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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package checklocks performs lock analysis to identify and flag unprotected
// access to annotated fields.
//
// For detailed usage refer to README.md in the same directory.
package checklocks
import (
"go/ast"
"go/token"
"go/types"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/buildssa"
"golang.org/x/tools/go/ssa"
)
// Analyzer is the main entrypoint.
var Analyzer = &analysis.Analyzer{
Name: "checklocks",
Doc: "checks lock preconditions on functions and fields",
Run: run,
Requires: []*analysis.Analyzer{buildssa.Analyzer},
FactTypes: []analysis.Fact{
(*atomicAlignment)(nil),
(*lockGuardFacts)(nil),
(*lockFunctionFacts)(nil),
},
}
// objectObservations tracks lock correlations.
type objectObservations struct {
counts map[types.Object]int
total int
}
// passContext is a pass with additional expected failures.
type passContext struct {
pass *analysis.Pass
failures map[positionKey]*failData
exemptions map[positionKey]struct{}
forced map[positionKey]struct{}
functions map[*ssa.Function]struct{}
observations map[types.Object]*objectObservations
}
// observationsFor retrieves observations for the given object.
func (pc *passContext) observationsFor(obj types.Object) *objectObservations {
if pc.observations == nil {
pc.observations = make(map[types.Object]*objectObservations)
}
oo, ok := pc.observations[obj]
if !ok {
oo = &objectObservations{
counts: make(map[types.Object]int),
}
pc.observations[obj] = oo
}
return oo
}
// forAllGlobals applies the given function to all globals.
func (pc *passContext) forAllGlobals(fn func(ts *ast.ValueSpec)) {
for _, f := range pc.pass.Files {
for _, decl := range f.Decls {
d, ok := decl.(*ast.GenDecl)
if !ok || d.Tok != token.VAR {
continue
}
for _, gs := range d.Specs {
fn(gs.(*ast.ValueSpec))
}
}
}
}
// forAllTypes applies the given function over all types.
func (pc *passContext) forAllTypes(fn func(ts *ast.TypeSpec)) {
for _, f := range pc.pass.Files {
for _, decl := range f.Decls {
d, ok := decl.(*ast.GenDecl)
if !ok || d.Tok != token.TYPE {
continue
}
for _, gs := range d.Specs {
fn(gs.(*ast.TypeSpec))
}
}
}
}
// forAllFunctions applies the given function over all functions.
func (pc *passContext) forAllFunctions(fn func(fn *ast.FuncDecl)) {
for _, f := range pc.pass.Files {
for _, decl := range f.Decls {
d, ok := decl.(*ast.FuncDecl)
if !ok {
continue
}
fn(d)
}
}
}
// run is the main entrypoint.
func run(pass *analysis.Pass) (interface{}, error) {
pc := &passContext{
pass: pass,
failures: make(map[positionKey]*failData),
exemptions: make(map[positionKey]struct{}),
forced: make(map[positionKey]struct{}),
functions: make(map[*ssa.Function]struct{}),
}
// Find all line failure annotations.
pc.extractLineFailures()
// Find all struct declarations and export relevant facts.
pc.forAllGlobals(func(vs *ast.ValueSpec) {
if ss, ok := vs.Type.(*ast.StructType); ok {
structType := pc.pass.TypesInfo.TypeOf(vs.Type).Underlying().(*types.Struct)
pc.structLockGuardFacts(structType, ss)
}
pc.globalLockGuardFacts(vs)
})
pc.forAllTypes(func(ts *ast.TypeSpec) {
if ss, ok := ts.Type.(*ast.StructType); ok {
structType := pc.pass.TypesInfo.TypeOf(ts.Name).Underlying().(*types.Struct)
pc.structLockGuardFacts(structType, ss)
}
})
// Check all alignments.
pc.forAllTypes(func(ts *ast.TypeSpec) {
typ, ok := pass.TypesInfo.TypeOf(ts.Name).(*types.Named)
if !ok {
return
}
pc.checkTypeAlignment(pass.Pkg, typ)
})
// Find all function declarations and export relevant facts.
pc.forAllFunctions(func(fn *ast.FuncDecl) {
pc.functionFacts(fn)
})
// Scan all code looking for invalid accesses.
state := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA)
for _, fn := range state.SrcFuncs {
// Import function facts generated above.
//
// Note that anonymous(closures) functions do not have an
// object but do show up in the SSA. They can only be invoked
// by named functions in the package, and they are analyzing
// inline on every call. Thus we skip the analysis here. They
// will be hit on calls, or picked up in the pass below.
if obj := fn.Object(); obj == nil {
continue
}
var lff lockFunctionFacts
pc.pass.ImportObjectFact(fn.Object(), &lff)
// Check the basic blocks in the function.
pc.checkFunction(nil, fn, &lff, nil, false /* force */)
}
for _, fn := range state.SrcFuncs {
// Ensure all anonymous functions are hit. They are not
// permitted to have any lock preconditions.
if obj := fn.Object(); obj != nil {
continue
}
var nolff lockFunctionFacts
pc.checkFunction(nil, fn, &nolff, nil, false /* force */)
}
// Check for inferred checklocks annotations.
pc.checkInferred()
// Check for expected failures.
pc.checkFailures()
return nil, nil
}
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