1 files changed, 77 insertions, 681 deletions

diff --git a/tools/checklocks/checklocks.go b/tools/checklocks/checklocks.go
index 1e877d394..180f8873f 100644
--- a/tools/checklocks/checklocks.go
+++ b/tools/checklocks/checklocks.go
@@ -13,32 +13,19 @@
 // limitations under the License.
 
 // Package checklocks performs lock analysis to identify and flag unprotected
-// access to field annotated with a '// +checklocks:<mutex-name>' annotation.
+// access to annotated fields.
 //
-// For detailed ussage refer to README.md in the same directory.
+// For detailed usage refer to README.md in the same directory.
 package checklocks
 
 import (
-	"bytes"
-	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
-	"reflect"
-	"regexp"
-	"strconv"
-	"strings"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/buildssa"
 	"golang.org/x/tools/go/ssa"
-	"gvisor.dev/gvisor/pkg/log"
-)
-
-const (
-	checkLocksAnnotation = "// +checklocks:"
-	checkLocksIgnore     = "// +checklocksignore"
-	checkLocksFail       = "// +checklocksfail"
 )
 
 // Analyzer is the main entrypoint.
@@ -47,712 +34,121 @@ var Analyzer = &analysis.Analyzer{
 	Doc:       "checks lock preconditions on functions and fields",
 	Run:       run,
 	Requires:  []*analysis.Analyzer{buildssa.Analyzer},
-	FactTypes: []analysis.Fact{(*lockFieldFacts)(nil), (*lockFunctionFacts)(nil)},
-}
-
-// lockFieldFacts apply on every struct field protected by a lock or that is a
-// lock.
-type lockFieldFacts struct {
-	// GuardedBy tracks the names and field numbers that guard this field.
-	GuardedBy map[string]int
-
-	// IsMutex is true if the field is of type sync.Mutex.
-	IsMutex bool
-
-	// IsRWMutex is true if the field is of type sync.RWMutex.
-	IsRWMutex bool
-
-	// FieldNumber is the number of this field in the struct.
-	FieldNumber int
-}
-
-// AFact implements analysis.Fact.AFact.
-func (*lockFieldFacts) AFact() {}
-
-type functionGuard struct {
-	// ParameterNumber is the index of the object that contains the guarding mutex.
-	// This is required during SSA analysis as field names and parameters names are
-	// not available in SSA. For example, from the example below ParameterNumber would
-	// be 1 and FieldNumber would correspond to the field number of 'mu' within b's type.
-	//
-	// //+checklocks:b.mu
-	// func (a *A) method(b *B, c *C) {
-	//   ...
-	// }
-	ParameterNumber int
-
-	// FieldNumber is the field index of the mutex in the parameter's struct
-	// type. Refer to example above for more details.
-	FieldNumber int
-}
-
-// lockFunctionFacts apply on every method.
-type lockFunctionFacts struct {
-	// GuardedBy tracks the names and number of parameter (including receiver)
-	// lockFuncfields that guard calls to this function.
-	// The key is the name specified in the checklocks annotation. e.g given
-	// the following code.
-	// ```
-	// type A struct {
-	//   mu sync.Mutex
-	//   a int
-	// }
-	//
-	// // +checklocks:a.mu
-	// func xyz(a *A) {..}
-	// ```
-	//
-	// '`+checklocks:a.mu' will result in an entry in this map as shown below.
-	// GuardedBy: {"a.mu" => {ParameterNumber: 0, FieldNumber: 0}
-	GuardedBy map[string]functionGuard
-}
-
-// AFact implements analysis.Fact.AFact.
-func (*lockFunctionFacts) AFact() {}
-
-type positionKey string
-
-// toPositionKey converts from a token.Position to a key we can use to track
-// failures as the position of the failure annotation is not the same as the
-// position of the actual failure (different column/offsets). Hence we ignore
-// these fields and only use the file/line numbers to track failures.
-func toPositionKey(position token.Position) positionKey {
-	return positionKey(fmt.Sprintf("%s:%d", position.Filename, position.Line))
-}
-
-type failData struct {
-	pos   token.Pos
-	count int
-}
-
-func (f failData) String() string {
-	return fmt.Sprintf("pos: %d, count: %d", f.pos, f.count)
+	FactTypes: []analysis.Fact{(*atomicAlignment)(nil), (*lockFieldFacts)(nil), (*lockGuardFacts)(nil), (*lockFunctionFacts)(nil)},
 }
 
