linux-kernel - Re: [PATCH 13/18] powerpc/uaccess: fix sparse errors

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Date:	Mon, 15 Dec 2014 12:37:46 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 13/18] powerpc/uaccess: fix sparse errors

On Mon, 2014-12-15 at 11:05 +1100, Benjamin Herrenschmidt wrote:
> On Sun, 2014-12-14 at 18:52 +0200, Michael S. Tsirkin wrote:
> > virtio wants to read bitwise types from userspace using get_user.  At the
> > moment this triggers sparse errors, since the value is passed through an
> > integer.
> > 
> > Fix that up using __force.
> 
> You mean bitfields ? Argh ... we should just remove them from the
> compiler and be done with it :-(

Oh... no I suppose you actually meant explicit endian fields, ie, __be32
or __le32 right ? Ack on that. It sucks a bit but I think it's
acceptable.

Cheers,
Ben.

> Ben.
> 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> >  arch/powerpc/include/asm/uaccess.h | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> > index 9485b43..a0c071d 100644
> > --- a/arch/powerpc/include/asm/uaccess.h
> > +++ b/arch/powerpc/include/asm/uaccess.h
> > @@ -284,7 +284,7 @@ do {								\
> >  	if (!is_kernel_addr((unsigned long)__gu_addr))		\
> >  		might_fault();					\
> >  	__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
> > -	(x) = (__typeof__(*(ptr)))__gu_val;			\
> > +	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
> >  	__gu_err;						\
> >  })
> >  #endif /* __powerpc64__ */
> > @@ -297,7 +297,7 @@ do {								\
> >  	might_fault();							\
> >  	if (access_ok(VERIFY_READ, __gu_addr, (size)))			\
> >  		__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
> > -	(x) = (__typeof__(*(ptr)))__gu_val;				\
> > +	(x) = (__force __typeof__(*(ptr)))__gu_val;				\
> >  	__gu_err;							\
> >  })
> >  
> > @@ -308,7 +308,7 @@ do {								\
> >  	const __typeof__(*(ptr)) __user *__gu_addr = (ptr);	\
> >  	__chk_user_ptr(ptr);					\
> >  	__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
> > -	(x) = (__typeof__(*(ptr)))__gu_val;			\
> > +	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
> >  	__gu_err;						\
> >  })
> >  
> 


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