Re: [PATCH v4 11/20] powerpc: Add ZEROIZE_GPRS macros for register clears
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2022-09-12 11:10:23
On Wed Aug 24, 2022 at 12:05 PM AEST, 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.
Can I bikeshed this a bit more and ask if you would change the order? Saving and restoring macros are incidental, and are neither the change nor the reson for it. I think the changelog reads better if you state the change (or the problem) up front. Provid register zeroing macros ... follow the same convention as existing register stack save/restore macros ... will be used in later change to zero registers. Or not, if you disagree. Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
quoted hunk ↗ jump to hunk
The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping with the naming of the accompanying restore and save macros, and usage of zeroize to describe this operation elsewhere in the kernel. Signed-off-by: Rohan McLure <redacted> --- 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. V3 -> V4: Update commit message to use zeroize. --- 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)-- 2.34.1