p, queue=%p", "queueprint", tcp, tcp->queue->head);
 560                queue_print(tcp->queue);
 561        }
 562        else if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
 563                DPRINTF("tcp=%p, queue=%p", "stackprint", tcp, tcp->queue->head);
 564                stacktrace_walk(tcp, print_call_cb, print_error_cb, NULL);
 565        }
 566 }
 567
 568 /*
 569  * capturing stack
 570  */
 571 void
 572 unwind_capture_stacktrace(struct tcb *tcp)
 573 {
 574 #if SUPPORTED_PERSONALITIES > 1
 575         if (tcp->currpers != DEFAULT_PERSONALITY) {
 576                 /* disable strack trace */
 577                 return;
 578         }
 579 #endif
 580         if (tcp->queue->head)
 581                 error_msg_and_die("bug: unprinted entries in queue");
 582
 583         if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
 584                 stacktrace_walk(tcp, queue_put_call, queue_put_error,
 585                                 tcp->queue);
 586                 DPRINTF("tcp=%p, queue=%p", "captured", tcp, tcp->queue->head);
 587         }
 588 }