arm64: mm: add set_memory_valid()

This function validates and invalidates PTE entries, and will be utilized
in kdump to protect loaded crash dump kernel image.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/cacheflush.h

@@ -154,5 +154,6 @@ int set_memory_ro(unsigned long addr, int numpages);
 int set_memory_rw(unsigned long addr, int numpages);
 int set_memory_x(unsigned long addr, int numpages);
 int set_memory_nx(unsigned long addr, int numpages);
+int set_memory_valid(unsigned long addr, unsigned long size, int enable);
 
 #endif

arch/arm64/mm/pageattr.c

@@ -125,20 +125,23 @@ int set_memory_x(unsigned long addr, int numpages)
 }
 EXPORT_SYMBOL_GPL(set_memory_x);
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
-void __kernel_map_pages(struct page *page, int numpages, int enable)
+int set_memory_valid(unsigned long addr, int numpages, int enable)
 {
-	unsigned long addr = (unsigned long) page_address(page);
-
 	if (enable)
-		__change_memory_common(addr, PAGE_SIZE * numpages,
+		return __change_memory_common(addr, PAGE_SIZE * numpages,
 					__pgprot(PTE_VALID),
 					__pgprot(0));
 	else
-		__change_memory_common(addr, PAGE_SIZE * numpages,
+		return __change_memory_common(addr, PAGE_SIZE * numpages,
 					__pgprot(0),
 					__pgprot(PTE_VALID));
 }
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	set_memory_valid((unsigned long)page_address(page), numpages, enable);
+}
 #ifdef CONFIG_HIBERNATION
 /*
  * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function