gdb/gcore.c

   1 /* Generate a core file for the inferior process.
   2
   3    Copyright (C) 2001-2012 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "elf-bfd.h"
  22 #include "infcall.h"
  23 #include "inferior.h"
  24 #include "gdbcore.h"
  25 #include "objfiles.h"
  26 #include "solib.h"
  27 #include "symfile.h"
  28 #include "arch-utils.h"
  29 #include "completer.h"
  30 #include "gcore.h"
  31 #include "cli/cli-decode.h"
  32 #include "gdb_assert.h"
  33 #include <fcntl.h>
  34 #include "regcache.h"
  35 #include "regset.h"
  36
  37 /* The largest amount of memory to read from the target at once.  We
  38    must throttle it to limit the amount of memory used by GDB during
  39    generate-core-file for programs with large resident data.  */
  40 #define MAX_COPY_BYTES (1024 * 1024)
  41
  42 static const char *default_gcore_target (void);
  43 static enum bfd_architecture default_gcore_arch (void);
  44 static unsigned long default_gcore_mach (void);
  45 static int gcore_memory_sections (bfd *);
  46
  47 /* create_gcore_bfd -- helper for gcore_command (exported).
  48    Open a new bfd core file for output, and return the handle.  */
  49
  50 bfd *
  51 create_gcore_bfd (char *filename)
  52 {
  53   bfd *obfd = bfd_openw (filename, default_gcore_target ());
  54
  55   if (!obfd)
  56     error (_("Failed to open '%s' for output."), filename);
  57   bfd_set_format (obfd, bfd_core);
  58   bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());
  59   return obfd;
  60 }
  61
  62 /* write_gcore_file -- helper for gcore_command (exported).
  63    Compose and write the corefile data to the core file.  */
  64
  65
  66 void
  67 write_gcore_file (bfd *obfd)
  68 {
  69   void *note_data = NULL;
  70   int note_size = 0;
  71   asection *note_sec = NULL;
  72
  73   /* An external target method must build the notes section.  */
  74   /* FIXME: uweigand/2011-10-06: All architectures that support core file
  75      generation should be converted to gdbarch_make_corefile_notes; at that
  76      point, the target vector method can be removed.  */
  77   if (!gdbarch_make_corefile_notes_p (target_gdbarch))
  78     note_data = target_make_corefile_notes (obfd, &note_size);
  79   else
  80     note_data = gdbarch_make_corefile_notes (target_gdbarch, obfd, &note_size);
  81
  82   if (note_data == NULL || note_size == 0)
  83     error (_("Target does not support core file generation."));
  84
  85   /* Create the note section.  */
  86   note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
  87                                                  SEC_HAS_CONTENTS
  88                                                  | SEC_READONLY
  89                                                  | SEC_ALLOC);
  90   if (note_sec == NULL)
  91     error (_("Failed to create 'note' section for corefile: %s"),
  92            bfd_errmsg (bfd_get_error ()));
  93
  94   bfd_set_section_vma (obfd, note_sec, 0);
  95   bfd_set_section_alignment (obfd, note_sec, 0);
  96   bfd_set_section_size (obfd, note_sec, note_size);
  97
  98   /* Now create the memory/load sections.  */
  99   if (gcore_memory_sections (obfd) == 0)
 100     error (_("gcore: failed to get corefile memory sections from target."));
 101
 102   /* Write out the contents of the note section.  */
 103   if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
 104     warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));
 105 }
 106
 107 static void
 108 do_bfd_delete_cleanup (void *arg)
 109 {
 110   bfd *obfd = arg;
 111   const char *filename = obfd->filename;
 112
 113   bfd_close (arg);
 114   unlink (filename);
 115 }
 116
 117 /* gcore_command -- implements the 'gcore' command.
