[CRIU] [PATCH 4/9] seccomp: Fetch seccomp flags if kernel provides

[Dmitry Safonov]

> @@ -47,6 +54,7 @@ static struct seccomp_info *find_inherited(struct pstree_item *parent,
>
>  static int collect_filter_for_pstree(struct pstree_item *item)
>  {
> +       struct seccomp_metadata meta_buf, *meta = &meta_buf;
>         struct seccomp_info *infos = NULL, *cursor;
>         int info_count, i, ret = -1;
>         struct sock_filter buf[BPF_MAXINSNS];
> @@ -75,7 +83,29 @@ static int collect_filter_for_pstree(struct pstree_item *item)
>                         }
>                 }
>
> -               inherited = find_inherited(item->parent, buf, len);
> +               if (!meta)
> +                       meta = &meta_buf;
> +
> +               meta->flags = 0;
> +               meta->filter_off = i;
> +
> +               if (ptrace(PTRACE_SECCOMP_GET_METADATA, item->pid->real, sizeof(meta), meta) < 0) {

Maybe sizeof(*meta), huh?
                                   ^
At this moment, if I see correctly in linux code - kernel will not write flags.
So, also a nit: meta->flags needs no initialization.

It would be cleaner with kdat feature..
But at least, can we do something:
if (meta && ptrace())?
It'll evaporate dirty lines with
if (!meta) meta = &meta_buf;
and will make it a bit faster on kernels without support even without kdat.

Thanks,
             Dmitry