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Subject[PATCH v2 1/5] mm, fs: Move randomize_stack_top from fs to mm
Date
This preparatory commit moves this function so that further introduction
of generic topdown mmap layout is contained only in mm/util.c.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
fs/binfmt_elf.c | 20 --------------------
include/linux/mm.h | 2 ++
mm/util.c | 22 ++++++++++++++++++++++
3 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 7d09d125f148..045f3b29d264 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -662,26 +662,6 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
* libraries. There is no binary dependent code anywhere else.
*/

-#ifndef STACK_RND_MASK
-#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
-#endif
-
-static 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
-}
-
static int load_elf_binary(struct linux_binprm *bprm)
{
struct file *interpreter = NULL; /* to shut gcc up */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 76769749b5a5..087824a5059f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2312,6 +2312,8 @@ extern int install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long flags, struct page **pages);

+unsigned long randomize_stack_top(unsigned long stack_top);
+
extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);

extern unsigned long mmap_region(struct file *file, unsigned long addr,
diff --git a/mm/util.c b/mm/util.c
index d559bde497a9..a54afb9b4faa 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -14,6 +14,8 @@
#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>

@@ -291,6 +293,26 @@ 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)
{
--
2.20.1
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