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