Date: Fri, 24 Aug 2012 09:29:29 +0200 From: musl <b.brezillon.musl@...il.com> To: musl@...ts.openwall.com Subject: Re: ldso : dladdr support On 24/08/2012 00:21, Rich Felker wrote: > On Thu, Aug 23, 2012 at 05:39:37PM -0400, Rich Felker wrote: >> On Mon, Aug 20, 2012 at 04:32:00PM +0200, musl wrote: >>> I missed a bug in my previous patch : >>> in find_sym func precomptab was always set to sysv_precomp. >> It's still broken; h is being used in the comparisons even if h was >> not initialized, rather than using gh. I'm working on integrating the >> code right now. I'll either commit my version or reply with a patch >> here soon for review. > Here's my proposed patch for gnu hash support. I've left dladdr to be > committed separately. I handled the precomputed hashes by duplicating > the code in the two branches; this is _ugly_ but it's moderately > faster, and I really don't like the performance impact of these checks > to begin with, so I'd rather not make them even worse. > > Some other changes I've made since Boris's last version: > > - Prefer GNU hash if it's available. It's a lot faster even in single > runs, and should make even more difference when data-locality issues > come into play (resolving whole files rather than just a single > dlsym call). > > - Omit bloom filter checks. It's not clear if they're beneficial on > average in large programs, but for single lookups where the symbol > is present, they increase lookup time by about 8%. > > - Replace the over-complicated decode_vec2 with search_vec, since we > only need a single extended entry anyway. In any case, the big-O > performance of high-entry lookups will always be the same as this > linear search unless we use heavy data structures, so we might as > well just do it this super-simple way. > > Comments welcome. I'll hold off on committing for a while in case I > made any dumb mistakes. I tested it and it works well. My tests are based on small libs (with a small set of shared symbols). I mixed libs with gnu hash and sysv hash. Tried to resolve symbols via dlsym. Have you tested it on big libraries ? Do you want me to do some specific tests ? > Rich
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