Wrote syscall interrupt handler in assembly

src/x86/isr.c

@@ -65,7 +65,3 @@ void isr_timer(struct interrupt_frame_t *frame)
     printf("Timer tick.\n");
     apic_eoi();
 }
-
-void isr_syscall(struct interrupt_frame_t *frame)
-{
-}

src/x86/preempt.S

@@ -1,5 +1,28 @@
 .section .text
 
+.global isr_syscall
+.type isr_syscall, @function
+isr_syscall:
+    cli
+    push %edx
+    push %ecx
+    push %ebx
+    push %eax
+    push $kernel_state
+    mov $0x10, %ax
+    mov %ax, %ds
+    mov %ax, %es
+    mov %ax, %fs
+    mov %ax, %gs
+    call do_syscall
+    add $0x14, %esp
+    mov $0x23, %cx
+    mov %cx, %ds
+    mov %cx, %es
+    mov %cx, %fs
+    mov %cx, %gs
+    iret
+
 .global isr_preempt
 .type isr_preempt, @function
 isr_preempt:
@@ -7,11 +30,11 @@ isr_preempt:
     push %esp
     push $0x800
     call save_context
-    sub $8, %esp
+    add $8, %esp
     push $0x800
     push $kernel_state
     call next_process
-    sub $8, %esp
+    add $8, %esp
     push %eax
     call load_context