1 //===- PPC.cpp ------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "OutputSections.h"
10 #include "Symbols.h"
11 #include "SyntheticSections.h"
12 #include "Target.h"
13 #include "Thunks.h"
14 #include "lld/Common/ErrorHandler.h"
15 #include "llvm/Support/Endian.h"
16
17 using namespace llvm;
18 using namespace llvm::support::endian;
19 using namespace llvm::ELF;
20 using namespace lld;
21 using namespace lld::elf;
22
23 namespace {
24 class PPC final : public TargetInfo {
25 public:
26 PPC();
27 RelExpr getRelExpr(RelType type, const Symbol &s,
28 const uint8_t *loc) const override;
29 RelType getDynRel(RelType type) const override;
30 void writeGotHeader(uint8_t *buf) const override;
writePltHeader(uint8_t * buf) const31 void writePltHeader(uint8_t *buf) const override {
32 llvm_unreachable("should call writePPC32GlinkSection() instead");
33 }
writePlt(uint8_t * buf,const Symbol & sym,uint64_t pltEntryAddr) const34 void writePlt(uint8_t *buf, const Symbol &sym,
35 uint64_t pltEntryAddr) const override {
36 llvm_unreachable("should call writePPC32GlinkSection() instead");
37 }
38 void writeIplt(uint8_t *buf, const Symbol &sym,
39 uint64_t pltEntryAddr) const override;
40 void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
41 bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file,
42 uint64_t branchAddr, const Symbol &s,
43 int64_t a) const override;
44 uint32_t getThunkSectionSpacing() const override;
45 bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
46 void relocate(uint8_t *loc, const Relocation &rel,
47 uint64_t val) const override;
48 RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
49 int getTlsGdRelaxSkip(RelType type) const override;
50 void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
51 uint64_t val) const override;
52 void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
53 uint64_t val) const override;
54 void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
55 uint64_t val) const override;
56 void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
57 uint64_t val) const override;
58 };
59 } // namespace
60
lo(uint32_t v)61 static uint16_t lo(uint32_t v) { return v; }
ha(uint32_t v)62 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; }
63
readFromHalf16(const uint8_t * loc)64 static uint32_t readFromHalf16(const uint8_t *loc) {
65 return read32(config->isLE ? loc : loc - 2);
66 }
67
writeFromHalf16(uint8_t * loc,uint32_t insn)68 static void writeFromHalf16(uint8_t *loc, uint32_t insn) {
69 write32(config->isLE ? loc : loc - 2, insn);
70 }
71
writePPC32GlinkSection(uint8_t * buf,size_t numEntries)72 void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) {
73 // Create canonical PLT entries for non-PIE code. Compilers don't generate
74 // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE.
75 uint32_t glink = in.plt->getVA(); // VA of .glink
76 if (!config->isPic) {
77 for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) {
78 writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
79 buf += 16;
80 glink += 16;
81 }
82 }
83
84 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an
85 // absolute address from a specific .plt slot (usually called .got.plt on
86 // other targets) and jumps there.
87 //
88 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load
89 // time. The .glink section is not used.
90 // b) With lazy binding, the .plt entry points to a `b PLTresolve`
91 // instruction in .glink, filled in by PPC::writeGotPlt().
92
93 // Write N `b PLTresolve` first.
94 for (size_t i = 0; i != numEntries; ++i)
95 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i));
96 buf += 4 * numEntries;
97
98 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve()
99 // computes the PLT index (by computing the distance from the landing b to
100 // itself) and calls _dl_runtime_resolve() (in glibc).
101 uint32_t got = in.got->getVA();
102 const uint8_t *end = buf + 64;
103 if (config->isPic) {
104 uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12;
105 uint32_t gotBcl = got + 4 - (glink + afterBcl);
106 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha
107 write32(buf + 4, 0x7c0802a6); // mflr r0
108 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4
109 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l
110 write32(buf + 16, 0x7d8802a6); // mflr r12
111 write32(buf + 20, 0x7c0803a6); // mtlr r0
112 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12
113 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha
114 if (ha(gotBcl) == ha(gotBcl + 4)) {
115 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12)
116 write32(buf + 36,
117 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12)
118 } else {
119 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12)
120 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12)
121 }
122 write32(buf + 40, 0x7c0903a6); // mtctr 0
123 write32(buf + 44, 0x7c0b5a14); // add r0,11,11
124 write32(buf + 48, 0x7d605a14); // add r11,0,11
125 write32(buf + 52, 0x4e800420); // bctr
126 buf += 56;
127 } else {
128 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha
129 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha
130 if (ha(got + 4) == ha(got + 8))
131 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12)
132 else
133 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12)
134 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l
135 write32(buf + 16, 0x7c0903a6); // mtctr r0
136 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11
137 if (ha(got + 4) == ha(got + 8))
138 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12)
139 else
140 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12)
141 write32(buf + 28, 0x7d605a14); // add r11,r0,r11
142 write32(buf + 32, 0x4e800420); // bctr
143 buf += 36;
144 }
145
146 // Pad with nop. They should not be executed.
