From 38d1799046ca8148fc2aba871081fabda6082d2e Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Thu, 12 Aug 2021 19:17:29 +0200
Subject: init: preserve registers in _syscall()

---
 src/init/syscall.s | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

(limited to 'src/init/syscall.s')

diff --git a/src/init/syscall.s b/src/init/syscall.s
index 86d3523..78ce817 100644
--- a/src/init/syscall.s
+++ b/src/init/syscall.s
@@ -2,12 +2,20 @@
 .global _syscall
 .type _syscall, @function
 _syscall:
-	mov 4(%esp), %eax
-	mov 8(%esp), %ebx
+	push %ebx // preserve registers
+	push %esi
+	push %edi
+
+//  note: i could squeeze out another parameter out of %ebp
+	mov 16(%esp), %eax
+	mov 20(%esp), %ebx
 	mov %esp, %ecx
 	mov $_syscall_ret, %edx
-	mov 12(%esp), %esi
-	mov 16(%esp), %edi
+	mov 24(%esp), %esi
+	mov 28(%esp), %edi
 	sysenter
 _syscall_ret:
+	pop %edi
+	pop %esi
+	pop %ebx
 	ret
-- 
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