arm64/mm: fold check for KFENCE into can_set_direct_map()

KFENCE requires linear map to be mapped at page granularity, so that it
is possible to protect/unprotect single pages, just like with
rodata_full and DEBUG_PAGEALLOC.

Instead of repating

	can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)

make can_set_direct_map() handle the KFENCE case.

This also prevents potential false positives in kernel_page_present()
that may return true for non-present page if CONFIG_KFENCE is enabled.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220921074841.382615-1-rppt@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/mmu.c

@@ -535,7 +535,7 @@ static void __init map_mem(pgd_t *pgdp)
 	 */
 	BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end));
 
-	if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
+	if (can_set_direct_map())
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	/*
@@ -1542,11 +1542,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
 
 	VM_BUG_ON(!mhp_range_allowed(start, size, true));
 
-	/*
-	 * KFENCE requires linear map to be mapped at page granularity, so that
-	 * it is possible to protect/unprotect single pages in the KFENCE pool.
-	 */
-	if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
+	if (can_set_direct_map())
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	__create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),

arch/arm64/mm/pageattr.c

@@ -21,7 +21,13 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED
 
 bool can_set_direct_map(void)
 {
-	return rodata_full || debug_pagealloc_enabled();
+	/*
+	 * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be
+	 * mapped at page granularity, so that it is possible to
+	 * protect/unprotect single pages.
+	 */
+	return rodata_full || debug_pagealloc_enabled() ||
+		IS_ENABLED(CONFIG_KFENCE);
 }
 
 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)