1// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package loader
6
7import (
8	"cmd/internal/goobj"
9	"cmd/internal/objabi"
10	"cmd/internal/sys"
11	"cmd/link/internal/sym"
12	"sort"
13)
14
15// SymbolBuilder is a helper designed to help with the construction
16// of new symbol contents.
17type SymbolBuilder struct {
18	*extSymPayload         // points to payload being updated
19	symIdx         Sym     // index of symbol being updated/constructed
20	l              *Loader // loader
21}
22
23// MakeSymbolBuilder creates a symbol builder for use in constructing
24// an entirely new symbol.
25func (l *Loader) MakeSymbolBuilder(name string) *SymbolBuilder {
26	// for now assume that any new sym is intended to be static
27	symIdx := l.CreateStaticSym(name)
28	sb := &SymbolBuilder{l: l, symIdx: symIdx}
29	sb.extSymPayload = l.getPayload(symIdx)
30	return sb
31}
32
33// MakeSymbolUpdater creates a symbol builder helper for an existing
34// symbol 'symIdx'. If 'symIdx' is not an external symbol, then create
35// a clone of it (copy name, properties, etc) fix things up so that
36// the lookup tables and caches point to the new version, not the old
37// version.
38func (l *Loader) MakeSymbolUpdater(symIdx Sym) *SymbolBuilder {
39	if symIdx == 0 {
40		panic("can't update the null symbol")
41	}
42	if !l.IsExternal(symIdx) {
43		// Create a clone with the same name/version/kind etc.
44		l.cloneToExternal(symIdx)
45	}
46
47	// Construct updater and return.
48	sb := &SymbolBuilder{l: l, symIdx: symIdx}
49	sb.extSymPayload = l.getPayload(symIdx)
50	return sb
51}
52
53// CreateSymForUpdate creates a symbol with given name and version,
54// returns a CreateSymForUpdate for update. If the symbol already
55// exists, it will update in-place.
56func (l *Loader) CreateSymForUpdate(name string, version int) *SymbolBuilder {
57	s := l.LookupOrCreateSym(name, version)
58	l.SetAttrReachable(s, true)
59	return l.MakeSymbolUpdater(s)
60}
61
62// Getters for properties of the symbol we're working on.
63
64func (sb *SymbolBuilder) Sym() Sym               { return sb.symIdx }
65func (sb *SymbolBuilder) Name() string           { return sb.name }
66func (sb *SymbolBuilder) Version() int           { return sb.ver }
67func (sb *SymbolBuilder) Type() sym.SymKind      { return sb.kind }
68func (sb *SymbolBuilder) Size() int64            { return sb.size }
69func (sb *SymbolBuilder) Data() []byte           { return sb.data }
70func (sb *SymbolBuilder) Value() int64           { return sb.l.SymValue(sb.symIdx) }
71func (sb *SymbolBuilder) Align() int32           { return sb.l.SymAlign(sb.symIdx) }
72func (sb *SymbolBuilder) Localentry() uint8      { return sb.l.SymLocalentry(sb.symIdx) }
73func (sb *SymbolBuilder) OnList() bool           { return sb.l.AttrOnList(sb.symIdx) }
74func (sb *SymbolBuilder) External() bool         { return sb.l.AttrExternal(sb.symIdx) }
75func (sb *SymbolBuilder) Extname() string        { return sb.l.SymExtname(sb.symIdx) }
76func (sb *SymbolBuilder) CgoExportDynamic() bool { return sb.l.AttrCgoExportDynamic(sb.symIdx) }
77func (sb *SymbolBuilder) Dynimplib() string      { return sb.l.SymDynimplib(sb.symIdx) }
78func (sb *SymbolBuilder) Dynimpvers() string     { return sb.l.SymDynimpvers(sb.symIdx) }
79func (sb *SymbolBuilder) SubSym() Sym            { return sb.l.SubSym(sb.symIdx) }
80func (sb *SymbolBuilder) GoType() Sym            { return sb.l.SymGoType(sb.symIdx) }
81func (sb *SymbolBuilder) VisibilityHidden() bool { return sb.l.AttrVisibilityHidden(sb.symIdx) }
82func (sb *SymbolBuilder) Sect() *sym.Section     { return sb.l.SymSect(sb.symIdx) }
83
84// Setters for symbol properties.
