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 "lld/Common/ErrorHandler.h" 14 #include "llvm/Support/Endian.h" 15 16 using namespace llvm; 17 using namespace llvm::support::endian; 18 using namespace llvm::ELF; 19 using namespace lld; 20 using namespace lld::elf; 21 22 namespace { 23 class PPC final : public TargetInfo { 24 public: 25 PPC(); 26 RelExpr getRelExpr(RelType Type, const Symbol &S, 27 const uint8_t *Loc) const override; 28 RelType getDynRel(RelType Type) const override; 29 void writeGotHeader(uint8_t *Buf) const override; 30 void writePltHeader(uint8_t *Buf) const override { 31 llvm_unreachable("should call writePPC32GlinkSection() instead"); 32 } 33 void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr, 34 int32_t Index, unsigned RelOff) const override { 35 llvm_unreachable("should call writePPC32GlinkSection() instead"); 36 } 37 void writeGotPlt(uint8_t *Buf, const Symbol &S) const override; 38 bool needsThunk(RelExpr Expr, RelType RelocType, const InputFile *File, 39 uint64_t BranchAddr, const Symbol &S) const override; 40 uint32_t getThunkSectionSpacing() const override; 41 bool inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const override; 42 void relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const override; 43 RelExpr adjustRelaxExpr(RelType Type, const uint8_t *Data, 44 RelExpr Expr) const override; 45 int getTlsGdRelaxSkip(RelType Type) const override; 46 void relaxTlsGdToIe(uint8_t *Loc, RelType Type, uint64_t Val) const override; 47 void relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override; 48 void relaxTlsLdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override; 49 void relaxTlsIeToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override; 50 }; 51 } // namespace 52 53 static uint16_t lo(uint32_t V) { return V; } 54 static uint16_t ha(uint32_t V) { return (V + 0x8000) >> 16; } 55 56 static uint32_t readFromHalf16(const uint8_t *Loc) { 57 return read32(Config->IsLE ? Loc : Loc - 2); 58 } 59 60 static void writeFromHalf16(uint8_t *Loc, uint32_t Insn) { 61 write32(Config->IsLE ? Loc : Loc - 2, Insn); 62 } 63 64 void elf::writePPC32GlinkSection(uint8_t *Buf, size_t NumEntries) { 65 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an 66 // absolute address from a specific .plt slot (usually called .got.plt on 67 // other targets) and jumps there. 68 // 69 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load 70 // time. The .glink section is not used. 71 // b) With lazy binding, the .plt entry points to a `b PLTresolve` 72 // instruction in .glink, filled in by PPC::writeGotPlt(). 73 74 // Write N `b PLTresolve` first. 75 for (size_t I = 0; I != NumEntries; ++I) 76 write32(Buf + 4 * I, 0x48000000 | 4 * (NumEntries - I)); 77 Buf += 4 * NumEntries; 78 79 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve() 80 // computes the PLT index (by computing the distance from the landing b to 81 // itself) and calls _dl_runtime_resolve() (in glibc). 82 uint32_t GOT = In.Got->getVA(); 83 uint32_t Glink = In.Plt->getVA(); // VA of .glink 84 const uint8_t *End = Buf + 64; 85 if (Config->Pic) { 86 uint32_t AfterBcl = In.Plt->getSize() - Target->PltHeaderSize + 12; 87 uint32_t GotBcl = GOT + 4 - (Glink + AfterBcl); 88 write32(Buf + 0, 0x3d6b0000 | ha(AfterBcl)); // addis r11,r11,1f-glink@ha 89 write32(Buf + 4, 0x7c0802a6); // mflr r0 90 write32(Buf + 8, 0x429f0005); // bcl 20,30,.