Add internal nogo analysis & checkescape tool.

See tools/nogo/README.md.

The checkescape tool is able to perform recursive escape analysis, using the
actual generated binary to confirm the results produced by the compiler itself.

As an initial use case, this replaces the manual escape analysis tests used for
go_marshal, and validates that the CopyIn and CopyOut paths will not require
any allocation or stack splits.

Updates #2243

PiperOrigin-RevId: 307532986

7 files changed, 141 insertions, 141 deletions

diff --git a/tools/go_marshal/gomarshal/generator_interfaces_array_newtype.go b/tools/go_marshal/gomarshal/generator_interfaces_array_newtype.go
index 8d6f102d5..72ef03a22 100644
--- a/tools/go_marshal/gomarshal/generator_interfaces_array_newtype.go
+++ b/tools/go_marshal/gomarshal/generator_interfaces_array_newtype.go
@@ -44,6 +44,7 @@ func (g *interfaceGenerator) emitMarshallableForArrayNewtype(n *ast.Ident, a *as
 	lenExpr := g.arrayLenExpr(a)
 
 	g.emit("// SizeBytes implements marshal.Marshallable.SizeBytes.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) SizeBytes() int {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		if size, dynamic := g.scalarSize(elt); !dynamic {
@@ -77,6 +78,7 @@ func (g *interfaceGenerator) emitMarshallableForArrayNewtype(n *ast.Ident, a *as
 	g.emit("}\n\n")
 
 	g.emit("// Packed implements marshal.Marshallable.Packed.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) Packed() bool {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emit("// Array newtypes are always packed.\n")
@@ -99,17 +101,19 @@ func (g *interfaceGenerator) emitMarshallableForArrayNewtype(n *ast.Ident, a *as
 	g.emit("}\n\n")
 
 	g.emit("// CopyOutN implements marshal.Marshallable.CopyOutN.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-		g.emit("length, err := task.CopyOutBytes(addr, buf[:limit])\n")
+		g.emit("length, err := task.CopyOutBytes(addr, buf[:limit]) // escapes: okay.\n")
 		g.emitKeepAlive(g.r)
 		g.emit("return length, err\n")
 	})
 	g.emit("}\n\n")
 
 	g.emit("// CopyOut implements marshal.Marshallable.CopyOut.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emit("return %s.CopyOutN(task, addr, %s.SizeBytes())\n", g.r, g.r)
@@ -117,11 +121,12 @@ func (g *interfaceGenerator) emitMarshallableForArrayNewtype(n *ast.Ident, a *as
 	g.emit("}\n\n")
 
 	g.emit("// CopyIn implements marshal.Marshallable.CopyIn.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-		g.emit("length, err := task.CopyInBytes(addr, buf)\n")
+		g.emit("length, err := task.CopyInBytes(addr, buf) // escapes: okay.\n")
 		g.emitKeepAlive(g.r)
 		g.emit("return length, err\n")
 	})
diff --git a/tools/go_marshal/gomarshal/generator_interfaces_primitive_newtype.go b/tools/go_marshal/gomarshal/generator_interfaces_primitive_newtype.go
index ef9bb903d..39f654ea8 100644
--- a/tools/go_marshal/gomarshal/generator_interfaces_primitive_newtype.go
+++ b/tools/go_marshal/gomarshal/generator_interfaces_primitive_newtype.go
@@ -104,6 +104,7 @@ func (g *interfaceGenerator) emitMarshallableForPrimitiveNewtype(nt *ast.Ident)
 	g.recordUsedImport("usermem")
 
 	g.emit("// SizeBytes implements marshal.Marshallable.SizeBytes.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) SizeBytes() int {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		if size, dynamic := g.scalarSize(nt); !dynamic {
@@ -129,6 +130,7 @@ func (g *interfaceGenerator) emitMarshallableForPrimitiveNewtype(nt *ast.Ident)
 	g.emit("}\n\n")
 
