Question about systemcall

Hi, all

i am a newbie to L4.
i have a question about systemcall.

i want to trace a syscall's route for example ThreadControl.
from the top 
convenience programming interface:DeassociateInterrupt() 
calls 
system-call funtion:ThreadControl() 

In ThreadControl(). i saw the source code call __L4_ThreadCOntrol() funtion.
but i don't know how and where __L4_ThreadControl() is implement.? 

and i read some sourcecode find that:
the route is:
SYSCALL_STUB(thread_control) -->then "int SYS_SYSCALL_NUM" to enter system interrupt
-->then jmp to IA32_EXC_NO_ERRORCODE(exc_user_syscall, 0).
--> then call the sys_thread_control() implement funtion.

am i correct?

and how jmp from __L4_ThreadControl() to SYSCALL_STUB(thread_control)?
Thank you very much!