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Message-Id: <20250905103651.489197-3-zhangchunyan@iscas.ac.cn>
Date: Fri, 5 Sep 2025 18:36:48 +0800
From: Chunyan Zhang <zhangchunyan@...as.ac.cn>
To: linux-riscv@...ts.infradead.org,
linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alex@...ti.fr>,
Andrew Morton <akpm@...ux-foundation.org>,
Deepak Gupta <debug@...osinc.com>,
Ved Shanbhogue <ved@...osinc.com>,
Peter Xu <peterx@...hat.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Jan Kara <jack@...e.cz>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Wei Xu <weixugc@...gle.com>,
David Hildenbrand <david@...hat.com>,
Chunyan Zhang <zhang.lyra@...il.com>
Subject: [PATCH v9 2/5] mm: uffd_wp: Add pte_uffd_wp_available()
Some platforms can customize the PTE uffd_wp bit and make it unavailable
even if the architecture allows providing the PTE resource.
This patch adds a macro API which allows architectures to define
their specific one for checking if the PTE uffd_wp bit is available.
Signed-off-by: Chunyan Zhang <zhangchunyan@...as.ac.cn>
---
fs/userfaultfd.c | 25 +++++++++--------
include/asm-generic/pgtable_uffd.h | 12 ++++++++
include/linux/mm_inline.h | 6 ++--
include/linux/pgtable.h | 1 +
include/linux/userfaultfd_k.h | 44 +++++++++++++++++++-----------
mm/memory.c | 6 ++--
6 files changed, 63 insertions(+), 31 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..68e5006e5158 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1270,9 +1270,10 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
vm_flags |= VM_UFFD_MISSING;
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
- goto out;
-#endif
+ if (!IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) ||
+ !pte_uffd_wp_available())
+ goto out;
+
vm_flags |= VM_UFFD_WP;
}
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1980,14 +1981,16 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
uffdio_api.features &=
~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
#endif
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
- uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
-#endif
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
- uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
- uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
- uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
-#endif
+ if (!IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) ||
+ !pte_uffd_wp_available())
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) ||
+ !pte_uffd_wp_available()) {
+ uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
+ }
ret = -EINVAL;
if (features & ~uffdio_api.features)
diff --git a/include/asm-generic/pgtable_uffd.h b/include/asm-generic/pgtable_uffd.h
index 828966d4c281..b86a5ff447da 100644
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -61,6 +61,18 @@ static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
{
return pmd;
}
+#define pte_uffd_wp_available() (false)
+#else
+/*
+ * Some platforms can customize the PTE uffd_wp bit and make it unavailable
+ * even if the architecture allows providing the PTE resource.
+ * This allows architectures to define their own API for checking if
+ * the PTE uffd_wp bit is available.
+ */
+#ifndef pte_uffd_wp_available
+#define pte_uffd_wp_available() (true)
+#endif
+
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
#endif /* _ASM_GENERIC_PGTABLE_UFFD_H */
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 89b518ff097e..a81055bb3f87 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -570,7 +570,9 @@ static inline bool
pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
pte_t *pte, pte_t pteval)
{
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) || !pte_uffd_wp_available())
+ return false;
+
bool arm_uffd_pte = false;
/* The current status of the pte should be "cleared" before calling */
@@ -601,7 +603,7 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
make_pte_marker(PTE_MARKER_UFFD_WP));
return true;
}
-#endif
+
return false;
}
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2a489647ac96..51f5b610c5ec 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1564,6 +1564,7 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
}
#endif
#else /* !CONFIG_HAVE_ARCH_SOFT_DIRTY */
+#define pte_soft_dirty_available() (false)
static inline int pte_soft_dirty(pte_t pte)
{
return 0;
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c0e716aec26a..ec4a815286c8 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -228,15 +228,15 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
if (wp_async && (vm_flags == VM_UFFD_WP))
return true;
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
/*
* If user requested uffd-wp but not enabled pte markers for
* uffd-wp, then shmem & hugetlbfs are not supported but only
* anonymous.
*/
- if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
+ if ((!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) ||
+ !pte_uffd_wp_available()) &&
+ (vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
return false;
-#endif
/* By default, allow any of anon|shmem|hugetlb */
return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
@@ -437,8 +437,11 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- return is_pte_marker_entry(entry) &&
- (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
+ if (pte_uffd_wp_available())
+ return is_pte_marker_entry(entry) &&
+ (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
+ else
+ return false;
#else
return false;
#endif
@@ -447,14 +450,19 @@ static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
static inline bool pte_marker_uffd_wp(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- swp_entry_t entry;
+ if (pte_uffd_wp_available()) {
+ swp_entry_t entry;
- if (!is_swap_pte(pte))
- return false;
+ if (!is_swap_pte(pte))
+ return false;
- entry = pte_to_swp_entry(pte);
+ entry = pte_to_swp_entry(pte);
+
+ return pte_marker_entry_uffd_wp(entry);
+ } else {
+ return false;
+ }
- return pte_marker_entry_uffd_wp(entry);
#else
return false;
#endif
@@ -467,14 +475,18 @@ static inline bool pte_marker_uffd_wp(pte_t pte)
static inline bool pte_swp_uffd_wp_any(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- if (!is_swap_pte(pte))
- return false;
+ if (pte_uffd_wp_available()) {
+ if (!is_swap_pte(pte))
+ return false;
- if (pte_swp_uffd_wp(pte))
- return true;
+ if (pte_swp_uffd_wp(pte))
+ return true;
- if (pte_marker_uffd_wp(pte))
- return true;
+ if (pte_marker_uffd_wp(pte))
+ return true;
+ } else {
+ return false;
+ }
#endif
return false;
}
diff --git a/mm/memory.c b/mm/memory.c
index 0ba4f6b71847..1c61b2d7bd4d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1465,7 +1465,9 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
{
bool was_installed = false;
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) || !pte_uffd_wp_available())
+ return was_installed;
+
/* Zap on anonymous always means dropping everything */
if (vma_is_anonymous(vma))
return false;
@@ -1482,7 +1484,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
pte++;
addr += PAGE_SIZE;
}
-#endif
+
return was_installed;
}
--
2.34.1
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