From dd4ac4b05883dbdf5573976ce9bbdaffaf978afd Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton@samba.org>
Date: Sun, 22 Feb 2009 01:50:05 +0000
Subject: [PATCH] --- yaml --- r: 138495 b: refs/heads/master c:
 a5adc91a4b44b5d1706b9d906cc14fe4f312afe9 h: refs/heads/master i:   138493:
 02313e775214657138c768117cbd3fde1f5e430d   138491:
 3e906035cc7295812516c3d5de516786cd839e68   138487:
 4d127648ea01e2ef2e6070661b89fb8389d27f17   138479:
 761cdf78c7cb2bca76ba70949d639f0f1954bfb7   138463:
 a5c8210cc921f06b2fed04db79d694cce9a138a1   138431:
 c3df475b850636a833f3e0a10917c251c0a64d60   138367:
 b6cfeed8699a546ea9f43cd2acb3899f52ee5c10   138239:
 d81b1198dfc83d73aa2885c4043bb341e4d4b586 v: v3

---
 [refs]                       |  2 +-
 trunk/arch/powerpc/mm/mmap.c | 14 +++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index 57f5853bc2e3..2511f4e806e8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 912f9ee21c836081e3c96dfe61025841ebeb95da
+refs/heads/master: a5adc91a4b44b5d1706b9d906cc14fe4f312afe9
diff --git a/trunk/arch/powerpc/mm/mmap.c b/trunk/arch/powerpc/mm/mmap.c
index f7376dbb653b..75dc7faaf917 100644
--- a/trunk/arch/powerpc/mm/mmap.c
+++ b/trunk/arch/powerpc/mm/mmap.c
@@ -46,6 +46,14 @@ static inline int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
+/*
+ * Since get_random_int() returns the same value within a 1 jiffy window,
+ * we will almost always get the same randomisation for the stack and mmap
+ * region. This will mean the relative distance between stack and mmap will
+ * be the same.
+ *
+ * To avoid this we can shift the randomness by 1 bit.
+ */
 static unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = 0;
@@ -53,11 +61,11 @@ static unsigned long mmap_rnd(void)
 	if (current->flags & PF_RANDOMIZE) {
 		/* 8MB for 32bit, 1GB for 64bit */
 		if (is_32bit_task())
-			rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
+			rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT)));
 		else
-			rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
+			rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT)));
 	}
-	return rnd << PAGE_SHIFT;
+	return (rnd << PAGE_SHIFT) * 2;
 }
 
 static inline unsigned long mmap_base(void)