netdev - Re: [PATCH bpf-next v5] bpf: Add bpf_ktime_get_real

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Date:   Thu, 24 Sep 2020 16:15:21 -0600
From:   David Ahern <dsahern@...il.com>
To:     bimmy.pujari@...el.com, bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, mchehab@...nel.org, ast@...nel.org,
        daniel@...earbox.net, kafai@...com, maze@...gle.com,
        ashkan.nikravesh@...el.com
Subject: Re: [PATCH bpf-next v5] bpf: Add bpf_ktime_get_real_ns

On 9/24/20 4:07 PM, bimmy.pujari@...el.com wrote:
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index a22812561064..198e69a6508d 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3586,6 +3586,13 @@ union bpf_attr {
>   * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
>   * 	Return
>   * 		0 on success, or a negative error in case of failure.
> + *
> + * u64 bpf_ktime_get_real_ns(void)
> + *	Description
> + *		Return the real time in nanoseconds.
> + *		See: **clock_gettime**\ (**CLOCK_REALTIME**)

This should be a little more explicit -- something like "See the caveats
regarding use of CLOCK_REALTIME in clock_gettime man page."


> + *	Return
> + *		Current *ktime*.
>   */
>  #define __BPF_FUNC_MAPPER(FN)		\
>  	FN(unspec),			\
> @@ -3737,6 +3744,7 @@ union bpf_attr {
>  	FN(inode_storage_delete),	\
>  	FN(d_path),			\
>  	FN(copy_from_user),		\
> +	FN(ktime_get_real_ns),		\
>  	/* */
>  
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper