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[23.128.96.18]) by mx.google.com with ESMTP id k22si1803749jak.36.2021.09.08.03.20.48; Wed, 08 Sep 2021 03:20:59 -0700 (PDT) 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; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347806AbhIHKMT (ORCPT + 99 others); Wed, 8 Sep 2021 06:12:19 -0400 Received: from mail-vs1-f47.google.com ([209.85.217.47]:43644 "EHLO mail-vs1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347877AbhIHKMQ (ORCPT ); Wed, 8 Sep 2021 06:12:16 -0400 Received: by mail-vs1-f47.google.com with SMTP id u1so1510814vsq.10; Wed, 08 Sep 2021 03:11:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IbTzHHY/WI6T/MMG5snxRp97B/nG4as15XsvK/bKWX4=; b=fBW3TtAosz9IDzfFHHzIYfivloccAdP+HvWiQ9qlFR/eD6A3PLK14QLW3XCckDFXlF WNz9HVVNyOX+vuzJ2LyojJkdbW5euu3WxJ1zk1q7Pg3rwsXUQYcLAYExmMt9z6gpxA0I OkU3lCqMqj1nWFZjksQRbWJQjjApdke4Yo/nRL8BQxtOM+4iZ24OD/7SNhTKy2fG2Zfp kchTBnMKY02j7nRHPxCOpqOARzZTh4OWEq5n9JqZkZ33NWdnxKNylyL75vKDIHAaPytK oze+QeIDquA63AUPP0OuSrQZvkWphVr+f5llLJ+PwZe0Ix7IpGxq6LUZDaC7GgN1Ja59 YMGQ== X-Gm-Message-State: AOAM533VbkLq61wlEcR1jBp1ACiS4uocyfBYO8GW0SorTMbXetosYlPU R2FX/w24W3IDMTsmTx1dDxh/Shd73fe8+r+HCsw= X-Received: by 2002:a67:cb0a:: with SMTP id b10mr1424921vsl.9.1631095868938; Wed, 08 Sep 2021 03:11:08 -0700 (PDT) MIME-Version: 1.0 References: <20210906142615.GA1917503@roeck-us.net> <20210906234921.GA1394069@roeck-us.net> <20210908042838.GA2585993@roeck-us.net> In-Reply-To: From: Geert Uytterhoeven Date: Wed, 8 Sep 2021 12:10:57 +0200 Message-ID: Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds To: Arnd Bergmann Cc: Guenter Roeck , Al Viro , Linus Torvalds , "David S. Miller" , Dmitry Torokhov , Christian Koenig , Huang Rui , Linux Kernel Mailing List , linux-sparc , Martin Sebor Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, On Wed, Sep 8, 2021 at 11:50 AM Arnd Bergmann wrote: > On Wed, Sep 8, 2021 at 9:49 AM Geert Uytterhoeven wrote: > > On Wed, Sep 8, 2021 at 7:16 AM Guenter Roeck wrote: > > > 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. > > > > So it can only be fixed by obfuscating the constant address in a > > chain of out-of-line functions... > > How is this compiler to be used for bare-metal programming? > > I reported this as a gcc bug when I first saw it back in March: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578 > > Martin Sebor suggested marking the pointer as 'volatile' as a workaround, > which is probably fine for bare-metal programming, but I would consider > that bad style for the kernel boot arguments. The RELOC_HIDE trick is probably > fine here, as there are only a couple of instances, and for the network > driver, using volatile is probably appropriate as well. Yeah, volatile should be fine for drivers. In fact this is one of the few places where I/O registers are accessed without involving volatile. > I still hope this can be fixed in a future gcc-11.x release. Maybe we should > add further instances of the problem on the gcc bug to boost the priority? > > > > I don't know the hardware, so I can not answer the ioremap() question. > > > > Yes it should. But this driver dates back to 2.1.110, when only > > half of the architectures already had ioremap(). > > How does mvme16x even create the mapping? Is this a virtual address > that is hardwired to the bus or do you have a static mapping somewhere? It's part of the transparent mapping of the top address space for I/O devices in arch/m68k/kernel/head.S. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds