zdtm: Check dead pidfd is restored correctly

signed-off-by: Bhavik Sachdev <[email protected]>

test/zdtm/static/Makefile

@@ -54,6 +54,7 @@ TST_NOFILE	:=				\
 		shm-mp				\
 		ptrace_sig			\
 		pidfd_self			\
+		pidfd_dead			\
 		pidfd_child			\
 		pidfd_kill			\
 		pipe00				\

test/zdtm/static/pidfd_dead.c

@@ -0,0 +1,95 @@
+#include <sys/types.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <sys/utsname.h>
+#include <fcntl.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "Check C/R of pidfds that point to dead processes\n";
+const char *test_author = "Bhavik Sachdev <[email protected]>";
+
+static int pidfd_open(pid_t pid, unsigned int flags)
+{
+	return syscall(SYS_pidfd_open, pid, flags);
+}
+
+static int pidfd_send_signal(int pidfd, int sig, siginfo_t* info, unsigned int flags)
+{
+	return syscall(SYS_pidfd_send_signal, pidfd, sig, info, flags);
+}
+
+static struct utsname buf;
+
+int main(int argc, char* argv[])
+{
+	int child, ret;
+	int pidfd_one, pidfd_two;
+	unsigned major, minor;
+	struct statx stat_one, stat_two;
+
+	test_init(argc, argv);
+
+	ret = uname(&buf);
+	if (ret)
+		return 1;
+
+	if (sscanf(buf.release, "%u.%u", &major, &minor) != 2)
+		return 1;
+
+	if ((major < 6) || (minor < 9)) {
+		test_msg("statx on pidfd is only supported on 6.9 and above..\n");
+		test_daemon();
+		test_waitsig();
+		pass();
+		return 0;
+	}
+
+	child = fork();
+	if (child < 0) {
+		pr_perror("fork");
+		return 1;
+	} else if (child == 0) {
+		while(1);
+	}
+
+	pidfd_one = pidfd_open(child, 0);
+	if (pidfd_one < 0) {
+		pr_perror("pidfd_open");
+		return 1;
+	}
+
+	pidfd_two = pidfd_open(child, 0);
+	if (pidfd_two < 0) {
+		pr_perror("pidfd_open");
+		return 1;
+	}
+
+	if (pidfd_send_signal(pidfd_one, SIGKILL, NULL, 0)) {
+		pr_perror("pidfd_send_signal");
+		return 1;
+	}
+	wait(NULL);
+
+	test_daemon();
+	test_waitsig();
+
+	/*
+	* After linux 6.9 we can compare inode numbers
+	* to determine if two pidfds point to the same process.
+	* While the inode number may change before and after C/R
+	* pidfds pointing to the same pid should have the same inode number.
+	*/
+	statx(pidfd_one, "", AT_EMPTY_PATH, STATX_ALL, &stat_one);
+	statx(pidfd_two, "", AT_EMPTY_PATH, STATX_ALL, &stat_two);
+	if (stat_one.stx_ino == stat_two.stx_ino)
+		pass();
+	else
+		fail();
+
+	close(pidfd_one);
+	close(pidfd_two);
+	return 0;
+}