[PATCH v18 10/12] powerpc/mm: Implement *_user_accessible_page() for ptes

Andrew Donnellan
2025-12-18T17:11:38Z

From: Rohan McLure <rmclure@linux.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.

[ajd@linux.ibm.com: rebase and clean up]
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>
---
v18: move the definitions of p{m,u}d_user_accessible_page() to be next to
p{m,u}d_access_permitted()
---
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 87dcca962be7864be3da1e7aad0992d2bc4581cf..2edca1068b6f31e64ddc4f39f594bb3ac27a8435 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 aac8ce30cd3b39ae184a69879a57ce8d6698fff5..2d69a827594f3c8593283fa11acd4750577e71a7 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -539,6 +539,11 @@ 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.
@@ -909,6 +914,12 @@ 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 pud_leaf(pud) && 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)
{
@@ -1074,6 +1085,12 @@ 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 pmd_leaf(pmd) && 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/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 5af168b7f292415c5896a5c63bd78641d9a2c2a6..9bf3e40f27b645da660cbeeb561f08eeef180b1b 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 17fd7ff6e535b6d2b320fc8c292b7eb964fa0ef2..859cdbaa54a7fa159d5bbd4653f7871381f4910f 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -202,6 +202,14 @@ static inline bool arch_supports_memmap_on_memory(unsigned long vmemmap_size)

#endif /* CONFIG_PPC64 */

+#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 /* __ASSEMBLER__ */

#endif /* _ASM_POWERPC_PGTABLE_H */

--
2.52.0