Re: [RFC PATCH v4 10/29] bpf tools: Collect map definitions from 'maps' section

[Alexei Starovoitov]

On Thu, May 28, 2015 at 11:09:50AM +0800, Wangnan (F) wrote:
> 
> However this breaks a law in current design that opening phase doesn't
> talk to kernel with sys_bpf() at all. All related staff is done in loading
> phase. This principle ensures that in every systems, no matter it support
> sys_bpf() or not, can read eBPF object without failure.

I see, so you want 'parse elf' and 'create maps + load programs'
to be separate phases?
Fair enough. Then please add a call to release the information
collected from elf after program loading is done.
relocations and other things are not needed at that point.

> Moreover, we are planning to introduce hardware PMU to eBPF in the way like
> maps,
> to give eBPF programs the ability to access hardware PMU counter. I haven't

that's very interesting. Please share more info when you can :)
If I understood it right, you want in-kernel bpf to do aggregation
and filtering of pmu counters ?
And computing a number of cache misses between two kprobe events?
I can see how I can use that to measure not only time
taken by syscall, but number of cache misses occurred due
to syscall. Sounds very useful!

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