the syscall stack frame and Context::regs method

hi, i am reading the code about system call. after the sys_ipc_wrapper (in file kern/syscalls.cpp) is called.it get the thread's pointer by current_thread and then get the Syscall_frame. the code is like this: ... Thread *curr=current_thread(); Syscall_frame *f = curr->regs(); ... i can not understand the relationship between curr->regs() and the system call's stack frame.