powerpc: Create a helper for getting the kernel toc value

Move the logic to work out the kernel toc pointer into a header. This is
a good cleanup, and also means we can use it elsewhere in future.

Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>

arch/powerpc/include/asm/sections.h

@@ -22,6 +22,18 @@ static inline int in_kernel_text(unsigned long addr)
 	return 0;
 }
 
+static inline unsigned long kernel_toc_addr(void)
+{
+	/* Defined by the linker, see vmlinux.lds.S */
+	extern unsigned long __toc_start;
+
+	/*
+	 * The TOC register (r2) points 32kB into the TOC, so that 64kB of
+	 * the TOC can be addressed using a single machine instruction.
+	 */
+	return (unsigned long)(&__toc_start) + 0x8000UL;
+}
+
 static inline int overlaps_interrupt_vector_text(unsigned long start,
 							unsigned long end)
 {

arch/powerpc/kernel/paca.c

@@ -17,10 +17,6 @@
 #include <asm/pgtable.h>
 #include <asm/kexec.h>
 
-/* This symbol is provided by the linker - let it fill in the paca
- * field correctly */
-extern unsigned long __toc_start;
-
 #ifdef CONFIG_PPC_BOOK3S
 
 /*
@@ -149,11 +145,6 @@ EXPORT_SYMBOL(paca);
 
 void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 {
-       /* The TOC register (GPR2) points 32kB into the TOC, so that 64kB
-	* of the TOC can be addressed using a single machine instruction.
-	*/
-	unsigned long kernel_toc = (unsigned long)(&__toc_start) + 0x8000UL;
-
 #ifdef CONFIG_PPC_BOOK3S
 	new_paca->lppaca_ptr = new_lppaca(cpu);
 #else
@@ -161,7 +152,7 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 #endif
 	new_paca->lock_token = 0x8000;
 	new_paca->paca_index = cpu;
-	new_paca->kernel_toc = kernel_toc;
+	new_paca->kernel_toc = kernel_toc_addr();
 	new_paca->kernelbase = (unsigned long) _stext;
 	/* Only set MSR:IR/DR when MMU is initialized */
 	new_paca->kernel_msr = MSR_KERNEL & ~(MSR_IR | MSR_DR);