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 // Undefine the macro predefined by GCC powerpc32. 24 #undef PPC 25 26 namespace { 27 class PPC final : public TargetInfo { 28 public: 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 relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 55 uint64_t val) const override; 56 void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 57 uint64_t val) const override; 58 void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 59 uint64_t val) const override; 60 void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 61 uint64_t val) const override; 62 }; 63 } // namespace 64 65 static uint16_t lo(uint32_t v) { return v; } 66 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; } 67 68 static uint32_t readFromHalf16(const uint8_t *loc) { 69 return read32(config->isLE ? loc : loc - 2); 70 } 71 72 static void writeFromHalf16(uint8_t *loc, uint32_t insn) { 73 write32(config->isLE ? loc : loc - 2, insn); 74 } 75 76 void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) { 77 // Create canonical PLT entries for non-PIE code. Compilers don't generate 78 // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE. 79 uint32_t glink = in.plt->getVA(); // VA of .glink 80 if (!config->isPic) { 81 for (const Symbol *sym : cast<PPC32GlinkSection>(*in.plt).canonical_plts) { 82 writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0); 83 buf += 16; 84 glink += 16; 85 } 86 } 87 88 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an 89 // absolute address from a specific .plt slot (usually called .got.plt on 90 // other targets) and jumps there. 91 // 92 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load 93 // time. The .glink section is not used. 94 // b) With lazy binding, the .plt entry points to a `b PLTresolve` 95 // instruction in .glink, filled in by PPC::writeGotPlt(). 96 97 // Write N `b PLTresolve` first. 98 for (size_t i = 0; i != numEntries; ++i) 99 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i)); 100 buf += 4 * numEntries; 101 102 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve() 103 // computes the PLT index (by computing the distance from the landing b to 104 // itself) and calls _dl_runtime_resolve() (in glibc). 105 uint32_t got = in.got->getVA(); 106 const uint8_t *end = buf + 64; 107 if (config->isPic) { 108 uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12; 109 uint32_t gotBcl = got + 4 - (glink + afterBcl); 110 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha 111 write32(buf + 4, 0x7c0802a6); // mflr r0 112 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4 113 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l 114 write32(buf + 16, 0x7d8802a6); // mflr r12 115 write32(buf + 20, 0x7c0803a6); // mtlr r0 116 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12 117 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha 118 if (ha(gotBcl) == ha(gotBcl + 4)) { 119 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12) 120 write32(buf + 36, 121 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12) 122 } else { 123 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12) 124 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12) 125 } 126 write32(buf + 40, 0x7c0903a6); // mtctr 0 127 write32(buf + 44, 0x7c0b5a14); // add r0,11,11 128 write32(buf + 48, 0x7d605a14); // add r11,0,11 129 write32(buf + 52, 0x4e800420); // bctr 130 buf += 56; 131 } else { 132 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha 133 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha 134 if (ha(got + 4) == ha(got + 8)) 135 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12) 136 else 137 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12) 138 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l 139 write32(buf + 16, 0x7c0903a6); // mtctr r0 140 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11 141 if (ha(got + 4) == ha(got + 8)) 142 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12) 143 else 144 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12) 145 write32(buf + 28, 0x7d605a14); // add r11,r0,r11 146 write32(buf + 32, 0x4e800420); // bctr 147 buf += 36; 148 } 149 150 // Pad with nop. They should not be executed. 