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 20 namespace lld { 21 namespace 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, uint64_t gotPltEntryAddr, uint64_t pltEntryAddr, 35 int32_t index, unsigned relOff) const override { 36 llvm_unreachable("should call writePPC32GlinkSection() instead"); 37 } 38 void writeGotPlt(uint8_t *buf, const Symbol &s) const override; 39 bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file, 40 uint64_t branchAddr, const Symbol &s, 41 int64_t a) const override; 42 uint32_t getThunkSectionSpacing() const override; 43 bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override; 44 void relocateOne(uint8_t *loc, RelType type, uint64_t val) const override; 45 RelExpr adjustRelaxExpr(RelType type, const uint8_t *data, 46 RelExpr expr) const override; 47 int getTlsGdRelaxSkip(RelType type) const override; 48 void relaxTlsGdToIe(uint8_t *loc, RelType type, uint64_t val) const override; 49 void relaxTlsGdToLe(uint8_t *loc, RelType type, uint64_t val) const override; 50 void relaxTlsLdToLe(uint8_t *loc, RelType type, uint64_t val) const override; 51 void relaxTlsIeToLe(uint8_t *loc, RelType type, uint64_t val) const override; 52 }; 53 } // namespace 54 55 static uint16_t lo(uint32_t v) { return v; } 56 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; } 57 58 static uint32_t readFromHalf16(const uint8_t *loc) { 59 return read32(config->isLE ? loc : loc - 2); 60 } 61 62 static void writeFromHalf16(uint8_t *loc, uint32_t insn) { 63 write32(config->isLE ? loc : loc - 2, insn); 64 } 65 66 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries) { 67 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an 68 // absolute address from a specific .plt slot (usually called .got.plt on 69 // other targets) and jumps there. 70 // 71 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load 72 // time. The .glink section is not used. 73 // b) With lazy binding, the .plt entry points to a `b PLTresolve` 74 // instruction in .glink, filled in by PPC::writeGotPlt(). 75 76 // Write N `b PLTresolve` first. 77 for (size_t i = 0; i != numEntries; ++i) 78 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i)); 79 buf += 4 * numEntries; 80 81 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve() 82 // computes the PLT index (by computing the distance from the landing b to 83 // itself) and calls _dl_runtime_resolve() (in glibc). 84 uint32_t got = in.got->getVA(); 85 uint32_t glink = in.plt->getVA(); // VA of .glink 86 const uint8_t *end = buf + 64; 87 if (config->isPic) { 88 uint32_t afterBcl = in.plt->getSize() - target->pltHeaderSize + 12; 89 uint32_t gotBcl = got + 4 - (glink + afterBcl); 90 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha 91 write32(buf + 4, 0x7c0802a6); // mflr r0 92 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4 93 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-.glink@l 94 write32(buf + 16, 0x7d8802a6); // mflr r12 95 write32(buf + 20, 0x7c0803a6); // mtlr r0 96 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12 97 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha 98 if (ha(gotBcl) == ha(gotBcl + 4)) { 99 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12) 100 write32(buf + 36, 101 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12) 102 } else { 103 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12) 104 