1UPX(1) UPX(1)
2
6 upx - compress or expand executable files
7
9 upx [ command ] [ options ] filename...
10
12 The Ultimate Packer for eXecutables
13 Copyright (c) 1996-2022 Markus Oberhumer, Laszlo Molnar & John Reiser
14 https://upx.github.io
15 UPX is a portable, extendable, high-performance executable packer for
17 several different executable formats. It achieves an excellent
18 compression ratio and offers *very* fast decompression. Your
19 executables suffer no memory overhead or other drawbacks for most of
20 the formats supported, because of in-place decompression.
21
23 UPX comes with ABSOLUTELY NO WARRANTY; for details see the file
24 COPYING.
25 Please report all problems or suggestions to the authors. Thanks.
27
29 IMPORTANT NOTE: UPX inherits the security context of any files it
30 handles.
31 This means that packing, unpacking, or even testing or listing a file
33 requires the same security considerations as actually executing the
34 file.
35 Use UPX on trusted files only!
37
39 UPX is a versatile executable packer with the following features:
40 - secure: as UPX is documented Open Source since many years any relevant
42 Security/Antivirus software is able to peek inside UPX compressed
43 apps to verify them
44 - excellent compression ratio: typically compresses better than Zip,
46 use UPX to decrease the size of your distribution !
47 - very fast decompression: more than 500 MB/sec on any reasonably modern
49 machine
50 - no memory overhead for your compressed executables for most of the
52 supported formats because of in-place decompression
53 - safe: you can list, test and unpack your executables.
55 Also, a checksum of both the compressed and uncompressed file is
56 maintained internally.
57 - universal: UPX can pack a number of executable formats, including
59 Windows programs and DLLs, macOS apps and Linux executables
60 - portable: UPX is written in portable endian-neutral C++
62 - extendable: because of the class layout it's very easy to support
64 new executable formats or add new compression algorithms
65 - free: UPX is distributed with full source code under the GNU General
67 Public License v2+, with special exceptions granting the free usage
68 for commercial programs
69 You probably understand now why we call UPX the "ultimate" executable
71 packer.
72
74 Compress
75 This is the default operation, eg. upx yourfile.exe will compress the
76 file specified on the command line.
77 Decompress
79 All UPX supported file formats can be unpacked using the -d switch, eg.
80 upx -d yourfile.exe will uncompress the file you've just compressed.
81 Test
83 The -t command tests the integrity of the compressed and uncompressed
84 data, eg. upx -t yourfile.exe check whether your file can be safely
85 decompressed. Note, that this command doesn't check the whole file,
86 only the part that will be uncompressed during program execution. This
87 means that you should not use this command instead of a virus checker.
88 List
90 The -l command prints out some information about the compressed files
91 specified on the command line as parameters, eg upx -l yourfile.exe
92 shows the compressed / uncompressed size and the compression ratio of
93 yourfile.exe.
94
96 -q: be quiet, suppress warnings
97 -q -q (or -qq): be very quiet, suppress errors
99 -q -q -q (or -qqq): produce no output at all
101 --help: prints the help
103 --version: print the version of UPX
105 --exact: when compressing, require to be able to get a byte-identical
107 file after decompression with option -d. [NOTE: this is work in
108 progress and is not supported for all formats yet. If you do care, as a
109 workaround you can compress and then decompress your program a first
110 time - any further compress-decompress steps should then yield byte-
111 identical results as compared to the first decompressed version.]
112 -k: keep backup files
114 -o file: write output to file
116 [ ...more docs need to be written... - type `upx --help' for now ]
118
120 UPX offers ten different compression levels from -1 to -9, and --best.
121 The default compression level is -8 for files smaller than 512 KiB, and
122 -7 otherwise.
123 • Compression levels 1, 2 and 3 are pretty fast.
125 • Compression levels 4, 5 and 6 achieve a good time/ratio
127 performance.
128 • Compression levels 7, 8 and 9 favor compression ratio over speed.
130 • Compression level --best may take a long time.
132 Note that compression level --best can be somewhat slow for large
134 files, but you definitely should use it when releasing a final version
135 of your program.
136 Quick info for achieving the best compression ratio:
138 • Try upx --brute --no-lzma myfile.exe or even upx --ultra-brute
140 --no-lzma myfile.exe.
