linux-kernel - Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic

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Message-ID: <647012f4-c221-addf-51ab-586014e8f435@i-love.sakura.ne.jp>
Date:   Sat, 16 Mar 2019 23:53:35 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel
 panic - not syncing: panic_on_warn set ..."

On 2019/03/16 23:16, Dmitry Vyukov wrote:
>>> Maybe try running with "ignore_loglevel" kernel command line option added?
>>
>> Right, that's something I would expect 0-day and syzkaller to do.
> 
> to double-check: enabling this won't lead to verbose/debug level of logging?
> 

I don't know what "verbose/debug level" means. But enabling this option causes
KERN_{EMERG,ALERT,CRIT,ERR,WARNING,NOTICE,INFO,DEBUG} be printed equally.

  "ignore loglevel setting (prints all kernel messages to the console)"

static bool suppress_message_printing(int level)
{
	return (level >= console_loglevel && !ignore_loglevel);
}