+// passContext is a pass with additional expected failures.
 type passContext struct {
-	pass *analysis.Pass
-
-	// exemptions tracks functions that should be exempted from lock checking due
-	// to '// +checklocksignore' annotation.
-	exemptions map[types.Object]struct{}
-
-	failures map[positionKey]*failData
+	pass       *analysis.Pass
+	failures   map[positionKey]*failData
+	exemptions map[positionKey]struct{}
+	forced     map[positionKey]struct{}
+	functions  map[*ssa.Function]struct{}
 }
 
-var (
-	mutexRE   = regexp.MustCompile("((.*/)|^)sync.(CrossGoroutineMutex|Mutex)")
-	rwMutexRE = regexp.MustCompile("((.*/)|^)sync.(CrossGoroutineRWMutex|RWMutex)")
-)
-
-func (pc *passContext) extractFieldAnnotations(field *ast.Field, fieldType *types.Var) *lockFieldFacts {
-	s := fieldType.Type().String()
-	// We use HasSuffix below because fieldType can be fully qualified with the
-	// package name eg for the gvisor sync package mutex fields have the type:
-	// "<package path>/sync/sync.Mutex"
-	switch {
-	case mutexRE.Match([]byte(s)):
-		return &lockFieldFacts{IsMutex: true}
-	case rwMutexRE.Match([]byte(s)):
-		return &lockFieldFacts{IsRWMutex: true}
-	default:
-	}
-	if field.Doc == nil {
-		return nil
-	}
-	fieldFacts := &lockFieldFacts{GuardedBy: make(map[string]int)}
-	for _, l := range field.Doc.List {
-		if strings.HasPrefix(l.Text, checkLocksAnnotation) {
-			guardName := strings.TrimPrefix(l.Text, checkLocksAnnotation)
-			if _, ok := fieldFacts.GuardedBy[guardName]; ok {
-				pc.pass.Reportf(field.Pos(), "annotation %s specified more than once.", l.Text)
-				continue
-			}
-			fieldFacts.GuardedBy[guardName] = -1
-		}
-	}
-
-	return fieldFacts
-}
-
-func (pc *passContext) findField(v ssa.Value, fieldNumber int) types.Object {
-	structType, ok := v.Type().Underlying().(*types.Struct)
-	if !ok {
-		structType = v.Type().Underlying().(*types.Pointer).Elem().Underlying().(*types.Struct)
-	}
-	return structType.Field(fieldNumber)
-}
-
-// findAndExportStructFacts finds any struct fields that are annotated with the
-// "// +checklocks:" annotation and exports relevant facts about the fields to
-// be used in later analysis.
-func (pc *passContext) findAndExportStructFacts(ss *ast.StructType, structType *types.Struct) {
-	type fieldRef struct {
-		fieldObj *types.Var
-		facts    *lockFieldFacts
-	}
-	mutexes := make(map[string]*fieldRef)
-	rwMutexes := make(map[string]*fieldRef)
-	guardedFields := make(map[string]*fieldRef)
-	for i, field := range ss.Fields.List {
-		fieldObj := structType.Field(i)
-		fieldFacts := pc.extractFieldAnnotations(field, fieldObj)
-		if fieldFacts == nil {
-			continue
-		}
-		fieldFacts.FieldNumber = i
-
-		ref := &fieldRef{fieldObj, fieldFacts}
-		if fieldFacts.IsMutex {
-			mutexes[fieldObj.Name()] = ref
-		}
-		if fieldFacts.IsRWMutex {
-			rwMutexes[fieldObj.Name()] = ref
-		}
-		if len(fieldFacts.GuardedBy) != 0 {
-			guardedFields[fieldObj.Name()] = ref
-		}
-	}
-
-	// Export facts about all mutexes.
-	for _, f := range mutexes {
-		pc.pass.ExportObjectFact(f.fieldObj, f.facts)
-	}
-	// Export facts about all rwMutexes.
-	for _, f := range rwMutexes {
-		pc.pass.ExportObjectFact(f.fieldObj, f.facts)
-	}
-
-	// Validate that guarded fields annotations refer to actual mutexes or
