gdb/gcore.c

   1 /* Generate a core file for the inferior process.
   2
   3    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
   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 #ifdef TARGET_ARCHITECTURE
 129   const struct bfd_arch_info *bfdarch = TARGET_ARCHITECTURE;
 130
 131   if (bfdarch != NULL)
 132     return bfdarch->mach;
 133 #endif /* TARGET_ARCHITECTURE */
 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 #ifdef TARGET_ARCHITECTURE
 145   const struct bfd_arch_info * bfdarch = TARGET_ARCHITECTURE;
 146
 147   if (bfdarch != NULL)
 148     return bfdarch->arch;
 149 #endif
 150   if (exec_bfd == NULL)
 151     error (_("Can't find bfd architecture for corefile (need execfile)."));
 152
 153   return bfd_get_arch (exec_bfd);
 154 }
 155
 156 static char *
 157 default_gcore_target (void)
 158 {
 159   /* FIXME: This may only work for ELF targets.  */
 160   if (exec_bfd == NULL)
 161     return NULL;
 162   else
 163     return bfd_get_target (exec_bfd);
 164 }
 165
 166 /* Derive a reasonable stack segment by unwinding the target stack,
 167    and store its limits in *BOTTOM and *TOP.  Return non-zero if
 168    successful.  */
 169
 170 static int
 171 derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
 172 {
 173   struct frame_info *fi, *tmp_fi;
 174
 175   gdb_assert (bottom);
 176   gdb_assert (top);
 177
 178   /* Can't succeed without stack and registers.  */
 179   if (!target_has_stack || !target_has_registers)
 180     return 0;
 181
 182   /* Can't succeed without current frame.  */
 183   fi = get_current_frame ();
 184   if (fi == NULL)
 185     return 0;
 186
 187   /* Save frame pointer of TOS frame.  */
 188   *top = get_frame_base (fi);
 189   /* If current stack pointer is more "inner", use that instead.  */
 190   if (INNER_THAN (read_sp (), *top))
 191     *top = read_sp ();
 192
 193   /* Find prev-most frame.  */
 194   while ((tmp_fi = get_prev_frame (fi)) != NULL)
 195     fi = tmp_fi;
 196
 197   /* Save frame pointer of prev-most frame.  */
 198   *bottom = get_frame_base (fi);
 199
 200   /* Now canonicalize their order, so that BOTTOM is a lower address
 201      (as opposed to a lower stack frame).  */
 202   if (*bottom > *top)
 203     {
 204       bfd_vma tmp_vma;
 205
 206       tmp_vma = *top;
 207       *top = *bottom;
 208       *bottom = tmp_vma;
 209     }
 210
 211   return 1;
 212 }
 213
 214 /* Derive a reasonable heap segment for ABFD by looking at sbrk and
 215    the static data sections.  Store its limits in *BOTTOM and *TOP.
