gdb/gcore.c

   1 /* Generate a core file for the inferior process.
   2
   3    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  21    Boston, MA 02110-1301, USA.  */
  22
  23 #include "defs.h"
  24 #include "elf-bfd.h"
  25 #include "infcall.h"
  26 #include "inferior.h"
  27 #include "gdbcore.h"
  28 #include "objfiles.h"
  29 #include "symfile.h"
  30
  31 #include "cli/cli-decode.h"
  32
  33 #include "gdb_assert.h"
  34
  35 /* The largest amount of memory to read from the target at once.  We
  36    must throttle it to limit the amount of memory used by GDB during
  37    generate-core-file for programs with large resident data.  */
  38 #define MAX_COPY_BYTES (1024 * 1024)
  39
  40 static char *default_gcore_target (void);
  41 static enum bfd_architecture default_gcore_arch (void);
  42 static unsigned long default_gcore_mach (void);
  43 static int gcore_memory_sections (bfd *);
  44
  45 /* Generate a core file from the inferior process.  */
  46
  47 static void
  48 gcore_command (char *args, int from_tty)
  49 {
  50   struct cleanup *old_chain;
  51   char *corefilename, corefilename_buffer[40];
  52   asection *note_sec = NULL;
  53   bfd *obfd;
  54   void *note_data = NULL;
  55   int note_size = 0;
  56
  57   /* No use generating a corefile without a target process.  */
  58   if (!target_has_execution)
  59     noprocess ();
  60
  61   if (args && *args)
  62     corefilename = args;
  63   else
  64     {
  65       /* Default corefile name is "core.PID".  */
  66       sprintf (corefilename_buffer, "core.%d", PIDGET (inferior_ptid));
  67       corefilename = corefilename_buffer;
  68     }
  69
  70   if (info_verbose)
  71     fprintf_filtered (gdb_stdout,
  72                       "Opening corefile '%s' for output.\n", corefilename);
  73
  74   /* Open the output file.  */
  75   obfd = bfd_openw (corefilename, default_gcore_target ());
  76   if (!obfd)
  77     error (_("Failed to open '%s' for output."), corefilename);
  78
  79   /* Need a cleanup that will close the file (FIXME: delete it?).  */
  80   old_chain = make_cleanup_bfd_close (obfd);
  81
  82   bfd_set_format (obfd, bfd_core);
  83   bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());
  84
  85   /* An external target method must build the notes section.  */
  86   note_data = target_make_corefile_notes (obfd, &note_size);
  87
  88   /* Create the note section.  */
  89   if (note_data != NULL && note_size != 0)
  90     {
  91       note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
  92                                                      SEC_HAS_CONTENTS
  93                                                      | SEC_READONLY
  94                                                      | SEC_ALLOC);
  95       if (note_sec == NULL)
  96         error (_("Failed to create 'note' section for corefile: %s"),
  97                bfd_errmsg (bfd_get_error ()));
  98
  99       bfd_set_section_vma (obfd, note_sec, 0);
 100       bfd_set_section_alignment (obfd, note_sec, 0);
 101       bfd_set_section_size (obfd, note_sec, note_size);
 102     }
 103
 104   /* Now create the memory/load sections.  */
 105   if (gcore_memory_sections (obfd) == 0)
 106     error (_("gcore: failed to get corefile memory sections from target."));
 107
 108   /* Write out the contents of the note section.  */
 109   if (note_data != NULL && note_size != 0)
 110     {
 111       if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
 112         warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));
 113     }
 114
 115   /* Succeeded.  */
 116   fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
 117
 118   /* Clean-ups will close the output file and free malloc memory.  */
 119   do_cleanups (old_chain);
 120   return;
 121 }
 122
 123 static unsigned long
 124 default_gcore_mach (void)
 125 {
 126 #if 1   /* See if this even matters...  */
 127   return 0;
 128 #else
 129
 130   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (current_gdbarch);
 131
 132   if (bfdarch != NULL)
 133     return bfdarch->mach;
 134   if (exec_bfd == NULL)
 135     error (_("Can't find default bfd machine type (need execfile)."));
 136
 137   return bfd_get_mach (exec_bfd);
 138 #endif /* 1 */
 139 }
 140
 141 static enum bfd_architecture
 142 default_gcore_arch (void)
 143 {
