Re: [PATCH v2 7/7] bug: Move WARN_ON() "cut here" into exception handler

[Christophe Leroy]

Le 23/08/2019 Ã 00:56, Andrew Morton a ÃcritÂ:
> On Tue, 20 Aug 2019 09:47:55 -0700 Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> > Reply-To: 20190819234111.9019-8-keescook@xxxxxxxxxxxx
>
> Really?

That seems correct, that's the "[PATCH 7/7] bug: Move WARN_ON() "cut 
here" into exception handler" from the series at 
https://lkml.org/lkml/2019/8/19/1155


> > Subject: [PATCH v2 7/7] bug: Move WARN_ON() "cut here" into exception handler
>
> It's strange to receive a standalone [7/7] patch.

Iaw the Reply_To, I understand it as an update of the 7th patch of the 
series.

> > Date:   Tue, 20 Aug 2019 09:47:55 -0700
> > Sender: linux-kernel-owner@xxxxxxxxxxxxxxx
> >
> > The original clean up of "cut here" missed the WARN_ON() case (that
> > does not have a printk message), which was fixed recently by adding
> > an explicit printk of "cut here". This had the downside of adding a
> > printk() to every WARN_ON() caller, which reduces the utility of using
> > an instruction exception to streamline the resulting code. By making
> > this a new BUGFLAG, all of these can be removed and "cut here" can be
> > handled by the exception handler.
> >
> > This was very pronounced on PowerPC, but the effect can be seen on
> > x86 as well. The resulting text size of a defconfig build shows some
> > small savings from this patch:
> >
> >     text    data     bss     dec     hex filename
> > 19691167        5134320 1646664 26472151        193eed7 vmlinux.before
> > 19676362        5134260 1663048 26473670        193f4c6 vmlinux.after
> >
> > This change also opens the door for creating something like BUG_MSG(),
> > where a custom printk() before issuing BUG(), without confusing the "cut
> > here" line.
>
> I can't get this to apply to anything, so I guess that [1/7]-[6/7]
> mattered ;)

On my side it applies cleanly on top of patch 1-6 of the series.

Christophe


> > Reported-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > Fixes: Fixes: 6b15f678fb7d ("include/asm-generic/bug.h: fix "cut here" for WARN_ON for __WARN_TAINT architectures")
>
> I'm seeing double.
>
> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>