-	// rwMutexes in the struct.
-	for _, gf := range guardedFields {
-		for g := range gf.facts.GuardedBy {
-			if f, ok := mutexes[g]; ok {
-				gf.facts.GuardedBy[g] = f.facts.FieldNumber
-			} else if f, ok := rwMutexes[g]; ok {
-				gf.facts.GuardedBy[g] = f.facts.FieldNumber
-			} else {
-				pc.maybeFail(gf.fieldObj.Pos(), false /* isExempted */, "invalid mutex guard, no such mutex %s in struct %s", g, structType.String())
-				continue
-			}
-			// Export guarded field fact.
-			pc.pass.ExportObjectFact(gf.fieldObj, gf.facts)
-		}
-	}
-}
-
-func (pc *passContext) findAndExportFuncFacts(d *ast.FuncDecl) {
-	log.Debugf("finding and exporting function facts\n")
-	// for each function definition, check for +checklocks:mu annotation, which
-	// means that the function must be called with that lock held.
-	fnObj := pc.pass.TypesInfo.ObjectOf(d.Name)
-	funcFacts := lockFunctionFacts{GuardedBy: make(map[string]functionGuard)}
-	var (
-		ignore    bool
-		ignorePos token.Pos
-	)
-
-outerLoop:
-	for _, l := range d.Doc.List {
-		if strings.HasPrefix(l.Text, checkLocksIgnore) {
-			pc.exemptions[fnObj] = struct{}{}
-			ignore = true
-			ignorePos = l.Pos()
-			continue
-		}
-		if strings.HasPrefix(l.Text, checkLocksAnnotation) {
-			guardName := strings.TrimPrefix(l.Text, checkLocksAnnotation)
-			if _, ok := funcFacts.GuardedBy[guardName]; ok {
-				pc.pass.Reportf(l.Pos(), "annotation %s specified more than once.", l.Text)
-				continue
-			}
-
-			found := false
-			x := strings.Split(guardName, ".")
-			if len(x) != 2 {
-				pc.pass.Reportf(l.Pos(), "checklocks mutex annotation should be of the form 'a.b'")
+// 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
 			}
-			paramName, fieldName := x[0], x[1]
-			log.Debugf("paramName: %s, fieldName: %s", paramName, fieldName)
-			var paramList []*ast.Field
-			if d.Recv != nil {
-				paramList = append(paramList, d.Recv.List...)
-			}
-			if d.Type.Params != nil {
-				paramList = append(paramList, d.Type.Params.List...)
-			}
-			for paramNum, field := range paramList {
-				log.Debugf("field names: %+v", field.Names)
-				if len(field.Names) == 0 {
-					log.Debugf("skipping because parameter is unnamed", paramName)
-					continue
-				}
-				nameExists := false
-				for _, name := range field.Names {
-					if name.Name == paramName {
-						nameExists = true
-					}
-				}
-				if !nameExists {
-					log.Debugf("skipping because parameter name(s) does not match : %s", paramName)
-					continue
-				}
-				ptrType, ok := pc.pass.TypesInfo.TypeOf(field.Type).Underlying().(*types.Pointer)
-				if !ok {
-					// Since mutexes cannot be copied we only care about parameters that
-					// are pointer types when checking for guards.
-					pc.pass.Reportf(l.Pos(), "annotation %s incorrectly specified, parameter name does not refer to a pointer type", l.Text)
-					continue outerLoop
-				}
-
-				structType, ok := ptrType.Elem().Underlying().(*types.Struct)
-				if !ok {
-					pc.pass.Reportf(l.Pos(), "annotation %s incorrectly specified, parameter name does not refer to a pointer to a struct", l.Text)
-					continue outerLoop
-				}
-
-				for i := 0; i < structType.NumFields(); i++ {
-					if structType.Field(i).Name() == fieldName {
