Add build system scaffolding and libc headers

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/libc/include/atomic.h b/lib/libc/include/atomic.h
new file mode 100644
index 00000000..94cd34db
--- /dev/null
+++ b/lib/libc/include/atomic.h
@@ -0,0 +1,23 @@
+#ifndef __LIBC_ATOMIC_H
+#define __LIBC_ATOMIC_H
+
+#include <stdatomic.h>
+
+#define LIBC_LOCK(__lock)   __libc_lock(&__lock)
+#define LIBC_UNLOCK(__lock) atomic_flag_clear(&__lock)
+
+static __inline void __libc_lock(volatile atomic_flag *lock)
+{
+	while (atomic_flag_test_and_set_explicit(lock, memory_order_acquire)) {
+		unsigned int spins = 1;
+		do {
+			for (unsigned int i = 0; i < spins; i++)
+				__asm__ volatile("pause");
+			if (spins < 64)
+				spins *= 2;
+		} while (atomic_flag_test_and_set_explicit(
+			lock, memory_order_relaxed));
+	}
+}
+
+#endif