powerpc/vdso: Save and restore TOC pointer on PPC64

On PPC64, the TOC pointer needs to be saved and restored.
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-7-mpe@ellerman.id.au

arch/powerpc/include/asm/vdso/gettimeofday.h

@@ -19,10 +19,16 @@
   .cfi_register lr, r0
 	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)
 	PPC_STL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
+#ifdef __powerpc64__
+	PPC_STL		r2, PPC_MIN_STKFRM + STK_GOT(r1)
+#endif
 	get_datapage	r5, r0
 	addi		r5, r5, VDSO_DATA_OFFSET
 	bl		DOTSYM(\funct)
 	PPC_LL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
+#ifdef __powerpc64__
+	PPC_LL		r2, PPC_MIN_STKFRM + STK_GOT(r1)
+#endif
 	cmpwi		r3, 0
 	mtlr		r0
   .cfi_restore lr
@@ -42,10 +48,16 @@
   .cfi_register lr, r0
 	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)
 	PPC_STL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
+#ifdef __powerpc64__
+	PPC_STL		r2, PPC_MIN_STKFRM + STK_GOT(r1)
+#endif
 	get_datapage	r4, r0
 	addi		r4, r4, VDSO_DATA_OFFSET
 	bl		DOTSYM(\funct)
 	PPC_LL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
+#ifdef __powerpc64__
+	PPC_LL		r2, PPC_MIN_STKFRM + STK_GOT(r1)
+#endif
 	crclr		so
 	mtlr		r0
   .cfi_restore lr