lld/ELF/Arch/PPC.cpp

   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(Ctx &);
  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 relocateAlloc(InputSectionBase &sec, uint8_t *buf) const override;
  55
  56 private:
  57   void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
  58   void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
  59   void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
  60   void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
  61 };
  62 } // namespace
  63
  64 static uint16_t lo(uint32_t v) { return v; }
  65 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; }
  66
  67 static uint32_t readFromHalf16(Ctx &ctx, const uint8_t *loc) {
  68   return read32(ctx, ctx.arg.isLE ? loc : loc - 2);
  69 }
  70
  71 static void writeFromHalf16(Ctx &ctx, uint8_t *loc, uint32_t insn) {
  72   write32(ctx, ctx.arg.isLE ? loc : loc - 2, insn);
  73 }
  74
  75 void elf::writePPC32GlinkSection(Ctx &ctx, uint8_t *buf, size_t numEntries) {
  76   // Create canonical PLT entries for non-PIE code. Compilers don't generate
  77   // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE.
  78   uint32_t glink = ctx.in.plt->getVA(); // VA of .glink
  79   if (!ctx.arg.isPic) {
  80     for (const Symbol *sym :
  81          cast<PPC32GlinkSection>(*ctx.in.plt).canonical_plts) {
  82       writePPC32PltCallStub(ctx, buf, sym->getGotPltVA(ctx), 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(ctx, 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 = ctx.in.got->getVA();
 106   const uint8_t *end = buf + 64;
 107   if (ctx.arg.isPic) {
 108     uint32_t afterBcl = 4 * ctx.in.plt->getNumEntries() + 12;
 109     uint32_t gotBcl = got + 4 - (glink + afterBcl);
 110     write32(ctx, buf + 0,
 111             0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha
 112     write32(ctx, buf + 4, 0x7c0802a6);  // mflr r0
 113     write32(ctx, buf + 8, 0x429f0005);  // bcl 20,30,.+4
 114     write32(ctx, buf + 12,
 115             0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l
 116     write32(ctx, buf + 16, 0x7d8802a6); // mflr r12
 117     write32(ctx, buf + 20, 0x7c0803a6); // mtlr r0
 118     write32(ctx, buf + 24, 0x7d6c5850); // sub r11,r11,r12
 119     write32(ctx, buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha
 120     if (ha(gotBcl) == ha(gotBcl + 4)) {
 121       write32(ctx, buf + 32,
 122               0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12)
 123       write32(ctx, buf + 36,
 124               0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12)
 125     } else {
 126       write32(ctx, buf + 32,
 127               0x840c0000 | lo(gotBcl));       // lwzu r0,r12,GOT+4-1b@l(r12)
 128       write32(ctx, buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12)
 129     }
 130     write32(ctx, buf + 40, 0x7c0903a6); // mtctr 0
 131     write32(ctx, buf + 44, 0x7c0b5a14); // add r0,11,11
 132     write32(ctx, buf + 48, 0x7d605a14); // add r11,0,11
 133     write32(ctx, buf + 52, 0x4e800420); // bctr
 134     buf += 56;
 135   } else {
 136     write32(ctx, buf + 0, 0x3d800000 | ha(got + 4)); // lis     r12,GOT+4@ha
 137     write32(ctx, buf + 4, 0x3d6b0000 | ha(-glink)); // addis   r11,r11,-glink@ha
 138     if (ha(got + 4) == ha(got + 8))
 139       write32(ctx, buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12)
 140     else
 141       write32(ctx, buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12)
 142     write32(ctx, buf + 12, 0x396b0000 | lo(-glink)); // addi    r11,r11,-glink@l
 143     write32(ctx, buf + 16, 0x7c0903a6);              // mtctr   r0
 144     write32(ctx, buf + 20, 0x7c0b5a14);              // add     r0,r11,r11
 145     if (ha(got + 4) == ha(got + 8))
 146       write32(ctx, buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12)
 147     else
 148       write32(ctx, buf + 24, 0x818c0000 | 4); // lwz r12,4(r12)
 149     write32(ctx, buf + 28, 0x7d605a14);       // add     r11,r0,r11
 150     write32(ctx, buf + 32, 0x4e800420);       // bctr
 151     buf += 36;
 152   }
 153
 154   // Pad with nop. They should not be executed.