+4 91 write32(Buf + 12, 0x396b0000 | lo(AfterBcl)); // 1: addi r11,r11,1b-.glink@l 92 write32(Buf + 16, 0x7d8802a6); // mflr r12 93 write32(Buf + 20, 0x7c0803a6); // mtlr r0 94 write32(Buf + 24, 0x7d6c5850); // sub r11,r11,r12 95 write32(Buf + 28, 0x3d8c0000 | ha(GotBcl)); // addis 12,12,GOT+4-1b@ha 96 if (ha(GotBcl) == ha(GotBcl + 4)) { 97 write32(Buf + 32, 0x800c0000 | lo(GotBcl)); // lwz r0,r12,GOT+4-1b@l(r12) 98 write32(Buf + 36, 99 0x818c0000 | lo(GotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12) 100 } else { 101 write32(Buf + 32, 0x840c0000 | lo(GotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12) 102 write32(Buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12) 103 } 104 write32(Buf + 40, 0x7c0903a6); // mtctr 0 105 write32(Buf + 44, 0x7c0b5a14); // add r0,11,11 106 write32(Buf + 48, 0x7d605a14); // add r11,0,11 107 write32(Buf + 52, 0x4e800420); // bctr 108 Buf += 56; 109 } else { 110 write32(Buf + 0, 0x3d800000 | ha(GOT + 4)); // lis r12,GOT+4@ha 111 write32(Buf + 4, 0x3d6b0000 | ha(-Glink)); // addis r11,r11,-Glink@ha 112 if (ha(GOT + 4) == ha(GOT + 8)) 113 write32(Buf + 8, 0x800c0000 | lo(GOT + 4)); // lwz r0,GOT+4@l(r12) 114 else 115 write32(Buf + 8, 0x840c0000 | lo(GOT + 4)); // lwzu r0,GOT+4@l(r12) 116 write32(Buf + 12, 0x396b0000 | lo(-Glink)); // addi r11,r11,-Glink@l 117 write32(Buf + 16, 0x7c0903a6); // mtctr r0 118 write32(Buf + 20, 0x7c0b5a14); // add r0,r11,r11 119 if (ha(GOT + 4) == ha(GOT + 8)) 120 write32(Buf + 24, 0x818c0000 | lo(GOT + 8)); // lwz r12,GOT+8@ha(r12) 121 else 122 write32(Buf + 24, 0x818c0000 | 4); // lwz r12,4(r12) 123 write32(Buf + 28, 0x7d605a14); // add r11,r0,r11 124 write32(Buf + 32, 0x4e800420); // bctr 125 Buf += 36; 126 } 127 128 // Pad with nop. They should not be executed. 129 for (; Buf < End; Buf += 4) 130 write32(Buf, 0x60000000); 131 } 132 133 PPC::PPC() { 134 GotRel = R_PPC_GLOB_DAT; 135 NoneRel = R_PPC_NONE; 136 PltRel = R_PPC_JMP_SLOT; 137 RelativeRel = R_PPC_RELATIVE; 138 IRelativeRel = R_PPC_IRELATIVE; 139 SymbolicRel = R_PPC_ADDR32; 140 GotBaseSymInGotPlt = false; 141 GotHeaderEntriesNum = 3; 142 GotPltHeaderEntriesNum = 0; 143 PltHeaderSize = 64; // size of PLTresolve in .glink 144 PltEntrySize = 4; 145 146 NeedsThunks = true; 147 148 TlsModuleIndexRel = R_PPC_DTPMOD32; 149 TlsOffsetRel = R_PPC_DTPREL32; 150 TlsGotRel = R_PPC_TPREL32; 151 152 DefaultMaxPageSize = 65536; 153 DefaultImageBase = 0x10000000; 154 155 write32(TrapInstr.data(), 0x7fe00008); 156 } 157 158 void PPC::writeGotHeader(uint8_t *Buf) const { 159 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC 160 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1], 161 // link_map in _GLOBAL_OFFSET_TABLE_[2]. 162 write32(Buf, Main->Dynamic->getVA()); 163 } 164 165 void PPC::writeGotPlt(uint8_t *Buf, const Symbol &S) const { 166 // Address of the symbol resolver stub in .glink . 167 write32(Buf, In.Plt->getVA() + 4 * S.PltIndex); 168 } 169 170 bool PPC::needsThunk(RelExpr Expr, RelType Type, const InputFile *File, 171 uint64_t BranchAddr, const Symbol &S) const { 172 if (Type != R_PPC_REL24 && Type != R_PPC_PLTREL24) 173 return false; 174 if (S.isInPlt()) 175 return true; 176 if (S.isUndefWeak()) 177 return false; 178 return !