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    SubjectRe: [PATCH 1/6] perf: Add new type PERF_TYPE_PROBE
    On Wed, Nov 15, 2017 at 09:23:33AM -0800, Song Liu wrote:

    > Note: We use type __u64 for pointer probe_desc instead of __aligned_u64.
    > The reason here is to avoid changing the size of struct perf_event_attr,
    > and breaking new-kernel-old-utility scenario. To avoid alignment problem
    > with the pointer, we will (in the following patches) copy probe_desc to
    > __aligned_u64 before using it as pointer.

    ISTR there are only relatively few architectures where __u64 and
    __aligned_u64 are not the same thing.

    The comment that goes with it seems to suggest i386 has short alignment
    for u64 but my compiler says differently:

    printf("%d, %d\n", sizeof(unsigned long long), __alignof__(unsigned long long));

    $ gcc -m32 -o align align.c && ./align
    8, 8

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