x86/kasan: Extend KASAN to support 5-level paging

This patch bring support for a non-folded additional page table level.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170330080731.65421-7-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/kasan_init_64.c

@@ -55,8 +55,18 @@ static void __init kasan_map_early_shadow(pgd_t *pgd)
 	unsigned long end = KASAN_SHADOW_END;
 
 	for (i = pgd_index(start); start < end; i++) {
-		pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud)
-				| _KERNPG_TABLE);
+		switch (CONFIG_PGTABLE_LEVELS) {
+		case 4:
+			pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud) |
+					_KERNPG_TABLE);
+			break;
+		case 5:
+			pgd[i] = __pgd(__pa_nodebug(kasan_zero_p4d) |
+					_KERNPG_TABLE);
+			break;
+		default:
+			BUILD_BUG();
+		}
 		start += PGDIR_SIZE;
 	}
 }
@@ -84,6 +94,7 @@ void __init kasan_early_init(void)
 	pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
 	pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
 	pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
+	p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
 
 	for (i = 0; i < PTRS_PER_PTE; i++)
 		kasan_zero_pte[i] = __pte(pte_val);
@@ -94,6 +105,9 @@ void __init kasan_early_init(void)
 	for (i = 0; i < PTRS_PER_PUD; i++)
 		kasan_zero_pud[i] = __pud(pud_val);
 
+	for (i = 0; CONFIG_PGTABLE_LEVELS >= 5 && i < PTRS_PER_P4D; i++)
+		kasan_zero_p4d[i] = __p4d(p4d_val);
+
 	kasan_map_early_shadow(early_level4_pgt);
 	kasan_map_early_shadow(init_level4_pgt);
 }