[PATCH v3 11/18] powerpc: Add ZEROIZE_GPRS macros for register clears

[Christophe Leroy]

Le 19/08/2022 à 05:37, Rohan McLure a écrit :
> Macros for restoring and saving registers to and from the stack exist.
> Provide macros with the same interface for clearing a range of gprs by
> setting each register's value in that range to zero.
> 
> The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping
> with the naming of the accompanying restore and save macros, and usage
> of nullify to describe this operation elsewhere in the kernel.

s/nullify/zeroize

> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
> V1 -> V2: Change 'ZERO' usage in naming to 'NULLIFY', a more obvious verb
> V2 -> V3: Change 'NULLIFY' usage in naming to 'ZEROIZE', which has
> precedent in kernel and explicitly specifies that we are zeroing.
> ---
>   arch/powerpc/include/asm/ppc_asm.h | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
> index 83c02f5a7f2a..b95689ada59c 100644
> --- a/arch/powerpc/include/asm/ppc_asm.h
> +++ b/arch/powerpc/include/asm/ppc_asm.h
> @@ -33,6 +33,20 @@
>   	.endr
>   .endm
>   
> +/*
> + * This expands to a sequence of register clears for regs start to end
> + * inclusive, of the form:
> + *
> + *   li rN, 0
> + */
> +.macro ZEROIZE_REGS start, end
> +	.Lreg=\start
> +	.rept (\end - \start + 1)
> +	li	.Lreg, 0
> +	.Lreg=.Lreg+1
> +	.endr
> +.endm
> +
>   /*
>    * Macros for storing registers into and loading registers from
>    * exception frames.
> @@ -49,6 +63,14 @@
>   #define REST_NVGPRS(base)		REST_GPRS(13, 31, base)
>   #endif
>   
> +#define	ZEROIZE_GPRS(start, end)	ZEROIZE_REGS start, end
> +#ifdef __powerpc64__
> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(14, 31)
> +#else
> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(13, 31)
> +#endif
> +#define	ZEROIZE_GPR(n)			ZEROIZE_GPRS(n, n)
> +
>   #define SAVE_GPR(n, base)		SAVE_GPRS(n, n, base)
>   #define REST_GPR(n, base)		REST_GPRS(n, n, base)
>