ARM: add PROC_VTABLE and PROC_TABLE macros

Allow the way we access members of the processor vtable to be changed
at compile time.  We will need to move to per-CPU vtables to fix the
Spectre variant 2 issues on big.Little systems.

However, we have a couple of calls that do not need the vtable
treatment, and indeed cause a kernel warning due to the (later) use
of smp_processor_id(), so also introduce the PROC_TABLE macro for
these which always use CPU 0's function pointers.
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/include/asm/proc-fns.h

@@ -23,7 +23,7 @@ struct mm_struct;
 /*
  * Don't change this structure - ASM code relies on it.
  */
-extern struct processor {
+struct processor {
 	/* MISC
 	 * get data abort address/flags
 	 */
@@ -79,9 +79,13 @@ extern struct processor {
 	unsigned int suspend_size;
 	void (*do_suspend)(void *);
 	void (*do_resume)(void *);
-} processor;
+};
 
 #ifndef MULTI_CPU
+static inline void init_proc_vtable(const struct processor *p)
+{
+}
+
 extern void cpu_proc_init(void);
 extern void cpu_proc_fin(void);
 extern int cpu_do_idle(void);
@@ -98,18 +102,27 @@ extern void cpu_reset(unsigned long addr, bool hvc) __attribute__((noreturn));
 extern void cpu_do_suspend(void *);
 extern void cpu_do_resume(void *);
 #else
-#define cpu_proc_init			processor._proc_init
-#define cpu_check_bugs			processor.check_bugs
-#define cpu_proc_fin			processor._proc_fin
-#define cpu_reset			processor.reset
-#define cpu_do_idle			processor._do_idle
-#define cpu_dcache_clean_area		processor.dcache_clean_area
-#define cpu_set_pte_ext			processor.set_pte_ext
-#define cpu_do_switch_mm		processor.switch_mm
 
-/* These three are private to arch/arm/kernel/suspend.c */
-#define cpu_do_suspend			processor.do_suspend
-#define cpu_do_resume			processor.do_resume
+extern struct processor processor;
+#define PROC_VTABLE(f)			processor.f
+#define PROC_TABLE(f)			processor.f
+static inline void init_proc_vtable(const struct processor *p)
+{
+	processor = *p;
+}
+
+#define cpu_proc_init			PROC_VTABLE(_proc_init)
+#define cpu_check_bugs			PROC_VTABLE(check_bugs)
+#define cpu_proc_fin			PROC_VTABLE(_proc_fin)
+#define cpu_reset			PROC_VTABLE(reset)
+#define cpu_do_idle			PROC_VTABLE(_do_idle)
+#define cpu_dcache_clean_area		PROC_TABLE(dcache_clean_area)
+#define cpu_set_pte_ext			PROC_TABLE(set_pte_ext)
+#define cpu_do_switch_mm		PROC_VTABLE(switch_mm)
+
+/* These two are private to arch/arm/kernel/suspend.c */
+#define cpu_do_suspend			PROC_VTABLE(do_suspend)
+#define cpu_do_resume			PROC_VTABLE(do_resume)
 #endif
 
 extern void cpu_resume(void);

arch/arm/kernel/setup.c

@@ -693,9 +693,7 @@ static void __init setup_processor(void)
 	cpu_name = list->cpu_name;
 	__cpu_architecture = __get_cpu_architecture();
 
-#ifdef MULTI_CPU
-	processor = *list->proc;
-#endif
+	init_proc_vtable(list->proc);
 #ifdef MULTI_TLB
 	cpu_tlb = *list->tlb;
 #endif