init: preserve registers in _syscall()

1 files changed, 12 insertions, 4 deletions

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