-						var fieldFacts lockFieldFacts
-						pc.pass.ImportObjectFact(structType.Field(i), &fieldFacts)
-						if !fieldFacts.IsMutex && !fieldFacts.IsRWMutex {
-							pc.pass.Reportf(l.Pos(), "field %s of param %s is not a mutex or an rwmutex", paramName, structType.Field(i))
-							continue outerLoop
-						}
-						funcFacts.GuardedBy[guardName] = functionGuard{ParameterNumber: paramNum, FieldNumber: i}
-						found = true
-						continue outerLoop
-					}
-				}
-				if !found {
-					pc.pass.Reportf(l.Pos(), "annotation refers to a non-existent field %s in %s", guardName, structType)
-					continue outerLoop
-				}
-			}
-			if !found {
-				pc.pass.Reportf(l.Pos(), "annotation refers to a non-existent parameter %s", paramName)
-			}
-		}
-	}
-
-	if len(funcFacts.GuardedBy) == 0 {
-		return
-	}
-	if ignore {
-		pc.pass.Reportf(ignorePos, "//+checklocksignore cannot be specified with other annotations on the function")
-	}
-	funcObj, ok := pc.pass.TypesInfo.Defs[d.Name].(*types.Func)
-	if !ok {
-		panic(fmt.Sprintf("function type information missing for %+v", d))
-	}
-	log.Debugf("export fact for d: %+v, funcObj: %+v, funcFacts: %+v\n", d, funcObj, funcFacts)
-	pc.pass.ExportObjectFact(funcObj, &funcFacts)
-}
-
-type mutexState struct {
-	// lockedMutexes is used to track which mutexes in a given struct are
-	// currently locked using the field number of the mutex as the key.
-	lockedMutexes map[int]struct{}
-}
-
-// locksHeld tracks all currently held locks.
-type locksHeld struct {
-	locks map[ssa.Value]mutexState
-}
-
-// Same returns true if the locks held by other and l are the same.
-func (l *locksHeld) Same(other *locksHeld) bool {
-	return reflect.DeepEqual(l.locks, other.locks)
-}
-
-// Copy creates a copy of all the lock state held by l.
-func (l *locksHeld) Copy() *locksHeld {
-	out := &locksHeld{locks: make(map[ssa.Value]mutexState)}
-	for ssaVal, mState := range l.locks {
-		newLM := make(map[int]struct{})
-		for k, v := range mState.lockedMutexes {
-			newLM[k] = v
-		}
-		out.locks[ssaVal] = mutexState{lockedMutexes: newLM}
-	}
-	return out
-}
-
-func isAlias(first, second ssa.Value) bool {
-	if first == second {
-		return true
-	}
-	switch x := first.(type) {
-	case *ssa.Field:
-		if y, ok := second.(*ssa.Field); ok {
-			return x.Field == y.Field && isAlias(x.X, y.X)
-		}
-	case *ssa.FieldAddr:
-		if y, ok := second.(*ssa.FieldAddr); ok {
-			return x.Field == y.Field && isAlias(x.X, y.X)
-		}
-	case *ssa.Index:
-		if y, ok := second.(*ssa.Index); ok {
-			return isAlias(x.Index, y.Index) && isAlias(x.X, y.X)
-		}
-	case *ssa.IndexAddr:
-		if y, ok := second.(*ssa.IndexAddr); ok {
-			return isAlias(x.Index, y.Index) && isAlias(x.X, y.X)
-		}
-	case *ssa.UnOp:
-		if y, ok := second.(*ssa.UnOp); ok {
-			return isAlias(x.X, y.X)
-		}
-	}
-	return false
-}
-
-// checkBasicBlocks traverses the control flow graph starting at a set of given
-// block and checks each instruction for allowed operations.
-//
-// funcFact are the exported facts for the enclosing function for these basic
-// blocks.
-func (pc *passContext) checkBasicBlocks(blocks []*ssa.BasicBlock, recoverBlock *ssa.BasicBlock, fn *ssa.Function, funcFact lockFunctionFacts) {
-	if len(blocks) == 0 {
-		return
-	}
-
