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

[Christophe Leroy]

Le 20/08/2019 Ã 12:06, Peter Zijlstra a ÃcritÂ:
> On Mon, Aug 19, 2019 at 04:41:11PM -0700, Kees Cook wrote:
>
> > diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> > index 588dd59a5b72..da471fcc5487 100644
> > --- a/include/asm-generic/bug.h
> > +++ b/include/asm-generic/bug.h
> > @@ -10,6 +10,7 @@
> >   #define BUGFLAG_WARNING		(1 << 0)
> >   #define BUGFLAG_ONCE		(1 << 1)
> >   #define BUGFLAG_DONE		(1 << 2)
> > +#define BUGFLAG_PRINTK		(1 << 3)
> >   #define BUGFLAG_TAINT(taint)	((taint) << 8)
> >   #define BUG_GET_TAINT(bug)	((bug)->flags >> 8)
> >   #endif
>
> > diff --git a/lib/bug.c b/lib/bug.c
> > 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.

Christophe