Re: [PATCH 1/6] xen/arm: smccc-1.1: Make return values unsigned long

[Volodymyr Babchuk <volodymyr_babchuk@epam.com>]

Hi  Julien, Marc

On 24.08.18 19:58, Julien Grall wrote:
> From: Marc Zyngier <marc.zyngier@arm.com>
> 
> An unfortunate consequence of having a strong typing for the input
> values to the SMC call is that it also affects the type of the
> return values, limiting r0 to 32 bits and r{1,2,3} to whatever
> was passed as an input. >
> Let's turn everything into "unsigned long", which satisfies the
> requirements of both architectures, and allows for the full
> range of return values.
Maybe it better to use register_t then? By definition register_t has the 
same size as a CPU register and SMC uses CPU registers to pass 
parameters/return values.

> Reported-by: Stefano Stabellini <stefanos@xilinx.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> ---
>   xen/include/asm-arm/smccc.h | 22 +++++++++++-----------
>   1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
> index 74c13f8419..a31d67a1de 100644
> --- a/xen/include/asm-arm/smccc.h
> +++ b/xen/include/asm-arm/smccc.h
> @@ -119,35 +119,35 @@ struct arm_smccc_res {
>   
>   #define __declare_arg_0(a0, res)                        \
>       struct arm_smccc_res    *___res = res;              \
> -    register uin32_t        r0 asm("r0") = a0;          \
> +    register unsigned long  r0 asm("r0") = (uint32_t)a0;\
Do you really want to silently drop upper 32 bits of the argument?
I know, that SMCCC states that function id is a 32-bit value,
but I don't think that it is a good place to enforce this
behavior.
I think it is better to allow user to shoot in his leg in this case.

>       register unsigned long  r1 asm("r1");               \
>       register unsigned long  r2 asm("r2");               \
>       register unsigned long  r3 asm("r3")
>   
>   #define __declare_arg_1(a0, a1, res)                    \
>       struct arm_smccc_res    *___res = res;              \
> -    register uint32_t       r0 asm("r0") = a0;          \
> -    register typeof(a1)     r1 asm("r1") = a1;          \
> +    register unsigned long  r0 asm("r0") = (uint32_t)a0;\
> +    register unsigned long  r1 asm("r1") = a1;          \
>       register unsigned long  r2 asm("r2");               \
>       register unsigned long  r3 asm("r3")
>   
>   #define __declare_arg_2(a0, a1, a2, res)                \
>       struct arm_smccc_res    *___res = res;				\
> -    register u32            r0 asm("r0") = a0;          \
> -    register typeof(a1)     r1 asm("r1") = a1;          \
> -    register typeof(a2)     r2 asm("r2") = a2;          \
> +    register unsigned long  r0 asm("r0") = (uint32_t)a0;\
> +    register unsigned long  r1 asm("r1") = a1;          \
> +    register unsigned long  r2 asm("r2") = a2;          \
>       register unsigned long  r3 asm("r3")
>   
>   #define __declare_arg_3(a0, a1, a2, a3, res)            \
>       struct arm_smccc_res    *___res = res;              \
> -    register u32            r0 asm("r0") = a0;          \
> -    register typeof(a1)     r1 asm("r1") = a1;          \
> -    register typeof(a2)     r2 asm("r2") = a2;          \
> -    register typeof(a3)     r3 asm("r3") = a3
> +    register unsigned long  r0 asm("r0") = (uint32_t)a0;\
> +    register unsigned long  r1 asm("r1") = a1;          \
> +    register unsigned long  r2 asm("r2") = a2;          \
> +    register unsigned long  r3 asm("r3") = a3
>   
>   #define __declare_arg_4(a0, a1, a2, a3, a4, res)        \
>       __declare_arg_3(a0, a1, a2, a3, res);               \
> -    register typeof(a4) r4 asm("r4") = a4
> +    register unsigned long r4 asm("r4") = a4
>   
>   #define __declare_arg_5(a0, a1, a2, a3, a4, a5, res)    \
>       __declare_arg_4(a0, a1, a2, a3, a4, res);           \
> 

-- 
Volodymyr Babchuk

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