-	// mutexes is used to track currently locked sync.Mutexes/sync.RWMutexes for a
-	// given *struct identified by ssa.Value.
-	seen := make(map[*ssa.BasicBlock]*locksHeld)
-	var scan func(block *ssa.BasicBlock, parent *locksHeld)
-	scan = func(block *ssa.BasicBlock, parent *locksHeld) {
-		_, isExempted := pc.exemptions[block.Parent().Object()]
-		if oldLocksHeld, ok := seen[block]; ok {
-			if oldLocksHeld.Same(parent) {
-				return
-			}
-			pc.maybeFail(block.Instrs[0].Pos(), isExempted, "failure entering a block %+v with different sets of lock held, oldLocks: %+v, parentLocks: %+v", block, oldLocksHeld, parent)
-			return
-		}
-		seen[block] = parent
-		var lh = parent.Copy()
-		for _, inst := range block.Instrs {
-			pc.checkInstruction(inst, isExempted, lh)
-		}
-		for _, b := range block.Succs {
-			scan(b, lh)
-		}
-	}
-
-	// Initialize lh with any preconditions that require locks to be held for the
-	// method to be invoked.
-	lh := &locksHeld{locks: make(map[ssa.Value]mutexState)}
-	for _, fg := range funcFact.GuardedBy {
-		// The first is the method object itself so we skip that when looking
-		// for receiver/function parameters.
-		log.Debugf("fn: %s, fn.Operands() == %+v", fn, fn.Operands(nil))
-		r := fn.Params[fg.ParameterNumber]
-		guardObj := findField(r, fg.FieldNumber)
-		var fieldFacts lockFieldFacts
-		pc.pass.ImportObjectFact(guardObj, &fieldFacts)
-		if fieldFacts.IsMutex || fieldFacts.IsRWMutex {
-			m, ok := lh.locks[r]
-			if !ok {
-				m = mutexState{lockedMutexes: make(map[int]struct{})}
-				lh.locks[r] = m
+			for _, gs := range d.Specs {
+				fn(gs.(*ast.TypeSpec))
 			}
-			m.lockedMutexes[fieldFacts.FieldNumber] = struct{}{}
-		} else {
-			panic(fmt.Sprintf("function: %+v has an invalid guard that is not a mutex: %+v", fn, guardObj))
-		}
-	}
-
-	// Start scanning from the first basic block.
-	scan(blocks[0], lh)
-
-	// Validate that all blocks were touched.
-	for _, b := range blocks {
-		if _, ok := seen[b]; !ok && b != recoverBlock {
-			panic(fmt.Sprintf("block %+v was not visited during checkBasicBlocks", b))
-		}
-	}
-}
-
-func (pc *passContext) checkInstruction(inst ssa.Instruction, isExempted bool, lh *locksHeld) {
-	log.Debugf("checking instruction: %s, isExempted: %t", inst, isExempted)
-	switch x := inst.(type) {
-	case *ssa.Field:
-		pc.checkFieldAccess(inst, x.X, x.Field, isExempted, lh)
-	case *ssa.FieldAddr:
-		pc.checkFieldAccess(inst, x.X, x.Field, isExempted, lh)
-	case *ssa.Call:
-		pc.checkFunctionCall(x, isExempted, lh)
-	}
-}
-
-func findField(v ssa.Value, field int) types.Object {
-	structType, ok := v.Type().Underlying().(*types.Struct)
-	if !ok {
-		ptrType, ok := v.Type().Underlying().(*types.Pointer)
-		if !ok {
-			return nil
-		}
-		structType = ptrType.Elem().Underlying().(*types.Struct)
-	}
-	return structType.Field(field)
-}
-
-func (pc *passContext) maybeFail(pos token.Pos, isExempted bool, fmtStr string, args ...interface{}) {
-	posKey := toPositionKey(pc.pass.Fset.Position(pos))
-	log.Debugf("maybeFail: pos: %d, positionKey: %s", pos, posKey)
-	if fData, ok := pc.failures[posKey]; ok {
-		fData.count--
-		if fData.count == 0 {
-			delete(pc.failures, posKey)
 		}
-		return
-	}
-	if !isExempted {
-		pc.pass.Reportf(pos, fmt.Sprintf(fmtStr, args...))
 	}
 }
 
