ref: 8b0c12fda4008321ef8cbd61f9af24e0e6464e74
dir: /src/libc/syscall.h/
extern int _brk(void *); extern void _exit(int); extern int _close(int); extern int _getpid(void); extern int _kill(int, int); extern int _open(const char *, int, int); extern int _read(int, void *, size_t); extern int _unlink(const char *); extern int _write(int, void *, size_t);