 216    Return non-zero if successful.  */
 217
 218 static int
 219 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
 220 {
 221   bfd_vma top_of_data_memory = 0;
 222   bfd_vma top_of_heap = 0;
 223   bfd_size_type sec_size;
 224   struct value *zero, *sbrk;
 225   bfd_vma sec_vaddr;
 226   asection *sec;
 227
 228   gdb_assert (bottom);
 229   gdb_assert (top);
 230
 231   /* This function depends on being able to call a function in the
 232      inferior.  */
 233   if (!target_has_execution)
 234     return 0;
 235
 236   /* The following code assumes that the link map is arranged as
 237      follows (low to high addresses):
 238
 239      ---------------------------------
 240      | text sections                 |
 241      ---------------------------------
 242      | data sections (including bss) |
 243      ---------------------------------
 244      | heap                          |
 245      --------------------------------- */
 246
 247   for (sec = abfd->sections; sec; sec = sec->next)
 248     {
 249       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
 250           || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
 251         {
 252           sec_vaddr = bfd_get_section_vma (abfd, sec);
 253           sec_size = bfd_get_section_size (sec);
 254           if (sec_vaddr + sec_size > top_of_data_memory)
 255             top_of_data_memory = sec_vaddr + sec_size;
 256         }
 257     }
 258
 259   /* Now get the top-of-heap by calling sbrk in the inferior.  */
 260   if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
 261     {
 262       sbrk = find_function_in_inferior ("sbrk");
 263       if (sbrk == NULL)
 264         return 0;
 265     }
 266   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
 267     {
 268       sbrk = find_function_in_inferior ("_sbrk");
 269       if (sbrk == NULL)
 270         return 0;
 271     }
 272   else
 273     return 0;
 274
 275   zero = value_from_longest (builtin_type_int, 0);
 276   gdb_assert (zero);
 277   sbrk = call_function_by_hand (sbrk, 1, &zero);
 278   if (sbrk == NULL)
 279     return 0;
 280   top_of_heap = value_as_long (sbrk);
 281
 282   /* Return results.  */
 283   if (top_of_heap > top_of_data_memory)
 284     {
 285       *bottom = top_of_data_memory;
 286       *top = top_of_heap;
 287       return 1;
 288     }
 289
 290   /* No additional heap space needs to be saved.  */
 291   return 0;
 292 }
 293
 294 static void
 295 make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
 296 {
 297   int p_flags = 0;
 298   int p_type;
 299
 300   /* FIXME: these constants may only be applicable for ELF.  */
 301   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
 302     p_type = PT_LOAD;
 303   else
 304     p_type = PT_NOTE;
 305
 306   p_flags |= PF_R;      /* Segment is readable.  */
 307   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
 308     p_flags |= PF_W;    /* Segment is writable.  */
 309   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
 310     p_flags |= PF_X;    /* Segment is executable.  */
 311
 312   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
 313 }
 314
 315 static int
 316 gcore_create_callback (CORE_ADDR vaddr, unsigned long size,
 317                        int read, int write, int exec, void *data)
 318 {
 319   bfd *obfd = data;
 320   asection *osec;
 321   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;
 322
 323   /* If the memory segment has no permissions set, ignore it, otherwise
 324      when we later try to access it for read/write, we'll get an error
 325      or jam the kernel.  */
 326   if (read == 0 && write == 0 && exec == 0)
 327     {
 328       if (info_verbose)
 329         {
 330           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at 0x%s\n",
 331                            paddr_d (size), paddr_nz (vaddr));
 332         }
 333
 334       return 0;
 335     }
 336
 337   if (write == 0)
 338     {
 339       /* See if this region of memory lies inside a known file on disk.
 340          If so, we can avoid copying its contents by clearing SEC_LOAD.  */
 341       struct objfile *objfile;
 342       struct obj_section *objsec;
 343
 344       ALL_OBJSECTIONS (objfile, objsec)
 345         {
 346           bfd *abfd = objfile->obfd;
 347           asection *asec = objsec->the_bfd_section;
 348           bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
 349                                                                     asec);
 350           bfd_vma start = objsec->addr & -align;
 351           bfd_vma end = (objsec->endaddr + align - 1) & -align;
 352           /* Match if either the entire memory region lies inside the
 353              section (i.e. a mapping covering some pages of a large
 354              segment) or the entire section lies inside the memory region
 355              (i.e. a mapping covering multiple small sections).
