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Copy pathexits.go
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356 lines (335 loc) · 9.85 KB
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package ir
import (
"go/types"
)
func (b *builder) buildExits(fn *Function) {
if obj := fn.Object(); obj != nil {
switch obj.Pkg().Path() {
case "runtime":
switch obj.Name() {
case "exit":
fn.NoReturn = AlwaysExits
return
case "throw":
fn.NoReturn = AlwaysExits
return
case "Goexit":
fn.NoReturn = AlwaysUnwinds
return
}
case "go.uber.org/zap":
switch obj.(*types.Func).FullName() {
case "(*go.uber.org/zap.Logger).Fatal",
"(*go.uber.org/zap.SugaredLogger).Fatal",
"(*go.uber.org/zap.SugaredLogger).Fatalw",
"(*go.uber.org/zap.SugaredLogger).Fatalf":
// Technically, this method does not unconditionally exit
// the process. It dynamically calls a function stored in
// the logger. If the function is nil, it defaults to
// os.Exit.
//
// The main intent of this method is to terminate the
// process, and that's what the vast majority of people
// will use it for. We'll happily accept some false
// negatives to avoid a lot of false positives.
fn.NoReturn = AlwaysExits
case "(*go.uber.org/zap.Logger).Panic",
"(*go.uber.org/zap.SugaredLogger).Panicw",
"(*go.uber.org/zap.SugaredLogger).Panicf":
fn.NoReturn = AlwaysUnwinds
return
case "(*go.uber.org/zap.Logger).DPanic",
"(*go.uber.org/zap.SugaredLogger).DPanicf",
"(*go.uber.org/zap.SugaredLogger).DPanicw":
// These methods will only panic in development.
}
case "github.com/sirupsen/logrus":
switch obj.(*types.Func).FullName() {
case "(*github.com/sirupsen/logrus.Logger).Exit":
// Technically, this method does not unconditionally exit
// the process. It dynamically calls a function stored in
// the logger. If the function is nil, it defaults to
// os.Exit.
//
// The main intent of this method is to terminate the
// process, and that's what the vast majority of people
// will use it for. We'll happily accept some false
// negatives to avoid a lot of false positives.
fn.NoReturn = AlwaysExits
return
case "(*github.com/sirupsen/logrus.Logger).Panic",
"(*github.com/sirupsen/logrus.Logger).Panicf",
"(*github.com/sirupsen/logrus.Logger).Panicln":
// Th
8000
ese methods will always panic, but that's not
// statically known from the code alone, because they
// take a detour through the generic Log methods.
fn.NoReturn = AlwaysUnwinds
return
case "(*github.com/sirupsen/logrus.Entry).Panicf",
"(*github.com/sirupsen/logrus.Entry).Panicln":
// Entry.Panic has an explicit panic, but Panicf and
// Panicln do not, relying fully on the generic Log
// method.
fn.NoReturn = AlwaysUnwinds
return
case "(*github.com/sirupsen/logrus.Logger).Log",
"(*github.com/sirupsen/logrus.Logger).Logf",
"(*github.com/sirupsen/logrus.Logger).Logln":
// TODO(dh): we cannot handle these cases. Whether they
// exit or unwind depends on the level, which is set
// via the first argument. We don't currently support
// call-site-specific exit information.
}
case "github.com/golang/glog":
switch obj.(*types.Func).FullName() {
case "github.com/golang/glog.Exit",
"github.com/golang/glog.ExitDepth",
"github.com/golang/glog.Exitf",
"github.com/golang/glog.Exitln",
"github.com/golang/glog.Fatal",
"github.com/golang/glog.FatalDepth",
"github.com/golang/glog.Fatalf",
"github.com/golang/glog.Fatalln":
// all of these call os.Exit after logging
fn.NoReturn = AlwaysExits
}
case "k8s.io/klog":
switch obj.(*types.Func).FullName() {
case "k8s.io/klog.Exit",
"k8s.io/klog.ExitDepth",
"k8s.io/klog.Exitf",
"k8s.io/klog.Exitln",
"k8s.io/klog.Fatal",
"k8s.io/klog.FatalDepth",
"k8s.io/klog.Fatalf",
"k8s.io/klog.Fatalln":
// all of these call os.Exit after logging
fn.NoReturn = AlwaysExits
}
}
}
isRecoverCall := func(instr Instruction) bool {
if instr, ok := instr.(*Call); ok {
if builtin, ok := instr.Call.Value.(*Builtin); ok {
if builtin.Name() == "recover" {
return true
}
}
}
return false
}
both := NewBlockSet(len(fn.Blocks))
exits := NewBlockSet(len(fn.Blocks))
unwinds := NewBlockSet(len(fn.Blocks))
recovers := false
for _, u := range fn.Blocks {
for _, instr := range u.Instrs {
instrSwitch:
switch instr := instr.(type) {
case *Defer:
if recovers {
// avoid doing extra work, we already know that this function calls recover
continue
}
call := instr.Call.StaticCallee()
if call == nil {
// not a static call, so we can't be sure the
// deferred call isn't calling recover
recovers = true
break
}
if call.Package() == fn.Package() {
b.buildFunction(call)
}
if len(call.Blocks) == 0 {
// external function, we don't know what's
// happening inside it
//
// TODO(dh): this includes functions from
// imported packages, due to how go/analysis
// works. We could introduce another fact,
// like we've done for exiting and unwinding.
