libucontext_posix: add posixly-correct wrapper around libucontext

libucontext_posix.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <stddef.h>
+#include <libucontext/libucontext.h>
+
+#ifdef FREESTANDING
+# error libucontext_posix cannot be built in FREESTANDING mode.
+#endif
+
+int
+getcontext(libucontext_ucontext_t *ucp)
+{
+	if (sigprocmask(SIG_SETMASK, NULL, &ucp->uc_sigmask))
+		return -1;
+
+	return libucontext_getcontext(ucp);
+}
+
+int
+setcontext(const libucontext_ucontext_t *ucp)
+{
+	if (sigprocmask(SIG_SETMASK, &ucp->uc_sigmask, NULL))
+		return -1;
+
+	return libucontext_setcontext(ucp);
+}
+
+int
+swapcontext(libucontext_ucontext_t *oucp, const libucontext_ucontext_t *ucp)
+{
+	if (sigprocmask(SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask))
+		return -1;
+
+	return libucontext_swapcontext(oucp, ucp);
+}