linux-kernel - [PATCH v13 09/11] powerpc: mm: Implement *_user_accessible

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Message-ID: <20250211161404.850215-10-ajd@linux.ibm.com>
Date: Wed, 12 Feb 2025 03:14:02 +1100
From: Andrew Donnellan <ajd@...ux.ibm.com>
To: linuxppc-dev@...ts.ozlabs.org
Cc: x86@...nel.org, linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        pasha.tatashin@...een.com, sweettea-kernel@...miny.me
Subject: [PATCH v13 09/11] powerpc: mm: Implement *_user_accessible_page() for ptes

From: Rohan McLure <rmclure@...ux.ibm.com>

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.

Signed-off-by: Rohan McLure <rmclure@...ux.ibm.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@...een.com>
[ajd: rebase and fix commit message]
Signed-off-by: Andrew Donnellan <ajd@...ux.ibm.com>
---
 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(+)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 42c3af90d1f0..a2305d850fc9 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -437,6 +437,11 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	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.
  *
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 6d98e6f08d4d..754d4d525f0e 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -540,6 +540,11 @@ 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, 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.
@@ -1431,5 +1436,17 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
 	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_ */
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 8d1f0b7062eb..1c3dfe2d6cc1 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -243,6 +243,11 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
 	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.
  *
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index bb43e4f46367..3cae32c74fed 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -224,6 +224,14 @@ 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 */
-- 
2.48.1