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 17using namespace llvm; 18using namespace llvm::support::endian; 19using namespace llvm::ELF; 20using namespace lld; 21using namespace lld::elf; 22 23// Undefine the macro predefined by GCC powerpc32. 24#undef PPC 25 26namespace { 27class PPC final : public TargetInfo { 28public: 29 PPC(); 30 RelExpr getRelExpr(RelType type, const Symbol &s, 31 const uint8_t *loc) const override; 32 RelType getDynRel(RelType type) const override; 33 int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override; 34 void writeGotHeader(uint8_t *buf) const override; 35 void writePltHeader(uint8_t *buf) const override { 36 llvm_unreachable("should call writePPC32GlinkSection() instead"); 37 } 38 void writePlt(uint8_t *buf, const Symbol &sym, 39 uint64_t pltEntryAddr) const override { 40 llvm_unreachable("should call writePPC32GlinkSection() instead"); 41 } 42 void writeIplt(uint8_t *buf, const Symbol &sym, 43 uint64_t pltEntryAddr) const override; 44 void writeGotPlt(uint8_t *buf, const Symbol &s) const override; 45 bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file, 46 uint64_t branchAddr, const Symbol &s, 47 int64_t a) const override; 48 uint32_t getThunkSectionSpacing() const override; 49 bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override; 50 void relocate(uint8_t *loc, const Relocation &rel, 51 uint64_t val) const override; 52 RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override; 53 int getTlsGdRelaxSkip(RelType type) const override; 54 void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const override; 55 56private: 57 void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, uint64_t val) const; 58 void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const; 59 void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const; 60 void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const; 61}; 62} // namespace 63 64static uint16_t lo(uint32_t v) { return v; } 65static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; } 66 67static uint32_t readFromHalf16(const uint8_t *loc) { 68 return read32(config->isLE ? loc : loc - 2); 69} 70 71static void writeFromHalf16(uint8_t *loc, uint32_t insn) { 72 write32(config->isLE ? loc : loc - 2, insn); 73} 74 75void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) { 76 // Create canonical PLT entries for non-PIE code. Compilers don't generate 77 // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE. 78 uint32_t glink = in.plt->getVA(); // VA of .glink 79 if (!config->isPic) { 80 for (const Symbol *sym : cast<PPC32GlinkSection>(*in.plt).canonical_plts) { 81 writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0); 82 buf += 16; 83 glink += 16; 84 } 85 } 86 87 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an 88 // absolute address from a specific .plt slot (usually called .got.plt on 89 // other targets) and jumps there. 90 // 91 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load 92 // time. The .glink section is not used. 93 // b) With lazy binding, the .plt entry points to a `b PLTresolve` 94 // instruction in .glink, filled in by PPC::writeGotPlt(). 95 96 // Write N `b PLTresolve` first. 97 for (size_t i = 0; i != numEntries; ++i) 98 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i)); 99 buf += 4 * numEntries; 100 101 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve() 102 // computes the PLT index (by computing the distance from the landing b to 103 // itself) and calls _dl_runtime_resolve() (in glibc). 104 uint32_t got = in.got->getVA(); 105 const uint8_t *end = buf + 64; 106 if (config->isPic) { 107 uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12; 108 uint32_t gotBcl = got + 4 - (glink + afterBcl); 109 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha 110 write32(buf + 4, 0x7c0802a6); // mflr r0 111 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4 112 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l 113 write32(buf + 16, 0x7d8802a6); // mflr r12 114 write32(buf + 20, 0x7c0803a6); // mtlr r0 115 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12 116 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha 117 if (ha(gotBcl) == ha(gotBcl + 4)) { 118 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12) 119 write32(buf + 36, 120 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12) 121 } else { 122 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12) 123 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12) 124 } 125 write32(buf + 40, 