From 9887a1fcddef1386d3387edf6497d08670460edb Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Wed, 12 Jan 2011 09:55:28 +0100
Subject: [PATCH] [S390] Randomize lower bits of stack address

Randomize the lower bits of the stack address like x86 and powerpc.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 arch/s390/include/asm/system.h | 2 +-
 arch/s390/kernel/process.c     | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/system.h b/arch/s390/include/asm/system.h
index 6710b0eac165..8f8d759f6a7b 100644
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -449,7 +449,7 @@ extern void (*_machine_restart)(char *command);
 extern void (*_machine_halt)(void);
 extern void (*_machine_power_off)(void);
 
-#define arch_align_stack(x) (x)
+extern unsigned long arch_align_stack(unsigned long sp);
 
 static inline int tprot(unsigned long addr)
 {
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 6ba42222b542..38ff69e562c8 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -30,9 +30,11 @@
 #include <linux/tick.h>
 #include <linux/elfcore.h>
 #include <linux/kernel_stat.h>
+#include <linux/personality.h>
 #include <linux/syscalls.h>
 #include <linux/compat.h>
 #include <linux/kprobes.h>
+#include <linux/random.h>
 #include <asm/compat.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -332,3 +334,10 @@ unsigned long get_wchan(struct task_struct *p)
 	}
 	return 0;
 }
+
+unsigned long arch_align_stack(unsigned long sp)
+{
+	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+		sp -= get_random_int() & ~PAGE_MASK;
+	return sp & ~0xf;
+}
-- 
2.11.0