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https://github.com/golang/go
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7e987b7b33
We are copying the results to uninitialized stack space. Write barrier is not needed. Fixes #30041. Change-Id: Ia91d74dbafd96dc2bd92de0cb479808991dda03e Reviewed-on: https://go-review.googlesource.com/c/160737 Run-TryBot: Cherry Zhang <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org>
64 lines
1.1 KiB
Go
64 lines
1.1 KiB
Go
// run
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// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Issue 30041: copying results of a reflect-generated
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// call on stack should not have write barrier.
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package main
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import (
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"reflect"
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"runtime"
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"unsafe"
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)
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var badPtr uintptr
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var sink []byte
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func init() {
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// Allocate large enough to use largeAlloc.
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b := make([]byte, 1<<16-1)
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sink = b // force heap allocation
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// Any space between the object and the end of page is invalid to point to.
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badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1
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}
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type ft func() *int
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var fn ft
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func rf([]reflect.Value) []reflect.Value {
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a := reflect.ValueOf((*int)(nil))
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return []reflect.Value{a}
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}
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const N = 1000
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func main() {
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fn = reflect.MakeFunc(reflect.TypeOf(fn), rf).Interface().(ft)
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// Keep running GC so the write barrier is on.
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go func() {
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for i := 0; i < N; i++ {
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runtime.GC()
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}
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}()
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var x [10]uintptr
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for i := range x {
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x[i] = badPtr
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}
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for i := 0; i < N; i++ {
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runtime.Gosched()
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use(x) // prepare bad pointers on stack
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fn()
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}
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}
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//go:noinline
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func use([10]uintptr) {}
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