linux-kernel - Re: [PATCH 1/2] soc: qcom: stats: fix 64-bit division

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: <20231206141658.kjpjwjy7utdux6b5@pengutronix.de>
Date:   Wed, 6 Dec 2023 15:16:58 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] soc: qcom: stats: fix 64-bit division

Hallo Arnd,

On Wed, Dec 06, 2023 at 01:37:06PM +0100, Arnd Bergmann wrote:
> Unguarded 64-bit division is not allowed on 32-bit kernels because this
> is very slow. The result of trying anyway is a link failure:
> 
> arm-linux-gnueabi-ld: drivers/soc/qcom/qcom_stats.o: in function `qcom_ddr_stats_show':
> qcom_stats.c:(.text+0x334): undefined reference to `__aeabi_uldivmod'
> 
> As this function is only used for debugging and not performance critical,
> rewrite it to use div_u64() instead. ARCH_TIMER_FREQ is a multiple of
> MSEC_PER_SEC anyway, so there is no loss in precisison.

Maybe add this information in a comment?

We have

	#define ARCH_TIMER_FREQ         19200000

so it's a multiple of MSEC_PER_SEC (= 1000) indeed.

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)