tools/testing/selftests/kcmp/kcmp_test.c: add KCMP_EPOLL_TFD testing

KCMP's KCMP_EPOLL_TFD mode merged in commit 0791e3644e5ef2 ("kcmp: add
KCMP_EPOLL_TFD mode to compare epoll target files") we've had no selftest
for it yet (except in criu development list).  Thus add it.

Link: http://lkml.kernel.org/r/20170901151620.GK1898@uranus.lan
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/kcmp/kcmp_test.c

@@ -8,7 +8,6 @@
 #include <errno.h>
 #include <string.h>
 #include <fcntl.h>
-
 #include <linux/unistd.h>
 #include <linux/kcmp.h>
 
@@ -16,20 +15,28 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
+#include <sys/epoll.h>
 
 #include "../kselftest.h"
 
-static long sys_kcmp(int pid1, int pid2, int type, int fd1, int fd2)
+static long sys_kcmp(int pid1, int pid2, int type, unsigned long fd1, unsigned long fd2)
 {
 	return syscall(__NR_kcmp, pid1, pid2, type, fd1, fd2);
 }
 
+static const unsigned int duped_num = 64;
+
 int main(int argc, char **argv)
 {
 	const char kpath[] = "kcmp-test-file";
+	struct kcmp_epoll_slot epoll_slot;
+	struct epoll_event ev;
 	int pid1, pid2;
+	int pipefd[2];
 	int fd1, fd2;
+	int epollfd;
 	int status;
+	int fddup;
 
 	fd1 = open(kpath, O_RDWR | O_CREAT | O_TRUNC, 0644);
 	pid1 = getpid();
@@ -39,6 +46,37 @@ int main(int argc, char **argv)
 		ksft_exit_fail();
 	}
 
+	if (pipe(pipefd)) {
+		perror("Can't create pipe");
+		ksft_exit_fail();
+	}
+
+	epollfd = epoll_create1(0);
+	if (epollfd < 0) {
+		perror("epoll_create1 failed");
+		ksft_exit_fail();
+	}
+
+	memset(&ev, 0xff, sizeof(ev));
+	ev.events = EPOLLIN | EPOLLOUT;
+
+	if (epoll_ctl(epollfd, EPOLL_CTL_ADD, pipefd[0], &ev)) {
+		perror("epoll_ctl failed");
+		ksft_exit_fail();
+	}
+
+	fddup = dup2(pipefd[1], duped_num);
+	if (fddup < 0) {
+		perror("dup2 failed");
+		ksft_exit_fail();
+	}
+
+	if (epoll_ctl(epollfd, EPOLL_CTL_ADD, fddup, &ev)) {
+		perror("epoll_ctl failed");
+		ksft_exit_fail();
+	}
+	close(fddup);
+
 	pid2 = fork();
 	if (pid2 < 0) {
 		perror("fork failed");
@@ -95,6 +133,24 @@ int main(int argc, char **argv)
 			ksft_inc_pass_cnt();
 		}
 
+		/* Compare epoll target */
+		epoll_slot = (struct kcmp_epoll_slot) {
+			.efd	= epollfd,
+			.tfd	= duped_num,
+			.toff	= 0,
+		};
+		ret = sys_kcmp(pid1, pid1, KCMP_EPOLL_TFD, pipefd[1],
+			       (unsigned long)(void *)&epoll_slot);
+		if (ret) {
+			printf("FAIL: 0 expected but %d returned (%s)\n",
+				ret, strerror(errno));
+			ksft_inc_fail_cnt();
+			ret = -1;
+		} else {
+			printf("PASS: 0 returned as expected\n");
+			ksft_inc_pass_cnt();
+		}
+
 		ksft_print_cnts();
 
 		if (ret)