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; 31 void writePltHeader(uint8_t *buf) const override { 32 llvm_unreachable("should call writePPC32GlinkSection() instead"); 33 } 34 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 adjustRelaxExpr(RelType type, const uint8_t *data, 49 RelExpr expr) const override; 50 int getTlsGdRelaxSkip(RelType type) const override; 51 void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 52 uint64_t val) const override; 53 void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 54 uint64_t val) const override; 55 void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 56 uint64_t val) const override; 57 void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 58 uint64_t val) const override; 59 }; 60 } // namespace 61 62 static uint16_t lo(uint32_t v) { return v; } 63 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; } 64 65 static uint32_t readFromHalf16(const uint8_t *loc) { 66 return read32(config->isLE ? loc : loc - 2); 67 } 68 69 static void writeFromHalf16(uint8_t *loc, uint32_t insn) { 70 write32(config->isLE ? loc : loc - 2, insn); 71 } 72 73 void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) { 74 // Create canonical PLT entries for non-PIE code. Compilers don't generate 75 // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE. 76 uint32_t glink = in.plt->getVA(); // VA of .glink 77 if (!config->isPic) { 78 for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) { 79 writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0); 80 buf += 16; 81 glink += 16; 82 } 83 } 84 85 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an 86 // absolute address from a specific .plt slot (usually called .got.plt on 87 // other targets) and jumps there. 88 // 89 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load 90 // time. The .glink section is not used. 91 // b) With lazy binding, the .plt entry points to a `b PLTresolve` 92 // instruction in .glink, filled in by PPC::writeGotPlt(). 93 94 // Write N `b PLTresolve` first. 95 for (size_t i = 0; i != numEntries; ++i) 96 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i)); 97 buf += 4 * numEntries; 98 99 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve() 100 // computes the PLT index (by computing the distance from the landing b to 101 // itself) and calls _dl_runtime_resolve() (in glibc). 102 uint32_t got = in.got->getVA(); 103 const uint8_t *end = buf + 64; 104 if (config->isPic) { 105 uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12; 106 uint32_t gotBcl = got + 4 - (glink + afterBcl); 107 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha 108 write32(buf + 4, 0x7c0802a6); // mflr r0 109 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4 110 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l 111 write32(buf + 16, 0x7d8802a6); // mflr r12 112 write32(buf + 20, 0x7c0803a6); // mtlr r0 113 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12 114 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha 115 if (ha(gotBcl) == ha(gotBcl + 4)) { 116 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12) 117 write32(buf + 36, 118 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12) 119 } else { 120 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12) 121 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12) 122 } 123 write32(buf + 40, 0x7c0903a6); // mtctr 0 124 write32(buf + 44, 0x7c0b5a14); // add r0,11,11 125 write32(buf + 48, 0x7d605a14); // add r11,0,11 126 write32(buf + 52, 0x4e800420); // bctr 127 buf += 56; 128 } else { 129 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha 130 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha 131 if (ha(got + 4) == ha(got + 8)) 132 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12) 133 else 134 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12) 135 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l 136 write32(buf + 16, 0x7c0903a6); // mtctr r0 137 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11 138 if (ha(got + 4) == ha(got + 8)) 139 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12) 140 else 141 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12) 142 write32(buf + 28, 0x7d605a14); // add r11,r0,r11 143 write32(buf + 32, 0x4e800420); // bctr 144 buf += 36; 145 } 146 147 // Pad with nop. They should not be executed. 