linux-kernel - Re: [PATCH v2 2/6] arm64: perf: Implement correct cap_user

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: <20200715083800.GC10769@hirez.programming.kicks-ass.net>
Date:   Wed, 15 Jul 2020 10:38:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Cercueil <paul@...pouillou.net>,
        "Ben Dooks (Codethink)" <ben.dooks@...ethink.co.uk>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/6] arm64: perf: Implement correct cap_user_time

On Wed, Jul 15, 2020 at 10:05:08AM +0800, Leo Yan wrote:

> [leoyan: Use quot/rem to convert cyc to ns to avoid overflow]

> +		quot = rd->epoch_cyc >> rd->shift;
> +		rem = rd->epoch_cyc & (((u64)1 << rd->shift) - 1);
> +		ns = quot * rd->mult + ((rem * rd->mult) >> rd->shift);
> +		userpg->time_zero -= ns;

I think we have mul_u64_u32_shr() for that.