[PATCH V3 11/30] mm/mmap: Drop protection_map[]

Anshuman Khandual
2022-02-28T10:50:53Z

There are no other users for protection_map[]. Hence just drop this array
construct and instead define __vm_get_page_prot() which will provide page
protection map based on vm_flags combination switch.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
drivers/gpu/drm/drm_vm.c | 4 +--
include/linux/mm.h | 6 ----
mm/mmap.c | 63 ++++++++++++++++++++++++++--------------
3 files changed, 44 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index e957d4851dc0..14862df7532f 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -482,7 +482,7 @@ static int drm_mmap_dma(struct file *filp, struct vm_area_struct *vma)
#else
/* Ye gads this is ugly. With more thought
we could move this up higher and use
- `protection_map' instead. */
+ `vm_get_page_prot()' instead. */
vma->vm_page_prot =
__pgprot(pte_val
(pte_wrprotect
@@ -566,7 +566,7 @@ static int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
#else
/* Ye gads this is ugly. With more thought
we could move this up higher and use
- `protection_map' instead. */
+ `vm_get_page_prot()' instead. */
vma->vm_page_prot =
__pgprot(pte_val
(pte_wrprotect
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 213cc569b192..ff74bd2d7850 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -418,12 +418,6 @@ extern unsigned int kobjsize(const void *objp);
#endif
#define VM_FLAGS_CLEAR (ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR)

-/*
- * mapping from the currently active vm_flags protection bits (the
- * low four bits) to a page protection mask..
- */
-extern pgprot_t protection_map[16];
-
/*
* The default fault flags that should be used by most of the
* arch-specific page fault handlers.
diff --git a/mm/mmap.c b/mm/mmap.c
index f2310f6e7466..78eeac277a80 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -102,24 +102,6 @@ static void unmap_region(struct mm_struct *mm,
* w: (no) no
* x: (yes) yes
*/
-pgprot_t protection_map[16] __ro_after_init = {
- [VM_NONE] = __P000,
- [VM_READ] = __P001,
- [VM_WRITE] = __P010,
- [VM_WRITE | VM_READ] = __P011,
- [VM_EXEC] = __P100,
- [VM_EXEC | VM_READ] = __P101,
- [VM_EXEC | VM_WRITE] = __P110,
- [VM_EXEC | VM_WRITE | VM_READ] = __P111,
- [VM_SHARED] = __S000,
- [VM_SHARED | VM_READ] = __S001,
- [VM_SHARED | VM_WRITE] = __S010,
- [VM_SHARED | VM_WRITE | VM_READ] = __S011,
- [VM_SHARED | VM_EXEC] = __S100,
- [VM_SHARED | VM_EXEC | VM_READ] = __S101,
- [VM_SHARED | VM_EXEC | VM_WRITE] = __S110,
- [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = __S111
-};

#ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
@@ -128,10 +110,49 @@ static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
}
#endif

+static inline pgprot_t __vm_get_page_prot(unsigned long vm_flags)
+{
+ switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
+ case VM_NONE:
+ return __P000;
+ case VM_READ:
+ return __P001;
+ case VM_WRITE:
+ return __P010;
+ case VM_READ | VM_WRITE:
+ return __P011;
+ case VM_EXEC:
+ return __P100;
+ case VM_EXEC | VM_READ:
+ return __P101;
+ case VM_EXEC | VM_WRITE:
+ return __P110;
+ case VM_EXEC | VM_READ | VM_WRITE:
+ return __P111;
+ case VM_SHARED:
+ return __S000;
+ case VM_SHARED | VM_READ:
+ return __S001;
+ case VM_SHARED | VM_WRITE:
+ return __S010;
+ case VM_SHARED | VM_READ | VM_WRITE:
+ return __S011;
+ case VM_SHARED | VM_EXEC:
+ return __S100;
+ case VM_SHARED | VM_EXEC | VM_READ:
+ return __S101;
+ case VM_SHARED | VM_EXEC | VM_WRITE:
+ return __S110;
+ case VM_SHARED | VM_EXEC | VM_READ | VM_WRITE:
+ return __S111;
+ default:
+ BUILD_BUG();
+ }
+}
+
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
- pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
- (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
+ pgprot_t ret = __pgprot(pgprot_val(__vm_get_page_prot(vm_flags)) |
pgprot_val(arch_vm_get_page_prot(vm_flags)));

return arch_filter_pgprot(ret);
@@ -1684,7 +1705,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
/*
* Some shared mappings will want the pages marked read-only
* to track write events. If so, we'll downgrade vm_page_prot
- * to the private version (using protection_map[] without the
+ * to the private version (using vm_get_page_prot() without the
* VM_SHARED bit).
*/
int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
--
2.25.1