 356
 357              This BFD was synthesized from reading target memory,
 358              we don't want to omit that.  */
 359           if (((vaddr >= start && vaddr + size <= end)
 360                || (start >= vaddr && end <= vaddr + size))
 361               && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
 362             {
 363               flags &= ~SEC_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 (obfd, "load");
 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   bfd_set_section_flags (obfd, osec, flags);
 395   return 0;
 396 }
 397
 398 static int
 399 objfile_find_memory_regions (int (*func) (CORE_ADDR, unsigned long,
 400                                           int, int, int, void *),
 401                              void *obfd)
 402 {
 403   /* Use objfile data to create memory sections.  */
 404   struct objfile *objfile;
 405   struct obj_section *objsec;
 406   bfd_vma temp_bottom, temp_top;
 407
 408   /* Call callback function for each objfile section.  */
 409   ALL_OBJSECTIONS (objfile, objsec)
 410     {
 411       bfd *ibfd = objfile->obfd;
 412       asection *isec = objsec->the_bfd_section;
 413       flagword flags = bfd_get_section_flags (ibfd, isec);
 414       int ret;
 415
 416       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
 417         {
 418           int size = bfd_section_size (ibfd, isec);
 419           int ret;
 420
 421           ret = (*func) (objsec->addr, bfd_section_size (ibfd, isec),
 422                          1, /* All sections will be readable.  */
 423                          (flags & SEC_READONLY) == 0, /* Writable.  */
 424                          (flags & SEC_CODE) != 0, /* Executable.  */
 425                          obfd);
 426           if (ret != 0)
 427             return ret;
 428         }
 429     }
 430
 431   /* Make a stack segment.  */
 432   if (derive_stack_segment (&temp_bottom, &temp_top))
 433     (*func) (temp_bottom, temp_top - temp_bottom,
 434              1, /* Stack section will be readable.  */
 435              1, /* Stack section will be writable.  */
 436              0, /* Stack section will not be executable.  */
 437              obfd);
 438
 439   /* Make a heap segment. */
 440   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
 441     (*func) (temp_bottom, temp_top - temp_bottom,
 442              1, /* Heap section will be readable.  */
 443              1, /* Heap section will be writable.  */
 444              0, /* Heap section will not be executable.  */
 445              obfd);
 446
 447   return 0;
 448 }
 449
 450 static void
 451 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
 452 {
 453   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
 454   file_ptr offset = 0;
 455   struct cleanup *old_chain = NULL;
 456   void *memhunk;
 457
 458   /* Read-only sections are marked; we don't have to copy their contents.  */
 459   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
 460     return;
 461
 462   /* Only interested in "load" sections.  */
 463   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
 464     return;
 465
 466   size = min (total_size, MAX_COPY_BYTES);
 467   memhunk = xmalloc (size);
 468   /* ??? This is crap since xmalloc should never return NULL.  */
 469   if (memhunk == NULL)
 470     error (_("Not enough memory to create corefile."));
 471   old_chain = make_cleanup (xfree, memhunk);
 472
 473   while (total_size > 0)
 474     {
 475       if (size > total_size)
 476         size = total_size;
 477
 478       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
 479                               memhunk, size) != 0)
 480         {
 481           warning (_("Memory read failed for corefile section, %s bytes at 0x%s."),
 482                    paddr_d (size), paddr (bfd_section_vma (obfd, osec)));
 483           break;
 484         }
 485       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
 486         {
 487           warning (_("Failed to write corefile contents (%s)."),
 488                    bfd_errmsg (bfd_get_error ()));
 489           break;
 490         }
 491
 492       total_size -= size;
 493       offset += size;
 494     }
 495
 496   do_cleanups (old_chain);      /* Frees MEMHUNK.  */
 497 }
 498
 499 static int
 500 gcore_memory_sections (bfd *obfd)
 501 {
 502   if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
 503     return 0;                   /* FIXME: error return/msg?  */
 504
 505   /* Record phdrs for section-to-segment mapping.  */
 506   bfd_map_over_sections (obfd, make_output_phdrs, NULL);
 507
 508   /* Copy memory region contents.  */
 509   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);
 510
 511   return 1;
 512 }
 513
 514 void
 515 _initialize_gcore (void)
 516 {
 517   add_com ("generate-core-file", class_files, gcore_command, _("\
 518 Save a core file with the current state of the debugged process.\n\
 519 Argument is optional filename.  Default filename is 'core.<process_id>'."));
 520
 521   add_com_alias ("gcore", "generate-core-file", class_files, 1);
 522   exec_set_find_memory_regions (objfile_find_memory_regions);
 523 }