From df1ca53cba34b1d40a4ed47907d71397e4ee72c2 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Wed, 12 Jan 2011 09:55:27 +0100
Subject: [PATCH] [S390] Randomize mmap start address

Randomize mmap start address with 8MB.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 arch/s390/mm/mmap.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 74d663f367e2..c9a9f7f18188 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -27,6 +27,7 @@
 #include <linux/personality.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/random.h>
 #include <asm/pgalloc.h>
 #include <asm/compat.h>
 
@@ -56,6 +57,14 @@ static inline int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
+static unsigned long mmap_rnd(void)
+{
+	if (!(current->flags & PF_RANDOMIZE))
+		return 0;
+	/* 8MB randomization for mmap_base */
+	return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
+}
+
 static inline unsigned long mmap_base(void)
 {
 	unsigned long gap = rlimit(RLIMIT_STACK);
@@ -64,8 +73,8 @@ static inline unsigned long mmap_base(void)
 		gap = MIN_GAP;
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
-
-	return STACK_TOP - stack_maxrandom_size() - (gap & PAGE_MASK);
+	gap &= PAGE_MASK;
+	return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
 }
 
 #ifndef CONFIG_64BIT