[tip:x86/mm] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>

[tip-bot for Kirill A. Shutemov]

Commit-ID:  d691a3cf8004784303f0a4c1c036edfaa7d64d0b
Gitweb:     http://git.kernel.org/tip/d691a3cf8004784303f0a4c1c036edfaa7d64d0b
Author:     Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 17 Mar 2017 21:55:13 +0300
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 27 Mar 2017 08:56:41 +0200

x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>

With folded p4d, pgd_clear() is a nop. Change clear_pgds() to use
p4d_clear() instead.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/20170317185515.8636-5-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/mm/kasan_init_64.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 8d63d7a..7b81f01 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -32,8 +32,19 @@ static int __init map_range(struct range *range)
 static void __init clear_pgds(unsigned long start,
 			unsigned long end)
 {
-	for (; start < end; start += PGDIR_SIZE)
-		pgd_clear(pgd_offset_k(start));
+	pgd_t *pgd;
+
+	for (; start < end; start += PGDIR_SIZE) {
+		pgd = pgd_offset_k(start);
+		/*
+		 * With folded p4d, pgd_clear() is nop, use p4d_clear()
+		 * instead.
+		 */
+		if (CONFIG_PGTABLE_LEVELS < 5)
+			p4d_clear(p4d_offset(pgd, start));
+		else
+			pgd_clear(pgd);
+	}
 }
 
 static void __init kasan_map_early_shadow(pgd_t *pgd)