+++ /dev/null
-// Copyright 2015 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 cgocall defines an Analyzer that detects some violations of
-// the cgo pointer passing rules.
-package cgocall
-
-import (
- "fmt"
- "go/ast"
- "go/format"
- "go/parser"
- "go/token"
- "go/types"
- "log"
- "os"
- "strconv"
-
- "golang.org/x/tools/go/analysis"
- "golang.org/x/tools/go/analysis/passes/internal/analysisutil"
-)
-
-const debug = false
-
-const Doc = `detect some violations of the cgo pointer passing rules
-
-Check for invalid cgo pointer passing.
-This looks for code that uses cgo to call C code passing values
-whose types are almost always invalid according to the cgo pointer
-sharing rules.
-Specifically, it warns about attempts to pass a Go chan, map, func,
-or slice to C, either directly, or via a pointer, array, or struct.`
-
-var Analyzer = &analysis.Analyzer{
- Name: "cgocall",
- Doc: Doc,
- RunDespiteErrors: true,
- Run: run,
-}
-
-func run(pass *analysis.Pass) (interface{}, error) {
- if !analysisutil.Imports(pass.Pkg, "runtime/cgo") {
- return nil, nil // doesn't use cgo
- }
-
- cgofiles, info, err := typeCheckCgoSourceFiles(pass.Fset, pass.Pkg, pass.Files, pass.TypesInfo, pass.TypesSizes)
- if err != nil {
- return nil, err
- }
- for _, f := range cgofiles {
- checkCgo(pass.Fset, f, info, pass.Reportf)
- }
- return nil, nil
-}
-
-func checkCgo(fset *token.FileSet, f *ast.File, info *types.Info, reportf func(token.Pos, string, ...interface{})) {
- ast.Inspect(f, func(n ast.Node) bool {
- call, ok := n.(*ast.CallExpr)
- if !ok {
- return true
- }
-
- // Is this a C.f() call?
- var name string
- if sel, ok := analysisutil.Unparen(call.Fun).(*ast.SelectorExpr); ok {
- if id, ok := sel.X.(*ast.Ident); ok && id.Name == "C" {
- name = sel.Sel.Name
- }
- }
- if name == "" {
- return true // not a call we need to check
- }
-
- // A call to C.CBytes passes a pointer but is always safe.
- if name == "CBytes" {
- return true
- }
-
- if debug {
- log.Printf("%s: call to C.%s", fset.Position(call.Lparen), name)
- }
-
- for _, arg := range call.Args {
- if !typeOKForCgoCall(cgoBaseType(info, arg), make(map[types.Type]bool)) {
- reportf(arg.Pos(), "possibly passing Go type with embedded pointer to C")
- break
- }
-
- // Check for passing the address of a bad type.
- if conv, ok := arg.(*ast.CallExpr); ok && len(conv.Args) == 1 &&
- isUnsafePointer(info, conv.Fun) {
- arg = conv.Args[0]
- }
- if u, ok := arg.(*ast.UnaryExpr); ok && u.Op == token.AND {
- if !typeOKForCgoCall(cgoBaseType(info, u.X), make(map[types.Type]bool)) {
- reportf(arg.Pos(), "possibly passing Go type with embedded pointer to C")
- break
- }
- }
- }
- return true
- })
-}
-
-// typeCheckCgoSourceFiles returns type-checked syntax trees for the raw
-// cgo files of a package (those that import "C"). Such files are not
-// Go, so there may be gaps in type information around C.f references.
-//
-// This checker was initially written in vet to inspect raw cgo source
-// files using partial type information. However, Analyzers in the new
-// analysis API are presented with the type-checked, "cooked" Go ASTs
-// resulting from cgo-processing files, so we must choose between
-// working with the cooked file generated by cgo (which was tried but
-// proved fragile) or locating the raw cgo file (e.g. from //line
-// directives) and working with that, as we now do.
-//
-// Specifically, we must type-check the raw cgo source files (or at
-// least the subtrees needed for this analyzer) in an environment that
-// simulates the rest of the already type-checked package.
