netdev - Re: [PATCH 1/2] kernel/bpf: change "char *" string form to "char []"

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Message-ID: <92cc4844-5815-c3b0-63be-2e54dc36e1d9@iogearbox.net>
Date:   Thu, 12 May 2022 22:59:31 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     liqiong <liqiong@...china.com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        hukun@...china.com, qixu@...china.com, yuzhe@...china.com,
        renyu@...china.com
Subject: Re: [PATCH 1/2] kernel/bpf: change "char *" string form to "char []"

On 5/12/22 7:08 PM, liqiong wrote:
> 在 2022年05月12日 23:16, Yonghong Song 写道:
>>
>> On 5/12/22 7:28 AM, liqiong wrote:
>>> The string form of "char []" declares a single variable. It is better
>>> than "char *" which creates two variables.
>>
>> Could you explain in details about why it is better in generated codes?
>> It is not clear to me why your patch is better than the original code.
> 
> The  string form of "char *" creates two variables in the final assembly output,
> a static string, and a char pointer to the static string.  Use  "objdump -S -D  *.o",
> can find out the static string  occurring  at "Contents of section .rodata".

There are ~360 instances of this type in the tree from a quick grep, do you
plan to convert all them ?

Thanks,
Daniel