linux-kernel - Re: [PATCH] Enable '-Werror' by default for all kernel builds

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Date:   Tue, 7 Sep 2021 22:14:41 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-sparc <sparclinux@...r.kernel.org>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds

On 9/7/21 9:48 PM, Al Viro wrote:
> On Tue, Sep 07, 2021 at 09:28:38PM -0700, Guenter Roeck wrote:
> 
>> 	memcpy(eth_addr, sanitize_address((void *) 0xfffc1f2c), ETH_ALEN);
>>
>> but that just seems weird. Is there a better solution ?
> 
> (char (*)[ETH_ALEN])?  Said that, shouldn't that be doing something like
> ioremap(), rather than casting explicit constants?
> 

Typecasts or even assigning the address to a variable does not help.
The sanitizer function can not be static either.

I don't know the hardware, so I can not answer the ioremap() question.

This is just one example, though; there are several sprinkled throughout
the code. Another is:

arch/parisc/kernel/setup.c:	running_on_qemu = (memcmp(&PAGE0->pad0, "SeaBIOS", 8) == 0);

where

#define PAGE0   ((struct zeropage *)__PAGE_OFFSET)

and __PAGE_OFFSET depends on the configuration.

That code runs early in setup; I don't think ioremap() would even
be available at that time. A workaround for that problem would be
a global variable pointing to PAGE0 (or of course an address sanitizer
function), but again that seems odd just to make the compiler happy.

Guenter