Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 20 Aug 2020 13:55:17 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Scott Branden <scott.branden@broadcom.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>, linux-kernel@vger.kernel.org,
        bcm-kernel-feedback-list@broadcom.com
Subject: Re: [PATCH v2 1/3] bcm-vk: add bcm_vk UAPI
Message-ID: <202008201353.F342E59EC@keescook>
References: <20200806004631.8102-1-scott.branden@broadcom.com>
 <20200806004631.8102-2-scott.branden@broadcom.com>
 <20200818135313.GB495837@kroah.com>
 <8894c3c4-4d5c-cb94-bc90-a26833ebf268@broadcom.com>
 <20200818174451.GA749919@kroah.com>
 <4adbd70e-c49b-c2d4-84c7-5e910f05e449@broadcom.com>
 <20200819070044.GA1004396@kroah.com>
 <fdbb7404-03c3-22b1-d409-5b6d8745ff2b@broadcom.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <fdbb7404-03c3-22b1-d409-5b6d8745ff2b@broadcom.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Aug 20, 2020 at 09:37:46AM -0700, Scott Branden wrote:
> On 2020-08-19 12:00 a.m., Greg Kroah-Hartman wrote:
> > On Tue, Aug 18, 2020 at 05:35:04PM -0700, Scott Branden wrote:
> >>
> >> On 2020-08-18 10:44 a.m., Greg Kroah-Hartman wrote:
> >>> On Tue, Aug 18, 2020 at 10:23:42AM -0700, Scott Branden wrote:
> >>>>>> +#define VK_FWSTS_RELOCATION_ENTRY	BIT(0)
> >>>>> <snip>
> >>>>>
> >>>>> I thought BIT() was not allowed in uapi .h files, this really works
> >>>>> properly???
> >>>> I did some investigation and it looks like a few other header files in include/uapi also use the BIT() macro:
> >>>> include/uapi/misc/uacce/uacce.h
> >>>> include/uapi/linux/psci.h
> >>>> include/uapi/linux/v4l2-subdev.h
> >>> Does the header install test target now fail for these?
> >> I do not understand the question above.? make headers_install works.
> >> But I guess the above headers would have similar issue with the BIT macro.
> > Try enabling CONFIG_UAPI_HEADER_TEST and see what happens :)
> I enabled CONFIG_UAPI_HEADER_TEST and then
> built using "make" and "make headers_install".
> 
> There didn't appear to be any issue with the BIT macro in the headers.

FWIW, other subsystems have not been so lucky:

https://git.kernel.org/linus/23b2c96fad21886c53f5e1a4ffedd45ddd2e85ba

It may just be better to avoid BIT(), even if it works "by accident"(?)
for some header combinations...

-- 
Kees Cook