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        3) try to delete the temporary file and start (execve)
           the uncompressed program in /tmp using /proc/<pid>/fd/X as
           attained by step 2)
        4) if that fails, fork off a subprocess to clean up and
           start the program in /tmp in the meantime

      The UPX stub is about 1700 bytes long, partly written in assembler
      and only uses kernel syscalls. It is not linked against any libc.

    Specific drawbacks:

      - You need additional free disk space for the uncompressed program
        in your /tmp directory. This program is deleted immediately after
        decompression, but you still need it for the full execution time
        of the program.

      - You must have /proc filesystem support as the stub wants to open
        /proc/<pid>/exe and needs /proc/<pid>/fd/X. This also means that you
        cannot compress programs that are used during the boot sequence
        before /proc is mounted.

      - Utilities like `top' will display numerical values in the process
        name field. This is because Linux computes the process name from
        the first argument of the last execve syscall (which is typically
        something like /proc/<pid>/fd/3).

      - Because of temporary decompression to disk the decompression speed
        is not as fast as with the other executable formats. Still, I can see
        no noticable delay when starting programs like my ~3 MB emacs (which
        is less than 1 MB when compressed :-).

    Extra options available for this executable format:

      --force-execve      Force the use of the generic linux/386 "execve"
                          format, i.e. do not try the linux/elf386 and
                          linux/sh386 formats.

  NOTES FOR PS1/EXE
    This is the executable format used by the Sony PlayStation (PSone), a
    Mips R3000 based gaming console which is popular since the late '90s.
    Support of this format is very similar to the Atari one, because of
    nostalgic feelings of one of the authors.

    Packed programs will be byte-identical to the original after
    uncompression, until further notice.

    Maximum uncompressed size: ~1998848 bytes.

    Notes:

      - UPX creates as default a 'CD-Rom only' PS1/PS2 compatible executable.
        For transfer between client/target use options below.

      - Normally the packed files use the same memory areas like the uncompressed
        versions, so they will not override other memory areas while unpacking.
        If this isn't possible UPX will abort showing a 'packed data overlap'
        error. With the "--force" option UPX will set a few 'bytes higher' loading
        offset for the packed file, but this isn't a real problem if it is a
        single or boot-only executable.

    Extra options available for this executable format:

      --all-methods       Compress the program several times, using all
                          available compression methods. This may improve
                          the compression ratio in some cases, but usually
                          the default method gives the best results anyway.

      --boot-only         The format will only run from a CD and may slightly
                          improves the compression ratio. The decompression
                          routines are faster than default ones.
                          But it cannot be used for host/client transfer !

      --no-align          This option disables CD mode 2 data sector format
                          alignment. May slightly improves the compression ratio,
                          but the compressed executable will not boot from a CD.
                          Use it for client/target transfer only !

  NOTES FOR RTM32/PE and ARM/PE
    Same as win32/pe.

  NOTES FOR TMT/ADAM
    This format is used by the TMT Pascal compiler - see http://www.tmt.com/
    .

    Extra options available for this executable format:

      --all-methods       Compress the program several times, using all
                          available compression methods. This may improve
                          the compression ratio in some cases, but usually
                          the default method gives the best results anyway.

      --all-filters       Compress the program several times, using all
                          available preprocessing filters. This may improve
                          the compression ratio in some cases, but usually
                          the default filter gives the best results anyway.

  NOTES FOR VMLINUZ/386
    The vmlinuz/386 and bvmlinuz/386 formats take a gzip-compressed bootable
    Linux kernel image ("vmlinuz", "zImage", "bzImage"), gzip-decompress it
    and re-compress it with the UPX compression method.

    vmlinuz/386 is completely unrelated to the other Linux executable
    formats, and it does not share any of their drawbacks.

    Notes:

      - Be sure that "vmlinuz/386" or "bvmlinuz/386" is displayed
      during compression - otherwise a wrong executable format
      may have been used, and the kernel won't boot.

    Benefits:

      - Better compression (but note that the kernel was already compressed,
      so the improvement is not as large as with other formats).
      Still, the bytes saved may be essential for special needs like
      bootdisks.

         For example, this is what I get for my 2.2.16 kernel:
            1589708  vmlinux
             641073  bzImage        [original]
             560755  bzImage.upx    [compressed by "upx -9"]

      - Much faster decompression at kernel boot time (but kernel
        decompression speed is not really an issue these days).

    Drawbacks:

      (none)

    Extra options available for this executable format:

      --all-methods       Compress the program several times, using all
                          available compression methods. This may improve
                          the compression ratio in some cases, but usually
                          the default method gives the best results anyway.

      --all-filters       Compress the program several times, using all
                          available preprocessing filters. This may improve
                          the compression ratio in some cases, but usually
                          the default filter gives the best results anyway.

