netdev - Re: [bpf PATCH v2 4/5] bpf, selftests: Add tests for sock

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Date:   Wed, 29 Jul 2020 14:36:23 -0700
From:   Song Liu <song@...nel.org>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Martin KaFai Lau <kafai@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [bpf PATCH v2 4/5] bpf, selftests: Add tests for sock_ops load
 with r9, r8.r7 registers

On Wed, Jul 29, 2020 at 9:24 AM John Fastabend <john.fastabend@...il.com> wrote:
>
> Loads in sock_ops case when using high registers requires extra logic to
> ensure the correct temporary value is used. We need to ensure the temp
> register does not use either the src_reg or dst_reg. Lets add an asm
> test to force the logic is triggered.
>
> The xlated code is here,
>
>   30: (7b) *(u64 *)(r9 +32) = r7
>   31: (61) r7 = *(u32 *)(r9 +28)
>   32: (15) if r7 == 0x0 goto pc+2
>   33: (79) r7 = *(u64 *)(r9 +0)
>   34: (63) *(u32 *)(r7 +916) = r8
>   35: (79) r7 = *(u64 *)(r9 +32)
>
> Notice r9 and r8 are not used for temp registers and r7 is chosen.
>
> Signed-off-by: John Fastabend <john.fastabend@...il.com>

Acked-by: Song Liu <songliubraving@...com>

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