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Message-Id: <20220927110120.106906-8-david@redhat.com>
Date: Tue, 27 Sep 2022 13:01:20 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
David Hildenbrand <david@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>,
Jason Gunthorpe <jgg@...dia.com>,
John Hubbard <jhubbard@...dia.com>,
Nadav Amit <namit@...are.com>, Peter Xu <peterx@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Vlastimil Babka <vbabka@...e.cz>,
Mike Rapoport <rppt@...nel.org>,
Christoph von Recklinghausen <crecklin@...hat.com>,
Don Dutile <ddutile@...hat.com>
Subject: [PATCH v1 7/7] selftests/vm: anon_cow: add R/O longterm tests via gup_test
Let's trigger a R/O longterm pin on three cases of R/O mapped anonymous
pages:
* exclusive (never shared)
* shared (child still alive)
* previously shared (child no longer alive)
... and make sure that the pin is reliable: whatever we write via the page
tables has to be observable via the pin.
Signed-off-by: David Hildenbrand <david@...hat.com>
---
tools/testing/selftests/vm/anon_cow.c | 210 ++++++++++++++++++++++++++
1 file changed, 210 insertions(+)
diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c
index 369b3e15647d..055bf13a05d9 100644
--- a/tools/testing/selftests/vm/anon_cow.c
+++ b/tools/testing/selftests/vm/anon_cow.c
@@ -17,6 +17,7 @@
#include <dirent.h>
#include <assert.h>
#include <sys/mman.h>
+#include <sys/ioctl.h>
#include <sys/wait.h>
#include "local_config.h"
@@ -24,6 +25,7 @@
#include <liburing.h>
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
+#include "../../../../mm/gup_test.h"
#include "../kselftest.h"
#include "vm_util.h"
@@ -32,6 +34,7 @@ static int pagemap_fd;
static size_t thpsize;
static int nr_hugetlbsizes;
static size_t hugetlbsizes[10];
+static int gup_fd;
static void detect_thpsize(void)
{
@@ -503,6 +506,170 @@ static void test_iouring_fork(char *mem, size_t size)
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
+enum ro_pin_test {
+ RO_PIN_TEST_SHARED,
+ RO_PIN_TEST_PREVIOUSLY_SHARED,
+ RO_PIN_TEST_RO_EXCLUSIVE,
+};
+
+static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test,
+ bool fast)
+{
+ struct pin_longterm_test args;
+ struct comm_pipes comm_pipes;
+ char *tmp, buf;
+ __u64 tmp_val;
+ int ret;
+
+ if (gup_fd < 0) {
+ ksft_test_result_skip("gup_test not available\n");
+ return;
+ }
+
+ tmp = malloc(size);
+ if (!tmp) {
+ ksft_test_result_fail("malloc() failed\n");
+ return;
+ }
+
+ ret = setup_comm_pipes(&comm_pipes);
+ if (ret) {
+ ksft_test_result_fail("pipe() failed\n");
+ goto free_tmp;
+ }
+
+ switch (test) {
+ case RO_PIN_TEST_SHARED:
+ case RO_PIN_TEST_PREVIOUSLY_SHARED:
+ /*
+ * Share the pages with our child. As the pages are not pinned,
+ * this should just work.
+ */
+ ret = fork();
+ if (ret < 0) {
+ ksft_test_result_fail("fork() failed\n");
+ goto close_comm_pipes;
+ } else if (!ret) {
+ write(comm_pipes.child_ready[1], "0", 1);
+ while (read(comm_pipes.parent_ready[0], &buf, 1) != 1)
+ ;
+ exit(0);
+ }
+
+ /* Wait until our child is ready. */
+ while (read(comm_pipes.child_ready[0], &buf, 1) != 1)
+ ;
+
+ if (test == RO_PIN_TEST_PREVIOUSLY_SHARED) {
+ /*
+ * Tell the child to quit now and wait until it quit.
+ * The pages should now be mapped R/O into our page
+ * tables, but they are no longer shared.
