Re: [PATCH] printk: Add loglevel for "do not print to consoles".

[Tetsuo Handa]

On 2020/04/25 1:21, Steven Rostedt wrote:
> On Sat, 25 Apr 2020 01:10:15 +0900
> Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> 
>> KERN_NO_CONSOLES is a mechanism for implementing user decided policy. As long as
>> userspace can control whether to use KERN_NO_CONSOLES (e.g. sysctl), there should
>> be no problem with adding KERN_NO_CONSOLES (i.e. this patch) to the kernel side.
> 
> How would you define what gets "KERN_NO_CONSOLES"? Is it going to be a
> sysctl switch?

Yes. See
https://lkml.kernel.org/r/c95dfafb-fe9c-19d7-8d42-bcd7d0946867@xxxxxxxxxxxxxxxxxxx .

> 
> Also, how does one control the log level of prints with KERN_NO_CONSOLES?

I couldn't understand the question.

KERN_NO_CONSOLES is just a flag for not to call call_console_drivers().
Messages printed with printk(KERN_$LOGLEVEL KERN_NO_CONSOLES ...) will be
read by userspace syslog daemon and be filtered based on KERN_$LOGLEVEL.