 	g.emit("// Packed implements marshal.Marshallable.Packed.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) Packed() bool {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emit("// Scalar newtypes are always packed.\n")
@@ -151,17 +153,19 @@ func (g *interfaceGenerator) emitMarshallableForPrimitiveNewtype(nt *ast.Ident)
 	g.emit("}\n\n")
 
 	g.emit("// CopyOutN implements marshal.Marshallable.CopyOutN.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-		g.emit("length, err := task.CopyOutBytes(addr, buf[:limit])\n")
+		g.emit("length, err := task.CopyOutBytes(addr, buf[:limit]) // escapes: okay.\n")
 		g.emitKeepAlive(g.r)
 		g.emit("return length, err\n")
 	})
 	g.emit("}\n\n")
 
 	g.emit("// CopyOut implements marshal.Marshallable.CopyOut.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emit("return %s.CopyOutN(task, addr, %s.SizeBytes())\n", g.r, g.r)
@@ -169,11 +173,12 @@ func (g *interfaceGenerator) emitMarshallableForPrimitiveNewtype(nt *ast.Ident)
 	g.emit("}\n\n")
 
 	g.emit("// CopyIn implements marshal.Marshallable.CopyIn.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-		g.emit("length, err := task.CopyInBytes(addr, buf)\n")
+		g.emit("length, err := task.CopyInBytes(addr, buf) // escapes: okay.\n")
 		g.emitKeepAlive(g.r)
 		g.emit("return length, err\n")
 	})
@@ -205,6 +210,7 @@ func (g *interfaceGenerator) emitMarshallableSliceForPrimitiveNewtype(nt *ast.Id
 	}
 
 	g.emit("// Copy%sIn copies in a slice of %s objects from the task's memory.\n", slice.ident, eltType)
+	g.emit("//go:nosplit\n")
 	g.emit("func Copy%sIn(task marshal.Task, addr usermem.Addr, dst []%s) (int, error) {\n", slice.ident, eltType)
 	g.inIndent(func() {
 		g.emit("count := len(dst)\n")
@@ -217,13 +223,14 @@ func (g *interfaceGenerator) emitMarshallableSliceForPrimitiveNewtype(nt *ast.Id
 
 		g.emitCastSliceToByteSlice("&dst", "buf", "size * count")
 
-		g.emit("length, err := task.CopyInBytes(addr, buf)\n")
+		g.emit("length, err := task.CopyInBytes(addr, buf) // escapes: okay.\n")
 		g.emitKeepAlive("dst")
 		g.emit("return length, err\n")
 	})
 	g.emit("}\n\n")
 
 	g.emit("// Copy%sOut copies a slice of %s objects to the task's memory.\n", slice.ident, eltType)
+	g.emit("//go:nosplit\n")
 	g.emit("func Copy%sOut(task marshal.Task, addr usermem.Addr, src []%s) (int, error) {\n", slice.ident, eltType)
 	g.inIndent(func() {
 		g.emit("count := len(src)\n")
@@ -236,7 +243,7 @@ func (g *interfaceGenerator) emitMarshallableSliceForPrimitiveNewtype(nt *ast.Id
 
 		g.emitCastSliceToByteSlice("&src", "buf", "size * count")
 
-		g.emit("length, err := task.CopyOutBytes(addr, buf)\n")
+		g.emit("length, err := task.CopyOutBytes(addr, buf) // escapes: okay.\n")
 		g.emitKeepAlive("src")
 		g.emit("return length, err\n")
 	})
diff --git a/tools/go_marshal/gomarshal/generator_interfaces_struct.go b/tools/go_marshal/gomarshal/generator_interfaces_struct.go
index 4236e978e..9cd3c9579 100644
--- a/tools/go_marshal/gomarshal/generator_interfaces_struct.go
+++ b/tools/go_marshal/gomarshal/generator_interfaces_struct.go
@@ -249,6 +249,7 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 	g.emit("}\n\n")
 
 	g.emit("// Packed implements marshal.Marshallable.Packed.\n")
+	g.emit("//go:nosplit\n")
 	g.emit("func (%s *%s) Packed() bool {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		expr, fieldsMaybePacked := g.areFieldsPackedExpression()
@@ -317,15 +318,16 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 	g.emit("}\n\n")
 
