linux-kernel - Re: [PATCH] IB/core: avoid 32-bit warning

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Date:	Wed, 07 Oct 2015 15:46:48 +0200
From:	Yann Droneaud <ydroneaud@...eya.com>
To:	Sagi Grimberg <sagig@....mellanox.co.il>,
	Arnd Bergmann <arnd@...db.de>,
	Doug Ledford <dledford@...hat.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>
Cc:	Roland Dreier <roland@...estorage.com>, linux-rdma@...r.kernel.org,
	Matan Barak <matanb@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] IB/core: avoid 32-bit warning

Hi,

Le mercredi 07 octobre 2015 à 16:19 +0300, Sagi Grimberg a écrit :
> On 10/7/2015 3:29 PM, Arnd Bergmann wrote:
> > The INIT_UDATA() macro requires a pointer or unsigned long argument
> > for
> > both input and output buffer, and all callers had a cast from when
> > the code was merged until a recent restructuring, so now we get
> > 
> > core/uverbs_cmd.c: In function 'ib_uverbs_create_cq':
> > core/uverbs_cmd.c:1481:66: warning: cast to pointer from integer of
> > different size [-Wint-to-pointer-cast]
> > 
> > This makes the code behave as before by adding back the cast to
> > unsigned long.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > Fixes: 565197dd8fb1 ("IB/core: Extend ib_uverbs_create_cq")
> > 
> > diff --git a/drivers/infiniband/core/uverbs_cmd.c
> > b/drivers/infiniband/core/uverbs_cmd.c
> > index be4cb9f04be3..88b3b78340f2 100644
> > --- a/drivers/infiniband/core/uverbs_cmd.c
> > +++ b/drivers/infiniband/core/uverbs_cmd.c
> > @@ -1478,7 +1478,7 @@ ssize_t ib_uverbs_create_cq(struct
> > ib_uverbs_file *file,
> >   	if (copy_from_user(&cmd, buf, sizeof(cmd)))
> >   		return -EFAULT;
> > 
> > -	INIT_UDATA(&ucore, buf, cmd.response, sizeof(cmd),
> > sizeof(resp));
> > +	INIT_UDATA(&ucore, buf, (unsigned long)cmd.response,
> > sizeof(cmd), sizeof(resp));
> 
> Would it make sense to cast inside INIT_UDATA() and not have callers
> worry about it?

It's ... complicated. See INIT_UDATA_BUF_OR_NULL().

Awayway, I have patch to do the opposite, eg. explicitly cast u64 value
to (void __user *)(unsigned long) in the caller function instead, as it
allows some safer / new operations on the response buffer.

Regards.

-- 
Yann Droneaud
OPTEYA

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