linux-kernel - [PATCH 5/6] mm/pagemap: Export uffd-wp protection information

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Date:   Wed, 28 Apr 2021 18:50:29 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Mike Kravetz <mike.kravetz@...cle.com>, peterx@...hat.com,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jerome Glisse <jglisse@...hat.com>
Subject: [PATCH 5/6] mm/pagemap: Export uffd-wp protection information

Export the PTE/PMD status of uffd-wp to pagemap too.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 Documentation/admin-guide/mm/pagemap.rst | 2 ++
 fs/proc/task_mmu.c                       | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index 340a5aee9b802..fb578fbbb76ca 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -21,6 +21,8 @@ There are four components to pagemap:
     * Bit  55    pte is soft-dirty (see
       :ref:`Documentation/admin-guide/mm/soft-dirty.rst <soft_dirty>`)
     * Bit  56    page exclusively mapped (since 4.2)
+    * Bit  57    pte is uffd-wp write-protected (since 5.13) (see
+      :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`)
     * Bits 57-60 zero
     * Bit  61    page is file-page or shared-anon (since 3.5)
     * Bit  62    page swapped
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index fc9784544b241..ce3b5f33b44c4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1302,6 +1302,7 @@ struct pagemapread {
 #define PM_PFRAME_MASK		GENMASK_ULL(PM_PFRAME_BITS - 1, 0)
 #define PM_SOFT_DIRTY		BIT_ULL(55)
 #define PM_MMAP_EXCLUSIVE	BIT_ULL(56)
+#define PM_UFFD_WP		BIT_ULL(57)
 #define PM_FILE			BIT_ULL(61)
 #define PM_SWAP			BIT_ULL(62)
 #define PM_PRESENT		BIT_ULL(63)
@@ -1375,10 +1376,14 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 		page = vm_normal_page(vma, addr, pte);
 		if (pte_soft_dirty(pte))
 			flags |= PM_SOFT_DIRTY;
+		if (pte_uffd_wp(pte))
+			flags |= PM_UFFD_WP;
 	} else if (is_swap_pte(pte)) {
 		swp_entry_t entry;
 		if (pte_swp_soft_dirty(pte))
 			flags |= PM_SOFT_DIRTY;
+		if (pte_swp_uffd_wp(pte))
+			flags |= PM_UFFD_WP;
 		entry = pte_to_swp_entry(pte);
 		if (pm->show_pfn)
 			frame = swp_type(entry) |
@@ -1426,6 +1431,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
 			flags |= PM_PRESENT;
 			if (pmd_soft_dirty(pmd))
 				flags |= PM_SOFT_DIRTY;
+			if (pmd_uffd_wp(pmd))
+				flags |= PM_UFFD_WP;
 			if (pm->show_pfn)
 				frame = pmd_pfn(pmd) +
 					((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -1444,6 +1451,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
 			flags |= PM_SWAP;
 			if (pmd_swp_soft_dirty(pmd))
 				flags |= PM_SOFT_DIRTY;
+			if (pmd_swp_uffd_wp(pmd))
+				flags |= PM_UFFD_WP;
 			VM_BUG_ON(!is_pmd_migration_entry(pmd));
 			page = migration_entry_to_page(entry);
 		}
-- 
2.26.2