lld/ELF/Target.cpp

   1 //===- Target.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 // Machine-specific things, such as applying relocations, creation of
  10 // GOT or PLT entries, etc., are handled in this file.
  11 //
  12 // Refer the ELF spec for the single letter variables, S, A or P, used
  13 // in this file.
  14 //
  15 // Some functions defined in this file has "relaxTls" as part of their names.
  16 // They do peephole optimization for TLS variables by rewriting instructions.
  17 // They are not part of the ABI but optional optimization, so you can skip
  18 // them if you are not interested in how TLS variables are optimized.
  19 // See the following paper for the details.
  20 //
  21 //   Ulrich Drepper, ELF Handling For Thread-Local Storage
  22 //   http://www.akkadia.org/drepper/tls.pdf
  23 //
  24 //===----------------------------------------------------------------------===//
  25
  26 #include "Target.h"
  27 #include "InputFiles.h"
  28 #include "OutputSections.h"
  29 #include "SymbolTable.h"
  30 #include "Symbols.h"
  31 #include "SyntheticSections.h"
  32 #include "lld/Common/ErrorHandler.h"
  33 #include "llvm/Object/ELF.h"
  34
  35 using namespace llvm;
  36 using namespace llvm::object;
  37 using namespace llvm::ELF;
  38 using namespace lld;
  39 using namespace lld::elf;
  40
  41 std::string elf::toStr(Ctx &ctx, RelType type) {
  42   StringRef s = getELFRelocationTypeName(ctx.arg.emachine, type);
  43   if (s == "Unknown")
  44     return ("Unknown (" + Twine(type) + ")").str();
  45   return std::string(s);
  46 }
  47
  48 const ELFSyncStream &elf::operator<<(const ELFSyncStream &s, RelType type) {
  49   s << toStr(s.ctx, type);
  50   return s;
  51 }
  52
  53 void elf::setTarget(Ctx &ctx) {
  54   switch (ctx.arg.emachine) {
  55   case EM_386:
  56   case EM_IAMCU:
  57     return setX86TargetInfo(ctx);
  58   case EM_AARCH64:
  59     return setAArch64TargetInfo(ctx);
  60   case EM_AMDGPU:
  61     return setAMDGPUTargetInfo(ctx);
  62   case EM_ARM:
  63     return setARMTargetInfo(ctx);
  64   case EM_AVR:
  65     return setAVRTargetInfo(ctx);
  66   case EM_HEXAGON:
  67     return setHexagonTargetInfo(ctx);
  68   case EM_LOONGARCH:
  69     return setLoongArchTargetInfo(ctx);
  70   case EM_MIPS:
  71     return setMipsTargetInfo(ctx);
  72   case EM_MSP430:
  73     return setMSP430TargetInfo(ctx);
  74   case EM_PPC:
  75     return setPPCTargetInfo(ctx);
  76   case EM_PPC64:
  77     return setPPC64TargetInfo(ctx);
  78   case EM_RISCV:
  79     return setRISCVTargetInfo(ctx);
  80   case EM_SPARCV9:
  81     return setSPARCV9TargetInfo(ctx);
  82   case EM_S390:
  83     return setSystemZTargetInfo(ctx);
  84   case EM_X86_64:
  85     return setX86_64TargetInfo(ctx);
  86   default:
  87     Fatal(ctx) << "unsupported e_machine value: " << Twine(ctx.arg.emachine);
  88   }
  89 }
  90
  91 ErrorPlace elf::getErrorPlace(Ctx &ctx, const uint8_t *loc) {
  92   assert(loc != nullptr);
  93   for (InputSectionBase *d : ctx.inputSections) {
  94     auto *isec = dyn_cast<InputSection>(d);
  95     if (!isec || !isec->getParent() || (isec->type & SHT_NOBITS))
  96       continue;
  97
  98     const uint8_t *isecLoc =
  99         ctx.bufferStart
 100             ? (ctx.bufferStart + isec->getParent()->offset + isec->outSecOff)
 101             : isec->contentMaybeDecompress().data();
 102     if (isecLoc == nullptr) {
 103       assert(isa<SyntheticSection>(isec) && "No data but not synthetic?");
 104       continue;
 105     }
 106     if (isecLoc <= loc && loc < isecLoc + isec->getSize()) {
 107       std::string objLoc = isec->getLocation(loc - isecLoc);
 108       // Return object file location and source file location.
 109       // TODO: Refactor getSrcMsg not to take a variable.
 110       Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);
 111       return {isec, objLoc + ": ",
 112               isec->file ? isec->getSrcMsg(dummy, loc - isecLoc) : ""};
 113     }
 114   }
 115   return {};
 116 }
 117
 118 TargetInfo::~TargetInfo() {}
 119
 120 int64_t TargetInfo::getImplicitAddend(const uint8_t *buf, RelType type) const {
 121   InternalErr(ctx, buf) << "cannot read addend for relocation " << type;
 122   return 0;
 123 }
 124
 125 bool TargetInfo::usesOnlyLowPageBits(RelType type) const { return false; }
 126
 127 bool TargetInfo::needsThunk(RelExpr expr, RelType type, const InputFile *file,
 128                             uint64_t branchAddr, const Symbol &s,
 129                             int64_t a) const {
 130   return false;
 131 }
 132
 133 bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
 134                                                   uint8_t stOther) const {
 135   Err(ctx) << "target doesn't support split stacks";
 136   return false;
 137 }
 138
 139 bool TargetInfo::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
 140   return true;
 141 }
 142
 143 RelExpr TargetInfo::adjustTlsExpr(RelType type, RelExpr expr) const {
 144   return expr;
 145 }
 146
 147 RelExpr TargetInfo::adjustGotPcExpr(RelType type, int64_t addend,
 148                                     const uint8_t *data) const {
 149   return R_GOT_PC;
 150 }
 151
 152 void TargetInfo::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
 153   const unsigned bits = ctx.arg.is64 ? 64 : 32;
 154   uint64_t secAddr = sec.getOutputSection()->addr;
 155   if (auto *s = dyn_cast<InputSection>(&sec))
 156     secAddr += s->outSecOff;
 157   else if (auto *ehIn = dyn_cast<EhInputSection>(&sec))
 158     secAddr += ehIn->getParent()->outSecOff;
 159   for (const Relocation &rel : sec.relocs()) {
 160     uint8_t *loc = buf + rel.offset;
 161     const uint64_t val = SignExtend64(
 162         sec.getRelocTargetVA(ctx, rel, secAddr + rel.offset), bits);
 163     if (rel.expr != R_RELAX_HINT)
 164       relocate(loc, rel, val);
 165   }
 166 }
 167
 168 uint64_t TargetInfo::getImageBase() const {
 169   // Use --image-base if set. Fall back to the target default if not.
 170   if (ctx.arg.imageBase)
 171     return *ctx.arg.imageBase;
 172   return ctx.arg.isPic ? 0 : defaultImageBase;
 173 }