 	g.emit("// CopyOutN implements marshal.Marshallable.CopyOutN.\n")
+	g.emit("//go:nosplit\n")
 	g.recordUsedImport("marshal")
 	g.recordUsedImport("usermem")
 	g.emit("func (%s *%s) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		fallback := func() {
 			g.emit("// Type %s doesn't have a packed layout in memory, fall back to MarshalBytes.\n", g.typeName())
-			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes())\n", g.r)
-			g.emit("%s.MarshalBytes(buf)\n", g.r)
-			g.emit("return task.CopyOutBytes(addr, buf[:limit])\n")
+			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes()) // escapes: okay.\n", g.r)
+			g.emit("%s.MarshalBytes(buf) // escapes: fallback.\n", g.r)
+			g.emit("return task.CopyOutBytes(addr, buf[:limit]) // escapes: okay.\n")
 		}
 		if thisPacked {
 			g.recordUsedImport("reflect")
@@ -339,7 +341,7 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 			// Fast serialization.
 			g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-			g.emit("length, err := task.CopyOutBytes(addr, buf[:limit])\n")
+			g.emit("length, err := task.CopyOutBytes(addr, buf[:limit]) // escapes: okay.\n")
 			g.emitKeepAlive(g.r)
 			g.emit("return length, err\n")
 		} else {
@@ -349,6 +351,7 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 	g.emit("}\n\n")
 
 	g.emit("// CopyOut implements marshal.Marshallable.CopyOut.\n")
+	g.emit("//go:nosplit\n")
 	g.recordUsedImport("marshal")
 	g.recordUsedImport("usermem")
 	g.emit("func (%s *%s) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
@@ -358,17 +361,18 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 	g.emit("}\n\n")
 
 	g.emit("// CopyIn implements marshal.Marshallable.CopyIn.\n")
+	g.emit("//go:nosplit\n")
 	g.recordUsedImport("marshal")
 	g.recordUsedImport("usermem")
 	g.emit("func (%s *%s) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		fallback := func() {
 			g.emit("// Type %s doesn't have a packed layout in memory, fall back to UnmarshalBytes.\n", g.typeName())
-			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes())\n", g.r)
-			g.emit("length, err := task.CopyInBytes(addr, buf)\n")
+			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes()) // escapes: okay.\n", g.r)
+			g.emit("length, err := task.CopyInBytes(addr, buf) // escapes: okay.\n")
 			g.emit("// Unmarshal unconditionally. If we had a short copy-in, this results in a\n")
 			g.emit("// partially unmarshalled struct.\n")
-			g.emit("%s.UnmarshalBytes(buf)\n", g.r)
+			g.emit("%s.UnmarshalBytes(buf) // escapes: fallback.\n", g.r)
 			g.emit("return length, err\n")
 		}
 		if thisPacked {
@@ -383,7 +387,7 @@ func (g *interfaceGenerator) emitMarshallableForStruct(st *ast.StructType) {
 			// Fast deserialization.
 			g.emitCastToByteSlice(g.r, "buf", fmt.Sprintf("%s.SizeBytes()", g.r))
 
-			g.emit("length, err := task.CopyInBytes(addr, buf)\n")
+			g.emit("length, err := task.CopyInBytes(addr, buf) // escapes: okay.\n")
 			g.emitKeepAlive(g.r)
 			g.emit("return length, err\n")
 		} else {
diff --git a/tools/go_marshal/test/BUILD b/tools/go_marshal/test/BUILD
index 3b839799d..2fbcc8a03 100644
--- a/tools/go_marshal/test/BUILD
+++ b/tools/go_marshal/test/BUILD
@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_binary", "go_library", "go_test")
+load("//tools:defs.bzl", "go_library", "go_test")
 
 licenses(["notice"])
 
