jslinux/readme.md

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2011-12-21 13:37:53 +08:00
Fabrix - (De-obfuscated) JSLinux
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I wanted to understand how the amazing [JsLinux][1] worked. However, Mr Bellard seems to have applied a decidedly french proclivity towards obfuscatory algorithmic prose, replete with two-letter variable names and the like... ;) I have no idea if he passed it through a minifier or if the code was generated algorithmically from stuff in the QEMU codebase. In any case, it's hard to follow the action as presented originally, let alone extend it to do new tricks.
2011-12-21 12:33:08 +08:00
So in order to better understand the code, I started transforming all the symbols and commenting it up, which isn't all that hard a thing to do given that it's been built to imitate a very well-specified piece of hardware.
2011-12-21 13:37:53 +08:00
In the tiny off-chance someone else might be interested I'm posting this "cheat sheet" version of the code here.
### Status
It's still absolutely ungainly, but not nearly so ungainly as the original. About a third to a half of the variables/function names have been redescribed. The names are basically long comments and will ultimately need to be redone once the whole is understood.
2011-12-22 13:04:09 +08:00
The core opcode execution loop has been autocommented to indicate what instruction operation the opcode refers to.
I highly recommend, by the way, the excellent [JSShaper][2] library for transforming large javascript code bases. The hacks I made from it are in this repo: a little symbol-name-transformer node.js script and an emacs function for doing this in live buffers.
### Caveat Coder
2011-12-21 13:37:53 +08:00
This is a pedagogical reinterpretation of the original JSLinux code Copyright (c) 2011 Fabrice Bellard.
2011-12-22 13:04:09 +08:00
There's no alteration in the algorithmic content. I do check that that it still runs, but I won't guarantee anything else.
### References
Some other helpful references for understanding what's going on:
http://ref.x86asm.net/coder32.html#xC4
http://en.wikibooks.org/wiki/X86_Assembly/X86_Architecture
http://en.wikipedia.org/wiki/X86
http://en.wikipedia.org/wiki/Control_register
http://en.wikipedia.org/wiki/X86_assembly_language
http://en.wikipedia.org/wiki/Translation_lookaside_buffer
http://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Programming
[1]: http://bellard.org/jslinux/tech.html
[2]: http://sshaper.org