-//
-// For example, for each raw cgo source file in the original package,
-// such as this one:
-//
-// package p
-// import "C"
-// import "fmt"
-// type T int
-// const k = 3
-// var x, y = fmt.Println()
-// func f() { ... }
-// func g() { ... C.malloc(k) ... }
-// func (T) f(int) string { ... }
-//
-// we synthesize a new ast.File, shown below, that dot-imports the
-// original "cooked" package using a special name ("·this·"), so that all
-// references to package members resolve correctly. (References to
-// unexported names cause an "unexported" error, which we ignore.)
-//
-// To avoid shadowing names imported from the cooked package,
-// package-level declarations in the new source file are modified so
-// that they do not declare any names.
-// (The cgocall analysis is concerned with uses, not declarations.)
-// Specifically, type declarations are discarded;
-// all names in each var and const declaration are blanked out;
-// each method is turned into a regular function by turning
-// the receiver into the first parameter;
-// and all functions are renamed to "_".
-//
-// package p
-// import . "·this·" // declares T, k, x, y, f, g, T.f
-// import "C"
-// import "fmt"
-// const _ = 3
-// var _, _ = fmt.Println()
-// func _() { ... }
-// func _() { ... C.malloc(k) ... }
-// func _(T, int) string { ... }
-//
-// In this way, the raw function bodies and const/var initializer
-// expressions are preserved but refer to the "cooked" objects imported
-// from "·this·", and none of the transformed package-level declarations
-// actually declares anything. In the example above, the reference to k
-// in the argument of the call to C.malloc resolves to "·this·".k, which
-// has an accurate type.
-//
-// This approach could in principle be generalized to more complex
-// analyses on raw cgo files. One could synthesize a "C" package so that
-// C.f would resolve to "·this·"._C_func_f, for example. But we have
-// limited ourselves here to preserving function bodies and initializer
-// expressions since that is all that the cgocall analyzer needs.
-//
-func typeCheckCgoSourceFiles(fset *token.FileSet, pkg *types.Package, files []*ast.File, info *types.Info, sizes types.Sizes) ([]*ast.File, *types.Info, error) {
- const thispkg = "·this·"
-
- // Which files are cgo files?
- var cgoFiles []*ast.File
- importMap := map[string]*types.Package{thispkg: pkg}
- for _, raw := range files {
- // If f is a cgo-generated file, Position reports
- // the original file, honoring //line directives.
- filename := fset.Position(raw.Pos()).Filename
- f, err := parser.ParseFile(fset, filename, nil, parser.Mode(0))
- if err != nil {
- return nil, nil, fmt.Errorf("can't parse raw cgo file: %v", err)
- }
- found := false
- for _, spec := range f.Imports {
- if spec.Path.Value == `"C"` {
- found = true
- break
- }
- }
- if !found {
- continue // not a cgo file
- }
-
- // Record the original import map.
- for _, spec := range raw.Imports {
- path, _ := strconv.Unquote(spec.Path.Value)
- importMap[path] = imported(info, spec)
- }
-
- // Add special dot-import declaration:
- // import . "·this·"
- var decls []ast.Decl
- decls = append(decls, &ast.GenDecl{
- Tok: token.IMPORT,
- Specs: []ast.Spec{
- &ast.ImportSpec{
- Name: &ast.Ident{Name: "."},
- Path: &ast.BasicLit{
- Kind: token.STRING,
- Value: strconv.Quote(thispkg),
- },
- },
- },
- })
-
- // Transform declarations from the raw cgo file.
- for _, decl := range f.Decls {
- switch decl := decl.(type) {
- case *ast.GenDecl:
- switch decl.Tok {
- case token.TYPE:
- // Discard type declarations.
- continue
- case token.IMPORT:
- // Keep imports.
- case token.VAR, token.CONST:
- // Blank the declared var/const names.
- for _, spec := range decl.Specs {
- spec := spec.(*ast.ValueSpec)
- for i := range spec.Names {
- spec.Names[i].Name = "_"
- }
- }
- }
- case *ast.FuncDecl:
- // Blank the declared func name.
- decl.Name.Name = "_"
-
- // Turn a method receiver: func (T) f(P) R {...}
- // into regular parameter: func _(T, P) R {...}
- if decl.Recv != nil {
- var params []*ast.Field
- params = append(params, decl.Recv.List...)
- params = append(params, decl.Type.Params.List...)
