  The Linux ELF HOWTO
  Daniel Barlow <daniel.barlow@sjc.ox.ac.uk>
  v1.03, August 1995

  This document describes how to migrate your Linux system to compile
  and run programs in the ELF binary format.  It falls into three con-
  ceptual parts: (1) What ELF is, and why/whether you should upgrade,
  (2) How to upgrade to ELF-capability, and (3) what you can do then.

  1.  What is ELF?  An introduction

  ELF (Executable and Linking Format) is a binary format originally
  developed by USL (UNIX System Laboratories) and currently used in
  Solaris and System V Release 4.  Because of its increased flexibility
  over the older a.out format that Linux currently uses, the GCC and C
  library developers decided last year to move to using ELF as the Linux
  standard binary format also.

  This `increased flexibility' manifests as essentially two benefits to
  the average applications progammer:


  o  It is much simpler to make shared libraries with ELF.  Typically,
     just compile all the object files with -fPIC, then link with a
     command like



        gcc -shared -Wl,-soname,libfoo.so.y -o libfoo.so.y.x *.o





  Now that may look complex, but it's far simpler than the method for
  a.out shared libraries, which involves reserving space for all the
  data you think that the library is likely to require in future, and
  registering that address space with a third party (it's described in a
  document over 20 pages long --- look at
  <ftp://tsx-11.mit.edu/pub/linux/packages/GCC/src/tools-2.16.tar.gz>
  for details).

  o  It makes dynamic loading (ie programs which can load modules at
     runtime) much simpler.  This is used by Perl 5, Python, and the
     ongoing port of Java to Linux, among other things.  Other
     suggestions for dynamic loading have included super-fast MUDs,
     where extra code could be compiled and linked into the running
     executable without having to stop and restart the program.


  Against this it must be weighed that ELF is reputed to be possibly a
  bit slower.  The figures that get bandied around are between 2% and
  5%, though as far as I know nobody has done any proper testing.  If
  you do know of any comparative tests, please let me know too.

  The slowdown comes from the fact the ELF library code must be position
  independent (this is what the -fPIC above is for) and so a register
  must be devoted to holding offsets.  That's one less for holding
  variables in, and the 80x86 has a paucity of general-purpose registers
  anyway.


  1.1.  What ELF isn't

  There are a number of common misconceptions about what ELF will do for
  your system:
     It's not a way to run SVR4 or Solaris programs
        Although it's the same binary `container' as SVR4 systems use,
        that doesn't mean that SVR4 programs suddenly become runnable on
        Linux.  It's analogous to a disk format --- you can keep Linux
        programs on MSDOS or Minix-format disks, and vice versa, but
        that doesn't mean that these systems become able to run each
        others' programs.

        It is theoretically possible to run applications for other x86
        Unices under Linux, but following the instructions in this HOWTO
        will not have that effect.  Start by looking at the iBCS kernel
        module (somewhere on tsx-11.mit.edu) and see if it fits your
        needs.


     It's not intrinsically smaller or faster
        You may well end up with smaller binaries anyway, though, as you
        can more easily create shared libraries of common code between
        many programs.  In general, if you use the same compiler options
        and your binaries come out smaller than they did with a.out,
        it's more likely to be fluke or a different compiler version.
        As for `faster', I'd be surprised.  Speed increases could turn
        up if your binaries are smaller, due to less swapping or larger
        functional areas fitting in cache.


     It doesn't require that you replace every binary on your system
        At the end of this procedure you have a system capable of
        compiling and running both ELF and a.out programs.  New programs
        will by default be compiled in ELF, though this can be
        overridden with a command-line switch.  There is admittedly a
        memory penalty for running a mixed ELF/a.out system --- if you
        have both breeds of program running at once you also have two
        copies of the C library in core, and so on.  I've had reports
        that the speed difference from this is undetectable in normal
        use on a 6Mb system though (I certainly haven't noticed much in
        8Mb), so it's hardly pressing.  You lose far more memory every
        day by running bloated programs like Emacs and static
        Mosaic/Netscape binaries :-)


     It's nothing to do with Tolkien, Pratchett, Keebler, or general
        mythology" Or at least, not in this context.  'Nuff said.



