X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Femul%2Fswitch_x86_64.s;h=ea76d2c98ed9d1246652f3aac29f1ad2152c0f19;hb=7911a6f01bc8a19f220f98e2fdc8595f65996853;hp=1632c816d4b01512c7fb554043aed9d7b8a259aa;hpb=2f1343e2774ac66a35c63ee90535265d67c78feb;p=bertos.git

diff --git a/bertos/emul/switch_x86_64.s b/bertos/emul/switch_x86_64.s
index 1632c816..ea76d2c9 100644
--- a/bertos/emul/switch_x86_64.s
+++ b/bertos/emul/switch_x86_64.s
@@ -30,29 +30,43 @@
  * Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
  * -->
  *
- * \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.
  */
 
 /* 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
+	popq	%rsi
+	popq	%rdi
+	popq	%rbp
 	ret