1// Inferno utils/5l/asm.c
2// https://bitbucket.org/inferno-os/inferno-os/src/master/utils/5l/asm.c
3//
4//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
5//	Portions Copyright © 1995-1997 C H Forsyth ([email protected])
6//	Portions Copyright © 1997-1999 Vita Nuova Limited
7//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
8//	Portions Copyright © 2004,2006 Bruce Ellis
9//	Portions Copyright © 2005-2007 C H Forsyth ([email protected])
10//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
11//	Portions Copyright © 2009 The Go Authors. All rights reserved.
12//
13// Permission is hereby granted, free of charge, to any person obtaining a copy
14// of this software and associated documentation files (the "Software"), to deal
15// in the Software without restriction, including without limitation the rights
16// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17// copies of the Software, and to permit persons to whom the Software is
18// furnished to do so, subject to the following conditions:
19//
20// The above copyright notice and this permission notice shall be included in
21// all copies or substantial portions of the Software.
22//
23// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
26// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
29// THE SOFTWARE.
30
31package mips64
32
33import (
34	"cmd/internal/objabi"
35	"cmd/internal/sys"
36	"cmd/link/internal/ld"
37	"cmd/link/internal/loader"
38	"cmd/link/internal/sym"
39	"debug/elf"
40)
41
42var (
43	// dtOffsets contains offsets for entries within the .dynamic section.
44	// These are used to fix up symbol values once they are known.
45	dtOffsets map[elf.DynTag]int64
46
47	// dynSymCount contains the number of entries in the .dynsym section.
48	// This is used to populate the DT_MIPS_SYMTABNO entry in the .dynamic
49	// section.
50	dynSymCount uint64
51
52	// gotLocalCount contains the number of local global offset table
53	// entries. This is used to populate the DT_MIPS_LOCAL_GOTNO entry in
54	// the .dynamic section.
55	gotLocalCount uint64
56
57	// gotSymIndex contains the index of the first dynamic symbol table
58	// entry that corresponds to an entry in the global offset table.
59	// This is used to populate the DT_MIPS_GOTSYM entry in the .dynamic
60	// section.
61	gotSymIndex uint64
62)
63
64func gentext(ctxt *ld.Link, ldr *loader.Loader) {
65	if *ld.FlagD || ctxt.Target.IsExternal() {
66		return
67	}
68
69	dynamic := ldr.MakeSymbolUpdater(ctxt.ArchSyms.Dynamic)
70
71	ld.Elfwritedynent(ctxt.Arch, dynamic, elf.DT_MIPS_RLD_VERSION, 1)
72	ld.Elfwritedynent(ctxt.Arch, dynamic, elf.DT_MIPS_BASE_ADDRESS, 0)
73
74	// elfsetupplt should have been called and gotLocalCount should now
75	// have its correct value.
76	if gotLocalCount == 0 {
77		ctxt.Errorf(0, "internal error: elfsetupplt has not been called")
78	}
79	ld.Elfwritedynent(ctxt.Arch, dynamic, elf.DT_MIPS_LOCAL_GOTNO, gotLocalCount)
80
81	// DT_* entries have to exist prior to elfdynhash(), which finalises the
82	// table by adding DT_NULL. However, the values for the following entries
83	// are not know until after dynreloc() has completed. Add the symbols now,
84	// then update their values prior to code generation.
85	dts := []elf.DynTag{
86		elf.DT_MIPS_SYMTABNO,
87		elf.DT_MIPS_GOTSYM,
88	}
89	dtOffsets = make(map[elf.DynTag]int64)
90	for _, dt := range dts {
91		ld.Elfwritedynent(ctxt.Arch, dynamic, dt, 0)
92		dtOffsets[dt] = dynamic.Size() - 8
93	}
94}
95
96func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r loader.Reloc, rIdx int) bool {
97	targ := r.Sym()
98	var targType sym.SymKind
99	if targ != 0 {
100		targType = ldr.SymType(targ)
101	}
102
103	if r.Type() >= objabi.ElfRelocOffset {
104		ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
105		return false
106	}
107
108	switch r.Type() {
109	case objabi.R_CALLMIPS, objabi.R_JMPMIPS:
110		if targType != sym.SDYNIMPORT {
111			// Nothing to do, the relocation will be laid out in reloc
112			return true
113		}
114		if target.IsExternal() {
115			// External linker will do this relocation.
116			return true
117		}
118
119		// Internal linking, build a PLT entry and change the relocation
120		// target to that entry.