  1.2.  Why you should(n't) convert to ELF

  There are essentially two reasons to upgrade your system to compile
  and run ELF programs: the first is the increased flexibility in
  programming referred to above, and the second is that, due to the
  first, everyone else will be too.  Future releases of the C library
  and GCC will only be compiled for ELF, and other developers are
  expected to move ELFwards too.

  Pleasingly for the purposes of symmetry, there are also two reasons
  not to convert at this time.  The first is that things are still
  changing, some packages (including the `stable' 1.2 kernel series)
  require patches to be made before they will compile in ELF, and there
  may be residual bugs; one could make a strong case for waiting until
  Linus himself has converted, for example.

  The second is that although the installation described here is a
  fairly small job in itself (it can be completed in well under an hour,
  excepting the time taken to download the new software), an error at
  almost any stage of it will probably leave you with an unbootable
  system.  If you are not comfortable with upgrading shared libraries
  and the commands ldconfig and ldd mean nothing to you, you may want to
  obtain or wait for a new Linux distribution in ELF, and backup,
  reinstall and selectively restore your system using it.  Then again
  (and especially if the system is not mission-critical) you may want to
  go through it anyway and look on it as a learning experience.

  Still with us?


  2.  Installation

  2.1.  Background

  The aim of this conversion is to leave you with a system which can
  build and run both a.out and ELF programs, with each type of program
  being able to find its appropriate breed of shared libraries.  This
  obviously requires a bit more intelligence in the library search
  strategy than the simple `look in /lib, /usr/lib and anywhere else
  that the program was compiled to search' strategy that some other
  systems can get away with.

  The beastie responsible for searching out libraries in linux is
  /lib/ld.so.  The compiler and linker do not encode absolute library
  pathnames into the programs they output; instead they put the library
  name and the absolute path to ld.so in, and leave ld.so to match the
  library name to the appropriate place at runtime.  This has one very
  important effect --- it means that the libraries that a program uses
  can be moved to other directories without recompiling the program,
  provided that ld.so is told to search the new directory.  This is
  essential for the directory swapping operation that follows.

  The corollary of the above, of course, is that any attempt to delete
  or move ld.so will cause every dynamically linked program on the
  system to stop working.  This is generally regarded as a Bad Thing.

  For ELF binaries, an alternate dynamic loader is provided.  This is
   /lib/ld-linux.so.1, and does exactly the same thing as ld.so, but for
  ELF programs.  ld-linux.so.1 uses the same support files and programs
  (ldd, ldconfig, and /etc/ld.so.conf) as the a.out loader ld.so does.

  The basic plan, then, is that ELF development things (compilers,
  include files and libraries) go into /usr/{bin,lib,include} where your
  a.out ones currently are, and the a.out things will be moved into
  /usr/i486-linuxaout/{bin, lib, include}.  /etc/ld.so.conf lists all
  the places on the system where libraries are expected to be found, and
  ldconfig is intelligent enough to distinguish between ELF and a.out
  variants.  There are a couple of exceptions to the library placement,
  though; see the Caveats section below.


  2.2.  Before you start --- Notes and Caveats


  o  You will need to be running a post-1.1.52 kernel with ELF binary
     format support.  Note that kernel versions 1.3.0 to 1.3.2 inclusive
     had an ELF-related bug.  If you're running the development 1.3
     kernel series, make sure you stay current!  1.3.3 is fine, as is
     1.2.10 (the latest stable kernel at time of writing).

  o  You are recommended to prepare or acquire a linux boot/root disk,
     such as a Slackware rescue disk.  You probably won't need it, but
     if you do and you don't have one, you'll kick yourself.  In a
     similar `prevention is better than cure' vein, statically linked
     copies of mv, ln, and maybe other file manipulation commands
     (though in fact I think you can do everything else you actually
     need to with shell builtins) may help you out of any awkward
     situations you could end up in.

  o  Extra care is needed if you have /usr or /usr/lib on a separate
     partition from /.  You will need to check the libraries that your
     programs in /bin and /sbin use, and put those libraries somewhere
     on the root partition, say in /lib-aout.  I'll come back to this at
     the appropriate spot.

  o  If you have been following the ELF development, you may have ELF
     libraries in /lib/elf (usually libc.so.4 and co).  Applications
     that you built using these should be rebuilt, then the directory
     removed.  There is no need for a /lib/elf directory!  It was used
     for a time during ELF development, but how it ended up as a
     standard directory in Slackware installs, who knows?

  o  Some old programs don't use ld.so, so any libraries that they
     depend on cannot be moved.  There may or may not be a problem here.
     Use ldd to determine which these libraries are.  If the program
     depends only on libc.so.4 and/or libm.so.4, there is no problem, as
     these libraries continue to reside in /lib.  If it depends on X in
     any way, shape, or form, you're also safe: to be old enough not to
     use ld.so it would have to have been compiled with a pretty old
     version of the X libraries, and both the major version number and
     directory placement of the X libraries has changed since then.