 118    Generate a core file from the inferior process.  */
 119
 120 static void
 121 gcore_command (char *args, int from_tty)
 122 {
 123   struct cleanup *old_chain;
 124   char *corefilename, corefilename_buffer[40];
 125   bfd *obfd;
 126
 127   /* No use generating a corefile without a target process.  */
 128   if (!target_has_execution)
 129     noprocess ();
 130
 131   if (args && *args)
 132     corefilename = args;
 133   else
 134     {
 135       /* Default corefile name is "core.PID".  */
 136       sprintf (corefilename_buffer, "core.%d", PIDGET (inferior_ptid));
 137       corefilename = corefilename_buffer;
 138     }
 139
 140   if (info_verbose)
 141     fprintf_filtered (gdb_stdout,
 142                       "Opening corefile '%s' for output.\n", corefilename);
 143
 144   /* Open the output file.  */
 145   obfd = create_gcore_bfd (corefilename);
 146
 147   /* Need a cleanup that will close and delete the file.  */
 148   old_chain = make_cleanup (do_bfd_delete_cleanup, obfd);
 149
 150   /* Call worker function.  */
 151   write_gcore_file (obfd);
 152
 153   /* Succeeded.  */
 154   fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
 155
 156   discard_cleanups (old_chain);
 157   bfd_close (obfd);
 158 }
 159
 160 static unsigned long
 161 default_gcore_mach (void)
 162 {
 163 #if 1   /* See if this even matters...  */
 164   return 0;
 165 #else
 166
 167   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch);
 168
 169   if (bfdarch != NULL)
 170     return bfdarch->mach;
 171   if (exec_bfd == NULL)
 172     error (_("Can't find default bfd machine type (need execfile)."));
 173
 174   return bfd_get_mach (exec_bfd);
 175 #endif /* 1 */
 176 }
 177
 178 static enum bfd_architecture
 179 default_gcore_arch (void)
 180 {
 181   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch);
 182
 183   if (bfdarch != NULL)
 184     return bfdarch->arch;
 185   if (exec_bfd == NULL)
 186     error (_("Can't find bfd architecture for corefile (need execfile)."));
 187
 188   return bfd_get_arch (exec_bfd);
 189 }
 190
 191 static const char *
 192 default_gcore_target (void)
 193 {
 194   /* The gdbarch may define a target to use for core files.  */
 195   if (gdbarch_gcore_bfd_target_p (target_gdbarch))
 196     return gdbarch_gcore_bfd_target (target_gdbarch);
 197
 198   /* Otherwise, try to fall back to the exec_bfd target.  This will probably
 199      not work for non-ELF targets.  */
 200   if (exec_bfd == NULL)
 201     return NULL;
 202   else
 203     return bfd_get_target (exec_bfd);
 204 }
 205
 206 /* Derive a reasonable stack segment by unwinding the target stack,
 207    and store its limits in *BOTTOM and *TOP.  Return non-zero if
 208    successful.  */
 209
 210 static int
 211 derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
 212 {
 213   struct frame_info *fi, *tmp_fi;
 214
 215   gdb_assert (bottom);
 216   gdb_assert (top);
 217
 218   /* Can't succeed without stack and registers.  */
 219   if (!target_has_stack || !target_has_registers)
 220     return 0;
 221
 222   /* Can't succeed without current frame.  */
 223   fi = get_current_frame ();
 224   if (fi == NULL)
 225     return 0;
 226
 227   /* Save frame pointer of TOS frame.  */
 228   *top = get_frame_base (fi);
 229   /* If current stack pointer is more "inner", use that instead.  */
 230   if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top))
 231     *top = get_frame_sp (fi);
 232
 233   /* Find prev-most frame.  */
 234   while ((tmp_fi = get_prev_frame (fi)) != NULL)
 235     fi = tmp_fi;
 236
 237   /* Save frame pointer of prev-most frame.  */
 238   *bottom = get_frame_base (fi);
 239
 240   /* Now canonicalize their order, so that BOTTOM is a lower address
 241      (as opposed to a lower stack frame).  */
 242   if (*bottom > *top)
 243     {
 244       bfd_vma tmp_vma;
 245
 246       tmp_vma = *top;
 247       *top = *bottom;
 248       *bottom = tmp_vma;
 249     }
 250
 251   return 1;
 252 }
 253
 254 /* call_target_sbrk --
 255    helper function for derive_heap_segment.  */
 256
 257 static bfd_vma
 258 call_target_sbrk (int sbrk_arg)
 259 {
 260   struct objfile *sbrk_objf;
 261   struct gdbarch *gdbarch;
 262   bfd_vma top_of_heap;
 263   struct value *target_sbrk_arg;
 264   struct value *sbrk_fn, *ret;
 265   bfd_vma tmp;
 266
 267   if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
 268     {
 269       sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf);
 270       if (sbrk_fn == NULL)
 271         return (bfd_vma) 0;
 272     }
 273   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
 274     {
 275       sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf);
 276       if (sbrk_fn == NULL)
 277         return (bfd_vma) 0;
 278     }
 279   else
 280     return (bfd_vma) 0;
 281
 282   gdbarch = get_objfile_arch (sbrk_objf);
 283   target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int,
 284                                         sbrk_arg);
 285   gdb_assert (target_sbrk_arg);
 286   ret = call_function_by_hand (sbrk_fn, 1, &target_sbrk_arg);
 287   if (ret == NULL)
 288     return (bfd_vma) 0;
 289
 290   tmp = value_as_long (ret);
 291   if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff)
 292     return (bfd_vma) 0;
 293
 294   top_of_heap = tmp;
 295   return top_of_heap;
 296 }
 297
 298 /* Derive a reasonable heap segment for ABFD by looking at sbrk and
 299    the static data sections.  Store its limits in *BOTTOM and *TOP.
