arm: move to C trampoline

arch/arm/defs.h

@@ -5,6 +5,9 @@
 
 #define TYPE(__proc)
 
+#define FETCH_LINKPTR(dest) \
+	asm("movs    r0, %0" : "=rm" ((dest)))
+
 #include "common-defs.h"
 
 #endif

arch/arm/startcontext.S

@@ -1,23 +0,0 @@
-/*
- * Copyright (c) 2018 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.
- */
-
-.globl libucontext_trampoline;
-.fnstart
-.cantunwind
-	nop
-libucontext_trampoline:
-	/* get the proper context into position and test for NULL */
-	movs	r0, r4
-	bne	libucontext_setcontext@plt
-
-	/* we are returning into a null context, it seems, so maybe we should exit */
-	b	exit@plt

arch/arm/trampoline.c

@@ -0,0 +1,2 @@
+#include "defs.h"
+#include "common-trampoline.c"