// generate generates offline constraints for the entire program.
func (a *analysis) generate() {
start("Constraint generation")
if a.log != nil {
fmt.Fprintln(a.log, "==== Generating constraints")
}
// Create a dummy node since we use the nodeid 0 for
// non-pointerlike variables.
a.addNodes(tInvalid, "(zero)")
// Create the global node for panic values.
a.panicNode = a.addNodes(tEface, "panic")
// Create nodes and constraints for all methods of reflect.rtype.
// (Shared contours are used by dynamic calls to reflect.Type
// methods---typically just String().)
if rtype := a.reflectRtypePtr; rtype != nil {
a.genMethodsOf(rtype)
}
root := a.genRootCalls()
if a.config.BuildCallGraph {
a.result.CallGraph = callgraph.New(root.fn)
}
// Create nodes and constraints for all methods of all types
// that are dynamically accessible via reflection or interfaces.
for _, T := range a.prog.RuntimeTypes() {
a.genMethodsOf(T)
}
// Generate constraints for functions as they become reachable
// from the roots. (No constraints are generated for functions
// that are dead in this analysis scope.)
for len(a.genq) > 0 {
cgn := a.genq[0]
a.genq = a.genq[1:]
a.genFunc(cgn)
}
// The runtime magically allocates os.Args; so should we.
if os := a.prog.ImportedPackage("os"); os != nil {
// In effect: os.Args = new([1]string)[:]
T := types.NewSlice(types.Typ[types.String])
obj := a.addNodes(sliceToArray(T), "<command-line args>")
a.endObject(obj, nil, "<command-line args>")
a.addressOf(T, a.objectNode(nil, os.Var("Args")), obj)
}
// Discard generation state, to avoid confusion after node renumbering.
a.panicNode = 0
a.globalval = nil
a.localval = nil
a.localobj = nil
stop("Constraint generation")
}
// CallGraph computes the call graph of the specified program
// considering only static calls.
//
func CallGraph(prog *ssa.Program) *callgraph.Graph {
cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
// TODO(adonovan): opt: use only a single pass over the ssa.Program.
for f := range ssautil.AllFunctions(prog) {
fnode := cg.CreateNode(f)
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if site, ok := instr.(ssa.CallInstruction); ok {
if g := site.Common().StaticCallee(); g != nil {
gnode := cg.CreateNode(g)
callgraph.AddEdge(fnode, site, gnode)
}
}
}
}
}
return cg
}
// Analyze performs Rapid Type Analysis, starting at the specified root
// functions. It returns nil if no roots were specified.
//
// If buildCallGraph is true, Result.CallGraph will contain a call
// graph; otherwise, only the other fields (reachable functions) are
// populated.
//
func Analyze(roots []*ssa.Function, buildCallGraph bool) *Result {
if len(roots) == 0 {
return nil
}
r := &rta{
result: &Result{Reachable: make(map[*ssa.Function]struct{ AddrTaken bool })},
prog: roots[0].Prog,
}
if buildCallGraph {
// TODO(adonovan): change callgraph API to eliminate the
// notion of a distinguished root node. Some callgraphs
// have many roots, or none.
r.result.CallGraph = callgraph.New(roots[0])
}
hasher := typeutil.MakeHasher()
r.result.RuntimeTypes.SetHasher(hasher)
r.addrTakenFuncsBySig.SetHasher(hasher)
r.dynCallSites.SetHasher(hasher)
r.invokeSites.SetHasher(hasher)
r.concreteTypes.SetHasher(hasher)
r.interfaceTypes.SetHasher(hasher)
// Visit functions, processing their instructions, and adding
// new functions to the worklist, until a fixed point is
// reached.
var shadow []*ssa.Function // for efficiency, we double-buffer the worklist
r.worklist = append(r.worklist, roots...)
for len(r.worklist) > 0 {
shadow, r.worklist = r.worklist, shadow[:0]
for _, f := range shadow {
r.visitFunc(f)
}
}
return r.result
}
// CallGraph computes the call graph of the specified program using the
// Class Hierarchy Analysis algorithm.
