2 files changed, 67 insertions, 0 deletions
diff --git a/src/init/lib/esemaphore.c b/src/init/lib/esemaphore.c
new file mode 100644
index 0000000..ac65b02
--- /dev/null
+++ b/src/init/lib/esemaphore.c
@@ -0,0 +1,55 @@
+#include <init/lib/esemaphore.h>
+#include <init/stdlib.h>
+#include <shared/flags.h>
+#include <shared/syscalls.h>
+
+void esem_signal(struct evil_sem *sem) {
+	_syscall_write(sem->signal, NULL, 0, 0);
+}
+
+void esem_wait(struct evil_sem *sem) {
+	_syscall_read(sem->wait, NULL, 0, 0);
+}
+
+struct evil_sem *esem_new(int value) {
+	handle_t ends_wait[2], ends_signal[2];
+	struct evil_sem *sem;
+
+	if (value < 0) return NULL;
+	if (_syscall_pipe(ends_wait, 0) < 0) return NULL;
+	if (_syscall_pipe(ends_signal, 0) < 0) goto fail_signal;
+	if (!(sem = malloc(sizeof *sem))) goto fail_malloc;
+
+	if (!_syscall_fork(FORK_NOREAP, NULL)) {
+		_syscall_close(ends_signal[1]);
+		while (_syscall_read(ends_signal[0], NULL, 0, 0) >= 0) {
+			if (!_syscall_fork(FORK_NOREAP, NULL)) {
+				_syscall_write(ends_wait[1], NULL, 0, 0);
+				_syscall_exit(0);
+			}
+		}
+		_syscall_exit(0);
+	}
+	_syscall_close(ends_signal[0]);
+	_syscall_close(ends_wait[1]);
+
+	sem->wait = ends_wait[0];
+	sem->signal = ends_signal[1];
+
+	while (value--) esem_signal(sem);
+	return sem;
+
+fail_malloc:
+	_syscall_close(ends_signal[0]);
+	_syscall_close(ends_signal[1]);
+fail_signal:
+	_syscall_close(ends_wait[0]);
+	_syscall_close(ends_wait[1]);
+	return NULL;
+}
+
+void esem_free(struct evil_sem *sem) {
+	_syscall_close(sem->wait);
+	_syscall_close(sem->signal);
+	free(sem);
+}
diff --git a/src/init/lib/esemaphore.h b/src/init/lib/esemaphore.h
new file mode 100644
index 0000000..e746bd7
--- /dev/null
+++ b/src/init/lib/esemaphore.h
@@ -0,0 +1,12 @@
+#pragma once
+#include <shared/types.h>
+
+struct evil_sem {
+	handle_t wait, signal;
+};
+
+void esem_signal(struct evil_sem *sem);
+void esem_wait(struct evil_sem *sem);
+
+struct evil_sem *esem_new(int value);
+void esem_free(struct evil_sem *sem);