linux-kernel - Re: [RFC v1 09/14] krsi: Add a helper function for bpf_perf_event

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Date:   Sat, 14 Sep 2019 18:23:43 +0000
From:   Yonghong Song <yhs@...com>
To:     KP Singh <kpsingh@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...omium.org>,
        "Michael Halcrow" <mhalcrow@...gle.com>,
        Paul Turner <pjt@...gle.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Mickaël Salaün <mic@...ikod.net>,
        Florent Revest <revest@...omium.org>,
        Martin Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "Mauro Carvalho Chehab" <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        "Quentin Monnet" <quentin.monnet@...ronome.com>,
        Andrey Ignatov <rdna@...com>, "Joe Stringer" <joe@...d.net.nz>
Subject: Re: [RFC v1 09/14] krsi: Add a helper function for
 bpf_perf_event_output



On 9/10/19 12:55 PM, KP Singh wrote:
> From: KP Singh <kpsingh@...gle.com>
> 
> This helper is mapped to the existing operation
> BPF_FUNC_perf_event_output.
> 
> An example usage of this function would be:
> 
> #define BUF_SIZE 64;
> 
> struct bpf_map_def SEC("maps") perf_map = {
>          .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
>          .key_size = sizeof(int),
>          .value_size = sizeof(u32),
>          .max_entries = MAX_CPUS,
> };

could you use a map definition similar to
tools/testing/selftests/bpf/progs/test_perf_buffer.c?

struct {
         __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
         __uint(key_size, sizeof(int));
         __uint(value_size, sizeof(u32));
} perf_map SEC(".maps");

> 
> SEC("krsi")
> int bpf_prog1(void *ctx)
> {
> 	char buf[BUF_SIZE];
> 	int len;
> 	u64 flags = BPF_F_CURRENT_CPU;
> 
> 	/* some logic that fills up buf with len data*/
> 	len = fill_up_buf(buf);
> 	if (len < 0)
> 		return len;
> 	if (len > BU)
BUF_SIZE?
> 		return 0;
> 
> 	bpf_perf_event_output(ctx, &perf_map, flags, buf len);
buf, len?
> 	return 0;
> }
> 
> A sample program that showcases the use of bpf_perf_event_output is
> added later.
> 
> Signed-off-by: KP Singh <kpsingh@...gle.com>
> ---
>   security/krsi/ops.c | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/security/krsi/ops.c b/security/krsi/ops.c
> index a61508b7018f..57bd304a03f4 100644
> --- a/security/krsi/ops.c
> +++ b/security/krsi/ops.c
> @@ -111,6 +111,26 @@ static bool krsi_prog_is_valid_access(int off, int size,
>   	return false;
>   }
>   
> +BPF_CALL_5(krsi_event_output, void *, log,

Maybe name the first argument as 'ctx' to follow typical helper convention?

> +	   struct bpf_map *, map, u64, flags, void *, data, u64, size)
> +{
> +	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
> +		return -EINVAL;
> +
> +	return bpf_event_output(map, flags, data, size, NULL, 0, NULL);
> +}
> +
> +static const struct bpf_func_proto krsi_event_output_proto =  {
> +	.func		= krsi_event_output,
> +	.gpl_only       = true,
> +	.ret_type       = RET_INTEGER,
> +	.arg1_type      = ARG_PTR_TO_CTX,
> +	.arg2_type      = ARG_CONST_MAP_PTR,
> +	.arg3_type      = ARG_ANYTHING,
> +	.arg4_type      = ARG_PTR_TO_MEM,
> +	.arg5_type      = ARG_CONST_SIZE_OR_ZERO,
> +};
> +
>   static const struct bpf_func_proto *krsi_prog_func_proto(enum bpf_func_id
>   							 func_id,
>   							 const struct bpf_prog
> @@ -121,6 +141,8 @@ static const struct bpf_func_proto *krsi_prog_func_proto(enum bpf_func_id
>   		return &bpf_map_lookup_elem_proto;
>   	case BPF_FUNC_get_current_pid_tgid:
>   		return &bpf_get_current_pid_tgid_proto;
> +	case BPF_FUNC_perf_event_output:
> +		return &krsi_event_output_proto;
>   	default:
>   		return NULL;
>   	}
>