Messages in this thread | | | Date | Wed, 4 Aug 2010 18:18:22 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCHv9 2.6.35-rc4-tip 2/13] uprobes: Breakpoint insertion/removal in user space applications. |
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* Peter Zijlstra <peterz@infradead.org> [2010-08-04 14:05:28]:
> On Tue, 2010-07-20 at 12:52 +0530, Srikar Dronamraju wrote: > > > Just wondering why these are function pointers. Do we exepect an > > > architecture to provide different versions of these for say 32 vs 64-bit > > > binaries? If not just making these arch provided helpers might be a lot > > > simpler. Especially in the current version where only very few of these > > > are overriden by the architecture at all. > > > > > > > Some of these functions are purely optional example being > > validate_address. > > > > Some of these functions need not be defined by the architecture in > > which case we default to the functions defined in common code. > > examples being: read_opcode, set_bkpt, and set_orig_insn. > > > > Some of these functions are architecture mode specific, for example > > there is a architecture specific pre_xol needed for x86_64. However > > generic pre_xol for x86_32 would suffice for x86_32. > > > > Some of these functions need to be mandatorily defined by the > > architecture. example being set_ip and analyze_insn. > > > > Apart from the above flexibilities and enforcements that we can make > > when we use function pointers, its would be handy to incorporate > > more enhancements like return probes and booster. > > Still not sure why you're using this vector though, why not use weak > function for optionals and defaults and no implementation for mandatory > functions (and if the implementations fails to provide it, that will > result in a link error).
Yes, we can certainly use weak functions instead of pointers. One another reason why we had these as function pointers in a structure was that it would easy be for a person porting uprobes to a new architecture. i.e person porting to a new architecture knows in one place(structure) which all functions need to be provided.
However I would go with your suggestion and make the changes to use weak functions in the next version of the patchset.
> > Are there likely to be multiple different versions of this method vector > around on a running kernel?
No for a running kernel, there will be only one method vector.
Also wanted to check with if you had tried perf probes and had comments/suggestions on any of the other patches in the patchset.
-- Thanks and Regards Srikar
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