===================================================================
@@ -24,6 +24,7 @@
#include <linux/personality.h>
#include <linux/mm.h>
+#include <linux/random.h>
#include <linux/sched.h>
/*
@@ -45,6 +46,20 @@
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 @@
else if (gap > MAX_GAP)
gap = MAX_GAP;
- return TASK_SIZE - (gap & PAGE_MASK);
+ return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
}
/*
Randomise mmap start address - 8MB on 32bit and 1GB on 64bit tasks. Until ppc32 uses the mmap.c functionality, this is ppc64 specific. Before: # ./test & cat /proc/${!}/maps|tail -2|head -1 f75fe000-f7fff000 rw-p f75fe000 00:00 0 f75fe000-f7fff000 rw-p f75fe000 00:00 0 f75fe000-f7fff000 rw-p f75fe000 00:00 0 f75fe000-f7fff000 rw-p f75fe000 00:00 0 f75fe000-f7fff000 rw-p f75fe000 00:00 0 After: # ./test & cat /proc/${!}/maps|tail -2|head -1 f718b000-f7b8c000 rw-p f718b000 00:00 0 f7551000-f7f52000 rw-p f7551000 00:00 0 f6ee7000-f78e8000 rw-p f6ee7000 00:00 0 f74d4000-f7ed5000 rw-p f74d4000 00:00 0 f6e9d000-f789e000 rw-p f6e9d000 00:00 0 Similar for 64bit, but with 1GB of scatter: # ./test & cat /proc/${!}/maps|tail -2|head -1 fffb97b5000-fffb97b6000 rw-p fffb97b5000 00:00 0 fffce9a3000-fffce9a4000 rw-p fffce9a3000 00:00 0 fffeaaf2000-fffeaaf3000 rw-p fffeaaf2000 00:00 0 fffd88ac000-fffd88ad000 rw-p fffd88ac000 00:00 0 fffbc62e000-fffbc62f000 rw-p fffbc62e000 00:00 0 Signed-off-by: Anton Blanchard <anton@samba.org> ---