path: root/mm
diff options
authorBernd Schmidt <bernds_cb1@t-online.de>2009-09-21 17:03:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:43 -0700
commiteb8cdec4a984fde123a91250dcc9e0bddf5eafdc (patch)
tree9f97b5949e6e63ae947363149b62ed224dad5ab9 /mm
parentpcmcia: cleanup/fixup patch for sa1100_jornada_pcmcia driver (diff)
nommu: add support for Memory Protection Units (MPU)
Some architectures (like the Blackfin arch) implement some of the "simpler" features that one would expect out of a MMU such as memory protection. In our case, we actually get read/write/exec protection down to the page boundary so processes can't stomp on each other let alone the kernel. There is a performance decrease (which depends greatly on the workload) however as the hardware/software interaction was not optimized at design time. Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> Signed-off-by: Bryan Wu <cooloney@kernel.org> Signed-off-by: Mike Frysinger <vapier@gentoo.org> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Greg Ungerer <gerg@snapgear.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 21 insertions, 0 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index 2d02ca17ce18..1a4473faac48 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -33,6 +33,7 @@
#include <asm/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
+#include <asm/mmu_context.h>
#include "internal.h"
static inline __attribute__((format(printf, 1, 2)))
@@ -623,6 +624,22 @@ static void put_nommu_region(struct vm_region *region)
+ * update protection on a vma
+ */
+static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
+#ifdef CONFIG_MPU
+ struct mm_struct *mm = vma->vm_mm;
+ long start = vma->vm_start & PAGE_MASK;
+ while (start < vma->vm_end) {
+ protect_page(mm, start, flags);
+ start += PAGE_SIZE;
+ }
+ update_protections(mm);
* add a VMA into a process's mm_struct in the appropriate place in the list
* and tree and add to the address space's page tree also if not an anonymous
* page
@@ -641,6 +658,8 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
vma->vm_mm = mm;
+ protect_vma(vma, vma->vm_flags);
/* add the VMA to the mapping */
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
@@ -703,6 +722,8 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
kenter("%p", vma);
+ protect_vma(vma, 0);
if (mm->mmap_cache == vma)
mm->mmap_cache = NULL;