summaryrefslogtreecommitdiff
path: root/libgo/go/exp/ogle/vars.go
blob: 8a3a14791dbf014967e6aa84519a6a5b5aadf28c (plain)
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
// Copyright 2009 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ogle

import (
	"debug/gosym"
	"debug/proc"
	"exp/eval"
	"log"
	"os"
)

/*
 * Remote frame pointers
 */

// A NotOnStack error occurs when attempting to access a variable in a
// remote frame where that remote frame is not on the current stack.
type NotOnStack struct {
	Fn        *gosym.Func
	Goroutine *Goroutine
}

func (e NotOnStack) String() string {
	return "function " + e.Fn.Name + " not on " + e.Goroutine.String() + "'s stack"
}

// A remoteFramePtr is an implementation of eval.PtrValue that
// represents a pointer to a function frame in a remote process.  When
// accessed, this locates the function on the current goroutine's
// stack and returns a structure containing the local variables of
// that function.
type remoteFramePtr struct {
	p  *Process
	fn *gosym.Func
	rt *remoteType
}

func (v remoteFramePtr) String() string {
	// TODO(austin): This could be a really awesome string method
	return "<remote frame>"
}

func (v remoteFramePtr) Assign(t *eval.Thread, o eval.Value) {
	v.Set(t, o.(eval.PtrValue).Get(t))
}

func (v remoteFramePtr) Get(t *eval.Thread) eval.Value {
	g := v.p.curGoroutine
	if g == nil || g.frame == nil {
		t.Abort(NoCurrentGoroutine{})
	}

	for f := g.frame; f != nil; f = f.aOuter(t) {
		if f.fn != v.fn {
			continue
		}

		// TODO(austin): Register for shootdown with f
		return v.rt.mk(remote{f.fp, v.p})
	}

	t.Abort(NotOnStack{v.fn, g})
	panic("fail")
}

func (v remoteFramePtr) Set(t *eval.Thread, x eval.Value) {
	// Theoretically this could be a static error.  If remote
	// packages were packages, remote frames could just be defined
	// as constants.
	t.Abort(ReadOnlyError("remote frames cannot be assigned to"))
}

/*
 * Remote packages
 */

// TODO(austin): Remote packages are implemented as structs right now,
// which has some weird consequences.  You can attempt to assign to a
// remote package.  It also produces terrible error messages.
// Ideally, these would actually be packages, but somehow first-class
// so they could be assigned to other names.

// A remotePackage is an implementation of eval.StructValue that
// represents a package in a remote process.  It's essentially a
// regular struct, except it cannot be assigned to.
type remotePackage struct {
	defs []eval.Value
}

func (v remotePackage) String() string { return "<remote package>" }

func (v remotePackage) Assign(t *eval.Thread, o eval.Value) {
	t.Abort(ReadOnlyError("remote packages cannot be assigned to"))
}

func (v remotePackage) Get(t *eval.Thread) eval.StructValue {
	return v
}

func (v remotePackage) Field(t *eval.Thread, i int) eval.Value {
	return v.defs[i]
}

/*
 * Remote variables
 */

// populateWorld defines constants in the given world for each package
// in this process.  These packages are structs that, in turn, contain
// fields for each global and function in that package.
func (p *Process) populateWorld(w *eval.World) os.Error {
	type def struct {
		t eval.Type
		v eval.Value
	}
	packages := make(map[string]map[string]def)

	for _, s := range p.syms.Syms {
		if s.ReceiverName() != "" {
			// TODO(austin)
			continue
		}

		// Package
		pkgName := s.PackageName()
		switch pkgName {
		case "", "type", "extratype", "string", "go":
			// "go" is really "go.string"
			continue
		}
		pkg, ok := packages[pkgName]
		if !ok {
			pkg = make(map[string]def)
			packages[pkgName] = pkg
		}

