upx.pod

UPX 源代码

       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 file system 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 noticeable 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.



=head2 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: ~1.89 / ~7.60 Mbytes.

Notes:

  - UPX creates as default a suitable executable for CD-Mastering
    and console transfer. For a CD-Master main executable you could also try
    the special option "--boot-only" as described below.
    It has been reported that upx packed executables are fully compatible with
    the Sony PlayStation 2 (PS2, PStwo) and Sony PlayStation Portable (PSP) in
    Sony PlayStation (PSone) emulation mode.

  - 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 relocate the loading address
    for the packed file, but this isn't a real problem if it is a single or
    the main 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.

  --8-bit             Uses 8 bit size compression [default: 32 bit]

  --8mb-ram           PSone has 8 MB ram available [default: 2 MB]

  --boot-only         This format is for main exes and CD-Mastering only !
                      It may slightly improve the compression ratio,
                      decompression routines are faster than default ones.
                      But it cannot be used for console 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 console transfer only !



=head2 NOTES FOR RTM32/PE and ARM/PE

Same as win32/pe.



=head2 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.



=head2 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 B<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
  boot disks.

     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.



=head2 NOTES FOR WATCOM/LE

B<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.



=head2 NOTES FOR WIN32/PE

The PE support in B<UPX> is quite stable now, but probably there are
still some incompatibilities with some files.

Because of the way B<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 segments 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 have 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-icons=3  Compress all icons.

  --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.



=head1 DIAGNOSTICS

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

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



=head1 BUGS

Please report all bugs immediately to the authors.



=head1 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]>



=head1 COPYRIGHT

Copyright (C) 1996-2007 Markus Franz Xaver Johannes Oberhumer

Copyright (C) 1996-2007 Laszlo Molnar

Copyright (C) 2000-2007 John F. Reiser

Copyright (C) 2002-2007 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
B<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.