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12) 105 } 106 write32(buf + 40, 0x7c0903a6); // mtctr 0 107 write32(buf + 44, 0x7c0b5a14); // add r0,11,11 108 write32(buf + 48, 0x7d605a14); // add r11,0,11 109 write32(buf + 52, 0x4e800420); // bctr 110 buf += 56; 111 } else { 112 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha 113 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-Glink@ha 114 if (ha(got + 4) == ha(got + 8)) 115 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12) 116 else 117 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12) 118 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-Glink@l 119 write32(buf + 16, 0x7c0903a6); // mtctr r0 120 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11 121 if (ha(got + 4) == ha(got + 8)) 122 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@ha(r12) 123 else 124 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12) 125 write32(buf + 28, 0x7d605a14); // add r11,r0,r11 126 write32(buf + 32, 0x4e800420); // bctr 127 buf += 36; 128 } 129 130 // Pad with nop. They should not be executed. 131 for (; buf < end; buf += 4) 132 write32(buf, 0x60000000); 133 } 134 135 PPC::PPC() { 136 gotRel = R_PPC_GLOB_DAT; 137 noneRel = R_PPC_NONE; 138 pltRel = R_PPC_JMP_SLOT; 139 relativeRel = R_PPC_RELATIVE; 140 iRelativeRel = R_PPC_IRELATIVE; 141 symbolicRel = R_PPC_ADDR32; 142 gotBaseSymInGotPlt = false; 143 gotHeaderEntriesNum = 3; 144 gotPltHeaderEntriesNum = 0; 145 pltHeaderSize = 64; // size of PLTresolve in .glink 146 pltEntrySize = 4; 147 148 needsThunks = true; 149 150 tlsModuleIndexRel = R_PPC_DTPMOD32; 151 tlsOffsetRel = R_PPC_DTPREL32; 152 tlsGotRel = R_PPC_TPREL32; 153 154 defaultMaxPageSize = 65536; 155 defaultImageBase = 0x10000000; 156 157 write32(trapInstr.data(), 0x7fe00008); 158 } 159 160 void PPC::writeGotHeader(uint8_t *buf) const { 161 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC 162 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1], 163 // link_map in _GLOBAL_OFFSET_TABLE_[2]. 164 write32(buf, mainPart->dynamic->getVA()); 165 } 166 167 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const { 168 // Address of the symbol resolver stub in .glink . 169 write32(buf, in.plt->getVA() + 4 * s.pltIndex); 170 } 171 172 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file, 173 uint64_t branchAddr, const Symbol &s, int64_t /*a*/) const { 174 if (type != R_PPC_REL24 && type != R_PPC_PLTREL24) 175 return false; 176 if (s.isInPlt()) 177 return true; 178 if (s.isUndefWeak()) 179 return false; 180 return !(expr == R_PC && PPC::inBranchRange(type, branchAddr, s.getVA())); 181 } 182 183 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; } 184 185 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 186 uint64_t offset = dst - src; 187 if (type == R_PPC_REL24 || type == R_PPC_PLTREL24) 188 return isInt<26>(offset); 189 llvm_unreachable("unsupported relocation type used in branch"); 190 } 191 192 RelExpr PPC::getRelExpr(RelType type, const Symbol &s, 193 const uint8_t *loc) const { 194 switch (type) { 195 case R_PPC_NONE: 196 return R_NONE; 197 case R_PPC_ADDR16_HA: 198 case R_PPC_ADDR16_HI: 199 case R_PPC_ADDR16_LO: 200 case R_PPC_ADDR32: 201 return R_ABS; 202 case R_PPC_DTPREL16: 203 case R_PPC_DTPREL16_HA: 204 case R_PPC_DTPREL16_HI: 205 case R_PPC_DTPREL16_LO: 206 case R_PPC_DTPREL32: 207 return R_DTPREL; 208 case R_PPC_REL14: 209 case