0x7c0903a6); // mtctr 0 126 write32(buf + 44, 0x7c0b5a14); // add r0,11,11 127 write32(buf + 48, 0x7d605a14); // add r11,0,11 128 write32(buf + 52, 0x4e800420); // bctr 129 buf += 56; 130 } else { 131 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha 132 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha 133 if (ha(got + 4) == ha(got + 8)) 134 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12) 135 else 136 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12) 137 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l 138 write32(buf + 16, 0x7c0903a6); // mtctr r0 139 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11 140 if (ha(got + 4) == ha(got + 8)) 141 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12) 142 else 143 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12) 144 write32(buf + 28, 0x7d605a14); // add r11,r0,r11 145 write32(buf + 32, 0x4e800420); // bctr 146 buf += 36; 147 } 148 149 // Pad with nop. They should not be executed. 150 for (; buf < end; buf += 4) 151 write32(buf, 0x60000000); 152} 153 154PPC::PPC() { 155 copyRel = R_PPC_COPY; 156 gotRel = R_PPC_GLOB_DAT; 157 pltRel = R_PPC_JMP_SLOT; 158 relativeRel = R_PPC_RELATIVE; 159 iRelativeRel = R_PPC_IRELATIVE; 160 symbolicRel = R_PPC_ADDR32; 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 179void 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 186void 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 193void 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.getPltIdx()); 196} 197 198bool 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 209uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 210 211bool 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 218RelExpr 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_TPREL; 265 default: 266 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 267 ") against symbol " + toString(s)); 268 return R_NONE; 269 } 270} 271 272RelType PPC::getDynRel(RelType type) const { 273 if (type == R_PPC_ADDR32) 274 return type; 275 return R_PPC_NONE; 276} 277 278int64_t PPC::getImplicitAddend(const uint8_t *buf, RelType type) const { 279 switch (type) { 280 case R_PPC_NONE: 281 return 0; 282 case R_PPC_ADDR32: 283 case R_PPC_REL32: 284 return SignExtend64<32>(read32(buf)); 285 default: 286 internalLinkerError(getErrorLocation(buf), 287 "cannot read addend for relocation " + toString(type)); 288 return 0; 289 } 290} 291 292static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 293 uint64_t dtpBiasedVal = val - 0x8000; 294 switch (type) { 295 case R_PPC_DTPREL16: 296 return {R_PPC64_ADDR16, dtpBiasedVal}; 297 case R_PPC_DTPREL16_HA: 298 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 299 case R_PPC_DTPREL16_HI: 300 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 301 case R_PPC_DTPREL16_LO: 302 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 303 case R_PPC_DTPREL32: 304 return {R_PPC_ADDR32, dtpBiasedVal}; 305 default: 306 return {type, val}; 307 } 308} 309 310void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { 311 RelType newType; 312 std::tie(newType, val) = fromDTPREL(rel.type, val); 313 switch (newType) { 314 case R_PPC_ADDR16: 315 checkIntUInt(loc, val, 16, rel); 316 write16(loc, val); 317 break; 318 case R_PPC_GOT16: 319 case R_PPC_GOT_TLSGD16: 320 case R_PPC_GOT_TLSLD16: 321 case R_PPC_GOT_TPREL16: 322 case R_PPC_TPREL16: 323 checkInt(loc, val, 16, rel); 324 write16(loc, val); 325 break; 326 case R_PPC_ADDR16_HA: 327 case R_PPC_DTPREL16_HA: 328 case R_PPC_GOT_TLSGD16_HA: 329 case R_PPC_GOT_TLSLD16_HA: 330 case R_PPC_GOT_TPREL16_HA: 331 case R_PPC_REL16_HA: 332 case R_PPC_TPREL16_HA: 333 write16(loc, ha(val)); 334 break; 335 case R_PPC_ADDR16_HI: 336 case R_PPC_DTPREL16_HI: 337 case R_PPC_GOT_TLSGD16_HI: 338 case R_PPC_GOT_TLSLD16_HI: 339 case R_PPC_GOT_TPREL16_HI: 340 case R_PPC_REL16_HI: 341 case R_PPC_TPREL16_HI: 342 write16(loc, val >> 16); 343 break; 344 case R_PPC_ADDR16_LO: 345 case R_PPC_DTPREL16_LO: 346 case R_PPC_GOT_TLSGD16_LO: 347 case R_PPC_GOT_TLSLD16_LO: 348 case R_PPC_GOT_TPREL16_LO: 349 case R_PPC_REL16_LO: 350 case R_PPC_TPREL16_LO: 351 write16(loc, val); 352 break; 353 case R_PPC_ADDR32: 354 case R_PPC_REL32: 355 write32(loc, val); 356 break; 357 case R_PPC_REL14: { 358 uint32_t mask = 0x0000FFFC; 359 checkInt(loc, val, 16, rel); 360 checkAlignment(loc, val, 4, rel); 361 write32(loc, (read32(loc) & ~mask) | (val & mask)); 362 break; 363 } 364 case R_PPC_ADDR24: 365 case R_PPC_REL24: 366 case R_PPC_LOCAL24PC: 367 case R_PPC_PLTREL24: { 368 