141 • The option --lzma enables LZMA compression, which compresses better
143 but is *significantly slower* at decompression. You probably do not
144 want to use it for large files.
145 (Note that --lzma is automatically enabled by --all-methods and
147 --brute, use --no-lzma to override.)
148 • Try if --overlay=strip works.
150 • For win32/pe programs there's --strip-relocs=0. See notes below.
152
154 Info: An "overlay" means auxiliary data attached after the logical end
155 of an executable, and it often contains application specific data (this
156 is a common practice to avoid an extra data file, though it would be
157 better to use resource sections).
158 UPX handles overlays like many other executable packers do: it simply
160 copies the overlay after the compressed image. This works with some
161 files, but doesn't work with others, depending on how an application
162 actually accesses this overlayed data.
163 --overlay=copy Copy any extra data attached to the file. [DEFAULT]
165 --overlay=strip Strip any overlay from the program instead of
167 copying it. Be warned, this may make the compressed
168 program crash or otherwise unusable.
169 --overlay=skip Refuse to compress any program which has an overlay.
171
173 The environment variable UPX can hold a set of default options for UPX.
174 These options are interpreted first and can be overwritten by explicit
175 command line parameters. For example:
176 for DOS/Windows: set UPX=-9 --compress-icons#0
178 for sh/ksh/zsh: UPX="-9 --compress-icons=0"; export UPX
179 for csh/tcsh: setenv UPX "-9 --compress-icons=0"
180 Under DOS/Windows you must use '#' instead of '=' when setting the
182 environment variable because of a COMMAND.COM limitation.
183 Not all of the options are valid in the environment variable - UPX will
185 tell you.
186 You can explicitly use the --no-env option to ignore the environment
188 variable.
189
191 NOTES FOR ATARI/TOS
192 This is the executable format used by the Atari ST/TT, a Motorola 68000
193 based personal computer which was popular in the late '80s. Support of
194 this format is only because of nostalgic feelings of one of the authors
195 and serves no practical purpose :-). See https://freemint.github.io
196 for more info.
197 Packed programs will be byte-identical to the original after
199 uncompression. All debug information will be stripped, though.
200 Extra options available for this executable format:
202 --all-methods Compress the program several times, using all
204 available compression methods. This may improve
205 the compression ratio in some cases, but usually
206 the default method gives the best results anyway.
207 NOTES FOR BVMLINUZ/I386
209 Same as vmlinuz/i386.
210 NOTES FOR DOS/COM
212 Obviously UPX won't work with executables that want to read data from
213 themselves (like some commandline utilities that ship with
214 Win95/98/ME).
215 Compressed programs only work on a 286+.
217 Packed programs will be byte-identical to the original after
219 uncompression.
220 Maximum uncompressed size: ~65100 bytes.
222 Extra options available for this executable format:
224 --8086 Create an executable that works on any 8086 CPU.
226 --all-methods Compress the program several times, using all
228 available compression methods. This may improve
229 the compression ratio in some cases, but usually
230 the default method gives the best results anyway.
231 --all-filters Compress the program several times, using all
233 available preprocessing filters. This may improve
234 the compression ratio in some cases, but usually
235 the default filter gives the best results anyway.
236 NOTES FOR DOS/EXE
238 dos/exe stands for all "normal" 16-bit DOS executables.
239 Obviously UPX won't work with executables that want to read data from
241 themselves (like some command line utilities that ship with
242 Win95/98/ME).
243 Compressed programs only work on a 286+.
245 Extra options available for this executable format:
247 --8086 Create an executable that works on any 8086 CPU.
249 --no-reloc Use no relocation records in the exe header.
251 --all-methods Compress the program several times, using all
253 available compression methods. This may improve
254 the compression ratio in some cases, but usually
255 the default method gives the best results anyway.
256 NOTES FOR DOS/SYS
258 Compressed programs only work on a 286+.
259 Packed programs will be byte-identical to the original after
261 uncompression.
262 Maximum uncompressed size: ~65350 bytes.
264 Extra options available for this executable format:
266 --8086 Create an executable that works on any 8086 CPU.
268 --all-methods Compress the program several times, using all
270 available compression methods. This may improve
271 the compression ratio in some cases, but usually
272 the default method gives the best results anyway.
