gdb/gcore.c

/* Generate a core file for the inferior process.

   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "elf-bfd.h"
#include "infcall.h"
#include "inferior.h"
#include "gdbcore.h"
#include "objfiles.h"
#include "symfile.h"

#include "cli/cli-decode.h"

#include "gdb_assert.h"

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

static const char *default_gcore_target (void);
static enum bfd_architecture default_gcore_arch (void);
static unsigned long default_gcore_mach (void);
static int gcore_memory_sections (bfd *);

/* Generate a core file from the inferior process.  */

static void
gcore_command (char *args, int from_tty)
{
  struct cleanup *old_chain;
  char *corefilename, corefilename_buffer[40];
  asection *note_sec = NULL;
  bfd *obfd;
  void *note_data = NULL;
  int note_size = 0;

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

  if (args && *args)
    corefilename = args;
  else
    {
      /* Default corefile name is "core.PID".  */
      sprintf (corefilename_buffer, "core.%d", PIDGET (inferior_ptid));
      corefilename = corefilename_buffer;
    }

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

  /* Open the output file.  */
  obfd = bfd_openw (corefilename, default_gcore_target ());
  if (!obfd)
    error (_("Failed to open '%s' for output."), corefilename);

  /* Need a cleanup that will close the file (FIXME: delete it?).  */
  old_chain = make_cleanup_bfd_close (obfd);

  bfd_set_format (obfd, bfd_core);
  bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());

  /* An external target method must build the notes section.  */
  note_data = target_make_corefile_notes (obfd, &note_size);

  /* Create the note section.  */
  if (note_data != NULL && note_size != 0)
    {
      note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
						     SEC_HAS_CONTENTS
						     | SEC_READONLY
						     | SEC_ALLOC);
      if (note_sec == NULL)
	error (_("Failed to create 'note' section for corefile: %s"),
	       bfd_errmsg (bfd_get_error ()));

      bfd_set_section_vma (obfd, note_sec, 0);
      bfd_set_section_alignment (obfd, note_sec, 0);
      bfd_set_section_size (obfd, note_sec, note_size);
    }

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

  /* Write out the contents of the note section.  */
  if (note_data != NULL && note_size != 0)
    {
      if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
	warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));
    }

  /* Succeeded.  */
  fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);

  /* Clean-ups will close the output file and free malloc memory.  */
  do_cleanups (old_chain);
  return;
}

static unsigned long
default_gcore_mach (void)
{
#if 1	/* See if this even matters...  */
  return 0;
#else

  const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch);

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

  return bfd_get_mach (exec_bfd);
#endif /* 1 */
}

static enum bfd_architecture
default_gcore_arch (void)
{
  const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch);

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

  return bfd_get_arch (exec_bfd);
}

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

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

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

static int
derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
{
  struct frame_info *fi, *tmp_fi;

  gdb_assert (bottom);
  gdb_assert (top);

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

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

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

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

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

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

      tmp_vma = *top;
      *top = *bottom;
      *bottom = tmp_vma;
    }

  return 1;
}

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

static int
derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
{
  struct objfile *sbrk_objf;
  struct gdbarch *gdbarch;
  bfd_vma top_of_data_memory = 0;
  bfd_vma top_of_heap = 0;
  bfd_size_type sec_size;
  struct value *zero, *sbrk;
  bfd_vma sec_vaddr;
  asection *sec;

  gdb_assert (bottom);
  gdb_assert (top);

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

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

     ---------------------------------
     | text sections                 |
     ---------------------------------
     | data sections (including bss) |
     ---------------------------------
     | heap                          |
     --------------------------------- */

  for (sec = abfd->sections; sec; sec = sec->next)
    {
      if (bfd_get_section_flags (abfd, sec) & SEC_DATA
	  || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
	{
	  sec_vaddr = bfd_get_section_vma (abfd, sec);
	  sec_size = bfd_get_section_size (sec);
	  if (sec_vaddr + sec_size > top_of_data_memory)
	    top_of_data_memory = sec_vaddr + sec_size;
	}
    }

  /* Now get the top-of-heap by calling sbrk in the inferior.  */
  if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
    {
      sbrk = find_function_in_inferior ("sbrk", &sbrk_objf);
      if (sbrk == NULL)
	return 0;
    }
  else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
    {
      sbrk = find_function_in_inferior ("_sbrk", &sbrk_objf);
      if (sbrk == NULL)
	return 0;
    }
  else
    return 0;

  gdbarch = get_objfile_arch (sbrk_objf);
  zero = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
  gdb_assert (zero);
  sbrk = call_function_by_hand (sbrk, 1, &zero);
  if (sbrk == NULL)
    return 0;
  top_of_heap = value_as_long (sbrk);

  /* Return results.  */
  if (top_of_heap > top_of_data_memory)
    {
      *bottom = top_of_data_memory;
      *top = top_of_heap;
      return 1;
    }

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

static void
make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
{
  int p_flags = 0;
  int p_type;

