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From: Kees Cook <keescook@chromium.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Drew Davenport <ddavenport@chromium.org>,
	Arnd Bergmann <arnd@arndb.de>, Feng Tang <feng.tang@intel.com>,
	Petr Mladek <pmladek@suse.com>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	Borislav Petkov <bp@suse.de>, YueHaibing <yuehaibing@huawei.com>,
	linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/7] bug: Move WARN_ON() "cut here" into exception handler
Date: Sat, 24 Aug 2019 10:17:39 -0700	[thread overview]
Message-ID: <201908241016.9DCD43AF1@keescook> (raw)
In-Reply-To: <20190820211429.7030b6f6@oasis.local.home>

On Tue, Aug 20, 2019 at 09:14:29PM -0400, Steven Rostedt wrote:
> On Tue, 20 Aug 2019 12:58:49 +0200
> Christophe Leroy <christophe.leroy@c-s.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?

As far as I could tell, all the other combinations end up either using
the slow path bug helpers or the common exception handler.
warn-with-a-fmt-string is the only case that does the "early cut here".

-- 
Kees Cook

      reply	other threads:[~2019-08-28 17:36 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-19 23:41 [PATCH 0/7] Clean up WARN() "cut here" handling Kees Cook
2019-08-19 23:41 ` [PATCH 1/7] bug: Refactor away warn_slowpath_fmt_taint() Kees Cook
2019-08-19 23:41 ` [PATCH 2/7] bug: Rename __WARN_printf_taint() to __WARN_printf() Kees Cook
2019-08-19 23:41 ` [PATCH 3/7] bug: Consolidate warn_slowpath_fmt() usage Kees Cook
2019-08-19 23:41 ` [PATCH 4/7] bug: Lift "cut here" out of __warn() Kees Cook
2019-08-19 23:41 ` [PATCH 5/7] bug: Clean up helper macros to remove __WARN_TAINT() Kees Cook
2019-08-19 23:41 ` [PATCH 6/7] bug: Consolidate __WARN_FLAGS usage Kees Cook
2019-08-19 23:41 ` [PATCH 7/7] bug: Move WARN_ON() "cut here" into exception handler Kees Cook
2019-08-20 10:06   ` Peter Zijlstra
2019-08-20 10:58     ` Christophe Leroy
2019-08-20 16:33       ` Kees Cook
2019-08-21  0:50         ` Steven Rostedt
2019-08-21  1:14       ` Steven Rostedt
2019-08-24 17:17         ` Kees Cook [this message]

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