llvm/tools/llvm-jitlink/llvm-jitlink-coff.cpp

   1 //===--- llvm-jitlink-coff.cpp -- COFF 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 // COFF 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 isCOFFGOTSection(Section &S) { return S.getName() == "$__GOT"; }
  24
  25 static bool isCOFFStubsSection(Section &S) { return S.getName() == "$__STUBS"; }
  26
  27 static Expected<Edge &> getFirstRelocationEdge(LinkGraph &G, Block &B) {
  28   auto EItr =
  29       llvm::find_if(B.edges(), [](Edge &E) { return E.isRelocation(); });
  30   if (EItr == B.edges().end())
  31     return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
  32                                        B.getSection().getName() +
  33                                        "\" has no relocations",
  34                                    inconvertibleErrorCode());
  35   return *EItr;
  36 }
  37
  38 static Expected<Symbol &> getCOFFGOTTarget(LinkGraph &G, Block &B) {
  39   auto E = getFirstRelocationEdge(G, B);
  40   if (!E)
  41     return E.takeError();
  42   auto &TargetSym = E->getTarget();
  43   if (!TargetSym.hasName())
  44     return make_error<StringError>(
  45         "GOT entry in " + G.getName() + ", \"" +
  46             TargetSym.getBlock().getSection().getName() +
  47             "\" points to anonymous "
  48             "symbol",
  49         inconvertibleErrorCode());
  50   return TargetSym;
  51 }
  52
  53 static Expected<Symbol &> getCOFFStubTarget(LinkGraph &G, Block &B) {
  54   auto E = getFirstRelocationEdge(G, B);
  55   if (!E)
  56     return E.takeError();
  57   auto &GOTSym = E->getTarget();
  58   if (!GOTSym.isDefined() || !isCOFFGOTSection(GOTSym.getBlock().getSection()))
  59     return make_error<StringError>(
  60         "Stubs entry in " + G.getName() + ", \"" +
  61             GOTSym.getBlock().getSection().getName() +
  62             "\" does not point to GOT entry",
  63         inconvertibleErrorCode());
  64   return getCOFFGOTTarget(G, GOTSym.getBlock());
  65 }
  66
  67 namespace llvm {
  68 Error registerCOFFGraphInfo(Session &S, LinkGraph &G) {
  69   auto FileName = sys::path::filename(G.getName());
  70   if (S.FileInfos.count(FileName)) {
  71     return make_error<StringError>("When -check is passed, file names must be "
  72                                    "distinct (duplicate: \"" +
  73                                        FileName + "\")",
  74                                    inconvertibleErrorCode());
  75   }
  76
  77   auto &FileInfo = S.FileInfos[FileName];
  78   LLVM_DEBUG(
  79       { dbgs() << "Registering COFF file info for \"" << FileName << "\"\n"; });
  80   for (auto &Sec : G.sections()) {
  81     LLVM_DEBUG({
  82       dbgs() << "  Section \"" << Sec.getName() << "\": "
  83              << (Sec.symbols().empty() ? "empty. skipping." : "processing...")
  84              << "\n";
  85     });
  86
  87     // Skip empty sections.
  88     if (Sec.symbols().empty())
  89       continue;
  90
  91     if (FileInfo.SectionInfos.count(Sec.getName()))
  92       return make_error<StringError>("Encountered duplicate section name \"" +
  93                                          Sec.getName() + "\" in \"" + FileName +
  94                                          "\"",
  95                                      inconvertibleErrorCode());
  96
  97     bool isGOTSection = isCOFFGOTSection(Sec);
  98     bool isStubsSection = isCOFFStubsSection(Sec);
  99
 100     bool SectionContainsContent = false;
 101     bool SectionContainsZeroFill = false;
 102
 103     auto *FirstSym = *Sec.symbols().begin();
 104     auto *LastSym = FirstSym;
 105     for (auto *Sym : Sec.symbols()) {
 106       if (Sym->getAddress() < FirstSym->getAddress())
 107         FirstSym = Sym;
 108       if (Sym->getAddress() > LastSym->getAddress())
 109         LastSym = Sym;
 110
 111       if (isGOTSection || isStubsSection) {
 112         if (isGOTSection) {
 113           // Skip the GOT start symbol
 114           if (Sym->getSize() != 0)
 115             if (Error E = FileInfo.registerGOTEntry(G, *Sym, getCOFFGOTTarget))
 116               return E;
 117         } else {
 118           if (Error E = FileInfo.registerStubEntry(G, *Sym, getCOFFStubTarget))
 119             return E;
 120         }
 121         SectionContainsContent = true;
 122       }
 123
 124       if (Sym->hasName()) {
 125         if (Sym->isSymbolZeroFill()) {
 126           S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
 127                                            Sym->getAddress().getValue()};
 128           SectionContainsZeroFill = true;
 129         } else {
 130           S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
 131                                            Sym->getAddress().getValue(),
 132                                            Sym->getTargetFlags()};
 133           SectionContainsContent = true;
 134         }
 135       }
 136     }
 137
 138     auto SecAddr = FirstSym->getAddress();
 139     auto SecSize =
 140         (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
 141         SecAddr;
 142
 143     if (SectionContainsZeroFill && SectionContainsContent)
 144       return make_error<StringError>("Mixed zero-fill and content sections not "
 145                                      "supported yet",
 146                                      inconvertibleErrorCode());
 147
 148     if (SectionContainsZeroFill)
 149       FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
 150     else
 151       FileInfo.SectionInfos[Sec.getName()] = {
 152           ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
 153           SecAddr.getValue(), FirstSym->getTargetFlags()};
 154   }
 155
 156   return Error::success();
 157 }
 158
 159 } // end namespace llvm