zdtm: Check pidfd fdinfo entry is consistent

Ensures that entries in /proc/<pid>/fdinfo/<pidfd> are same.

Signed-off-by: Bhavik Sachdev <b.sachdev1904@gmail.com>

test/zdtm/static/Makefile

@@ -53,6 +53,7 @@ TST_NOFILE	:=				\
 		shm				\
 		shm-mp				\
 		ptrace_sig			\
+		pidfd_self			\
 		pipe00				\
 		pipe01				\
 		pipe02				\

test/zdtm/static/pidfd_self.c

@@ -0,0 +1,140 @@
+#include <sys/syscall.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "Check pidfd /proc/self/fdinfo/<pidfd> entry remains consistent after checkpoint/restore\n";
+const char *test_author = "Bhavik Sachdev <b.sachdev1904@gmail.com>";
+
+struct pidfd_status {
+	unsigned int flags;
+	pid_t pid;
+};
+
+static int pidfd_open(pid_t pid, unsigned int flags)
+{
+	return syscall(__NR_pidfd_open, pid, flags);
+}
+
+static int pidfd_send_signal(int pidfd, int sig, siginfo_t* info, unsigned int flags)
+{
+	return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
+}
+
+static void show_pidfd(char *prefix, struct pidfd_status *s)
+{
+	test_msg("\n\t%s\n\tflags: 0%o\n\tpid: %d\n", prefix, s->flags, s->pid);
+}
+
+static int parse_self_fdinfo(int pidfd, struct pidfd_status *s)
+{
+	char buf[256];
+	int ret = -1;
+	FILE *f;
+
+	sprintf(buf, "/proc/self/fdinfo/%d", pidfd);
+	f = fopen(buf, "r");
+	if (!f) {
+		perror("Can't open /proc/self/fdinfo/ to parse");
+		return -1;
+	}
+
+	memset(s, 0, sizeof(*s));
+
+	/*
+	* flags:  file access mode (octal) 02000002 => [O_RDWR | O_CLOEXEC]
+	* pid:    the pid to which we have pidfd open
+	*/
+	while (fgets(buf, sizeof(buf), f)) {
+		if (!fgets(buf, sizeof(buf), f))
+			goto parse_err;
+
+		if (sscanf(buf, "flags: 0%o", &s->flags) != 1) {
+			goto parse_err;
+		}
+
+		if (!fgets(buf, sizeof(buf), f))
+			goto parse_err;
+		if (!fgets(buf, sizeof(buf), f))
+			goto parse_err;
+
+		if (!fgets(buf, sizeof(buf), f))
+			goto parse_err;
+
+		if (sscanf(buf, "Pid: %d", &s->pid) != 1)
+			goto parse_err;
+		ret = 0;
+		break;
+	}
+
+	if (ret)
+		goto parse_err;
+err:
+	fclose(f);
+	return ret;
+
+parse_err:
+	pr_perror("Format error");
+	goto err;
+}
+
+static int check_pidfd(int fd, struct pidfd_status *old)
+{
+	struct pidfd_status new;
+
+	if (parse_self_fdinfo(fd, &new))
+		return -1;
+
+	show_pidfd("restored", &new);
+
+	if (old->flags != new.flags || old->pid != new.pid)
+		return -1;
+
+	return 0;
+}
+
+int main(int argc, char* argv[])
+{
+	struct pidfd_status old;
+	int pidfd, ret;
+
+	test_init(argc, argv);
+
+	pidfd = pidfd_open(getpid(), 0);
+	if (pidfd < 0) {
+		pr_perror("pidfd_open failed");
+		return 1;
+	}
+
+	parse_self_fdinfo(pidfd, &old);
+
+	show_pidfd("old", &old);
+
+	if (pidfd_send_signal(pidfd, 0, NULL, 0)) {
+		pr_perror("Could not send signal");
+		return 1;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	ret = check_pidfd(pidfd, &old);
+	if (ret) {
+		fail();
+		goto err;
+	}
+
+	if (pidfd_send_signal(pidfd, 0, NULL, 0)) {
+		pr_perror("Could not send signal");
+		fail();
+		goto err;
+	}
+
+	pass();
+	close(pidfd);
+	return 0;
+err:
+	close(pidfd);
+	return 1;
+}