--- Libc/Libc-997.90.3/sys/fork.c
+++ Libc/Libc-1669.40.2/sys/fork.c
@@ -24,60 +24,94 @@
 #include <sys/stat.h>
 #include <errno.h>
 #include <TargetConditionals.h>
+#include <stdbool.h>
 
-#if TARGET_IPHONE_SIMULATOR
-extern pid_t (*_host_fork)(void);
-#else
+#include "_libc_init.h" // for libc_atfork_helper
+
 extern pid_t __fork(void);
-#endif
+extern pid_t __vfork(void);
 
 static void (*_libSystem_atfork_prepare)(void) = 0;
 static void (*_libSystem_atfork_parent)(void) = 0;
 static void (*_libSystem_atfork_child)(void) = 0;
+static void (*_libSystem_atfork_prepare_v2)(unsigned int flags, ...) = 0;
+static void (*_libSystem_atfork_parent_v2)(unsigned int flags, ...) = 0;
+static void (*_libSystem_atfork_child_v2)(unsigned int flags, ...) = 0;
 
-#if !TARGET_IPHONE_SIMULATOR
 __private_extern__
-#endif
-void _libc_fork_init(void (*prepare)(void), void (*parent)(void), void (*child)(void))
+void _libc_fork_init(const struct _libc_functions *funcs)
 {
-	_libSystem_atfork_prepare = prepare;
-	_libSystem_atfork_parent = parent;
-	_libSystem_atfork_child = child;
+	if (funcs->version >= 2) {
+		_libSystem_atfork_prepare_v2 = funcs->atfork_prepare_v2;
+		_libSystem_atfork_parent_v2 = funcs->atfork_parent_v2;
+		_libSystem_atfork_child_v2 = funcs->atfork_child_v2;
+	} else {
+		_libSystem_atfork_prepare = funcs->atfork_prepare;
+		_libSystem_atfork_parent = funcs->atfork_parent;
+		_libSystem_atfork_child = funcs->atfork_child;
+	}
 }
 
-/*
- * fork stub
- */
+static inline __attribute__((always_inline))
+pid_t
+_do_fork(bool libsystem_atfork_handlers_only)
+{
+	int ret;
+
+	int flags = libsystem_atfork_handlers_only ? LIBSYSTEM_ATFORK_HANDLERS_ONLY_FLAG : 0;
+
+	if (_libSystem_atfork_prepare_v2) {
+		_libSystem_atfork_prepare_v2(flags);
+	} else {
+		_libSystem_atfork_prepare();
+	}
+	// Reader beware: this __fork() call is yet another wrapper around the actual syscall
+	// and lives inside libsyscall. The fork syscall needs some cuddling by asm before it's
+	// allowed to see the big wide C world.
+	ret = __fork();
+	if (-1 == ret)
+	{
+		// __fork already set errno for us
+		if (_libSystem_atfork_parent_v2) {
+			_libSystem_atfork_parent_v2(flags);
+		} else {
+			_libSystem_atfork_parent();
+		}
+		return ret;
+	}
+
+	if (0 == ret)
+	{
+		// We're the child in this part.
+		if (_libSystem_atfork_child_v2) {
+			_libSystem_atfork_child_v2(flags);
+		} else {
+			_libSystem_atfork_child();
+		}
+		return 0;
+	}
+
+	if (_libSystem_atfork_parent_v2) {
+		_libSystem_atfork_parent_v2(flags);
+	} else {
+		_libSystem_atfork_parent();
+	}
+	return ret;
+}
+
 pid_t
 fork(void)
 {
-	int ret;
-	
-	_libSystem_atfork_prepare();
-	// Reader beware: this __fork() call is yet another wrapper around the actual syscall
-	// and lives inside libsyscall. The fork syscall needs some cuddling by asm before it's
-	// allowed to see the big wide C world.
-#if TARGET_IPHONE_SIMULATOR
-	// _host_fork is yet another layer of wrapping that lives in the simulator's libSystem
-	ret = _host_fork();
-#else
-	ret = __fork();
-#endif
-	if (-1 == ret)
-	{
-		// __fork already set errno for us
-		_libSystem_atfork_parent();
-		return ret;
-	}
-	
-	if (0 == ret)
-	{
-		// We're the child in this part.
-		_libSystem_atfork_child();
-		return 0;
-	}
-	
-	_libSystem_atfork_parent();
-	return ret;
+	return _do_fork(false);
 }
 
+pid_t
+vfork(void)
+{
+	// vfork() is now just fork().
+	// Skip the API pthread_atfork handlers, but do call our own
+	// Libsystem_atfork handlers. People are abusing vfork in ways where
+	// it matters, e.g. tcsh does all kinds of stuff after the vfork. Sigh.
+	return _do_fork(true);
+}
+