-func (pc *passContext) checkFieldAccess(inst ssa.Instruction, structObj ssa.Value, field int, isExempted bool, lh *locksHeld) {
-	var fieldFacts lockFieldFacts
-	fieldObj := findField(structObj, field)
-	pc.pass.ImportObjectFact(fieldObj, &fieldFacts)
-	log.Debugf("fieldObj: %s, fieldFacts: %+v", fieldObj, fieldFacts)
-	for _, guardFieldNumber := range fieldFacts.GuardedBy {
-		guardObj := findField(structObj, guardFieldNumber)
-		var guardfieldFacts lockFieldFacts
-		pc.pass.ImportObjectFact(guardObj, &guardfieldFacts)
-		log.Debugf("guardObj: %s, guardFieldFacts: %+v", guardObj, guardfieldFacts)
-		if guardfieldFacts.IsMutex || guardfieldFacts.IsRWMutex {
-			log.Debugf("guard is a mutex")
-			m, ok := lh.locks[structObj]
+// 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 {
-				pc.maybeFail(inst.Pos(), isExempted, "invalid field access, %s must be locked when accessing %s", guardObj.Name(), fieldObj.Name())
-				continue
-			}
-			if _, ok := m.lockedMutexes[guardfieldFacts.FieldNumber]; !ok {
-				pc.maybeFail(inst.Pos(), isExempted, "invalid field access, %s must be locked when accessing %s", guardObj.Name(), fieldObj.Name())
-			}
-		} else {
-			panic("incorrect guard that is not a mutex or an RWMutex")
-		}
-	}
-}
-
-func (pc *passContext) checkFunctionCall(call *ssa.Call, isExempted bool, lh *locksHeld) {
-	// See: https://godoc.org/golang.org/x/tools/go/ssa#CallCommon
-	//
-	// 1. "call" mode: when Method is nil (!IsInvoke), a CallCommon represents an ordinary
-	//  function call of the value in Value, which may be a *Builtin, a *Function or any
-	//  other value of kind 'func'.
-	//
-	// 	Value may be one of:
-	// (a) a *Function, indicating a statically dispatched call
-	// to a package-level function, an anonymous function, or
-	// a method of a named type.
-	//
-	// (b) a *MakeClosure, indicating an immediately applied
-	// function literal with free variables.
-	//
-	// (c) a *Builtin, indicating a statically dispatched call
-	// to a built-in function.
-	//
-	// (d) any other value, indicating a dynamically dispatched
-	//     function call.
-	fn, ok := call.Common().Value.(*ssa.Function)
-	if !ok {
-		return
-	}
-	if fn.Object() == nil {
-		return
-	}
-
-	// Check if the function should be called with any locks held.
-	var funcFact lockFunctionFacts
-	pc.pass.ImportObjectFact(fn.Object(), &funcFact)
-	if len(funcFact.GuardedBy) > 0 {
-		for _, fg := range funcFact.GuardedBy {
-			// The first is the method object itself so we skip that when looking
-			// for receiver/function parameters.
-			r := (*call.Value().Operands(nil)[fg.ParameterNumber+1])
-			guardObj := findField(r, fg.FieldNumber)
-			if guardObj == nil {
 				continue
 			}
-			var fieldFacts lockFieldFacts
-			pc.pass.ImportObjectFact(guardObj, &fieldFacts)
-			if fieldFacts.IsMutex || fieldFacts.IsRWMutex {
-				heldMutexes, ok := lh.locks[r]
-				if !ok {
-					log.Debugf("fn: %s, funcFact: %+v", fn, funcFact)
-					pc.maybeFail(call.Pos(), isExempted, "invalid function call %s must be held", guardObj.Name())
-					continue
-				}
-				if _, ok := heldMutexes.lockedMutexes[fg.FieldNumber]; !ok {
-					log.Debugf("fn: %s, funcFact: %+v", fn, funcFact)
-					pc.maybeFail(call.Pos(), isExempted, "invalid function call %s must be held", guardObj.Name())
-				}
-			} else {
-				panic(fmt.Sprintf("function: %+v has an invalid guard that is not a mutex: %+v", fn, guardObj))
-			}
-		}
-	}
-
-	// Check if it's a method dispatch for something in the sync package.
-	// See: https://godoc.org/golang.org/x/tools/go/ssa#Function
-	if fn.Package() != nil && fn.Package().Pkg.Name() == "sync" && fn.Signature.Recv() != nil {
-		r, ok := call.Common().Args[0].(*ssa.FieldAddr)
-		if !ok {
-			return
-		}
-		guardObj := findField(r.X, r.Field)
-		var fieldFacts lockFieldFacts
-		pc.pass.ImportObjectFact(guardObj, &fieldFacts)
-		if fieldFacts.IsMutex || fieldFacts.IsRWMutex {
-			switch fn.Name() {
-			case "Lock", "RLock":
-				obj := r.X
-				m := mutexState{lockedMutexes: make(map[int]struct{})}
-				for k, v := range lh.locks {
-					if isAlias(r.X, k) {
-						obj = k
-						m = v
-					}
-				}
-				if _, ok := m.lockedMutexes[r.Field]; ok {
-					// Double locking a mutex that is already locked.
-					pc.maybeFail(call.Pos(), isExempted, "trying to a lock %s when already locked", guardObj.Name())
-					return
-				}
-				m.lockedMutexes[r.Field] = struct{}{}
-				lh.locks[obj] = m
-			case "Unlock", "RUnlock":
-				// Find the associated locker object.
-				var (
-					obj ssa.Value
-					m   mutexState
-				)
-				for k, v := range lh.locks {
-					if isAlias(r.X, k) {
-						obj = k
-						m = v
-						break
-					}
-				}
-				if _, ok := m.lockedMutexes[r.Field]; !ok {
-					pc.maybeFail(call.Pos(), isExempted, "trying to unlock a mutex %s that is already unlocked", guardObj.Name())
-					return
-				}
-				delete(m.lockedMutexes, r.Field)
-				if len(m.lockedMutexes) == 0 {
-					delete(lh.locks, obj)
-				}
-			case "RLocker", "DowngradeLock", "TryLock", "TryRLock":
-				// we explicitly ignore this for now.
-			default:
-				panic(fmt.Sprintf("unexpected mutex/rwmutex method invoked: %s", fn.Name()))
-			}
+			fn(d)
 		}
 	}
 }
 
