RE: [PATCH v2 bpf-next 2/3] selftests/bpf: Add skb_pkt_end test

John Fastabend
2020-11-12T19:20:05Z

Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.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@kernel.org>
> ---

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