linux-kernel - Re: [PATCH 7/7] bug: Move WARN_ON() "cut here" into exception handler

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Message-ID: <20190820211429.7030b6f6@oasis.local.home>
Date:   Tue, 20 Aug 2019 21:14:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Drew Davenport <ddavenport@...omium.org>,
        Arnd Bergmann <arnd@...db.de>, Feng Tang <feng.tang@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        YueHaibing <yuehaibing@...wei.com>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] bug: Move WARN_ON() "cut here" into exception
 handler

On Tue, 20 Aug 2019 12:58:49 +0200
Christophe Leroy <christophe.leroy@....fr> wrote:

> >> index 1077366f496b..6c22e8a6f9de 100644
> >> --- a/lib/bug.c
> >> +++ b/lib/bug.c
> >> @@ -181,6 +181,15 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
> >>   		}
> >>   	}
> >>   
> >> +	/*
> >> +	 * BUG() and WARN_ON() families don't print a custom debug message
> >> +	 * before triggering the exception handler, so we must add the
> >> +	 * "cut here" line now. WARN() issues its own "cut here" before the
> >> +	 * extra debugging message it writes before triggering the handler.
> >> +	 */
> >> +	if ((bug->flags & BUGFLAG_PRINTK) == 0)
> >> +		printk(KERN_DEFAULT CUT_HERE);  
> > 
> > I'm not loving that BUGFLAG_PRINTK name, BUGFLAG_CUT_HERE makes more
> > sense to me.
> >   
> 
> Actually it would be BUGFLAG_NO_CUT_HERE then, otherwise all arches not 
> using the generic macros will have to add the flag to get the "cut here" 
> line.
>

Perhaps they all should be audited to see if they don't have the same
problem?

-- Steve