Kernel/LibC: Implement getppid

userspace/libraries/LibC/include/sys/syscall.h

@@ -41,6 +41,7 @@ __BEGIN_DECLS
 	O(SYS_KILL,				kill)			\
 	O(SYS_TCGETPGRP,		tcgetpgrp)		\
 	O(SYS_TCSETPGRP,		tcsetpgrp)		\
+	O(SYS_GET_PPID,			getppid)		\
 	O(SYS_GET_PID,			getpid)			\
 	O(SYS_GET_PGID,			getpgid)		\
 	O(SYS_SET_PGID,			setpgid)		\

userspace/libraries/LibC/unistd.cpp

@@ -489,6 +489,11 @@ error:
 	return ret;
 }
 
+pid_t getppid(void)
+{
+	return syscall(SYS_GET_PPID);
+}
+
 pid_t getpid(void)
 {
 	return syscall(SYS_GET_PID);