  /* FIXME: these constants may only be applicable for ELF.  */
  if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
    p_type = PT_LOAD;
  else
    p_type = PT_NOTE;

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

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

static int
gcore_create_callback (CORE_ADDR vaddr, unsigned long size,
		       int read, int write, int exec, void *data)
{
  bfd *obfd = data;
  asection *osec;
  flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;

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

      return 0;
    }

  if (write == 0)
    {
      /* See if this region of memory lies inside a known file on disk.
	 If so, we can avoid copying its contents by clearing SEC_LOAD.  */
      struct objfile *objfile;
      struct obj_section *objsec;

      ALL_OBJSECTIONS (objfile, objsec)
	{
	  bfd *abfd = objfile->obfd;
	  asection *asec = objsec->the_bfd_section;
	  bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
								    asec);
	  bfd_vma start = obj_section_addr (objsec) & -align;
	  bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align;
	  /* Match if either the entire memory region lies inside the
	     section (i.e. a mapping covering some pages of a large
	     segment) or the entire section lies inside the memory region
	     (i.e. a mapping covering multiple small sections).

	     This BFD was synthesized from reading target memory,
	     we don't want to omit that.  */
	  if (((vaddr >= start && vaddr + size <= end)
	       || (start >= vaddr && end <= vaddr + size))
	      && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
	    {
	      flags &= ~SEC_LOAD;
	      flags |= SEC_NEVER_LOAD;
	      goto keep;	/* break out of two nested for loops */
	    }
	}

    keep:
      flags |= SEC_READONLY;
    }

  if (exec)
    flags |= SEC_CODE;
  else
    flags |= SEC_DATA;

  osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
  if (osec == NULL)
    {
      warning (_("Couldn't make gcore segment: %s"),
	       bfd_errmsg (bfd_get_error ()));
      return 1;
    }

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

  bfd_set_section_size (obfd, osec, size);
  bfd_set_section_vma (obfd, osec, vaddr);
  bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
  return 0;
}

static int
objfile_find_memory_regions (int (*func) (CORE_ADDR, unsigned long,
					  int, int, int, void *),
			     void *obfd)
{
  /* Use objfile data to create memory sections.  */
  struct objfile *objfile;
  struct obj_section *objsec;
  bfd_vma temp_bottom, temp_top;

  /* Call callback function for each objfile section.  */
  ALL_OBJSECTIONS (objfile, objsec)
    {
      bfd *ibfd = objfile->obfd;
      asection *isec = objsec->the_bfd_section;
      flagword flags = bfd_get_section_flags (ibfd, isec);
      int ret;

      if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
	{
	  int size = bfd_section_size (ibfd, isec);
	  int ret;

	  ret = (*func) (obj_section_addr (objsec), bfd_section_size (ibfd, isec),
			 1, /* All sections will be readable.  */
			 (flags & SEC_READONLY) == 0, /* Writable.  */
			 (flags & SEC_CODE) != 0, /* Executable.  */
			 obfd);
	  if (ret != 0)
	    return ret;
	}
    }

  /* Make a stack segment.  */
  if (derive_stack_segment (&temp_bottom, &temp_top))
    (*func) (temp_bottom, temp_top - temp_bottom,
	     1, /* Stack section will be readable.  */
	     1, /* Stack section will be writable.  */
	     0, /* Stack section will not be executable.  */
	     obfd);

  /* Make a heap segment. */
  if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
    (*func) (temp_bottom, temp_top - temp_bottom,
	     1, /* Heap section will be readable.  */
	     1, /* Heap section will be writable.  */
	     0, /* Heap section will not be executable.  */
	     obfd);

  return 0;
}

static void
gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
{
  bfd_size_type size, total_size = bfd_section_size (obfd, osec);
  file_ptr offset = 0;
  struct cleanup *old_chain = NULL;
  void *memhunk;

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

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

  size = min (total_size, MAX_COPY_BYTES);
  memhunk = xmalloc (size);
  /* ??? This is crap since xmalloc should never return NULL.  */
  if (memhunk == NULL)
    error (_("Not enough memory to create corefile."));
  old_chain = make_cleanup (xfree, memhunk);

  while (total_size > 0)
    {
      if (size > total_size)
	size = total_size;

      if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
			      memhunk, size) != 0)
	{
	  warning (_("Memory read failed for corefile section, %s bytes at %s."),
		   plongest (size),
		   paddress (target_gdbarch, bfd_section_vma (obfd, osec)));
	  break;
	}
      if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
	{
	  warning (_("Failed to write corefile contents (%s)."),
		   bfd_errmsg (bfd_get_error ()));
	  break;
	}

      total_size -= size;
      offset += size;
    }

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

static int
gcore_memory_sections (bfd *obfd)
{
  if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
    return 0;			/* FIXME: error return/msg?  */

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

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

  return 1;
}

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

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

  add_com_alias ("gcore", "generate-core-file", class_files, 1);
  exec_set_find_memory_regions (objfile_find_memory_regions);
}