 155   for (; buf < end; buf += 4)
 156     write32(ctx, buf, 0x60000000);
 157 }
 158
 159 PPC::PPC(Ctx &ctx) : TargetInfo(ctx) {
 160   copyRel = R_PPC_COPY;
 161   gotRel = R_PPC_GLOB_DAT;
 162   pltRel = R_PPC_JMP_SLOT;
 163   relativeRel = R_PPC_RELATIVE;
 164   iRelativeRel = R_PPC_IRELATIVE;
 165   symbolicRel = R_PPC_ADDR32;
 166   gotHeaderEntriesNum = 3;
 167   gotPltHeaderEntriesNum = 0;
 168   pltHeaderSize = 0;
 169   pltEntrySize = 4;
 170   ipltEntrySize = 16;
 171
 172   needsThunks = true;
 173
 174   tlsModuleIndexRel = R_PPC_DTPMOD32;
 175   tlsOffsetRel = R_PPC_DTPREL32;
 176   tlsGotRel = R_PPC_TPREL32;
 177
 178   defaultMaxPageSize = 65536;
 179   defaultImageBase = 0x10000000;
 180
 181   write32(ctx, trapInstr.data(), 0x7fe00008);
 182 }
 183
 184 void PPC::writeIplt(uint8_t *buf, const Symbol &sym,
 185                     uint64_t /*pltEntryAddr*/) const {
 186   // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a
 187   // .got2.plt_pic32. thunk.
 188   writePPC32PltCallStub(ctx, buf, sym.getGotPltVA(ctx), sym.file, 0x8000);
 189 }
 190
 191 void PPC::writeGotHeader(uint8_t *buf) const {
 192   // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC
 193   // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1],
 194   // link_map in _GLOBAL_OFFSET_TABLE_[2].
 195   write32(ctx, buf, ctx.mainPart->dynamic->getVA());
 196 }
 197
 198 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const {
 199   // Address of the symbol resolver stub in .glink .
 200   write32(ctx, buf,
 201           ctx.in.plt->getVA() + ctx.in.plt->headerSize + 4 * s.getPltIdx(ctx));
 202 }
 203
 204 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file,
 205                      uint64_t branchAddr, const Symbol &s, int64_t a) const {
 206   if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24)
 207     return false;
 208   if (s.isInPlt(ctx))
 209     return true;
 210   if (s.isUndefWeak())
 211     return false;
 212   return !PPC::inBranchRange(type, branchAddr, s.getVA(ctx, a));
 213 }
 214
 215 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; }
 216
 217 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
 218   uint64_t offset = dst - src;
 219   if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24)
 220     return isInt<26>(offset);
 221   llvm_unreachable("unsupported relocation type used in branch");
 222 }
 223
 224 RelExpr PPC::getRelExpr(RelType type, const Symbol &s,
 225                         const uint8_t *loc) const {
 226   switch (type) {
 227   case R_PPC_NONE:
 228     return R_NONE;
 229   case R_PPC_ADDR16_HA:
 230   case R_PPC_ADDR16_HI:
 231   case R_PPC_ADDR16_LO:
 232   case R_PPC_ADDR24:
