From eb8cdec4a984fde123a91250dcc9e0bddf5eafdc Mon Sep 17 00:00:00 2001 From: Bernd Schmidt Date: Mon, 21 Sep 2009 17:03:57 -0700 Subject: 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 Signed-off-by: Bryan Wu Signed-off-by: Mike Frysinger Acked-by: David Howells Acked-by: Greg Ungerer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/nommu.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'mm/nommu.c') 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 #include #include +#include #include "internal.h" static inline __attribute__((format(printf, 1, 2))) @@ -622,6 +623,22 @@ static void put_nommu_region(struct vm_region *region) __put_nommu_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); +#endif +} + /* * 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 @@ -641,6 +658,8 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma) mm->map_count++; 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); + mm->map_count--; if (mm->mmap_cache == vma) mm->mmap_cache = NULL; -- cgit v1.2.3-59-g8ed1b