 300    Return non-zero if successful.  */
 301
 302 static int
 303 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
 304 {
 305   bfd_vma top_of_data_memory = 0;
 306   bfd_vma top_of_heap = 0;
 307   bfd_size_type sec_size;
 308   bfd_vma sec_vaddr;
 309   asection *sec;
 310
 311   gdb_assert (bottom);
 312   gdb_assert (top);
 313
 314   /* This function depends on being able to call a function in the
 315      inferior.  */
 316   if (!target_has_execution)
 317     return 0;
 318
 319   /* The following code assumes that the link map is arranged as
 320      follows (low to high addresses):
 321
 322      ---------------------------------
 323      | text sections                 |
 324      ---------------------------------
 325      | data sections (including bss) |
 326      ---------------------------------
 327      | heap                          |
 328      --------------------------------- */
 329
 330   for (sec = abfd->sections; sec; sec = sec->next)
 331     {
 332       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
 333           || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
 334         {
 335           sec_vaddr = bfd_get_section_vma (abfd, sec);
 336           sec_size = bfd_get_section_size (sec);
 337           if (sec_vaddr + sec_size > top_of_data_memory)
 338             top_of_data_memory = sec_vaddr + sec_size;
 339         }
 340     }
 341
 342   top_of_heap = call_target_sbrk (0);
 343   if (top_of_heap == (bfd_vma) 0)
 344     return 0;
 345
 346   /* Return results.  */
 347   if (top_of_heap > top_of_data_memory)
 348     {
 349       *bottom = top_of_data_memory;
 350       *top = top_of_heap;
 351       return 1;
 352     }
 353
 354   /* No additional heap space needs to be saved.  */
 355   return 0;
 356 }
 357
 358 static void
 359 make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
 360 {
 361   int p_flags = 0;
 362   int p_type = 0;
 363
 364   /* FIXME: these constants may only be applicable for ELF.  */
 365   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
 366     p_type = PT_LOAD;
 367   else if (strncmp (bfd_section_name (obfd, osec), "note", 4) == 0)
 368     p_type = PT_NOTE;
 369   else
 370     p_type = PT_NULL;
 371
 372   p_flags |= PF_R;      /* Segment is readable.  */
 373   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
 374     p_flags |= PF_W;    /* Segment is writable.  */
 375   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
 376     p_flags |= PF_X;    /* Segment is executable.  */
 377
 378   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
 379 }
 380
 381 static int
 382 gcore_create_callback (CORE_ADDR vaddr, unsigned long size,
 383                        int read, int write, int exec, void *data)
 384 {
 385   bfd *obfd = data;
 386   asection *osec;
 387   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;
 388
 389   /* If the memory segment has no permissions set, ignore it, otherwise
 390      when we later try to access it for read/write, we'll get an error
 391      or jam the kernel.  */
 392   if (read == 0 && write == 0 && exec == 0)
 393     {
 394       if (info_verbose)
 395         {
 396           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n",
 397                             plongest (size), paddress (target_gdbarch, vaddr));
 398         }
 399
 400       return 0;
 401     }
 402
 403   if (write == 0 && !solib_keep_data_in_core (vaddr, size))
 404     {
 405       /* See if this region of memory lies inside a known file on disk.
 406          If so, we can avoid copying its contents by clearing SEC_LOAD.  */
 407       struct objfile *objfile;
 408       struct obj_section *objsec;
 409
 410       ALL_OBJSECTIONS (objfile, objsec)
 411         {
 412           bfd *abfd = objfile->obfd;
 413           asection *asec = objsec->the_bfd_section;
 414           bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
 415                                                                     asec);
 416           bfd_vma start = obj_section_addr (objsec) & -align;
 417           bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align;
 418
 419           /* Match if either the entire memory region lies inside the
 420              section (i.e. a mapping covering some pages of a large
 421              segment) or the entire section lies inside the memory region
 422              (i.e. a mapping covering multiple small sections).