273 --all-filters Compress the program several times, using all
275 available preprocessing filters. This may improve
276 the compression ratio in some cases, but usually
277 the default filter gives the best results anyway.
278 NOTES FOR DJGPP2/COFF
280 First of all, it is recommended to use UPX *instead* of strip. strip
281 has the very bad habit of replacing your stub with its own (outdated)
282 version. Additionally UPX corrects a bug/feature in strip v2.8.x: it
283 will fix the 4 KiB alignment of the stub.
284 UPX includes the full functionality of stubify. This means it will
286 automatically stubify your COFF files. Use the option --coff to disable
287 this functionality (see below).
288 UPX automatically handles Allegro packfiles.
290 The DLM format (a rather exotic shared library extension) is not
292 supported.
293 Packed programs will be byte-identical to the original after
295 uncompression. All debug information and trailing garbage will be
296 stripped, though.
297 Extra options available for this executable format:
299 --coff Produce COFF output instead of EXE. By default
301 UPX keeps your current stub.
302 --all-methods Compress the program several times, using all
304 available compression methods. This may improve
305 the compression ratio in some cases, but usually
306 the default method gives the best results anyway.
307 --all-filters Compress the program several times, using all
309 available preprocessing filters. This may improve
310 the compression ratio in some cases, but usually
311 the default filter gives the best results anyway.
312 NOTES FOR LINUX [general]
314 Introduction
315 Linux/386 support in UPX consists of 3 different executable formats,
317 one optimized for ELF executables ("linux/elf386"), one optimized
318 for shell scripts ("linux/sh386"), and one generic format
319 ("linux/386").
320 We will start with a general discussion first, but please
322 also read the relevant docs for each of the individual formats.
323 Also, there is special support for bootable kernels - see the
325 description of the vmlinuz/386 format.
326 General user's overview
328 Running a compressed executable program trades less space on a
330 ``permanent'' storage medium (such as a hard disk, floppy disk,
331 CD-ROM, flash memory, EPROM, etc.) for more space in one or more
332 ``temporary'' storage media (such as RAM, swap space, /tmp, etc.).
333 Running a compressed executable also requires some additional CPU
334 cycles to generate the compressed executable in the first place,
335 and to decompress it at each invocation.
336 How much space is traded? It depends on the executable, but many
338 programs save 30% to 50% of permanent disk space. How much CPU
339 overhead is there? Again, it depends on the executable, but
340 decompression speed generally is at least many megabytes per second,
341 and frequently is limited by the speed of the underlying disk
342 or network I/O.
343 Depending on the statistics of usage and access, and the relative
345 speeds of CPU, RAM, swap space, /tmp, and file system storage, then
346 invoking and running a compressed executable can be faster than
347 directly running the corresponding uncompressed program.
348 The operating system might perform fewer expensive I/O operations
349 to invoke the compressed program. Paging to or from swap space
350 or /tmp might be faster than paging from the general file system.
351 ``Medium-sized'' programs which access about 1/3 to 1/2 of their
352 stored program bytes can do particularly well with compression.
353 Small programs tend not to benefit as much because the absolute
354 savings is less. Big programs tend not to benefit proportionally
355 because each invocation may use only a small fraction of the program,
356 yet UPX decompresses the entire program before invoking it.
357 But in environments where disk or flash memory storage is limited,
358 then compression may win anyway.
359 Currently, executables compressed by UPX do not share RAM at runtime
361 in the way that executables mapped from a file system do. As a
362 result, if the same program is run simultaneously by more than one
363 process, then using the compressed version will require more RAM and/or
364 swap space. So, shell programs (bash, csh, etc.) and ``make''
365 might not be good candidates for compression.
366 UPX recognizes three executable formats for Linux: Linux/elf386,
368 Linux/sh386, and Linux/386. Linux/386 is the most generic format;
369 it accommodates any file that can be executed. At runtime, the UPX
370 decompression stub re-creates in /tmp a copy of the original file,
371 and then the copy is (re-)executed with the same arguments.
372 ELF binary executables prefer the Linux/elf386 format by default,
373 because UPX decompresses them directly into RAM, uses only one
374 exec, does not use space in /tmp, and does not use /proc.
375 Shell scripts where the underlying shell accepts a ``-c'' argument
376 can use the Linux/sh386 format. UPX decompresses the shell script
377 into low memory, then maps the shell and passes the entire text of the
378 script as an argument with a leading ``-c''.
