[PATCH v2 09/14] powerpc: Add NULLIFY_GPRS macros for register clears
Andrew Donnellan
ajd at linux.ibm.com
Mon Aug 8 17:42:41 AEST 2022
On Mon, 2022-07-25 at 16:29 +1000, Rohan McLure wrote:
> 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 NULLIFY_GPRS and NULLIFY_NVGPRS,
> keeping
> with the naming of the accompanying restore and save macros, and
> usage
> of nullify to describe this operation elsewhere in the kernel.
>
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
> V1 -> V2: Change 'ZERO' usage in naming to 'NULLIFY', a more obvious
> verb
And I see you've addressed my comment re 32 v 64 bit from V1 as well.
Reviewed-by: Andrew Donnellan <ajd at linux.ibm.com>
> ---
> 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..d6c46082bf7f 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 NULLIFY_REGS start, end
> + .Lreg=\start
> + .rept (\end - \start + 1)
> + li .Lreg, 0
> + .Lreg=.Lreg+1
> + .endr
> +.endm
> +
I suppose this could be done using the existing OP_REGS macro,
something like OP_REGS li, 0, start, end, 0, 0 - but a load immediate
is semantically a bit different from the existing uses of OP_REGS so I
don't mind either way
> /*
> * 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 NULLIFY_GPRS(start, end) NULLIFY_REGS start,
> end
> +#ifdef __powerpc64__
> +#define NULLIFY_NVGPRS() NULLIFY_GPRS(14, 31)
> +#else
> +#define NULLIFY_NVGPRS() NULLIFY_GPRS(13, 31)
> +#endif
> +#define NULLIFY_GPR(n) NULLIFY_GPRS(n, n)
> +
> #define SAVE_GPR(n, base) SAVE_GPRS(n, n, base)
> #define REST_GPR(n, base) REST_GPRS(n, n, base)
>
--
Andrew Donnellan OzLabs, ADL Canberra
ajd at linux.ibm.com IBM Australia Limited
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