Ruby-Elf and Sun extensions

I’ve written in my post about OpenSolaris that I’m interested in extending Ruby-Elf to parse and access Sun-specific extensions, that is the .SUNW_* sections of ELF files produced under OpenSolaris. Up to now I only knew the format, and not even that properly, of the .SUNW_cap section, that contains hardware and software capabilities for an object file or an executable, but I wasn’t sure how to interpret that.

Thanks to Roman, who sent me the link to the Sun Linker and Libraries Guide (I did know about it but I lost the link to it quite a long time ago and then I forgot it existed), now I know some more things about Sun-specific sections, and I’ve already started implementing support for those in Ruby-Elf (unfortunately I’m still looking for a way to properly test for them, in particular I’m not yet sure how I can check for the various hardware-specific extensions — also I have no idea how to test the Sparc-specific data since my Ultra5 runs FreeBSD, not Solaris). Right at the moment I write this, Ruby-Elf can properly parse the capabilities section with its flags, and report them back. Hopefully, with no mistakes, since only basic support is in the regression test for now.

One thing I really want to implement in Ruby-Elf is versioning support, with the same API I’m currently using for GNU-style symbol versioning. This way it’ll be possible for ruby-elf based tools to access both GNU and Sun versioning information as it was a single thing. Too bad I haven’t looked up yet how to generate ELF files with Sun-style versioning support. Oh well, it’ll be one more thing I’ll have to learn. Together with a way to set visibility with Sun Studio, to test the extended visibility support they have in their ELF extended format.

In general, I think that my decision of going with Ruby for this is very positive, mostly because it makes it much easier to support new stuff by just writing an extra class and hook it up, without needing “major surgery” every time. It’s easy and quick to implement new stuff and new functions, even if the tools will require more time and more power to access the data (but with the recent changes I did to properly support OS-specific sections, I think Ruby-Elf is now much faster than it was before, and uses much less memory, as only the sections actually used are loaded). Maybe one day once I can consider this good enough I’ll try to port it to some compiled language, using the Ruby version as a flow scheme, but I don’t think it’s worth the hassle.

Anyway, if you’re interested in improving Ruby-Elf and would like to see it improve even further, so that it can report further optimisations and similar things (like for instance something I planned from the start: telling which shared objects for which there’s a NEEDED line are useless, without having to load the file trough ld.so to use the LD_* variables), I can ask you one thing and one thing only: a copy of Linkers and Loaders that I can consult. I tried preparing a copy out of the original freely available HTML files for the Reader but it was quite nasty to see, nastier than O’Reilly freely-available eBooks (which are bad already). It’s in my wishlist if you want.

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