     If you do have a clash between an a.out library that cannot be
     moved and an ELF library with the same major version that wants to
     install over the top of it, you'll have to put the ELF library
     somewhere else and add the other directory to /etc/ld.so.conf.

     If your system is old enough that you still have shared libraries
     with dates in the filenames then you're obviously a Linux God(tm)
     and should be advising me on the appropriate course of action at
     this point :-)  Answers to the address in the title of this HOWTO.

  o  Most Linux installations these days have converged on the `FSSTND'
     standard file system, but doubtless there are still installed
     systems that haven't.  If you see references to /sbin/something and
     you don't have a /sbin directory, you'll probably find the program
     referred to in /bin or /etc/.


  2.3.  You will need ...

  The following packages are available from
  <ftp://tsx-11.mit.edu/pub/linux/packages/GCC/> and
  <ftp://sunsite.unc.edu/pub/Linux/GCC/>.  Both sites are widely
  mirrored; please take the time to look up your nearest mirror site and
  use that instead of the master sites where possible.  It's faster for
  both you and everyone else.

  These packages (either the listed version or a later one) are
  required.  Also download and read through the release notes for each
  of them: these are the files named release.packagename.  This applies
  especially if you get newer versions than are listed here, as
  procedures may have changed.


  o  ld.so-1.7.3.tar.gz --- the new dynamic linker

  o  libc-5.0.9.bin.tar.gz --- the ELF shared images for the C library
     and its friends (m (maths), termcap, gdbm, and so on), plus the
     corresponding static libraries and the include files needed to
     compile programs with them.

  o  gcc-2.7.0.bin.tar.gz --- the ELF C compiler.  Also includes an
     a.out C compiler which understands the new directory layout.

  o  binutils-2.5.2l.17.bin.tar.gz --- the GNU binary utilities patched
     for Linux.  These are programs such as gas, ld, strings and so on,
     most of which are required to make the C compiler go.  Note that
     you can also use binutils-2.5.2l.20.bin.tar.gz, if it's arrived in
     your part of the world.


  2.4.  Rearranging your filesystem

  Sooo...  Note that in all that follows, when I say `remove' I
  naturally mean `backup then remove' :-).  Also, these instructions
  directly apply only to people who haven't yet messed with ELF ---
  those who have are expected to have the necessary nous to adapt as
  appropriate.  Let's go!


  1. If you have separate / and /usr partitions, some caution is
     required here.  You must check each program that is run at startup
     before /usr is mounted, or run in other situations where /usr is
     unavailable, and put all the libraries required by it in /lib-aout.

     This is actually less tedious than it sounds.  Simply run



       $ ldd /sbin/* /bin/* /etc/* >/tmp/list.txt





  and then look through /tmp/list.txt , ignoring all the errors from
  non-executable files, and noting which libraries appear.  These are
  the libraries which you will need on the root partition.  Keep this
  list.

  2. Make the new directories that you will move a.out things to


       ______________________________________________________________________
       mkdir -p /usr/i486-linuxaout/bin
       mkdir -p /usr/i486-linuxaout/include
       mkdir -p /usr/i486-linuxaout/lib
       mkdir /lib-aout
       ______________________________________________________________________





  3. Untar the dynamic linker package ld.so-1.7.3 in the directory you
     usually put source code, then read through the
     ld.so-1.7.3/instldso.sh script just unpacked.  If you have a really
     standard system, run it by doing sh instldso.sh, but if you have
     anything at all unusual then do the install by hand instead.
     `Anything at all unusual' includes

  o  using zsh as a shell (some versions of zsh define $VERSION, which
     seems to confuse instldso.sh)

  o  having symlinks from /lib/elf to /lib (which you shouldn't need,
     but you may have valid reasons for if you have been following the
     ELF development)
     Edit /etc/ld.so.conf to add the new directory
     /usr/i486-linuxaout/lib (and /lib-aout if you're going to need
     one).  Then rerun /sbin/ldconfig -v to check that it is picking up
     the new directories.

