[PATCH V6 02/26] mm/mmap: Define DECLARE_VM_GET_PAGE_PROT

Anshuman Khandual
2022-06-30T05:17:23Z

This just converts the generic vm_get_page_prot() implementation into a new
macro i.e DECLARE_VM_GET_PAGE_PROT which later can be used across platforms
when enabling them with ARCH_HAS_VM_GET_PAGE_PROT. This does not create any
functional change.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
include/linux/pgtable.h | 28 ++++++++++++++++++++++++++++
mm/mmap.c | 26 +-------------------------
2 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 3cdc16cfd867..014ee8f0fbaa 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1689,4 +1689,32 @@ typedef unsigned int pgtbl_mod_mask;
#define MAX_PTRS_PER_P4D PTRS_PER_P4D
#endif

+/* description of effects of mapping type and prot in current implementation.
+ * this is due to the limited x86 page protection hardware. The expected
+ * behavior is in parens:
+ *
+ * map_type prot
+ * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC
+ * MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes
+ * w: (no) no w: (no) no w: (yes) yes w: (no) no
+ * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
+ *
+ * MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes
+ * w: (no) no w: (no) no w: (copy) copy w: (no) no
+ * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
+ *
+ * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
+ * MAP_PRIVATE (with Enhanced PAN supported):
+ * r: (no) no
+ * w: (no) no
+ * x: (yes) yes
+ */
+#define DECLARE_VM_GET_PAGE_PROT \
+pgprot_t vm_get_page_prot(unsigned long vm_flags) \
+{ \
+ return protection_map[vm_flags & \
+ (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)]; \
+} \
+EXPORT_SYMBOL(vm_get_page_prot);
+
#endif /* _LINUX_PGTABLE_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index b01f0280bda2..b46d5e931bb3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -81,26 +81,6 @@ static void unmap_region(struct mm_struct *mm,
struct vm_area_struct *vma, struct vm_area_struct *prev,
unsigned long start, unsigned long end);

-/* description of effects of mapping type and prot in current implementation.
- * this is due to the limited x86 page protection hardware. The expected
- * behavior is in parens:
- *
- * map_type prot
- * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC
- * MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes
- * w: (no) no w: (no) no w: (yes) yes w: (no) no
- * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
- *
- * MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes
- * w: (no) no w: (no) no w: (copy) copy w: (no) no
- * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
- *
- * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
- * MAP_PRIVATE (with Enhanced PAN supported):
- * r: (no) no
- * w: (no) no
- * x: (yes) yes
- */
#ifdef __P000
pgprot_t protection_map[16] __ro_after_init = {
[VM_NONE] = __P000,
@@ -123,11 +103,7 @@ pgprot_t protection_map[16] __ro_after_init = {
#endif

#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
-pgprot_t vm_get_page_prot(unsigned long vm_flags)
-{
- return protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
-}
-EXPORT_SYMBOL(vm_get_page_prot);
+DECLARE_VM_GET_PAGE_PROT
#endif /* CONFIG_ARCH_HAS_VM_GET_PAGE_PROT */

static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
--
2.25.1