recovers = true
break
}
for _, y := range call.Blocks {
for _, instr2 := range y.Instrs {
if isRecoverCall(instr2) {
recovers = true
break instrSwitch
}
}
}
case *Panic:
both.Add(u)
unwinds.Add(u)
case CallInstruction:
switch instr.(type) {
case *Defer, *Call:
default:
continue
}
if instr.Common().IsInvoke() {
// give up
return
}
var call *Function
switch instr.Common().Value.(type) {
case *Function, *MakeClosure:
call = instr.Common().StaticCallee()
case *Builtin:
// the only builtins that affect control flow are
// panic and recover, and we've already handled
// those
continue
default:
// dynamic dispatch
return
}
// buildFunction is idempotent. if we're part of a
// (mutually) recursive call chain, then buildFunction
// will immediately return, and fn.WillExit will be false.
if call.Package() == fn.Package() {
b.buildFunction(call)
}
switch call.NoReturn {
case AlwaysExits:
both.Add(u)
exits.Add(u)
case AlwaysUnwinds:
both.Add(u)
unwinds.Add(u)
case NeverReturns:
both.Add(u)
}
}
}
}
// depth-first search trying to find a path to the exit block that
// doesn't cross any of the blacklisted blocks
seen := NewBlockSet(len(fn.Blocks))
var findPath func(root *BasicBlock, bl *BlockSet) bool
findPath = func(root *BasicBlock, bl *BlockSet) bool {
if root == fn.Exit {
return true
}
if seen.Has(root) {
return false
}
if bl.Has(root) {
return false
}
seen.Add(root)
for _, succ := range root.Succs {
if findPath(succ, bl) {
return true
}
}
return false
}
findPathEntry := func(root *BasicBlock, bl *BlockSet) bool {
if bl.Num() == 0 {
return true
}
seen.Clear()
return findPath(root, bl)
}
if !findPathEntry(fn.Blocks[0], exits) {
fn.NoReturn = AlwaysExits
} else if !recovers {
// Only consider unwinding and "never returns" if we don't
// call recover. If we do call recover, then panics don't
// bubble up the stack.
// TODO(dh): the position of the defer matters. If we
// unconditionally terminate before we defer a recover, then
// the recover is ineffective.
if !findPathEntry(fn.Blocks[0], unwinds) {
fn.NoReturn = AlwaysUnwinds
} else if !findPathEntry(fn.Blocks[0], both) {
fn.NoReturn = NeverReturns
}
}
}
func (b *builder) addUnreachables(fn *Function) {
var unreachable *BasicBlock
for _, bb := range fn.Blocks {
instrLoop:
for i, instr := range bb.Instrs {
if instr, ok := instr.(*Call); ok {
var call *Function
switch v := instr.Common().Value.(type) {
case *Function:
call = v
case *MakeClosure:
call = v.Fn.(*Function)
}
if call == nil {
continue
}
if call.Package() == fn.Package() {
// make sure we have information on all functions in this package
b.buildFunction(call)
}
switch call.NoReturn {
case AlwaysExits:
// This call will cause the process to terminate.
// Remove remaining instructions in the block and
// replace any control flow with Unreachable.
for _, succ := range bb.Succs {
succ.removePred(bb)
}
bb.Succs = bb.Succs[:0]
bb.Instrs = bb.Instrs[:i+1]
bb.emit(new(Unreachable), instr.Source())
addEdge(bb, fn.Exit)
break instrLoop
case AlwaysUnwinds:
// This call will cause the goroutine to terminate
// and defers to run (i.e. a panic or
// runtime.Goexit). Remove remaining instructions
// in the block and replace any control flow with
// an unconditional jump to the exit block.
for _, succ := range bb.Succs {
succ.removePred(bb)
}
bb.Succs = bb.Succs[:0]
bb.Instrs = bb.Instrs[:i+1]
bb.emit(new(Jump), instr.Source())
addEdge(bb, fn.Exit)
break instrLoop
case NeverReturns:
// This call will either cause the goroutine to
// terminate, or the process to terminate. Remove
// remaining instructions in the block and replace
// any control flow with a conditional jump to
// either the exit block, or Unreachable.
for _, succ := range bb.Succs {
succ.removePred(bb)
}
bb.Succs = bb.Succs[:0]
bb.Instrs = bb.Instrs[:i+1]
var c Call
c.Call.Value = &Builtin{
name: "ir:noreturnWasPanic",
sig: types.NewSignature(nil,
types.NewTuple(),
types.NewTuple(anonVar(types.Typ[types.Bool])),
false,
),
}
c.setType(types.Typ[types.Bool])
if unreachable == nil {
unreachable = fn.newBasicBlock("unreachable")
unreachable.emit(&Unreachable{}, nil)
addEdge(unreachable, fn.Exit)
}
bb.emit(&c, instr.Source())
bb.emit(&If{Cond: &c}, instr.Source())
addEdge(bb, fn.Exit)
addEdge(bb, unreachable)
break instrLoop
}
}
}
}
}