  4. Move all your a.out libraries in /usr/*/lib to
     /usr/i486-linuxaout/lib.  If /usr is not on the root partition,
     refer now to the list you made of libraries that are needed in
     single-user mode, and move them from /lib to /lib-aout.  After
     doing that, or if you didn't need to do that, move all remaining
     libraries in /lib to /usr/i486-linuxaout/lib.  Don't move, delete
     or do anything with /lib/ld.so!

     For people with only the one partition, the following series of
     commands are pretty well what you need to do.



       ______________________________________________________________________
       cd /lib
       mv *.o *.a *.sa /usr/i486-linuxaout/lib
       mv libfoo.so* libbar.so* libmumble.so*  /usr/i486-linuxaout/lib
       cd /usr/lib
       mv *.o *.a *.so* *.sa /usr/i486-linuxaout/lib
       cd /usr/X11R6/lib
       mv *.o *.a *.so* *.sa /usr/i486-linuxaout/lib
       cd /usr/local/lib
       mv *.o *.a *.so* *.sa /usr/i486-linuxaout/lib
       ______________________________________________________________________






  If you actually typed in the third line of that without reading it
  first, you'll observe that it didn't do anything.  What you should be
  attempting to do there is move all files matching *.so* except for
  libc.so*, libm.so* and libdl.so* to /usr/i486-linuxaout/lib.  I can't
  advise more specifically than that as I don't know what libraries you
  have in /lib

  Do not pass this stage until you have removed all libraries and object
  (*.o) files from each of the above directories, except for libc.so*,
  libm.so* and libdl.so* in /lib, which you need to keep so that aged
  programs continue to work, and ld.so in /lib, which you still need for
  anything to work.  Now run ldconfig again.


  5. Remove the directory /usr/lib/ldscripts if it's there.

  6. Remove any copies of ld and as (except for ld86 and as86) that you
     can find in /usr/bin.

  7. Some versions of GNU tar appear to have problems dealing with
     symbolically linked files.  Before installing the libc images you
     might want to go through /usr/include and remove some parts.

     This is icky.  Many packages (such as ncurses) are installed into
     /usr/include by distribution maintainers and are not supplied with
     the C library.  Backup the /usr/include tree, use tar tzf to see
     what's in the file before untarring it, and delete the directories
     that it actually fills.  Then untar the libc-5.0.9.bin.tar.gz
     package from root.


  8. Install the binutils package.  tar -xvzf
     binutils-2.6.2.l17.bin.tar.gz -C /  is one perfectly good way to do
     this.

  9. You have now installed everything you need to run ELF executables.
     Medical experts recommend that VDU workers take regular breaks away
     from the screen; this would be an opportune moment.  Don't forget
     what you were doing, though; depending on the version of gcc you
     were previously using, you may have left yourself unable to compile
     programs in a.out until you unpack the new gcc.

  10.
     Backup and remove everything in /usr/lib/gcc-lib/{i486-linux,
     i486-linuxelf, i486-linuxaout}/ Then install the gcc package, again
     by untarring from root.

  11.
     Some programs (notably various X programs) use /lib/cpp, which
     under Linux is generally a link to /usr/lib/gcc-
     lib/i486-linux/version/cpp.  As the preceding step wiped out
     whatever version of cpp it was pointing to, you'll need to recreate
     the link:



       $ cd /lib
       $ ln -s /usr/lib/gcc-lib/i486-linux/2.7.0/cpp .





   Done!  Simple tests that you can try are



       ______________________________________________________________________
       $ gcc -v
       Reading specs from /usr/lib/gcc-lib/i486-linux/2.7.0/specs
       gcc version 2.7.0
       $ gcc -v -b i486-linuxaout
       Reading specs from /usr/lib/gcc-lib/i486-linuxaout/2.7.0/specs
       gcc version 2.7.0
       $ ld -V
       ld version cygnus/linux-2.5.2l.14 (with BFD cygnus/linux-2.5.2l.11)
         Supported emulations:
          elf_i386
          i386linux
          i386coff
       ______________________________________________________________________




  followed of course by the traditional ``Hello, world'' program.  Try
  it with gcc and with gcc -b i486-linuxaout to check that both the
  a.out and ELF compilers are set up corectly.


