Re: Some OpenWrt port related problems

[Eli Zaretskii <eliz@gnu.org>]

> From: David Kuehling <dvdkhlng@gmx.de>
> Date: Sat, 01 Jan 2011 15:20:58 +0100
> Cc: rms@gnu.org, Emacs Dev <emacs-devel@gnu.org>
> 
>   Loading ediff-hook...
>   Finding pointers to doc strings...
>   Finding pointers to doc strings...done
>   emacs: Can't allocate buffer for /usr/bin/emacs
> 
> So it wants to pull a full copy of the emacs binary into memory?

It tries to mmap it, yes:

  old_file_size = stat_buf.st_size;
  old_base = mmap (NULL, old_file_size, PROT_READ | PROT_WRITE,
		   MAP_ANON | MAP_PRIVATE, mmap_fd, 0);
  if (old_base == MAP_FAILED)
    fatal ("Can't allocate buffer for %s\n", old_name, 0);

>   $ echo "1" > /proc/sys/vm/overcommit_memory
>   $ emacs -Q --batch --eval \
>      '(dump-emacs "./demacs" "/usr/bin/emacs")'
> 
>   [..]
>   Finding pointers to doc strings...
>   Finding pointers to doc strings...done
>   emacs: Program segment above .bss in /usr/bin/emacs
> 
> So what's that supposed to mean?

This message comes from this portion of unexelf.c:

   /* Fix up a new program header.  Extend the writable data segment so
      that the bss area is covered too. Find that segment by looking
      for a segment that ends just before the .bss area.  Make sure
      that no segments are above the new .data2.  Put a loop at the end
      to adjust the offset and address of any segment that is above
      data2, just in case we decide to allow this later.  */

   for (n = new_file_h->e_phnum - 1; n >= 0; n--)
     {
       /* Compute maximum of all requirements for alignment of section.  */
       ElfW(Word) alignment = (NEW_PROGRAM_H (n)).p_align;
       if ((OLD_SECTION_H (old_bss_index)).sh_addralign > alignment)
	 alignment = OLD_SECTION_H (old_bss_index).sh_addralign;

 #ifdef __sgi
	   /* According to r02kar@x4u2.desy.de (Karsten Kuenne)
	      and oliva@gnu.org (Alexandre Oliva), on IRIX 5.2, we
	      always get "Program segment above .bss" when dumping
	      when the executable doesn't have an sbss section.  */
       if (old_sbss_index != -1)
 #endif /* __sgi */
       if (NEW_PROGRAM_H (n).p_vaddr + NEW_PROGRAM_H (n).p_filesz
	   > (old_sbss_index == -1
	      ? old_bss_addr
	      : round_up (old_bss_addr, alignment)))
	   fatal ("Program segment above .bss in %s\n", old_name, 0);

I don't know enough about unexelf, nor about ELF in general, to tell
what this means or what to do about this, though.  Anyone?