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) fprintf(stderr, " [unwind(" A ")] " F "\n", __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         tcp->libunwind_ui = _UPT_create(tcp->pid);
 107         if (!tcp->libunwind_ui)
 108                 die_out_of_memory();
 109
 110         tcp->queue = xmalloc(sizeof(*tcp->queue));
 111         tcp->queue->head = NULL;
 112         tcp->queue->tail = NULL;
 113 }
 114
 115 void
 116 unwind_tcb_fin(struct tcb *tcp)
 117 {
 118         queue_print(tcp->queue);
 119         free(tcp->queue);
 120         tcp->queue = NULL;
 121
 122         delete_mmap_cache(tcp, __FUNCTION__);
 123
 124         _UPT_destroy(tcp->libunwind_ui);
 125         tcp->libunwind_ui = NULL;
 126 }
 127
 128 /*
 129  * caching of /proc/ID/maps for each process to speed up stack tracing
 130  *
 131  * The cache must be refreshed after syscalls that affect memory mappings,
 132  * e.g. mmap, mprotect, munmap, execve.
 133  */
 134 static void
 135 build_mmap_cache(struct tcb* tcp)
 136 {
 137         FILE *fp;
 138         struct mmap_cache_t *cache_head;
 139         /* start with a small dynamically-allocated array and then expand it */
 140         size_t cur_array_size = 10;
 141         char filename[sizeof("/proc/4294967296/maps")];
 142         char buffer[PATH_MAX + 80];
 143
 144         unw_flush_cache(libunwind_as, 0, 0);
 145
 146         sprintf(filename, "/proc/%u/maps", tcp->pid);
 147         fp = fopen_for_input(filename, "r");
 148         if (!fp) {
 149                 perror_msg("fopen: %s", filename);
 150                 return;
 151         }
 152
 153         cache_head = xcalloc(cur_array_size, sizeof(*cache_head));
 154
 155         while (fgets(buffer, sizeof(buffer), fp) != NULL) {
 156                 struct mmap_cache_t *entry;
 157                 unsigned long start_addr, end_addr, mmap_offset;
 158                 char exec_bit;
 159                 char binary_path[PATH_MAX];
 160
 161                 if (sscanf(buffer, "%lx-%lx %*c%*c%c%*c %lx %*x:%*x %*d %[^\n]",
 162                            &start_addr, &end_addr, &exec_bit,
 163                            &mmap_offset, binary_path) != 5)
 164                         continue;
 165
 166                 /* ignore mappings that have no PROT_EXEC bit set */
 167                 if (exec_bit != 'x')
 168                         continue;
 169
 170                 if (end_addr < start_addr) {
 171                         error_msg("%s: unrecognized file format", filename);
 172                         break;
 173                 }
 174
 175                 /*
 176                  * sanity check to make sure that we're storing
 177                  * non-overlapping regions in ascending order
 178                  */
 179                 if (tcp->mmap_cache_size > 0) {
 180                         entry = &cache_head[tcp->mmap_cache_size - 1];
 181                         if (entry->start_addr == start_addr &&
 182                             entry->end_addr == end_addr) {
 183                                 /* duplicate entry, e.g. [vsyscall] */
 184                                 continue;
 185                         }
 186                         if (start_addr <= entry->start_addr ||
 187                             start_addr < entry->end_addr) {
 188                                 error_msg("%s: overlapping memory region",
 189                                           filename);
 190                                 continue;
 191                         }
 192                 }
 193
 194                 if (tcp->mmap_cache_size >= cur_array_size) {
 195                         cur_array_size *= 2;
 196                         cache_head = xreallocarray(cache_head, cur_array_size,
 197                                                    sizeof(*cache_head));
 198                 }
 199
 200                 entry = &cache_head[tcp->mmap_cache_size];
 201                 entry->start_addr = start_addr;
 202                 entry->end_addr = end_addr;
 203                 entry->mmap_offset = mmap_offset;
 204                 entry->binary_filename = xstrdup(binary_path);
 205                 tcp->mmap_cache_size++;
 206         }
 207         fclose(fp);
 208         tcp->mmap_cache = cache_head;
 209         tcp->mmap_cache_generation = mmap_cache_generation;