  2.5.  Common errors

  I'm soliciting reports of people's problems for this section.  Your
  anonymity will be preserved if you so request :-)



      no such file or directory: /usr/bin/gcc
        that the ELF dynamic loader /lib/ld-linux.so.1 is not installed,
        or is unreadable for some reason.  You should have installed it
        at around step 3 of the previous section.


      not a ZMAGIC file, skipping
        from ldconfig.  You have an old version of the ld.so package, so
        get a recent one.  Again, see step 3 of the previous section.


      bad address
        on attempting to run anything ELF.  You're using kernel 1.3.x,
        where x<3.  Upgrade to 1.3.3 or downgrade to 1.2.something


      _setutent: Can't open utmp file
        You didn't read the libc release notes.  In accordance with
        version 1.2 of the FSSTND, utmp and wtmp have moved again, and
        should now be located in /var/run and /var/log respectively.
        Recommended practice is to add symlinks from their old locations
        so that your older programs will also find them.  Don't forget
        to check your startup scripts (/etc/bcheckrc, for example) to
        make sure you're not deleting things you shouldn't at startup.


      gcc: installation problem, cannot exec something: No such file or
        directory
        when attempting to do a.out compilations (something is usually
        one of cpp or cc1).  Either it's right, or alternatively you
        typed



          $ gcc -b -i486-linuxaout




     when you should have typed



          $ gcc -b i486-linuxaout




     Note that the `i486' does not start with a dash.



  3.  Building programs in ELF

  3.1.  Ordinary programs

  To build a program in ELF, use gcc as always.  To build in a.out, use
  gcc -b i486-linuxaout .








  ______________________________________________________________________
  $ cat >hello.c
  main() { printf("hello, world\n"); }
  ^D
  $ gcc -o hello hello.c
  $ file hello
  hello: ELF 32-bit LSB executable i386 (386 and up) Version 1
  $ ./hello
  hello, world
  ______________________________________________________________________




  This is perhaps an appropriate time to answer the question ``if a.out
  compilers default to producing a program called a.out, what name does
  an ELF compiler give its output?''.  Still a.out, is the answer.
  Boring boring boring ...  :-)


  3.2.  Building libraries

  To build libfoo.so as a shared library, the basic steps look like
  this:



       ______________________________________________________________________
       $ gcc -fPIC -c *.c
       $ gcc -shared -Wl,-soname,libfoo.so.1 -o libfoo.so.1.0 *.o
       $ ln -s libfoo.so.1.0 libfoo.so.1
       $ ln -s libfoo.so.1 libfoo.so
       $ export LD_LIBRARY_PATH=`pwd`:$LD_LIBRARY_PATH
       ______________________________________________________________________




  This will generate a shared library called libfoo.so.1.0, and the
  appropriate links for ld (libfoo.so) and the dynamic linker
  (libfoo.so.1) to find it.  To test, we add the current directory to
  LD_LIBRARY_PATH.

  When you're happpy that the library works, you'll have to move it to,
  say, /usr/local/lib, and recreate the appropriate links.  Note that
  the libfoo.so link should point to libfoo.so.1, so it doesn't need
  updating on every minor version number change.  The link from
  libfoo.so.1 to libfoo.so.1.0 is kept up to date by ldconfig, which on
  most systems is run as part of the boot process.



       ______________________________________________________________________
       $ su
       # cp libfoo.so.1.0 /usr/local/lib
       # /sbin/ldconfig
       # ( cd /usr/local/lib ; ln -s libfoo.so.1 libfoo.so )
       ______________________________________________________________________








  3.3.  Programs with dynamic loading

  These are covered extensively in H J Lu's ELF programming document,
  and the dlopen(3) manual page, which can be found in the ld.so
  package.  Here's a nice simple example though: link it with -ldl



       ______________________________________________________________________
       #include <dlfcn.h>
       #include <stdio.h>

       main()
       {
         void *libc;
         void (*printf_call)();

         if(libc=dlopen("/lib/libc.so.5",RTLD_LAZY))
         {
           printf_call=dlsym(libc,"printf");
           (*printf_call)("hello, world\n");
         }

       }
       ______________________________________________________________________





  3.4.  Debugging

  Your existing copy of gdb will most likely work unchanged with ELF
  programs.  The new version in the GCC directory on tsx-11 is reported
  to be better at debugging programs that use dynamic loading and to
  understand ELF core dumps.