148 for (; buf < end; buf += 4) 149 write32(buf, 0x60000000); 150 } 151 152 PPC::PPC() { 153 copyRel = R_PPC_COPY; 154 gotRel = R_PPC_GLOB_DAT; 155 noneRel = R_PPC_NONE; 156 pltRel = R_PPC_JMP_SLOT; 157 relativeRel = R_PPC_RELATIVE; 158 iRelativeRel = R_PPC_IRELATIVE; 159 symbolicRel = R_PPC_ADDR32; 160 gotBaseSymInGotPlt = false; 161 gotHeaderEntriesNum = 3; 162 gotPltHeaderEntriesNum = 0; 163 pltHeaderSize = 0; 164 pltEntrySize = 4; 165 ipltEntrySize = 16; 166 167 needsThunks = true; 168 169 tlsModuleIndexRel = R_PPC_DTPMOD32; 170 tlsOffsetRel = R_PPC_DTPREL32; 171 tlsGotRel = R_PPC_TPREL32; 172 173 defaultMaxPageSize = 65536; 174 defaultImageBase = 0x10000000; 175 176 write32(trapInstr.data(), 0x7fe00008); 177 } 178 179 void PPC::writeIplt(uint8_t *buf, const Symbol &sym, 180 uint64_t /*pltEntryAddr*/) const { 181 // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a 182 // .got2.plt_pic32. thunk. 183 writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000); 184 } 185 186 void PPC::writeGotHeader(uint8_t *buf) const { 187 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC 188 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1], 189 // link_map in _GLOBAL_OFFSET_TABLE_[2]. 190 write32(buf, mainPart->dynamic->getVA()); 191 } 192 193 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const { 194 // Address of the symbol resolver stub in .glink . 195 write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.pltIndex); 196 } 197 198 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file, 199 uint64_t branchAddr, const Symbol &s, int64_t a) const { 200 if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24) 201 return false; 202 if (s.isInPlt()) 203 return true; 204 if (s.isUndefWeak()) 205 return false; 206 return !PPC::inBranchRange(type, branchAddr, s.getVA(a)); 207 } 208 209 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 210 211 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 212 uint64_t offset = dst - src; 213 if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24) 214 return isInt<26>(offset); 215 llvm_unreachable("unsupported relocation type used in branch"); 216 } 217 218 RelExpr PPC::getRelExpr(RelType type, const Symbol &s, 219 const uint8_t *loc) const { 220 switch (type) { 221 case R_PPC_NONE: 222 return R_NONE; 223 case R_PPC_ADDR16_HA: 224 case R_PPC_ADDR16_HI: 225 case R_PPC_ADDR16_LO: 226 case R_PPC_ADDR24: 227 case R_PPC_ADDR32: 228 return R_ABS; 229 case R_PPC_DTPREL16: 230 case R_PPC_DTPREL16_HA: 231 case R_PPC_DTPREL16_HI: 232 case R_PPC_DTPREL16_LO: 233 case R_PPC_DTPREL32: 234 return R_DTPREL; 235 case R_PPC_REL14: 236 case R_PPC_REL32: 237 case R_PPC_REL16_LO: 238 case R_PPC_REL16_HI: 239 case R_PPC_REL16_HA: 240 return R_PC; 241 case R_PPC_GOT16: 242 return R_GOT_OFF; 243 case R_PPC_LOCAL24PC: 244 case R_PPC_REL24: 245 return R_PLT_PC; 246 case R_PPC_PLTREL24: 247 return R_PPC32_PLTREL; 248 case R_PPC_GOT_TLSGD16: 249 return R_TLSGD_GOT; 250 case R_PPC_GOT_TLSLD16: 251 return R_TLSLD_GOT; 252 case R_PPC_GOT_TPREL16: 253 return R_GOT_OFF; 254 case R_PPC_TLS: 255 return R_TLSIE_HINT; 256 case R_PPC_TLSGD: 257 return R_TLSDESC_CALL; 258 case R_PPC_TLSLD: 259 return R_TLSLD_HINT; 260 case R_PPC_TPREL16: 261 case R_PPC_TPREL16_HA: 262 case R_PPC_TPREL16_LO: 263 case R_PPC_TPREL16_HI: 264 return R_TLS; 265 default: 266 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 267 ") against symbol " + toString(s)); 268 return R_NONE; 269 } 270 } 271 272 RelType PPC::getDynRel(RelType type) const { 273 if (type == R_PPC_ADDR32) 274 return type; 275 return R_PPC_NONE; 276 } 277 278 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 279 uint64_t dtpBiasedVal = val - 0x8000; 280 switch (type) { 281 case R_PPC_DTPREL16: 282 return {R_PPC64_ADDR16, dtpBiasedVal}; 283 case R_PPC_DTPREL16_HA: 284 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 285 case R_PPC_DTPREL16_HI: 286 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 287 case R_PPC_DTPREL16_LO: 288 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 289 case R_PPC_DTPREL32: 290 return {R_PPC_ADDR32, dtpBiasedVal}; 291 default: 292 return {type, val}; 293 } 294 } 295 296 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { 297 RelType newType; 298 std::tie(newType, val) = fromDTPREL(rel.type, val); 299 switch (newType) { 300 case R_PPC_ADDR16: 301 checkIntUInt(loc, val, 16, rel); 302 write16(loc, val); 303 break; 304 case R_PPC_GOT16: 305 case R_PPC_GOT_TLSGD16: 306 case R_PPC_GOT_TLSLD16: 307 case R_PPC_GOT_TPREL16: 308 case R_PPC_TPREL16: 309 checkInt(loc, val, 16, rel); 310 write16(loc, val); 311 break; 312 case R_PPC_ADDR16_HA: 313 case R_PPC_DTPREL16_HA: 314 case R_PPC_GOT_TLSGD16_HA: 315 case R_PPC_GOT_TLSLD16_HA: 316 case R_PPC_GOT_TPREL16_HA: 317 case R_PPC_REL16_HA: 318 case R_PPC_TPREL16_HA: 319 