151 for (; buf < end; buf += 4) 152 write32(buf, 0x60000000); 153 } 154 155 PPC::PPC() { 156 copyRel = R_PPC_COPY; 157 gotRel = R_PPC_GLOB_DAT; 158 pltRel = R_PPC_JMP_SLOT; 159 relativeRel = R_PPC_RELATIVE; 160 iRelativeRel = R_PPC_IRELATIVE; 161 symbolicRel = R_PPC_ADDR32; 162 gotHeaderEntriesNum = 3; 163 gotPltHeaderEntriesNum = 0; 164 pltHeaderSize = 0; 165 pltEntrySize = 4; 166 ipltEntrySize = 16; 167 168 needsThunks = true; 169 170 tlsModuleIndexRel = R_PPC_DTPMOD32; 171 tlsOffsetRel = R_PPC_DTPREL32; 172 tlsGotRel = R_PPC_TPREL32; 173 174 defaultMaxPageSize = 65536; 175 defaultImageBase = 0x10000000; 176 177 write32(trapInstr.data(), 0x7fe00008); 178 } 179 180 void PPC::writeIplt(uint8_t *buf, const Symbol &sym, 181 uint64_t /*pltEntryAddr*/) const { 182 // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a 183 // .got2.plt_pic32. thunk. 184 writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000); 185 } 186 187 void PPC::writeGotHeader(uint8_t *buf) const { 188 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC 189 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1], 190 // link_map in _GLOBAL_OFFSET_TABLE_[2]. 191 write32(buf, mainPart->dynamic->getVA()); 192 } 193 194 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const { 195 // Address of the symbol resolver stub in .glink . 196 write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.getPltIdx()); 197 } 198 199 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file, 200 uint64_t branchAddr, const Symbol &s, int64_t a) const { 201 if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24) 202 return false; 203 if (s.isInPlt()) 204 return true; 205 if (s.isUndefWeak()) 206 return false; 207 return !PPC::inBranchRange(type, branchAddr, s.getVA(a)); 208 } 209 210 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 211 212 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 213 uint64_t offset = dst - src; 214 if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24) 215 return isInt<26>(offset); 216 llvm_unreachable("unsupported relocation type used in branch"); 217 } 218 219 RelExpr PPC::getRelExpr(RelType type, const Symbol &s, 220 const uint8_t *loc) const { 221 switch (type) { 222 case R_PPC_NONE: 223 return R_NONE; 224 case R_PPC_ADDR16_HA: 225 case R_PPC_ADDR16_HI: 226 case R_PPC_ADDR16_LO: 227 case R_PPC_ADDR24: 228 case R_PPC_ADDR32: 229 return R_ABS; 230 case R_PPC_DTPREL16: 231 case R_PPC_DTPREL16_HA: 232 case R_PPC_DTPREL16_HI: 233 case R_PPC_DTPREL16_LO: 234 case R_PPC_DTPREL32: 235 return R_DTPREL; 236 case R_PPC_REL14: 237 case R_PPC_REL32: 238 case R_PPC_REL16_LO: 239 case R_PPC_REL16_HI: 240 case R_PPC_REL16_HA: 241 return R_PC; 242 case R_PPC_GOT16: 243 return R_GOT_OFF; 244 case R_PPC_LOCAL24PC: 245 case R_PPC_REL24: 246 return R_PLT_PC; 247 case R_PPC_PLTREL24: 248 return R_PPC32_PLTREL; 249 case R_PPC_GOT_TLSGD16: 250 return R_TLSGD_GOT; 251 case R_PPC_GOT_TLSLD16: 252 return R_TLSLD_GOT; 253 case R_PPC_GOT_TPREL16: 254 return R_GOT_OFF; 255 case R_PPC_TLS: 256 return R_TLSIE_HINT; 257 case R_PPC_TLSGD: 258 return R_TLSDESC_CALL; 259 case R_PPC_TLSLD: 260 return R_TLSLD_HINT; 261 case R_PPC_TPREL16: 262 case R_PPC_TPREL16_HA: 263 case R_PPC_TPREL16_LO: 264 case R_PPC_TPREL16_HI: 265 return R_TPREL; 266 default: 267 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 268 ") against symbol " + toString(s)); 269 return R_NONE; 270 } 271 } 272 273 RelType PPC::getDynRel(RelType type) const { 274 if (type == R_PPC_ADDR32) 275 return type; 276 return R_PPC_NONE; 277 } 278 279 int64_t PPC::getImplicitAddend(const uint8_t *buf, RelType type) const { 280 switch (type) { 281 case R_PPC_NONE: 282 return 0; 283 case R_PPC_ADDR32: 284 case R_PPC_REL32: 285 return SignExtend64<32>(read32(buf)); 286 default: 287 internalLinkerError(getErrorLocation(buf), 288 "cannot read addend for relocation " + toString(type)); 289 return 0; 290 } 291 } 292 293 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 294 uint64_t dtpBiasedVal = val - 0x8000; 295 switch (type) { 296 case R_PPC_DTPREL16: 297 return {R_PPC64_ADDR16, dtpBiasedVal}; 298 case R_PPC_DTPREL16_HA: 299 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 300 case R_PPC_DTPREL16_HI: 301 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 302 case R_PPC_DTPREL16_LO: 303 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 304 case R_PPC_DTPREL32: 305 return {R_PPC_ADDR32, dtpBiasedVal}; 306 default: 307 return {type, val}; 308 } 309 } 310 311 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { 312 RelType newType; 313 std::tie(newType, val) = fromDTPREL(rel.type, val); 314 switch (newType) { 315 case R_PPC_ADDR16: 316 checkIntUInt(loc, val, 16, rel); 317 write16(loc, val); 318 break; 319 case R_PPC_GOT16: 320 case R_PPC_GOT_TLSGD16: 321 case R_PPC_GOT_TLSLD16: 322 case R_PPC_GOT_TPREL16: 323 case R_PPC_TPREL16: 324 checkInt(loc, val, 16, rel); 325 write16(loc, val); 326 break; 327 case R_PPC_ADDR16_HA: 328 case R_PPC_DTPREL16_HA: 329 case R_PPC_GOT_TLSGD16_HA: 330 case R_PPC_GOT_TLSLD16_HA: 331 case