147 for (; buf < end; buf += 4)
148 write32(buf, 0x60000000);
149 }
150
PPC()151 PPC::PPC() {
152 copyRel = R_PPC_COPY;
153 gotRel = R_PPC_GLOB_DAT;
154 noneRel = R_PPC_NONE;
155 pltRel = R_PPC_JMP_SLOT;
156 relativeRel = R_PPC_RELATIVE;
157 iRelativeRel = R_PPC_IRELATIVE;
158 symbolicRel = R_PPC_ADDR32;
159 gotBaseSymInGotPlt = false;
160 gotHeaderEntriesNum = 3;
161 gotPltHeaderEntriesNum = 0;
162 pltHeaderSize = 0;
163 pltEntrySize = 4;
164 ipltEntrySize = 16;
165
166 needsThunks = true;
167
168 tlsModuleIndexRel = R_PPC_DTPMOD32;
169 tlsOffsetRel = R_PPC_DTPREL32;
170 tlsGotRel = R_PPC_TPREL32;
171
172 defaultMaxPageSize = 65536;
173 defaultImageBase = 0x10000000;
174
175 write32(trapInstr.data(), 0x7fe00008);
176 }
177
writeIplt(uint8_t * buf,const Symbol & sym,uint64_t) const178 void PPC::writeIplt(uint8_t *buf, const Symbol &sym,
179 uint64_t /*pltEntryAddr*/) const {
180 // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a
181 // .got2.plt_pic32. thunk.
182 writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000);
183 }
184
writeGotHeader(uint8_t * buf) const185 void PPC::writeGotHeader(uint8_t *buf) const {
186 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC
187 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1],
188 // link_map in _GLOBAL_OFFSET_TABLE_[2].
189 write32(buf, mainPart->dynamic->getVA());
190 }
191
writeGotPlt(uint8_t * buf,const Symbol & s) const192 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const {
193 // Address of the symbol resolver stub in .glink .
194 write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.pltIndex);
195 }
196
needsThunk(RelExpr expr,RelType type,const InputFile * file,uint64_t branchAddr,const Symbol & s,int64_t a) const197 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file,
198 uint64_t branchAddr, const Symbol &s, int64_t a) const {
199 if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24)
200 return false;
201 if (s.isInPlt())
202 return true;
203 if (s.isUndefWeak())
204 return false;
205 return !PPC::inBranchRange(type, branchAddr, s.getVA(a));
206 }
207
getThunkSectionSpacing() const208 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; }
209
inBranchRange(RelType type,uint64_t src,uint64_t dst) const210 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
211 uint64_t offset = dst - src;
212 if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24)
213 return isInt<26>(offset);
214 llvm_unreachable("unsupported relocation type used in branch");
215 }
216
getRelExpr(RelType type,const Symbol & s,const uint8_t * loc) const217 RelExpr PPC::getRelExpr(RelType type, const Symbol &s,
218 const uint8_t *loc) const {
219 switch (type) {
220 case R_PPC_NONE:
221 return R_NONE;
222 case R_PPC_ADDR16_HA:
223 case R_PPC_ADDR16_HI:
224 case R_PPC_ADDR16_LO:
225 case R_PPC_ADDR32:
226 return R_ABS;
227 case R_PPC_DTPREL16:
228 case R_PPC_DTPREL16_HA:
229 case R_PPC_DTPREL16_HI:
230 case R_PPC_DTPREL16_LO:
231 case R_PPC_DTPREL32:
232 return R_DTPREL;
233 case R_PPC_REL14:
234 case R_PPC_REL32:
235 case R_PPC_REL16_LO:
236 case R_PPC_REL16_HI:
237 case R_PPC_REL16_HA:
238 return R_PC;
239 case R_PPC_GOT16:
240 return R_GOT_OFF;
241 case R_PPC_LOCAL24PC:
242 case R_PPC_REL24:
243 return R_PLT_PC;
244 case R_PPC_PLTREL24:
245 return R_PPC32_PLTREL;
246 case R_PPC_GOT_TLSGD16:
247 return R_TLSGD_GOT;
248 case R_PPC_GOT_TLSLD16:
249 return R_TLSLD_GOT;
250 case R_PPC_GOT_TPREL16:
