On some old kernels (think RHEL-7) __NR_userfaultfd may not be defined
on certain arches, even though the <linux/userfaultfd.h> header is
available. To avoid build errors in such environments, abstract the
userfaultfd syscall into a helper function and make it fail with ENOSYS
when __NR_userfaultfd is not defined.
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
tests/userfaultfd/userfaultfd.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/tests/userfaultfd/userfaultfd.c b/tests/userfaultfd/userfaultfd.c
index a283a83..dd3a9f3 100644
--- a/tests/userfaultfd/userfaultfd.c
+++ b/tests/userfaultfd/userfaultfd.c
@@ -19,7 +19,7 @@ int page_size;
void *fault_handler_thread(void *arg)
{
- long uffd = (long)arg;
+ int uffd = (int)(intptr_t)arg;
struct uffd_msg msg = {0};
struct uffdio_copy uffdio_copy = {0};
ssize_t nread;
@@ -83,6 +83,16 @@ void *fault_handler_thread(void *arg)
}
}
+int syscall_userfaultfd(int flags)
+{
+#ifdef __NR_userfaultfd
+ return (int)syscall(__NR_userfaultfd, flags);
+#else
+ errno = ENOSYS;
+ return -1;
+#endif
+}
+
int main (int argc, char *argv[])
{
char *addr;
@@ -92,7 +102,7 @@ int main (int argc, char *argv[])
pthread_t thr; // ID of thread that handles page faults
ssize_t ret;
- long uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+ int uffd = syscall_userfaultfd(O_CLOEXEC | O_NONBLOCK);
if (uffd < 0) {
if (errno == ENOSYS) {
return 8;
@@ -159,7 +169,8 @@ int main (int argc, char *argv[])
}
// Create a thread that will process the userfaultfd events
- ret = pthread_create(&thr, NULL, fault_handler_thread, (void *) uffd);
+ ret = pthread_create(&thr, NULL, fault_handler_thread,
+ (void *)(intptr_t)uffd);
if (ret != 0) {
errno = ret;
perror("pthread_create");
--
2.30.2