 144   const struct bfd_arch_info * bfdarch = gdbarch_bfd_arch_info
 145                                          (current_gdbarch);
 146
 147   if (bfdarch != NULL)
 148     return bfdarch->arch;
 149   if (exec_bfd == NULL)
 150     error (_("Can't find bfd architecture for corefile (need execfile)."));
 151
 152   return bfd_get_arch (exec_bfd);
 153 }
 154
 155 static char *
 156 default_gcore_target (void)
 157 {
 158   /* FIXME: This may only work for ELF targets.  */
 159   if (exec_bfd == NULL)
 160     return NULL;
 161   else
 162     return bfd_get_target (exec_bfd);
 163 }
 164
 165 /* Derive a reasonable stack segment by unwinding the target stack,
 166    and store its limits in *BOTTOM and *TOP.  Return non-zero if
 167    successful.  */
 168
 169 static int
 170 derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
 171 {
 172   struct frame_info *fi, *tmp_fi;
 173
 174   gdb_assert (bottom);
 175   gdb_assert (top);
 176
 177   /* Can't succeed without stack and registers.  */
 178   if (!target_has_stack || !target_has_registers)
 179     return 0;
 180
 181   /* Can't succeed without current frame.  */
 182   fi = get_current_frame ();
 183   if (fi == NULL)
 184     return 0;
 185
 186   /* Save frame pointer of TOS frame.  */
 187   *top = get_frame_base (fi);
 188   /* If current stack pointer is more "inner", use that instead.  */
 189   if (gdbarch_inner_than (current_gdbarch, get_frame_sp (fi), *top))
 190     *top = get_frame_sp (fi);
 191
 192   /* Find prev-most frame.  */
 193   while ((tmp_fi = get_prev_frame (fi)) != NULL)
 194     fi = tmp_fi;
 195
 196   /* Save frame pointer of prev-most frame.  */
 197   *bottom = get_frame_base (fi);
 198
 199   /* Now canonicalize their order, so that BOTTOM is a lower address
 200      (as opposed to a lower stack frame).  */
 201   if (*bottom > *top)
 202     {
 203       bfd_vma tmp_vma;
 204
 205       tmp_vma = *top;
 206       *top = *bottom;
 207       *bottom = tmp_vma;
 208     }
 209
 210   return 1;
 211 }
 212
 213 /* Derive a reasonable heap segment for ABFD by looking at sbrk and
 214    the static data sections.  Store its limits in *BOTTOM and *TOP.
 215    Return non-zero if successful.  */
 216
 217 static int
 218 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
 219 {
 220   bfd_vma top_of_data_memory = 0;
 221   bfd_vma top_of_heap = 0;
 222   bfd_size_type sec_size;
 223   struct value *zero, *sbrk;
 224   bfd_vma sec_vaddr;
 225   asection *sec;
 226
 227   gdb_assert (bottom);
 228   gdb_assert (top);
 229
 230   /* This function depends on being able to call a function in the
 231      inferior.  */
 232   if (!target_has_execution)
 233     return 0;
 234
 235   /* The following code assumes that the link map is arranged as
 236      follows (low to high addresses):
 237
 238      ---------------------------------
 239      | text sections                 |
 240      ---------------------------------
 241      | data sections (including bss) |
 242      ---------------------------------
 243      | heap                          |
 244      --------------------------------- */
 245
 246   for (sec = abfd->sections; sec; sec = sec->next)
 247     {
 248       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
 249           || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
 250         {
 251           sec_vaddr = bfd_get_section_vma (abfd, sec);
 252           sec_size = bfd_get_section_size (sec);
 253           if (sec_vaddr + sec_size > top_of_data_memory)
 254             top_of_data_memory = sec_vaddr + sec_size;
 255         }
 256     }
 257
 258   /* Now get the top-of-heap by calling sbrk in the inferior.  */
 259   if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
 260     {
 261       sbrk = find_function_in_inferior ("sbrk");
 262       if (sbrk == NULL)
 263         return 0;
 264     }
 265   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
 266     {
 267       sbrk = find_function_in_inferior ("_sbrk");
 268       if (sbrk == NULL)
 269         return 0;
 270     }
 271   else
 272     return 0;
 273
 274   zero = value_from_longest (builtin_type_int, 0);
 275   gdb_assert (zero);
 276   sbrk = call_function_by_hand (sbrk, 1, &zero);
 277   if (sbrk == NULL)
 278     return 0;
 279   top_of_heap = value_as_long (sbrk);
