Re: [Xen-devel] [PATCH 4/7] xen/arm: traps: Avoid using BUG_ON() in _show_registers()

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

Julien Grall writes:

> At the moment, _show_registers() is using a BUG_ON() to assert only
> userspace will run 32-bit code in a 64-bit domain.
>
> Such extra precaution is not necessary and could be avoided by only
> checking the CPU mode to decide whether show_registers_64() or
> show_reigsters_32() should be called.
>
> This has also the nice advantage to avoid nested if in the code.
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>

> ---
>  xen/arch/arm/traps.c | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 54e66a86d0..132686ee0f 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -914,21 +914,11 @@ static void _show_registers(const struct cpu_user_regs 
> *regs,
>  
>      if ( guest_mode )
>      {
> -        if ( is_32bit_domain(v->domain) )
> +        if ( psr_mode_is_32bit(regs) )
>              show_registers_32(regs, ctxt, guest_mode, v);
>  #ifdef CONFIG_ARM_64
> -        else if ( is_64bit_domain(v->domain) )
> -        {
> -            if ( psr_mode_is_32bit(regs) )
> -            {
> -                BUG_ON(!usr_mode(regs));
> -                show_registers_32(regs, ctxt, guest_mode, v);
> -            }
> -            else
> -            {
> -                show_registers_64(regs, ctxt, guest_mode, v);
> -            }
> -        }
> +        else
> +            show_registers_64(regs, ctxt, guest_mode, v);
>  #endif
>      }
>      else


-- 
Volodymyr Babchuk at EPAM
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