Re: [PATCH bpf-next] bpf:syscall: Log error code on trampoline unlink failure

[Leon Hwang]

In subject, 'bpf:' is enough, 'syscall:' can be dropped.

On 16/7/26 11:34, xu.xin16@xxxxxxxxxx wrote:
> From: xu xin <xu.xin16@xxxxxxxxxx>
> 
> Replace silent WARN_ON_ONCE with WARN_ONCE that prints the actual error
> code from bpf_trampoline_unlink_prog(). This aids debugging of race
> conditions during link teardown, while keeping the warning rate limited
> to avoid log flooding.


Have you tried to trace bpf_trampoline_unlink_prog() with fexit?

bpftrace -lv 'fexit:bpf_trampoline_unlink_prog'
kretfunc:vmlinux:bpf_trampoline_unlink_prog
    struct bpf_tramp_node * node
    struct bpf_trampoline * tr
    struct bpf_prog * tgt_prog
    int retval

Since bpf_trampoline_unlink_prog() can be traced with fexit, it seems
unnecessary for this change?

Thanks,
Leon

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