--- /dev/null
+// Copyright 2019 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 atomicalign defines an Analyzer that checks for non-64-bit-aligned
+// arguments to sync/atomic functions. On non-32-bit platforms, those functions
+// panic if their argument variables are not 64-bit aligned. It is therefore
+// the caller's responsibility to arrange for 64-bit alignment of such variables.
+// See https://golang.org/pkg/sync/atomic/#pkg-note-BUG
+package atomicalign
+
+import (
+ "go/ast"
+ "go/token"
+ "go/types"
+
+ "golang.org/x/tools/go/analysis"
+ "golang.org/x/tools/go/analysis/passes/inspect"
+ "golang.org/x/tools/go/analysis/passes/internal/analysisutil"
+ "golang.org/x/tools/go/ast/inspector"
+)
+
+const Doc = "check for non-64-bits-aligned arguments to sync/atomic functions"
+
+var Analyzer = &analysis.Analyzer{
+ Name: "atomicalign",
+ Doc: Doc,
+ Requires: []*analysis.Analyzer{inspect.Analyzer},
+ Run: run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+ if 8*pass.TypesSizes.Sizeof(types.Typ[types.Uintptr]) == 64 {
+ return nil, nil // 64-bit platform
+ }
+ if !analysisutil.Imports(pass.Pkg, "sync/atomic") {
+ return nil, nil // doesn't directly import sync/atomic
+ }
+
+ inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+ nodeFilter := []ast.Node{
+ (*ast.CallExpr)(nil),
+ }
+
+ inspect.Preorder(nodeFilter, func(node ast.Node) {
+ call := node.(*ast.CallExpr)
+ sel, ok := call.Fun.(*ast.SelectorExpr)
+ if !ok {
+ return
+ }
+ pkgIdent, ok := sel.X.(*ast.Ident)
+ if !ok {
+ return
+ }
+ pkgName, ok := pass.TypesInfo.Uses[pkgIdent].(*types.PkgName)
+ if !ok || pkgName.Imported().Path() != "sync/atomic" {
+ return
+ }
+
+ switch sel.Sel.Name {
+ case "AddInt64", "AddUint64",
+ "LoadInt64", "LoadUint64",
+ "StoreInt64", "StoreUint64",
+ "SwapInt64", "SwapUint64",
+ "CompareAndSwapInt64", "CompareAndSwapUint64":
+
+ // For all the listed functions, the expression to check is always the first function argument.
+ check64BitAlignment(pass, sel.Sel.Name, call.Args[0])
+ }
+ })
+
+ return nil, nil
+}
+
+func check64BitAlignment(pass *analysis.Pass, funcName string, arg ast.Expr) {
+ // Checks the argument is made of the address operator (&) applied to
+ // to a struct field (as opposed to a variable as the first word of
+ // uint64 and int64 variables can be relied upon to be 64-bit aligned.
+ unary, ok := arg.(*ast.UnaryExpr)
+ if !ok || unary.Op != token.AND {
+ return
+ }
+
+ // Retrieve the types.Struct in order to get the offset of the
+ // atomically accessed field.
+ sel, ok := unary.X.(*ast.SelectorExpr)
+ if !ok {
+ return
+ }
+ tvar, ok := pass.TypesInfo.Selections[sel].Obj().(*types.Var)
+ if !ok || !tvar.IsField() {
+ return
+ }
+
+ stype, ok := pass.TypesInfo.Types[sel.X].Type.Underlying().(*types.Struct)
+ if !ok {
+ return
+ }
+
+ var offset int64
+ var fields []*types.Var
+ for i := 0; i < stype.NumFields(); i++ {
+ f := stype.Field(i)
+ fields = append(fields, f)
+ if f == tvar {
+ // We're done, this is the field we were looking for,
+ // no need to fill the fields slice further.
+ offset = pass.TypesSizes.Offsetsof(fields)[i]
+ break
+ }
+ }
+ if offset&7 == 0 {
+ return // 64-bit aligned
+ }
+
+ pass.ReportRangef(arg, "address of non 64-bit aligned field .%s passed to atomic.%s", tvar.Name(), funcName)
+}