379 General benefits:
381 - UPX can compress all executables, be it AOUT, ELF, libc4, libc5,
383 libc6, Shell/Perl/Python/... scripts, standalone Java .class
384 binaries, or whatever...
385 All scripts and programs will work just as before.
386 - Compressed programs are completely self-contained. No need for
388 any external program.
389 - UPX keeps your original program untouched. This means that
391 after decompression you will have a byte-identical version,
392 and you can use UPX as a file compressor just like gzip.
393 [ Note that UPX maintains a checksum of the file internally,
394 so it is indeed a reliable alternative. ]
395 - As the stub only uses syscalls and isn't linked against libc it
397 should run under any Linux configuration that can run ELF
398 binaries.
399 - For the same reason compressed executables should run under
401 FreeBSD and other systems which can run Linux binaries.
402 [ Please send feedback on this topic ]
403 General drawbacks:
405 - It is not advisable to compress programs which usually have many
407 instances running (like `sh' or `make') because the common segments of
408 compressed programs won't be shared any longer between different
409 processes.
410 - `ldd' and `size' won't show anything useful because all they
412 see is the statically linked stub. Since version 0.82 the section
413 headers are stripped from the UPX stub and `size' doesn't even
414 recognize the file format. The file patches/patch-elfcode.h has a
415 patch to fix this bug in `size' and other programs which use GNU BFD.
416 General notes:
418 - As UPX leaves your original program untouched it is advantageous
420 to strip it before compression.
421 - If you compress a script you will lose platform independence -
423 this could be a problem if you are using NFS mounted disks.
424 - Compression of suid, guid and sticky-bit programs is rejected
426 because of possible security implications.
427 - For the same reason there is no sense in making any compressed
429 program suid.
430 - Obviously UPX won't work with executables that want to read data
432 from themselves. E.g., this might be a problem for Perl scripts
433 which access their __DATA__ lines.
434 - In case of internal errors the stub will abort with exitcode 127.
436 Typical reasons for this to happen are that the program has somehow
437 been modified after compression.
438 Running `strace -o strace.log compressed_file' will tell you more.
439 NOTES FOR LINUX/ELF386
441 Please read the general Linux description first.
442 The linux/elf386 format decompresses directly into RAM, uses only one
444 exec, does not use space in /tmp, and does not use /proc.
445 Linux/elf386 is automatically selected for Linux ELF executables.
447 Packed programs will be byte-identical to the original after
449 uncompression.
450 How it works:
452 For ELF executables, UPX decompresses directly to memory, simulating
454 the mapping that the operating system kernel uses during exec(),
455 including the PT_INTERP program interpreter (if any).
456 The brk() is set by a special PT_LOAD segment in the compressed
457 executable itself. UPX then wipes the stack clean except for
458 arguments, environment variables, and Elf_auxv entries (this is
459 required by bugs in the startup code of /lib/ld-linux.so as of
460 May 2000), and transfers control to the program interpreter or
461 the e_entry address of the original executable.
462 The UPX stub is about 1700 bytes long, partly written in assembler
464 and only uses kernel syscalls. It is not linked against any libc.
465 Specific drawbacks:
467 - For linux/elf386 and linux/sh386 formats, you will be relying on
469 RAM and swap space to hold all of the decompressed program during
470 the lifetime of the process. If you already use most of your swap
471 space, then you may run out. A system that is "out of memory"
472 can become fragile. Many programs do not react gracefully when
473 malloc() returns 0. With newer Linux kernels, the kernel
474 may decide to kill some processes to regain memory, and you
475 may not like the kernel's choice of which to kill. Running
476 /usr/bin/top is one way to check on the usage of swap space.
477 Extra options available for this executable format:
479 (none)
481 NOTES FOR LINUX/SH386
483 Please read the general Linux description first.
484 Shell scripts where the underling shell accepts a ``-c'' argument can
486 use the Linux/sh386 format. UPX decompresses the shell script into low
487 memory, then maps the shell and passes the entire text of the script as
488 an argument with a leading ``-c''. It does not use space in /tmp, and
489 does not use /proc.
490 Linux/sh386 is automatically selected for shell scripts that use a
492 known shell.
493 Packed programs will be byte-identical to the original after
495 uncompression.
