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cmd/compile: add missing WBs for reflect.{Slice,String}Header.Data
Fixes #19168. Change-Id: I3f4fcc0b189c53819ac29ef8de86fdad76a17488 Reviewed-on: https://go-review.googlesource.com/37663 Reviewed-by: Keith Randall <khr@golang.org>
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@ -3454,6 +3454,11 @@ func (s *state) insertWBstore(t *Type, left, right *ssa.Value, skip skipMask) {
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if !s.WBPos.IsKnown() {
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s.WBPos = left.Pos
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}
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if t == Types[TUINTPTR] {
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// Stores to reflect.{Slice,String}Header.Data.
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s.vars[&memVar] = s.newValue3I(ssa.OpStoreWB, ssa.TypeMem, s.config.PtrSize, left, right, s.mem())
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return
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}
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s.storeTypeScalars(t, left, right, skip)
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s.storeTypePtrsWB(t, left, right)
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}
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@ -2006,6 +2006,29 @@ func isstack(n *Node) bool {
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return false
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}
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// isReflectHeaderDataField reports whether l is an expression p.Data
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// where p has type reflect.SliceHeader or reflect.StringHeader.
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func isReflectHeaderDataField(l *Node) bool {
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if l.Type != Types[TUINTPTR] {
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return false
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}
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var tsym *Sym
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switch l.Op {
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case ODOT:
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tsym = l.Left.Type.Sym
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case ODOTPTR:
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tsym = l.Left.Type.Elem().Sym
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default:
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return false
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}
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if tsym == nil || l.Sym.Name != "Data" || tsym.Pkg.Path != "reflect" {
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return false
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}
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return tsym.Name == "SliceHeader" || tsym.Name == "StringHeader"
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}
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// Do we need a write barrier for assigning to l?
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func needwritebarrier(l *Node) bool {
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if !use_writebarrier {
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@ -2016,15 +2039,21 @@ func needwritebarrier(l *Node) bool {
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return false
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}
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// No write barrier for write of non-pointers.
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dowidth(l.Type)
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if !haspointers(l.Type) {
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// No write barrier for write to stack.
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if isstack(l) {
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return false
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}
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// No write barrier for write to stack.
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if isstack(l) {
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// Package unsafe's documentation says storing pointers into
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// reflect.SliceHeader and reflect.StringHeader's Data fields
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// is valid, even though they have type uintptr (#19168).
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if isReflectHeaderDataField(l) {
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return true
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}
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// No write barrier for write of non-pointers.
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dowidth(l.Type)
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if !haspointers(l.Type) {
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return false
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}
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58
test/fixedbugs/issue19168.go
Normal file
58
test/fixedbugs/issue19168.go
Normal file
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@ -0,0 +1,58 @@
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// errorcheck -0 -l -d=wb
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// Copyright 2017 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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package p
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import (
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"reflect"
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"unsafe"
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reflect2 "reflect"
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)
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func sink(e interface{})
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func a(hdr *reflect.SliceHeader, p *byte) {
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hdr.Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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}
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func b(hdr *reflect.StringHeader, p *byte) {
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hdr.Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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}
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func c(hdrs *[1]reflect.SliceHeader, p *byte) {
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hdrs[0].Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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}
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func d(hdr *struct{ s reflect.StringHeader }, p *byte) {
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hdr.s.Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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}
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func e(p *byte) (resHeap, resStack string) {
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sink(&resHeap)
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hdr := (*reflect.StringHeader)(unsafe.Pointer(&resHeap))
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hdr.Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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// No write barrier for non-escaping stack vars.
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hdr = (*reflect.StringHeader)(unsafe.Pointer(&resStack))
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hdr.Data = uintptr(unsafe.Pointer(p))
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return
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}
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func f(hdr *reflect2.SliceHeader, p *byte) {
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hdr.Data = uintptr(unsafe.Pointer(p)) // ERROR "write barrier"
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}
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type SliceHeader struct {
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Data uintptr
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}
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func g(hdr *SliceHeader, p *byte) {
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// No write barrier for lookalike SliceHeader.
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hdr.Data = uintptr(unsafe.Pointer(p))
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}
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