Re: [edk2-devel] [PATCH v3 02/13] ArmPkg/ArmSvcLib: Return x4-x7 in output parameters

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 15 Jan 2021 at 07:14, Sughosh Ganu <sughosh.ganu@linaro.org> wrote:
>
> From: Achin Gupta <achin.gupta@arm.com>
>
> The Arm SMC calling convention standard v1.2 allows 8 input and output
> parameter registers. The FF-A specification relies on this
> communication. This patch extends the number of output registers
> returned by ArmCallSvc() to match this convention.
>
> Signed-off-by: Achin Gupta <achin.gupta@arm.com>
> Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>
> Changes since V2: None
>
>  ArmPkg/Include/Library/ArmSvcLib.h        | 10 ++++++++--
>  ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S |  4 +++-
>  2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/ArmPkg/Include/Library/ArmSvcLib.h b/ArmPkg/Include/Library/ArmSvcLib.h
> index a94ead1965..a4414270f3 100644
> --- a/ArmPkg/Include/Library/ArmSvcLib.h
> +++ b/ArmPkg/Include/Library/ArmSvcLib.h
> @@ -27,10 +27,16 @@ typedef struct {
>  /**
>    Trigger an SVC call
>
> -  SVC calls can take up to 7 arguments and return up to 4 return values.
> -  Therefore, the 4 first fields in the ARM_SVC_ARGS structure are used
> +  SVC calls can take up to 8 arguments and return up to 8 return values.
> +  Therefore, the 8 first fields in the ARM_SVC_ARGS structure are used
>    for both input and output values.
>
> +  @param[in, out]    Args Arguments to be passed as part of the SVC call
> +                     The return values of the SVC call are also placed
> +                     in the same structure
> +
> +  @retval None
> +
>  **/
>  VOID
>  ArmCallSvc (
> diff --git a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
> index ee265f94b9..1a7c10cb79 100644
> --- a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
> +++ b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
> @@ -33,9 +33,11 @@ ASM_PFX(ArmCallSvc):
>    ldr   x9, [sp, #16]
>
>    // Store the SVC returned values into the ARM_SVC_ARGS structure.
> -  // A SVC call can return up to 4 values - we do not need to store back x4-x7.
> +  // A SVC call can return up to 8 values
>    stp   x0, x1, [x9, #0]
>    stp   x2, x3, [x9, #16]
> +  stp   x4, x5, [x9, #32]
> +  stp   x6, x7, [x9, #48]
>
>    mov   x0, x9
>
> --
> 2.17.1
>
>
>
> 
>
>