linux-kernel - Re: [PATCH 07/22] risc-v: replace bitmap_weight with bitmap_empty in riscv_fill

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]

Date:   Tue, 10 May 2022 22:01:30 +0530
From:   Anup Patel <anup@...infault.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Laight <David.Laight@...lab.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Nicholas Piggin <npiggin@...il.com>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Tsukasa OI <research_trasio@....a4lg.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH 07/22] risc-v: replace bitmap_weight with bitmap_empty in riscv_fill_hwcap()

On Tue, May 10, 2022 at 9:18 PM Yury Norov <yury.norov@...il.com> wrote:
>
> bitmap_empty() is better than bitmap_weight() because it may return
> earlier, and improves on readability.
>
> CC: Albert Ou <aou@...s.berkeley.edu>
> CC: Anup Patel <anup@...infault.org>
> CC: Atish Patra <atishp@...shpatra.org>
> CC: Jisheng Zhang <jszhang@...nel.org>
> CC: Palmer Dabbelt <palmer@...belt.com>
> CC: Paul Walmsley <paul.walmsley@...ive.com>
> CC: Tsukasa OI <research_trasio@....a4lg.com>
> CC: linux-riscv@...ts.infradead.org
> CC: linux-kernel@...r.kernel.org
> Signed-off-by: Yury Norov <yury.norov@...il.com>

Looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>  arch/riscv/kernel/cpufeature.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 1b2d42d7f589..f0298d756f66 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -206,11 +206,10 @@ void __init riscv_fill_hwcap(void)
>                 else
>                         elf_hwcap = this_hwcap;
>
> -               if (bitmap_weight(riscv_isa, RISCV_ISA_EXT_MAX))
> -                       bitmap_and(riscv_isa, riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
> -               else
> +               if (bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX))
>                         bitmap_copy(riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
> -
> +               else
> +                       bitmap_and(riscv_isa, riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
>         }
>
>         /* We don't support systems with F but without D, so mask those out
> --
> 2.32.0
>