user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/linux/pidfd.c

@@ -0,0 +1,74 @@
+#include <assert.h>
+#include <errno.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/pidfd.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main() {
+	int child = fork();
+
+	if(!child) {
+		sleep(1);
+		exit(42);
+	}
+
+	int pidfd = pidfd_open(child, 0);
+	assert(pidfd > 0);
+
+	int ret = lseek(pidfd, 0, SEEK_SET);
+	assert(ret == -1);
+	assert(errno == ESPIPE);
+
+	pid_t outpid = pidfd_getpid(pidfd);
+	assert(outpid == child);
+
+	struct pollfd pollfd;
+	pollfd.fd = pidfd;
+	pollfd.events = POLLIN;
+
+	int ready = poll(&pollfd, 1, 0);
+	assert(ready == 0);
+
+	ready = poll(&pollfd, 1, 2000);
+	if(ready == -1) {
+		perror("poll");
+		exit(EXIT_FAILURE);
+	}
+	assert(ready == 1);
+	assert(pollfd.revents == POLLIN);
+
+	siginfo_t info = {};
+	ret = waitid(P_PIDFD, pidfd, &info, WEXITED | WNOHANG);
+	assert(ret == 0);
+	assert(info.si_code == CLD_EXITED);
+	assert(info.si_pid == child);
+	assert(info.si_status == 42);
+
+	close(pidfd);
+
+	child = fork();
+
+	if(!child) {
+		sleep(10);
+	}
+
+	pidfd = pidfd_open(child, 0);
+	assert(pidfd > 0);
+
+	ret = pidfd_send_signal(pidfd, SIGKILL, NULL, 0);
+	assert(ret == 0);
+
+	memset(&info, 0, sizeof(info));
+	ret = waitid(P_PIDFD, pidfd, &info, WEXITED);
+	assert(ret == 0);
+	assert(info.si_code == CLD_KILLED);
+	assert(info.si_pid == child);
+	assert(info.si_status == SIGKILL);
+
+	return 0;
+}