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Date: Wed, 1 May 2024 15:54:19 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Joey Gouly <joey.gouly@....com>,
Ard Biesheuvel <ardb@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Anshuman Khandual <anshuman.khandual@....com>,
David Hildenbrand <david@...hat.com>,
Peter Xu <peterx@...hat.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Shivansh Vij <shivanshvij@...look.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/3] arm64/mm: Add uffd write-protect support
Let's use the newly-free PTE SW bit (58) to add support for uffd-wp.
The standard handlers are implemented for set/test/clear for both pte
and pmd. Additionally we must also track the uffd-wp state as a pte swp
bit, so use a free swap pte bit (3).
Acked-by: Peter Xu <peterx@...hat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/pgtable-prot.h | 8 +++++
arch/arm64/include/asm/pgtable.h | 44 +++++++++++++++++++++++++++
3 files changed, 53 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b11c98b3e84..763e221f2169 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -255,6 +255,7 @@ config ARM64
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
+ select HAVE_ARCH_USERFAULTFD_WP if USERFAULTFD
select TRACE_IRQFLAGS_SUPPORT
select TRACE_IRQFLAGS_NMI_SUPPORT
select HAVE_SOFTIRQ_ON_OWN_STACK
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 3047d10987fd..ef51aed39765 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -20,6 +20,14 @@
#define PTE_DEVMAP (_AT(pteval_t, 1) << 57)
#define PTE_PRESENT_INVALID (PTE_NG) /* only when !PTE_VALID */
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+#define PTE_UFFD_WP (_AT(pteval_t, 1) << 58) /* uffd-wp tracking */
+#define PTE_SWP_UFFD_WP (_AT(pteval_t, 1) << 3) /* only for swp ptes */
+#else
+#define PTE_UFFD_WP (_AT(pteval_t, 0))
+#define PTE_SWP_UFFD_WP (_AT(pteval_t, 0))
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
#define _PROT_DEFAULT (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
#define _PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7f1ff59c43ed..2dcf582981ae 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -280,6 +280,23 @@ static inline pte_t pte_mkdevmap(pte_t pte)
return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL));
}
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+static inline int pte_uffd_wp(pte_t pte)
+{
+ return !!(pte_val(pte) & PTE_UFFD_WP);
+}
+
+static inline pte_t pte_mkuffd_wp(pte_t pte)
+{
+ return pte_wrprotect(set_pte_bit(pte, __pgprot(PTE_UFFD_WP)));
+}
+
+static inline pte_t pte_clear_uffd_wp(pte_t pte)
+{
+ return clear_pte_bit(pte, __pgprot(PTE_UFFD_WP));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
static inline void __set_pte(pte_t *ptep, pte_t pte)
{
WRITE_ONCE(*ptep, pte);
@@ -472,6 +489,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
return clear_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
}
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+static inline pte_t pte_swp_mkuffd_wp(pte_t pte)
+{
+ return set_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP));
+}
+
+static inline int pte_swp_uffd_wp(pte_t pte)
+{
+ return !!(pte_val(pte) & PTE_SWP_UFFD_WP);
+}
+
+static inline pte_t pte_swp_clear_uffd_wp(pte_t pte)
+{
+ return clear_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
#ifdef CONFIG_NUMA_BALANCING
/*
* See the comment in include/linux/pgtable.h
@@ -522,6 +556,15 @@ static inline int pmd_trans_huge(pmd_t pmd)
#define pmd_mkdirty(pmd) pte_pmd(pte_mkdirty(pmd_pte(pmd)))
#define pmd_mkyoung(pmd) pte_pmd(pte_mkyoung(pmd_pte(pmd)))
#define pmd_mkinvalid(pmd) pte_pmd(pte_mkinvalid(pmd_pte(pmd)))
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+#define pmd_uffd_wp(pmd) pte_uffd_wp(pmd_pte(pmd))
+#define pmd_mkuffd_wp(pmd) pte_pmd(pte_mkuffd_wp(pmd_pte(pmd)))
+#define pmd_clear_uffd_wp(pmd) pte_pmd(pte_clear_uffd_wp(pmd_pte(pmd)))
+#define pmd_swp_uffd_wp(pmd) pte_swp_uffd_wp(pmd_pte(pmd))
+#define pmd_swp_mkuffd_wp(pmd) pte_pmd(pte_swp_mkuffd_wp(pmd_pte(pmd)))
+#define pmd_swp_clear_uffd_wp(pmd) \
+ pte_pmd(pte_swp_clear_uffd_wp(pmd_pte(pmd)))
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
#define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd))
@@ -1254,6 +1297,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
* Encode and decode a swap entry:
* bits 0-1: present (must be zero)
* bits 2: remember PG_anon_exclusive
+ * bit 3: remember uffd-wp state
* bits 6-10: swap type
* bit 11: PTE_PRESENT_INVALID (must be zero)
* bits 12-61: swap offset
--
2.25.1
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