496 How it works:
498 For shell script executables (files beginning with "#!/" or "#! /")
500 where the shell is known to accept "-c <command>", UPX decompresses
501 the file into low memory, then maps the shell (and its PT_INTERP),
502 and passes control to the shell with the entire decompressed file
503 as the argument after "-c". Known shells are sh, ash, bash, bsh, csh,
504 ksh, tcsh, pdksh. Restriction: UPX cannot use this method
505 for shell scripts which use the one optional string argument after
506 the shell name in the script (example: "#! /bin/sh option3\n".)
507 The UPX stub is about 1700 bytes long, partly written in assembler
509 and only uses kernel syscalls. It is not linked against any libc.
510 Specific drawbacks:
512 - For linux/elf386 and linux/sh386 formats, you will be relying on
514 RAM and swap space to hold all of the decompressed program during
515 the lifetime of the process. If you already use most of your swap
516 space, then you may run out. A system that is "out of memory"
517 can become fragile. Many programs do not react gracefully when
518 malloc() returns 0. With newer Linux kernels, the kernel
519 may decide to kill some processes to regain memory, and you
520 may not like the kernel's choice of which to kill. Running
521 /usr/bin/top is one way to check on the usage of swap space.
522 Extra options available for this executable format:
524 (none)
526 NOTES FOR LINUX/386
528 Please read the general Linux description first.
529 The generic linux/386 format decompresses to /tmp and needs /proc file
531 system support. It starts the decompressed program via the execve()
532 syscall.
533 Linux/386 is only selected if the specialized linux/elf386 and
535 linux/sh386 won't recognize a file.
536 Packed programs will be byte-identical to the original after
538 uncompression.
539 How it works:
541 For files which are not ELF and not a script for a known "-c" shell,
543 UPX uses kernel execve(), which first requires decompressing to a
544 temporary file in the file system. Interestingly -
545 because of the good memory management of the Linux kernel - this
546 often does not introduce a noticeable delay, and in fact there
547 will be no disk access at all if you have enough free memory as
548 the entire process takes places within the file system buffers.
549 A compressed executable consists of the UPX stub and an overlay
551 which contains the original program in a compressed form.
552 The UPX stub is a statically linked ELF executable and does
554 the following at program startup:
555 1) decompress the overlay to a temporary location in /tmp
557 2) open the temporary file for reading
558 3) try to delete the temporary file and start (execve)
559 the uncompressed program in /tmp using /proc/<pid>/fd/X as
560 attained by step 2)
561 4) if that fails, fork off a subprocess to clean up and
562 start the program in /tmp in the meantime
563 The UPX stub is about 1700 bytes long, partly written in assembler
565 and only uses kernel syscalls. It is not linked against any libc.
566 Specific drawbacks:
568 - You need additional free disk space for the uncompressed program
570 in your /tmp directory. This program is deleted immediately after
571 decompression, but you still need it for the full execution time
572 of the program.
573 - You must have /proc file system support as the stub wants to open
575 /proc/<pid>/exe and needs /proc/<pid>/fd/X. This also means that you
576 cannot compress programs that are used during the boot sequence
577 before /proc is mounted.
578 - Utilities like `top' will display numerical values in the process
580 name field. This is because Linux computes the process name from
581 the first argument of the last execve syscall (which is typically
582 something like /proc/<pid>/fd/3).
583 - Because of temporary decompression to disk the decompression speed
585 is not as fast as with the other executable formats. Still, I can see
586 no noticeable delay when starting programs like my ~3 MiB emacs (which
587 is less than 1 MiB when compressed :-).
588 Extra options available for this executable format:
590 --force-execve Force the use of the generic linux/386 "execve"
592 format, i.e. do not try the linux/elf386 and
593 linux/sh386 formats.
594 NOTES FOR PS1/EXE
596 This is the executable format used by the Sony PlayStation (PSone), a
597 MIPS R3000 based gaming console which is popular since the late '90s.
598 Support of this format is very similar to the Atari one, because of
599 nostalgic feelings of one of the authors.
600 Packed programs will be byte-identical to the original after
602 uncompression, until further notice.
603 Maximum uncompressed size: ~1.89 / ~7.60 MiB.
605 Notes:
607 - UPX creates as default a suitable executable for CD-Mastering
609 and console transfer. For a CD-Master main executable you could also try
610 the special option "--boot-only" as described below.
