Repository navigation
Expand file tree
/
Copy pathexits.go
More file actions
317 lines (296 loc) · 8.43 KB
/
Copy pathexits.go
File metadata and controls
317 lines (296 loc) · 8.43 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
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 "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":
// These 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
}
}
}
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
}
}
}
}
}