[PATCH 3/8] arm64: Add new hcall HVC_CALL_FUNC

Catalin Marinas
2015-01-27T17:39:47Z

On Sat, Jan 17, 2015 at 12:23:34AM +0000, Geoff Levand wrote:
> diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> index 99c319c..4f23a48 100644
> --- a/arch/arm64/include/asm/virt.h
> +++ b/arch/arm64/include/asm/virt.h
> @@ -41,6 +41,19 @@
>
> #define HVC_CALL_HYP 3
>
> +/*
> + * HVC_CALL_FUNC - Execute a function at EL2.
> + *
> + * @x0: Physical address of the function to be executed.
> + * @x1: Passed as the first argument to the function.
> + * @x2: Passed as the second argument to the function.
> + * @x3: Passed as the third argument to the function.
> + *
> + * The called function must preserve the contents of register x18.

Can you pick a register that's normally callee saved?

> + */
> +
> +#define HVC_CALL_FUNC 4
> +
> #ifndef __ASSEMBLY__
>
> /*
> diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> index e3db3fd..b5d36e7 100644
> --- a/arch/arm64/kernel/hyp-stub.S
> +++ b/arch/arm64/kernel/hyp-stub.S
> @@ -66,9 +66,20 @@ el1_sync:
> mrs x0, vbar_el2
> b 2f
>
> -1: cmp x18, #HVC_SET_VECTORS
> - b.ne 2f
> - msr vbar_el2, x0
> +1: cmp x18, #HVC_SET_VECTORS

This line doesn't seem to have any change, apart from some whitespace.
Or did you want to drop the label?

> + b.ne 1f
> + msr vbar_el2, x0
> + b 2f
> +
> +1: cmp x18, #HVC_CALL_FUNC
> + b.ne 2f
> + mov x18, lr
> + mov lr, x0
> + mov x0, x1
> + mov x1, x2
> + mov x2, x3
> + blr lr
> + mov lr, x18
>
> 2: eret
> ENDPROC(el1_sync)

What is the calling convention for this HVC? You mentioned x18 above but
what about other registers that the called function may corrupt (x18 is
a temporary register, so it's not expected to be callee saved).

--
Catalin