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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime_test
import (
"go/ast"
"go/build"
"go/importer"
"go/parser"
"go/printer"
"go/token"
"go/types"
"internal/testenv"
"os"
"regexp"
"runtime"
"strings"
"testing"
)
// Check that 64-bit fields on which we apply atomic operations
// are aligned to 8 bytes. This can be a problem on 32-bit systems.
func TestAtomicAlignment(t *testing.T) {
testenv.MustHaveGoBuild(t) // go command needed to resolve std .a files for importer.Default().
// Read the code making the tables above, to see which fields and
// variables we are currently checking.
checked := map[string]bool{}
x, err := os.ReadFile("./align_runtime_test.go")
if err != nil {
t.Fatalf("read failed: %v", err)
}
fieldDesc := map[int]string{}
r := regexp.MustCompile(`unsafe[.]Offsetof[(](\w+){}[.](\w+)[)]`)
matches := r.FindAllStringSubmatch(string(x), -1)
for i, v := range matches {
checked["field runtime."+v[1]+"."+v[2]] = true
fieldDesc[i] = v[1] + "." + v[2]
}
varDesc := map[int]string{}
r = regexp.MustCompile(`unsafe[.]Pointer[(]&(\w+)[)]`)
matches = r.FindAllStringSubmatch(string(x), -1)
for i, v := range matches {
checked["var "+v[1]] = true
varDesc[i] = v[1]
}
// Check all of our alignments. This is the actual core of the test.
for i, d := range runtime.AtomicFields {
if d%8 != 0 {
t.Errorf("field alignment of %s failed: offset is %d", fieldDesc[i], d)
}
}
for i, p := range runtime.AtomicVariables {
if uintptr(p)%8 != 0 {
t.Errorf("variable alignment of %s failed: address is %x", varDesc[i], p)
}
}
// The code above is the actual test. The code below attempts to check
// that the tables used by the code above are exhaustive.
// Parse the whole runtime package, checking that arguments of
// appropriate atomic operations are in the list above.
fset := token.NewFileSet()
m, err := parser.ParseDir(fset, ".", nil, 0)
if err != nil {
t.Fatalf("parsing runtime failed: %v", err)
}
pkg := m["runtime"] // Note: ignore runtime_test and main packages
// Filter files by those for the current architecture/os being tested.
fileMap := map[string]bool{}
for _, f := range buildableFiles(t, ".") {
fileMap[f] = true
}
var files []*ast.File
for fname, f := range pkg.Files {
if fileMap[fname] {
files = append(files, f)
}
}
// Call go/types to analyze the runtime package.
var info types.Info
info.Types = map[ast.Expr]types.TypeAndValue{}
conf := types.Config{Importer: importer.Default()}
_, err = conf.Check("runtime", fset, files, &info)
if err != nil {
t.Fatalf("typechecking runtime failed: %v", err)
}
// Analyze all atomic.*64 callsites.
v := Visitor{t: t, fset: fset, types: info.Types, checked: checked}
ast.Walk(&v, pkg)
}
type Visitor struct {
fset *token.FileSet
types map[ast.Expr]types.TypeAndValue
checked map[string]bool
t *testing.T
}
func (v *Visitor) Visit(n ast.Node) ast.Visitor {
c, ok := n.(*ast.CallExpr)
if !ok {
return v
}
f, ok := c.Fun.(*ast.SelectorExpr)
if !ok {
return v
}
p, ok := f.X.(*ast.Ident)
if !ok {
return v
}
if p.Name != "atomic" {
return v
}
if !strings.HasSuffix(f.Sel.Name, "64") {
return v
}
a := c.Args[0]
// This is a call to atomic.XXX64(a, ...). Make sure a is aligned to 8 bytes.
// XXX = one of Load, Store, Cas, etc.
// The arg we care about the alignment of is always the first one.
if u, ok := a.(*ast.UnaryExpr); ok && u.Op == token.AND {
v.checkAddr(u.X)
return v
}
// Other cases there's nothing we can check. Assume we're ok.
v.t.Logf("unchecked atomic operation %s %v", v.fset.Position(n.Pos()), v.print(n))
return v
}
// checkAddr checks to make sure n is a properly aligned address for a 64-bit atomic operation.
func (v *Visitor) checkAddr(n ast.Node) {
switch n := n.(type) {
case *ast.IndexExpr:
// Alignment of an array element is the same as the whole array.
v.checkAddr(n.X)
return
case *ast.Ident:
key := "var " + v.print(n)
if !v.checked[key] {
v.t.Errorf("unchecked variable %s %s", v.fset.Position(n.Pos()), key)
}
return
case *ast.SelectorExpr:
t := v.types[n.X].Type
if t == nil {
// Not sure what is happening here, go/types fails to
// type the selector arg on some platforms.
return
}
if p, ok := t.(*types.Pointer); ok {
// Note: we assume here that the pointer p in p.foo is properly
// aligned. We just check that foo is at a properly aligned offset.
t = p.Elem()
} else {
v.checkAddr(n.X)
}
if t.Underlying() == t {
v.t.Errorf("analysis can't handle unnamed type %s %v", v.fset.Position(n.Pos()), t)
}
key := "field " + t.String() + "." + n.Sel.Name
if !v.checked[key] {
v.t.Errorf("unchecked field %s %s", v.fset.Position(n.Pos()), key)
}
default:
v.t.Errorf("unchecked atomic address %s %v", v.fset.Position(n.Pos()), v.print(n))
}
}
func (v *Visitor) print(n ast.Node) string {
var b strings.Builder
printer.Fprint(&b, v.fset, n)
return b.String()
}
// buildableFiles returns the list of files in the given directory
// that are actually used for the build, given GOOS/GOARCH restrictions.
func buildableFiles(t *testing.T, dir string) []string {
ctxt := build.Default
ctxt.CgoEnabled = true
pkg, err := ctxt.ImportDir(dir, 0)
if err != nil {
t.Fatalf("can't find buildable files: %v", err)
}
return pkg.GoFiles
}
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