netdev - RE: [PATCH v2 bpf-next 2/3] selftests/bpf: Add skb_pkt

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Message-ID: <5fad8adaa7c5d_2a6120828@john-XPS-13-9370.notmuch>
Date:   Thu, 12 Nov 2020 11:19:54 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        davem@...emloft.net
Cc:     daniel@...earbox.net, netdev@...r.kernel.org, bpf@...r.kernel.org,
        kernel-team@...com
Subject: RE: [PATCH v2 bpf-next 2/3] selftests/bpf: Add skb_pkt_end test

Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@...nel.org>
> 
> Add a test that currently makes LLVM generate assembly code:
> 
> $ llvm-objdump -S skb_pkt_end.o
> 0000000000000000 <main_prog>:
> ; 	if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
>        0:	61 12 50 00 00 00 00 00	r2 = *(u32 *)(r1 + 80)
>        1:	61 14 4c 00 00 00 00 00	r4 = *(u32 *)(r1 + 76)
>        2:	bf 43 00 00 00 00 00 00	r3 = r4
>        3:	07 03 00 00 36 00 00 00	r3 += 54
>        4:	b7 01 00 00 00 00 00 00	r1 = 0
>        5:	2d 23 02 00 00 00 00 00	if r3 > r2 goto +2 <LBB0_2>
>        6:	07 04 00 00 0e 00 00 00	r4 += 14
> ; 	if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
>        7:	bf 41 00 00 00 00 00 00	r1 = r4
> 0000000000000040 <LBB0_2>:
>        8:	b4 00 00 00 ff ff ff ff	w0 = -1
> ; 	if (!(ip = get_iphdr(skb)))
>        9:	2d 23 05 00 00 00 00 00	if r3 > r2 goto +5 <LBB0_6>
> ; 	proto = ip->protocol;
>       10:	71 12 09 00 00 00 00 00	r2 = *(u8 *)(r1 + 9)
> ; 	if (proto != IPPROTO_TCP)
>       11:	56 02 03 00 06 00 00 00	if w2 != 6 goto +3 <LBB0_6>
> ; 	if (tcp->dest != 0)
>       12:	69 12 16 00 00 00 00 00	r2 = *(u16 *)(r1 + 22)
>       13:	56 02 01 00 00 00 00 00	if w2 != 0 goto +1 <LBB0_6>
> ; 	return tcp->urg_ptr;
>       14:	69 10 26 00 00 00 00 00	r0 = *(u16 *)(r1 + 38)
> 0000000000000078 <LBB0_6>:
> ; }
>       15:	95 00 00 00 00 00 00 00	exit
> 
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---

Acked-by: John Fastabend <john.fastabend@...il.com>