不论是 rt0_go 还是 go 语法 (如果在有 idle 的状况下) 最终都会调用 mstart
mstart
// mstart is the entry-point for new Ms.
//
// This must not split the stack because we may not even have stack
// bounds set up yet.
//
// May run during STW (because it doesn't have a P yet), so write
// barriers are not allowed.
//
//go:nosplit
//go:nowritebarrierrec
func mstart() {_g_ := getg()
osStack := _g_.stack.lo == 0
if osStack {
// Initialize stack bounds from system stack.
// Cgo may have left stack size in stack.hi.
// minit may update the stack bounds.
//
// Note: these bounds may not be very accurate.
// We set hi to &size, but there are things above
// it. The 1024 is supposed to compensate this,
// but is somewhat arbitrary.
size := _g_.stack.hi
if size == 0 {size = 8192 * sys.StackGuardMultiplier}
_g_.stack.hi = uintptr(noescape(unsafe.Pointer(&size)))
_g_.stack.lo = _g_.stack.hi - size + 1024
}
// Initialize stack guard so that we can start calling regular
// Go code.
_g_.stackguard0 = _g_.stack.lo + _StackGuard
// This is the g0, so we can also call go:systemstack
// functions, which check stackguard1.
_g_.stackguard1 = _g_.stackguard0
mstart1()
// Exit this thread.
if mStackIsSystemAllocated() {
// Windows, Solaris, illumos, Darwin, AIX and Plan 9 always system-allocate
// the stack, but put it in _g_.stack before mstart,
// so the logic above hasn't set osStack yet.
osStack = true
}
mexit(osStack)
}