Re: [PATCH V7 13/20] riscv: compat: process: Add UXL_32 support in start_thread

[Guo Ren]

Hi Arnd,

On Mon, Feb 28, 2022 at 12:30 AM <guoren@xxxxxxxxxx> wrote:
>
> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> ---
>  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/