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

[Guo Ren]

On Fri, Mar 11, 2022 at 9:38 PM Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
>
> On 11/03/2022 02:38, Guo Ren wrote:
> > 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].
>
> would an if (IS_ENABLED(CONFIG_COMPAT)) { } around the lot be better
> than an #ifdef here?
I don't think, seems #ifdef CONFIG_COMPAT is more commonly used in arch/*

>
> >>   }
> >>
> >>   void flush_thread(void)
> >> --
> >> 2.25.1
> >>
> >
> >
>
>
> --
> Ben Dooks                               http://www.codethink.co.uk/
> Senior Engineer                         Codethink - Providing Genius
>
> https://www.codethink.co.uk/privacy.html



-- 
Best Regards
 Guo Ren

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