(Expr == R_PC && PPC::inBranchRange(Type, BranchAddr, S.getVA())); 179 } 180 181 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 182 183 bool PPC::inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const { 184 uint64_t Offset = Dst - Src; 185 if (Type == R_PPC_REL24 || Type == R_PPC_PLTREL24) 186 return isInt<26>(Offset); 187 llvm_unreachable("unsupported relocation type used in branch"); 188 } 189 190 RelExpr PPC::getRelExpr(RelType Type, const Symbol &S, 191 const uint8_t *Loc) const { 192 switch (Type) { 193 case R_PPC_DTPREL16: 194 case R_PPC_DTPREL16_HA: 195 case R_PPC_DTPREL16_HI: 196 case R_PPC_DTPREL16_LO: 197 case R_PPC_DTPREL32: 198 return R_DTPREL; 199 case R_PPC_REL14: 200 case R_PPC_REL32: 201 case R_PPC_LOCAL24PC: 202 case R_PPC_REL16_LO: 203 case R_PPC_REL16_HI: 204 case R_PPC_REL16_HA: 205 return R_PC; 206 case R_PPC_GOT16: 207 return R_GOT_OFF; 208 case R_PPC_REL24: 209 return R_PLT_PC; 210 case R_PPC_PLTREL24: 211 return R_PPC32_PLTREL; 212 case R_PPC_GOT_TLSGD16: 213 return R_TLSGD_GOT; 214 case R_PPC_GOT_TLSLD16: 215 return R_TLSLD_GOT; 216 case R_PPC_GOT_TPREL16: 217 return R_GOT_OFF; 218 case R_PPC_TLS: 219 return R_TLSIE_HINT; 220 case R_PPC_TLSGD: 221 return R_TLSDESC_CALL; 222 case R_PPC_TLSLD: 223 return R_TLSLD_HINT; 224 case R_PPC_TPREL16: 225 case R_PPC_TPREL16_HA: 226 case R_PPC_TPREL16_LO: 227 case R_PPC_TPREL16_HI: 228 return R_TLS; 229 default: 230 return R_ABS; 231 } 232 } 233 234 RelType PPC::getDynRel(RelType Type) const { 235 if (Type == R_PPC_ADDR32) 236 return Type; 237 return R_PPC_NONE; 238 } 239 240 static std::pair<RelType, uint64_t> fromDTPREL(RelType Type, uint64_t Val) { 241 uint64_t DTPBiasedVal = Val - 0x8000; 242 switch (Type) { 243 case R_PPC_DTPREL16: 244 return {R_PPC64_ADDR16, DTPBiasedVal}; 245 case R_PPC_DTPREL16_HA: 246 return {R_PPC_ADDR16_HA, DTPBiasedVal}; 247 case R_PPC_DTPREL16_HI: 248 return {R_PPC_ADDR16_HI, DTPBiasedVal}; 249 case R_PPC_DTPREL16_LO: 250 return {R_PPC_ADDR16_LO, DTPBiasedVal}; 251 case R_PPC_DTPREL32: 252 return {R_PPC_ADDR32, DTPBiasedVal}; 253 default: 254 return {Type, Val}; 255 } 256 } 257 258 void PPC::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const { 259 RelType NewType; 260 std::tie(NewType, Val) = fromDTPREL(Type, Val); 261 switch (NewType) { 262 case R_PPC_ADDR16: 263 checkIntUInt(Loc, Val, 16, Type); 264 write16(Loc, Val); 265 break; 266 case R_PPC_GOT16: 267 case R_PPC_GOT_TLSGD16: 268 case R_PPC_GOT_TLSLD16: 269 case R_PPC_GOT_TPREL16: 270 case R_PPC_TPREL16: 271 checkInt(Loc, Val, 16, Type); 272 write16(Loc, Val); 273 break; 274 case R_PPC_ADDR16_HA: 275 case R_PPC_DTPREL16_HA: 276 case R_PPC_GOT_TLSGD16_HA: 277 case R_PPC_GOT_TLSLD16_HA: 278 case R_PPC_GOT_TPREL16_HA: 279 case R_PPC_REL16_HA: 280 case R_PPC_TPREL16_HA: 281 write16(Loc, ha(Val)); 282 break; 283 case R_PPC_ADDR16_HI: 284 case R_PPC_DTPREL16_HI: 285 case R_PPC_GOT_TLSGD16_HI: 286 case R_PPC_GOT_TLSLD16_HI: 287 case R_PPC_GOT_TPREL16_HI: 288 case R_PPC_REL16_HI: 289 case R_PPC_TPREL16_HI: 290 write16(Loc, Val >> 16); 291 break; 292 case R_PPC_ADDR16_LO: 293 case R_PPC_DTPREL16_LO: 294 case R_PPC_GOT_TLSGD16_LO: 295 case R_PPC_GOT_TLSLD16_LO: 296 case R_PPC_GOT_TPREL16_LO: 297 case R_PPC_REL16_LO: 298 case R_PPC_TPREL16_LO: 299 write16(Loc, Val); 300 break; 301 case R_PPC_ADDR32: 302 case R_PPC_REL32: 303 write32(Loc, Val); 304 break; 305 case R_PPC_REL14: { 306 uint32_t Mask = 0x0000FFFC; 307 checkInt(Loc, Val, 16, Type); 308 checkAlignment(Loc, Val, 4, Type); 309 write32(Loc, (read32(Loc) & ~Mask) | (Val & Mask)); 310 break; 311 } 312 case R_PPC_REL24: 313 case R_PPC_LOCAL24PC: 314 case R_PPC_PLTREL24: { 315 uint32_t Mask = 0x03FFFFFC; 316 checkInt(Loc, Val, 26, Type); 317 checkAlignment(Loc, Val, 4, Type); 318 write32(Loc, (read32(Loc) & ~Mask) | (Val & Mask)); 319 break; 320 } 321 default: 322 error(getErrorLocation(Loc) + "unrecognized