goid: new package

Allows retrieving the goroutine ID for concurrency testing when the race
detector is enabled.

Updates #1472

PiperOrigin-RevId: 289155308

7 files changed, 256 insertions, 0 deletions

diff --git a/pkg/goid/BUILD b/pkg/goid/BUILD
new file mode 100644
index 000000000..5d31e5366
--- /dev/null
+++ b/pkg/goid/BUILD
@@ -0,0 +1,26 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "goid",
+    srcs = [
+        "goid.go",
+        "goid_amd64.s",
+        "goid_race.go",
+        "goid_unsafe.go",
+    ],
+    importpath = "gvisor.dev/gvisor/pkg/goid",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "goid_test",
+    size = "small",
+    srcs = [
+        "empty_test.go",
+        "goid_test.go",
+    ],
+    embed = [":goid"],
+)
diff --git a/pkg/goid/empty_test.go b/pkg/goid/empty_test.go
new file mode 100644
index 000000000..c0a4b17ab
--- /dev/null
+++ b/pkg/goid/empty_test.go
@@ -0,0 +1,22 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !race
+
+package goid
+
+import "testing"
+
+// TestNothing exists to make the build system happy.
+func TestNothing(t *testing.T) {}
diff --git a/pkg/goid/goid.go b/pkg/goid/goid.go
new file mode 100644
index 000000000..39df30031
--- /dev/null
+++ b/pkg/goid/goid.go
@@ -0,0 +1,24 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !race
+
+// Package goid provides access to the ID of the current goroutine in
+// race/gotsan builds.
+package goid
+
+// Get returns the ID of the current goroutine.
+func Get() int64 {
+	panic("unimplemented for non-race builds")
+}
diff --git a/pkg/goid/goid_amd64.s b/pkg/goid/goid_amd64.s
new file mode 100644
index 000000000..d9f5cd2a3
--- /dev/null
+++ b/pkg/goid/goid_amd64.s
@@ -0,0 +1,21 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "textflag.h"
+
+// func getg() *g
+TEXT ·getg(SB),NOSPLIT,$0-8
+	MOVQ (TLS), R14
+	MOVQ R14, ret+0(FP)
+	RET
diff --git a/pkg/goid/goid_race.go b/pkg/goid/goid_race.go
new file mode 100644
index 000000000..1766beaee
--- /dev/null
+++ b/pkg/goid/goid_race.go
@@ -0,0 +1,25 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Only available in race/gotsan builds.
+// +build race
+
+// Package goid provides access to the ID of the current goroutine in
+// race/gotsan builds.
+package goid
+
+// Get returns the ID of the current goroutine.
+func Get() int64 {
+	return goid()
+}
diff --git a/pkg/goid/goid_test.go b/pkg/goid/goid_test.go
new file mode 100644
index 000000000..31970ce79
--- /dev/null
+++ b/pkg/goid/goid_test.go
@@ -0,0 +1,74 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build race
+
+package goid
+
+import (
+	"runtime"
+	"sync"
+	"testing"
+)
+
+func TestInitialGoID(t *testing.T) {
+	const max = 10000
+	if id := goid(); id < 0 || id > max {
+		t.Errorf("got goid = %d, want 0 < goid <= %d", id, max)
+	}
+}
+
+// TestGoIDSquence verifies that goid returns values which could plausibly be
+// goroutine IDs. If this test breaks or becomes flaky, the structs in
+// goid_unsafe.go may need to be updated.
+func TestGoIDSquence(t *testing.T) {
+	// Goroutine IDs are cached by each P.
+	runtime.GOMAXPROCS(1)
+
+	// Fill any holes in lower range.
+	for i := 0; i < 50; i++ {
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			wg.Done()
+
+			// Leak the goroutine to prevent the ID from being
+			// reused.
+			select {}
+		}()
+		wg.Wait()
+	}
+
+	id := goid()
+	for i := 0; i < 100; i++ {
+		var (
+			newID int64
+			wg    sync.WaitGroup
+		)
+		wg.Add(1)
+		go func() {
+			newID = goid()
+			wg.Done()
+
+			// Leak the goroutine to prevent the ID from being
+			// reused.
+			select {}
+		}()
+		wg.Wait()
+		if max := id + 100; newID <= id || newID > max {
+			t.Errorf("unexpected goroutine ID pattern, got goid = %d, want %d < goid <= %d (previous = %d)", newID, id, max, id)
+		}
+		id = newID
+	}
+}
diff --git a/pkg/goid/goid_unsafe.go b/pkg/goid/goid_unsafe.go
new file mode 100644
index 000000000..ded8004dd
--- /dev/null
+++ b/pkg/goid/goid_unsafe.go
@@ -0,0 +1,64 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package goid
+
+// Structs from Go runtime. These may change in the future and require
+// updating. These structs are currently the same on both AMD64 and ARM64,
+// but may diverge in the future.
+
+type stack struct {
+	lo uintptr
+	hi uintptr
+}
+
+type gobuf struct {
+	sp   uintptr
+	pc   uintptr
+	g    uintptr
+	ctxt uintptr
+	ret  uint64
+	lr   uintptr
+	bp   uintptr
+}
+
+type g struct {
+	stack       stack
+	stackguard0 uintptr
+	stackguard1 uintptr
+
+	_panic       uintptr
+	_defer       uintptr
+	m            uintptr
+	sched        gobuf
+	syscallsp    uintptr
+	syscallpc    uintptr
+	stktopsp     uintptr
+	param        uintptr
+	atomicstatus uint32
+	stackLock    uint32
+	goid         int64
+
+	// More fields...
+	//
+	// We only use goid and the fields before it are only listed to
+	// calculate the correct offset.
+}
+
+func getg() *g
+
+// goid returns the ID of the current goroutine.
+func goid() int64 {
+	return getg().goid
+}