[LTP] [PATCH] userfaultfd: Add test using UFFDIO_CONTINUE
Ricardo Branco
rbranco@suse.de
Sat Mar 21 20:58:15 CET 2026
Signed-off-by: Ricardo Branco <rbranco@suse.de>
---
include/lapi/userfaultfd.h | 1 +
runtest/syscalls | 1 +
.../kernel/syscalls/userfaultfd/.gitignore | 1 +
.../kernel/syscalls/userfaultfd/Makefile | 1 +
.../syscalls/userfaultfd/userfaultfd07.c | 161 ++++++++++++++++++
5 files changed, 165 insertions(+)
create mode 100644 testcases/kernel/syscalls/userfaultfd/userfaultfd07.c
diff --git a/include/lapi/userfaultfd.h b/include/lapi/userfaultfd.h
index aab3890b7..c05b8dbf5 100644
--- a/include/lapi/userfaultfd.h
+++ b/include/lapi/userfaultfd.h
@@ -171,6 +171,7 @@ struct uffdio_zeropage {
#ifndef UFFD_PAGEFAULT_FLAG_MINOR
#define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9)
#define UFFDIO_REGISTER_MODE_MINOR ((__u64)1<<2)
+#define UFFD_PAGEFAULT_FLAG_MINOR (1<<2)
#define _UFFDIO_CONTINUE (0x07)
#define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \
diff --git a/runtest/syscalls b/runtest/syscalls
index 6ba0227a8..534140f42 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1780,6 +1780,7 @@ userfaultfd03 userfaultfd03
userfaultfd04 userfaultfd04
userfaultfd05 userfaultfd05
userfaultfd06 userfaultfd06
+userfaultfd07 userfaultfd07
ustat01 ustat01
ustat02 ustat02
diff --git a/testcases/kernel/syscalls/userfaultfd/.gitignore b/testcases/kernel/syscalls/userfaultfd/.gitignore
index bc32fdf3b..3478a162e 100644
--- a/testcases/kernel/syscalls/userfaultfd/.gitignore
+++ b/testcases/kernel/syscalls/userfaultfd/.gitignore
@@ -4,3 +4,4 @@
/userfaultfd04
/userfaultfd05
/userfaultfd06
+/userfaultfd07
diff --git a/testcases/kernel/syscalls/userfaultfd/Makefile b/testcases/kernel/syscalls/userfaultfd/Makefile
index 3252e47df..257249e88 100644
--- a/testcases/kernel/syscalls/userfaultfd/Makefile
+++ b/testcases/kernel/syscalls/userfaultfd/Makefile
@@ -17,3 +17,4 @@ userfaultfd03: CFLAGS += -pthread
userfaultfd04: CFLAGS += -pthread
userfaultfd05: CFLAGS += -pthread
userfaultfd06: CFLAGS += -pthread
+userfaultfd07: CFLAGS += -pthread
diff --git a/testcases/kernel/syscalls/userfaultfd/userfaultfd07.c b/testcases/kernel/syscalls/userfaultfd/userfaultfd07.c
new file mode 100644
index 000000000..f2746d4ca
--- /dev/null
+++ b/testcases/kernel/syscalls/userfaultfd/userfaultfd07.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 SUSE LLC
+ * Author: Ricardo Branco <rbranco@suse.com>
+ */
+
+/*\
+ * Force a pagefault event and handle it using :manpage:`userfaultfd(2)`
+ * from a different thread testing UFFDIO_CONTINUE.
+ */
+
+#define _GNU_SOURCE
+#include "config.h"
+#include <poll.h>
+#include <unistd.h>
+#include "tst_test.h"
+#include "tst_safe_macros.h"
+#include "tst_safe_prw.h"
+#include "tst_safe_pthread.h"
+#include "lapi/memfd.h"
+#include "lapi/userfaultfd.h"
+#include "lapi/syscalls.h"
+
+static int page_size;
+static char *page;
+static int uffd;
+static int memfd = -1;
+
+static int sys_memfd_create(const char *name, unsigned int flags)
+{
+ return tst_syscall(__NR_memfd_create, name, flags);
+}
+
+static void set_pages(void)
+{
+ char ch = 'A';
+
+ page_size = sysconf(_SC_PAGE_SIZE);
+
+ memfd = sys_memfd_create("ltp-uffd-continue", MFD_CLOEXEC);
+ if (memfd < 0)
+ tst_brk(TBROK | TERRNO, "memfd_create failed");
+
+ SAFE_FTRUNCATE(memfd, page_size);
+
+ /*
+ * Populate page cache so that after MADV_DONTNEED the next access
+ * can generate a MINOR fault rather than a MISSING fault.