relocation " + toString(Type)); 323 } 324 } 325 326 RelExpr PPC::adjustRelaxExpr(RelType Type, const uint8_t *Data, 327 RelExpr Expr) const { 328 if (Expr == R_RELAX_TLS_GD_TO_IE) 329 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 330 if (Expr == R_RELAX_TLS_LD_TO_LE) 331 return R_RELAX_TLS_LD_TO_LE_ABS; 332 return Expr; 333 } 334 335 int PPC::getTlsGdRelaxSkip(RelType Type) const { 336 // A __tls_get_addr call instruction is marked with 2 relocations: 337 // 338 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 339 // R_PPC_REL24: __tls_get_addr 340 // 341 // After the relaxation we no longer call __tls_get_addr and should skip both 342 // relocations to not create a false dependence on __tls_get_addr being 343 // defined. 344 if (Type == R_PPC_TLSGD || Type == R_PPC_TLSLD) 345 return 2; 346 return 1; 347 } 348 349 void PPC::relaxTlsGdToIe(uint8_t *Loc, RelType Type, uint64_t Val) const { 350 switch (Type) { 351 case R_PPC_GOT_TLSGD16: { 352 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 353 uint32_t Insn = readFromHalf16(Loc); 354 writeFromHalf16(Loc, 0x80000000 | (Insn & 0x03ff0000)); 355 relocateOne(Loc, R_PPC_GOT_TPREL16, Val); 356 break; 357 } 358 case R_PPC_TLSGD: 359 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 360 write32(Loc, 0x7c631214); 361 break; 362 default: 363 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 364 } 365 } 366 367 void PPC::relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const { 368 switch (Type) { 369 case R_PPC_GOT_TLSGD16: 370 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 371 writeFromHalf16(Loc, 0x3c620000 | ha(Val)); 372 break; 373 case R_PPC_TLSGD: 374 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 375 write32(Loc, 0x38630000 | lo(Val)); 376 break; 377 default: 378 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 379 } 380 } 381 382 void PPC::relaxTlsLdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const { 383 switch (Type) { 384 case R_PPC_GOT_TLSLD16: 385 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 386 writeFromHalf16(Loc, 0x3c620000); 387 break; 388 case R_PPC_TLSLD: 389 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 390 // = r3+x-0x7000, so add 4096 to r3. 391 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 392 write32(Loc, 0x38631000); 393 break; 394 case R_PPC_DTPREL16: 395 case R_PPC_DTPREL16_HA: 396 case R_PPC_DTPREL16_HI: 397 case R_PPC_DTPREL16_LO: 398 relocateOne(Loc, Type, Val); 399 break; 400 default: 401 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 402 } 403 } 404 405 void PPC::relaxTlsIeToLe(uint8_t *Loc, RelType Type, uint64_t Val) const { 406 switch (Type) { 407 case R_PPC_GOT_TPREL16: { 408 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 409 uint32_t RT = readFromHalf16(Loc) & 0x03e00000; 410 writeFromHalf16(Loc, 0x3c020000 | RT | ha(Val)); 411 break; 412 } 413 case R_PPC_TLS: { 414 uint32_t Insn = read32(Loc); 415 if (Insn >> 26 != 31) 416 error("unrecognized instruction for IE to LE R_PPC_TLS"); 417 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 418 uint32_t DFormOp = getPPCDFormOp((read32(Loc) & 0x000007fe) >> 1); 419 if (DFormOp == 0) 420 error("unrecognized instruction for IE to LE R_PPC_TLS"); 421 write32(Loc, (DFormOp << 26) | (Insn & 0x03ff0000) | lo(Val)); 422 break; 423 } 424 default: 425 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 426 } 427 } 428 429 TargetInfo *elf::getPPCTargetInfo() { 430 static PPC Target; 431 return &Target; 432 } 433