gdb/gcore.c - gdb

Functions defined

Macros defined

Source code

  1. /* Generate a core file for the inferior process.

  3.    Copyright (C) 2001-2015 Free Software Foundation, Inc.

  5.    This file is part of GDB.

  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.

  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.

  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/>.  */

  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 <fcntl.h>
  33. #include "regcache.h"
  34. #include "regset.h"
  35. #include "gdb_bfd.h"
  36. #include "readline/tilde.h"

  38. /* The largest amount of memory to read from the target at once.  We
  39.    must throttle it to limit the amount of memory used by GDB during
  40.    generate-core-file for programs with large resident data.  */
  41. ‌#define MAX_COPY_BYTES (1024 * 1024)

  43. static const char *default_gcore_target (void);
  44. static enum bfd_architecture default_gcore_arch (void);
  45. static unsigned long default_gcore_mach (void);
  46. static int gcore_memory_sections (bfd *);

  48. /* create_gcore_bfd -- helper for gcore_command (exported).
  49.    Open a new bfd core file for output, and return the handle.  */

  51. bfd *
  52. ‌create_gcore_bfd (const char *filename)
  53. {
  54.   bfd *obfd = gdb_bfd_openw (filename, default_gcore_target ());

  56.   if (!obfd)
  57.     error (_("Failed to open '%s' for output."), filename);
  58.   bfd_set_format (obfd, bfd_core);
  59.   bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());
  60.   return obfd;
  61. }

  63. /* write_gcore_file_1 -- do the actual work of write_gcore_file.  */

  65. static void
  66. ‌write_gcore_file_1 (bfd *obfd)
  67. {
  68.   struct cleanup *cleanup;
  69.   void *note_data = NULL;
  70.   int note_size = 0;
  71.   asection *note_sec = NULL;

  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);

  82.   cleanup = make_cleanup (xfree, note_data);

  84.   if (note_data == NULL || note_size == 0)
  85.     error (_("Target does not support core file generation."));

  87.   /* Create the note section.  */
  88.   note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
  89.                                                  SEC_HAS_CONTENTS
  90.                                                  | SEC_READONLY
  91.                                                  | SEC_ALLOC);
  92.   if (note_sec == NULL)
  93.     error (_("Failed to create 'note' section for corefile: %s"),
  94.            bfd_errmsg (bfd_get_error ()));

  96.   bfd_set_section_vma (obfd, note_sec, 0);
  97.   bfd_set_section_alignment (obfd, note_sec, 0);
  98.   bfd_set_section_size (obfd, note_sec, note_size);

  100.   /* Now create the memory/load sections.  */
  101.   if (gcore_memory_sections (obfd) == 0)
  102.     error (_("gcore: failed to get corefile memory sections from target."));

  104.   /* Write out the contents of the note section.  */
  105.   if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
  106.     warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));

  108.   do_cleanups (cleanup);
  109. }

  111. /* write_gcore_file -- helper for gcore_command (exported).
  112.    Compose and write the corefile data to the core file.  */

  114. void
  115. ‌write_gcore_file (bfd *obfd)
  116. {
  117.   volatile struct gdb_exception except;

  119.   target_prepare_to_generate_core ();

  121.   TRY_CATCH (except, RETURN_MASK_ALL)
  122.     write_gcore_file_1 (obfd);

  124.   target_done_generating_core ();

  126.   if (except.reason < 0)
  127.     throw_exception (except);
  128. }

  130. static void
  131. ‌do_bfd_delete_cleanup (void *arg)
  132. {
  133.   bfd *obfd = arg;
  134.   const char *filename = obfd->filename;

  136.   gdb_bfd_unref (arg);
  137.   unlink (filename);
  138. }

  140. /* gcore_command -- implements the 'gcore' command.
  141.    Generate a core file from the inferior process.  */

  143. static void
  144. ‌gcore_command (char *args, int from_tty)
  145. {
  146.   struct cleanup *filename_chain;
  147.   struct cleanup *bfd_chain;
  148.   char *corefilename;
  149.   bfd *obfd;