  At the time of writing, a patch to the kernel is necessary before ELF
  programs will generate core dumps anyway, so it's perhaps a little
  academic.


  4.  Patches and binaries

  At this point in the proceedings, you can, if you like, stop.  You
  have installed everything necessary to compile and run ELF programs.

  You may wish to rebuild some programs in ELF, either for purposes of
  `neatness' or to minimise memory usage.  For most end-user
  applications, this is pretty simple; some packages however do assume
  too much about the systems they run on, and may fail due to one or
  more of:

  o  Different underscore conventions in the assembler: in an a.out
     executable, external labels get _ prefixed to them; in an ELF
     executable, they don't.  This makes no difference until you start
     integrating hand-written assembler: all the labels of the form _foo
     must be translated to foo, or (if you want to be portable about it)
     to EXTERNAL(foo) where EXTERNAL is some macro which returns either
     its argument (if __ELF__ is defined) or _ concatenated with its
     argument if not.

  o  Differences in libc 5 from libc 4.  The interface to the locale
     support has changed, for one.


  o  The application or build process depends on knowledge of the binary
     format used --- emacs, for example, dumps its memory image to disk
     in executable format, so obviously needs to know what format your
     executables are in.

  o  The application consists of or includes shared libraries (X11 is
     the obvious example).  These will obviously need changes to
     accomodate the different method of shared library creation in ELF.

  Anyway, here are two lists: the first is of programs that needed
  changing for ELF where the changes have been made (ie that you will
  need new versions of to compile as ELF), and the second is of programs
  that still need third-party patches of some kind.


  4.1.  Upgrade:


  o  Dosemu.  Modulo the three or four cuurrent dosemu development trees
     (don't ask, just join the linux-msdos mailing list), dosemu runs
     with ELF.  You'll need to monkey with the Makefile.  Current
     versions of dosemu are available from
     <ftp://tsx-11.mit.edu/pub/linux/ALPHA/dosemu/>

  o  Emacs.  Emacs has a rather odd build procedure that involves
     running a minimal version of itself, loading in all the useful bits
     as lisp, then dumping its memory image back to disk as an
     executable file.  (FSF) Emacs 19.29 and XEmacs 19.12 (formerly
     Lucid Emacs) can both detect whether you are compiling as ELF and
     Do The Right Thing automatically.

  o  MAKEDEV.  In some incarnations, this utility removes existing
     entries for devices before recreating them.  This is Bad News if it
     happens to touch /dev/zero, as said device is necessary to the
     operation of all ELF programs.  See the util-linux package(q.v.)
     for a fixed version.

  o  perl 5.001.  Perl 5.001 plus the ``official unofficial'' patches a-
     e will compile unchanged on an ELF system, complete with dynamic
     loading.  The patches are available from ftp.metronet.com or
     ftp.wpi.edu

  o  The cal program in util-linux 2.2 doesn't work.  Upgrade to version
     2.4 <ftp://tsx-11.mit.edu/pub/linux/packages/utils> or later.

  o  XFree86.  XFree86 3.1.2 comes in both a.out and ELF formats.  ftp
     to ftp.xfree86.org, read the `too many users' message that you are
     almost guaranteed to get, and pick the closest mirror site network-
     wise to you.

     I confess to not having actually tried this yet.  At time of
     writing, it's only been out for one day ;-)


  4.2.  Patch


  o  e2fsutils.  The Utilities for the Second Extended File System need
     a patch from
     <ftp://ftp.ibp.fr/pub/linux/ELF/patches/e2fsprogs-0.5b.elf.diff.gz>
     to compile correctly as a shared library.  Remy Card says ``This is
     the ELF patch which will probably be included in the next release
     of e2fsck and co''

  o  file.  This works anyway, but can be improved:
     <http://sable.ox.ac.uk/~jo95004/patches/file.diff> adds support for
     identifying stripped and mixed-endian ELF binaries.

  o  The Kernel.  As from at least 1.3.8, the development 1.3 series
     have a make config option to build using ELF tools.  If you are
     using the 1.2 series, you have two options:


     1. Patch the Makefile slightly to use the a.out compiler.  Just
        change the CC and LD definitions to be



          ___________________________________________________________________
          LD      =ld -m i386linux
          CC      =gcc -b i486-linuxaout -D__KERNEL__ -I$(TOPDIR)/include
          ___________________________________________________________________





     Alternatively,

     2. Apply H J Lu's patch which allows compiling the kernel in ELF
        (and also adds the ability to do ELF core dumps).


