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    SubjectRe: [PATCH] perf_counter: extensible perf_counter_attr

    * Paul Mackerras <paulus@samba.org> wrote:

    > Peter Zijlstra writes:
    >
    > > Allow extending the perf_counter_attr structure by linking extended
    > > structures to it.
    >
    > ...
    >
    > > @@ -175,6 +175,13 @@ struct perf_counter_attr {
    > > __u32 __reserved_3;
    > >
    > > __u64 __reserved_4;
    > > +
    > > + struct perf_counter_attr_ext *ext_attrs;
    > > +};
    >
    > Since this is a user-visible structure, you've just introduced an
    > ABI difference between 32-bit and 64-bit processes, which we've
    > managed to avoid so far. [...]

    This is a good point too - handling pointers in ABIs is possible but
    should be avoided as much as possible: it creates the need to
    introduce a compat_sys_perf_counter_open() and doubles the syscall
    table complexity.

    Lets do the s/__reserved_1/attr_size ABI i suggested (i outlined
    various properties of it in the previous mail). Agreed?

    Ingo


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