mm: pgtable: add shortcuts for accessing kernel PMD and PTE

The powerpc 32-bit implementation of pgtable has nice shortcuts for
accessing kernel PMD and PTE for a given virtual address.  Make these
helpers available for all architectures.

[[email protected]: microblaze: fix page table traversal in setup_rt_frame()]
  Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: s/pmd_ptr_k/pmd_off_k/ in various powerpc places]

Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Cain <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greentime Hu <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ley Foon Tan <[email protected]>
Cc: Mark Salter <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Nick Hu <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Russell King <[email protected]>
Cc: Stafford Horne <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vincent Chen <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 24 insertions, 0 deletions

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 6e274da637fd..ee85b222d098 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -28,6 +28,30 @@
 #define USER_PGTABLES_CEILING	0UL
 #endif
 
+/*
+ * In many cases it is known that a virtual address is mapped at PMD or PTE
+ * level, so instead of traversing all the page table levels, we can get a
+ * pointer to the PMD entry in user or kernel page table or translate a virtual
+ * address to the pointer in the PTE in the kernel page tables with simple
+ * helpers.
+ */
+static inline pmd_t *pmd_off(struct mm_struct *mm, unsigned long va)
+{
+	return pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, va), va), va), va);
+}
+
+static inline pmd_t *pmd_off_k(unsigned long va)
+{
+	return pmd_offset(pud_offset(p4d_offset(pgd_offset_k(va), va), va), va);
+}
+
+static inline pte_t *virt_to_kpte(unsigned long vaddr)
+{
+	pmd_t *pmd = pmd_off_k(vaddr);
+
+	return pmd_none(*pmd) ? NULL : pte_offset_kernel(pmd, vaddr);
+}
+
 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
 extern int ptep_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pte_t *ptep,