R_PPC_REL32: 210 case R_PPC_LOCAL24PC: 211 case R_PPC_REL16_LO: 212 case R_PPC_REL16_HI: 213 case R_PPC_REL16_HA: 214 return R_PC; 215 case R_PPC_GOT16: 216 return R_GOT_OFF; 217 case R_PPC_REL24: 218 return R_PLT_PC; 219 case R_PPC_PLTREL24: 220 return R_PPC32_PLTREL; 221 case R_PPC_GOT_TLSGD16: 222 return R_TLSGD_GOT; 223 case R_PPC_GOT_TLSLD16: 224 return R_TLSLD_GOT; 225 case R_PPC_GOT_TPREL16: 226 return R_GOT_OFF; 227 case R_PPC_TLS: 228 return R_TLSIE_HINT; 229 case R_PPC_TLSGD: 230 return R_TLSDESC_CALL; 231 case R_PPC_TLSLD: 232 return R_TLSLD_HINT; 233 case R_PPC_TPREL16: 234 case R_PPC_TPREL16_HA: 235 case R_PPC_TPREL16_LO: 236 case R_PPC_TPREL16_HI: 237 return R_TLS; 238 default: 239 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + 240 ") against symbol " + toString(s)); 241 return R_NONE; 242 } 243 } 244 245 RelType PPC::getDynRel(RelType type) const { 246 if (type == R_PPC_ADDR32) 247 return type; 248 return R_PPC_NONE; 249 } 250 251 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) { 252 uint64_t dtpBiasedVal = val - 0x8000; 253 switch (type) { 254 case R_PPC_DTPREL16: 255 return {R_PPC64_ADDR16, dtpBiasedVal}; 256 case R_PPC_DTPREL16_HA: 257 return {R_PPC_ADDR16_HA, dtpBiasedVal}; 258 case R_PPC_DTPREL16_HI: 259 return {R_PPC_ADDR16_HI, dtpBiasedVal}; 260 case R_PPC_DTPREL16_LO: 261 return {R_PPC_ADDR16_LO, dtpBiasedVal}; 262 case R_PPC_DTPREL32: 263 return {R_PPC_ADDR32, dtpBiasedVal}; 264 default: 265 return {type, val}; 266 } 267 } 268 269 void PPC::relocateOne(uint8_t *loc, RelType type, uint64_t val) const { 270 RelType newType; 271 std::tie(newType, val) = fromDTPREL(type, val); 272 switch (newType) { 273 case R_PPC_ADDR16: 274 checkIntUInt(loc, val, 16, type); 275 write16(loc, val); 276 break; 277 case R_PPC_GOT16: 278 case R_PPC_GOT_TLSGD16: 279 case R_PPC_GOT_TLSLD16: 280 case R_PPC_GOT_TPREL16: 281 case R_PPC_TPREL16: 282 checkInt(loc, val, 16, type); 283 write16(loc, val); 284 break; 285 case R_PPC_ADDR16_HA: 286 case R_PPC_DTPREL16_HA: 287 case R_PPC_GOT_TLSGD16_HA: 288 case R_PPC_GOT_TLSLD16_HA: 289 case R_PPC_GOT_TPREL16_HA: 290 case R_PPC_REL16_HA: 291 case R_PPC_TPREL16_HA: 292 write16(loc, ha(val)); 293 break; 294 case R_PPC_ADDR16_HI: 295 case R_PPC_DTPREL16_HI: 296 case R_PPC_GOT_TLSGD16_HI: 297 case R_PPC_GOT_TLSLD16_HI: 298 case R_PPC_GOT_TPREL16_HI: 299 case R_PPC_REL16_HI: 300 case R_PPC_TPREL16_HI: 301 write16(loc, val >> 16); 302 break; 303 case R_PPC_ADDR16_LO: 304 case R_PPC_DTPREL16_LO: 305 case R_PPC_GOT_TLSGD16_LO: 306 case R_PPC_GOT_TLSLD16_LO: 307 case R_PPC_GOT_TPREL16_LO: 308 case R_PPC_REL16_LO: 309 case R_PPC_TPREL16_LO: 310 write16(loc, val); 311 break; 312 case R_PPC_ADDR32: 313 case R_PPC_REL32: 314 write32(loc, val); 315 break; 316 case R_PPC_REL14: { 317 uint32_t mask = 0x0000FFFC; 318 checkInt(loc, val, 16, type); 319 checkAlignment(loc, val, 4, type); 320 write32(loc, (read32(loc) & ~mask) | (val & mask)); 321 break; 322 } 323 case R_PPC_REL24: 324 case R_PPC_LOCAL24PC: 325 case R_PPC_PLTREL24: { 326 uint32_t mask = 0x03FFFFFC; 327 checkInt(loc, val, 26, type); 328 checkAlignment(loc, val, 4, type); 329 write32(loc, (read32(loc) & ~mask) | (val & mask)); 330 break; 331 } 332 default: 333 llvm_unreachable("unknown relocation"); 334 } 335 } 336 337 RelExpr PPC::adjustRelaxExpr(RelType type, const uint8_t *data, 338 RelExpr expr) const { 339 if (expr == R_RELAX_TLS_GD_TO_IE) 340 return R_RELAX_TLS_GD_TO_IE_GOT_OFF; 341 if (expr == R_RELAX_TLS_LD_TO_LE) 342 return R_RELAX_TLS_LD_TO_LE_ABS; 343 return expr; 344 } 345 346 int PPC::getTlsGdRelaxSkip(RelType type) const { 347 // A __tls_get_addr call instruction is marked with 2 relocations: 348 // 349 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation 350 // R_PPC_REL24: __tls_get_addr 351 // 352 // After the relaxation we no longer call __tls_get_addr and should skip both 353 // relocations to not create a false dependence on __tls_get_addr being 354 // defined. 355 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD) 356 return 2; 357 return 1; 358 } 359 360 void PPC::relaxTlsGdToIe(uint8_t *loc, RelType type, uint64_t val) const { 361 switch (type) { 362 case R_PPC_GOT_TLSGD16: { 363 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA) 364 uint32_t insn = readFromHalf16(loc); 365 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000)); 366 relocateOne(loc, R_PPC_GOT_TPREL16, val); 367 break; 368 } 369 case R_PPC_TLSGD: 370 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2 371 write32(loc, 0x7c631214); 372 break; 373 default: 374 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation"); 375 } 376 } 377 378 void PPC::relaxTlsGdToLe(uint8_t *loc, RelType type, uint64_t val) const { 379 switch (type) { 380 case R_PPC_GOT_TLSGD16: 381 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha 382 writeFromHalf16(loc, 0x3c620000 | ha(val)); 383 break; 384 case R_PPC_TLSGD: 385 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l 386 write32(loc, 0x38630000 | lo(val)); 387 break; 388 default: 389 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation"); 390 } 391 } 392 393 void PPC::relaxTlsLdToLe(uint8_t *loc, RelType type, uint64_t val) const { 394 switch (type) { 395 case R_PPC_GOT_TLSLD16: 396 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0 397 writeFromHalf16(loc, 0x3c620000); 398 break; 399 case R_PPC_TLSLD: 400 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel 401 // = r3+x-0x7000, so add 4096 to r3. 402 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096 403 write32(loc, 0x38631000); 404 break; 405 case R_PPC_DTPREL16: 406 case R_PPC_DTPREL16_HA: 407 case R_PPC_DTPREL16_HI: 408 case R_PPC_DTPREL16_LO: 409 relocateOne(loc, type, val); 410 break; 411 default: 412 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation"); 413 } 414 } 415 416 void PPC::relaxTlsIeToLe(uint8_t *loc, RelType type, uint64_t val) const { 417 switch (type) { 418 case R_PPC_GOT_TPREL16: { 419 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha 420 uint32_t rt = readFromHalf16(loc) & 0x03e00000; 421 writeFromHalf16(loc, 0x3c020000 | rt | ha(val)); 422 break; 423 } 424 case R_PPC_TLS: { 425 uint32_t insn = read32(loc); 426 if (insn >> 26 != 31) 427 error("unrecognized instruction for IE to LE R_PPC_TLS"); 428 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l 429 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1); 430 if (dFormOp == 0) 431 error("unrecognized instruction for IE to LE R_PPC_TLS"); 432 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val)); 433 break; 434 } 435 default: 436 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation"); 437 } 438 } 439 440 TargetInfo *getPPCTargetInfo() { 441 static PPC target; 442 return ⌖ 443 } 444 445 } // namespace elf 446 } // namespace lld 447