     Let me reiterate that neither of these is necessary for the 1.3
     series.

  o  ps (procps-0.97) The psupdate program needs a patch to work if you
     have compiled the kernel as ELF.  It's available in
     <linux.nrao.edu:/pub/people/juphoff/procps>, both as a patch to
     vanilla 0.97 and as an entire tar-file.  A new version of procps is
     expected to be released soon with this patch in place, so if you
     can find procps 0.98 by the time you read this, this patch will
     probably be obsolete.

  o  SVGATextMode requires a single simple adjustment.  Cut out the diff
     below and apply it, or else make the patch by hand.



       ______________________________________________________________________
       --- SVGATextMode-0.7.orig/XFREE/os-support/assyntax.h   Sun Feb 26 18:58:15 1995
       +++ SVGATextMode-0.7/XFREE/os-support/assyntax.h        Thu Mar 30 07:52:03 1995
       @@ -211,7 +211,7 @@
        #endif /* ACK_ASSEMBLER */


       -#if (defined(SYSV) || defined(SVR4)) && !defined(ACK_ASSEMBLER)
       +#if (defined (__ELF__) || defined(SYSV) || defined(SVR4)) && !defined(ACK_ASSEMBLER)
        #define GLNAME(a)       a
        #else
        #define GLNAME(a)       CONCAT(_,a)
       ______________________________________________________________________






  5.  Further information



  o  The linux-gcc mailing list is really the best place to see what's
     happening, usually without even posting to it.  Remember, it's not
     Usenet, so keep the questions down unless you're actually
     developing.  For instructions on joining the mailing list, mail a
     message containing the word help to majordomo@vger.rutgers.edu

  o  There's a certain amount of information about what the linux-gcc
     list is doing at my ELF web page
     <http://sable.ox.ac.uk/~jo95004/elf.html>, when I remember to
     update it.  Archives of the list itself are at
     <http://homer.ncm.com/>.

  o  See also Bobby Shmit's ELF upgrade experience
     <http://www.intac.com/~cully/elf.html> web page.

  o  The GCC-FAQ <ftp://sunsite.unc.edu/pub/Linux/docs/faqs/GCC-
     FAQ.html> contains much general development information and some
     more technical ELF details.

  o  There's also documentation for the file format on tsx-11
     <ftp://tsx-11.mit.edu/pub/linux/packages/GCC/ELF.doc.tar.gz>.  This
     is probably of most use to people who want to understand, debug or
     rewrite programs that deal directly with binary objects.

  o  H J Lu's document ELF: From The Programmer's Perspective
     <ftp://tsx-11.mit.edu/pub/linux/packages/GCC/elf.latex.tar.gz>
     contains much useful and more detailed information on programming
     with ELF.  If you aren't LaTeX-capable, it is also available as
     PostScript.

  o  There is a manual page for dlopen(3) supplied with the ld.so
     package.


  6.  Legalese

  All trademarks used in this document are acknowledged as being owned
  by their respective owners.  (Spot the teeth-gritting irony there...)


  The right of Daniel Barlow to be identified as the author of this work
  has been asserted in accordance with sections 77 and 78 of the
  Copyright Designs and Patents Act 1988.  (Proof by assertion

  This document is copyright (C) 1995 Daniel Barlow
  <daniel.barlow@sjc.ox.ac.uk> It may be reproduced and distributed in
  whole or in part, in any medium physical or electronic, as long as
  this copyright notice is retained on all copies. Commercial
  redistribution is allowed and encouraged; however, the author would
  like to be notified of any such distributions.

  All translations, derivative works, or aggregate works incorporating
  any Linux HOWTO documents must be covered under this copyright notice.
  That is, you may not produce a derivative work from a HOWTO and impose
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  may be granted under certain conditions; please contact the Linux
  HOWTO coordinator at the address given below.

  In short, we wish to promote dissemination of this information through
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  If you have questions, please contact Greg Hankins, the Linux HOWTO
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  9989.