R_PPC_GOT_TPREL16_HA: 332 case R_PPC_REL16_HA: 333 case R_PPC_TPREL16_HA: 334 write16(loc, ha(val)); 335 break; 336 case R_PPC_ADDR16_HI: 337 case R_PPC_DTPREL16_HI: 338 case R_PPC_GOT_TLSGD16_HI: 339 case R_PPC_GOT_TLSLD16_HI: 340 case R_PPC_GOT_TPREL16_HI: 341 case R_PPC_REL16_HI: 342 case R_PPC_TPREL16_HI: 343 write16(loc, val >> 16); 344 break; 345 case R_PPC_ADDR16_LO: 346 case R_PPC_DTPREL16_LO: 347 case R_PPC_GOT_TLSGD16_LO: 348 case R_PPC_GOT_TLSLD16_LO: 349 case R_PPC_GOT_TPREL16_LO: 350 case R_PPC_REL16_LO: 351 case R_PPC_TPREL16_LO: 352 write16(loc, val); 353 break; 354 case R_PPC_ADDR32: 355 case R_PPC_REL32: 356 write32(loc, val); 357 break; 358 case R_PPC_REL14: { 359 uint32_t mask = 0x0000FFFC; 360 checkInt(loc, val, 16, rel); 361 checkAlignment(loc, val, 4, rel); 362 write32(loc, (read32(loc) & ~mask) | (val & mask)); 363 break; 364 } 365 case R_PPC_ADDR24: 366 case R_PPC_REL24: 367 case R_PPC_LOCAL24PC: 368 case R_PPC_PLTREL24: { 369 uint32_t mask = 0x03FFFFFC; 370 checkInt(loc, val, 26, rel); 371 checkAlignment(loc, val, 4, rel); 372 write32(loc, (read32(loc) & ~mask) | (val & mask)); 373 break; 374 } 375 default: 376 llvm_unreachable("unknown relocation"); 377 } 378 } 379 380 RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const { 381 if (expr == R_RELAX_TLS_GD_TO_IE) 382 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 383 if (expr == R_RELAX_TLS_LD_TO_LE) 384 return R_RELAX_TLS_LD_TO_LE_ABS; 385 return expr; 386 } 387 388 int PPC::getTlsGdRelaxSkip(RelType type) const { 389 // A __tls_get_addr call instruction is marked with 2 relocations: 390 // 391 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 392 // R_PPC_REL24: __tls_get_addr 393 // 394 // After the relaxation we no longer call __tls_get_addr and should skip both 395 // relocations to not create a false dependence on __tls_get_addr being 396 // defined. 397 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 398 return 2; 399 return 1; 400 } 401 402 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 403 uint64_t val) const { 404 switch (rel.type) { 405 case R_PPC_GOT_TLSGD16: { 406 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 407 uint32_t insn = readFromHalf16(loc); 408 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 409 relocateNoSym(loc, R_PPC_GOT_TPREL16, val); 410 break; 411 } 412 case R_PPC_TLSGD: 413 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 414 write32(loc, 0x7c631214); 415 break; 416 default: 417 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 418 } 419 } 420 421 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 422 uint64_t val) const { 423 switch (rel.type) { 424 case R_PPC_GOT_TLSGD16: 425 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 426 writeFromHalf16(loc, 0x3c620000 | ha(val)); 427 break; 428 case R_PPC_TLSGD: 429 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 430 write32(loc, 0x38630000 | lo(val)); 431 break; 432 default: 433 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 434 } 435 } 436 437 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 438 uint64_t val) const { 439 switch (rel.type) { 440 case R_PPC_GOT_TLSLD16: 441 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 442 writeFromHalf16(loc, 0x3c620000); 443 break; 444 case R_PPC_TLSLD: 445 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 446 // = r3+x-0x7000, so add 4096 to r3. 447 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 448 write32(loc, 0x38631000); 449 break; 450 case R_PPC_DTPREL16: 451 case R_PPC_DTPREL16_HA: 452 case R_PPC_DTPREL16_HI: 453 case R_PPC_DTPREL16_LO: 454 relocate(loc, rel, val); 455 break; 456 default: 457 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 458 } 459 } 460 461 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 462 uint64_t val) const { 463 switch (rel.type) { 464 case R_PPC_GOT_TPREL16: { 465 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 466 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 467 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 468 break; 469 } 470 case R_PPC_TLS: { 471 uint32_t insn = read32(loc); 472 if (insn >> 26 != 31) 473 error("unrecognized instruction for IE to LE R_PPC_TLS"); 474 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 475 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 476 if (dFormOp == 0) 477 error("unrecognized instruction for IE to LE R_PPC_TLS"); 478 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 479 break; 480 } 481 default: 482 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 483 } 484 } 485 486 TargetInfo *elf::getPPCTargetInfo() { 487 static PPC target; 488 return ⌖ 489 } 490