  NOTES FOR WATCOM/LE
    UPX has been successfully tested with the following extenders: DOS4G,
    DOS4GW, PMODE/W, DOS32a, CauseWay. The WDOS/X extender is partly
    supported (for details see the file bugs BUGS).

    DLLs and the LX format are not supported.

    Extra options available for this executable format:

      --le                Produce an unbound LE output instead of
                          keeping the current stub.

  NOTES FOR WIN32/PE
    The PE support in UPX is quite stable now, but probably there are still
    some incompabilities with some files.

    Because of the way UPX (and other packers for this format) works, you
    can see increased memory usage of your compressed files because the
    whole program is loaded into memory at startup. If you start several
    instances of huge compressed programs you're wasting memory because the
    common segements of the program won't get shared across the instances.
    On the other hand if you're compressing only smaller programs, or
    running only one instance of larger programs, then this penalty is
    smaller, but it's still there.

    If you're running executables from network, then compressed programs
    will load faster, and require less bandwidth during execution.

    DLLs are supported. But UPX compressed DLLs can not share common data
    and code when they got used by multiple applications. So compressing
    msvcrt.dll is a waste of memory, but compressing the dll plugins of a
    particular application may be a better idea.

    Screensavers are supported, with the restriction that the filename must
    end with ".scr" (as screensavers are handled slightly different than
    normal exe files).

    UPX compressed PE files has some minor memory overhead (usually in the
    10 - 30 kbytes range) which can be seen by specifying the "-i" command
    line switch during compression.

    Extra options available for this executable format:

     --compress-exports=0 Don't compress the export section.
                          Use this if you plan to run the compressed
                          program under Wine.
     --compress-exports=1 Compress the export section. [DEFAULT]
                          Compression of the export section can improve the
                          compression ratio quite a bit but may not work
                          with all programs (like winword.exe).
                          UPX never compresses the export section of a DLL
                          regardless of this option.

      --compress-icons=0  Don't compress any icons.
      --compress-icons=1  Compress all but the first icon.
      --compress-icons=2  Compress all icons which are not in the
                          first icon directory. [DEFAULT]

      --compress-resources=0  Don't compress any resources at all.

      --keep-resource=list Don't compress resources specified by the list.
                          The members of the list are separated by commas.
                          A list member has the following format: I<type[/name]>.
                          I<Type> is the type of the resource. Standard types
                          must be specified as decimal numbers, user types can be
                          specified by decimal IDs or strings. I<Name> is the
                          identifier of the resource. It can be a decimal number
                          or a string. For example:

                          --keep-resource=2/MYBITMAP,5,6/12345

                          UPX won't compress the named bitmap resource "MYBITMAP",
                          it leaves every dialog (5) resource uncompressed, and
                          it won't touch the string table resource with identifier
                          12345.

      --force             Force compression even when there is an
                          unexpected value in a header field.
                          Use with care.

      --strip-relocs=0    Don't strip relocation records.
      --strip-relocs=1    Strip relocation records. [DEFAULT]
                          This option only works on executables with base
                          address greater or equal to 0x400000. Usually the
                          compressed files becomes smaller, but some files
                          may become larger. Note that the resulting file will
                          not work under Windows 3.x (Win32s).
                          UPX never strips relocations from a DLL
                          regardless of this option.

      --all-methods       Compress the program several times, using all
                          available compression methods. This may improve
                          the compression ratio in some cases, but usually
                          the default method gives the best results anyway.

      --all-filters       Compress the program several times, using all
                          available preprocessing filters. This may improve
                          the compression ratio in some cases, but usually
                          the default filter gives the best results anyway.

DIAGNOSTICS
    Exit status is normally 0; if an error occurs, exit status is 1. If a
    warning occurs, exit status is 2.

    UPX's diagnostics are intended to be self-explanatory.

BUGS
    Please report all bugs immediately to the authors.

AUTHORS
     Markus F.X.J. Oberhumer <[e-mail]>
     http://www.oberhumer.com

     Laszlo Molnar <[e-mail]>

     John F. Reiser <[e-mail]>

     Jens Medoch <[e-mail]>

COPYRIGHT
    Copyright (C) 1996-2006 Markus Franz Xaver Johannes Oberhumer

    Copyright (C) 1996-2006 Laszlo Molnar

    Copyright (C) 2000-2006 John F. Reiser

    Copyright (C) 2002-2006 Jens Medoch

    This program may be used freely, and you are welcome to redistribute it
    under certain conditions.

    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 UPX License
    Agreement for more details.

    You should have received a copy of the UPX License Agreement along with
    this program; see the file LICENSE. If not, visit the UPX home page.