[SPARC64]: Randomize mm->mmap_base when PF_RANDOMIZE is set.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/sys_sparc.c

@@ -25,6 +25,7 @@
 #include <linux/syscalls.h>
 #include <linux/ipc.h>
 #include <linux/personality.h>
+#include <linux/random.h>
 
 #include <asm/uaccess.h>
 #include <asm/ipc.h>
@@ -358,6 +359,17 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u
 /* Essentially the same as PowerPC... */
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
+	unsigned long random_factor = 0UL;
+
+	if (current->flags & PF_RANDOMIZE) {
+		random_factor = get_random_int();
+		if (test_thread_flag(TIF_32BIT))
+			random_factor &= ((1 * 1024 * 1024) - 1);
+		else
+			random_factor = ((random_factor << PAGE_SHIFT) &
+					 0xffffffffUL);
+	}
+
 	/*
 	 * Fall back to the standard layout if the personality
 	 * bit is set, or if the expected stack growth is unlimited:
@@ -366,7 +378,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 	    (current->personality & ADDR_COMPAT_LAYOUT) ||
 	    current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY ||
 	    sysctl_legacy_va_layout) {
-		mm->mmap_base = TASK_UNMAPPED_BASE;
+		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 		mm->get_unmapped_area = arch_get_unmapped_area;
 		mm->unmap_area = arch_unmap_area;
 	} else {
@@ -380,7 +392,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 		if (gap > (task_size / 6 * 5))
 			gap = (task_size / 6 * 5);
 
-		mm->mmap_base = task_size - (gap & PAGE_MASK);
+		mm->mmap_base = PAGE_ALIGN(task_size - gap - random_factor);
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 		mm->unmap_area = arch_unmap_area_topdown;
 	}