611 It has been reported that upx packed executables are fully compatible with
612 the Sony PlayStation 2 (PS2, PStwo) and Sony PlayStation Portable (PSP) in
613 Sony PlayStation (PSone) emulation mode.
614 - Normally the packed files use the same memory areas like the uncompressed
616 versions, so they will not override other memory areas while unpacking.
617 If this isn't possible UPX will abort showing a 'packed data overlap'
618 error. With the "--force" option UPX will relocate the loading address
619 for the packed file, but this isn't a real problem if it is a single or
620 the main executable.
621 Extra options available for this executable format:
623 --all-methods Compress the program several times, using all
625 available compression methods. This may improve
626 the compression ratio in some cases, but usually
627 the default method gives the best results anyway.
628 --8-bit Uses 8 bit size compression [default: 32 bit]
630 --8mib-ram PSone has 8 MiB ram available [default: 2 MiB]
632 --boot-only This format is for main exes and CD-Mastering only !
634 It may slightly improve the compression ratio,
635 decompression routines are faster than default ones.
636 But it cannot be used for console transfer !
637 --no-align This option disables CD mode 2 data sector format
639 alignment. May slightly improves the compression ratio,
640 but the compressed executable will not boot from a CD.
641 Use it for console transfer only !
642 NOTES FOR RTM32/PE and ARM/PE
644 Same as win32/pe.
645 NOTES FOR TMT/ADAM
647 This format is used by the TMT Pascal compiler - see
648 http://www.tmt.com/ .
649 Extra options available for this executable format:
651 --all-methods Compress the program several times, using all
653 available compression methods. This may improve
654 the compression ratio in some cases, but usually
655 the default method gives the best results anyway.
656 --all-filters Compress the program several times, using all
658 available preprocessing filters. This may improve
659 the compression ratio in some cases, but usually
660 the default filter gives the best results anyway.
661 NOTES FOR VMLINUZ/386
663 The vmlinuz/386 and bvmlinuz/386 formats take a gzip-compressed
664 bootable Linux kernel image ("vmlinuz", "zImage", "bzImage"), gzip-
665 decompress it and re-compress it with the UPX compression method.
666 vmlinuz/386 is completely unrelated to the other Linux executable
668 formats, and it does not share any of their drawbacks.
669 Notes:
671 - Be sure that "vmlinuz/386" or "bvmlinuz/386" is displayed
673 during compression - otherwise a wrong executable format
674 may have been used, and the kernel won't boot.
675 Benefits:
677 - Better compression (but note that the kernel was already compressed,
679 so the improvement is not as large as with other formats).
680 Still, the bytes saved may be essential for special needs like
681 boot disks.
682 For example, this is what I get for my 2.2.16 kernel:
684 1589708 vmlinux
685 641073 bzImage [original]
686 560755 bzImage.upx [compressed by "upx -9"]
687 - Much faster decompression at kernel boot time (but kernel
689 decompression speed is not really an issue these days).
690 Drawbacks:
692 (none)
694 Extra options available for this executable format:
696 --all-methods Compress the program several times, using all
698 available compression methods. This may improve
699 the compression ratio in some cases, but usually
700 the default method gives the best results anyway.
701 --all-filters Compress the program several times, using all
703 available preprocessing filters. This may improve
704 the compression ratio in some cases, but usually
705 the default filter gives the best results anyway.
706 NOTES FOR WATCOM/LE
708 UPX has been successfully tested with the following extenders:
709 DOS4G, DOS4GW, PMODE/W, DOS32a, CauseWay.
710 The WDOS/X extender is partly supported (for details
711 see the file bugs BUGS).
712 DLLs and the LX format are not supported.
714 Extra options available for this executable format:
716 --le Produce an unbound LE output instead of
718 keeping the current stub.
719 NOTES FOR WIN32/PE
721 The PE support in UPX is quite stable now, but probably there are still
722 some incompatibilities with some files.
723 Because of the way UPX (and other packers for this format) works, you
725 can see increased memory usage of your compressed files because the
726 whole program is loaded into memory at startup. If you start several
727 instances of huge compressed programs you're wasting memory because the
728 common segments of the program won't get shared across the instances.
729 On the other hand if you're compressing only smaller programs, or
730 running only one instance of larger programs, then this penalty is
731 smaller, but it's still there.
