runtime: remove openbsd/mips64 related code

The openbsd/mips64 port has been broken for many years and it has not
been possible to land the changes needed to unbreak it. As such, this
port is considered dead and can be decommissioned in order to remove
technical debt and allow other changes to be completed.

Updates #61546

Change-Id: I9680eab9fb3aa85b83de47c66e9ebaf8c388a3bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/649659
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Mark Freeman <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: 4a6f656c

src/runtime/crash_unix_test.go

@@ -65,7 +65,7 @@ func TestCrashDumpsAllThreads(t *testing.T) {
 		t.Skipf("skipping; not supported on %v", runtime.GOOS)
 	}
 
-	if runtime.GOOS == "openbsd" && (runtime.GOARCH == "arm" || runtime.GOARCH == "mips64" || runtime.GOARCH == "ppc64") {
+	if runtime.GOOS == "openbsd" && (runtime.GOARCH == "arm" || runtime.GOARCH == "ppc64") {
 		// This may be ncpu < 2 related...
 		t.Skipf("skipping; test fails on %s/%s - see issue #42464", runtime.GOOS, runtime.GOARCH)
 	}

src/runtime/defs_openbsd.go

@@ -11,7 +11,6 @@ GOARCH=amd64 go tool cgo -godefs defs_openbsd.go
 GOARCH=386 go tool cgo -godefs defs_openbsd.go
 GOARCH=arm go tool cgo -godefs defs_openbsd.go
 GOARCH=arm64 go tool cgo -godefs defs_openbsd.go
-GOARCH=mips64 go tool cgo -godefs defs_openbsd.go
 */
 
 package runtime

src/runtime/defs_openbsd_mips64.go

@@ -134,6 +134,54 @@ func semawakeup(mp *m) {
 	}
 }
 
+// mstart_stub provides glue code to call mstart from pthread_create.
+func mstart_stub()
+
+// May run with m.p==nil, so write barriers are not allowed.
+//
+//go:nowritebarrierrec
+func newosproc(mp *m) {
+	if false {
+		print("newosproc m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
+	}
+
+	// Initialize an attribute object.
+	var attr pthreadattr
+	if err := pthread_attr_init(&attr); err != 0 {
+		writeErrStr(failthreadcreate)
+		exit(1)
+	}
+
+	// Find out OS stack size for our own stack guard.
+	var stacksize uintptr
+	if pthread_attr_getstacksize(&attr, &stacksize) != 0 {
+		writeErrStr(failthreadcreate)
+		exit(1)
+	}
+	mp.g0.stack.hi = stacksize // for mstart
+
+	// Tell the pthread library we won't join with this thread.
+	if pthread_attr_setdetachstate(&attr, _PTHREAD_CREATE_DETACHED) != 0 {
+		writeErrStr(failthreadcreate)
+		exit(1)
+	}
+
+	// Finally, create the thread. It starts at mstart_stub, which does some low-level
+	// setup and then calls mstart.
+	var oset sigset
+	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
+	err := retryOnEAGAIN(func() int32 {
+		return pthread_create(&attr, abi.FuncPCABI0(mstart_stub), unsafe.Pointer(mp))
+	})
+	sigprocmask(_SIG_SETMASK, &oset, nil)
+	if err != 0 {
+		writeErrStr(failthreadcreate)
+		exit(1)
+	}
+
+	pthread_attr_destroy(&attr)
+}
+
 func osinit() {
 	numCPUStartup = getCPUCount()
 	physPageSize = getPageSize()
@@ -160,9 +208,6 @@ func goenvs() {
 // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
 func mpreinit(mp *m) {
 	gsignalSize := int32(32 * 1024)
-	if GOARCH == "mips64" {
-		gsignalSize = int32(64 * 1024)
-	}
 	mp.gsignal = malg(gsignalSize)
 	mp.gsignal.m = mp
 }