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    SubjectRe: [REGRESSION][PATCH V4 3/3] bpf jit: Let the powerpc jit handle negative offsets
    On Mon, 2012-04-30 at 12:43 +1000, Benjamin Herrenschmidt wrote:

    > Ok, he hasn't so I'll dig a bit.
    > No obvious wrongness (but I'm not very familiar with bpf), though I do
    > have a comment: sk_negative_common() and bpf_slow_path_common() should
    > be made one and single macro which takes the fallback function as an
    > argument.
    > I'll mess around & try to test using Jan test case & will come back
    > with an updated patch.

    Wow, hit that nasty along the way: The test program will not work
    on big endian machines because of a nasty difference between
    the kernel struct sock_fprog and libpcap struct bpf_program:

    Kernel expects:

    struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
    unsigned short len; /* Number of filter blocks */
    struct sock_filter __user *filter;

    libpcap provides:

    struct bpf_program {
    u_int bf_len;
    struct bpf_insn *bf_insns;

    Note the unsigned short vs. unsigned int there ? This totally
    breaks it here.

    Is it expected that one can pass a struct bpf_program directly
    to the kernel or should it be "converted" by the library in which
    case it's just a bug in Jan's test program ?


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