llvm/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 =
  31       llvm::find_if(B.edges(), [](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   return TargetSym;
  53 }
  54
  55 static Expected<Symbol &> getMachOStubTarget(LinkGraph &G, Block &B) {
  56   auto E = getFirstRelocationEdge(G, B);
  57   if (!E)
  58     return E.takeError();
  59   auto &GOTSym = E->getTarget();
  60   if (!GOTSym.isDefined() || !isMachOGOTSection(GOTSym.getBlock().getSection()))
  61     return make_error<StringError>(
  62         "Stubs entry in " + G.getName() + ", \"" +
  63             GOTSym.getBlock().getSection().getName() +
  64             "\" does not point to GOT entry",
  65         inconvertibleErrorCode());
  66   return getMachOGOTTarget(G, GOTSym.getBlock());
  67 }
  68
  69 namespace llvm {
  70
  71 Error registerMachOGraphInfo(Session &S, LinkGraph &G) {
  72   auto FileName = sys::path::filename(G.getName());
  73   if (S.FileInfos.count(FileName)) {
  74     return make_error<StringError>("When -check is passed, file names must be "
  75                                    "distinct (duplicate: \"" +
  76                                        FileName + "\")",
  77                                    inconvertibleErrorCode());
  78   }
  79
  80   auto &FileInfo = S.FileInfos[FileName];
  81   LLVM_DEBUG({
  82     dbgs() << "Registering MachO file info for \"" << FileName << "\"\n";
  83   });
  84   for (auto &Sec : G.sections()) {
  85     LLVM_DEBUG({
  86       dbgs() << "  Section \"" << Sec.getName() << "\": "
  87              << (Sec.symbols().empty() ? "empty. skipping." : "processing...")
  88              << "\n";
  89     });
  90
  91     // Skip empty sections.
  92     if (Sec.symbols().empty())
  93       continue;
  94
  95     if (FileInfo.SectionInfos.count(Sec.getName()))
  96       return make_error<StringError>("Encountered duplicate section name \"" +
  97                                          Sec.getName() + "\" in \"" + FileName +
  98                                          "\"",
  99                                      inconvertibleErrorCode());
 100
 101     bool isGOTSection = isMachOGOTSection(Sec);
 102     bool isStubsSection = isMachOStubsSection(Sec);
 103
 104     bool SectionContainsContent = false;
 105     bool SectionContainsZeroFill = false;
 106
 107     auto *FirstSym = *Sec.symbols().begin();
 108     auto *LastSym = FirstSym;
 109     for (auto *Sym : Sec.symbols()) {
 110       if (Sym->getAddress() < FirstSym->getAddress())
 111         FirstSym = Sym;
 112       if (Sym->getAddress() > LastSym->getAddress())
 113         LastSym = Sym;
 114       if (isGOTSection || isStubsSection) {
 115         Error Err =
 116             isGOTSection
 117                 ? FileInfo.registerGOTEntry(G, *Sym, getMachOGOTTarget)
 118                 : FileInfo.registerStubEntry(G, *Sym, getMachOStubTarget);
 119         if (Err)
 120           return Err;
 121         SectionContainsContent = true;
 122       } else if (Sym->hasName()) {
 123         if (Sym->isSymbolZeroFill()) {
 124           S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
 125                                            Sym->getAddress().getValue()};
 126           SectionContainsZeroFill = true;
 127         } else {
 128           S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
 129                                            Sym->getAddress().getValue(),
 130                                            Sym->getTargetFlags()};
 131           SectionContainsContent = true;
 132         }
 133       }
 134     }
 135
 136     auto SecAddr = FirstSym->getAddress();
 137     auto SecSize =
 138         (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
 139         SecAddr;
 140
 141     if (SectionContainsZeroFill && SectionContainsContent)
 142       return make_error<StringError>("Mixed zero-fill and content sections not "
 143                                      "supported yet",
 144                                      inconvertibleErrorCode());
 145     if (SectionContainsZeroFill)
 146       FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
 147     else
 148       FileInfo.SectionInfos[Sec.getName()] = {
 149           ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
 150           SecAddr.getValue(), FirstSym->getTargetFlags()};
 151   }
 152
 153   return Error::success();
 154 }
 155
 156 } // end namespace llvm