85
86func (sb *SymbolBuilder) SetType(kind sym.SymKind)   { sb.kind = kind }
87func (sb *SymbolBuilder) SetSize(size int64)         { sb.size = size }
88func (sb *SymbolBuilder) SetData(data []byte)        { sb.data = data }
89func (sb *SymbolBuilder) SetOnList(v bool)           { sb.l.SetAttrOnList(sb.symIdx, v) }
90func (sb *SymbolBuilder) SetExternal(v bool)         { sb.l.SetAttrExternal(sb.symIdx, v) }
91func (sb *SymbolBuilder) SetValue(v int64)           { sb.l.SetSymValue(sb.symIdx, v) }
92func (sb *SymbolBuilder) SetAlign(align int32)       { sb.l.SetSymAlign(sb.symIdx, align) }
93func (sb *SymbolBuilder) SetLocalentry(value uint8)  { sb.l.SetSymLocalentry(sb.symIdx, value) }
94func (sb *SymbolBuilder) SetExtname(value string)    { sb.l.SetSymExtname(sb.symIdx, value) }
95func (sb *SymbolBuilder) SetDynimplib(value string)  { sb.l.SetSymDynimplib(sb.symIdx, value) }
96func (sb *SymbolBuilder) SetDynimpvers(value string) { sb.l.SetSymDynimpvers(sb.symIdx, value) }
97func (sb *SymbolBuilder) SetPlt(value int32)         { sb.l.SetPlt(sb.symIdx, value) }
98func (sb *SymbolBuilder) SetGot(value int32)         { sb.l.SetGot(sb.symIdx, value) }
99func (sb *SymbolBuilder) SetSpecial(value bool)      { sb.l.SetAttrSpecial(sb.symIdx, value) }
100func (sb *SymbolBuilder) SetLocal(value bool)        { sb.l.SetAttrLocal(sb.symIdx, value) }
101func (sb *SymbolBuilder) SetVisibilityHidden(value bool) {
102	sb.l.SetAttrVisibilityHidden(sb.symIdx, value)
103}
104func (sb *SymbolBuilder) SetNotInSymbolTable(value bool) {
105	sb.l.SetAttrNotInSymbolTable(sb.symIdx, value)
106}
107func (sb *SymbolBuilder) SetSect(sect *sym.Section) { sb.l.SetSymSect(sb.symIdx, sect) }
108
109func (sb *SymbolBuilder) AddBytes(data []byte) {
110	if sb.kind == 0 {
111		sb.kind = sym.SDATA
112	}
113	sb.data = append(sb.data, data...)
114	sb.size = int64(len(sb.data))
115}
116
117func (sb *SymbolBuilder) Relocs() Relocs {
118	return sb.l.Relocs(sb.symIdx)
119}
120
121// ResetRelocs removes all relocations on this symbol.
122func (sb *SymbolBuilder) ResetRelocs() {
123	sb.relocs = sb.relocs[:0]
124}
125
126// SetRelocType sets the type of the 'i'-th relocation on this sym to 't'
127func (sb *SymbolBuilder) SetRelocType(i int, t objabi.RelocType) {
128	sb.relocs[i].SetType(uint16(t))
129}
130
131// SetRelocSym sets the target sym of the 'i'-th relocation on this sym to 's'
132func (sb *SymbolBuilder) SetRelocSym(i int, tgt Sym) {
133	sb.relocs[i].SetSym(goobj.SymRef{PkgIdx: 0, SymIdx: uint32(tgt)})
134}
135
136// SetRelocAdd sets the addend of the 'i'-th relocation on this sym to 'a'
137func (sb *SymbolBuilder) SetRelocAdd(i int, a int64) {
138	sb.relocs[i].SetAdd(a)
139}
140
141// Add n relocations, return a handle to the relocations.