 233   case R_PPC_ADDR32:
 234     return R_ABS;
 235   case R_PPC_DTPREL16:
 236   case R_PPC_DTPREL16_HA:
 237   case R_PPC_DTPREL16_HI:
 238   case R_PPC_DTPREL16_LO:
 239   case R_PPC_DTPREL32:
 240     return R_DTPREL;
 241   case R_PPC_REL14:
 242   case R_PPC_REL32:
 243   case R_PPC_REL16_LO:
 244   case R_PPC_REL16_HI:
 245   case R_PPC_REL16_HA:
 246     return R_PC;
 247   case R_PPC_GOT16:
 248     return R_GOT_OFF;
 249   case R_PPC_LOCAL24PC:
 250   case R_PPC_REL24:
 251     return R_PLT_PC;
 252   case R_PPC_PLTREL24:
 253     return RE_PPC32_PLTREL;
 254   case R_PPC_GOT_TLSGD16:
 255     return R_TLSGD_GOT;
 256   case R_PPC_GOT_TLSLD16:
 257     return R_TLSLD_GOT;
 258   case R_PPC_GOT_TPREL16:
 259     return R_GOT_OFF;
 260   case R_PPC_TLS:
 261     return R_TLSIE_HINT;
 262   case R_PPC_TLSGD:
 263     return R_TLSDESC_CALL;
 264   case R_PPC_TLSLD:
 265     return R_TLSLD_HINT;
 266   case R_PPC_TPREL16:
 267   case R_PPC_TPREL16_HA:
 268   case R_PPC_TPREL16_LO:
 269   case R_PPC_TPREL16_HI:
 270     return R_TPREL;
 271   default:
 272     Err(ctx) << getErrorLoc(ctx, loc) << "unknown relocation (" << type.v
 273              << ") against symbol " << &s;
 274     return R_NONE;
 275   }
 276 }
 277
 278 RelType PPC::getDynRel(RelType type) const {
 279   if (type == R_PPC_ADDR32)
 280     return type;
 281   return R_PPC_NONE;
 282 }
 283
 284 int64_t PPC::getImplicitAddend(const uint8_t *buf, RelType type) const {
 285   switch (type) {
 286   case R_PPC_NONE:
 287   case R_PPC_GLOB_DAT:
 288   case R_PPC_JMP_SLOT:
 289     return 0;
 290   case R_PPC_ADDR32:
 291   case R_PPC_REL32:
 292   case R_PPC_RELATIVE:
 293   case R_PPC_IRELATIVE:
 294   case R_PPC_DTPMOD32:
 295   case R_PPC_DTPREL32:
 296   case R_PPC_TPREL32:
 297     return SignExtend64<32>(read32(ctx, buf));
 298   default:
 299     InternalErr(ctx, buf) << "cannot read addend for relocation " << type;
 300     return 0;
 301   }
 302 }
 303
 304 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) {
 305   uint64_t dtpBiasedVal = val - 0x8000;
 306   switch (type) {
 307   case R_PPC_DTPREL16:
 308     return {R_PPC64_ADDR16, dtpBiasedVal};
 309   case R_PPC_DTPREL16_HA:
 310     return {R_PPC_ADDR16_HA, dtpBiasedVal};
 311   case R_PPC_DTPREL16_HI:
 312     return {R_PPC_ADDR16_HI, dtpBiasedVal};
 313   case R_PPC_DTPREL16_LO:
 314     return {R_PPC_ADDR16_LO, dtpBiasedVal};
 315   case R_PPC_DTPREL32:
 316     return {R_PPC_ADDR32, dtpBiasedVal};
 317   default:
 318     return {type, val};
 319   }
 320 }
 321
 322 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
 323   RelType newType;
 324   std::tie(newType, val) = fromDTPREL(rel.type, val);
