linux-kernel - Re: [PATCH v9 03/27] kallsyms: add static relationship between `KSYM_NAME_LEN{,

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Message-ID: <202208171238.80053F8C@keescook>
Date:   Wed, 17 Aug 2022 12:39:48 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, patches@...ts.linux.dev,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: Re: [PATCH v9 03/27] kallsyms: add static relationship between
 `KSYM_NAME_LEN{,_BUFFER}`

On Fri, Aug 05, 2022 at 05:41:48PM +0200, Miguel Ojeda wrote:
> This adds a static assert to ensure `KSYM_NAME_LEN_BUFFER`
> gets updated when `KSYM_NAME_LEN` changes.
> 
> The relationship used is one that keeps the new size (512+1)
> close to the original buffer size (500).
> 
> Co-developed-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
>  scripts/kallsyms.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index f3c5a2623f71..f543b1c4f99f 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -33,7 +33,11 @@
>  #define KSYM_NAME_LEN		128
>  
>  /* A substantially bigger size than the current maximum. */
> -#define KSYM_NAME_LEN_BUFFER	499
> +#define KSYM_NAME_LEN_BUFFER	512
> +_Static_assert(
> +	KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
> +	"Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
> +);

Why not just make this define:

#define KSYM_NAME_LEN_BUFFER (KSYM_NAME_LEN * 4)

? If there's a good reason not it, please put it in the commit log.

-Kees

-- 
Kees Cook