Attachment #152799: Patch for 18.59: 05_all_bss-heap-gap.patch for bug #221281

2008-05-11  Ulrich Mueller  <ulm@gentoo.org>

	* emacs.c: Handle gap between end of BSS and heap, backported

	from Emacs 22. Original changes by Jan Djarv and Masatake YAMATO.

	This fixes dumping on Linux 2.6.25.

	(my_heap_start, heap_bss_diff, MAX_HEAP_BSS_DIFF): New variables

	and constant.

	(main): Calculate heap_bss_diff.  If we are dumping and the

	heap_bss_diff is greater than MAX_HEAP_BSS_DIFF, set PER_LINUX32

	and ADD_NO_RANDOMIZE and exec ourself again.

	* lastfile.c: (my_endbss, my_endbss_static) New variables.

	* s-linux.h (HAVE_PERSONALITY_LINUX32): Define.

#ifdef HAVE_PERSONALITY_LINUX32

#include <sys/personality.h>

#endif

/* The address where the heap starts (from the first sbrk (0) call).  */

static void *my_heap_start;

/* The gap between BSS end and heap start as far as we can tell.  */

static unsigned long heap_bss_diff;

/* If the gap between BSS end and heap start is larger than this we try to

   work around it, and if that fails, output a warning in dump-emacs.  */

#define MAX_HEAP_BSS_DIFF (1024*1024)

  extern char *sbrk ();

  if (!initialized)

    {

      extern char my_endbss[];

      extern char *my_endbss_static;

      if (my_heap_start == 0)

        my_heap_start = sbrk (0);

      heap_bss_diff = (char *)my_heap_start

	- (my_endbss > my_endbss_static ? my_endbss : my_endbss_static);

    }

#ifdef HAVE_PERSONALITY_LINUX32

  /* See if there is a gap between the end of BSS and the heap.

     In that case, set personality and exec ourself again.  */

  if (!initialized

      && strcmp (argv[argc-1], "dump") == 0

      && heap_bss_diff > MAX_HEAP_BSS_DIFF)

    {

      if (! getenv ("EMACS_HEAP_EXEC"))

	{

	  /* Set this so we only do this once.  */

	  putenv("EMACS_HEAP_EXEC=true");

	  /* A flag to turn off address randomization which is introduced

	   in linux kernel shipped with fedora core 4 */

#define ADD_NO_RANDOMIZE 0x0040000

	  personality (PER_LINUX32 | ADD_NO_RANDOMIZE);

#undef  ADD_NO_RANDOMIZE

	  execvp (argv[0], argv);

	  /* If the exec fails, try to dump anyway.  */

	  perror ("execvp");

	}

    }

#endif /* HAVE_PERSONALITY_LINUX32 */

/* Help unexec locate the end of the .bss area used by Emacs (which

   isn't always a separate section in NT executables).  */

char my_endbss[1];

/* The Alpha MSVC linker globally segregates all static and public bss

   data, so we must take both into account to determine the true extent

   of the bss area used by Emacs.  */

static char _my_endbss[1];

char * my_endbss_static = _my_endbss;

#define HAVE_PERSONALITY_LINUX32 /* personality LINUX32 can be set */