powerpc: Randomise mmap start address

[linux-2.6-omap-h63xx.git] / arch / powerpc / mm / mmap.c

diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index 8ff5757af0d74fb74268db13026ec1c9d57138e7..f7376dbb653b6bda6b5bab6c927d486a013ba350 100644 (file)
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -24,6 +24,7 @@
 
 #include <linux/personality.h>
 #include <linux/mm.h>
+#include <linux/random.h>
 #include <linux/sched.h>
 
 /*
@@ -45,6 +46,20 @@ static inline int mmap_is_legacy(void)
        return sysctl_legacy_va_layout;
 }
 
+static unsigned long mmap_rnd(void)
+{
+       unsigned long rnd = 0;
+
+       if (current->flags & PF_RANDOMIZE) {
+               /* 8MB for 32bit, 1GB for 64bit */
+               if (is_32bit_task())
+                       rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
+               else
+                       rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
+       }
+       return rnd << PAGE_SHIFT;
+}
+
 static inline unsigned long mmap_base(void)
 {
        unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
@@ -54,7 +69,7 @@ static inline unsigned long mmap_base(void)
        else if (gap > MAX_GAP)
                gap = MAX_GAP;
 
-       return TASK_SIZE - (gap & PAGE_MASK);
+       return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
 }
 
 /*