[RFC PATCH 30/34] mm/pgtable: disallow calling folded (pgd|p4d|pud)_page, pgd_page_vaddr() and (p4d|pud)_pgtable

[Yeoreum Yun]

From: "David Hildenbrand (Arm)" <david at kernel.org>

These helpers that silently fallback to the folded level
are dangerous, especially with some upcoming changes.

We made all code compile-out any calls to these helpers. So let's make the
compiler complain if these helpers are abused in wrong context.

Signed-off-by: David Hildenbrand (Arm) <david at kernel.org>
Signed-off-by: Yeoreum Yun <yeoreum.yun at arm.com>
---
 include/asm-generic/pgtable-nop4d.h | 4 ++--
 include/asm-generic/pgtable-nopmd.h | 4 ++--
 include/asm-generic/pgtable-nopud.h | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/asm-generic/pgtable-nop4d.h b/include/asm-generic/pgtable-nop4d.h
index 0f3b56deaa165..25c26a587b512 100644
--- a/include/asm-generic/pgtable-nop4d.h
+++ b/include/asm-generic/pgtable-nop4d.h
@@ -46,8 +46,8 @@ static inline p4d_t *p4d_offset_lockless(pgd_t *pgdp, pgd_t pgd,
 #define p4d_val(x)				(pgd_val((x).pgd))
 #define __p4d(x)				((p4d_t) { __pgd(x) })
 
-#define pgd_page(pgd)				(p4d_page((p4d_t){ pgd }))
-#define pgd_page_vaddr(pgd)			((unsigned long)(p4d_pgtable((p4d_t){ pgd })))
+#define pgd_page(pgd)				({ BUILD_BUG(); (struct page *)NULL; })
+#define pgd_page_vaddr(pgd)			({ BUILD_BUG(); 0UL; })
 
 /*
  * allocating and freeing a p4d is trivial: the 1-entry p4d is
diff --git a/include/asm-generic/pgtable-nopmd.h b/include/asm-generic/pgtable-nopmd.h
index 9d854211a55a5..75650fa9111cd 100644
--- a/include/asm-generic/pgtable-nopmd.h
+++ b/include/asm-generic/pgtable-nopmd.h
@@ -56,8 +56,8 @@ static inline pmd_t *pmd_offset_lockless(pud_t *pudp, pud_t pud,
 #define pmd_val(x)				(pud_val((x).pud))
 #define __pmd(x)				((pmd_t) { __pud(x) } )
 
-#define pud_page(pud)				(pmd_page((pmd_t){ pud }))
-#define pud_pgtable(pud)			((pmd_t *)(pmd_page_vaddr((pmd_t){ pud })))
+#define pud_page(pud)				({ BUILD_BUG(); (struct page *)NULL; })
+#define pud_pgtable(pud)			({ BUILD_BUG(); NULL; })
 
 /*
  * allocating and freeing a pmd is trivial: the 1-entry pmd is
diff --git a/include/asm-generic/pgtable-nopud.h b/include/asm-generic/pgtable-nopud.h
index aa8a6ce139e47..b592fff18887a 100644
--- a/include/asm-generic/pgtable-nopud.h
+++ b/include/asm-generic/pgtable-nopud.h
@@ -54,8 +54,8 @@ static inline pud_t *pud_offset_lockless(p4d_t *p4dp, p4d_t p4d,
 #define pud_val(x)				(p4d_val((x).p4d))
 #define __pud(x)				((pud_t) { __p4d(x) })
 
-#define p4d_page(p4d)				(pud_page((pud_t){ p4d }))
-#define p4d_pgtable(p4d)			((pud_t *)(pud_pgtable((pud_t){ p4d })))
+#define p4d_page(p4d)				({ BUILD_BUG(); (struct page *)NULL; })
+#define p4d_pgtable(p4d)			({ BUILD_BUG(); NULL; })
 
 /*
  * allocating and freeing a pud is trivial: the 1-entry pud is
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}