@@ -25,21 +25,10 @@ go_library(
     testonly = 1,
     srcs = ["test.go"],
     marshal = True,
+    visibility = ["//tools/go_marshal/test:__subpackages__"],
     deps = ["//tools/go_marshal/test/external"],
 )
 
-go_binary(
-    name = "escape",
-    testonly = 1,
-    srcs = ["escape.go"],
-    gc_goopts = ["-m"],
-    deps = [
-        ":test",
-        "//pkg/usermem",
-        "//tools/go_marshal/marshal",
-    ],
-)
-
 go_test(
     name = "marshal_test",
     size = "small",
diff --git a/tools/go_marshal/test/escape.go b/tools/go_marshal/test/escape.go
deleted file mode 100644
index 184f05ea3..000000000
--- a/tools/go_marshal/test/escape.go
+++ /dev/null
@@ -1,114 +0,0 @@
-// 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.
-
-// This binary provides a convienient target for analyzing how the go-marshal
-// API causes its various arguments to escape to the heap. To use, build and
-// observe the output from the go compiler's escape analysis:
-//
-// $ bazel build :escape
-// ...
-// escape.go:67:2: moved to heap: task
-// escape.go:77:31: make([]byte, size) escapes to heap
-// escape.go:87:31: make([]byte, size) escapes to heap
-// escape.go:96:6: moved to heap: stat
-// ...
-//
-// This is not an automated test, but simply a minimal binary for easy analysis.
-package main
-
-import (
-	"gvisor.dev/gvisor/pkg/usermem"
-	"gvisor.dev/gvisor/tools/go_marshal/marshal"
-	"gvisor.dev/gvisor/tools/go_marshal/test"
-)
-
-// dummyTask implements marshal.Task.
-type dummyTask struct {
-}
-
-func (*dummyTask) CopyScratchBuffer(size int) []byte {
-	return make([]byte, size)
-}
-
-func (*dummyTask) CopyOutBytes(addr usermem.Addr, b []byte) (int, error) {
-	return len(b), nil
-}
-
-func (*dummyTask) CopyInBytes(addr usermem.Addr, b []byte) (int, error) {
-	return len(b), nil
-}
-
-func (task *dummyTask) MarshalBytes(addr usermem.Addr, marshallable marshal.Marshallable) {
-	buf := task.CopyScratchBuffer(marshallable.SizeBytes())
-	marshallable.MarshalBytes(buf)
-	task.CopyOutBytes(addr, buf)
-}
-
-func (task *dummyTask) MarshalUnsafe(addr usermem.Addr, marshallable marshal.Marshallable) {
-	buf := task.CopyScratchBuffer(marshallable.SizeBytes())
-	marshallable.MarshalUnsafe(buf)
-	task.CopyOutBytes(addr, buf)
-}
-
-// Expected escapes:
-// - task: passed to marshal.Marshallable.CopyOut as the marshal.Task interface.
-func doCopyOut() {
-	task := dummyTask{}
-	var stat test.Stat
-	stat.CopyOut(&task, usermem.Addr(0xf000ba12))
-}
-
-// Expected escapes:
-// - buf: make allocates on the heap.
-func doMarshalBytesDirect() {
-	task := dummyTask{}
-	var stat test.Stat
-	buf := task.CopyScratchBuffer(stat.SizeBytes())
-	stat.MarshalBytes(buf)
-	task.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
-}
-
-// Expected escapes:
-// - buf: make allocates on the heap.
-func doMarshalUnsafeDirect() {
-	task := dummyTask{}
-	var stat test.Stat
-	buf := task.CopyScratchBuffer(stat.SizeBytes())
-	stat.MarshalUnsafe(buf)
-	task.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
-}
-
-// Expected escapes:
-// - stat: passed to dummyTask.MarshalBytes as the marshal.Marshallable interface.
-func doMarshalBytesViaMarshallable() {
-	task := dummyTask{}
-	var stat test.Stat