		// Symbol name
		name := s.BaseName()
		if _, ok := pkg[name]; ok {
			log.Printf("Multiple definitions of symbol %s", s.Name)
			continue
		}

		// Symbol type
		rt, err := p.typeOfSym(&s)
		if err != nil {
			return err
		}

		// Definition
		switch s.Type {
		case 'D', 'd', 'B', 'b':
			// Global variable
			if rt == nil {
				continue
			}
			pkg[name] = def{rt.Type, rt.mk(remote{proc.Word(s.Value), p})}

		case 'T', 't', 'L', 'l':
			// Function
			s := s.Func
			// TODO(austin): Ideally, this would *also* be
			// callable.  How does that interact with type
			// conversion syntax?
			rt, err := p.makeFrameType(s)
			if err != nil {
				return err
			}
			pkg[name] = def{eval.NewPtrType(rt.Type), remoteFramePtr{p, s, rt}}
		}
	}

	// TODO(austin): Define remote types

	// Define packages
	for pkgName, defs := range packages {
		fields := make([]eval.StructField, len(defs))
		vals := make([]eval.Value, len(defs))
		i := 0
		for name, def := range defs {
			fields[i].Name = name
			fields[i].Type = def.t
			vals[i] = def.v
			i++
		}
		pkgType := eval.NewStructType(fields)
		pkgVal := remotePackage{vals}

		err := w.DefineConst(pkgName, pkgType, pkgVal)
		if err != nil {
			log.Printf("while defining package %s: %v", pkgName, err)
		}
	}

	return nil
}

// typeOfSym returns the type associated with a symbol.  If the symbol
// has no type, returns nil.
func (p *Process) typeOfSym(s *gosym.Sym) (*remoteType, os.Error) {
	if s.GoType == 0 {
		return nil, nil
	}
	addr := proc.Word(s.GoType)
	var rt *remoteType
	err := try(func(a aborter) { rt = parseRemoteType(a, p.runtime.Type.mk(remote{addr, p}).(remoteStruct)) })
	if err != nil {
		return nil, err
	}
	return rt, nil
}

// makeFrameType constructs a struct type for the frame of a function.
// The offsets in this struct type are such that the struct can be
// instantiated at this function's frame pointer.
func (p *Process) makeFrameType(s *gosym.Func) (*remoteType, os.Error) {
	n := len(s.Params) + len(s.Locals)
	fields := make([]eval.StructField, n)
	layout := make([]remoteStructField, n)
	i := 0

	// TODO(austin): There can be multiple locals/parameters with
	// the same name.  We probably need liveness information to do
	// anything about this.  Once we have that, perhaps we give
	// such fields interface{} type?  Or perhaps we disambiguate
	// the names with numbers.  Disambiguation is annoying for
	// things like "i", where there's an obvious right answer.

	for _, param := range s.Params {
		rt, err := p.typeOfSym(param)
		if err != nil {
			return nil, err
		}
		if rt == nil {
			//fmt.Printf(" (no type)\n");
			continue
		}
		// TODO(austin): Why do local variables carry their
		// package name?
		fields[i].Name = param.BaseName()
		fields[i].Type = rt.Type
		// Parameters have positive offsets from FP
		layout[i].offset = int(param.Value)
		layout[i].fieldType = rt
		i++
	}

	for _, local := range s.Locals {
		rt, err := p.typeOfSym(local)
		if err != nil {
			return nil, err
		}
		if rt == nil {
			continue
		}
		fields[i].Name = local.BaseName()
		fields[i].Type = rt.Type
		// Locals have negative offsets from FP - PtrSize
		layout[i].offset = -int(local.Value) - p.PtrSize()
		layout[i].fieldType = rt
		i++
	}

	fields = fields[0:i]
	layout = layout[0:i]
	t := eval.NewStructType(fields)
	mk := func(r remote) eval.Value { return remoteStruct{r, layout} }
	return &remoteType{t, 0, 0, mk}, nil
}