Message-ID: <1418604052.19970.6.camel@ellerman.id.au>
Subject: Re: [PATCH 00/18] uaccess: fix sparse warning on get_user for
 bitwise types
From: Michael Ellerman <mpe@ellerman.id.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        linux-arch@vger.kernel.org
Date: Mon, 15 Dec 2014 11:40:52 +1100
In-Reply-To: <1418575877-21488-1-git-send-email-mst@redhat.com>
References: <1418575877-21488-1-git-send-email-mst@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

On Sun, 2014-12-14 at 18:51 +0200, Michael S. Tsirkin wrote:
> At the moment, if p and x are both tagged as bitwise types,
> get_user(x, p) produces a sparse warning on many architectures.
> This is because *p on these architectures is loaded into long
> (typically using asm), then cast back to typeof(*p).
> 
> When typeof(*p) is a bitwise type (which is uncommon), such a cast needs
> __force, otherwise sparse produces a warning.

What does __force actually mean? Force the cast even though it's a bitfield? Or
does it mean more than that?

ie. are we loosing the ability to detect any actual errors by adding force?

cheers


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/