  151.   /* No use generating a corefile without a target process.  */
  152.   if (!target_has_execution)
  153.     noprocess ();

  155.   if (args && *args)
  156.     corefilename = tilde_expand (args);
  157.   else
  158.     {
  159.       /* Default corefile name is "core.PID".  */
  160.       corefilename = xstrprintf ("core.%d", ptid_get_pid (inferior_ptid));
  161.     }
  162.   filename_chain = make_cleanup (xfree, corefilename);

  164.   if (info_verbose)
  165.     fprintf_filtered (gdb_stdout,
  166.                       "Opening corefile '%s' for output.\n", corefilename);

  168.   /* Open the output file.  */
  169.   obfd = create_gcore_bfd (corefilename);

  171.   /* Need a cleanup that will close and delete the file.  */
  172.   bfd_chain = make_cleanup (do_bfd_delete_cleanup, obfd);

  174.   /* Call worker function.  */
  175.   write_gcore_file (obfd);

  177.   /* Succeeded.  */
  178.   discard_cleanups (bfd_chain);
  179.   gdb_bfd_unref (obfd);

  181.   fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
  182.   do_cleanups (filename_chain);
  183. }

  185. static unsigned long
  186. ‌default_gcore_mach (void)
  187. {
  188. #if 1        /* See if this even matters...  */
  189.   return 0;
  190. #else

  192.   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ());

  194.   if (bfdarch != NULL)
  195.     return bfdarch->mach;
  196.   if (exec_bfd == NULL)
  197.     error (_("Can't find default bfd machine type (need execfile)."));

  199.   return bfd_get_mach (exec_bfd);
  200. #endif /* 1 */
  201. }

  203. static enum bfd_architecture
  204. ‌default_gcore_arch (void)
  205. {
  206.   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ());

  208.   if (bfdarch != NULL)
  209.     return bfdarch->arch;
  210.   if (exec_bfd == NULL)
  211.     error (_("Can't find bfd architecture for corefile (need execfile)."));

  213.   return bfd_get_arch (exec_bfd);
  214. }

  216. static const char *
  217. ‌default_gcore_target (void)
  218. {
  219.   /* The gdbarch may define a target to use for core files.  */
  220.   if (gdbarch_gcore_bfd_target_p (target_gdbarch ()))
  221.     return gdbarch_gcore_bfd_target (target_gdbarch ());

  223.   /* Otherwise, try to fall back to the exec_bfd target.  This will probably
  224.      not work for non-ELF targets.  */
  225.   if (exec_bfd == NULL)
  226.     return NULL;
  227.   else
  228.     return bfd_get_target (exec_bfd);
  229. }

  231. /* Derive a reasonable stack segment by unwinding the target stack,
  232.    and store its limits in *BOTTOM and *TOP.  Return non-zero if
  233.    successful.  */

  235. static int
  236. ‌derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
  237. {
  238.   struct frame_info *fi, *tmp_fi;

  240.   gdb_assert (bottom);
  241.   gdb_assert (top);

  243.   /* Can't succeed without stack and registers.  */
  244.   if (!target_has_stack || !target_has_registers)
  245.     return 0;

  247.   /* Can't succeed without current frame.  */
  248.   fi = get_current_frame ();
  249.   if (fi == NULL)
  250.     return 0;

  252.   /* Save frame pointer of TOS frame.  */
  253.   *top = get_frame_base (fi);
  254.   /* If current stack pointer is more "inner", use that instead.  */
  255.   if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top))
  256.     *top = get_frame_sp (fi);

  258.   /* Find prev-most frame.  */
  259.   while ((tmp_fi = get_prev_frame (fi)) != NULL)
  260.     fi = tmp_fi;

  262.   /* Save frame pointer of prev-most frame.  */
  263.   *bottom = get_frame_base (fi);

  265.   /* Now canonicalize their order, so that BOTTOM is a lower address
  266.      (as opposed to a lower stack frame).  */
  267.   if (*bottom > *top)
  268.     {
  269.       bfd_vma tmp_vma;

