Minor fix.

[bertos.git] / bertos / emul / switch_x86_64.s

diff --git a/bertos/emul/switch_x86_64.s b/bertos/emul/switch_x86_64.s
index 61859834cb95f50dfa41aa219fa6c2c5b584544f..ea76d2c98ed9d1246652f3aac29f1ad2152c0f19 100644 (file)
--- a/bertos/emul/switch_x86_64.s
+++ b/bertos/emul/switch_x86_64.s
@@ -26,45 +26,47 @@
  * invalidate any other reasons why the executable file might be covered by
  * the GNU General Public License.
  *
- * Copyright 2004 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
  * Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
- * This file is part of DevLib - See devlib/README for information.
  * -->
  *
- * \version $Id$
  * \author Bernie Innocenti <bernie@codewiz.org>
  *
- * \brief i386 context switch
+ * \brief x86_64 context switch
+ *
+ * x86_64 function call convention:
+ * --------------------------------
+ *  arguments           |  callee-saved      | extra caller-saved | return
+ * [callee-clobbered]   |                    | [callee-clobbered] |
+ * -------------------------------------------------------------------------
+ * rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11             | rax, rdx
+ *
+ *  [*]  In the frame-pointers case rbp must hold a base address for the
+ *       current stack frame.
+ *
+ * asm_switch_context() can be considered as a normal function call, so we need
+ * to save all the callee-clobbered registers minus the return registers.
  */
 
-/* I know it's ugly... */
-/* .intel_syntax */
-
-/* void AsmSwitchContext(void **new_sp, void **save_sp) */
-/*                       %rdi           %rsi            */
+/* void asm_switch_context(void **new_sp [%rdi], void **save_sp [%rsi]) */
 .globl asm_switch_context
 asm_switch_context:
-       pushq   %rax
-       pushq   %rbx
-       pushq   %rcx
-       pushq   %rdx
-       pushq   %rsi
-       pushq   %rdi
        pushq   %rbp
+       pushq   %rdi
+       pushq   %rsi
+       pushq   %rcx
+       pushq   %r8
+       pushq   %r9
+       pushq   %r10
+       pushq   %r11
        movq    %rsp,(%rsi)             /* *save_sp = rsp */
        movq    (%rdi),%rsp             /* rsp = *new_sp */
-       popq    %rbp
-       popq    %rdi
-       popq    %rsi
-       popq    %rdx
+       popq    %r11
+       popq    %r10
+       popq    %r9
+       popq    %r8
        popq    %rcx
-       popq    %rbx
-       popq    %rax
-       ret
-
-/* int asm_switch_version(void) */
-.globl asm_switch_version
-asm_switch_version:
-       mov     $1,%rax
+       popq    %rsi
+       popq    %rdi
+       popq    %rbp
        ret
-