mm, fs: move randomize_stack_top from fs to mm

[linux-2.6-block.git] / mm / util.c

diff --git a/mm/util.c b/mm/util.c
index 37f7b6711514c7bc25fca683cd86f13fc6310b0f..bf8af5e07c4a24e26ecc0fae785fe24255b8a494 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -16,6 +16,8 @@
 #include <linux/hugetlb.h>
 #include <linux/vmalloc.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/elf.h>
+#include <linux/random.h>
 
 #include <linux/uaccess.h>
 
@@ -293,6 +295,26 @@ int vma_is_stack_for_current(struct vm_area_struct *vma)
        return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 }
 
+#ifndef STACK_RND_MASK
+#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))     /* 8MB of VA */
+#endif
+
+unsigned long randomize_stack_top(unsigned long stack_top)
+{
+       unsigned long random_variable = 0;
+
+       if (current->flags & PF_RANDOMIZE) {
+               random_variable = get_random_long();
+               random_variable &= STACK_RND_MASK;
+               random_variable <<= PAGE_SHIFT;
+       }
+#ifdef CONFIG_STACK_GROWSUP
+       return PAGE_ALIGN(stack_top) + random_variable;
+#else
+       return PAGE_ALIGN(stack_top) - random_variable;
+#endif
+}
+
 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 {