powerpc: simplify ppc_save_regs

Adjust the pt_regs pointer so the interrupt frame offsets can be used
to save registers.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221127124942.1665522-7-npiggin@gmail.com

arch/powerpc/kernel/ppc_save_regs.S

@@ -21,60 +21,33 @@
  * different ABIs, though).
  */
 _GLOBAL(ppc_save_regs)
-	PPC_STL	r0,0*SZL(r3)
+	/* This allows stack frame accessor macros and offsets to be used */
+	subi	r3,r3,STACK_FRAME_OVERHEAD
+	PPC_STL	r0,GPR0(r3)
 #ifdef CONFIG_PPC32
-	stmw	r2, 2*SZL(r3)
+	stmw	r2,GPR2(r3)
 #else
-	PPC_STL	r2,2*SZL(r3)
-	PPC_STL	r3,3*SZL(r3)
-	PPC_STL	r4,4*SZL(r3)
-	PPC_STL	r5,5*SZL(r3)
-	PPC_STL	r6,6*SZL(r3)
-	PPC_STL	r7,7*SZL(r3)
-	PPC_STL	r8,8*SZL(r3)
-	PPC_STL	r9,9*SZL(r3)
-	PPC_STL	r10,10*SZL(r3)
-	PPC_STL	r11,11*SZL(r3)
-	PPC_STL	r12,12*SZL(r3)
-	PPC_STL	r13,13*SZL(r3)
-	PPC_STL	r14,14*SZL(r3)
-	PPC_STL	r15,15*SZL(r3)
-	PPC_STL	r16,16*SZL(r3)
-	PPC_STL	r17,17*SZL(r3)
-	PPC_STL	r18,18*SZL(r3)
-	PPC_STL	r19,19*SZL(r3)
-	PPC_STL	r20,20*SZL(r3)
-	PPC_STL	r21,21*SZL(r3)
-	PPC_STL	r22,22*SZL(r3)
-	PPC_STL	r23,23*SZL(r3)
-	PPC_STL	r24,24*SZL(r3)
-	PPC_STL	r25,25*SZL(r3)
-	PPC_STL	r26,26*SZL(r3)
-	PPC_STL	r27,27*SZL(r3)
-	PPC_STL	r28,28*SZL(r3)
-	PPC_STL	r29,29*SZL(r3)
-	PPC_STL	r30,30*SZL(r3)
-	PPC_STL	r31,31*SZL(r3)
+	SAVE_GPRS(2, 31, r3)
 	lbz	r0,PACAIRQSOFTMASK(r13)
-	PPC_STL	r0,SOFTE-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,SOFTE(r3)
 #endif
 	/* go up one stack frame for SP */
 	PPC_LL	r4,0(r1)
-	PPC_STL	r4,1*SZL(r3)
+	PPC_STL	r4,GPR1(r3)
 	/* get caller's LR */
 	PPC_LL	r0,LRSAVE(r4)
-	PPC_STL	r0,_LINK-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_LINK(r3)
 	mflr	r0
-	PPC_STL	r0,_NIP-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_NIP(r3)
 	mfmsr	r0
-	PPC_STL	r0,_MSR-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_MSR(r3)
 	mfctr	r0
-	PPC_STL	r0,_CTR-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_CTR(r3)
 	mfxer	r0
-	PPC_STL	r0,_XER-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_XER(r3)
 	mfcr	r0
-	PPC_STL	r0,_CCR-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_CCR(r3)
 	li	r0,0
-	PPC_STL	r0,_TRAP-STACK_FRAME_OVERHEAD(r3)
-	PPC_STL	r0,ORIG_GPR3-STACK_FRAME_OVERHEAD(r3)
+	PPC_STL	r0,_TRAP(r3)
+	PPC_STL	r0,ORIG_GPR3(r3)
 	blr