121		if r.Add() != 0 {
122			ldr.Errorf(s, "PLT call with non-zero addend (%v)", r.Add())
123		}
124		addpltsym(target, ldr, syms, targ)
125		su := ldr.MakeSymbolUpdater(s)
126		su.SetRelocSym(rIdx, syms.PLT)
127		su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
128		return true
129	}
130
131	return false
132}
133
134func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, ri int, sectoff int64) bool {
135
136	// mips64 ELF relocation (endian neutral)
137	//		offset	uint64
138	//		sym		uint32
139	//		ssym	uint8
140	//		type3	uint8
141	//		type2	uint8
142	//		type	uint8
143	//		addend	int64
144
145	addend := r.Xadd
146
147	out.Write64(uint64(sectoff))
148
149	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
150	out.Write32(uint32(elfsym))
151	out.Write8(0)
152	out.Write8(0)
153	out.Write8(0)
154	switch r.Type {
155	default:
156		return false
157	case objabi.R_ADDR, objabi.R_DWARFSECREF:
158		switch r.Size {
159		case 4:
160			out.Write8(uint8(elf.R_MIPS_32))
161		case 8:
162			out.Write8(uint8(elf.R_MIPS_64))
163		default:
164			return false
165		}
166	case objabi.R_ADDRMIPS:
167		out.Write8(uint8(elf.R_MIPS_LO16))
168	case objabi.R_ADDRMIPSU:
169		out.Write8(uint8(elf.R_MIPS_HI16))
170	case objabi.R_ADDRMIPSTLS:
171		out.Write8(uint8(elf.R_MIPS_TLS_TPREL_LO16))
172		if ctxt.Target.IsOpenbsd() {
173			// OpenBSD mips64 does not currently offset TLS by 0x7000,
174			// as such we need to add this back to get the correct offset
175			// via the external linker.
176			addend += 0x7000
177		}
178	case objabi.R_CALLMIPS,
179		objabi.R_JMPMIPS:
180		out.Write8(uint8(elf.R_MIPS_26))
181	}
182	out.Write64(uint64(addend))
183
184	return true
185}
186
187func elfsetupplt(ctxt *ld.Link, ldr *loader.Loader, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym) {
188	if plt.Size() != 0 {
189		return
190	}
191
192	// Load resolver address from got[0] into r25.
193	plt.AddSymRef(ctxt.Arch, gotplt.Sym(), 0, objabi.R_ADDRMIPSU, 4)
194	plt.SetUint32(ctxt.Arch, plt.Size()-4, 0x3c0e0000) // lui   $14, %hi(&GOTPLT[0])
195	plt.AddSymRef(ctxt.Arch, gotplt.Sym(), 0, objabi.R_ADDRMIPS, 4)
196	plt.SetUint32(ctxt.Arch, plt.Size()-4, 0xddd90000) // ld    $25, %lo(&GOTPLT[0])($14)
197
198	// Load return address into r15, the index of the got.plt entry into r24, then
199	// JALR to the resolver. The address of the got.plt entry is currently in r24,
200	// which we have to turn into an index.
201	plt.AddSymRef(ctxt.Arch, gotplt.Sym(), 0, objabi.R_ADDRMIPS, 4)
202	plt.SetUint32(ctxt.Arch, plt.Size()-4, 0x25ce0000) // addiu $14, $14, %lo(&GOTPLT[0])
203	plt.AddUint32(ctxt.Arch, 0x030ec023)               // subu  $24, $24, $14
204	plt.AddUint32(ctxt.Arch, 0x03e07825)               // move  $15, $31
205	plt.AddUint32(ctxt.Arch, 0x0018c0c2)               // srl   $24, $24, 3
206	plt.AddUint32(ctxt.Arch, 0x0320f809)               // jalr  $25
207	plt.AddUint32(ctxt.Arch, 0x2718fffe)               // subu  $24, $24, 2
208
209	if gotplt.Size() != 0 {
210		ctxt.Errorf(gotplt.Sym(), "got.plt is not empty")
211	}
212
213	// Reserve got[0] for resolver address (populated by dynamic loader).
214	gotplt.AddUint32(ctxt.Arch, 0)
215	gotplt.AddUint32(ctxt.Arch, 0)
216	gotLocalCount++
217
218	// Reserve got[1] for ELF object pointer (populated by dynamic loader).
219	gotplt.AddUint32(ctxt.Arch, 0)
220	gotplt.AddUint32(ctxt.Arch, 0)
221	gotLocalCount++
222}
223
224func addpltsym(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
225	if ldr.SymPlt(s) >= 0 {
226		return
227	}
228
229	dynamic := ldr.MakeSymbolUpdater(syms.Dynamic)
230
231	const dynSymEntrySize = 20
232	if gotSymIndex == 0 {
233		// Compute and update GOT symbol index.
