On 3 Nov 2022, at 7:02 pm, Christophe Leroy [off-list ref] wrote:



Le 24/10/2022 à 02:35, Rohan McLure a écrit :

quoted

Add the following helpers for detecting whether a page table entry
is a leaf and is accessible to user space.

 * pte_user_accessible_page
 * pmd_user_accessible_page
 * pud_user_accessible_page

Also implement missing pud_user definitions for both Book3S/nohash 64-bit
systems, and pmd_user for Book3S/nohash 32-bit systems.

Signed-off-by: Rohan McLure <redacted>
---
V2: Provide missing pud_user implementations, use p{u,m}d_is_leaf.
V3: Provide missing pmd_user implementations as stubs in 32-bit.
---
 arch/powerpc/include/asm/book3s/32/pgtable.h |  4 ++++
 arch/powerpc/include/asm/book3s/64/pgtable.h | 10 ++++++++++
 arch/powerpc/include/asm/nohash/32/pgtable.h |  1 +
 arch/powerpc/include/asm/nohash/64/pgtable.h | 10 ++++++++++
 arch/powerpc/include/asm/pgtable.h           | 15 +++++++++++++++
 5 files changed, 40 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 40041ac713d9..8bf1c538839a 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h

@@ -531,6 +531,10 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
  return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
 }

+static inline bool pmd_user(pmd_t pmd)
+{
+ return 0;
+}


 /* This low level function performs the actual PTE insertion

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index f9aefa492df0..3083111f9d0a 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -621,6 +621,16 @@ static inline bool pte_user(pte_t pte)
  return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
 }

+static inline bool pmd_user(pmd_t pmd)
+{
+ return !(pmd_raw(pmd) & cpu_to_be64(_PAGE_PRIVILEGED));
+}
+
+static inline bool pud_user(pud_t pud)
+{
+ return !(pud_raw(pud) & cpu_to_be64(_PAGE_PRIVILEGED));
+}
+
 #define pte_access_permitted pte_access_permitted
 static inline bool pte_access_permitted(pte_t pte, bool write)
 {

diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 9091e4904a6b..b92044d9d778 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h

@@ -354,6 +354,7 @@ static inline int pte_young(pte_t pte)
 #endif

 #define pmd_page(pmd) pfn_to_page(pmd_pfn(pmd))
+#define pmd_user(pmd) 0
 /*
  * Encode and decode a swap entry.
  * Note that the bits we use in a PTE for representing a swap entry

diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index 599921cc257e..23c5135178d1 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h

@@ -123,6 +123,11 @@ static inline pte_t pmd_pte(pmd_t pmd)
  return __pte(pmd_val(pmd));
 }

+static inline bool pmd_user(pmd_t pmd)
+{
+ return (pmd_val(pmd) & _PAGE_USER) == _PAGE_USER;
+}
+
 #define pmd_none(pmd) (!pmd_val(pmd))
 #define pmd_bad(pmd) (!is_kernel_addr(pmd_val(pmd)) \
   || (pmd_val(pmd) & PMD_BAD_BITS))

@@ -158,6 +163,11 @@ static inline pte_t pud_pte(pud_t pud)
  return __pte(pud_val(pud));
 }

+static inline bool pud_user(pud_t pud)
+{
+ return (pud_val(pud) & _PAGE_USER) == _PAGE_USER;
+}
+
 static inline pud_t pte_pud(pte_t pte)
 {
  return __pud(pte_val(pte));

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 36956fb440e1..3cb5de9f1aa4 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h

@@ -172,6 +172,21 @@ static inline int pud_pfn(pud_t pud)
 }
 #endif

+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return pte_present(pte) && pte_user(pte);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_is_leaf(pmd) && pmd_present(pmd) && pmd_user(pmd);

pmd_is_leaf() is specific to powerpc and we may want to get rid of it.

Can you use pmd_leaf() instead ?

quoted

+}
+
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+ return pud_is_leaf(pud) && pud_present(pud) && pud_user(pud);

pud_is_leaf() is specific to powerpc and we may want to get rid of it.

Can you use pud_leaf() instead ?

Going to resend, replacing all usages/definitions of p{m,u,4}d_is_leaf()
with p{m,u,4}_leaf() in arch/powerpc prior to this patch.

quoted

+}
+
 #endif /* __ASSEMBLY__ */

 #endif /* _ASM_POWERPC_PGTABLE_H */