README: Clarify limitations

README.md

@@ -127,8 +127,11 @@ int main(void)
 We execute "cat()". The first call succeeds. In the second, we get an exception, because
 the subprocess "cat()" was launched in violated the policy (missing "rpath" vow). 
 
-Naturally, there is a performance overhead. Certain challenges such pass-by-reference
-are yet to be solved.
+Naturally, there is a performance overhead. Certain challenges remain, such as the fact
+that being executed in a subprocess, we operate on copies, so handling references
+is not something that has been given much thought. There is also the fact
+that clone()ing from threads opens a can of worms. Hence, exile_launch()
+is best avoided in multi-threaded contexts.
 
 ## Status
 No release yet, experimental, API is unstable, builds will break on updates of this library.

exile.c

@@ -274,10 +274,12 @@ static struct syscall_vow_map exile_vow_map[] =
 	{EXILE_SYS(sched_getattr), EXILE_SYSCALL_VOW_SCHED},
 	{EXILE_SYS(renameat2), EXILE_SYSCALL_VOW_CPATH},
 	{EXILE_SYS(getrandom), EXILE_SYSCALL_VOW_STDIO},
+	{EXILE_SYS(memfd_create), EXILE_SYSCALL_VOW_STDIO},
 	{EXILE_SYS(execveat), EXILE_SYSCALL_VOW_EXEC},
 	{EXILE_SYS(mlock2), EXILE_SYSCALL_VOW_STDIO},
 	{EXILE_SYS(copy_file_range), EXILE_SYSCALL_VOW_STDIO},
 	{EXILE_SYS(statx), EXILE_SYSCALL_VOW_RPATH},
+	{EXILE_SYS(rseq), EXILE_SYSCALL_VOW_THREAD},
 	{EXILE_SYS(clone3), EXILE_SYSCALL_VOW_CLONE},
 	{EXILE_SYS(close_range), EXILE_SYSCALL_VOW_STDIO},
 	{EXILE_SYS(openat2), EXILE_SYSCALL_VOW_RPATH|EXILE_SYSCALL_VOW_WPATH},

exile.hpp

@@ -119,7 +119,7 @@ inline int do_clone(int (*clonefn)(void *), void *launcharg)
 }
 
 template<typename T, typename U, typename ... Args>
-typename std::enable_if_t<std::is_trivially_copyable_v<T>, T> exile_launch(struct exile_policy *policy, U fn, Args && ... args)
+typename std::enable_if_t<std::is_trivially_copyable_v<T> && !std::is_pointer_v<T>, T> exile_launch(struct exile_policy *policy, U fn, Args && ... args)
 {
 	size_t mapsize = sizeof(T);
 	T * sharedbuf =  (T *) mmap(NULL, mapsize , PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
@@ -145,7 +145,7 @@ typename std::enable_if_t<std::is_trivially_copyable_v<T>, T> exile_launch(struc
 
 
 template<typename T, typename U, typename ... Args>
-typename std::enable_if_t<!std::is_trivially_copyable_v<T> && std::is_copy_constructible_v<T>, T>
+typename std::enable_if_t<std::is_pointer_v<T> || (!std::is_trivially_copyable_v<T> && std::is_copy_constructible_v<T>), T>
 	exile_launch(struct exile_policy *policy, const std::function<size_t (const T &, char *, size_t)> &serializer, const std::function<T(const char *, size_t)> &deserializer, U fn, Args && ... args)
 {
 	size_t mapsize = EXILE_MMAP_SIZE;