UPX(the Ultimate Packer for eXecutables)是一个非常全面的可执行文件压缩软件，支持dos/exe、dos/com、dos/sys、djgpp2/coff、 watcom/le、win32/pe、rtm32/pe、tmt/adam、atari/tos、linux/i386等几乎所有平台上的可执行文件，具有极佳的压缩比，还可以对未压缩的文件和压缩完后进行比较。

features:
• excellent compression ratio: typically compresses better than WinZip/zip/gzip, use UPX to decrease the size of your distribution!
• very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000+.
• no memory overhead for your compressed executables because of in-place decompression.
• safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
• universal: UPX can pack a number of executable formats.
• portable: UPX is written in portable endian-neutral C++
• extendable: because of the class layout it's very easy to add new executable formats or new compression algorithms
• free: UPX is distributed with full source code under the GNU General Public License, and may be used freely even with commercial programs.

Changes in version 3.02 (16 Dec 2007):
* fix unmapping on arm-linux.elf
* fix error checking in mmap for i386-linux.elf [triggered by -fPIE]
* bug fixes

官网：http://upx.sourceforge.net

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