- decl.Type.Params.List = params
- decl.Recv = nil
- }
- }
- decls = append(decls, decl)
- }
- f.Decls = decls
- if debug {
- format.Node(os.Stderr, fset, f) // debugging
- }
- cgoFiles = append(cgoFiles, f)
- }
- if cgoFiles == nil {
- return nil, nil, nil // nothing to do (can't happen?)
- }
-
- // Type-check the synthetic files.
- tc := &types.Config{
- FakeImportC: true,
- Importer: importerFunc(func(path string) (*types.Package, error) {
- return importMap[path], nil
- }),
- Sizes: sizes,
- Error: func(error) {}, // ignore errors (e.g. unused import)
- }
-
- // It's tempting to record the new types in the
- // existing pass.TypesInfo, but we don't own it.
- altInfo := &types.Info{
- Types: make(map[ast.Expr]types.TypeAndValue),
- }
- tc.Check(pkg.Path(), fset, cgoFiles, altInfo)
-
- return cgoFiles, altInfo, nil
-}
-
-// cgoBaseType tries to look through type conversions involving
-// unsafe.Pointer to find the real type. It converts:
-// unsafe.Pointer(x) => x
-// *(*unsafe.Pointer)(unsafe.Pointer(&x)) => x
-func cgoBaseType(info *types.Info, arg ast.Expr) types.Type {
- switch arg := arg.(type) {
- case *ast.CallExpr:
- if len(arg.Args) == 1 && isUnsafePointer(info, arg.Fun) {
- return cgoBaseType(info, arg.Args[0])
- }
- case *ast.StarExpr:
- call, ok := arg.X.(*ast.CallExpr)
- if !ok || len(call.Args) != 1 {
- break
- }
- // Here arg is *f(v).
- t := info.Types[call.Fun].Type
- if t == nil {
- break
- }
- ptr, ok := t.Underlying().(*types.Pointer)
- if !ok {
- break
- }
- // Here arg is *(*p)(v)
- elem, ok := ptr.Elem().Underlying().(*types.Basic)
- if !ok || elem.Kind() != types.UnsafePointer {
- break
- }
- // Here arg is *(*unsafe.Pointer)(v)
- call, ok = call.Args[0].(*ast.CallExpr)
- if !ok || len(call.Args) != 1 {
- break
- }
- // Here arg is *(*unsafe.Pointer)(f(v))
- if !isUnsafePointer(info, call.Fun) {
- break
- }
- // Here arg is *(*unsafe.Pointer)(unsafe.Pointer(v))
- u, ok := call.Args[0].(*ast.UnaryExpr)
- if !ok || u.Op != token.AND {
- break
- }
- // Here arg is *(*unsafe.Pointer)(unsafe.Pointer(&v))
- return cgoBaseType(info, u.X)
- }
-
- return info.Types[arg].Type
-}
-
-// typeOKForCgoCall reports whether the type of arg is OK to pass to a
-// C function using cgo. This is not true for Go types with embedded
-// pointers. m is used to avoid infinite recursion on recursive types.
-func typeOKForCgoCall(t types.Type, m map[types.Type]bool) bool {
- if t == nil || m[t] {
- return true
- }
- m[t] = true
- switch t := t.Underlying().(type) {
- case *types.Chan, *types.Map, *types.Signature, *types.Slice:
- return false
- case *types.Pointer:
- return typeOKForCgoCall(t.Elem(), m)
- case *types.Array:
- return typeOKForCgoCall(t.Elem(), m)
- case *types.Struct:
- for i := 0; i < t.NumFields(); i++ {
- if !typeOKForCgoCall(t.Field(i).Type(), m) {
- return false
- }
- }
- }
- return true
-}
-
-func isUnsafePointer(info *types.Info, e ast.Expr) bool {
- t := info.Types[e].Type
- return t != nil && t.Underlying() == types.Typ[types.UnsafePointer]
-}
-
-type importerFunc func(path string) (*types.Package, error)
-
-func (f importerFunc) Import(path string) (*types.Package, error) { return f(path) }
-
-// TODO(adonovan): make this a library function or method of Info.
-func imported(info *types.Info, spec *ast.ImportSpec) *types.Package {
- obj, ok := info.Implicits[spec]
- if !ok {
- obj = info.Defs[spec.Name] // renaming import
- }
- return obj.(*types.PkgName).Imported()
-}
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