riscv64: port to C trampoline

README.md

@@ -25,7 +25,7 @@ target to do it.
 |    mips64    | ✓             |         | ✓                     |                   |
 |      ppc     | ✓             | ✓       |                       |                   |
 |     ppc64    | ✓             | ✓       |                       |                   |
-|    riscv64   | ✓             |         | ✓                     |                   |
+|    riscv64   | ✓             |         | ✓                     | ✓                 |
 |     s390x    | ✓             |         | ✓                     |                   |
 |      sh      | ✓             |         | ✓                     | ✓                 |
 |      x86     | ✓             |         | ✓                     | ✓                 |

arch/riscv64/defs.h

@@ -47,6 +47,9 @@
 
 #define PC_OFFSET	REG_OFFSET(REG_PC)
 
+#define FETCH_LINKPTR(dest) \
+	asm("mv	%0, s1" : "=rm" ((dest)))
+
 #include "common-defs.h"
 
 #endif

arch/riscv64/startcontext.S

@@ -1,26 +0,0 @@
-/*
- * 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 "defs.h"
-
-FUNC(libucontext_trampoline)
-	/* check for linked context */
-	beqz	s1, no_linked_context
-
-	/* if one is set, invoke it */
-	mv	a0, s1
-	jal	libucontext_setcontext
-
-	/* otherwise, exit. */
-no_linked_context:
-	tail	exit@plt
-END(libucontext_trampoline)

arch/riscv64/trampoline.c

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