 210
 211         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p",
 212                 "cache-build",
 213                 tcp->mmap_cache_generation,
 214                 mmap_cache_generation,
 215                 tcp, tcp->mmap_cache);
 216 }
 217
 218 /* deleting the cache */
 219 static void
 220 delete_mmap_cache(struct tcb *tcp, const char *caller)
 221 {
 222         unsigned int i;
 223
 224         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p, caller=%s",
 225                 "cache-delete",
 226                 tcp->mmap_cache_generation,
 227                 mmap_cache_generation,
 228                 tcp, tcp->mmap_cache, caller);
 229
 230         for (i = 0; i < tcp->mmap_cache_size; i++) {
 231                 free(tcp->mmap_cache[i].binary_filename);
 232                 tcp->mmap_cache[i].binary_filename = NULL;
 233         }
 234         free(tcp->mmap_cache);
 235         tcp->mmap_cache = NULL;
 236         tcp->mmap_cache_size = 0;
 237 }
 238
 239 static bool
 240 rebuild_cache_if_invalid(struct tcb *tcp, const char *caller)
 241 {
 242         if ((tcp->mmap_cache_generation != mmap_cache_generation)
 243             && tcp->mmap_cache)
 244                 delete_mmap_cache(tcp, caller);
 245
 246         if (!tcp->mmap_cache)
 247                 build_mmap_cache(tcp);
 248
 249         if (!tcp->mmap_cache || !tcp->mmap_cache_size)
 250                 return false;
 251         else
 252                 return true;
 253 }
 254
 255 void
 256 unwind_cache_invalidate(struct tcb* tcp)
 257 {
 258 #if SUPPORTED_PERSONALITIES > 1
 259         if (tcp->currpers != DEFAULT_PERSONALITY) {
 260                 /* disable strack trace */
 261                 return;
 262         }
 263 #endif
 264         mmap_cache_generation++;
 265         DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p", "increment",
 266                 tcp->mmap_cache_generation,
 267                 mmap_cache_generation,
 268                 tcp,
 269                 tcp->mmap_cache);
 270 }
 271
 272 static void
 273 get_symbol_name(unw_cursor_t *cursor, char **name,
 274                 size_t *size, unw_word_t *offset)
 275 {
 276         for (;;) {
 277                 int rc = unw_get_proc_name(cursor, *name, *size, offset);
 278                 if (rc == 0)
 279                         break;
 280                 if (rc != -UNW_ENOMEM) {
 281                         **name = '\0';
 282                         *offset = 0;
 283                         break;
 284                 }
 285                 *name = xreallocarray(*name, 2, *size);
 286                 *size *= 2;
 287         }
 288 }
 289
 290 static int
 291 print_stack_frame(struct tcb *tcp,
 292                   call_action_fn call_action,
 293                   error_action_fn error_action,
 294                   void *data,
 295                   unw_cursor_t *cursor,
 296                   char **symbol_name,
 297                   size_t *symbol_name_size)
 298 {
 299         unw_word_t ip;
 300         int lower = 0;
 301         int upper = (int) tcp->mmap_cache_size - 1;
 302
 303         if (unw_get_reg(cursor, UNW_REG_IP, &ip) < 0) {
 304                 perror_msg("Can't walk the stack of process %d", tcp->pid);
 305                 return -1;
 306         }
 307
 308         while (lower <= upper) {
 309                 struct mmap_cache_t *cur_mmap_cache;
 310                 int mid = (upper + lower) / 2;
 311
 312                 cur_mmap_cache = &tcp->mmap_cache[mid];
 313
 314                 if (ip >= cur_mmap_cache->start_addr &&
 315                     ip < cur_mmap_cache->end_addr) {
 316                         unsigned long true_offset;
 317                         unw_word_t function_offset;
 318
 319                         get_symbol_name(cursor, symbol_name, symbol_name_size,
 320                                         &function_offset);
 321                         true_offset = ip - cur_mmap_cache->start_addr +
 322                                 cur_mmap_cache->mmap_offset;
 323                         call_action(data,
 324                                     cur_mmap_cache->binary_filename,
 325                                     *symbol_name,
 326                                     function_offset,
 327                                     true_offset);