732 If you're running executables from network, then compressed programs
734 will load faster, and require less bandwidth during execution.
735 DLLs are supported. But UPX compressed DLLs can not share common data
737 and code when they got used by multiple applications. So compressing
738 msvcrt.dll is a waste of memory, but compressing the dll plugins of a
739 particular application may be a better idea.
740 Screensavers are supported, with the restriction that the filename must
742 end with ".scr" (as screensavers are handled slightly different than
743 normal exe files).
744 UPX compressed PE files have some minor memory overhead (usually in the
746 10 - 30 KiB range) which can be seen by specifying the "-i" command
747 line switch during compression.
748 Extra options available for this executable format:
750 --compress-exports=0 Don't compress the export section.
752 Use this if you plan to run the compressed
753 program under Wine.
754 --compress-exports=1 Compress the export section. [DEFAULT]
755 Compression of the export section can improve the
756 compression ratio quite a bit but may not work
757 with all programs (like winword.exe).
758 UPX never compresses the export section of a DLL
759 regardless of this option.
760 --compress-icons=0 Don't compress any icons.
762 --compress-icons=1 Compress all but the first icon.
763 --compress-icons=2 Compress all icons which are not in the
764 first icon directory. [DEFAULT]
765 --compress-icons=3 Compress all icons.
766 --compress-resources=0 Don't compress any resources at all.
768 --keep-resource=list Don't compress resources specified by the list.
770 The members of the list are separated by commas.
771 A list member has the following format: I<type[/name]>.
772 I<Type> is the type of the resource. Standard types
773 must be specified as decimal numbers, user types can be
774 specified by decimal IDs or strings. I<Name> is the
775 identifier of the resource. It can be a decimal number
776 or a string. For example:
777 --keep-resource=2/MYBITMAP,5,6/12345
779 UPX won't compress the named bitmap resource "MYBITMAP",
781 it leaves every dialog (5) resource uncompressed, and
782 it won't touch the string table resource with identifier
783 12345.
784 --force Force compression even when there is an
786 unexpected value in a header field.
787 Use with care.
788 --strip-relocs=0 Don't strip relocation records.
790 --strip-relocs=1 Strip relocation records. [DEFAULT]
791 This option only works on executables with base
792 address greater or equal to 0x400000. Usually the
793 compressed files becomes smaller, but some files
794 may become larger. Note that the resulting file will
795 not work under Windows 3.x (Win32s).
796 UPX never strips relocations from a DLL
797 regardless of this option.
798 --all-methods Compress the program several times, using all
800 available compression methods. This may improve
801 the compression ratio in some cases, but usually
802 the default method gives the best results anyway.
803 --all-filters Compress the program several times, using all
805 available preprocessing filters. This may improve
806 the compression ratio in some cases, but usually
807 the default filter gives the best results anyway.
808
810 Exit status is normally 0; if an error occurs, exit status is 1. If a
811 warning occurs, exit status is 2.
812 UPX's diagnostics are intended to be self-explanatory.
814
816 Please report all bugs immediately to the authors.
817
819 Markus F.X.J. Oberhumer <markus@oberhumer.com>
820 http://www.oberhumer.com
821 Laszlo Molnar <ezerotven+github@gmail.com>
823 John F. Reiser <jreiser@BitWagon.com>
825 Jens Medoch <jssg@users.sourceforge.net>
827
829 Copyright (C) 1996-2022 Markus Franz Xaver Johannes Oberhumer
830 Copyright (C) 1996-2022 Laszlo Molnar
832 Copyright (C) 2000-2022 John F. Reiser
834 Copyright (C) 2002-2022 Jens Medoch
836 UPX is distributed with full source code under the terms of the GNU
838 General Public License v2+; either under the pure GPLv2+ (see the file
839 COPYING), or (at your option) under the GPLv+2 with special exceptions
840 and restrictions granting the free usage for all binaries including
841 commercial programs (see the file LICENSE).
842 This program is distributed in the hope that it will be useful, but
844 WITHOUT ANY WARRANTY; without even the implied warranty of
845 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
846 You should have received a copy of the UPX License Agreements along
848 with this program; see the files COPYING and LICENSE. If not, visit the
849 UPX home page.
850upx 4.0.1 2022-11-16 UPX(1)