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