[PATCH v3 15/18] powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers

[Rohan McLure <rmclure@linux.ibm.com>]

Use the convenience macros for saving/clearing/restoring gprs in keeping
with syscall calling conventions. The plural variants of these macros
can store a range of registers for concision.

This works well when the user gpr value we are hoping to save is still
live. In the syscall interrupt handlers, user register state is
sometimes juggled between registers. Hold-off from issuing the SAVE_GPR
macro for applicable neighbouring lines to highlight the delicate
register save logic.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Update summary
V2 -> V3: Update summary regarding exclusions for the SAVE_GPR marco.
Acknowledge new name for ZEROIZE_GPR{,S} macros.
---
 arch/powerpc/kernel/interrupt_64.S | 51 +++++++---------------------
 1 file changed, 13 insertions(+), 38 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index d9625113c7a5..ad302ad93433 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -71,12 +71,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
 	mfcr	r12
 	li	r11,0
 	/* Save syscall parameters in r3-r8 */
-	std	r3,GPR3(r1)
-	std	r4,GPR4(r1)
-	std	r5,GPR5(r1)
-	std	r6,GPR6(r1)
-	std	r7,GPR7(r1)
-	std	r8,GPR8(r1)
+	SAVE_GPRS(3, 8, r1)
 	/* Zero r9-r12, this should only be required when restoring all GPRs */
 	std	r11,GPR9(r1)
 	std	r11,GPR10(r1)
@@ -113,8 +108,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 * Zero user registers to prevent influencing speculative execution
 	 * state of kernel code.
 	 */
-	NULLIFY_GPRS(5, 12)
-	NULLIFY_NVGPRS()
+	ZEROIZE_GPRS(5, 12)
+	ZEROIZE_NVGPRS()
 
 	/* Calling convention has r3 = orig r0, r4 = regs */
 	mr	r3,r0
@@ -157,17 +152,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	/* Could zero these as per ABI, but we may consider a stricter ABI
 	 * which preserves these if libc implementations can benefit, so
 	 * restore them for now until further measurement is done. */
-	ld	r0,GPR0(r1)
-	ld	r4,GPR4(r1)
-	ld	r5,GPR5(r1)
-	ld	r6,GPR6(r1)
-	ld	r7,GPR7(r1)
-	ld	r8,GPR8(r1)
+	REST_GPR(0, r1)
+	REST_GPRS(4, 8, r1)
 	/* Zero volatile regs that may contain sensitive kernel data */
-	li	r9,0
-	li	r10,0
-	li	r11,0
-	li	r12,0
+	ZEROIZE_GPRS(9, 12)
 	mtspr	SPRN_XER,r0
 
 	/*
@@ -189,7 +177,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r4,_LINK(r1)
 	ld	r5,_XER(r1)
 
-	ld	r0,GPR0(r1)
+	REST_GPR(0, r1)
 	mtcr	r2
 	mtctr	r3
 	mtlr	r4
@@ -257,12 +245,7 @@ END_BTB_FLUSH_SECTION
 	mfcr	r12
 	li	r11,0
 	/* Save syscall parameters in r3-r8 */
-	std	r3,GPR3(r1)
-	std	r4,GPR4(r1)
-	std	r5,GPR5(r1)
-	std	r6,GPR6(r1)
-	std	r7,GPR7(r1)
-	std	r8,GPR8(r1)
+	SAVE_GPRS(3, 8, r1)
 	/* Zero r9-r12, this should only be required when restoring all GPRs */
 	std	r11,GPR9(r1)
 	std	r11,GPR10(r1)
@@ -311,8 +294,8 @@ END_BTB_FLUSH_SECTION
 	 * Zero user registers to prevent influencing speculative execution
 	 * state of kernel code.
 	 */
-	NULLIFY_GPRS(5, 12)
-	NULLIFY_NVGPRS()
+	ZEROIZE_GPRS(5, 12)
+	ZEROIZE_NVGPRS()
 
 	/* Calling convention has r3 = orig r0, r4 = regs */
 	mr	r3,r0
@@ -360,16 +343,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	cmpdi	r3,0
 	bne	.Lsyscall_restore_regs
 	/* Zero volatile regs that may contain sensitive kernel data */
-	li	r0,0
-	li	r4,0
-	li	r5,0
-	li	r6,0
-	li	r7,0
-	li	r8,0
-	li	r9,0
-	li	r10,0
-	li	r11,0
-	li	r12,0
+	ZEROIZE_GPR(0)
+	ZEROIZE_GPRS(4, 12)
 	mtctr	r0
 	mtspr	SPRN_XER,r0
 .Lsyscall_restore_regs_cont:
@@ -394,7 +369,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r4,_XER(r1)
 	mtctr	r3
 	mtspr	SPRN_XER,r4
-	ld	r0,GPR0(r1)
+	REST_GPR(0, r1)
 	REST_GPRS(4, 12, r1)
 	b	.Lsyscall_restore_regs_cont
 .Lsyscall_rst_end:
-- 
2.34.1