  271.       tmp_vma = *top;
  272.       *top = *bottom;
  273.       *bottom = tmp_vma;
  274.     }

  276.   return 1;
  277. }

  279. /* call_target_sbrk --
  280.    helper function for derive_heap_segment.  */

  282. static bfd_vma
  283. ‌call_target_sbrk (int sbrk_arg)
  284. {
  285.   struct objfile *sbrk_objf;
  286.   struct gdbarch *gdbarch;
  287.   bfd_vma top_of_heap;
  288.   struct value *target_sbrk_arg;
  289.   struct value *sbrk_fn, *ret;
  290.   bfd_vma tmp;

  292.   if (lookup_minimal_symbol ("sbrk", NULL, NULL).minsym != NULL)
  293.     {
  294.       sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf);
  295.       if (sbrk_fn == NULL)
  296.         return (bfd_vma) 0;
  297.     }
  298.   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL).minsym != NULL)
  299.     {
  300.       sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf);
  301.       if (sbrk_fn == NULL)
  302.         return (bfd_vma) 0;
  303.     }
  304.   else
  305.     return (bfd_vma) 0;

  307.   gdbarch = get_objfile_arch (sbrk_objf);
  308.   target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int,
  309.                                         sbrk_arg);
  310.   gdb_assert (target_sbrk_arg);
  311.   ret = call_function_by_hand (sbrk_fn, 1, &target_sbrk_arg);
  312.   if (ret == NULL)
  313.     return (bfd_vma) 0;

  315.   tmp = value_as_long (ret);
  316.   if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff)
  317.     return (bfd_vma) 0;

  319.   top_of_heap = tmp;
  320.   return top_of_heap;
  321. }

  323. /* Derive a reasonable heap segment for ABFD by looking at sbrk and
  324.    the static data sections.  Store its limits in *BOTTOM and *TOP.
  325.    Return non-zero if successful.  */

  327. static int
  328. ‌derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
  329. {
  330.   bfd_vma top_of_data_memory = 0;
  331.   bfd_vma top_of_heap = 0;
  332.   bfd_size_type sec_size;
  333.   bfd_vma sec_vaddr;
  334.   asection *sec;

  336.   gdb_assert (bottom);
  337.   gdb_assert (top);

  339.   /* This function depends on being able to call a function in the
  340.      inferior.  */
  341.   if (!target_has_execution)
  342.     return 0;

  344.   /* The following code assumes that the link map is arranged as
  345.      follows (low to high addresses):

  347.      ---------------------------------
  348.      | text sections                 |
  349.      ---------------------------------
  350.      | data sections (including bss) |
  351.      ---------------------------------
  352.      | heap                          |
  353.      --------------------------------- */

  355.   for (sec = abfd->sections; sec; sec = sec->next)
  356.     {
  357.       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
  358.           || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
  359.         {
  360.           sec_vaddr = bfd_get_section_vma (abfd, sec);
  361.           sec_size = bfd_get_section_size (sec);
  362.           if (sec_vaddr + sec_size > top_of_data_memory)
  363.             top_of_data_memory = sec_vaddr + sec_size;
  364.         }
  365.     }

  367.   top_of_heap = call_target_sbrk (0);
  368.   if (top_of_heap == (bfd_vma) 0)
  369.     return 0;

  371.   /* Return results.  */
  372.   if (top_of_heap > top_of_data_memory)
  373.     {
  374.       *bottom = top_of_data_memory;
  375.       *top = top_of_heap;
  376.       return 1;
  377.     }

  379.   /* No additional heap space needs to be saved.  */
  380.   return 0;
  381. }

  383. static void
  384. ‌make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
  385. {
  386.   int p_flags = 0;
  387.   int p_type = 0;

  389.   /* FIXME: these constants may only be applicable for ELF.  */
  390.   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
  391.     p_type = PT_LOAD;
  392.   else if (strncmp (bfd_section_name (obfd, osec), "note", 4) == 0)
  393.     p_type = PT_NOTE;
  394.   else
  395.     p_type = PT_NULL;

