1 / 22

Crinkler

Crinkler. - compressing Windows 4k intros to EXE files. Aske Simon Christensen Rune L. H. Stubbe. Overview. Background Compression method Function import Header layout Demo Future plans. Why another one?. Most common method: CAB dropping Dropping is a mess We want EXE files!.

landry
Télécharger la présentation

Crinkler

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Crinkler - compressing Windows 4k intros to EXE files Aske Simon Christensen Rune L. H. Stubbe Assembly 2005, Helsinki, July 2005

  2. Overview • Background • Compression method • Function import • Header layout • Demo • Future plans Assembly 2005, Helsinki, July 2005

  3. Why another one? • Most common method: CAB dropping • Dropping is a mess • We want EXE files! EXE file EXE optimizer CAB compressor BAT inserter BAT file Assembly 2005, Helsinki, July 2005

  4. How is Crinkler different? • The normal build process: ASM files C/C++ files object / library files Compiler Assember Linker Cruncher EXE file Assembly 2005, Helsinki, July 2005

  5. How is Crinkler different? • The Crinkler way: ASM files C/C++ files object / library files Compiler Assember Crinkler EXE file Assembly 2005, Helsinki, July 2005

  6. Why another one? • Control over code and data placement • Choose base address • Optimize order for best compression • Separate code and data • Put in extra code • Import code • Code transformations Assembly 2005, Helsinki, July 2005

  7. Compression method • Context modelling + Much better compression ratio than LZX + Well suited for small amounts of data + Small decompression code (< 250 bytes) + Pays off even with the extra header - Extremely slow - Very memory-hungry Assembly 2005, Helsinki, July 2005

  8. Data compression basics • Take advantage of self-similarity • Find patterns and eliminate them • Dictionary compression • Statistical compression Assembly 2005, Helsinki, July 2005

  9. Dictionary compression • LZ77: Refer repetitions back to original • Reasonable compression ratio • Fast compression • Very fast decompression M M I I S S S S I I S S S S I I P P P P I I Assembly 2005, Helsinki, July 2005

  10. Statistical compression • Estimate probability distribution of each symbol based on earlier data • PPM: • Problem: local M I S S I S S I P P I Assembly 2005, Helsinki, July 2005

  11. Context modelling • Generalization of PPM • Look at combinations of recent symbols • A bit mask describes a model • Problem: Many masks to choose from M I S S I S S I P P I Assembly 2005, Helsinki, July 2005

  12. Implementation • Estimation for each single bit • Context is current byte + selection of last 8 • Estimate the best collection of masks • Estimate the best weights of the masks • Keep track of contexts in a hash table • Ignore hash collisions • Find hash table size with few collisions Assembly 2005, Helsinki, July 2005

  13. Function import • Import by name: Name of each function • The import table is a big part of an EXE file • Import by ordinal: Number instead of name • Much smaller but quite incompatible • Import by hash: Hash code of each function • Small and compatible • Not supported directly • Import by hashed ordinal range Assembly 2005, Helsinki, July 2005

  14. Header optimization DOS header PE offset DOS stub PE header Data directories Section header 544 bytes! Assembly 2005, Helsinki, July 2005

  15. Header optimization DOS header PE offset DOS stub PE header Data directories Section header Assembly 2005, Helsinki, July 2005

  16. Header optimization DOS header PE offset DOS stub PE header Data directories Section header Assembly 2005, Helsinki, July 2005

  17. Header optimization DOS header PE offset DOS stub PE header Data directories Section header Ignored Assembly 2005, Helsinki, July 2005

  18. Header optimization DOS header PE offset DOS stub PE header Data directories 196 bytes! Section header Ignored Assembly 2005, Helsinki, July 2005

  19. Header optimization DOS header PE offset DOS stub PE header Data directories 124 bytes + 18 hash codes! Section header Hash code Assembly 2005, Helsinki, July 2005

  20. Demo Assembly 2005, Helsinki, July 2005

  21. Future plans • Windows 2000 compatibility • Even better compression • Section reordering • Transformations • More feedback • 64k specialized version Assembly 2005, Helsinki, July 2005

  22. Thank you Questions? Comments? Suggestions? Assembly 2005, Helsinki, July 2005

More Related