mips: extract logic for mmap_rnd()

In preparation for splitting out ET_DYN ASLR, extract the mmap ASLR selection into a separate function. Signed-off-by: Kees Cook <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Cc: Ralf Baechle <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
needcaffeine · Apr 14, 2015 · 1f0569d · 1f0569d
1 parent dd04cff
commit 1f0569d
Showing 1 changed file with 16 additions and 8 deletions.
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
@@ -142,18 +142,26 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 			addr0, len, pgoff, flags, DOWN);
 }
 
+static unsigned long mmap_rnd(void)
+{
+	unsigned long rnd;
+
+	rnd = (unsigned long)get_random_int();
+	rnd <<= PAGE_SHIFT;
+	if (TASK_IS_32BIT_ADDR)
+		rnd &= 0xfffffful;
+	else
+		rnd &= 0xffffffful;
+
+	return rnd;
+}
+
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
 	unsigned long random_factor = 0UL;
 
-	if (current->flags & PF_RANDOMIZE) {
-		random_factor = get_random_int();
-		random_factor = random_factor << PAGE_SHIFT;
-		if (TASK_IS_32BIT_ADDR)
-			random_factor &= 0xfffffful;
-		else
-			random_factor &= 0xffffffful;
-	}
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = mmap_rnd();
 
 	if (mmap_is_legacy()) {
 		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;