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Subject[PATCH v2 2/2] userfaultfd: selftest: Add tests for UFFD_FEATURE_SIGBUS feature
Date
This patch adds tests for UFFD_FEATURE_SIGBUS feature. The
tests will verify signal delivery instead of userfault events.
Also, test use of UFFDIO_COPY to allocate memory and retry
accessing monitored area after signal delivery.

This patch also fixes a bug in uffd_poll_thread() where 'uffd'
is leaked.

Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
---
Change log

v2:
- Added comments to explain the tests.
- Fixed test to fail immediately if signal repeats.
- Addressed other review comments.

v1: https://lkml.org/lkml/2017/7/26/101
---
tools/testing/selftests/vm/userfaultfd.c | 127 +++++++++++++++++++++++++++++-
1 files changed, 124 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 1eae79a..3976d7a 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -66,6 +66,7 @@
#include <sys/wait.h>
#include <pthread.h>
#include <linux/userfaultfd.h>
+#include <setjmp.h>

#ifdef __NR_userfaultfd

@@ -408,6 +409,7 @@ static int copy_page(int ufd, unsigned long offset)
userfaults++;
break;
case UFFD_EVENT_FORK:
+ close(uffd);
uffd = msg.arg.fork.ufd;
pollfd[0].fd = uffd;
break;
@@ -572,6 +574,17 @@ static int userfaultfd_open(int features)
return 0;
}

+sigjmp_buf jbuf, *sigbuf;
+
+static void sighndl(int sig, siginfo_t *siginfo, void *ptr)
+{
+ if (sig == SIGBUS) {
+ if (sigbuf)
+ siglongjmp(*sigbuf, 1);
+ abort();
+ }
+}
+
/*
* For non-cooperative userfaultfd test we fork() a process that will
* generate pagefaults, will mremap the area monitored by the
@@ -585,19 +598,59 @@ static int userfaultfd_open(int features)
* The release of the pages currently generates event for shmem and
* anonymous memory (UFFD_EVENT_REMOVE), hence it is not checked
* for hugetlb.
+ * For signal test(UFFD_FEATURE_SIGBUS), signal_test = 1, we register
+ * monitored area, generate pagefaults and test that signal is delivered.
+ * Use UFFDIO_COPY to allocate missing page and retry. For signal_test = 2
+ * test robustness use case - we release monitored area, fork a process
+ * that will generate pagefaults and verify signal is generated.
+ * This also tests UFFD_FEATURE_EVENT_FORK event along with the signal
+ * feature. Using monitor thread, verify no userfault events are generated.
*/
-static int faulting_process(void)
+static int faulting_process(int signal_test)
{
unsigned long nr;
unsigned long long count;
unsigned long split_nr_pages;
+ unsigned long lastnr;
+ struct sigaction act;
+ unsigned long signalled = 0, sig_repeats = 0;

if (test_type != TEST_HUGETLB)
split_nr_pages = (nr_pages + 1) / 2;
else
split_nr_pages = nr_pages;

+ if (signal_test) {
+ sigbuf = &jbuf;
+ memset(&act, 0, sizeof(act));
+ act.sa_sigaction = sighndl;
+ act.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGBUS, &act, 0)) {
+ perror("sigaction");
+ return 1;
+ }
+ lastnr = (unsigned long)-1;
+ }
+
for (nr = 0; nr < split_nr_pages; nr++) {
+ if (signal_test) {
+ if (sigsetjmp(*sigbuf, 1) != 0) {
+ if (nr == lastnr) {
+ sig_repeats++;
+ break;
+ }
+
+ lastnr = nr;
+ if (signal_test == 1) {
+ if (copy_page(uffd, nr * page_size))
+ signalled++;
+ } else {
+ signalled++;
+ continue;
+ }
+ }
+ }
+
count = *area_count(area_dst, nr);
if (count != count_verify[nr]) {
fprintf(stderr,
@@ -607,6 +660,9 @@ static int faulting_process(void)
}
}

+ if (signal_test)
+ return !(signalled == split_nr_pages && sig_repeats == 0);
+
if (test_type == TEST_HUGETLB)
return 0;

@@ -761,7 +817,7 @@ static int userfaultfd_events_test(void)
perror("fork"), exit(1);

if (!pid)
- return faulting_process();
+ return faulting_process(0);

waitpid(pid, &err, 0);
if (err)
@@ -778,6 +834,70 @@ static int userfaultfd_events_test(void)
return userfaults != nr_pages;
}

+static int userfaultfd_sig_test(void)
+{
+ struct uffdio_register uffdio_register;
+ unsigned long expected_ioctls;
+ unsigned long userfaults;
+ pthread_t uffd_mon;
+ int err, features;
+ pid_t pid;
+ char c;
+
+ printf("testing signal delivery: ");
+ fflush(stdout);
+
+ if (uffd_test_ops->release_pages(area_dst))
+ return 1;
+
+ features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
+ if (userfaultfd_open(features) < 0)
+ return 1;
+ fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
+
+ uffdio_register.range.start = (unsigned long) area_dst;
+ uffdio_register.range.len = nr_pages * page_size;
+ uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
+ if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+ fprintf(stderr, "register failure\n"), exit(1);
+
+ expected_ioctls = uffd_test_ops->expected_ioctls;
+ if ((uffdio_register.ioctls & expected_ioctls) !=
+ expected_ioctls)
+ fprintf(stderr,
+ "unexpected missing ioctl for anon memory\n"),
+ exit(1);
+
+ if (faulting_process(1))
+ fprintf(stderr, "faulting process failed\n"), exit(1);
+
+ if (uffd_test_ops->release_pages(area_dst))
+ return 1;
+
+ if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, NULL))
+ perror("uffd_poll_thread create"), exit(1);
+
+ pid = fork();
+ if (pid < 0)
+ perror("fork"), exit(1);
+
+ if (!pid)
+ exit(faulting_process(2));
+
+ waitpid(pid, &err, 0);
+ if (err)
+ fprintf(stderr, "faulting process failed\n"), exit(1);
+
+ if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+ perror("pipe write"), exit(1);
+ if (pthread_join(uffd_mon, (void **)&userfaults))
+ return 1;
+
+ printf("done\n");
+ printf(" Signal test userfaults: %ld\n", userfaults);
+ close(uffd);
+ return userfaults != 0;
+}
static int userfaultfd_stress(void)
{
void *area;
@@ -946,7 +1066,8 @@ static int userfaultfd_stress(void)
return err;

close(uffd);
- return userfaultfd_zeropage_test() || userfaultfd_events_test();
+ return userfaultfd_zeropage_test() || userfaultfd_sig_test()
+ || userfaultfd_events_test();
}

/*
--
1.7.1
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