 325   switch (newType) {
 326   case R_PPC_ADDR16:
 327     checkIntUInt(ctx, loc, val, 16, rel);
 328     write16(ctx, loc, val);
 329     break;
 330   case R_PPC_GOT16:
 331   case R_PPC_GOT_TLSGD16:
 332   case R_PPC_GOT_TLSLD16:
 333   case R_PPC_GOT_TPREL16:
 334   case R_PPC_TPREL16:
 335     checkInt(ctx, loc, val, 16, rel);
 336     write16(ctx, loc, val);
 337     break;
 338   case R_PPC_ADDR16_HA:
 339   case R_PPC_DTPREL16_HA:
 340   case R_PPC_GOT_TLSGD16_HA:
 341   case R_PPC_GOT_TLSLD16_HA:
 342   case R_PPC_GOT_TPREL16_HA:
 343   case R_PPC_REL16_HA:
 344   case R_PPC_TPREL16_HA:
 345     write16(ctx, loc, ha(val));
 346     break;
 347   case R_PPC_ADDR16_HI:
 348   case R_PPC_DTPREL16_HI:
 349   case R_PPC_GOT_TLSGD16_HI:
 350   case R_PPC_GOT_TLSLD16_HI:
 351   case R_PPC_GOT_TPREL16_HI:
 352   case R_PPC_REL16_HI:
 353   case R_PPC_TPREL16_HI:
 354     write16(ctx, loc, val >> 16);
 355     break;
 356   case R_PPC_ADDR16_LO:
 357   case R_PPC_DTPREL16_LO:
 358   case R_PPC_GOT_TLSGD16_LO:
 359   case R_PPC_GOT_TLSLD16_LO:
 360   case R_PPC_GOT_TPREL16_LO:
 361   case R_PPC_REL16_LO:
 362   case R_PPC_TPREL16_LO:
 363     write16(ctx, loc, val);
 364     break;
 365   case R_PPC_ADDR32:
 366   case R_PPC_REL32:
 367     write32(ctx, loc, val);
 368     break;
 369   case R_PPC_REL14: {
 370     uint32_t mask = 0x0000FFFC;
 371     checkInt(ctx, loc, val, 16, rel);
 372     checkAlignment(ctx, loc, val, 4, rel);
 373     write32(ctx, loc, (read32(ctx, loc) & ~mask) | (val & mask));
 374     break;
 375   }
 376   case R_PPC_ADDR24:
 377   case R_PPC_REL24:
 378   case R_PPC_LOCAL24PC:
 379   case R_PPC_PLTREL24: {
 380     uint32_t mask = 0x03FFFFFC;
 381     checkInt(ctx, loc, val, 26, rel);
 382     checkAlignment(ctx, loc, val, 4, rel);
 383     write32(ctx, loc, (read32(ctx, loc) & ~mask) | (val & mask));
 384     break;
 385   }
 386   default:
 387     llvm_unreachable("unknown relocation");
 388   }
 389 }
 390
 391 RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const {
 392   if (expr == R_RELAX_TLS_GD_TO_IE)
 393     return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
 394   if (expr == R_RELAX_TLS_LD_TO_LE)
 395     return R_RELAX_TLS_LD_TO_LE_ABS;
 396   return expr;
 397 }
 398
 399 int PPC::getTlsGdRelaxSkip(RelType type) const {
 400   // A __tls_get_addr call instruction is marked with 2 relocations:
 401   //
 402   //   R_PPC_TLSGD / R_PPC_TLSLD: marker relocation
 403   //   R_PPC_REL24: __tls_get_addr
 404   //
 405   // After the relaxation we no longer call __tls_get_addr and should skip both
 406   // relocations to not create a false dependence on __tls_get_addr being
 407   // defined.
