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Message-Id: <20240815030403.832489-4-zhangchunyan@iscas.ac.cn>
Date: Thu, 15 Aug 2024 11:04:03 +0800
From: Chunyan Zhang <zhangchunyan@...as.ac.cn>
To: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexandre Ghiti <alex@...ti.fr>
Cc: linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org,
Chunyan Zhang <zhang.lyra@...il.com>
Subject: [PATCH V4 3/3] riscv: mm: Add uffd write-protect support
Reuse PTE bit(9) to do uffd-wp tracking and make it mutually exclusive
with soft-dirty and DEVMAP which all use this PTE bit.
Additionally for tracking the uffd-wp state as a PTE swap bit,
we use swap entry pte bit(4) which is also used by swap
soft-dirty tracking.
Signed-off-by: Chunyan Zhang <zhangchunyan@...as.ac.cn>
---
arch/riscv/Kconfig | 7 +++
arch/riscv/include/asm/pgtable-bits.h | 13 ++++++
arch/riscv/include/asm/pgtable.h | 66 ++++++++++++++++++++++++++-
3 files changed, 85 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f1460fc01cd4..aa595a5ed4b8 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -971,6 +971,13 @@ config RISCV_HAS_SOFT_DIRTY
help
The PTE bit(9) is used for soft-dirty tracking.
+config RISCV_HAS_USERFAULTFD_WP
+ bool "userfaultfd write protection"
+ select HAVE_ARCH_USERFAULTFD_WP
+ depends on USERFAULTFD
+ help
+ The PTE bit(9) is used for userfaultfd write-protected
+ tracking.
endchoice
endmenu # "Kernel features"
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index c6d51fe9fc6f..7de16141c049 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -38,6 +38,19 @@
#define _PAGE_SWP_SOFT_DIRTY 0
#endif /* CONFIG_MEM_SOFT_DIRTY */
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+/*
+ * CONFIG_HAVE_ARCH_USERFAULTFD_WP is mutually exclusive with
+ * HAVE_ARCH_SOFT_DIRTY so we can use the same bit for uffd-wp
+ * and soft-dirty tracking.
+ */
+#define _PAGE_UFFD_WP (1 << 9) /* RSW: 0x2 for uffd-wp tracking */
+#define _PAGE_SWP_UFFD_WP _PAGE_USER
+#else
+#define _PAGE_UFFD_WP 0
+#define _PAGE_SWP_UFFD_WP 0
+#endif
+
#define _PAGE_TABLE _PAGE_PRESENT
/*
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index d41507919ef2..6ce4c9ba862a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -417,6 +417,38 @@ static inline pte_t pte_wrprotect(pte_t pte)
return __pte(pte_val(pte) & ~(_PAGE_WRITE));
}
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+static inline int pte_uffd_wp(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_UFFD_WP;
+}
+
+static inline pte_t pte_mkuffd_wp(pte_t pte)
+{
+ return pte_wrprotect(__pte(pte_val(pte) | _PAGE_UFFD_WP));
+}
+
+static inline pte_t pte_clear_uffd_wp(pte_t pte)
+{
+ return __pte(pte_val(pte) & ~(_PAGE_UFFD_WP));
+}
+
+static inline int pte_swp_uffd_wp(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_UFFD_WP;
+}
+
+static inline pte_t pte_swp_mkuffd_wp(pte_t pte)
+{
+ return pte_wrprotect(__pte(pte_val(pte) | _PAGE_SWP_UFFD_WP));
+}
+
+static inline pte_t pte_swp_clear_uffd_wp(pte_t pte)
+{
+ return __pte(pte_val(pte) & ~(_PAGE_SWP_UFFD_WP));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
/* static inline pte_t pte_mkread(pte_t pte) */
static inline pte_t pte_mkwrite_novma(pte_t pte)
@@ -783,6 +815,38 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
return pte_pmd(pte_mkdevmap(pmd_pte(pmd)));
}
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+static inline int pmd_uffd_wp(pmd_t pmd)
+{
+ return pte_uffd_wp(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_mkuffd_wp(pmd_t pmd)
+{
+ return pte_pmd(pte_mkuffd_wp(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_clear_uffd_wp(pmd_t pmd)
+{
+ return pte_pmd(pte_clear_uffd_wp(pmd_pte(pmd)));
+}
+
+static inline int pmd_swp_uffd_wp(pmd_t pmd)
+{
+ return pte_swp_uffd_wp(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_swp_mkuffd_wp(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_mkuffd_wp(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_clear_uffd_wp(pmd_pte(pmd)));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
static inline int pmd_soft_dirty(pmd_t pmd)
{
@@ -907,7 +971,7 @@ extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
* Format of swap PTE:
* bit 0: _PAGE_PRESENT (zero)
* bit 1 to 3: _PAGE_LEAF (zero)
- * bit 4: _PAGE_SWP_SOFT_DIRTY
+ * bit 4: _PAGE_SWP_SOFT_DIRTY or _PAGE_SWP_UFFD_WP
* bit 5: _PAGE_PROT_NONE (zero)
* bit 6: exclusive marker
* bits 7 to 11: swap type
--
2.34.1
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