Re: [PATCH bpf-next 3/3] bpf: introduce bpf_relay_output helper

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, Dec 22, 2023 at 08:21:46PM +0800, Philo Lu wrote:
> Like perfbuf/ringbuf, a helper is needed to write into the buffer, named
> bpf_relay_output, whose usage is same as ringbuf. Note that it works only
> after relay files are set, i.e., after calling map_update_elem for the
> created relay map.

we can't add helpers anymore, this will need to be kfunc
check functions marked with __bpf_kfunc as examples

jirka

> 
> Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
> ---
>  include/linux/bpf.h      |  1 +
>  include/uapi/linux/bpf.h | 10 ++++++++++
>  kernel/bpf/helpers.c     |  4 ++++
>  kernel/bpf/relaymap.c    | 26 ++++++++++++++++++++++++++
>  kernel/bpf/verifier.c    |  8 ++++++++
>  kernel/trace/bpf_trace.c |  4 ++++
>  6 files changed, 53 insertions(+)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 7671530d6e4e..b177122369e6 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3095,6 +3095,7 @@ extern const struct bpf_func_proto bpf_get_retval_proto;
>  extern const struct bpf_func_proto bpf_user_ringbuf_drain_proto;
>  extern const struct bpf_func_proto bpf_cgrp_storage_get_proto;
>  extern const struct bpf_func_proto bpf_cgrp_storage_delete_proto;
> +extern const struct bpf_func_proto bpf_relay_output_proto;
>  
>  const struct bpf_func_proto *tracing_prog_func_proto(
>    enum bpf_func_id func_id, const struct bpf_prog *prog);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 143b75676bd3..03c0c1953ba1 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5686,6 +5686,15 @@ union bpf_attr {
>   *		0 on success.
>   *
>   *		**-ENOENT** if the bpf_local_storage cannot be found.
> + *
> + * long bpf_relay_output(void *map, void *data, u64 size, u64 flags)
> + * 	Description
> + * 		Copy *size* bytes from *data* into *map* of type BPF_MAP_TYPE_RELAY.
> + * 		Currently, the *flags* must be 0.
> + * 	Return
> + * 		0 on success.
> + *
> + *		**-ENOENT** if the relay base_file in debugfs cannot be found.
>   */
>  #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
>  	FN(unspec, 0, ##ctx)				\
> @@ -5900,6 +5909,7 @@ union bpf_attr {
>  	FN(user_ringbuf_drain, 209, ##ctx)		\
>  	FN(cgrp_storage_get, 210, ##ctx)		\
>  	FN(cgrp_storage_delete, 211, ##ctx)		\
> +	FN(relay_output, 212, ##ctx)		\
>  	/* */
>  
>  /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index be72824f32b2..0c26e87ce729 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1720,6 +1720,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>  		return &bpf_ringbuf_discard_proto;
>  	case BPF_FUNC_ringbuf_query:
>  		return &bpf_ringbuf_query_proto;
> +#ifdef CONFIG_RELAY
> +	case BPF_FUNC_relay_output:
> +		return &bpf_relay_output_proto;
> +#endif
>  	case BPF_FUNC_strncmp:
>  		return &bpf_strncmp_proto;
>  	case BPF_FUNC_strtol:
> diff --git a/kernel/bpf/relaymap.c b/kernel/bpf/relaymap.c
> index 588c8de0a4bd..f9e2e4a780df 100644
> --- a/kernel/bpf/relaymap.c
> +++ b/kernel/bpf/relaymap.c
> @@ -173,6 +173,32 @@ static u64 relay_map_mem_usage(const struct bpf_map *map)
>  	return usage;
>  }
>  
> +BPF_CALL_4(bpf_relay_output, struct bpf_map *, map, void *, data, u64, size,
> +	   u64, flags)
> +{
> +	struct bpf_relay_map *rmap;
> +
> +	/* not support any flag now */
> +	if (unlikely(flags))
> +		return -EINVAL;
> +
> +	rmap = container_of(map, struct bpf_relay_map, map);
> +	if (!rmap->relay_chan->has_base_filename)
> +		return -ENOENT;
> +
> +	relay_write(rmap->relay_chan, data, size);
> +	return 0;
> +}
> +
> +const struct bpf_func_proto bpf_relay_output_proto = {
> +	.func		= bpf_relay_output,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_CONST_MAP_PTR,
> +	.arg2_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
> +	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
> +	.arg4_type	= ARG_ANYTHING,
> +};
> +
>  BTF_ID_LIST_SINGLE(relay_map_btf_ids, struct, bpf_relay_map)
>  const struct bpf_map_ops relay_map_ops = {
>  	.map_meta_equal = bpf_map_meta_equal,
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index f13008d27f35..8c8287d6ae18 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -8800,6 +8800,10 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
>  		if (func_id != BPF_FUNC_user_ringbuf_drain)
>  			goto error;
>  		break;
> +	case BPF_MAP_TYPE_RELAY:
> +		if (func_id != BPF_FUNC_relay_output)
> +			goto error;
> +		break;
>  	case BPF_MAP_TYPE_STACK_TRACE:
>  		if (func_id != BPF_FUNC_get_stackid)
>  			goto error;
> @@ -8932,6 +8936,10 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
>  		if (map->map_type != BPF_MAP_TYPE_USER_RINGBUF)
>  			goto error;
>  		break;
> +	case BPF_FUNC_relay_output:
> +		if (map->map_type != BPF_MAP_TYPE_RELAY)
> +			goto error;
> +		break;
>  	case BPF_FUNC_get_stackid:
>  		if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
>  			goto error;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 7ac6c52b25eb..5b13553c6232 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1594,6 +1594,10 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_ringbuf_discard_proto;
>  	case BPF_FUNC_ringbuf_query:
>  		return &bpf_ringbuf_query_proto;
> +#ifdef CONFIG_RELAY
> +	case BPF_FUNC_relay_output:
> +		return &bpf_relay_output_proto;
> +#endif
>  	case BPF_FUNC_jiffies64:
>  		return &bpf_jiffies64_proto;
>  	case BPF_FUNC_get_task_stack:
> -- 
> 2.32.0.3.g01195cf9f
>