uint32_t mask = 0x03FFFFFC; 369 checkInt(loc, val, 26, rel); 370 checkAlignment(loc, val, 4, rel); 371 write32(loc, (read32(loc) & ~mask) | (val & mask)); 372 break; 373 } 374 default: 375 llvm_unreachable("unknown relocation"); 376 } 377} 378 379RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const { 380 if (expr == R_RELAX_TLS_GD_TO_IE) 381 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 382 if (expr == R_RELAX_TLS_LD_TO_LE) 383 return R_RELAX_TLS_LD_TO_LE_ABS; 384 return expr; 385} 386 387int PPC::getTlsGdRelaxSkip(RelType type) const { 388 // A __tls_get_addr call instruction is marked with 2 relocations: 389 // 390 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 391 // R_PPC_REL24: __tls_get_addr 392 // 393 // After the relaxation we no longer call __tls_get_addr and should skip both 394 // relocations to not create a false dependence on __tls_get_addr being 395 // defined. 396 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 397 return 2; 398 return 1; 399} 400 401void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 402 uint64_t val) const { 403 switch (rel.type) { 404 case R_PPC_GOT_TLSGD16: { 405 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 406 uint32_t insn = readFromHalf16(loc); 407 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 408 relocateNoSym(loc, R_PPC_GOT_TPREL16, val); 409 break; 410 } 411 case R_PPC_TLSGD: 412 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 413 write32(loc, 0x7c631214); 414 break; 415 default: 416 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 417 } 418} 419 420void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 421 uint64_t val) const { 422 switch (rel.type) { 423 case R_PPC_GOT_TLSGD16: 424 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 425 writeFromHalf16(loc, 0x3c620000 | ha(val)); 426 break; 427 case R_PPC_TLSGD: 428 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 429 write32(loc, 0x38630000 | lo(val)); 430 break; 431 default: 432 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 433 } 434} 435 436void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 437 uint64_t val) const { 438 switch (rel.type) { 439 case R_PPC_GOT_TLSLD16: 440 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 441 writeFromHalf16(loc, 0x3c620000); 442 break; 443 case R_PPC_TLSLD: 444 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 445 // = r3+x-0x7000, so add 4096 to r3. 446 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 447 write32(loc, 0x38631000); 448 break; 449 case R_PPC_DTPREL16: 450 case R_PPC_DTPREL16_HA: 451 case R_PPC_DTPREL16_HI: 452 case R_PPC_DTPREL16_LO: 453 relocate(loc, rel, val); 454 break; 455 default: 456 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 457 } 458} 459 460void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 461 uint64_t val) const { 462 switch (rel.type) { 463 case R_PPC_GOT_TPREL16: { 464 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 465 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 466 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 467 break; 468 } 469 case R_PPC_TLS: { 470 uint32_t insn = read32(loc); 471 if (insn >> 26 != 31) 472 error("unrecognized instruction for IE to LE R_PPC_TLS"); 473 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 474 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 475 if (dFormOp == 0) 476 error("unrecognized instruction for IE to LE R_PPC_TLS"); 477 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 478 break; 479 } 480 default: 481 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 482 } 483} 484 485void PPC::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const { 486 uint64_t secAddr = sec.getOutputSection()->addr; 487 if (auto *s = dyn_cast<InputSection>(&sec)) 488 secAddr += s->outSecOff; 489 for (const Relocation &rel : sec.relocs()) { 490 uint8_t *loc = buf + rel.offset; 491 const uint64_t val = SignExtend64( 492 sec.getRelocTargetVA(sec.file, rel.type, rel.addend, 493 secAddr + rel.offset, *rel.sym, rel.expr), 494 32); 495 switch (rel.expr) { 496 case R_RELAX_TLS_GD_TO_IE_GOT_OFF: 497 relaxTlsGdToIe(loc, rel, val); 498 break; 499 case R_RELAX_TLS_GD_TO_LE: 500 relaxTlsGdToLe(loc, rel, val); 501 break; 502 case R_RELAX_TLS_LD_TO_LE_ABS: 503 relaxTlsLdToLe(loc, rel, val); 504 break; 505 case R_RELAX_TLS_IE_TO_LE: 506 relaxTlsIeToLe(loc, rel, val); 507 break; 508 default: 509 relocate(loc, rel, val); 510 break; 511 } 512 } 513} 514 515TargetInfo *elf::getPPCTargetInfo() { 516 static PPC target; 517 return ⌖ 518} 519