io_uring provides a simple mechanism to test long-term, R/W GUP pins
-- via fixed buffers -- and can be used to verify that GUP pins stay
in sync with the pages in the page table even if a page would
temporarily get mapped R/O or concurrent fork() could accidentially
end up sharing pinned pages with the child.
Note that this essentially re-introduces local_config support that was
removed recently in commit 6f83d6c74ea5 ("Kselftests: remove support of
libhugetlbfs from kselftests").
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
tools/testing/selftests/vm/Makefile | 21 ++-
tools/testing/selftests/vm/anon_cow.c | 190 +++++++++++++++++++++
tools/testing/selftests/vm/check_config.sh | 31 ++++
3 files changed, 241 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/vm/check_config.sh
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index bc759534ec28..7931b84040ed 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -1,7 +1,9 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for vm selftests
-LOCAL_HDRS += $(top_srcdir)/mm/gup_test.h
+LOCAL_HDRS += $(selfdir)/vm/local_config.h $(top_srcdir)/mm/gup_test.h
+
+include local_config.mk
uname_M := $(shell uname -m 2>/dev/null || echo not)
MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/' -e 's/ppc64.*/ppc64/')
@@ -150,8 +152,25 @@ warn_32bit_failure:
endif
endif
+# ANON_COW_EXTRA_LIBS may get set in local_config.mk, or it may be left empty.
+$(OUTPUT)/anon_cow: LDLIBS += $(ANON_COW_EXTRA_LIBS)
+
$(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
$(OUTPUT)/ksm_tests: LDLIBS += -lnuma
$(OUTPUT)/migration: LDLIBS += -lnuma
+
+local_config.mk local_config.h: check_config.sh
+ /bin/sh ./check_config.sh $(CC)
+
+EXTRA_CLEAN += local_config.mk local_config.h
+
+ifeq ($(ANON_COW_EXTRA_LIBS),)
+all: warn_missing_liburing
+
+warn_missing_liburing:
+ @echo ; \
+ echo "Warning: missing liburing support. Some COW tests will be skipped." ; \
+ echo
+endif
diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c
index 06fd046bf1f2..369b3e15647d 100644
--- a/tools/testing/selftests/vm/anon_cow.c
+++ b/tools/testing/selftests/vm/anon_cow.c
@@ -19,6 +19,11 @@
#include <sys/mman.h>
#include <sys/wait.h>
+#include "local_config.h"
+#ifdef LOCAL_CONFIG_HAVE_LIBURING
+#include <liburing.h>
+#endif /* LOCAL_CONFIG_HAVE_LIBURING */
+
#include "../kselftest.h"
#include "vm_util.h"
@@ -334,6 +339,170 @@ static void test_vmsplice_after_fork(char *mem, size_t size)
do_test_vmsplice_in_parent(mem, size, false);
}
+#ifdef LOCAL_CONFIG_HAVE_LIBURING
+static void do_test_iouring(char *mem, size_t size, bool use_fork)
+{
+ struct comm_pipes comm_pipes;
+ struct io_uring_cqe *cqe;
+ struct io_uring_sqe *sqe;
+ struct io_uring ring;
+ size_t cur, total;
+ struct iovec iov;
+ char *buf, *tmp;
+ int ret, fd;
+ FILE *file;
+
+ ret = setup_comm_pipes(&comm_pipes);
+ if (ret) {
+ ksft_test_result_fail("pipe() failed\n");
+ return;
+ }
+
+ file = tmpfile();
+ if (!file) {
+ ksft_test_result_fail("tmpfile() failed\n");
+ goto close_comm_pipes;
+ }
+ fd = fileno(file);
+ assert(fd);
+
+ tmp = malloc(size);
+ if (!tmp) {
+ ksft_test_result_fail("malloc() failed\n");
+ goto close_file;
+ }
+
+ /* Skip on errors, as we might just lack kernel support. */
+ ret = io_uring_queue_init(1, &ring, 0);
+ if (ret < 0) {
+ ksft_test_result_skip("io_uring_queue_init() failed\n");
+ goto free_tmp;
+ }
+
+ /*
+ * Register the range as a fixed buffer. This will FOLL_WRITE | FOLL_PIN
+ * | FOLL_LONGTERM the range.
+ *
+ * Skip on errors, as we might just lack kernel support or might not
+ * have sufficient MEMLOCK permissions.
+ */
+ iov.iov_base = mem;
+ iov.iov_len = size;
+ ret = io_uring_register_buffers(&ring, &iov, 1);
+ if (ret) {
+ ksft_test_result_skip("io_uring_register_buffers() failed\n");
+ goto queue_exit;
+ }
+
+ if (use_fork) {
+ /*
+ * fork() and keep the child alive until we're done. Note that
+ * we expect the pinned page to not get shared with the child.
+ */
+ ret = fork();
+ if (ret < 0) {
+ ksft_test_result_fail("fork() failed\n");
+ goto unregister_buffers;
+ } else if (!ret) {
+ write(comm_pipes.child_ready[1], "0", 1);
+ while (read(comm_pipes.parent_ready[0], &buf, 1) != 1)
+ ;
+ exit(0);
+ }
+
+ while (read(comm_pipes.child_ready[0], &buf, 1) != 1)
+ ;
+ } else {
+ /*
+ * Map the page R/O into the page table. Enable softdirty
+ * tracking to stop the page from getting mapped R/W immediately
+ * again by mprotect() optimizations. Note that we don't have an
+ * easy way to test if that worked (the pagemap does not export
+ * if the page is mapped R/O vs. R/W).