+// run is the main entrypoint.
 func run(pass *analysis.Pass) (interface{}, error) {
 	pc := &passContext{
 		pass:       pass,
-		exemptions: make(map[types.Object]struct{}),
 		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.
-	for _, f := range pass.Files {
-		for _, cg := range f.Comments {
-			for _, c := range cg.List {
-				if strings.Contains(c.Text, checkLocksFail) {
-					cnt := 1
-					if strings.Contains(c.Text, checkLocksFail+":") {
-						parts := strings.SplitAfter(c.Text, checkLocksFail+":")
-						parsedCount, err := strconv.Atoi(parts[1])
-						if err != nil {
-							pc.pass.Reportf(c.Pos(), "invalid checklocks annotation : %s", err)
-							continue
-						}
-						cnt = parsedCount
-					}
-					position := toPositionKey(pass.Fset.Position(c.Pos()))
-					pc.failures[position] = &failData{pos: c.Pos(), count: cnt}
-				}
-			}
-		}
-	}
-
-	// Find all struct declarations and export any relevant facts.
-	for _, f := range pass.Files {
-		for _, decl := range f.Decls {
-			d, ok := decl.(*ast.GenDecl)
-			// A GenDecl node (generic declaration node) represents an import,
-			// constant, type or variable declaration.  We only care about struct
-			// declarations so skip any declaration that doesn't declare a new type.
-			if !ok || d.Tok != token.TYPE {
-				continue
-			}
+	pc.extractLineFailures()
 
