Subject: Re: [PATCH net-next] net: filter: cleanup invocation of internal BPF

From: Daniel Borkmann <[email-masked]>
Date: Tue, 20 May 2014 10:57:13 +0200

On 05/19/2014 11:56 PM, Alexei Starovoitov wrote:
> Kernel API for classic BPF socket filters is:
>
> sk_unattached_filter_create() - validate classic BPF, convert, JIT
> SK_RUN_FILTER() - run it
> sk_unattached_filter_destroy() - destroy socket filter
>
> Cleanup internal BPF kernel API as following:
>
> sk_filter_select_runtime() - final step of internal BPF creation.
>    Try to JIT internal BPF program, if JIT is not available select interpreter
> SK_RUN_FILTER() - run it
> sk_filter_free() - free internal BPF program
>
> Disallow direct calls to BPF interpreter. Execution of the BPF program should
> be done with SK_RUN_FILTER() macro.
>
> Example of internal BPF create, run, destroy:
>
>    struct sk_filter *fp;
>
>    fp = kzalloc(sk_filter_size(prog_len), GFP_KERNEL);
>    memcpy(fp->insni, prog, prog_len * sizeof(fp->insni[0]));
>    fp->len = prog_len;
>
>    sk_filter_select_runtime(fp);
>
>    SK_RUN_FILTER(fp, ctx);
>
>    sk_filter_free(fp);
>
> Sockets, seccomp, testsuite, tracing are using different ways to populate
> sk_filter, so first steps of program creation are not common.
>
> Signed-off-by: Alexei Starovoitov <[email-masked]>

I think it makes sense and we can avoid directly exposing the symbol
__sk_run_filter() resp. its aliases.

Acked-by: Daniel Borkmann <[email-masked]>