142func (sb *SymbolBuilder) AddRelocs(n int) Relocs {
143	sb.relocs = append(sb.relocs, make([]goobj.Reloc, n)...)
144	return sb.l.Relocs(sb.symIdx)
145}
146
147// Add a relocation with given type, return its handle and index
148// (to set other fields).
149func (sb *SymbolBuilder) AddRel(typ objabi.RelocType) (Reloc, int) {
150	j := len(sb.relocs)
151	sb.relocs = append(sb.relocs, goobj.Reloc{})
152	sb.relocs[j].SetType(uint16(typ))
153	relocs := sb.Relocs()
154	return relocs.At(j), j
155}
156
157// Sort relocations by offset.
158func (sb *SymbolBuilder) SortRelocs() {
159	sort.Sort((*relocsByOff)(sb.extSymPayload))
160}
161
162// Implement sort.Interface
163type relocsByOff extSymPayload
164
165func (p *relocsByOff) Len() int           { return len(p.relocs) }
166func (p *relocsByOff) Less(i, j int) bool { return p.relocs[i].Off() < p.relocs[j].Off() }
167func (p *relocsByOff) Swap(i, j int) {
168	p.relocs[i], p.relocs[j] = p.relocs[j], p.relocs[i]
169}
170
171func (sb *SymbolBuilder) Reachable() bool {
172	return sb.l.AttrReachable(sb.symIdx)
173}
174
175func (sb *SymbolBuilder) SetReachable(v bool) {
176	sb.l.SetAttrReachable(sb.symIdx, v)
177}
178
179func (sb *SymbolBuilder) ReadOnly() bool {
180	return sb.l.AttrReadOnly(sb.symIdx)
181}
182
183func (sb *SymbolBuilder) SetReadOnly(v bool) {
184	sb.l.SetAttrReadOnly(sb.symIdx, v)
185}
186
187func (sb *SymbolBuilder) DuplicateOK() bool {
188	return sb.l.AttrDuplicateOK(sb.symIdx)
189}
190
191func (sb *SymbolBuilder) SetDuplicateOK(v bool) {
192	sb.l.SetAttrDuplicateOK(sb.symIdx, v)
193}
194
195func (sb *SymbolBuilder) Outer() Sym {
196	return sb.l.OuterSym(sb.symIdx)
197}
198
199func (sb *SymbolBuilder) Sub() Sym {
200	return sb.l.SubSym(sb.symIdx)
201}
202
203func (sb *SymbolBuilder) SortSub() {
204	sb.l.SortSub(sb.symIdx)
205}
206
207func (sb *SymbolBuilder) AddInteriorSym(sub Sym) {
208	sb.l.AddInteriorSym(sb.symIdx, sub)
209}
210
211func (sb *SymbolBuilder) AddUint8(v uint8) int64 {
212	off := sb.size
213	if sb.kind == 0 {
214		sb.kind = sym.SDATA
215	}
216	sb.size++
217	sb.data = append(sb.data, v)
218	return off
219}
220
221func (sb *SymbolBuilder) AddUintXX(arch *sys.Arch, v uint64, wid int) int64 {
222	off := sb.size
223	sb.setUintXX(arch, off, v, int64(wid))
224	return off
225}
226
227func (sb *SymbolBuilder) setUintXX(arch *sys.Arch, off int64, v uint64, wid int64) int64 {
228	if sb.kind == 0 {
229		sb.kind = sym.SDATA
230	}
231	if sb.size < off+wid {
232		sb.size = off + wid
233		sb.Grow(sb.size)
234	}
235
236	switch wid {
237	case 1:
238		sb.data[off] = uint8(v)
239	case 2:
240		arch.ByteOrder.PutUint16(sb.data[off:], uint16(v))
241	case 4:
242		arch.ByteOrder.PutUint32(sb.data[off:], uint32(v))
