Re: [PATCH] bpf: Expose bpf_sk_storage_* to iterator programs

[Martin KaFai Lau]

On Thu, Nov 12, 2020 at 09:09:14PM +0100, Florent Revest wrote:
> From: Florent Revest <revest@xxxxxxxxxx>
> 
> Iterators are currently used to expose kernel information to userspace
> over fast procfs-like files but iterators could also be used to
> initialize local storage. For example, the task_file iterator could be
> used to store associations between processes and sockets.
> 
> This exposes the socket local storage helpers to all iterators. Martin
> Kafai checked that this was safe to call these helpers from the
> sk_storage_map iterators.
> 
> Signed-off-by: Florent Revest <revest@xxxxxxxxxx>
> ---
>  kernel/trace/bpf_trace.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index e4515b0f62a8..3530120fa280 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -17,6 +17,8 @@
>  #include <linux/error-injection.h>
>  #include <linux/btf_ids.h>
>  
> +#include <net/bpf_sk_storage.h>
> +
>  #include <uapi/linux/bpf.h>
>  #include <uapi/linux/btf.h>
>  
> @@ -1750,6 +1752,14 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		       NULL;
>  	case BPF_FUNC_d_path:
>  		return &bpf_d_path_proto;
> +	case BPF_FUNC_sk_storage_get:
> +		return prog->expected_attach_type == BPF_TRACE_ITER ?
> +		       &bpf_sk_storage_get_proto :
> +		       NULL;
> +	case BPF_FUNC_sk_storage_delete:
> +		return prog->expected_attach_type == BPF_TRACE_ITER ?
> +		       &bpf_sk_storage_delete_proto :
> +		       NULL;
Test(s) is needed.  e.g. iterating a bpf_sk_storage_map and also
calling bpf_sk_storage_get/delete.

I would expect to see another test/example
showing how it works end-to-end to solve the problem you have in hand.
This patch probably belongs to a longer series.

BTW, I am also enabling bpf_sk_storage_(get|delete) for FENTRY/FEXIT/RAW_TP
but I think the conflict should be manageable.
https://patchwork.ozlabs.org/project/netdev/patch/20201112211313.2587383-1-kafai@xxxxxx/