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References: <20220227162831.674483-1-guoren@kernel.org> <20220227162831.674483-14-guoren@kernel.org>
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From:   Guo Ren <guoren@kernel.org>
Date:   Fri, 11 Mar 2022 10:38:09 +0800
Message-ID: <CAJF2gTSJFMg1YJ=dbaNyemNV4sc_3P=+_PrS=RD_Y2_xz3TzPA@mail.gmail.com>
Subject: Re: [PATCH V7 13/20] riscv: compat: process: Add UXL_32 support in start_thread
To:     Guo Ren <guoren@kernel.org>, Palmer Dabbelt <palmer@dabbelt.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Anup Patel <anup@brainfault.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        liush <liush@allwinnertech.com>, Wei Fu <wefu@redhat.com>,
        Drew Fustini <drew@beagleboard.org>,
        Wang Junqiang <wangjunqiang@iscas.ac.cn>,
        Christoph Hellwig <hch@lst.de>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        linux-csky@vger.kernel.org,
        linux-s390 <linux-s390@vger.kernel.org>,
        sparclinux <sparclinux@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Parisc List <linux-parisc@vger.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Guo Ren <guoren@linux.alibaba.com>
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Hi Arnd,

On Mon, Feb 28, 2022 at 12:30 AM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.alibaba.com>
>
> If the current task is in COMPAT mode, set SR_UXL_32 in status for
> returning userspace. We need CONFIG _COMPAT to prevent compiling
> errors with rv32 defconfig.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> ---
>  arch/riscv/kernel/process.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index 03ac3aa611f5..54787ca9806a 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -97,6 +97,11 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
>         }
>         regs->epc = pc;
>         regs->sp = sp;
> +
FIxup:

+ #ifdef CONFIG_COMPAT
> +       if (is_compat_task())
> +               regs->status = (regs->status & ~SR_UXL) | SR_UXL_32;
> +       else
> +               regs->status = (regs->status & ~SR_UXL) | SR_UXL_64;
+ #endif

We still need "#ifdef CONFIG_COMPAT" here, because for rv32 we can't
set SR_UXL at all. SR_UXL is BIT[32, 33].

>  }
>
>  void flush_thread(void)
> --
> 2.25.1
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/