mm: userfaultfd: add pgtable_supports_uffd_wp()

Some platforms can customize the PTE/PMD entry uffd-wp bit making it
unavailable even if the architecture provides the resource.  This patch
adds a macro API pgtable_supports_uffd_wp() that allows architectures to
define their specific implementations to check if the uffd-wp bit is
available on which device the kernel is running.

Also this patch is removing "ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP" and
"ifdef CONFIG_PTE_MARKER_UFFD_WP" in favor of pgtable_supports_uffd_wp()
and uffd_supports_wp_marker() checks respectively that default to
IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) and
"IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) &&
IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP)" if not overridden by the
architecture, no change in behavior is expected.

Link: https://lkml.kernel.org/r/20251113072806.795029-3-zhangchunyan@iscas.ac.cn
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Jones <ajones@ventanamicro.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Conor Dooley <conor.dooley@microchip.com>
Cc: Conor Dooley <conor@kernel.org>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 3f539aabc3b3835250dc5f5ab609cfd26b5e3110..5a0d19dec7ba3c08f52a64ee7da3e3866177dec4 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1289,9 +1289,9 @@ 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 (!pgtable_supports_uffd_wp())
+                       goto out;
+
                vm_flags |= VM_UFFD_WP;
        }
        if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1999,14 +1999,14 @@ 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 (!pgtable_supports_uffd_wp())
+               uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+       if (!uffd_supports_wp_marker()) {
+               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 828966d4c28115a0315ed9d19ab7a83269e5244a..0d85791efdf778f76671044291625aa212341b2f 100644 (file)
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -1,6 +1,23 @@
 #ifndef _ASM_GENERIC_PGTABLE_UFFD_H
 #define _ASM_GENERIC_PGTABLE_UFFD_H
 
+/*
+ * Some platforms can customize the uffd-wp bit, making it unavailable
+ * even if the architecture provides the resource.
+ * Adding this API allows architectures to add their own checks for the
+ * devices on which the kernel is running.
+ * Note: When overriding it, please make sure the
+ * CONFIG_HAVE_ARCH_USERFAULTFD_WP is part of this macro.
+ */
+#ifndef pgtable_supports_uffd_wp
+#define pgtable_supports_uffd_wp()     IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP)
+#endif
+
+static inline bool uffd_supports_wp_marker(void)
+{
+       return pgtable_supports_uffd_wp() && IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP);
+}
+
 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
 static __always_inline int pte_uffd_wp(pte_t pte)
 {

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index b58f34c4fe92ebb854932b01be43b593d60097b8..fa2d6ba811b53e0e8166a6468c134c793f7129be 100644 (file)
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -553,7 +553,6 @@ static inline pte_marker copy_pte_marker(
 
        return dstm;
 }
-#endif
 
 /*
  * If this pte is wr-protected by uffd-wp in any form, arm the special pte to
@@ -571,9 +570,11 @@ 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
        bool arm_uffd_pte = false;
 
+       if (!uffd_supports_wp_marker())
+               return false;
+
        /* The current status of the pte should be "cleared" before calling */
        WARN_ON_ONCE(!pte_none(ptep_get(pte)));
 
@@ -602,7 +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;
 }
 
@@ -616,6 +617,7 @@ static inline bool vma_has_recency(const struct vm_area_struct *vma)
 
        return true;
 }
+#endif
 
 /**
  * num_pages_contiguous() - determine the number of contiguous pages

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 96b089dff4efaf008f6edd36adc799f2716feee3..fd5f4276549732468ddb5faa0e0cc5f3703efd13 100644 (file)
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -228,15 +228,14 @@ 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 (!uffd_supports_wp_marker() && (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) ||
@@ -291,6 +290,43 @@ void userfaultfd_release_new(struct userfaultfd_ctx *ctx);
 void userfaultfd_release_all(struct mm_struct *mm,
                             struct userfaultfd_ctx *ctx);
 
+static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
+{
+       /* Only wr-protect mode uses pte markers */
+       if (!userfaultfd_wp(vma))
+               return false;
+
+       /* File-based uffd-wp always need markers */
+       if (!vma_is_anonymous(vma))
+               return true;
+
+       /*
+        * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
+        * enabled (to apply markers on zero pages).
+        */
+       return userfaultfd_wp_unpopulated(vma);
+}
+
+/*
+ * Returns true if this is a swap pte and was uffd-wp wr-protected in either
+ * forms (pte marker or a normal swap pte), false otherwise.
+ */
+static inline bool pte_swp_uffd_wp_any(pte_t pte)
+{
+       if (!uffd_supports_wp_marker())
+               return false;
+
+       if (pte_present(pte))
+               return false;
+
+       if (pte_swp_uffd_wp(pte))
+               return true;
+
+       if (pte_is_uffd_wp_marker(pte))
+               return true;
+
+       return false;
+}
 #else /* CONFIG_USERFAULTFD */
 
 /* mm helpers */
@@ -415,23 +451,9 @@ static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
        return false;
 }
 
-#endif /* CONFIG_USERFAULTFD */
-
 static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
 {
-       /* Only wr-protect mode uses pte markers */
-       if (!userfaultfd_wp(vma))
-               return false;
-
-       /* File-based uffd-wp always need markers */
-       if (!vma_is_anonymous(vma))
-               return true;
-
-       /*
-        * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
-        * enabled (to apply markers on zero pages).
-        */
-       return userfaultfd_wp_unpopulated(vma);
+       return false;
 }
 
 /*
@@ -440,16 +462,7 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
  */
 static inline bool pte_swp_uffd_wp_any(pte_t pte)
 {
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
-       if (pte_present(pte))
-               return false;
-       if (pte_swp_uffd_wp(pte))
-               return true;
-
-       if (pte_is_uffd_wp_marker(pte))
-               return true;
-#endif
        return false;
 }
-
+#endif /* CONFIG_USERFAULTFD */
 #endif /* _LINUX_USERFAULTFD_K_H */

diff --git a/mm/memory.c b/mm/memory.c
index 50b93b45b174005ce82e752ef24b00522f8e0aa7..6675e87eb7dd74100aa447a86d7ca646bef3d232 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1590,7 +1590,9 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
 {
        bool was_installed = false;
 
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+       if (!uffd_supports_wp_marker())
+               return false;
+
        /* Zap on anonymous always means dropping everything */
        if (vma_is_anonymous(vma))
                return false;
@@ -1607,7 +1609,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
                pte++;
                addr += PAGE_SIZE;
        }
-#endif
+
        return was_installed;
 }