[PATCH v9 5/7] poweprc: mm: Implement *_user_accessible_page() for ptes

[Rohan McLure]

Page table checking depends on architectures providing an
implementation of p{te,md,ud}_user_accessible_page. With
refactorisations made on powerpc/mm, the pte_access_permitted() and
similar methods verify whether a userland page is accessible with the
required permissions.

Since page table checking is the only user of
p{te,md,ud}_user_accessible_page(), implement these for all platforms,
using some of the same preliminay checks taken by pte_access_permitted()
on that platform.

Since Commit 8e9bd41e4ce1 ("powerpc/nohash: Replace pte_user() by pte_read()")
pte_user() is no longer required to be present on all platforms as it
may be equivalent to or implied by pte_read(). Hence implementations are
specialised.

Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
---
v9: New implementation
---
 arch/powerpc/include/asm/book3s/32/pgtable.h |  5 +++++
 arch/powerpc/include/asm/book3s/64/pgtable.h |  5 +++++
 arch/powerpc/include/asm/nohash/pgtable.h    |  5 +++++
 arch/powerpc/include/asm/pgtable.h           | 15 +++++++++++++++
 4 files changed, 30 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 9cc95a61d2a6..bd6f8cdd25aa 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -441,6 +441,11 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	return true;
 }
 
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+	return pte_present(pte) && pte_read(pte);
+}
+
 /* Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  *
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 2454174b26cb..dd3e7b190ab7 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -544,6 +544,11 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	return arch_pte_access_permitted(pte_val(pte), write, 0);
 }
 
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+	return pte_present(pte) && pte_user(pte) && pte_read(pte);
+}
+
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 427db14292c9..33b4a4267f66 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -213,6 +213,11 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	return true;
 }
 
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+	return pte_present(pte) && pte_read(pte);
+}
+
 /* Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  *
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index d7d0f47760d3..661bf3afca37 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -250,6 +250,21 @@ static inline pte_t pud_pte(pud_t pud)
 	return __pte(pud_val(pud));
 }
 #endif
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+	pte_t pte = pmd_pte(pmd);
+
+	return pte_user_accessible_page(pte);
+}
+
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+	pte_t pte = pud_pte(pud);
+
+	return pte_user_accessible_page(pte);
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PGTABLE_H */
-- 
2.43.0