[RFC PATCH 29/34] mm/pgtable: disallow calling folded set_pgd/set_p4d/set_pud

[Yeoreum Yun]

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

The stubs are documented to "doesn't get actually called", which was
false for a couple of instances.

The helpers are dangerous, especially with some upcoming changes.

We made all code compile-out any calls to set_pgd/set_p4d/set_pud for
folded page tables. 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 | 7 ++-----
 include/asm-generic/pgtable-nopmd.h | 6 +-----
 include/asm-generic/pgtable-nopud.h | 7 ++-----
 3 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/include/asm-generic/pgtable-nop4d.h b/include/asm-generic/pgtable-nop4d.h
index 019c3f074b771..0f3b56deaa165 100644
--- a/include/asm-generic/pgtable-nop4d.h
+++ b/include/asm-generic/pgtable-nop4d.h
@@ -28,11 +28,8 @@ static inline bool pgd_leaf(pgd_t pgd)		{ return false; }
 
 #define pgd_populate(mm, pgd, p4d)		do { } while (0)
 #define pgd_populate_safe(mm, pgd, p4d)		do { } while (0)
-/*
- * (p4ds are folded into pgds so this doesn't get actually called,
- * but the define is needed for a generic inline function.)
- */
-#define set_pgd(pgdptr, pgdval)	set_p4d((p4d_t *)(pgdptr), (p4d_t) { pgdval })
+
+#define set_pgd(pgdptr, pgdval)			BUILD_BUG()
 
 static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)
 {
diff --git a/include/asm-generic/pgtable-nopmd.h b/include/asm-generic/pgtable-nopmd.h
index ae2eff44889ac..9d854211a55a5 100644
--- a/include/asm-generic/pgtable-nopmd.h
+++ b/include/asm-generic/pgtable-nopmd.h
@@ -38,11 +38,7 @@ static inline void pud_clear(pud_t *pud)	{ }
 
 #define pud_populate(mm, pmd, pte)		do { } while (0)
 
-/*
- * (pmds are folded into puds so this doesn't get actually called,
- * but the define is needed for a generic inline function.)
- */
-#define set_pud(pudptr, pudval)			set_pmd((pmd_t *)(pudptr), (pmd_t) { pudval })
+#define set_pud(pudptr, pudval)			BUILD_BUG()
 
 static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address)
 {
diff --git a/include/asm-generic/pgtable-nopud.h b/include/asm-generic/pgtable-nopud.h
index 5a2b0a81ae197..aa8a6ce139e47 100644
--- a/include/asm-generic/pgtable-nopud.h
+++ b/include/asm-generic/pgtable-nopud.h
@@ -35,11 +35,8 @@ static inline bool p4d_leaf(p4d_t p4d)		{ return false; }
 
 #define p4d_populate(mm, p4d, pud)		do { } while (0)
 #define p4d_populate_safe(mm, p4d, pud)		do { } while (0)
-/*
- * (puds are folded into p4ds so this doesn't get actually called,
- * but the define is needed for a generic inline function.)
- */
-#define set_p4d(p4dptr, p4dval)	set_pud((pud_t *)(p4dptr), (pud_t) { p4dval })
+
+#define set_p4d(p4dptr, p4dval)			BUILD_BUG()
 
 static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
 {
-- 
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