linux-kernel - Re: [PATCH] Remove hardcoded static string length

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Message-ID: <CAOWid-eEbeeU9mOpwgOatt5rHQhRt+xPrsQ1fsMemVZDdeN=MQ@mail.gmail.com>
Date:   Thu, 25 May 2023 10:27:53 -0400
From:   Kenny Ho <y2kenny@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Marc Dionne <marc.dionne@...istor.com>,
        Kenny Ho <Kenny.Ho@....com>,
        David Howells <dhowells@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Remove hardcoded static string length

On Thu, May 25, 2023 at 5:14 AM David Laight <David.Laight@...lab.com> wrote:
>
> I does rather beg the question as what is in UTS_RELEASE when
> it exceeds (IIRC) about 48 characters?

Thanks for the question as it made me dig deeper.  UTS_RELEASE is
actually capped at 64:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/Makefile?#n1317
"""
uts_len := 64
define filechk_utsrelease.h
if [ `echo -n "$(KERNELRELEASE)" | wc -c ` -gt $(uts_len) ]; then \
 echo '"$(KERNELRELEASE)" exceeds $(uts_len) characters' >&2;    \
 exit 1;                                                         \
...
"""

So UTS_RELEASE on its own would fit perfectly by coincidence (and it
is also why UTS_RELEASE with the pre and postfix exceeds the limit.)
That makes me wonder if the content / format of the version matter and
looks like it sort of does by looking at when the string was
introduced:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/net/rxrpc/local_object.c?id=44ba06987c0b10faa998b9324850e8a6564c714d

"The standard formulation seems to be: <project> <version> built
<yyyy>-<mm>-<dd>"

That commit also confirms the size and null termination requirement.

I will create a separate patch with your suggestion.

Regards,
Kenny