+[extern ci_offsetof_tThread_KernelStack]
+[extern SyscallHandler]
+[global SyscallStub]
+SyscallStub:
+ mov rbp, dr0
+ mov ebx, [rel ci_offsetof_tThread_KernelStack]
+ mov rbp, [rbp+rbx] ; Get kernel stack
+ xchg rbp, rsp ; Swap stacks
+
+ push rbp ; Save User RSP
+ push rcx ; RIP
+ push r11 ; RFLAGS
+
+ ; RDI
+ ; RSI
+ ; RDX
+ ; R10 (RCX for non syscall)
+ ; R8
+ ; R9
+ sub rsp, (6+2)*8
+ mov [rsp+0x00], rax ; Number
+; mov [rsp+0x08], rax ; Errno (output only)
+ mov [rsp+0x10], rdi ; Arg1
+ mov [rsp+0x18], rsi ; Arg2
+ mov [rsp+0x20], rdx ; Arg3
+ mov [rsp+0x28], r10 ; Arg4
+ mov [rsp+0x30], r8 ; Arg5
+ mov [rsp+0x38], r9 ; Arg6
+
+ mov rdi, rsp
+ sub rsp, 8
+ call SyscallHandler
+
+ %if 0
+[section .rodata]
+csSyscallReturn: db "Syscall Return: 0x%x",0
+[section .text]
+ mov rdi, csSyscallReturn
+ mov rsi, [rsp+0+8]
+ call Log
+ %endif
+
+ add rsp, 8
+ mov ebx, [rsp+8] ; Get errno
+ mov rax, [rsp+0] ; Get return
+ add rsp, (6+2)*8
+
+ pop r11
+ pop rcx
+ pop rsp ; Change back to user stack
+ ; TODO: Determine if user is 64 or 32 bit
+
+ db 0x48 ; REX, nasm doesn't have a sysretq opcode
+ sysret
+