  397.   p_flags |= PF_R;        /* Segment is readable.  */
  398.   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
  399.     p_flags |= PF_W;        /* Segment is writable.  */
  400.   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
  401.     p_flags |= PF_X;        /* Segment is executable.  */

  403.   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
  404. }

  406. /* find_memory_region_ftype implementation.  DATA is 'bfd *' for the core file
  407.    GDB is creating.  */

  409. static int
  410. ‌gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
  411.                        int write, int exec, int modified, void *data)
  412. {
  413.   bfd *obfd = data;
  414.   asection *osec;
  415.   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;

  417.   /* If the memory segment has no permissions set, ignore it, otherwise
  418.      when we later try to access it for read/write, we'll get an error
  419.      or jam the kernel.  */
  420.   if (read == 0 && write == 0 && exec == 0 && modified == 0)
  421.     {
  422.       if (info_verbose)
  423.         {
  424.           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n",
  425.                             plongest (size), paddress (target_gdbarch (), vaddr));
  426.         }

  428.       return 0;
  429.     }

  431.   if (write == 0 && modified == 0 && !solib_keep_data_in_core (vaddr, size))
  432.     {
  433.       /* See if this region of memory lies inside a known file on disk.
  434.          If so, we can avoid copying its contents by clearing SEC_LOAD.  */
  435.       struct objfile *objfile;
  436.       struct obj_section *objsec;

  438.       ALL_OBJSECTIONS (objfile, objsec)
  439.         {
  440.           bfd *abfd = objfile->obfd;
  441.           asection *asec = objsec->the_bfd_section;
  442.           bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
  443.                                                                     asec);
  444.           bfd_vma start = obj_section_addr (objsec) & -align;
  445.           bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align;

  447.           /* Match if either the entire memory region lies inside the
  448.              section (i.e. a mapping covering some pages of a large
  449.              segment) or the entire section lies inside the memory region
  450.              (i.e. a mapping covering multiple small sections).

  452.              This BFD was synthesized from reading target memory,
  453.              we don't want to omit that.  */
  454.           if (objfile->separate_debug_objfile_backlink == NULL
  455.               && ((vaddr >= start && vaddr + size <= end)
  456.                   || (start >= vaddr && end <= vaddr + size))
  457.               && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
  458.             {
  459.               flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS);
  460.               goto keep;        /* Break out of two nested for loops.  */
  461.             }
  462.         }

  464.     keep:;
  465.     }

  467.   if (write == 0)
  468.     flags |= SEC_READONLY;

  470.   if (exec)
  471.     flags |= SEC_CODE;
  472.   else
  473.     flags |= SEC_DATA;

  475.   osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
  476.   if (osec == NULL)
  477.     {
  478.       warning (_("Couldn't make gcore segment: %s"),
  479.                bfd_errmsg (bfd_get_error ()));
  480.       return 1;
  481.     }

  483.   if (info_verbose)
  484.     {
  485.       fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n",
  486.                         plongest (size), paddress (target_gdbarch (), vaddr));
  487.     }

  489.   bfd_set_section_size (obfd, osec, size);
  490.   bfd_set_section_vma (obfd, osec, vaddr);
  491.   bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
  492.   return 0;
  493. }

  495. int
  496. ‌objfile_find_memory_regions (struct target_ops *self,
  497.                              find_memory_region_ftype func, void *obfd)
  498. {
  499.   /* Use objfile data to create memory sections.  */
  500.   struct objfile *objfile;
  501.   struct obj_section *objsec;
  502.   bfd_vma temp_bottom, temp_top;

  504.   /* Call callback function for each objfile section.  */
  505.   ALL_OBJSECTIONS (objfile, objsec)
  506.     {
  507.       bfd *ibfd = objfile->obfd;
  508.       asection *isec = objsec->the_bfd_section;
  509.       flagword flags = bfd_get_section_flags (ibfd, isec);

  511.       /* Separate debug info files are irrelevant for gcore.  */
  512.       if (objfile->separate_debug_objfile_backlink != NULL)
  513.         continue;

