starting implicit function calls cleanup

1 files changed, 22 insertions, 0 deletions

diff --git a/asm/syscallasm.s b/asm/syscallasm.s
new file mode 100644
index 0000000..8860d89
--- /dev/null
+++ b/asm/syscallasm.s
@@ -0,0 +1,22 @@
+.global syscall
+
+// call from c with 4 x 32bit params
+// syscall number, p1,p2,p3,p4
+
+// TODO: push stack frame?
+
+syscall:
+
+	push %ebx // preserve (sysV abi convnetion)
+
+	mov 0x8(%esp),%eax    //syscall number
+	mov 0xC(%esp),%edx    //p1
+	mov 0x10(%esp),%ecx   //p2
+	mov 0x14(%esp),%ebx   //p3
+	
+	int $0x80
+	mov %ebx, %eax // set as return value
+
+	pop %ebx // preserve
+	ret
+