-			for _, gs := range d.Specs {
-				ts := gs.(*ast.TypeSpec)
-				ss, ok := ts.Type.(*ast.StructType)
-				if !ok {
-					continue
-				}
-				structType := pass.TypesInfo.TypeOf(ts.Name).Underlying().(*types.Struct)
-				pc.findAndExportStructFacts(ss, structType)
-			}
+	// Find all struct declarations and export relevant facts.
+	pc.forAllTypes(func(ts *ast.TypeSpec) {
+		if ss, ok := ts.Type.(*ast.StructType); ok {
+			pc.exportLockFieldFacts(ts, ss)
 		}
-	}
+	})
+	pc.forAllTypes(func(ts *ast.TypeSpec) {
+		if ss, ok := ts.Type.(*ast.StructType); ok {
+			pc.exportLockGuardFacts(ts, ss)
+		}
+	})
 
-	// Find all method calls and export any relevant facts.
-	for _, f := range pass.Files {
-		for _, decl := range f.Decls {
-			d, ok := decl.(*ast.FuncDecl)
-			// Ignore any non function declarations and any functions that do not have
-			// any comments.
-			if !ok || d.Doc == nil {
-				continue
-			}
-			pc.findAndExportFuncFacts(d)
+	// 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)
+	})
 
-	// log all known facts and all failures if debug logging is enabled.
-	allFacts := pass.AllObjectFacts()
-	for i := range allFacts {
-		log.Debugf("fact.object: %+v, fact.Fact: %+v", allFacts[i].Object, allFacts[i].Fact)
-	}
-	log.Debugf("all expected failures: %+v", pc.failures)
+	// Find all function declarations and export relevant facts.
+	pc.forAllFunctions(func(fn *ast.FuncDecl) {
+		pc.exportFunctionFacts(fn)
+	})
 
 	// Scan all code looking for invalid accesses.
 	state := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA)
 	for _, fn := range state.SrcFuncs {
-		var funcFact lockFunctionFacts
-		// Anonymous(closures) functions do not have an object() but do show up in
-		// the SSA.
-		if obj := fn.Object(); obj != nil {
-			pc.pass.ImportObjectFact(fn.Object(), &funcFact)
+		// 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)
 
-		log.Debugf("checking function: %s", fn)
-		var b bytes.Buffer
-		ssa.WriteFunction(&b, fn)
-		log.Debugf("function SSA: %s", b.String())
-		if fn.Recover != nil {
-			pc.checkBasicBlocks([]*ssa.BasicBlock{fn.Recover}, nil, fn, funcFact)
+		// Do we ignore this?
+		if lff.Ignore {
+			continue
 		}
-		pc.checkBasicBlocks(fn.Blocks, fn.Recover, fn, funcFact)
-	}
 
-	// Scan for remaining failures we expect.
-	for _, failure := range pc.failures {
-		// We are missing expect failures, report as much as possible.
-		pass.Reportf(failure.pos, "expected %d failures", failure.count)
+		// 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 expected failures.
+	pc.checkFailures()
 
 	return nil, nil
 }