  515.       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
  516.         {
  517.           int size = bfd_section_size (ibfd, isec);
  518.           int ret;

  520.           ret = (*func) (obj_section_addr (objsec), size,
  521.                          1, /* All sections will be readable.  */
  522.                          (flags & SEC_READONLY) == 0, /* Writable.  */
  523.                          (flags & SEC_CODE) != 0, /* Executable.  */
  524.                          1, /* MODIFIED is unknown, pass it as true.  */
  525.                          obfd);
  526.           if (ret != 0)
  527.             return ret;
  528.         }
  529.     }

  531.   /* Make a stack segment.  */
  532.   if (derive_stack_segment (&temp_bottom, &temp_top))
  533.     (*func) (temp_bottom, temp_top - temp_bottom,
  534.              1, /* Stack section will be readable.  */
  535.              1, /* Stack section will be writable.  */
  536.              0, /* Stack section will not be executable.  */
  537.              1, /* Stack section will be modified.  */
  538.              obfd);

  540.   /* Make a heap segment.  */
  541.   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
  542.     (*func) (temp_bottom, temp_top - temp_bottom,
  543.              1, /* Heap section will be readable.  */
  544.              1, /* Heap section will be writable.  */
  545.              0, /* Heap section will not be executable.  */
  546.              1, /* Heap section will be modified.  */
  547.              obfd);

  549.   return 0;
  550. }

  552. static void
  553. ‌gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
  554. {
  555.   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
  556.   file_ptr offset = 0;
  557.   struct cleanup *old_chain = NULL;
  558.   void *memhunk;

  560.   /* Read-only sections are marked; we don't have to copy their contents.  */
  561.   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
  562.     return;

  564.   /* Only interested in "load" sections.  */
  565.   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
  566.     return;

  568.   size = min (total_size, MAX_COPY_BYTES);
  569.   memhunk = xmalloc (size);
  570.   old_chain = make_cleanup (xfree, memhunk);

  572.   while (total_size > 0)
  573.     {
  574.       if (size > total_size)
  575.         size = total_size;

  577.       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
  578.                               memhunk, size) != 0)
  579.         {
  580.           warning (_("Memory read failed for corefile "
  581.                      "section, %s bytes at %s."),
  582.                    plongest (size),
  583.                    paddress (target_gdbarch (), bfd_section_vma (obfd, osec)));
  584.           break;
  585.         }
  586.       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
  587.         {
  588.           warning (_("Failed to write corefile contents (%s)."),
  589.                    bfd_errmsg (bfd_get_error ()));
  590.           break;
  591.         }

  593.       total_size -= size;
  594.       offset += size;
  595.     }

  597.   do_cleanups (old_chain);        /* Frees MEMHUNK.  */
  598. }

  600. static int
  601. ‌gcore_memory_sections (bfd *obfd)
  602. {
  603.   /* Try gdbarch method first, then fall back to target method.  */
  604.   if (!gdbarch_find_memory_regions_p (target_gdbarch ())
  605.       || gdbarch_find_memory_regions (target_gdbarch (),
  606.                                       gcore_create_callback, obfd) != 0)
  607.     {
  608.       if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
  609.         return 0;                        /* FIXME: error return/msg?  */
  610.     }

  612.   /* Record phdrs for section-to-segment mapping.  */
  613.   bfd_map_over_sections (obfd, make_output_phdrs, NULL);

  615.   /* Copy memory region contents.  */
  616.   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);

  618.   return 1;
  619. }

  621. /* Provide a prototype to silence -Wmissing-prototypes.  */
  622. extern initialize_file_ftype _initialize_gcore;

  624. void
  625. ‌_initialize_gcore (void)
  626. {
  627.   add_com ("generate-core-file", class_files, gcore_command, _("\
  628. Save a core file with the current state of the debugged process.\n\
  629. Argument is optional filename.  Default filename is 'core.<process_id>'."));

  631.   add_com_alias ("gcore", "generate-core-file", class_files, 1);
  632. }