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    SubjectRe: [PATCH v13 net-next 07/11] bpf: verifier (add ability to receive verification log)
    On 09/18/2014 04:34 PM, Alexei Starovoitov wrote:
    > On Wed, Sep 17, 2014 at 11:44 PM, Daniel Borkmann <dborkman@redhat.com> wrote:
    ...
    >> Sure, you will never get a full compatibility on that regard
    >> while backwards compatibility needs to be guaranteed on the
    >> other hand. I looked at perf_copy_attr() implementation and I
    >> think that we should mimic it in a very similar way as it
    >> exactly solves what we need.
    >>
    >> For example, it will return with -EINVAL for (size > PAGE_SIZE)
    >> and (size < PERF_ATTR_SIZE_VER0) where PAGE_SIZE has been chosen
    >> as an arbitrary hard upper limit where it is believed that it will
    >> never grow beyond that large limit in future.
    >>
    >> So this is a more loose constraint than what we currently do,
    >> that is, -EINVAL on (size > sizeof(attr)) where attr is the
    >> currently known size of a specific kernel. That would at least
    >> be a start, you won't be able to cover everything though, but
    >> it would allow to address the issue raised when running with
    >> a basic feature set.
    >
    > you missed my point. We should not 'do a start', since it
    > doesn't help user space in the long run and only makes
    > kernel more complex.

    Sorry, I don't think I missed your point. But if you see things
    differently, fair enough, it was just a suggestion.


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