memfd: test fd-sharing for memfds

Signed-off-by: Michał Mirosław <[email protected]>

test/zdtm/static/Makefile

@@ -257,6 +257,7 @@ TST_NOFILE	:=				\
 		memfd02				\
 		memfd02-hugetlb			\
 		memfd03				\
+		memfd04				\
 		shmemfd				\
 		shmemfd-priv			\
 		time				\

test/zdtm/static/memfd04.c

@@ -0,0 +1,71 @@
+#include <fcntl.h>
+#include <linux/memfd.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "memfd file descriptor sharing";
+const char *test_author = "Michał Mirosław <[email protected]>";
+
+static int _memfd_create(const char *name, unsigned int flags)
+{
+	return syscall(SYS_memfd_create, name, flags);
+}
+
+#ifndef KCMP_FILE
+#define KCMP_FILE 0
+#endif
+
+static int kcmp_fd(int fd1, int fd2)
+{
+	pid_t pid = getpid();
+	return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2);
+}
+
+#define CHECK(call) \
+	if (((call)) < 0) { \
+		fail(#call); \
+		return 1; \
+	}
+
+static int check_fd_sharing(int orig_fd, int dup_fd, int open_fd)
+{
+	int cmp1, cmp2;
+
+	CHECK(cmp1 = kcmp_fd(orig_fd, dup_fd));
+	if (cmp1)
+		fail("dup()ed fd is reported not the same as original");
+
+	CHECK(cmp2 = kcmp_fd(orig_fd, open_fd));
+	if (!cmp2)
+		fail("re-open()ed fd is reported the same as original");
+
+	return cmp1 || !cmp2;
+}
+
+int main(int argc, char *argv[])
+{
+	int orig_fd, dup_fd, open_fd;
+	char path[64];
+
+	test_init(argc, argv);
+
+	CHECK(orig_fd = _memfd_create("foo", 0));
+	CHECK(dup_fd = dup(orig_fd));
+	sprintf(path, "/proc/self/fd/%d", orig_fd);
+	CHECK(open_fd = open(path, O_RDWR));
+
+	if (check_fd_sharing(orig_fd, dup_fd, open_fd))
+		return 1;
+
+	test_daemon();
+	test_waitsig();
+
+	if (check_fd_sharing(orig_fd, dup_fd, open_fd))
+		return 1;
+
+	pass();
+	return 0;
+}