251 return R_GOT_OFF;
252 case R_PPC_TLS:
253 return R_TLSIE_HINT;
254 case R_PPC_TLSGD:
255 return R_TLSDESC_CALL;
256 case R_PPC_TLSLD:
257 return R_TLSLD_HINT;
258 case R_PPC_TPREL16:
259 case R_PPC_TPREL16_HA:
260 case R_PPC_TPREL16_LO:
261 case R_PPC_TPREL16_HI:
262 return R_TLS;
263 default:
264 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
265 ") against symbol " + toString(s));
266 return R_NONE;
267 }
268 }
269
getDynRel(RelType type) const270 RelType PPC::getDynRel(RelType type) const {
271 if (type == R_PPC_ADDR32)
272 return type;
273 return R_PPC_NONE;
274 }
275
fromDTPREL(RelType type,uint64_t val)276 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) {
277 uint64_t dtpBiasedVal = val - 0x8000;
278 switch (type) {
279 case R_PPC_DTPREL16:
280 return {R_PPC64_ADDR16, dtpBiasedVal};
281 case R_PPC_DTPREL16_HA:
282 return {R_PPC_ADDR16_HA, dtpBiasedVal};
283 case R_PPC_DTPREL16_HI:
284 return {R_PPC_ADDR16_HI, dtpBiasedVal};
285 case R_PPC_DTPREL16_LO:
286 return {R_PPC_ADDR16_LO, dtpBiasedVal};
287 case R_PPC_DTPREL32:
288 return {R_PPC_ADDR32, dtpBiasedVal};
289 default:
290 return {type, val};
291 }
292 }
293
relocate(uint8_t * loc,const Relocation & rel,uint64_t val) const294 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
295 RelType newType;
296 std::tie(newType, val) = fromDTPREL(rel.type, val);
297 switch (newType) {
298 case R_PPC_ADDR16:
299 checkIntUInt(loc, val, 16, rel);
300 write16(loc, val);
301 break;
302 case R_PPC_GOT16:
303 case R_PPC_GOT_TLSGD16:
304 case R_PPC_GOT_TLSLD16:
305 case R_PPC_GOT_TPREL16:
306 case R_PPC_TPREL16:
307 checkInt(loc, val, 16, rel);
308 write16(loc, val);
309 break;
310 case R_PPC_ADDR16_HA:
311 case R_PPC_DTPREL16_HA:
312 case R_PPC_GOT_TLSGD16_HA:
313 case R_PPC_GOT_TLSLD16_HA:
314 case R_PPC_GOT_TPREL16_HA:
315 case R_PPC_REL16_HA:
316 case R_PPC_TPREL16_HA:
317 write16(loc, ha(val));
318 break;
319 case R_PPC_ADDR16_HI:
320 case R_PPC_DTPREL16_HI:
321 case R_PPC_GOT_TLSGD16_HI:
322 case R_PPC_GOT_TLSLD16_HI:
323 case R_PPC_GOT_TPREL16_HI:
324 case R_PPC_REL16_HI:
325 case R_PPC_TPREL16_HI:
326 write16(loc, val >> 16);
327 break;
328 case R_PPC_ADDR16_LO:
329 case R_PPC_DTPREL16_LO:
330 case R_PPC_GOT_TLSGD16_LO:
331 case R_PPC_GOT_TLSLD16_LO:
332 case R_PPC_GOT_TPREL16_LO:
333 case R_PPC_REL16_LO:
334 case R_PPC_TPREL16_LO:
335 write16(loc, val);
336 break;
337 case R_PPC_ADDR32:
338 case R_PPC_REL32:
339 write32(loc, val);
340 break;
341 case R_PPC_REL14: {
342 uint32_t mask = 0x0000FFFC;
343 checkInt(loc, val, 16, rel);
344 checkAlignment(loc, val, 4, rel);
345 write32(loc, (read32(loc) & ~mask) | (val & mask));
346 break;
347 }
348 case R_PPC_REL24:
349 case R_PPC_LOCAL24PC:
350 case R_PPC_PLTREL24: {
351 uint32_t mask = 0x03FFFFFC;
352 checkInt(loc, val, 26, rel);
353 checkAlignment(loc, val, 4, rel);
354 write32(loc, (read32(loc) & ~mask) | (val & mask));
355 break;
356 }
357 default:
358 llvm_unreachable("unknown relocation");
359 }
360 }
361
adjustTlsExpr(RelType type,RelExpr expr) const362 RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const {
363 if (expr == R_RELAX_TLS_GD_TO_IE)
364 return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
365 if (expr == R_RELAX_TLS_LD_TO_LE)
366 return R_RELAX_TLS_LD_TO_LE_ABS;
367 return expr;
368 }
369
getTlsGdRelaxSkip(RelType type) const370 int PPC::getTlsGdRelaxSkip(RelType type) const {