 423
 424              This BFD was synthesized from reading target memory,
 425              we don't want to omit that.  */
 426           if (((vaddr >= start && vaddr + size <= end)
 427                || (start >= vaddr && end <= vaddr + size))
 428               && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
 429             {
 430               flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS);
 431               goto keep;        /* Break out of two nested for loops.  */
 432             }
 433         }
 434
 435     keep:
 436       flags |= SEC_READONLY;
 437     }
 438
 439   if (exec)
 440     flags |= SEC_CODE;
 441   else
 442     flags |= SEC_DATA;
 443
 444   osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
 445   if (osec == NULL)
 446     {
 447       warning (_("Couldn't make gcore segment: %s"),
 448                bfd_errmsg (bfd_get_error ()));
 449       return 1;
 450     }
 451
 452   if (info_verbose)
 453     {
 454       fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n",
 455                         plongest (size), paddress (target_gdbarch, vaddr));
 456     }
 457
 458   bfd_set_section_size (obfd, osec, size);
 459   bfd_set_section_vma (obfd, osec, vaddr);
 460   bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
 461   return 0;
 462 }
 463
 464 static int
 465 objfile_find_memory_regions (find_memory_region_ftype func, void *obfd)
 466 {
 467   /* Use objfile data to create memory sections.  */
 468   struct objfile *objfile;
 469   struct obj_section *objsec;
 470   bfd_vma temp_bottom, temp_top;
 471
 472   /* Call callback function for each objfile section.  */
 473   ALL_OBJSECTIONS (objfile, objsec)
 474     {
 475       bfd *ibfd = objfile->obfd;
 476       asection *isec = objsec->the_bfd_section;
 477       flagword flags = bfd_get_section_flags (ibfd, isec);
 478
 479       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
 480         {
 481           int size = bfd_section_size (ibfd, isec);
 482           int ret;
 483
 484           ret = (*func) (obj_section_addr (objsec), size,
 485                          1, /* All sections will be readable.  */
 486                          (flags & SEC_READONLY) == 0, /* Writable.  */
 487                          (flags & SEC_CODE) != 0, /* Executable.  */
 488                          obfd);
 489           if (ret != 0)
 490             return ret;
 491         }
 492     }
 493
 494   /* Make a stack segment.  */
 495   if (derive_stack_segment (&temp_bottom, &temp_top))
 496     (*func) (temp_bottom, temp_top - temp_bottom,
 497              1, /* Stack section will be readable.  */
 498              1, /* Stack section will be writable.  */
 499              0, /* Stack section will not be executable.  */
 500              obfd);
 501
 502   /* Make a heap segment.  */
 503   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
 504     (*func) (temp_bottom, temp_top - temp_bottom,
 505              1, /* Heap section will be readable.  */
 506              1, /* Heap section will be writable.  */
 507              0, /* Heap section will not be executable.  */
 508              obfd);
 509
 510   return 0;
 511 }
 512
 513 static void
 514 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
 515 {
 516   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
 517   file_ptr offset = 0;
 518   struct cleanup *old_chain = NULL;
 519   void *memhunk;
 520
 521   /* Read-only sections are marked; we don't have to copy their contents.  */
 522   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
 523     return;
 524
 525   /* Only interested in "load" sections.  */
 526   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
 527     return;
 528
 529   size = min (total_size, MAX_COPY_BYTES);
 530   memhunk = xmalloc (size);
 531   old_chain = make_cleanup (xfree, memhunk);
 532
 533   while (total_size > 0)
 534     {
 535       if (size > total_size)
 536         size = total_size;
 537
 538       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
 539                               memhunk, size) != 0)
 540         {
 541           warning (_("Memory read failed for corefile "
 542                      "section, %s bytes at %s."),
 543                    plongest (size),
 544                    paddress (target_gdbarch, bfd_section_vma (obfd, osec)));
 545           break;
 546         }
 547       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
 548         {
 549           warning (_("Failed to write corefile contents (%s)."),
 550                    bfd_errmsg (bfd_get_error ()));
 551           break;
 552         }
 553
 554       total_size -= size;
 555       offset += size;
 556     }
 557
 558   do_cleanups (old_chain);      /* Frees MEMHUNK.  */
 559 }
 560
 561 static int
 562 gcore_memory_sections (bfd *obfd)
 563 {
 564   if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
 565     return 0;                   /* FIXME: error return/msg?  */
 566
 567   /* Record phdrs for section-to-segment mapping.  */
 568   bfd_map_over_sections (obfd, make_output_phdrs, NULL);
 569
 570   /* Copy memory region contents.  */
 571   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);
 572
 573   return 1;
 574 }
 575
 576 /* Provide a prototype to silence -Wmissing-prototypes.  */
 577 extern initialize_file_ftype _initialize_gcore;
 578
 579 void
 580 _initialize_gcore (void)
 581 {
 582   add_com ("generate-core-file", class_files, gcore_command, _("\
 583 Save a core file with the current state of the debugged process.\n\
 584 Argument is optional filename.  Default filename is 'core.<process_id>'."));
 585
 586   add_com_alias ("gcore", "generate-core-file", class_files, 1);
 587   exec_set_find_memory_regions (objfile_find_memory_regions);
 588 }