linux-kernel - Re: [PATCH V6 16/20] riscv: compat: vdso: Add rv32 VDSO base code implementation

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Date:   Thu, 24 Feb 2022 10:13:23 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Guo Ren <guoren@...nel.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>, Arnd Bergmann <arnd@...db.de>,
        Anup Patel <anup@...infault.org>,
        gregkh <gregkh@...uxfoundation.org>,
        liush <liush@...winnertech.com>, Wei Fu <wefu@...hat.com>,
        Drew Fustini <drew@...gleboard.org>,
        Wang Junqiang <wangjunqiang@...as.ac.cn>,
        Christoph Hellwig <hch@....de>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V6 16/20] riscv: compat: vdso: Add rv32 VDSO base code implementation

On Thu, Feb 24, 2022 at 9:54 AM <guoren@...nel.org> wrote:
>
> From: Guo Ren <guoren@...ux.alibaba.com>
>
> There is no vgettimeofday supported in rv32 that makes simple to
> generate rv32 vdso code which only needs riscv64 compiler. Other
> architectures need change compiler or -m (machine parameter) to
> support vdso32 compiling. If rv32 support vgettimeofday (which
> cause C compile) in future, we would add CROSS_COMPILE to support
> that makes more requirement on compiler enviornment.

I think it's just a bug that rv32 doesn't have the vdso version of the
time syscalls. Fixing that is of course independent of the compat support,
but I think you need that anyway, and it would be better to start
out by building the compat vdso with the correct
architecture level.

At least this should be a lot easier than on arch/arm64 because you
can assume that an rv64 compiler is able to also build rv32 output.

        Arnd