371 // A __tls_get_addr call instruction is marked with 2 relocations:
372 //
373 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation
374 // R_PPC_REL24: __tls_get_addr
375 //
376 // After the relaxation we no longer call __tls_get_addr and should skip both
377 // relocations to not create a false dependence on __tls_get_addr being
378 // defined.
379 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD)
380 return 2;
381 return 1;
382 }
383
relaxTlsGdToIe(uint8_t * loc,const Relocation & rel,uint64_t val) const384 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
385 uint64_t val) const {
386 switch (rel.type) {
387 case R_PPC_GOT_TLSGD16: {
388 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA)
389 uint32_t insn = readFromHalf16(loc);
390 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000));
391 relocateNoSym(loc, R_PPC_GOT_TPREL16, val);
392 break;
393 }
394 case R_PPC_TLSGD:
395 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2
396 write32(loc, 0x7c631214);
397 break;
398 default:
399 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
400 }
401 }
402
relaxTlsGdToLe(uint8_t * loc,const Relocation & rel,uint64_t val) const403 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
404 uint64_t val) const {
405 switch (rel.type) {
406 case R_PPC_GOT_TLSGD16:
407 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha
408 writeFromHalf16(loc, 0x3c620000 | ha(val));
409 break;
410 case R_PPC_TLSGD:
411 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l
412 write32(loc, 0x38630000 | lo(val));
413 break;
414 default:
415 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
416 }
417 }
418
relaxTlsLdToLe(uint8_t * loc,const Relocation & rel,uint64_t val) const419 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
420 uint64_t val) const {
421 switch (rel.type) {
422 case R_PPC_GOT_TLSLD16:
423 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0
424 writeFromHalf16(loc, 0x3c620000);
425 break;
426 case R_PPC_TLSLD:
427 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel
428 // = r3+x-0x7000, so add 4096 to r3.
429 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096
430 write32(loc, 0x38631000);
431 break;
432 case R_PPC_DTPREL16:
433 case R_PPC_DTPREL16_HA:
434 case R_PPC_DTPREL16_HI:
435 case R_PPC_DTPREL16_LO:
436 relocate(loc, rel, val);
437 break;
438 default:
439 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
440 }
441 }
442
relaxTlsIeToLe(uint8_t * loc,const Relocation & rel,uint64_t val) const443 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
444 uint64_t val) const {
445 switch (rel.type) {
446 case R_PPC_GOT_TPREL16: {
447 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha
448 uint32_t rt = readFromHalf16(loc) & 0x03e00000;
449 writeFromHalf16(loc, 0x3c020000 | rt | ha(val));
450 break;
451 }
452 case R_PPC_TLS: {
453 uint32_t insn = read32(loc);
454 if (insn >> 26 != 31)
455 error("unrecognized instruction for IE to LE R_PPC_TLS");
456 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l
457 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1);
458 if (dFormOp == 0)
459 error("unrecognized instruction for IE to LE R_PPC_TLS");
460 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val));
461 break;
462 }
463 default:
464 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation");
465 }
466 }
467
getPPCTargetInfo()468 TargetInfo *elf::getPPCTargetInfo() {
469 static PPC target;
470 return ⌖
471 }
472