 328                         return 0;
 329                 }
 330                 else if (ip < cur_mmap_cache->start_addr)
 331                         upper = mid - 1;
 332                 else
 333                         lower = mid + 1;
 334         }
 335
 336         /*
 337          * there is a bug in libunwind >= 1.0
 338          * after a set_tid_address syscall
 339          * unw_get_reg returns IP == 0
 340          */
 341         if(ip)
 342                 error_action(data, "unexpected_backtracing_error", ip);
 343         return -1;
 344 }
 345
 346 /*
 347  * walking the stack
 348  */
 349 static void
 350 stacktrace_walk(struct tcb *tcp,
 351                 call_action_fn call_action,
 352                 error_action_fn error_action,
 353                 void *data)
 354 {
 355         char *symbol_name;
 356         size_t symbol_name_size = 40;
 357         unw_cursor_t cursor;
 358         int stack_depth;
 359
 360         if (!tcp->mmap_cache)
 361                 error_msg_and_die("bug: mmap_cache is NULL");
 362         if (tcp->mmap_cache_size == 0)
 363                 error_msg_and_die("bug: mmap_cache is empty");
 364
 365         symbol_name = xmalloc(symbol_name_size);
 366
 367         if (unw_init_remote(&cursor, libunwind_as, tcp->libunwind_ui) < 0)
 368                 perror_msg_and_die("Can't initiate libunwind");
 369
 370         for (stack_depth = 0; stack_depth < 256; ++stack_depth) {
 371                 if (print_stack_frame(tcp, call_action, error_action, data,
 372                                 &cursor, &symbol_name, &symbol_name_size) < 0)
 373                         break;
 374                 if (unw_step(&cursor) <= 0)
 375                         break;
 376         }
 377         if (stack_depth >= 256)
 378                 error_action(data, "too many stack frames", 0);
 379
 380         free(symbol_name);
 381 }
 382
 383 /*
 384  * printing an entry in stack to stream or buffer
 385  */
 386 /*
 387  * we want to keep the format used by backtrace_symbols from the glibc
 388  *
 389  * ./a.out() [0x40063d]
 390  * ./a.out() [0x4006bb]
 391  * ./a.out() [0x4006c6]
 392  * /lib64/libc.so.6(__libc_start_main+0xed) [0x7fa2f8a5976d]
 393  * ./a.out() [0x400569]
 394  */
 395 #define STACK_ENTRY_SYMBOL_FMT                  \
 396         " > %s(%s+0x%lx) [0x%lx]\n",            \
 397         binary_filename,                        \
 398         symbol_name,                            \
 399         (unsigned long) function_offset,        \
 400         true_offset
 401 #define STACK_ENTRY_NOSYMBOL_FMT                \
 402         " > %s() [0x%lx]\n",                    \
 403         binary_filename, true_offset
 404 #define STACK_ENTRY_BUG_FMT                     \
 405         " > BUG IN %s\n"
 406 #define STACK_ENTRY_ERROR_WITH_OFFSET_FMT       \
 407         " > %s [0x%lx]\n", error, true_offset
 408 #define STACK_ENTRY_ERROR_FMT                   \
 409         " > %s\n", error
 410
 411 static void
 412 print_call_cb(void *dummy,
 413               const char *binary_filename,
 414               const char *symbol_name,
 415               unw_word_t function_offset,
 416               unsigned long true_offset)
 417 {
 418         if (symbol_name && (symbol_name[0] != '\0'))
 419                 tprintf(STACK_ENTRY_SYMBOL_FMT);
 420         else if (binary_filename)
 421                 tprintf(STACK_ENTRY_NOSYMBOL_FMT);
 422         else
 423                 tprintf(STACK_ENTRY_BUG_FMT, __FUNCTION__);
 424
 425         line_ended();
 426 }
 427
 428 static void
 429 print_error_cb(void *dummy,
 430                const char *error,
 431                unsigned long true_offset)
 432 {
 433         if (true_offset)
 434                 tprintf(STACK_ENTRY_ERROR_WITH_OFFSET_FMT);
 435         else
 436                 tprintf(STACK_ENTRY_ERROR_FMT);
 437
 438         line_ended();
 439 }
 440
 441 static char *
 442 sprint_call_or_error(const char *binary_filename,
 443                      const char *symbol_name,
 444                      unw_word_t function_offset,
 445                      unsigned long true_offset,
 446                      const char *error)
 447 {
 448        char *output_line = NULL;
 449        int n;
 450
 451        if (symbol_name)
 452                n = asprintf(&output_line, STACK_ENTRY_SYMBOL_FMT);
