From: arighi <arighi@38d2e660-2303-0410-9eaa-f027e97ec537>
Date: Wed, 17 Mar 2010 11:53:05 +0000 (+0000)
Subject: fix asm_switch_context() for the x86 and x86_64 archs
X-Git-Tag: 2.4.0~48
X-Git-Url: https://codewiz.org/gitweb?a=commitdiff_plain;ds=sidebyside;h=fc34a91daf3bab5fac57c928bb4bb948e002e0fb;p=bertos.git

fix asm_switch_context() for the x86 and x86_64 archs

Save and restore all the callee-clobbered registers minus the return
registers, according to the x86 and x86_64 ABI.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@3216 38d2e660-2303-0410-9eaa-f027e97ec537
---

diff --git a/bertos/cpu/frame.h b/bertos/cpu/frame.h
index dbb20a1e..90995a8a 100644
--- a/bertos/cpu/frame.h
+++ b/bertos/cpu/frame.h
@@ -53,7 +53,7 @@
 #if CPU_X86
 	#if CPU_X86_32
 
-		#define CPU_SAVED_REGS_CNT      4
+		#define CPU_SAVED_REGS_CNT      2
 		#define CPU_STACK_GROWS_UPWARD  0
 		#define CPU_SP_ON_EMPTY_SLOT	0
 
diff --git a/bertos/emul/switch_i386.S b/bertos/emul/switch_i386.S
index b605c15e..abcb487b 100644
--- a/bertos/emul/switch_i386.S
+++ b/bertos/emul/switch_i386.S
@@ -34,6 +34,19 @@
  * \author Bernie Innocenti <bernie@codewiz.org>
  *
  * \brief i386 context switch
+ *
+ * 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
+ *
+ *  [*]  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__
@@ -47,15 +60,11 @@
 .globl SWITCH_CONTEXT
 SWITCH_CONTEXT:
 	pushl	%ebp
-	pushl	%edi
-	pushl	%esi
-	pushl	%ebx
-	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	%ebx
-	popl	%esi
-	popl	%edi
+	popl	%ecx
 	popl	%ebp
 	ret
diff --git a/bertos/emul/switch_x86_64.s b/bertos/emul/switch_x86_64.s
index de0f8f65..df12bed1 100644
--- a/bertos/emul/switch_x86_64.s
+++ b/bertos/emul/switch_x86_64.s
@@ -33,7 +33,20 @@
  * \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]) */
@@ -42,7 +55,7 @@ asm_switch_context:
 	pushq	%rbp
 	pushq	%rdi
 	pushq	%rsi
-	pushq	%rbx
+	pushq	%rcx
 	pushq	%r8
 	pushq	%r9
 	pushq	%r10
@@ -53,7 +66,7 @@ asm_switch_context:
 	popq	%r10
 	popq	%r9
 	popq	%r8
-	popq	%rbx
+	popq	%rcx
 	popq	%rsi
 	popq	%rdi
 	popq	%rbp