115 lines
3.3 KiB
Go
115 lines
3.3 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// This binary provides a convienient target for analyzing how the go-marshal
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// API causes its various arguments to escape to the heap. To use, build and
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// observe the output from the go compiler's escape analysis:
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//
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// $ bazel build :escape
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// ...
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// escape.go:67:2: moved to heap: task
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// escape.go:77:31: make([]byte, size) escapes to heap
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// escape.go:87:31: make([]byte, size) escapes to heap
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// escape.go:96:6: moved to heap: stat
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// ...
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//
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// This is not an automated test, but simply a minimal binary for easy analysis.
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package main
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import (
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"gvisor.dev/gvisor/pkg/usermem"
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"gvisor.dev/gvisor/tools/go_marshal/marshal"
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"gvisor.dev/gvisor/tools/go_marshal/test"
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)
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// dummyTask implements marshal.Task.
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type dummyTask struct {
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}
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func (*dummyTask) CopyScratchBuffer(size int) []byte {
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return make([]byte, size)
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}
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func (*dummyTask) CopyOutBytes(addr usermem.Addr, b []byte) (int, error) {
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return len(b), nil
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}
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func (*dummyTask) CopyInBytes(addr usermem.Addr, b []byte) (int, error) {
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return len(b), nil
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}
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func (task *dummyTask) MarshalBytes(addr usermem.Addr, marshallable marshal.Marshallable) {
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buf := task.CopyScratchBuffer(marshallable.SizeBytes())
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marshallable.MarshalBytes(buf)
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task.CopyOutBytes(addr, buf)
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}
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func (task *dummyTask) MarshalUnsafe(addr usermem.Addr, marshallable marshal.Marshallable) {
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buf := task.CopyScratchBuffer(marshallable.SizeBytes())
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marshallable.MarshalUnsafe(buf)
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task.CopyOutBytes(addr, buf)
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}
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// Expected escapes:
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// - task: passed to marshal.Marshallable.CopyOut as the marshal.Task interface.
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func doCopyOut() {
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task := dummyTask{}
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var stat test.Stat
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stat.CopyOut(&task, usermem.Addr(0xf000ba12))
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}
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// Expected escapes:
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// - buf: make allocates on the heap.
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func doMarshalBytesDirect() {
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task := dummyTask{}
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var stat test.Stat
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buf := task.CopyScratchBuffer(stat.SizeBytes())
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stat.MarshalBytes(buf)
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task.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
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}
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// Expected escapes:
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// - buf: make allocates on the heap.
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func doMarshalUnsafeDirect() {
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task := dummyTask{}
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var stat test.Stat
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buf := task.CopyScratchBuffer(stat.SizeBytes())
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stat.MarshalUnsafe(buf)
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task.CopyOutBytes(usermem.Addr(0xf000ba12), buf)
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}
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// Expected escapes:
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// - stat: passed to dummyTask.MarshalBytes as the marshal.Marshallable interface.
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func doMarshalBytesViaMarshallable() {
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task := dummyTask{}
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var stat test.Stat
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task.MarshalBytes(usermem.Addr(0xf000ba12), &stat)
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}
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// Expected escapes:
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// - stat: passed to dummyTask.MarshalUnsafe as the marshal.Marshallable interface.
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func doMarshalUnsafeViaMarshallable() {
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task := dummyTask{}
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var stat test.Stat
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task.MarshalUnsafe(usermem.Addr(0xf000ba12), &stat)
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}
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func main() {
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doCopyOut()
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doMarshalBytesDirect()
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doMarshalUnsafeDirect()
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doMarshalBytesViaMarshallable()
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doMarshalUnsafeViaMarshallable()
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}
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