Add API to enable/disable writeprotect a vma range. Unlike mprotect,
this doesn't split/merge vmas.
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
---
include/linux/userfaultfd_k.h | 2 ++
mm/userfaultfd.c | 52 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 4e22d11..44f5b09 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -35,6 +35,8 @@ extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
extern ssize_t mfill_zeropage(struct mm_struct *dst_mm,
unsigned long dst_start,
unsigned long len);
+extern int mwriteprotect_range(struct mm_struct *dst_mm,
+ unsigned long start, unsigned long len, bool enable_wp);
/* mm helpers */
static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 77fee93..3e97e24 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -306,3 +306,55 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
{
return __mcopy_atomic(dst_mm, start, 0, len, true);
}
+
+int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
+ unsigned long len, bool enable_wp)
+{
+ struct vm_area_struct *dst_vma;
+ pgprot_t newprot;
+ int err;
+
+ /*
+ * Sanitize the command parameters:
+ */
+ BUG_ON(start & ~PAGE_MASK);
+ BUG_ON(len & ~PAGE_MASK);
+
+ /* Does the address range wrap, or is the span zero-sized? */
+ BUG_ON(start + len <= start);
+
+ down_read(&dst_mm->mmap_sem);
+
+ /*
+ * Make sure the vma is not shared, that the dst range is
+ * both valid and fully within a single existing vma.
+ */
+ err = -EINVAL;
+ dst_vma = find_vma(dst_mm, start);
+ if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
+ goto out_unlock;
+ if (start < dst_vma->vm_start ||
+ start + len > dst_vma->vm_end)
+ goto out_unlock;
+
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
+ goto out_unlock;
+ if (!userfaultfd_wp(dst_vma))
+ goto out_unlock;
+
+ if (dst_vma->vm_ops)
+ goto out_unlock;
+
+ if (enable_wp)
+ newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
+ else
+ newprot = vm_get_page_prot(dst_vma->vm_flags);
+
+ change_protection(dst_vma, start, start + len, newprot,
+ !enable_wp, 0);
+
+ err = 0;
+out_unlock:
+ up_read(&dst_mm->mmap_sem);
+ return err;
+}
--
2.4.6
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