linux-kernel - Re: arm: ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240304114546.4e8e1e32@donnerap.manchester.arm.com>
Date: Mon, 4 Mar 2024 11:45:46 +0000
From: Andre Przywara <andre.przywara@....com>
To: "Arnd Bergmann" <arnd@...db.de>
Cc: "Naresh Kamboju" <naresh.kamboju@...aro.org>, "open list"
 <linux-kernel@...r.kernel.org>, "Linux ARM"
 <linux-arm-kernel@...ts.infradead.org>, linux-sunxi@...ts.linux.dev,
 dri-devel@...ts.freedesktop.org, lkft-triage@...ts.linaro.org, "Maxime
 Ripard" <mripard@...nel.org>, "Dave Airlie" <airlied@...hat.com>, "Dan
 Carpenter" <dan.carpenter@...aro.org>, "Ard Biesheuvel" <ardb@...nel.org>
Subject: Re: arm: ERROR: modpost: "__aeabi_uldivmod"
 [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!

On Mon, 04 Mar 2024 12:26:46 +0100
"Arnd Bergmann" <arnd@...db.de> wrote:

> On Mon, Mar 4, 2024, at 12:24, Andre Przywara wrote:
> > On Mon, 04 Mar 2024 12:11:36 +0100 "Arnd Bergmann" <arnd@...db.de> wrote:  
> >>
> >> This used to be a 32-bit division. If the rate is never more than
> >> 4.2GHz, clock could be turned back into 'unsigned long' to avoid
> >> the expensive div_u64().  
> >
> > Wouldn't "div_u64(clock, 200)" solve this problem?  
> 
> Yes, that's why I mentioned it as the worse of the two obvious
> solutions. ;-)

Argh, should have cleaned my glasses first ;-)

I guess I was put somehow put off by the word "expensive". While it's
admittedly not trivial, I wonder if we care about the (hidden) complexity
of that function? I mean it's neither core code nor something called
frequently?
I don't think we have any clock exceeding 3GHz at the moment, but it
sounds fishy to rely on that.

Cheers,
Andre