[PATCH] ARM: kernel: Fix interrupted SMC calls

[Russell King - ARM Linux admin]

On Mon, Jan 18, 2021 at 09:21:53PM +0530, Manivannan Sadhasivam wrote:
> @@ -27,10 +29,18 @@ UNWIND(	.fnstart)
>  UNWIND(	.save	{r4-r7})
>  	ldm	r12, {r4-r7}
>  	\instr
> +	mov	r9, r6			// Copy r6 before popping from stack
>  	pop	{r4-r7}
>  	ldr	r12, [sp, #(4 * 4)]
>  	stm	r12, {r0-r3}
> -	bx	lr
> +	ldr	r10, [sp, #20]
> +	cmp	r10, #0
> +	beq	1f			// No quirk structure
> +	ldr     r11, [r10, #ARM_SMCCC_QUIRK_ID_OFFS]
> +	cmp     r11, #ARM_SMCCC_QUIRK_QCOM_A6
> +	bne	1f			// No quirk present
> +	str	r9, [r10, #ARM_SMCCC_QUIRK_STATE_OFFS]
> +1:	bx	lr

NAK. This patch shows little regard for the C ABI. You are corrupting
registers that must be preserved. Please find out about the C ABIs
that are used on ARM.

Thanks.

-- 
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