+ */
+ write(comm_pipes.parent_ready[1], "0", 1);
+ wait(&ret);
+ if (!WIFEXITED(ret))
+ ksft_print_msg("[INFO] wait() failed\n");
+ }
+ break;
+ case RO_PIN_TEST_RO_EXCLUSIVE:
+ /*
+ * 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 close_comm_pipes;
+ }
+ break;
+ default:
+ assert(false);
+ }
+
+ /* Take a R/O pin. This should trigger unsharing. */
+ args.addr = (__u64)mem;
+ args.size = size;
+ args.flags = fast ? PIN_LONGTERM_TEST_FLAG_USE_FAST : 0;
+ ret = ioctl(gup_fd, PIN_LONGTERM_TEST_START, &args);
+ if (ret) {
+ if (errno == EINVAL)
+ ksft_test_result_skip("PIN_LONGTERM_TEST_START failed\n");
+ else
+ ksft_test_result_fail("PIN_LONGTERM_TEST_START failed\n");
+ goto wait;
+ }
+
+ /* Modify the page. */
+ memset(mem, 0xff, size);
+
+ /*
+ * Read back the content via the pin to the temporary buffer and
+ * test if we observed the modification.
+ */
+ tmp_val = (__u64)tmp;
+ ret = ioctl(gup_fd, PIN_LONGTERM_TEST_READ, &tmp_val);
+ if (ret)
+ ksft_test_result_fail("PIN_LONGTERM_TEST_READ failed\n");
+ else
+ ksft_test_result(!memcmp(mem, tmp, size),
+ "Longterm R/O pin is reliable\n");
+
+ ret = ioctl(gup_fd, PIN_LONGTERM_TEST_STOP);
+ if (ret)
+ ksft_print_msg("[INFO] PIN_LONGTERM_TEST_STOP failed\n");
+wait:
+ switch (test) {
+ case RO_PIN_TEST_SHARED:
+ write(comm_pipes.parent_ready[1], "0", 1);
+ wait(&ret);
+ if (!WIFEXITED(ret))
+ ksft_print_msg("[INFO] wait() failed\n");
+ break;
+ default:
+ break;
+ }
+close_comm_pipes:
+ close_comm_pipes(&comm_pipes);
+free_tmp:
+ free(tmp);
+}
+
+static void test_ro_pin_on_shared(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_SHARED, false);
+}
+
+static void test_ro_fast_pin_on_shared(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_SHARED, true);
+}
+
+static void test_ro_pin_on_ro_previously_shared(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_PREVIOUSLY_SHARED, false);
+}
+
+static void test_ro_fast_pin_on_ro_previously_shared(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_PREVIOUSLY_SHARED, true);
+}
+
+static void test_ro_pin_on_ro_exclusive(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_RO_EXCLUSIVE, false);
+}
+
+static void test_ro_fast_pin_on_ro_exclusive(char *mem, size_t size)
+{
+ do_test_ro_pin(mem, size, RO_PIN_TEST_RO_EXCLUSIVE, true);
+}
+
typedef void (*test_fn)(char *mem, size_t size);
static void do_run_with_base_page(test_fn fn, bool swapout)
@@ -850,6 +1017,48 @@ static const struct test_case test_cases[] = {
},
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
+ /*
+ * Take a R/O longterm pin on a R/O-mapped shared anonymous page.
+ * When modifying the page via the page table, the page content change
+ * must be visible via the pin.
+ */
+ {
+ "R/O GUP pin on R/O-mapped shared page",
+ test_ro_pin_on_shared,
+ },
+ /* Same as above, but using GUP-fast. */
+ {
+ "R/O GUP-fast pin on R/O-mapped shared page",
+ test_ro_fast_pin_on_shared,
+ },
+ /*
+ * Take a R/O longterm pin on a R/O-mapped exclusive anonymous page that
+ * was previously shared. When modifying the page via the page table,
+ * the page content change must be visible via the pin.
+ */
+ {
+ "R/O GUP pin on R/O-mapped previously-shared page",
+ test_ro_pin_on_ro_previously_shared,
+ },
+ /* Same as above, but using GUP-fast. */
+ {
+ "R/O GUP-fast pin on R/O-mapped previously-shared page",
+ test_ro_fast_pin_on_ro_previously_shared,
+ },
+ /*
+ * Take a R/O longterm pin on a R/O-mapped exclusive anonymous page.
+ * When modifying the page via the page table, the page content change
+ * must be visible via the pin.
+ */
+ {
+ "R/O GUP pin on R/O-mapped exclusive page",
+ test_ro_pin_on_ro_exclusive,
+ },
+ /* Same as above, but using GUP-fast. */
+ {
+ "R/O GUP-fast pin on R/O-mapped exclusive page",
+ test_ro_fast_pin_on_ro_exclusive,
+ },
};
static void run_test_case(struct test_case const *test_case)
@@ -902,6 +1111,7 @@ int main(int argc, char **argv)
ksft_print_header();
ksft_set_plan(nr_test_cases * tests_per_test_case());
+ gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
if (pagemap_fd < 0)
ksft_exit_fail_msg("opening pagemap failed\n");
--
2.37.3
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