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 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 61 static uint16_t lo(uint32_t v) { return v; } 62 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; } 63 64 static uint32_t readFromHalf16(const uint8_t *loc) { 65 return read32(config->isLE ? loc : loc - 2); 66 } 67 68 static void writeFromHalf16(uint8_t *loc, uint32_t insn) { 69 write32(config->isLE ? loc : loc - 2, insn); 70 } 71 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 } 150 151 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 } 177 178 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 } 184 185 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 } 191 192 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 } 196 197 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 } 207 208 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 209 210 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 } 216 217 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_ADDR24: 226 case R_PPC_ADDR32: 227 return R_ABS; 228 case R_PPC_DTPREL16: 229 case R_PPC_DTPREL16_HA: 230 case R_PPC_DTPREL16_HI: 231 case R_PPC_DTPREL16_LO: 232 case R_PPC_DTPREL32: 233 return R_DTPREL; 234 case R_PPC_REL14: 235 case R_PPC_REL32: 236 case R_PPC_REL16_LO: 237 case R_PPC_REL16_HI: 238 case R_PPC_REL16_HA: 239 return R_PC; 240 case R_PPC_GOT16: 241 return R_GOT_OFF; 242 case R_PPC_LOCAL24PC: 243 case R_PPC_REL24: 244 return R_PLT_PC; 245 case R_PPC_PLTREL24: 246 return R_PPC32_PLTREL; 247 case R_PPC_GOT_TLSGD16: 248 return R_TLSGD_GOT; 249 case R_PPC_GOT_TLSLD16: 250 return R_TLSLD_GOT; 251 case R_PPC_GOT_TPREL16: 252 return R_GOT_OFF; 253 case R_PPC_TLS: 254 return R_TLSIE_HINT; 255 case R_PPC_TLSGD: 256 return R_TLSDESC_CALL; 257 case R_PPC_TLSLD: 258 return R_TLSLD_HINT; 259 case R_PPC_TPREL16: 260 case R_PPC_TPREL16_HA: 261 case R_PPC_TPREL16_LO: 262 case R_PPC_TPREL16_HI: 263 return R_TPREL; 264 default: 265 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 266 ") against symbol " + toString(s)); 267 return R_NONE; 268 } 269 } 270 271 RelType PPC::getDynRel(RelType type) const { 272 if (type == R_PPC_ADDR32) 273 return type; 274 return R_PPC_NONE; 275 } 276 277 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 278 uint64_t dtpBiasedVal = val - 0x8000; 279 switch (type) { 280 case R_PPC_DTPREL16: 281 return {R_PPC64_ADDR16, dtpBiasedVal}; 282 case R_PPC_DTPREL16_HA: 283 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 284 case R_PPC_DTPREL16_HI: 285 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 286 case R_PPC_DTPREL16_LO: 287 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 288 case R_PPC_DTPREL32: 289 return {R_PPC_ADDR32, dtpBiasedVal}; 290 default: 291 return {type, val}; 292 } 293 } 294 295 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { 296 RelType newType; 297 std::tie(newType, val) = fromDTPREL(rel.type, val); 298 switch (newType) { 299 case R_PPC_ADDR16: 300 checkIntUInt(loc, val, 16, rel); 301 write16(loc, val); 302 break; 303 case R_PPC_GOT16: 304 case R_PPC_GOT_TLSGD16: 305 case R_PPC_GOT_TLSLD16: 306 case R_PPC_GOT_TPREL16: 307 case R_PPC_TPREL16: 308 checkInt(loc, val, 16, rel); 309 write16(loc, val); 310 break; 311 case R_PPC_ADDR16_HA: 312 case R_PPC_DTPREL16_HA: 313 case R_PPC_GOT_TLSGD16_HA: 314 case R_PPC_GOT_TLSLD16_HA: 315 case R_PPC_GOT_TPREL16_HA: 316 case R_PPC_REL16_HA: 317 case R_PPC_TPREL16_HA: 318 write16(loc, ha(val)); 319 break; 320 case R_PPC_ADDR16_HI: 321 case R_PPC_DTPREL16_HI: 322 case R_PPC_GOT_TLSGD16_HI: 323 case R_PPC_GOT_TLSLD16_HI: 324 case R_PPC_GOT_TPREL16_HI: 325 case R_PPC_REL16_HI: 326 case R_PPC_TPREL16_HI: 327 write16(loc, val >> 16); 328 break; 329 case R_PPC_ADDR16_LO: 330 case R_PPC_DTPREL16_LO: 331 case R_PPC_GOT_TLSGD16_LO: 332 case R_PPC_GOT_TLSLD16_LO: 333 case R_PPC_GOT_TPREL16_LO: 334 case R_PPC_REL16_LO: 335 case R_PPC_TPREL16_LO: 336 write16(loc, val); 337 break; 338 case R_PPC_ADDR32: 339 case R_PPC_REL32: 340 