243	case 8:
244		arch.ByteOrder.PutUint64(sb.data[off:], v)
245	}
246
247	return off + wid
248}
249
250func (sb *SymbolBuilder) AddUint16(arch *sys.Arch, v uint16) int64 {
251	return sb.AddUintXX(arch, uint64(v), 2)
252}
253
254func (sb *SymbolBuilder) AddUint32(arch *sys.Arch, v uint32) int64 {
255	return sb.AddUintXX(arch, uint64(v), 4)
256}
257
258func (sb *SymbolBuilder) AddUint64(arch *sys.Arch, v uint64) int64 {
259	return sb.AddUintXX(arch, v, 8)
260}
261
262func (sb *SymbolBuilder) AddUint(arch *sys.Arch, v uint64) int64 {
263	return sb.AddUintXX(arch, v, arch.PtrSize)
264}
265
266func (sb *SymbolBuilder) SetUint8(arch *sys.Arch, r int64, v uint8) int64 {
267	return sb.setUintXX(arch, r, uint64(v), 1)
268}
269
270func (sb *SymbolBuilder) SetUint16(arch *sys.Arch, r int64, v uint16) int64 {
271	return sb.setUintXX(arch, r, uint64(v), 2)
272}
273
274func (sb *SymbolBuilder) SetUint32(arch *sys.Arch, r int64, v uint32) int64 {
275	return sb.setUintXX(arch, r, uint64(v), 4)
276}
277
278func (sb *SymbolBuilder) SetUint(arch *sys.Arch, r int64, v uint64) int64 {
279	return sb.setUintXX(arch, r, v, int64(arch.PtrSize))
280}
281
282func (sb *SymbolBuilder) SetUintptr(arch *sys.Arch, r int64, v uintptr) int64 {
283	return sb.setUintXX(arch, r, uint64(v), int64(arch.PtrSize))
284}
285
286func (sb *SymbolBuilder) SetAddrPlus(arch *sys.Arch, off int64, tgt Sym, add int64) int64 {
287	if sb.Type() == 0 {
288		sb.SetType(sym.SDATA)
289	}
290	if off+int64(arch.PtrSize) > sb.size {
291		sb.size = off + int64(arch.PtrSize)
292		sb.Grow(sb.size)
293	}
294	r, _ := sb.AddRel(objabi.R_ADDR)
295	r.SetSym(tgt)
296	r.SetOff(int32(off))
297	r.SetSiz(uint8(arch.PtrSize))
298	r.SetAdd(add)
299	return off + int64(r.Siz())
300}
301
302func (sb *SymbolBuilder) SetAddr(arch *sys.Arch, off int64, tgt Sym) int64 {
303	return sb.SetAddrPlus(arch, off, tgt, 0)
304}
305
306func (sb *SymbolBuilder) AddStringAt(off int64, str string) int64 {
307	strLen := int64(len(str))
308	if off+strLen > int64(len(sb.data)) {
309		panic("attempt to write past end of buffer")
310	}
311	copy(sb.data[off:off+strLen], str)
312	return off + strLen
313}
314
315// AddCStringAt adds str plus a null terminating byte.
316func (sb *SymbolBuilder) AddCStringAt(off int64, str string) int64 {
317	strLen := int64(len(str))
318	if off+strLen+1 > int64(len(sb.data)) {
319		panic("attempt to write past end of buffer")
320	}
321	copy(sb.data[off:off+strLen], str)
322	sb.data[off+strLen] = 0
323	return off + strLen + 1
324}
325
326func (sb *SymbolBuilder) Addstring(str string) int64 {
327	if sb.kind == 0 {
328		sb.kind = sym.SNOPTRDATA
329	}
330	r := sb.size
331	sb.data = append(sb.data, str...)
