ARM: add __arm_iomem_set_ro() to write-protect ioremapped area

__arm_iomem_set_ro() marks an ioremapped area read-only. This is
intended for use with __arm_ioremap_exec() to allow the kernel to
write some code into e.g. SRAM and then write-protect it so the
kernel doesn't complain about W+X mappings.
Tested-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/include/asm/io.h

@@ -138,6 +138,7 @@ extern void __iomem *__arm_ioremap_caller(phys_addr_t, size_t, unsigned int,
 	void *);
 extern void __iomem *__arm_ioremap_pfn(unsigned long, unsigned long, size_t, unsigned int);
 extern void __iomem *__arm_ioremap_exec(phys_addr_t, size_t, bool cached);
+void __arm_iomem_set_ro(void __iomem *ptr, size_t size);
 extern void __iounmap(volatile void __iomem *addr);
 
 extern void __iomem * (*arch_ioremap_caller)(phys_addr_t, size_t,

arch/arm/mm/ioremap.c

@@ -36,6 +36,7 @@
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
+#include <asm/set_memory.h>
 #include <asm/system_info.h>
 
 #include <asm/mach/map.h>
@@ -401,6 +402,11 @@ __arm_ioremap_exec(phys_addr_t phys_addr, size_t size, bool cached)
 			__builtin_return_address(0));
 }
 
+void __arm_iomem_set_ro(void __iomem *ptr, size_t size)
+{
+	set_memory_ro((unsigned long)ptr, PAGE_ALIGN(size) / PAGE_SIZE);
+}
+
 void *arch_memremap_wb(phys_addr_t phys_addr, size_t size)
 {
 	return (__force void *)arch_ioremap_caller(phys_addr, size,