• Daniel Borkmann's avatar
    bpf: add BPF_CALL_x macros for declaring helpers · f3694e00
    Daniel Borkmann authored
    This work adds BPF_CALL_<n>() macros and converts all the eBPF helper functions
    to use them, in a similar fashion like we do with SYSCALL_DEFINE<n>() macros
    that are used today. Motivation for this is to hide all the register handling
    and all necessary casts from the user, so that it is done automatically in the
    background when adding a BPF_CALL_<n>() call.
    
    This makes current helpers easier to review, eases to write future helpers,
    avoids getting the casting mess wrong, and allows for extending all helpers at
    once (f.e. build time checks, etc). It also helps detecting more easily in
    code reviews that unused registers are not instrumented in the code by accident,
    breaking compatibility with existing programs.
    
    BPF_CALL_<n>() internals are quite similar to SYSCALL_DEFINE<n>() ones with some
    fundamental differences, for example, for generating the actual helper function
    that carries all u64 regs, we need to fill unused regs, so that we always end up
    with 5 u64 regs as an argument.
    
    I reviewed several 0-5 generated BPF_CALL_<n>() variants of the .i results and
    they look all as expected. No sparse issue spotted. We let this also sit for a
    few days with Fengguang's kbuild test robot, and there were no issues seen. On
    s390, it barked on the "uses dynamic stack allocation" notice, which is an old
    one from bpf_perf_event_output{,_tp}() reappearing here due to the conversion
    to the call wrapper, just telling that the perf raw record/frag sits on stack
    (gcc with s390's -mwarn-dynamicstack), but that's all. Did various runtime tests
    and they were fine as well. All eBPF helpers are now converted to use these
    macros, getting rid of a good chunk of all the raw castings.
    Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    f3694e00
bpf_trace.c 16 KB