linux-kernel - Re: linux-next: Tree for Jan 12 (build failures: m68k, ppc)

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Date:	Mon, 12 Jan 2015 09:59:20 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Linux-Next <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Clark <robdclark@...il.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: linux-next: Tree for Jan 12 (build failures: m68k, ppc)

On Mon, Jan 12, 2015 at 05:27:08PM +0100, Geert Uytterhoeven wrote:
> On Mon, Jan 12, 2015 at 5:24 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> > On Mon, Jan 12, 2015 at 06:03:22PM +1100, Stephen Rothwell wrote:
> >> Hi all,
> >>
> >> Changes since 20150109:
> >>
> >> The usb-gadget-fixes tree gained a conflict against the usb.current tree.
> >>
> >> The net-next tree gained a build failure for which I reverted a commit.
> >>
> >> The pinctrl tree gained a build failure so I used the version from
> >> next-20150109.
> >>
> >> The akpm tree lost a few patches that turned up elsewhere.
> >>
> >> Non-merge commits (relative to Linus' tree): 2202
> >>  2272 files changed, 69868 insertions(+), 38441 deletions(-)
> >>
> >
> > Build failures, seen since next-20150109:
> >         m68k:allmodconfig
> >         powerpc:ppc6xx_defconfig
> >
> > Due to:
> >         ERROR: "__get_user_bad" [drivers/gpu/drm/drm.ko] undefined!
> >         make[1]: *** [__modpost] Error 1
> >
> > Caused by commit d34f20d6e2f (drm: Atomic modeset ioctl).
> 
> Yeah, it needs a get_user() that supports 64-bit data.
> 
Hi Geert,

I assume you mean m68k, where 64 bit support for get_user has been disabled.

The problem on powerpc is different though: __get_user_nocheck()
and __get_user_check() use
	unsigned long __gu_val;
followed by
	__get_user_size(__gu_val, __gu_addr, (size), __gu_err);

__get_user_size() fails in
	if (size > sizeof(x))
		 (x) = __get_user_bad();

Presumably "unsigned long" is 32 bit on 32 bit powerpc, not 64 bit.

Overall, the explicit 64-bit use of get_user() seems to be quite unusual.

Thanks,
Guenter
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