From ef108730dc05fe3fc4d4cf5ff89a544b0d615fe6 Mon Sep 17 00:00:00 2001
From: Hubert Badocha <badocha.hubert@gmail.com>
Date: Wed, 29 Nov 2023 20:24:32 +0100
Subject: [PATCH] ia32/vfork: simplify assembly

JIRA: RTOS-697
---
 arch/ia32/syscalls.S | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/arch/ia32/syscalls.S b/arch/ia32/syscalls.S
index ef4a78d8..568a26b1 100644
--- a/arch/ia32/syscalls.S
+++ b/arch/ia32/syscalls.S
@@ -32,27 +32,17 @@ sym: \
 .size sym, .-sym
 
 
-.bss
-vfork_address:
-.space 4
-.text
 .globl vfork
 .type vfork, @function
 .align 4, 0x90
 vfork:
-	mov (%esp), %eax
-	mov %eax, (vfork_address)
+	/* Save the return address as child will override parent's stack.
+	 * Syscalls restore all registers but %eax thus %edx will not be overwritten.
+	 * %edx is used as it need not to be restored before function exit. */
+	mov (%esp), %edx
 	movl $4, %eax
 	int $0x80
-	cmp $0, %eax
-	jz vfork_child
-	push %eax
-	mov (vfork_address), %eax
-	mov %eax, 4(%esp)
-	pop %eax
-	ret
-vfork_child:
-	mov $0, %eax
+	mov %edx, (%esp)
 	ret
 .size vfork, .-vfork