+ powerpc-mm-implement-_user_accessible_page-for-ptes.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: powerpc: mm: implement *_user_accessible_page() for ptes
has been added to the -mm mm-new branch.  Its filename is
     powerpc-mm-implement-_user_accessible_page-for-ptes.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/powerpc-mm-implement-_user_accessible_page-for-ptes.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Rohan McLure <rmclure@linux.ibm.com>
Subject: powerpc: mm: implement *_user_accessible_page() for ptes
Date: Wed, 13 Aug 2025 16:26:12 +1000

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 preliminary 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 of pte_user_accessible_page() are specialised.

[ajd@linux.ibm.com: rebase and fix commit message]
Link: https://lkml.kernel.org/r/20250813062614.51759-12-ajd@linux.ibm.com
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Nicholas Miehlbradt <nicholas@linux.ibm.com>
Cc: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/powerpc/include/asm/book3s/32/pgtable.h |    5 +++++
 arch/powerpc/include/asm/book3s/64/pgtable.h |   17 +++++++++++++++++
 arch/powerpc/include/asm/nohash/pgtable.h    |    5 +++++
 arch/powerpc/include/asm/pgtable.h           |    8 ++++++++
 4 files changed, 35 insertions(+)

--- a/arch/powerpc/include/asm/book3s/32/pgtable.h~powerpc-mm-implement-_user_accessible_page-for-ptes
+++ a/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -437,6 +437,11 @@ static inline bool pte_access_permitted(
 	return true;
 }
 
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && !is_kernel_addr(addr);
+}
+
 /* Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  *
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h~powerpc-mm-implement-_user_accessible_page-for-ptes
+++ a/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -539,6 +539,11 @@ static inline bool pte_access_permitted(
 	return arch_pte_access_permitted(pte_val(pte), write, 0);
 }
 
+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.
@@ -1381,5 +1386,17 @@ static inline bool is_pte_rw_upgrade(uns
 	return false;
 }
 
+#define pmd_user_accessible_page pmd_user_accessible_page
+static inline bool pmd_user_accessible_page(pmd_t pmd, unsigned long addr)
+{
+	return pmd_leaf(pmd) && pte_user_accessible_page(pmd_pte(pmd), addr);
+}
+
+#define pud_user_accessible_page pud_user_accessible_page
+static inline bool pud_user_accessible_page(pud_t pud, unsigned long addr)
+{
+	return pud_leaf(pud) && pte_user_accessible_page(pud_pte(pud), addr);
+}
+
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */
--- a/arch/powerpc/include/asm/nohash/pgtable.h~powerpc-mm-implement-_user_accessible_page-for-ptes
+++ a/arch/powerpc/include/asm/nohash/pgtable.h
@@ -243,6 +243,11 @@ static inline bool pte_access_permitted(
 	return true;
 }
 
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && !is_kernel_addr(addr);
+}
+
 /* Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  *
--- a/arch/powerpc/include/asm/pgtable.h~powerpc-mm-implement-_user_accessible_page-for-ptes
+++ a/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,14 @@ static inline int pud_pfn(pud_t pud)
 }
 #endif
 
+#ifndef pmd_user_accessible_page
+#define pmd_user_accessible_page(pmd, addr)	false
+#endif
+
+#ifndef pud_user_accessible_page
+#define pud_user_accessible_page(pud, addr)	false
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PGTABLE_H */
_

Patches currently in -mm which might be from rmclure@linux.ibm.com are

mm-page_table_check-reinstate-address-parameter-in-page_table_check_pud_set.patch
mm-page_table_check-reinstate-address-parameter-in-page_table_check_pmd_set.patch
mm-page_table_check-provide-addr-parameter-to-page_table_check_ptes_set.patch
mm-page_table_check-reinstate-address-parameter-in-page_table_check_pud_clear.patch
mm-page_table_check-reinstate-address-parameter-in-page_table_check_pmd_clear.patch
mm-page_table_check-reinstate-address-parameter-in-page_table_check_pte_clear.patch
mm-provide-address-parameter-to-ptemdud_user_accessible_page.patch
powerpc-mm-add-pud_pfn-stub.patch
powerpc-mm-implement-_user_accessible_page-for-ptes.patch
powerpc-mm-use-set_pte_at_unchecked-for-internal-usages.patch
powerpc-mm-support-page-table-check.patch