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 int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override; 31 void writeGotHeader(uint8_t *buf) const override; 32 void writePltHeader(uint8_t *buf) const override { 33 llvm_unreachable("should call writePPC32GlinkSection() instead"); 34 } 35 void writePlt(uint8_t *buf, const Symbol &sym, 36 uint64_t pltEntryAddr) const override { 37 llvm_unreachable("should call writePPC32GlinkSection() instead"); 38 } 39 void writeIplt(uint8_t *buf, const Symbol &sym, 40 uint64_t pltEntryAddr) const override; 41 void writeGotPlt(uint8_t *buf, const Symbol &s) const override; 42 bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file, 43 uint64_t branchAddr, const Symbol &s, 44 int64_t a) const override; 45 uint32_t getThunkSectionSpacing() const override; 46 bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override; 47 void relocate(uint8_t *loc, const Relocation &rel, 48 uint64_t val) const override; 49 RelExpr adjustTlsExpr(RelType type, 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 pltRel = R_PPC_JMP_SLOT; 156 relativeRel = R_PPC_RELATIVE; 157 iRelativeRel = R_PPC_IRELATIVE; 158 symbolicRel = R_PPC_ADDR32; 159 gotHeaderEntriesNum = 3; 160 gotPltHeaderEntriesNum = 0; 161 pltHeaderSize = 0; 162 pltEntrySize = 4; 163 ipltEntrySize = 16; 164 165 needsThunks = true; 166 167 tlsModuleIndexRel = R_PPC_DTPMOD32; 168 tlsOffsetRel = R_PPC_DTPREL32; 169 tlsGotRel = R_PPC_TPREL32; 170 171 defaultMaxPageSize = 65536; 172 defaultImageBase = 0x10000000; 173 174 write32(trapInstr.data(), 0x7fe00008); 175 } 176 177 void PPC::writeIplt(uint8_t *buf, const Symbol &sym, 178 uint64_t /*pltEntryAddr*/) const { 179 // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a 180 // .got2.plt_pic32. thunk. 181 writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000); 182 } 183 184 void PPC::writeGotHeader(uint8_t *buf) const { 185 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC 186 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1], 187 // link_map in _GLOBAL_OFFSET_TABLE_[2]. 188 write32(buf, mainPart->dynamic->getVA()); 189 } 190 191 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const { 192 // Address of the symbol resolver stub in .glink . 193 write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.pltIndex); 194 } 195 196 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file, 197 uint64_t branchAddr, const Symbol &s, int64_t a) const { 198 if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24) 199 return false; 200 if (s.isInPlt()) 201 return true; 202 if (s.isUndefWeak()) 203 return false; 204 return !PPC::inBranchRange(type, branchAddr, s.getVA(a)); 205 } 206 207 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 208 209 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 210 uint64_t offset = dst - src; 211 if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24) 212 return isInt<26>(offset); 213 llvm_unreachable("unsupported relocation type used in branch"); 214 } 215 216 RelExpr PPC::getRelExpr(RelType type, const Symbol &s, 217 const uint8_t *loc) const { 218 switch (type) { 219 case R_PPC_NONE: 220 return R_NONE; 221 case R_PPC_ADDR16_HA: 222 case R_PPC_ADDR16_HI: 223 case R_PPC_ADDR16_LO: 224 case R_PPC_ADDR24: 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_TPREL; 263 default: 264 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 265 ") against symbol " + toString(s)); 266 return R_NONE; 267 } 268 } 269 270 RelType PPC::getDynRel(RelType type) const { 271 if (type == R_PPC_ADDR32) 272 return type; 273 return R_PPC_NONE; 274 } 275 276 int64_t PPC::getImplicitAddend(const uint8_t *buf, RelType type) const { 277 switch (type) { 278 case R_PPC_NONE: 279 return 0; 280 case R_PPC_ADDR32: 281 case R_PPC_REL32: 282 return SignExtend64<32>(read32(buf)); 283 default: 284 internalLinkerError(getErrorLocation(buf), 285 "cannot read addend for relocation " + toString(type)); 286 return 0; 287 } 288 } 289 290 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 291 uint64_t dtpBiasedVal = val - 0x8000; 292 switch (type) { 293 case R_PPC_DTPREL16: 294 return {R_PPC64_ADDR16, dtpBiasedVal}; 295 case R_PPC_DTPREL16_HA: 296 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 297 case R_PPC_DTPREL16_HI: 298 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 299 case R_PPC_DTPREL16_LO: 300 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 301 case R_PPC_DTPREL32: 302 return {R_PPC_ADDR32, dtpBiasedVal}; 303 default: 304 return {type, val}; 305 } 306 } 307 308 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { 309 RelType newType; 310 std::tie(newType, val) = fromDTPREL(rel.type, val); 311 switch (newType) { 312 case R_PPC_ADDR16: 313 checkIntUInt(loc, val, 16, rel); 314 write16(loc, val); 315 break; 316 case R_PPC_GOT16: 317 case R_PPC_GOT_TLSGD16: 318 case R_PPC_GOT_TLSLD16: 319 case