[PATCH v10 10/12] 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
v10: Let book3s/64 use pte_user(), but otherwise default other platforms
to using the address provided with the call to infer whether it is a
user page or not. pmd/pud variants will warn on all other platforms, as
they should not be used for user page mappings
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 19 ++++++++++++++
 arch/powerpc/include/asm/pgtable.h           | 26 ++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 382724c5e872..ca765331e21d 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -538,6 +538,12 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	return arch_pte_access_permitted(pte_val(pte), write, 0);
 }
 
+#define pte_user_accessible_page pte_user_accessible_page
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && pte_user(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.
@@ -881,6 +887,7 @@ static inline int pud_present(pud_t pud)
 
 extern struct page *pud_page(pud_t pud);
 extern struct page *pmd_page(pmd_t pmd);
+
 static inline pte_t pud_pte(pud_t pud)
 {
 	return __pte_raw(pud_raw(pud));
@@ -926,6 +933,12 @@ static inline bool pud_access_permitted(pud_t pud, bool write)
 	return pte_access_permitted(pud_pte(pud), write);
 }
 
+#define pud_user_accessible_page pud_user_accessible_page
+static inline bool pud_user_accessible_page(pud_t pud, unsigned long addr)
+{
+	return pte_user_accessible_page(pud_pte(pud), addr);
+}
+
 #define __p4d_raw(x)	((p4d_t) { __pgd_raw(x) })
 static inline __be64 p4d_raw(p4d_t x)
 {
@@ -1091,6 +1104,12 @@ static inline bool pmd_access_permitted(pmd_t pmd, bool write)
 	return pte_access_permitted(pmd_pte(pmd), write);
 }
 
+#define pmd_user_accessible_page pmd_user_accessible_page
+static inline bool pmd_user_accessible_page(pmd_t pmd, unsigned long addr)
+{
+	return pte_user_accessible_page(pmd_pte(pmd), addr);
+}
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
 extern pud_t pfn_pud(unsigned long pfn, pgprot_t pgprot);
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 13f661831333..3741a63fb82e 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -227,6 +227,32 @@ static inline int pud_pfn(pud_t pud)
 }
 #endif
 
+#ifndef pte_user_accessible_page
+#define pte_user_accessible_page pte_user_accessible_page
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && !is_kernel_addr(addr);
+}
+#endif
+
+#ifndef pmd_user_accessible_page
+#define pmd_user_accessible_page pmd_user_accessible_page
+static inline bool pmd_user_accessible_page(pmd_t pmd, unsigned long addr)
+{
+	WARN_ONCE(1, "pmd: platform does not use pmd entries directly");
+	return false;
+}
+#endif
+
+#ifndef pud_user_accessible_page
+#define pud_user_accessible_page pud_user_accessible_page
+static inline bool pud_user_accessible_page(pud_t pud, unsigned long addr)
+{
+	WARN_ONCE(1, "pud: platform does not use pud entries directly");
+	return false;
+}
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PGTABLE_H */
-- 
2.44.0