234		gotSymIndex = uint64(ldr.SymSize(syms.DynSym) / dynSymEntrySize)
235		dynamic.SetUint(target.Arch, dtOffsets[elf.DT_MIPS_GOTSYM], gotSymIndex)
236	}
237	if dynSymCount == 0 {
238		dynSymCount = uint64(ldr.SymSize(syms.DynSym) / dynSymEntrySize)
239	}
240
241	ld.Adddynsym(ldr, target, syms, s)
242	dynSymCount++
243
244	if !target.IsElf() {
245		ldr.Errorf(s, "addpltsym: unsupported binary format")
246	}
247
248	plt := ldr.MakeSymbolUpdater(syms.PLT)
249	gotplt := ldr.MakeSymbolUpdater(syms.GOTPLT)
250	if plt.Size() == 0 {
251		panic("plt is not set up")
252	}
253
254	// Load got.plt entry into r25.
255	plt.AddSymRef(target.Arch, gotplt.Sym(), gotplt.Size(), objabi.R_ADDRMIPSU, 4)
256	plt.SetUint32(target.Arch, plt.Size()-4, 0x3c0f0000) // lui   $15, %hi(.got.plt entry)
257	plt.AddSymRef(target.Arch, gotplt.Sym(), gotplt.Size(), objabi.R_ADDRMIPS, 4)
258	plt.SetUint32(target.Arch, plt.Size()-4, 0xddf90000) // ld    $25, %lo(.got.plt entry)($15)
259
260	// Load address of got.plt entry into r24 and JALR to address in r25.
261	plt.AddUint32(target.Arch, 0x03200008) // jr  $25
262	plt.AddSymRef(target.Arch, gotplt.Sym(), gotplt.Size(), objabi.R_ADDRMIPS, 4)
263	plt.SetUint32(target.Arch, plt.Size()-4, 0x65f80000) // daddiu $24, $15, %lo(.got.plt entry)
264
265	// Add pointer to plt[0] to got.plt
266	gotplt.AddAddrPlus(target.Arch, plt.Sym(), 0)
267
268	ldr.SetPlt(s, int32(plt.Size()-16))
269
270	// Update dynamic symbol count.
271	dynamic.SetUint(target.Arch, dtOffsets[elf.DT_MIPS_SYMTABNO], dynSymCount)
272}
273
274func machoreloc1(*sys.Arch, *ld.OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool {
275	return false
276}
277
278func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loader.Reloc, s loader.Sym, val int64) (o int64, nExtReloc int, ok bool) {
279	if target.IsExternal() {
280		switch r.Type() {
281		default:
282			return val, 0, false
283
284		case objabi.R_ADDRMIPS,
285			objabi.R_ADDRMIPSU,
286			objabi.R_ADDRMIPSTLS,
287			objabi.R_CALLMIPS,
288			objabi.R_JMPMIPS:
289			return val, 1, true
290		}
291	}
292
293	const isOk = true
294	const noExtReloc = 0
295	rs := r.Sym()
296	switch r.Type() {
297	case objabi.R_ADDRMIPS,
298		objabi.R_ADDRMIPSU:
299		t := ldr.SymValue(rs) + r.Add()
300		if r.Type() == objabi.R_ADDRMIPS {
301			return int64(val&0xffff0000 | t&0xffff), noExtReloc, isOk
302		}
303		return int64(val&0xffff0000 | ((t+1<<15)>>16)&0xffff), noExtReloc, isOk
304	case objabi.R_ADDRMIPSTLS:
305		// thread pointer is at 0x7000 offset from the start of TLS data area
306		t := ldr.SymValue(rs) + r.Add() - 0x7000
307		if target.IsOpenbsd() {
308			// OpenBSD mips64 does not currently offset TLS by 0x7000,
309			// as such we need to add this back to get the correct offset.
310			t += 0x7000
311		}
312		if t < -32768 || t >= 32678 {
313			ldr.Errorf(s, "TLS offset out of range %d", t)
314		}
315		return int64(val&0xffff0000 | t&0xffff), noExtReloc, isOk
316	case objabi.R_CALLMIPS,
317		objabi.R_JMPMIPS:
318		// Low 26 bits = (S + A) >> 2
319		t := ldr.SymValue(rs) + r.Add()
320		return int64(val&0xfc000000 | (t>>2)&^0xfc000000), noExtReloc, isOk
321	}
322
323	return val, 0, false
324}
325
326func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc, sym.RelocVariant, loader.Sym, int64, []byte) int64 {
327	return -1
328}
329
330func extreloc(target *ld.Target, ldr *loader.Loader, r loader.Reloc, s loader.Sym) (loader.ExtReloc, bool) {
331	switch r.Type() {
332	case objabi.R_ADDRMIPS,
333		objabi.R_ADDRMIPSU:
334		return ld.ExtrelocViaOuterSym(ldr, r, s), true
335
336	case objabi.R_ADDRMIPSTLS,
337		objabi.R_CALLMIPS,
338		objabi.R_JMPMIPS:
339		return ld.ExtrelocSimple(ldr, r), true
340	}
341	return loader.ExtReloc{}, false
342}
343