 453        else if (binary_filename)
 454                n = asprintf(&output_line, STACK_ENTRY_NOSYMBOL_FMT);
 455        else if (error)
 456                n = true_offset
 457                        ? asprintf(&output_line, STACK_ENTRY_ERROR_WITH_OFFSET_FMT)
 458                        : asprintf(&output_line, STACK_ENTRY_ERROR_FMT);
 459        else
 460                n = asprintf(&output_line, STACK_ENTRY_BUG_FMT, __FUNCTION__);
 461
 462        if (n < 0)
 463                error_msg_and_die("error in asprintf");
 464
 465        return output_line;
 466 }
 467
 468 /*
 469  * queue manipulators
 470  */
 471 static void
 472 queue_put(struct queue_t *queue,
 473           const char *binary_filename,
 474           const char *symbol_name,
 475           unw_word_t function_offset,
 476           unsigned long true_offset,
 477           const char *error)
 478 {
 479         struct call_t *call;
 480
 481         call = xmalloc(sizeof(*call));
 482         call->output_line = sprint_call_or_error(binary_filename,
 483                                                  symbol_name,
 484                                                  function_offset,
 485                                                  true_offset,
 486                                                  error);
 487         call->next = NULL;
 488
 489         if (!queue->head) {
 490                 queue->head = call;
 491                 queue->tail = call;
 492         } else {
 493                 queue->tail->next = call;
 494                 queue->tail = call;
 495         }
 496 }
 497
 498 static void
 499 queue_put_call(void *queue,
 500                const char *binary_filename,
 501                const char *symbol_name,
 502                unw_word_t function_offset,
 503                unsigned long true_offset)
 504 {
 505         queue_put(queue,
 506                   binary_filename,
 507                   symbol_name,
 508                   function_offset,
 509                   true_offset,
 510                   NULL);
 511 }
 512
 513 static void
 514 queue_put_error(void *queue,
 515                 const char *error,
 516                 unsigned long ip)
 517 {
 518         queue_put(queue, NULL, NULL, 0, ip, error);
 519 }
 520
 521 static void
 522 queue_print(struct queue_t *queue)
 523 {
 524         struct call_t *call, *tmp;
 525
 526         queue->tail = NULL;
 527         call = queue->head;
 528         queue->head = NULL;
 529         while (call) {
 530                 tmp = call;
 531                 call = call->next;
 532
 533                 tprints(tmp->output_line);
 534                 line_ended();
 535
 536                 free(tmp->output_line);
 537                 tmp->output_line = NULL;
 538                 tmp->next = NULL;
 539                 free(tmp);
 540         }
 541 }
 542
 543 /*
 544  * printing stack
 545  */
 546 void
 547 unwind_print_stacktrace(struct tcb* tcp)
 548 {
 549 #if SUPPORTED_PERSONALITIES > 1
 550         if (tcp->currpers != DEFAULT_PERSONALITY) {
 551                 /* disable strack trace */
 552                 return;
 553         }
 554 #endif
 555        if (tcp->queue->head) {
 556                DPRINTF("tcp=%p, queue=%p", "queueprint", tcp, tcp->queue->head);
 557                queue_print(tcp->queue);
 558        }
 559        else if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
 560                DPRINTF("tcp=%p, queue=%p", "stackprint", tcp, tcp->queue->head);
 561                stacktrace_walk(tcp, print_call_cb, print_error_cb, NULL);
 562        }
 563 }
 564
 565 /*
 566  * capturing stack
 567  */
 568 void
 569 unwind_capture_stacktrace(struct tcb *tcp)
 570 {
 571 #if SUPPORTED_PERSONALITIES > 1
 572         if (tcp->currpers != DEFAULT_PERSONALITY) {
 573                 /* disable strack trace */
 574                 return;
 575         }
 576 #endif
 577         if (tcp->queue->head)
 578                 error_msg_and_die("bug: unprinted entries in queue");
 579
 580         if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
 581                 stacktrace_walk(tcp, queue_put_call, queue_put_error,
 582                                 tcp->queue);
 583                 DPRINTF("tcp=%p, queue=%p", "captured", tcp, tcp->queue->head);
 584         }
 585 }