drm: add flag for mapping PCI DMA buffers read-only.

Add DRM_PCI_BUFFER_RO flag for mapping PCI DMA buffer read-only. An additional
flag is needed, since PCI DMA buffers do not have an associated map.

Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/char/drm/drm_vm.c b/drivers/char/drm/drm_vm.c
index b40ae438f531..74686e9a2d34 100644
--- a/drivers/char/drm/drm_vm.c
+++ b/drivers/char/drm/drm_vm.c
@@ -473,6 +473,22 @@ static int drm_mmap_dma(struct file *filp, struct vm_area_struct *vma)
         }
         unlock_kernel();
 
+        if (!capable(CAP_SYS_ADMIN) &&
+            (dma->flags & _DRM_DMA_USE_PCI_RO)) {
+                vma->vm_flags &= ~(VM_WRITE | VM_MAYWRITE);
+#if defined(__i386__) || defined(__x86_64__)
+                pgprot_val(vma->vm_page_prot) &= ~_PAGE_RW;
+#else
+                /* Ye gads this is ugly.  With more thought
+                   we could move this up higher and use
+                   `protection_map' instead.  */
+                vma->vm_page_prot =
+                    __pgprot(pte_val
+                             (pte_wrprotect
+                              (__pte(pgprot_val(vma->vm_page_prot)))));
+#endif
+        }
+
         vma->vm_ops = &drm_vm_dma_ops;
 
         vma->vm_flags |= VM_RESERVED;   /* Don't swap */