Handle cross-package global guards.

Updates #7721

PiperOrigin-RevId: 455029306

tools/checklocks/analysis.go

@@ -322,9 +322,17 @@ func (pc *passContext) checkFieldAccess(inst almostInst, structObj ssa.Value, fi
 	pc.checkGuards(inst, structObj, fieldObj, ls, isWrite)
 }
 
+// noReferrers wraps an instruction as an almostInst.
+type noReferrers struct {
+	ssa.Instruction
+}
+
+// Referrers implements almostInst.Referrers.
+func (noReferrers) Referrers() *[]ssa.Instruction { return nil }
+
 // checkGlobalAccess checks the validity of a global access.
-func (pc *passContext) checkGlobalAccess(g *ssa.Global, ls *lockState, isWrite bool) {
-	pc.checkGuards(g, g, g.Object(), ls, isWrite)
+func (pc *passContext) checkGlobalAccess(inst ssa.Instruction, g *ssa.Global, ls *lockState, isWrite bool) {
+	pc.checkGuards(noReferrers{inst}, g, g.Object(), ls, isWrite)
 }
 
 func (pc *passContext) checkCall(call callCommon, lff *lockFunctionFacts, ls *lockState) {
@@ -592,7 +600,7 @@ func (pc *passContext) checkInstruction(inst ssa.Instruction, lff *lockFunctionF
 			continue
 		}
 		_, isWrite := inst.(*ssa.Store)
-		pc.checkGlobalAccess(g, ls, isWrite)
+		pc.checkGlobalAccess(inst, g, ls, isWrite)
 	}
 
 	// Process the instruction.

tools/checklocks/facts.go

@@ -167,6 +167,9 @@ type globalGuard struct {
 	// ObjectName indicates the object from which resolution should occur.
 	ObjectName string
 
+	// PackageName is the package where the object lives.
+	PackageName string
+
 	// FieldList is the traversal path from object.
 	FieldList fieldList
 }
@@ -179,7 +182,11 @@ type ssaPackager interface {
 // resolveCommon implements resolution for all cases.
 func (g *globalGuard) resolveCommon(pc *passContext, ls *lockState) resolvedValue {
 	state := pc.pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA)
-	v := state.Pkg.Members[g.ObjectName].(ssa.Value)
+	pkg := state.Pkg
+	if g.PackageName != "" && g.PackageName != state.Pkg.Pkg.Path() {
+		pkg = state.Pkg.Prog.ImportedPackage(g.PackageName)
+	}
+	v := pkg.Members[g.ObjectName].(ssa.Value)
 	return makeResolvedValue(v, g.FieldList)
 }
 
@@ -627,8 +634,9 @@ func (pc *passContext) findGlobalGuard(pos token.Pos, guardName string) (*global
 		return nil, false
 	}
 	return &globalGuard{
-		ObjectName: parts[0],
-		FieldList:  fl,
+		ObjectName:  parts[0],
+		PackageName: pc.pass.Pkg.Path(),
+		FieldList:   fl,
 	}, true
 }
 

tools/checklocks/test/BUILD

@@ -27,4 +27,5 @@ go_library(
     # control expected failures for analysis.
     marshal = False,
     stateify = False,
+    deps = ["//tools/checklocks/test/crosspkg"],
 )

tools/checklocks/test/crosspkg/BUILD

@@ -0,0 +1,12 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "crosspkg",
+    srcs = ["crosspkg.go"],
+    # See next level up.
+    marshal = False,
+    stateify = False,
+    visibility = ["//tools/checklocks/test:__pkg__"],
+)

tools/checklocks/test/crosspkg/crosspkg.go

@@ -0,0 +1,26 @@
+// Copyright 2022 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 crosspkg is a second package for testing.
+package crosspkg
+
+import (
+	"sync"
+)
+
+var (
+	// +checklocks:FooMu
+	Foo   int
+	FooMu sync.Mutex
+)

tools/checklocks/test/globals.go

@@ -16,6 +16,8 @@ package test
 
 import (
 	"sync"
+
+	"gvisor.dev/gvisor/tools/checklocks/test/crosspkg"
 )
 
 var (
@@ -83,3 +85,13 @@ func testGlobalInvalid() {
 	otherStruct.guardedField2 = 1 // +checklocksfail
 	otherStruct.guardedField3 = 1 // +checklocksfail
 }
+
+func testCrosspkgGlobalValid() {
+	crosspkg.FooMu.Lock()
+	crosspkg.Foo = 1
+	crosspkg.FooMu.Unlock()
+}
+
+func testCrosspkgGlobalInvalid() {
+	crosspkg.Foo = 1 // +checklocksfail
+}