netdev - Re: [PATCH bpf-next v1 7/8] bpf: Propagate bpf_per_cpu

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Date:   Thu, 20 Aug 2020 10:30:35 -0700
From:   Yonghong Song <yhs@...com>
To:     Hao Luo <haoluo@...gle.com>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>
CC:     Shuah Khan <shuah@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Quentin Monnet <quentin@...valent.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Andrey Ignatov <rdna@...com>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH bpf-next v1 7/8] bpf: Propagate bpf_per_cpu_ptr() to
 /tools



On 8/19/20 3:40 PM, Hao Luo wrote:
> Sync tools/include/linux/uapi/bpf.h with include/linux/uapi/bpf.h

This can be folded into the previous patch.

> 
> Signed-off-by: Hao Luo <haoluo@...gle.com>
> ---
>   tools/include/uapi/linux/bpf.h | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 468376f2910b..7e3dfb2bbb86 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -3415,6 +3415,20 @@ union bpf_attr {
>    *		A non-negative value equal to or less than *size* on success,
>    *		or a negative error in case of failure.
>    *
> + * void *bpf_per_cpu_ptr(const void *ptr, u32 cpu)
> + *	Description
> + *		Take the address of a percpu ksym and return a pointer pointing
> + *		to the variable on *cpu*. A ksym is an extern variable decorated
> + *		with '__ksym'. A ksym is percpu if there is a global percpu var
> + *		(either static or global) defined of the same name in the kernel.
> + *
> + *		bpf_per_cpu_ptr() has the same semantic as per_cpu_ptr() in the
> + *		kernel, except that bpf_per_cpu_ptr() may return NULL. This
> + *		happens if *cpu* is larger than nr_cpu_ids. The caller of
> + *		bpf_per_cpu_ptr() must check the returned value.
> + *	Return
> + *		A generic pointer pointing to the variable on *cpu*.
> + *
>    */
>   #define __BPF_FUNC_MAPPER(FN)		\
>   	FN(unspec),			\
> @@ -3559,6 +3573,7 @@ union bpf_attr {
>   	FN(skc_to_tcp_request_sock),	\
>   	FN(skc_to_udp6_sock),		\
>   	FN(get_task_stack),		\
> +	FN(bpf_per_cpu_ptr),		\
>   	/* */
>   
>   /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>