X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Femul%2Fswitch_i386.S;h=f00d447c1467093ed74dedc8c5722099efe0566c;hb=7911a6f01bc8a19f220f98e2fdc8595f65996853;hp=39eb31d5f734e243ff44d28425b0991cbec28987;hpb=4cc44c9888a0336b9d01121ec0b7ad95f4a76195;p=bertos.git

diff --git a/bertos/emul/switch_i386.S b/bertos/emul/switch_i386.S
index 39eb31d5..f00d447c 100644
--- a/bertos/emul/switch_i386.S
+++ b/bertos/emul/switch_i386.S
@@ -1,55 +1,69 @@
-/*!
+/**
  * \file
  * <!--
- * Copyright 2004 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.
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
  * -->
  *
+ * \author Bernie Innocenti <bernie@codewiz.org>
+ *
  * \brief i386 context switch
  *
- * \version $Id$
+ * x86 function calling convention:
+ * --------------------------------
+ *  arguments         | callee-saved        | extra caller-saved | return
+ * [callee-clobbered] |                     | [callee-clobbered] |
+ * -------------------------------------------------------------------------
+ * eax edx ecx        | ebx edi esi ebp [*] | <none>             | eax, edx
  *
- * \author Bernie Innocenti <bernie@codewiz.org>
+ *  [*]  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.
  */
 
-
-
 #ifdef __APPLE__
-    //This workaround is necessary to compile under OS X assembler.
+    // This workaround is necessary to compile under OS X assembler.
     #define SWITCH_CONTEXT _asm_switch_context
-    #define SWITCH_VERSION _asm_switch_version
 #else
     #define SWITCH_CONTEXT asm_switch_context
-    #define SWITCH_VERSION asm_switch_version
 #endif
 
-/* void asm_switch_context(void ** new_sp, void ** save_sp) */
+/* void asm_switch_context(void ** new_sp [sp+4], void ** save_sp [sp+8]) */
 .globl SWITCH_CONTEXT
 SWITCH_CONTEXT:
-	pushl	%eax
-	pushl	%ebx
-	pushl	%ecx
-	pushl	%edx
-	pushl	%esi
-	pushl	%edi
 	pushl	%ebp
-	movl	0x24(%esp),%ebp         /* ebp = save_sp */
+	pushl	%ecx
+	movl	0x10(%esp),%ebp         /* ebp = save_sp */
 	movl	%esp,(%ebp)             /* *save_sp = esp */
-	movl	0x20(%esp),%ebp         /* ebp = new_sp */
+	movl	0x0c(%esp),%ebp         /* ebp = new_sp */
 	movl	(%ebp),%esp             /* esp = *new_sp */
-	popl	%ebp
-	popl	%edi
-	popl	%esi
-	popl	%edx
 	popl	%ecx
-	popl	%ebx
-	popl	%eax
-	ret
-
-/* int asm_switch_version(void) */
-.globl SWITCH_VERSION
-SWITCH_VERSION:
-	mov	$1,%eax
+	popl	%ebp
 	ret
-