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This allows userspace tools, such as CRIU, to detect and handle guard regions. Signed-off-by: Andrei Vagin Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand --- Documentation/admin-guide/mm/pagemap.rst | 1 + fs/proc/task_mmu.c | 8 ++++++-- include/uapi/linux/fs.h | 1 + 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index a297e824f990..7997b67ffc97 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -234,6 +234,7 @@ Following flags about pages are currently supported: - ``PAGE_IS_PFNZERO`` - Page has zero PFN - ``PAGE_IS_HUGE`` - Page is PMD-mapped THP or Hugetlb backed - ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty +- ``PAGE_IS_GUARD`` - Page is a guard region The ``struct pm_scan_arg`` is used as the argument of the IOCTL. diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index c17615e21a5d..698d660bfee4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2067,7 +2067,8 @@ static int pagemap_release(struct inode *inode, struct file *file) #define PM_SCAN_CATEGORIES (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \ PAGE_IS_FILE | PAGE_IS_PRESENT | \ PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \ - PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY) + PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY | \ + PAGE_IS_GUARD) #define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC) struct pagemap_scan_private { @@ -2108,8 +2109,11 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p, if (!pte_swp_uffd_wp_any(pte)) categories |= PAGE_IS_WRITTEN; + swp = pte_to_swp_entry(pte); + if (is_guard_swp_entry(swp)) + categories |= PAGE_IS_GUARD; + if (p->masks_of_interest & PAGE_IS_FILE) { - swp = pte_to_swp_entry(pte); if (is_pfn_swap_entry(swp) && !folio_test_anon(pfn_swap_entry_folio(swp))) categories |= PAGE_IS_FILE; diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 2bbe00cf1248..8aa66c5f69b7 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -363,6 +363,7 @@ typedef int __bitwise __kernel_rwf_t; #define PAGE_IS_PFNZERO (1 << 5) #define PAGE_IS_HUGE (1 << 6) #define PAGE_IS_SOFT_DIRTY (1 << 7) +#define PAGE_IS_GUARD (1 << 8) /* * struct page_region - Page region with flags From patchwork Thu Mar 20 06:39:03 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrei Vagin X-Patchwork-Id: 14023466 Received: from mail-io1-f74.google.com (mail-io1-f74.google.com [209.85.166.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 96CB31EF394 for ; 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Wed, 19 Mar 2025 23:39:50 -0700 (PDT) Date: Thu, 20 Mar 2025 06:39:03 +0000 In-Reply-To: <20250320063903.2685882-1-avagin@google.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250320063903.2685882-1-avagin@google.com> X-Mailer: git-send-email 2.49.0.rc1.451.g8f38331e32-goog Message-ID: <20250320063903.2685882-3-avagin@google.com> Subject: [PATCH 2/2] selftests/mm: add PAGEMAP_SCAN guard region test From: Andrei Vagin To: Lorenzo Stoakes , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, David Hildenbrand , Shuah Khan , Jonathan Corbet , Andrei Vagin From: Andrei Vagin Add a selftest to verify the PAGEMAP_SCAN ioctl correctly reports guard regions using the newly introduced PAGE_IS_GUARD flag. Signed-off-by: Andrei Vagin --- tools/testing/selftests/mm/guard-regions.c | 53 ++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c index 0c7183e8b661..24e09092fda5 100644 --- a/tools/testing/selftests/mm/guard-regions.c +++ b/tools/testing/selftests/mm/guard-regions.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -2079,4 +2080,56 @@ TEST_F(guard_regions, pagemap) ASSERT_EQ(munmap(ptr, 10 * page_size), 0); } +/* + * Assert that PAGEMAP_SCAN correctly reports guard region ranges. + */ +TEST_F(guard_regions, pagemap_scan) +{ + const unsigned long page_size = self->page_size; + struct page_region pm_regs[10]; + struct pm_scan_arg pm_scan_args = { + .size = sizeof(struct pm_scan_arg), + .category_anyof_mask = PAGE_IS_GUARD, + .return_mask = PAGE_IS_GUARD, + .vec = (long)&pm_regs, + .vec_len = ARRAY_SIZE(pm_regs), + }; + int proc_fd, i; + char *ptr; + + proc_fd = open("/proc/self/pagemap", O_RDONLY); + ASSERT_NE(proc_fd, -1); + + ptr = mmap_(self, variant, NULL, 10 * page_size, + PROT_READ | PROT_WRITE, 0, 0); + ASSERT_NE(ptr, MAP_FAILED); + + pm_scan_args.start = (long)ptr; + pm_scan_args.end = (long)ptr + 10 * page_size; + ASSERT_EQ(ioctl(proc_fd, PAGEMAP_SCAN, &pm_scan_args), 0); + ASSERT_EQ(pm_scan_args.walk_end, (long)ptr + 10 * page_size); + + /* Install a guard region in every other page. */ + for (i = 0; i < 10; i += 2) { + char *ptr_p = &ptr[i * page_size]; + + ASSERT_EQ(syscall(__NR_madvise, ptr_p, page_size, MADV_GUARD_INSTALL), 0); + } + + ASSERT_EQ(ioctl(proc_fd, PAGEMAP_SCAN, &pm_scan_args), 5); + ASSERT_EQ(pm_scan_args.walk_end, (long)ptr + 10 * page_size); + + /* Re-read from pagemap, and assert guard regions are detected. */ + for (i = 0; i < 5; i++) { + long ptr_p = (long)&ptr[2 * i * page_size]; + + ASSERT_EQ(pm_regs[i].start, ptr_p); + ASSERT_EQ(pm_regs[i].end, ptr_p + page_size); + ASSERT_EQ(pm_regs[i].categories, PAGE_IS_GUARD); + } + + ASSERT_EQ(close(proc_fd), 0); + ASSERT_EQ(munmap(ptr, 10 * page_size), 0); +} + TEST_HARNESS_MAIN