332	sb.data = append(sb.data, 0)
333	sb.size = int64(len(sb.data))
334	return r
335}
336
337func (sb *SymbolBuilder) SetBytesAt(off int64, b []byte) int64 {
338	datLen := int64(len(b))
339	if off+datLen > int64(len(sb.data)) {
340		panic("attempt to write past end of buffer")
341	}
342	copy(sb.data[off:off+datLen], b)
343	return off + datLen
344}
345
346func (sb *SymbolBuilder) addSymRef(tgt Sym, add int64, typ objabi.RelocType, rsize int) int64 {
347	if sb.kind == 0 {
348		sb.kind = sym.SDATA
349	}
350	i := sb.size
351
352	sb.size += int64(rsize)
353	sb.Grow(sb.size)
354
355	r, _ := sb.AddRel(typ)
356	r.SetSym(tgt)
357	r.SetOff(int32(i))
358	r.SetSiz(uint8(rsize))
359	r.SetAdd(add)
360
361	return i + int64(rsize)
362}
363
364// Add a symbol reference (relocation) with given type, addend, and size
365// (the most generic form).
366func (sb *SymbolBuilder) AddSymRef(arch *sys.Arch, tgt Sym, add int64, typ objabi.RelocType, rsize int) int64 {
367	return sb.addSymRef(tgt, add, typ, rsize)
368}
369
370func (sb *SymbolBuilder) AddAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
371	return sb.addSymRef(tgt, add, objabi.R_ADDR, arch.PtrSize)
372}
373
374func (sb *SymbolBuilder) AddAddrPlus4(arch *sys.Arch, tgt Sym, add int64) int64 {
375	return sb.addSymRef(tgt, add, objabi.R_ADDR, 4)
376}
377
378func (sb *SymbolBuilder) AddAddr(arch *sys.Arch, tgt Sym) int64 {
379	return sb.AddAddrPlus(arch, tgt, 0)
380}
381
382func (sb *SymbolBuilder) AddPEImageRelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
383	return sb.addSymRef(tgt, add, objabi.R_PEIMAGEOFF, 4)
384}
385
386func (sb *SymbolBuilder) AddPCRelPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
387	return sb.addSymRef(tgt, add, objabi.R_PCREL, 4)
388}
389
390func (sb *SymbolBuilder) AddCURelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
391	return sb.addSymRef(tgt, add, objabi.R_ADDRCUOFF, arch.PtrSize)
392}
393
394func (sb *SymbolBuilder) AddSize(arch *sys.Arch, tgt Sym) int64 {
395	return sb.addSymRef(tgt, 0, objabi.R_SIZE, arch.PtrSize)
396}
397
398// GenAddAddrPlusFunc returns a function to be called when capturing
399// a function symbol's address. In later stages of the link (when
400// address assignment is done) when doing internal linking and
401// targeting an executable, we can just emit the address of a function
402// directly instead of generating a relocation. Clients can call
403// this function (setting 'internalExec' based on build mode and target)
404// and then invoke the returned function in roughly the same way that
405// loader.*SymbolBuilder.AddAddrPlus would be used.
406func GenAddAddrPlusFunc(internalExec bool) func(s *SymbolBuilder, arch *sys.Arch, tgt Sym, add int64) int64 {
407	if internalExec {
408		return func(s *SymbolBuilder, arch *sys.Arch, tgt Sym, add int64) int64 {
409			if v := s.l.SymValue(tgt); v != 0 {
410				return s.AddUint(arch, uint64(v+add))
411			}
412			return s.AddAddrPlus(arch, tgt, add)
413		}
414	} else {
415		return (*SymbolBuilder).AddAddrPlus
416	}
417}
418
419func (sb *SymbolBuilder) MakeWritable() {
420	if sb.ReadOnly() {
421		sb.data = append([]byte(nil), sb.data...)
422		sb.l.SetAttrReadOnly(sb.symIdx, false)
423	}
424}
425
426func (sb *SymbolBuilder) AddUleb(v uint64) {
427	if v < 128 { // common case: 1 byte
428		sb.AddUint8(uint8(v))
429		return
430	}
431	for {
432		c := uint8(v & 0x7f)
433		v >>= 7
434		if v != 0 {
435			c |= 0x80
436		}
437		sb.AddUint8(c)
438		if c&0x80 == 0 {
439			break
440		}
441	}
442}
443