write32(loc, val); 341 break; 342 case R_PPC_REL14: { 343 uint32_t mask = 0x0000FFFC; 344 checkInt(loc, val, 16, rel); 345 checkAlignment(loc, val, 4, rel); 346 write32(loc, (read32(loc) & ~mask) | (val & mask)); 347 break; 348 } 349 case R_PPC_ADDR24: 350 case R_PPC_REL24: 351 case R_PPC_LOCAL24PC: 352 case R_PPC_PLTREL24: { 353 uint32_t mask = 0x03FFFFFC; 354 checkInt(loc, val, 26, rel); 355 checkAlignment(loc, val, 4, rel); 356 write32(loc, (read32(loc) & ~mask) | (val & mask)); 357 break; 358 } 359 default: 360 llvm_unreachable("unknown relocation"); 361 } 362 } 363 364 RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const { 365 if (expr == R_RELAX_TLS_GD_TO_IE) 366 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 367 if (expr == R_RELAX_TLS_LD_TO_LE) 368 return R_RELAX_TLS_LD_TO_LE_ABS; 369 return expr; 370 } 371 372 int PPC::getTlsGdRelaxSkip(RelType type) const { 373 // A __tls_get_addr call instruction is marked with 2 relocations: 374 // 375 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 376 // R_PPC_REL24: __tls_get_addr 377 // 378 // After the relaxation we no longer call __tls_get_addr and should skip both 379 // relocations to not create a false dependence on __tls_get_addr being 380 // defined. 381 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 382 return 2; 383 return 1; 384 } 385 386 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 387 uint64_t val) const { 388 switch (rel.type) { 389 case R_PPC_GOT_TLSGD16: { 390 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 391 uint32_t insn = readFromHalf16(loc); 392 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 393 relocateNoSym(loc, R_PPC_GOT_TPREL16, val); 394 break; 395 } 396 case R_PPC_TLSGD: 397 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 398 write32(loc, 0x7c631214); 399 break; 400 default: 401 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 402 } 403 } 404 405 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 406 uint64_t val) const { 407 switch (rel.type) { 408 case R_PPC_GOT_TLSGD16: 409 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 410 writeFromHalf16(loc, 0x3c620000 | ha(val)); 411 break; 412 case R_PPC_TLSGD: 413 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 414 write32(loc, 0x38630000 | lo(val)); 415 break; 416 default: 417 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 418 } 419 } 420 421 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 422 uint64_t val) const { 423 switch (rel.type) { 424 case R_PPC_GOT_TLSLD16: 425 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 426 writeFromHalf16(loc, 0x3c620000); 427 break; 428 case R_PPC_TLSLD: 429 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 430 // = r3+x-0x7000, so add 4096 to r3. 431 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 432 write32(loc, 0x38631000); 433 break; 434 case R_PPC_DTPREL16: 435 case R_PPC_DTPREL16_HA: 436 case R_PPC_DTPREL16_HI: 437 case R_PPC_DTPREL16_LO: 438 relocate(loc, rel, val); 439 break; 440 default: 441 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 442 } 443 } 444 445 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 446 uint64_t val) const { 447 switch (rel.type) { 448 case R_PPC_GOT_TPREL16: { 449 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 450 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 451 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 452 break; 453 } 454 case R_PPC_TLS: { 455 uint32_t insn = read32(loc); 456 if (insn >> 26 != 31) 457 error("unrecognized instruction for IE to LE R_PPC_TLS"); 458 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 459 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 460 if (dFormOp == 0) 461 error("unrecognized instruction for IE to LE R_PPC_TLS"); 462 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 463 break; 464 } 465 default: 466 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 467 } 468 } 469 470 TargetInfo *elf::getPPCTargetInfo() { 471 static PPC target; 472 return ⌖ 473 } 474