linux-kernel - Re: [PATCH v4 3/6] sysctl: Warn when a clamped sysctl parameter is set out of range

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Date:   Mon, 12 Mar 2018 17:04:57 -0400
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v4 3/6] sysctl: Warn when a clamped sysctl parameter is
 set out of range

On 03/12/2018 05:00 PM, Andrew Morton wrote:
> On Mon, 12 Mar 2018 16:15:41 -0400 Waiman Long <longman@...hat.com> wrote:
>
>> Even with clamped sysctl parameters, it is still not that straight
>> forward to figure out the exact range of those parameters. One may
>> try to write extreme parameter values to see if they get clamped.
>> To make it easier, a warning with the expected range will now be
>> printed into the kernel ring buffer when a clamped sysctl parameter
>> receives an out of range value.
>>
>> The pr_warn_ratelimited() macro is used to limit the number of warning
>> messages that can be printed within a given period of time.
>>
>> ...
>>
>> +#ifdef pr_fmt
>> +#undef pr_fmt
>> +#endif
>> +#define pr_fmt(fmt)	"sysctl: " fmt
> Why is it necessary to undefine pr_fmt?  That's a somewhat unusual
> thing to do.
>
>
Because it is defined in the printk.h. I should have put the pr_fmt
definition before the iinclude file to eliminate the need to undefine it.

-Longman