+ */
+ SAFE_PWRITE(1, memfd, &ch, 1, 0);
+
+ page = SAFE_MMAP(NULL, page_size, PROT_READ, MAP_SHARED, memfd, 0);
+}
+
+static void reset_pages(void)
+{
+ if (page) {
+ SAFE_MUNMAP(page, page_size);
+ page = NULL;
+ }
+
+ if (memfd >= 0) {
+ SAFE_CLOSE(memfd);
+ memfd = -1;
+ }
+}
+
+static void *handle_thread(void *arg LTP_ATTRIBUTE_UNUSED)
+{
+ static struct uffd_msg msg;
+ struct uffdio_continue uffdio_continue = {};
+ struct pollfd pollfd;
+ int nready;
+ char z = 'Z';
+
+ pollfd.fd = uffd;
+ pollfd.events = POLLIN;
+ nready = poll(&pollfd, 1, -1);
+ if (nready == -1)
+ tst_brk(TBROK | TERRNO, "Error on poll");
+
+ SAFE_READ(1, uffd, &msg, sizeof(msg));
+
+ if (msg.event != UFFD_EVENT_PAGEFAULT)
+ tst_brk(TFAIL, "Received unexpected UFFD_EVENT %d", msg.event);
+
+ if (!(msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_MINOR)) {
+ tst_brk(TBROK, "expected MINOR fault, got flags=0x%llx",
+ (unsigned long long)msg.arg.pagefault.flags);
+ }
+
+ /* Update the shmem page in page cache before resuming the fault. */
+ SAFE_PWRITE(1, memfd, &z, 1, 0);
+
+ uffdio_continue.range.start =
+ msg.arg.pagefault.address & ~(page_size - 1);
+ uffdio_continue.range.len = page_size;
+
+ SAFE_IOCTL(uffd, UFFDIO_CONTINUE, &uffdio_continue);
+
+ close(uffd);
+ return NULL;
+}
+
+static void run(void)
+{
+ pthread_t thr;
+ struct uffdio_api uffdio_api = {};
+ struct uffdio_register uffdio_register;
+
+ set_pages();
+
+ uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
+
+ uffdio_api.api = UFFD_API;
+ uffdio_api.features = UFFD_FEATURE_MINOR_SHMEM;
+
+ SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);
+
+ if (!(uffdio_api.features & UFFD_FEATURE_MINOR_SHMEM))
+ tst_brk(TCONF, "UFFD_FEATURE_MINOR_SHMEM not supported");
+
+ uffdio_register.range.start = (unsigned long) page;
+ uffdio_register.range.len = page_size;
+ uffdio_register.mode = UFFDIO_REGISTER_MODE_MINOR;
+
+ SAFE_IOCTL(uffd, UFFDIO_REGISTER, &uffdio_register);
+
+ /*
+ * Drop PTEs while retaining the cached shmem page so the next access
+ * faults in MINOR mode.
+ */
+ if (madvise(page, page_size, MADV_DONTNEED) < 0)
+ tst_brk(TBROK | TERRNO, "madvise MADV_DONTNEED failed");
+
+ SAFE_PTHREAD_CREATE(&thr, NULL, (void *) handle_thread, NULL);
+
+ char c = page[0];
+
+ if (c == 'Z')
+ tst_res(TPASS, "Pagefault handled via UFFDIO_CONTINUE");
+ else
+ tst_res(TFAIL, "pagefault not handled via UFFDIO_CONTINUE, got '%c'", c);
+
+ SAFE_PTHREAD_JOIN(thr, NULL);
+ reset_pages();
+}
+
+static struct tst_test test = {
+ .test_all = run,
+ /*
+ * UFFDIO_CONTINUE is available since 5.13 but
+ * UFFD_FEATURE_MINOR_SHMEM appeared in 5.14
+ */
+ .min_kver = "5.14",
+ .needs_kconfigs = (const char *[]) {
+ "CONFIG_HAVE_ARCH_USERFAULTFD_WP=y",
+ NULL
+ },
+ .cleanup = reset_pages,
+};
--
2.53.0
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