// This function is called by a goroutine to execute a C function and
// switches from the goroutine stack to the system stack.
// Since we are unwinding the stack from callee to caller we have switch
// from the system stack to the goroutine stack.
off,_:=readIntRaw(it.mem,uintptr(it.regs.SP()+asmcgocallSPOffsetSaveSlot),int64(it.bi.Arch.PtrSize()))// reads "offset of SP from StackHi" from where runtime.asmcgocall saved it