//
func CallGraph(prog *ssa.Program) *callgraph.Graph {
cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
allFuncs := ssautil.AllFunctions(prog)
// funcsBySig contains all functions, keyed by signature. It is
// the effective set of address-taken functions used to resolve
// a dynamic call of a particular signature.
var funcsBySig typeutil.Map // value is []*ssa.Function
// methodsByName contains all methods,
// grouped by name for efficient lookup.
methodsByName := make(map[string][]*ssa.Function)
// methodsMemo records, for every abstract method call call I.f on
// interface type I, the set of concrete methods C.f of all
// types C that satisfy interface I.
methodsMemo := make(map[*types.Func][]*ssa.Function)
lookupMethods := func(m *types.Func) []*ssa.Function {
methods, ok := methodsMemo[m]
if !ok {
I := m.Type().(*types.Signature).Recv().Type().Underlying().(*types.Interface)
for _, f := range methodsByName[m.Name()] {
C := f.Signature.Recv().Type() // named or *named
if types.Implements(C, I) {
methods = append(methods, f)
}
}
methodsMemo[m] = methods
}
return methods
}
for f := range allFuncs {
if f.Signature.Recv() == nil {
// Package initializers can never be address-taken.
if f.Name() == "init" && f.Synthetic == "package initializer" {
continue
}
funcs, _ := funcsBySig.At(f.Signature).([]*ssa.Function)
funcs = append(funcs, f)
funcsBySig.Set(f.Signature, funcs)
} else {
methodsByName[f.Name()] = append(methodsByName[f.Name()], f)
}
}
addEdge := func(fnode *callgraph.Node, site ssa.CallInstruction, g *ssa.Function) {
gnode := cg.CreateNode(g)
callgraph.AddEdge(fnode, site, gnode)
}
addEdges := func(fnode *callgraph.Node, site ssa.CallInstruction, callees []*ssa.Function) {
// Because every call to a highly polymorphic and
// frequently used abstract method such as
// (io.Writer).Write is assumed to call every concrete
// Write method in the program, the call graph can
// contain a lot of duplication.
//
// TODO(adonovan): opt: consider factoring the callgraph
// API so that the Callers component of each edge is a
// slice of nodes, not a singleton.
for _, g := range callees {
addEdge(fnode, site, g)
}
}
for f := range allFuncs {
fnode := cg.CreateNode(f)
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if site, ok := instr.(ssa.CallInstruction); ok {
call := site.Common()
if call.IsInvoke() {
addEdges(fnode, site, lookupMethods(call.Method))
} else if g := call.StaticCallee(); g != nil {
addEdge(fnode, site, g)
} else if _, ok := call.Value.(*ssa.Builtin); !ok {
callees, _ := funcsBySig.At(call.Signature()).([]*ssa.Function)
addEdges(fnode, site, callees)
}
}
}
}
}
return cg
}
// directCallsTo inspects the whole program and returns a callgraph
// containing edges for all direct calls to the target function.
// directCallsTo returns nil if the function is ever address-taken.
func directCallsTo(target *ssa.Function, entrypoints []*ssa.Function) *callgraph.Graph {
cg := callgraph.New(nil) // use nil as root *Function
targetNode := cg.CreateNode(target)
// Is the function a program entry point?
// If so, add edge from callgraph root.
for _, f := range entrypoints {
if f == target {
callgraph.AddEdge(cg.Root, nil, targetNode)
}
}
// Find receiver type (for methods).
var recvType types.Type
if recv := target.Signature.Recv(); recv != nil {
recvType = recv.Type()
}
// Find all direct calls to function,
// or a place where its address is taken.
var space [32]*ssa.Value // preallocate
for fn := range ssautil.AllFunctions(target.Prog) {
for _, b := range fn.Blocks {
for _, instr := range b.Instrs {
// Is this a method (T).f of a concrete type T
// whose runtime type descriptor is address-taken?
// (To be fully sound, we would have to check that
// the type doesn't make it to reflection as a
// subelement of some other address-taken type.)
if recvType != nil {
if mi, ok := instr.(*ssa.MakeInterface); ok {
if types.Identical(mi.X.Type(), recvType) {
return nil // T is address-taken
}
if ptr, ok := mi.X.Type().(*types.Pointer); ok &&
types.Identical(ptr.Elem(), recvType) {
return nil // *T is address-taken
}
}
}
// Direct call to target?
rands := instr.Operands(space[:0])
if site, ok := instr.(ssa.CallInstruction); ok &&
site.Common().Value == target {
callgraph.AddEdge(cg.CreateNode(fn), site, targetNode)
rands = rands[1:] // skip .Value (rands[0])
}
// Address-taken?
for _, rand := range rands {
if rand != nil && *rand == target {
return nil
}
}
}
}
}
return cg
}