 408   if (type == R_PPC_TLSGD || type == R_PPC_TLSLD)
 409     return 2;
 410   return 1;
 411 }
 412
 413 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
 414                          uint64_t val) const {
 415   switch (rel.type) {
 416   case R_PPC_GOT_TLSGD16: {
 417     // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA)
 418     uint32_t insn = readFromHalf16(ctx, loc);
 419     writeFromHalf16(ctx, loc, 0x80000000 | (insn & 0x03ff0000));
 420     relocateNoSym(loc, R_PPC_GOT_TPREL16, val);
 421     break;
 422   }
 423   case R_PPC_TLSGD:
 424     // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2
 425     write32(ctx, loc, 0x7c631214);
 426     break;
 427   default:
 428     llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
 429   }
 430 }
 431
 432 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
 433                          uint64_t val) const {
 434   switch (rel.type) {
 435   case R_PPC_GOT_TLSGD16:
 436     // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha
 437     writeFromHalf16(ctx, loc, 0x3c620000 | ha(val));
 438     break;
 439   case R_PPC_TLSGD:
 440     // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l
 441     write32(ctx, loc, 0x38630000 | lo(val));
 442     break;
 443   default:
 444     llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
 445   }
 446 }
 447
 448 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
 449                          uint64_t val) const {
 450   switch (rel.type) {
 451   case R_PPC_GOT_TLSLD16:
 452     // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0
 453     writeFromHalf16(ctx, loc, 0x3c620000);
 454     break;
 455   case R_PPC_TLSLD:
 456     // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel
 457     // = r3+x-0x7000, so add 4096 to r3.
 458     // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096
 459     write32(ctx, loc, 0x38631000);
 460     break;
 461   case R_PPC_DTPREL16:
 462   case R_PPC_DTPREL16_HA:
 463   case R_PPC_DTPREL16_HI:
 464   case R_PPC_DTPREL16_LO:
 465     relocate(loc, rel, val);
 466     break;
 467   default:
 468     llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
 469   }
 470 }
 471
 472 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
 473                          uint64_t val) const {
 474   switch (rel.type) {
 475   case R_PPC_GOT_TPREL16: {
 476     // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha
 477     uint32_t rt = readFromHalf16(ctx, loc) & 0x03e00000;
 478     writeFromHalf16(ctx, loc, 0x3c020000 | rt | ha(val));
 479     break;
 480   }
 481   case R_PPC_TLS: {
 482     uint32_t insn = read32(ctx, loc);
 483     if (insn >> 26 != 31)
 484       ErrAlways(ctx) << "unrecognized instruction for IE to LE R_PPC_TLS";
 485     // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l
 486     unsigned secondaryOp = (read32(ctx, loc) & 0x000007fe) >> 1;
 487     uint32_t dFormOp = getPPCDFormOp(secondaryOp);
 488     if (dFormOp == 0) { // Expecting a DS-Form instruction.
 489       dFormOp = getPPCDSFormOp(secondaryOp);
 490       if (dFormOp == 0)
 491         ErrAlways(ctx) << "unrecognized instruction for IE to LE R_PPC_TLS";
 492     }
 493     write32(ctx, loc, (dFormOp | (insn & 0x03ff0000) | lo(val)));
 494     break;
 495   }
 496   default:
 497     llvm_unreachable("unsupported relocation for TLS IE to LE relaxation");
 498   }
 499 }
 500
 501 void PPC::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
 502   uint64_t secAddr = sec.getOutputSection()->addr;
 503   if (auto *s = dyn_cast<InputSection>(&sec))
 504     secAddr += s->outSecOff;
 505   for (const Relocation &rel : sec.relocs()) {
 506     uint8_t *loc = buf + rel.offset;
 507     const uint64_t val =
 508         SignExtend64(sec.getRelocTargetVA(ctx, rel, secAddr + rel.offset), 32);
 509     switch (rel.expr) {
 510     case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
 511       relaxTlsGdToIe(loc, rel, val);
 512       break;
 513     case R_RELAX_TLS_GD_TO_LE:
 514       relaxTlsGdToLe(loc, rel, val);
 515       break;
 516     case R_RELAX_TLS_LD_TO_LE_ABS:
 517       relaxTlsLdToLe(loc, rel, val);
 518       break;
 519     case R_RELAX_TLS_IE_TO_LE:
 520       relaxTlsIeToLe(loc, rel, val);
 521       break;
 522     default:
 523       relocate(loc, rel, val);
 524       break;
 525     }
 526   }
 527 }
 528
 529 void elf::setPPCTargetInfo(Ctx &ctx) { ctx.target.reset(new PPC(ctx)); }