-	task.MarshalBytes(usermem.Addr(0xf000ba12), &stat)
-}
-
-// Expected escapes:
-// - stat: passed to dummyTask.MarshalUnsafe as the marshal.Marshallable interface.
-func doMarshalUnsafeViaMarshallable() {
-	task := dummyTask{}
-	var stat test.Stat
-	task.MarshalUnsafe(usermem.Addr(0xf000ba12), &stat)
-}
-
-func main() {
-	doCopyOut()
-	doMarshalBytesDirect()
-	doMarshalUnsafeDirect()
-	doMarshalBytesViaMarshallable()
-	doMarshalUnsafeViaMarshallable()
-}
diff --git a/tools/go_marshal/test/escape/BUILD b/tools/go_marshal/test/escape/BUILD
new file mode 100644
index 000000000..f74e6ffae
--- /dev/null
+++ b/tools/go_marshal/test/escape/BUILD
@@ -0,0 +1,14 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "escape",
+    testonly = 1,
+    srcs = ["escape.go"],
+    deps = [
+        "//pkg/usermem",
+        "//tools/go_marshal/marshal",
+        "//tools/go_marshal/test",
+    ],
+)
diff --git a/tools/go_marshal/test/escape/escape.go b/tools/go_marshal/test/escape/escape.go
new file mode 100644
index 000000000..6a46ddbf8
--- /dev/null
+++ b/tools/go_marshal/test/escape/escape.go
@@ -0,0 +1,95 @@
+// 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 escape
+
+import (
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/tools/go_marshal/marshal"
+	"gvisor.dev/gvisor/tools/go_marshal/test"
+)
+
+// dummyTask implements marshal.Task.
+type dummyTask struct {
+}
+
+func (*dummyTask) CopyScratchBuffer(size int) []byte {
+	return make([]byte, size)
+}
+
+func (*dummyTask) CopyOutBytes(addr usermem.Addr, b []byte) (int, error) {
+	return len(b), nil
+}
+
+func (*dummyTask) CopyInBytes(addr usermem.Addr, b []byte) (int, error) {
+	return len(b), nil
+}
+
+func (t *dummyTask) MarshalBytes(addr usermem.Addr, marshallable marshal.Marshallable) {
+	buf := t.CopyScratchBuffer(marshallable.SizeBytes())
+	marshallable.MarshalBytes(buf)
+	t.CopyOutBytes(addr, buf)
+}
+
+func (t *dummyTask) MarshalUnsafe(addr usermem.Addr, marshallable marshal.Marshallable) {
+	buf := t.CopyScratchBuffer(marshallable.SizeBytes())
+	marshallable.MarshalUnsafe(buf)
+	t.CopyOutBytes(addr, buf)
+}
+
+// +checkescape:all
+//go:nosplit
+func doCopyIn(t *dummyTask) {
+	var stat test.Stat
+	stat.CopyIn(t, usermem.Addr(0xf000ba12))
+}
+
+// +checkescape:all
+//go:nosplit
+func doCopyOut(t *dummyTask) {
+	var stat test.Stat
+	stat.CopyOut(t, usermem.Addr(0xf000ba12))
+}
+
+// +mustescape:builtin
+// +mustescape:stack
+func doMarshalBytesDirect(t *dummyTask) {
+	var stat test.Stat
+	buf := t.CopyScratchBuffer(stat.SizeBytes())
+	stat.MarshalBytes(buf)
+	t.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
+}
+
+// +mustescape:builtin
+// +mustescape:stack
+func doMarshalUnsafeDirect(t *dummyTask) {
+	var stat test.Stat
+	buf := t.CopyScratchBuffer(stat.SizeBytes())
+	stat.MarshalUnsafe(buf)
+	t.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
+}
+
+// +mustescape:local,heap
+// +mustescape:stack
+func doMarshalBytesViaMarshallable(t *dummyTask) {
+	var stat test.Stat
+	t.MarshalBytes(usermem.Addr(0xf000ba12), &stat)
+}
+
+// +mustescape:local,heap
+// +mustescape:stack
+func doMarshalUnsafeViaMarshallable(t *dummyTask) {
+	var stat test.Stat
+	t.MarshalUnsafe(usermem.Addr(0xf000ba12), &stat)
+}