tools/llvm-jitlink/llvm-jitlink-macho.cpp

   1 //===-- llvm-jitlink-macho.cpp -- MachO parsing support for llvm-jitlink --===//
   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 // MachO parsing support for llvm-jitlink.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm-jitlink.h"
  14
  15 #include "llvm/Support/Error.h"
  16 #include "llvm/Support/Path.h"
  17
  18 #define DEBUG_TYPE "llvm-jitlink"
  19
  20 using namespace llvm;
  21 using namespace llvm::jitlink;
  22
  23 static bool isMachOGOTSection(Section &S) { return S.getName() == "$__GOT"; }
  24
  25 static bool isMachOStubsSection(Section &S) {
  26   return S.getName() == "$__STUBS";
  27 }
  28
  29 static Expected<Edge &> getFirstRelocationEdge(LinkGraph &G, Block &B) {
  30   auto EItr = std::find_if(B.edges().begin(), B.edges().end(),
  31                            [](Edge &E) { return E.isRelocation(); });
  32   if (EItr == B.edges().end())
  33     return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
  34                                        B.getSection().getName() +
  35                                        "\" has no relocations",
  36                                    inconvertibleErrorCode());
  37   return *EItr;
  38 }
  39
  40 static Expected<Symbol &> getMachOGOTTarget(LinkGraph &G, Block &B) {
  41   auto E = getFirstRelocationEdge(G, B);
  42   if (!E)
  43     return E.takeError();
  44   auto &TargetSym = E->getTarget();
  45   if (!TargetSym.hasName())
  46     return make_error<StringError>(
  47         "GOT entry in " + G.getName() + ", \"" +
  48             TargetSym.getBlock().getSection().getName() +
  49             "\" points to anonymous "
  50             "symbol",
  51         inconvertibleErrorCode());
  52   if (TargetSym.isDefined() || TargetSym.isAbsolute())
  53     return make_error<StringError>(
  54         "GOT entry \"" + TargetSym.getName() + "\" in " + G.getName() + ", \"" +
  55             TargetSym.getBlock().getSection().getName() +
  56             "\" does not point to an external symbol",
  57         inconvertibleErrorCode());
  58   return TargetSym;
  59 }
  60
  61 static Expected<Symbol &> getMachOStubTarget(LinkGraph &G, Block &B) {
  62   auto E = getFirstRelocationEdge(G, B);
  63   if (!E)
  64     return E.takeError();
  65   auto &GOTSym = E->getTarget();
  66   if (!GOTSym.isDefined() || !isMachOGOTSection(GOTSym.getBlock().getSection()))
  67     return make_error<StringError>(
  68         "Stubs entry in " + G.getName() + ", \"" +
  69             GOTSym.getBlock().getSection().getName() +
  70             "\" does not point to GOT entry",
  71         inconvertibleErrorCode());
  72   return getMachOGOTTarget(G, GOTSym.getBlock());
  73 }
  74
  75 namespace llvm {
  76
  77 Error registerMachOStubsAndGOT(Session &S, LinkGraph &G) {
  78   auto FileName = sys::path::filename(G.getName());
  79   if (S.FileInfos.count(FileName)) {
  80     return make_error<StringError>("When -check is passed, file names must be "
  81                                    "distinct (duplicate: \"" +
  82                                        FileName + "\")",
  83                                    inconvertibleErrorCode());
  84   }
  85
  86   auto &FileInfo = S.FileInfos[FileName];
  87   LLVM_DEBUG({
  88     dbgs() << "Registering MachO file info for \"" << FileName << "\"\n";
  89   });
  90   for (auto &Sec : G.sections()) {
  91     LLVM_DEBUG({
  92       dbgs() << "  Section \"" << Sec.getName() << "\": "
  93              << (Sec.symbols_empty() ? "empty. skipping." : "processing...")
  94              << "\n";
  95     });
  96
  97     // Skip empty sections.
  98     if (Sec.symbols_empty())
  99       continue;
 100
 101     if (FileInfo.SectionInfos.count(Sec.getName()))
 102       return make_error<StringError>("Encountered duplicate section name \"" +
 103                                          Sec.getName() + "\" in \"" + FileName +
 104                                          "\"",
 105                                      inconvertibleErrorCode());
 106
 107     bool isGOTSection = isMachOGOTSection(Sec);
 108     bool isStubsSection = isMachOStubsSection(Sec);
 109
 110     bool SectionContainsContent = false;
 111     bool SectionContainsZeroFill = false;
 112
 113     auto *FirstSym = *Sec.symbols().begin();
 114     auto *LastSym = FirstSym;
 115     for (auto *Sym : Sec.symbols()) {
 116       if (Sym->getAddress() < FirstSym->getAddress())
 117         FirstSym = Sym;
 118       if (Sym->getAddress() > LastSym->getAddress())
 119         LastSym = Sym;
 120       if (isGOTSection) {
 121         if (Sym->isSymbolZeroFill())
 122           return make_error<StringError>("zero-fill atom in GOT section",
 123                                          inconvertibleErrorCode());
 124
 125         if (auto TS = getMachOGOTTarget(G, Sym->getBlock()))
 126           FileInfo.GOTEntryInfos[TS->getName()] = {Sym->getSymbolContent(),
 127                                                    Sym->getAddress()};
 128         else
 129           return TS.takeError();
 130         SectionContainsContent = true;
 131       } else if (isStubsSection) {
 132         if (Sym->isSymbolZeroFill())
 133           return make_error<StringError>("zero-fill atom in Stub section",
 134                                          inconvertibleErrorCode());
 135
 136         if (auto TS = getMachOStubTarget(G, Sym->getBlock()))
 137           FileInfo.StubInfos[TS->getName()] = {Sym->getSymbolContent(),
 138                                                Sym->getAddress()};
 139         else
 140           return TS.takeError();
 141         SectionContainsContent = true;
 142       } else if (Sym->hasName()) {
 143         if (Sym->isSymbolZeroFill()) {
 144           S.SymbolInfos[Sym->getName()] = {Sym->getSize(), Sym->getAddress()};
 145           SectionContainsZeroFill = true;
 146         } else {
 147           S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
 148                                            Sym->getAddress()};
 149           SectionContainsContent = true;
 150         }
 151       }
 152     }
 153
 154     JITTargetAddress SecAddr = FirstSym->getAddress();
 155     uint64_t SecSize =
 156         (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
 157         SecAddr;
 158
 159     if (SectionContainsZeroFill && SectionContainsContent)
 160       return make_error<StringError>("Mixed zero-fill and content sections not "
 161                                      "supported yet",
 162                                      inconvertibleErrorCode());
 163     if (SectionContainsZeroFill)
 164       FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr};
 165     else
 166       FileInfo.SectionInfos[Sec.getName()] = {
 167           StringRef(FirstSym->getBlock().getContent().data(), SecSize),
 168           SecAddr};
 169   }
 170
 171   return Error::success();
 172 }
 173
 174 } // end namespace llvm