 280
 281   /* Return results.  */
 282   if (top_of_heap > top_of_data_memory)
 283     {
 284       *bottom = top_of_data_memory;
 285       *top = top_of_heap;
 286       return 1;
 287     }
 288
 289   /* No additional heap space needs to be saved.  */
 290   return 0;
 291 }
 292
 293 static void
 294 make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
 295 {
 296   int p_flags = 0;
 297   int p_type;
 298
 299   /* FIXME: these constants may only be applicable for ELF.  */
 300   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
 301     p_type = PT_LOAD;
 302   else
 303     p_type = PT_NOTE;
 304
 305   p_flags |= PF_R;      /* Segment is readable.  */
 306   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
 307     p_flags |= PF_W;    /* Segment is writable.  */
 308   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
 309     p_flags |= PF_X;    /* Segment is executable.  */
 310
 311   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
 312 }
 313
 314 static int
 315 gcore_create_callback (CORE_ADDR vaddr, unsigned long size,
 316                        int read, int write, int exec, void *data)
 317 {
 318   bfd *obfd = data;
 319   asection *osec;
 320   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;
 321
 322   /* If the memory segment has no permissions set, ignore it, otherwise
 323      when we later try to access it for read/write, we'll get an error
 324      or jam the kernel.  */
 325   if (read == 0 && write == 0 && exec == 0)
 326     {
 327       if (info_verbose)
 328         {
 329           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at 0x%s\n",
 330                            paddr_d (size), paddr_nz (vaddr));
 331         }
 332
 333       return 0;
 334     }
 335
 336   if (write == 0)
 337     {
 338       /* See if this region of memory lies inside a known file on disk.
 339          If so, we can avoid copying its contents by clearing SEC_LOAD.  */
 340       struct objfile *objfile;
 341       struct obj_section *objsec;
 342
 343       ALL_OBJSECTIONS (objfile, objsec)
 344         {
 345           bfd *abfd = objfile->obfd;
 346           asection *asec = objsec->the_bfd_section;
 347           bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
 348                                                                     asec);
 349           bfd_vma start = objsec->addr & -align;
 350           bfd_vma end = (objsec->endaddr + align - 1) & -align;
 351           /* Match if either the entire memory region lies inside the
 352              section (i.e. a mapping covering some pages of a large
 353              segment) or the entire section lies inside the memory region
 354              (i.e. a mapping covering multiple small sections).
 355
 356              This BFD was synthesized from reading target memory,
 357              we don't want to omit that.  */
 358           if (((vaddr >= start && vaddr + size <= end)
 359                || (start >= vaddr && end <= vaddr + size))
 360               && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
 361             {
 362               flags &= ~SEC_LOAD;
 363               flags |= SEC_NEVER_LOAD;
 364               goto keep;        /* break out of two nested for loops */
 365             }
 366         }
 367
 368     keep:
 369       flags |= SEC_READONLY;
 370     }
 371
 372   if (exec)
 373     flags |= SEC_CODE;
 374   else
 375     flags |= SEC_DATA;
 376
 377   osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
 378   if (osec == NULL)
 379     {
 380       warning (_("Couldn't make gcore segment: %s"),
 381                bfd_errmsg (bfd_get_error ()));
 382       return 1;
 383     }
 384
 385   if (info_verbose)
 386     {
 387       fprintf_filtered (gdb_stdout, "Save segment, %s bytes at 0x%s\n",
 388                         paddr_d (size), paddr_nz (vaddr));
 389     }
 390
 391   bfd_set_section_size (obfd, osec, size);
 392   bfd_set_section_vma (obfd, osec, vaddr);
 393   bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
 394   return 0;
 395 }
 396
 397 static int
 398 objfile_find_memory_regions (int (*func) (CORE_ADDR, unsigned long,
 399                                           int, int, int, void *),
 400                              void *obfd)
 401 {
 402   /* Use objfile data to create memory sections.  */