write16(loc, ha(val)); 320 break; 321 case R_PPC_ADDR16_HI: 322 case R_PPC_DTPREL16_HI: 323 case R_PPC_GOT_TLSGD16_HI: 324 case R_PPC_GOT_TLSLD16_HI: 325 case R_PPC_GOT_TPREL16_HI: 326 case R_PPC_REL16_HI: 327 case R_PPC_TPREL16_HI: 328 write16(loc, val >> 16); 329 break; 330 case R_PPC_ADDR16_LO: 331 case R_PPC_DTPREL16_LO: 332 case R_PPC_GOT_TLSGD16_LO: 333 case R_PPC_GOT_TLSLD16_LO: 334 case R_PPC_GOT_TPREL16_LO: 335 case R_PPC_REL16_LO: 336 case R_PPC_TPREL16_LO: 337 write16(loc, val); 338 break; 339 case R_PPC_ADDR32: 340 case R_PPC_REL32: 341 write32(loc, val); 342 break; 343 case R_PPC_REL14: { 344 uint32_t mask = 0x0000FFFC; 345 checkInt(loc, val, 16, rel); 346 checkAlignment(loc, val, 4, rel); 347 write32(loc, (read32(loc) & ~mask) | (val & mask)); 348 break; 349 } 350 case R_PPC_REL24: 351 case R_PPC_ADDR24: 352 case R_PPC_LOCAL24PC: 353 case R_PPC_PLTREL24: { 354 uint32_t mask = 0x03FFFFFC; 355 checkInt(loc, val, 26, rel); 356 checkAlignment(loc, val, 4, rel); 357 write32(loc, (read32(loc) & ~mask) | (val & mask)); 358 break; 359 } 360 default: 361 llvm_unreachable("unknown relocation"); 362 } 363 } 364 365 RelExpr PPC::adjustRelaxExpr(RelType type, const uint8_t *data, 366 RelExpr expr) const { 367 if (expr == R_RELAX_TLS_GD_TO_IE) 368 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 369 if (expr == R_RELAX_TLS_LD_TO_LE) 370 return R_RELAX_TLS_LD_TO_LE_ABS; 371 return expr; 372 } 373 374 int PPC::getTlsGdRelaxSkip(RelType type) const { 375 // A __tls_get_addr call instruction is marked with 2 relocations: 376 // 377 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 378 // R_PPC_REL24: __tls_get_addr 379 // 380 // After the relaxation we no longer call __tls_get_addr and should skip both 381 // relocations to not create a false dependence on __tls_get_addr being 382 // defined. 383 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 384 return 2; 385 return 1; 386 } 387 388 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 389 uint64_t val) const { 390 switch (rel.type) { 391 case R_PPC_GOT_TLSGD16: { 392 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 393 uint32_t insn = readFromHalf16(loc); 394 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 395 relocateNoSym(loc, R_PPC_GOT_TPREL16, val); 396 break; 397 } 398 case R_PPC_TLSGD: 399 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 400 write32(loc, 0x7c631214); 401 break; 402 default: 403 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 404 } 405 } 406 407 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 408 uint64_t val) const { 409 switch (rel.type) { 410 case R_PPC_GOT_TLSGD16: 411 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 412 writeFromHalf16(loc, 0x3c620000 | ha(val)); 413 break; 414 case R_PPC_TLSGD: 415 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 416 write32(loc, 0x38630000 | lo(val)); 417 break; 418 default: 419 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 420 } 421 } 422 423 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 424 uint64_t val) const { 425 switch (rel.type) { 426 case R_PPC_GOT_TLSLD16: 427 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 428 writeFromHalf16(loc, 0x3c620000); 429 break; 430 case R_PPC_TLSLD: 431 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 432 // = r3+x-0x7000, so add 4096 to r3. 433 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 434 write32(loc, 0x38631000); 435 break; 436 case R_PPC_DTPREL16: 437 case R_PPC_DTPREL16_HA: 438 case R_PPC_DTPREL16_HI: 439 case R_PPC_DTPREL16_LO: 440 relocate(loc, rel, val); 441 break; 442 default: 443 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 444 } 445 } 446 447 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 448 uint64_t val) const { 449 switch (rel.type) { 450 case R_PPC_GOT_TPREL16: { 451 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 452 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 453 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 454 break; 455 } 456 case R_PPC_TLS: { 457 uint32_t insn = read32(loc); 458 if (insn >> 26 != 31) 459 error("unrecognized instruction for IE to LE R_PPC_TLS"); 460 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 461 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 462 if (dFormOp == 0) 463 error("unrecognized instruction for IE to LE R_PPC_TLS"); 464 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 465 break; 466 } 467 default: 468 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 469 } 470 } 471 472 TargetInfo *elf::getPPCTargetInfo() { 473 static PPC target; 474 return ⌖ 475 } 476