Subject: Re: [PATCH iproute2 -next 1/5] {f,m}_bpf: make tail calls working

From: Sergei Shtylyov <[email-masked]>
Date: Thu, 26 Nov 2015 16:10:44 +0300

Hello.

On 11/26/2015 3:58 PM, Daniel Borkmann wrote:

> Now that we have the possibility of sharing maps, it's time we get the
> ELF loader fully working with regards to tail calls. Since program array
> maps are pinned, we can keep them finally alive. I've noticed two bugs
> that are being fixed in bpf_fill_prog_arrays() with this patch. Example
> code comes as follow-up.
>
> Signed-off-by: Daniel Borkmann <[email-masked]>
> Acked-by: Alexei Starovoitov <[email-masked]>
> ---
>   tc/tc_bpf.c | 31 +++++++++++++++++++++++--------
>   1 file changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/tc/tc_bpf.c b/tc/tc_bpf.c
> index bc7bc9f..73a0f41 100644
> --- a/tc/tc_bpf.c
> +++ b/tc/tc_bpf.c
> @@ -1139,11 +1139,26 @@ static int bpf_fetch_prog_sec(struct bpf_elf_ctx *ctx, const char *section)
>   	return ret;
>   }
>
> +static int bpf_find_map_by_id(struct bpf_elf_ctx *ctx, uint32_t id)
> +{
> +	int i, ret = -1;
> +
> +	for (i = 0; i < ARRAY_SIZE(ctx->map_fds); i++) {
> +		if (ctx->map_fds[i] && ctx->maps[i].id == id &&
> +		    ctx->maps[i].type == BPF_MAP_TYPE_PROG_ARRAY) {
> +			ret = i;
> +			break;

    Isn't just *return* i; simpler? That way, you don't need 'ret' at all.

> +		}
> +	}
> +
> +	return ret;
> +}
> +
[...]

MBR, Sergei