+ */
+ ret = mprotect(mem, size, PROT_READ);
+ clear_softdirty();
+ ret |= mprotect(mem, size, PROT_READ | PROT_WRITE);
+ if (ret) {
+ ksft_test_result_fail("mprotect() failed\n");
+ goto unregister_buffers;
+ }
+ }
+
+ /*
+ * Modify the page and write page content as observed by the fixed
+ * buffer pin to the file so we can verify it.
+ */
+ memset(mem, 0xff, size);
+ sqe = io_uring_get_sqe(&ring);
+ if (!sqe) {
+ ksft_test_result_fail("io_uring_get_sqe() failed\n");
+ goto quit_child;
+ }
+ io_uring_prep_write_fixed(sqe, fd, mem, size, 0, 0);
+
+ ret = io_uring_submit(&ring);
+ if (ret < 0) {
+ ksft_test_result_fail("io_uring_submit() failed\n");
+ goto quit_child;
+ }
+
+ ret = io_uring_wait_cqe(&ring, &cqe);
+ if (ret < 0) {
+ ksft_test_result_fail("io_uring_wait_cqe() failed\n");
+ goto quit_child;
+ }
+
+ if (cqe->res != size) {
+ ksft_test_result_fail("write_fixed failed\n");
+ goto quit_child;
+ }
+ io_uring_cqe_seen(&ring, cqe);
+
+ /* Read back the file content to the temporary buffer. */
+ total = 0;
+ while (total < size) {
+ cur = pread(fd, tmp + total, size - total, total);
+ if (cur < 0) {
+ ksft_test_result_fail("pread() failed\n");
+ goto quit_child;
+ }
+ total += cur;
+ }
+
+ /* Finally, check if we read what we expected. */
+ ksft_test_result(!memcmp(mem, tmp, size),
+ "Longterm R/W pin is reliable\n");
+
+quit_child:
+ if (use_fork) {
+ write(comm_pipes.parent_ready[1], "0", 1);
+ wait(&ret);
+ }
+unregister_buffers:
+ io_uring_unregister_buffers(&ring);
+queue_exit:
+ io_uring_queue_exit(&ring);
+free_tmp:
+ free(tmp);
+close_file:
+ fclose(file);
+close_comm_pipes:
+ close_comm_pipes(&comm_pipes);
+}
+
+static void test_iouring_ro(char *mem, size_t size)
+{
+ do_test_iouring(mem, size, false);
+}
+
+static void test_iouring_fork(char *mem, size_t size)
+{
+ do_test_iouring(mem, size, true);
+}
+
+#endif /* LOCAL_CONFIG_HAVE_LIBURING */
+
typedef void (*test_fn)(char *mem, size_t size);
static void do_run_with_base_page(test_fn fn, bool swapout)
@@ -660,6 +829,27 @@ static const struct test_case test_cases[] = {
"vmsplice() + unmap in parent after fork()",
test_vmsplice_after_fork,
},
+#ifdef LOCAL_CONFIG_HAVE_LIBURING
+ /*
+ * Take a R/W longterm pin and then map the page R/O into the page
+ * table to trigger a write fault on next access. When modifying the
+ * page, the page content must be visible via the pin.
+ */
+ {
+ "R/O-mapping a page registered as iouring fixed buffer",
+ test_iouring_ro,
+ },
+ /*
+ * Take a R/W longterm pin and then fork() a child. When modifying the
+ * page, the page content must be visible via the pin. We expect the
+ * pinned page to not get shared with the child.
+ */
+ {
+ "fork() with an iouring fixed buffer",
+ test_iouring_fork,
+ },
+
+#endif /* LOCAL_CONFIG_HAVE_LIBURING */
};
static void run_test_case(struct test_case const *test_case)
diff --git a/tools/testing/selftests/vm/check_config.sh b/tools/testing/selftests/vm/check_config.sh
new file mode 100644
index 000000000000..9a44c6520925
--- /dev/null
+++ b/tools/testing/selftests/vm/check_config.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Probe for libraries and create header files to record the results. Both C
+# header files and Makefile include fragments are created.
+
+OUTPUT_H_FILE=local_config.h
+OUTPUT_MKFILE=local_config.mk
+
+tmpname=$(mktemp)
+tmpfile_c=${tmpname}.c
+tmpfile_o=${tmpname}.o
+
+# liburing
+echo "#include <sys/types.h>" > $tmpfile_c
+echo "#include <liburing.h>" >> $tmpfile_c
+echo "int func(void) { return 0; }" >> $tmpfile_c
+
+CC=${1:?"Usage: $0 <compiler> # example compiler: gcc"}
+$CC -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1
+
+if [ -f $tmpfile_o ]; then
+ echo "#define LOCAL_CONFIG_HAVE_LIBURING 1" > $OUTPUT_H_FILE
+ echo "ANON_COW_EXTRA_LIBS = -luring" > $OUTPUT_MKFILE
+else
+ echo "// No liburing support found" > $OUTPUT_H_FILE
+ echo "# No liburing support found, so:" > $OUTPUT_MKFILE
+ echo "ANON_COW_EXTRA_LIBS = " >> $OUTPUT_MKFILE
+fi
+
+rm ${tmpname}.*
--
2.37.3