 403   struct objfile *objfile;
 404   struct obj_section *objsec;
 405   bfd_vma temp_bottom, temp_top;
 406
 407   /* Call callback function for each objfile section.  */
 408   ALL_OBJSECTIONS (objfile, objsec)
 409     {
 410       bfd *ibfd = objfile->obfd;
 411       asection *isec = objsec->the_bfd_section;
 412       flagword flags = bfd_get_section_flags (ibfd, isec);
 413       int ret;
 414
 415       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
 416         {
 417           int size = bfd_section_size (ibfd, isec);
 418           int ret;
 419
 420           ret = (*func) (objsec->addr, bfd_section_size (ibfd, isec),
 421                          1, /* All sections will be readable.  */
 422                          (flags & SEC_READONLY) == 0, /* Writable.  */
 423                          (flags & SEC_CODE) != 0, /* Executable.  */
 424                          obfd);
 425           if (ret != 0)
 426             return ret;
 427         }
 428     }
 429
 430   /* Make a stack segment.  */
 431   if (derive_stack_segment (&temp_bottom, &temp_top))
 432     (*func) (temp_bottom, temp_top - temp_bottom,
 433              1, /* Stack section will be readable.  */
 434              1, /* Stack section will be writable.  */
 435              0, /* Stack section will not be executable.  */
 436              obfd);
 437
 438   /* Make a heap segment. */
 439   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
 440     (*func) (temp_bottom, temp_top - temp_bottom,
 441              1, /* Heap section will be readable.  */
 442              1, /* Heap section will be writable.  */
 443              0, /* Heap section will not be executable.  */
 444              obfd);
 445
 446   return 0;
 447 }
 448
 449 static void
 450 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
 451 {
 452   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
 453   file_ptr offset = 0;
 454   struct cleanup *old_chain = NULL;
 455   void *memhunk;
 456
 457   /* Read-only sections are marked; we don't have to copy their contents.  */
 458   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
 459     return;
 460
 461   /* Only interested in "load" sections.  */
 462   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
 463     return;
 464
 465   size = min (total_size, MAX_COPY_BYTES);
 466   memhunk = xmalloc (size);
 467   /* ??? This is crap since xmalloc should never return NULL.  */
 468   if (memhunk == NULL)
 469     error (_("Not enough memory to create corefile."));
 470   old_chain = make_cleanup (xfree, memhunk);
 471
 472   while (total_size > 0)
 473     {
 474       if (size > total_size)
 475         size = total_size;
 476
 477       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
 478                               memhunk, size) != 0)
 479         {
 480           warning (_("Memory read failed for corefile section, %s bytes at 0x%s."),
 481                    paddr_d (size), paddr (bfd_section_vma (obfd, osec)));
 482           break;
 483         }
 484       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
 485         {
 486           warning (_("Failed to write corefile contents (%s)."),
 487                    bfd_errmsg (bfd_get_error ()));
 488           break;
 489         }
 490
 491       total_size -= size;
 492       offset += size;
 493     }
 494
 495   do_cleanups (old_chain);      /* Frees MEMHUNK.  */
 496 }
 497
 498 static int
 499 gcore_memory_sections (bfd *obfd)
 500 {
 501   if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
 502     return 0;                   /* FIXME: error return/msg?  */
 503
 504   /* Record phdrs for section-to-segment mapping.  */
 505   bfd_map_over_sections (obfd, make_output_phdrs, NULL);
 506
 507   /* Copy memory region contents.  */
 508   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);
 509
 510   return 1;
 511 }
 512
 513 void
 514 _initialize_gcore (void)
 515 {
 516   add_com ("generate-core-file", class_files, gcore_command, _("\
 517 Save a core file with the current state of the debugged process.\n\
 518 Argument is optional filename.  Default filename is 'core.<process_id>'."));
 519
 520   add_com_alias ("gcore", "generate-core-file", class_files, 1);
 521   exec_set_find_memory_regions (objfile_find_memory_regions);
 522 }