R_PPC_GOT_TPREL16: 320 case R_PPC_TPREL16: 321 checkInt(loc, val, 16, rel); 322 write16(loc, val); 323 break; 324 case R_PPC_ADDR16_HA: 325 case R_PPC_DTPREL16_HA: 326 case R_PPC_GOT_TLSGD16_HA: 327 case R_PPC_GOT_TLSLD16_HA: 328 case R_PPC_GOT_TPREL16_HA: 329 case R_PPC_REL16_HA: 330 case R_PPC_TPREL16_HA: 331 write16(loc, ha(val)); 332 break; 333 case R_PPC_ADDR16_HI: 334 case R_PPC_DTPREL16_HI: 335 case R_PPC_GOT_TLSGD16_HI: 336 case R_PPC_GOT_TLSLD16_HI: 337 case R_PPC_GOT_TPREL16_HI: 338 case R_PPC_REL16_HI: 339 case R_PPC_TPREL16_HI: 340 write16(loc, val >> 16); 341 break; 342 case R_PPC_ADDR16_LO: 343 case R_PPC_DTPREL16_LO: 344 case R_PPC_GOT_TLSGD16_LO: 345 case R_PPC_GOT_TLSLD16_LO: 346 case R_PPC_GOT_TPREL16_LO: 347 case R_PPC_REL16_LO: 348 case R_PPC_TPREL16_LO: 349 write16(loc, val); 350 break; 351 case R_PPC_ADDR32: 352 case R_PPC_REL32: 353 write32(loc, val); 354 break; 355 case R_PPC_REL14: { 356 uint32_t mask = 0x0000FFFC; 357 checkInt(loc, val, 16, rel); 358 checkAlignment(loc, val, 4, rel); 359 write32(loc, (read32(loc) & ~mask) | (val & mask)); 360 break; 361 } 362 case R_PPC_ADDR24: 363 case R_PPC_REL24: 364 case R_PPC_LOCAL24PC: 365 case R_PPC_PLTREL24: { 366 uint32_t mask = 0x03FFFFFC; 367 checkInt(loc, val, 26, rel); 368 checkAlignment(loc, val, 4, rel); 369 write32(loc, (read32(loc) & ~mask) | (val & mask)); 370 break; 371 } 372 default: 373 llvm_unreachable("unknown relocation"); 374 } 375 } 376 377 RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const { 378 if (expr == R_RELAX_TLS_GD_TO_IE) 379 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 380 if (expr == R_RELAX_TLS_LD_TO_LE) 381 return R_RELAX_TLS_LD_TO_LE_ABS; 382 return expr; 383 } 384 385 int PPC::getTlsGdRelaxSkip(RelType type) const { 386 // A __tls_get_addr call instruction is marked with 2 relocations: 387 // 388 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 389 // R_PPC_REL24: __tls_get_addr 390 // 391 // After the relaxation we no longer call __tls_get_addr and should skip both 392 // relocations to not create a false dependence on __tls_get_addr being 393 // defined. 394 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 395 return 2; 396 return 1; 397 } 398 399 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 400 uint64_t val) const { 401 switch (rel.type) { 402 case R_PPC_GOT_TLSGD16: { 403 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 404 uint32_t insn = readFromHalf16(loc); 405 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 406 relocateNoSym(loc, R_PPC_GOT_TPREL16, val); 407 break; 408 } 409 case R_PPC_TLSGD: 410 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 411 write32(loc, 0x7c631214); 412 break; 413 default: 414 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 415 } 416 } 417 418 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 419 uint64_t val) const { 420 switch (rel.type) { 421 case R_PPC_GOT_TLSGD16: 422 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 423 writeFromHalf16(loc, 0x3c620000 | ha(val)); 424 break; 425 case R_PPC_TLSGD: 426 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 427 write32(loc, 0x38630000 | lo(val)); 428 break; 429 default: 430 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 431 } 432 } 433 434 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 435 uint64_t val) const { 436 switch (rel.type) { 437 case R_PPC_GOT_TLSLD16: 438 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 439 writeFromHalf16(loc, 0x3c620000); 440 break; 441 case R_PPC_TLSLD: 442 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 443 // = r3+x-0x7000, so add 4096 to r3. 444 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 445 write32(loc, 0x38631000); 446 break; 447 case R_PPC_DTPREL16: 448 case R_PPC_DTPREL16_HA: 449 case R_PPC_DTPREL16_HI: 450 case R_PPC_DTPREL16_LO: 451 relocate(loc, rel, val); 452 break; 453 default: 454 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 455 } 456 } 457 458 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 459 uint64_t val) const { 460 switch (rel.type) { 461 case R_PPC_GOT_TPREL16: { 462 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 463 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 464 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 465 break; 466 } 467 case R_PPC_TLS: { 468 uint32_t insn = read32(loc); 469 if (insn >> 26 != 31) 470 error("unrecognized instruction for IE to LE R_PPC_TLS"); 471 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 472 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 473 if (dFormOp == 0) 474 error("unrecognized instruction for IE to LE R_PPC_TLS"); 475 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 476 break; 477 } 478 default: 479 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 480 } 481 } 482 483 TargetInfo *elf::getPPCTargetInfo() { 484 static PPC target; 485 return ⌖ 486 } 487