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   std::lock_guard<std::mutex> Lock(S.M);
  70
  71   auto FileName = sys::path::filename(G.getName());
  72   if (S.FileInfos.count(FileName)) {
  73     return make_error<StringError>("When -check is passed, file names must be "
  74                                    "distinct (duplicate: \"" +
  75                                        FileName + "\")",
  76                                    inconvertibleErrorCode());
  77   }
  78
  79   auto &FileInfo = S.FileInfos[FileName];
  80   LLVM_DEBUG(
  81       { dbgs() << "Registering COFF file info for \"" << FileName << "\"\n"; });
  82   for (auto &Sec : G.sections()) {
  83     LLVM_DEBUG({
  84       dbgs() << "  Section \"" << Sec.getName() << "\": "
  85              << (Sec.symbols().empty() ? "empty. skipping." : "processing...")
  86              << "\n";
  87     });
  88
  89     // Skip empty sections.
  90     if (Sec.symbols().empty())
  91       continue;
  92
  93     if (FileInfo.SectionInfos.count(Sec.getName()))
  94       return make_error<StringError>("Encountered duplicate section name \"" +
  95                                          Sec.getName() + "\" in \"" + FileName +
  96                                          "\"",
  97                                      inconvertibleErrorCode());
  98
  99     bool isGOTSection = isCOFFGOTSection(Sec);
 100     bool isStubsSection = isCOFFStubsSection(Sec);
 101
 102     bool SectionContainsContent = false;
 103     bool SectionContainsZeroFill = false;
 104
 105     auto *FirstSym = *Sec.symbols().begin();
 106     auto *LastSym = FirstSym;
 107     for (auto *Sym : Sec.symbols()) {
 108       if (Sym->getAddress() < FirstSym->getAddress())
 109         FirstSym = Sym;
 110       if (Sym->getAddress() > LastSym->getAddress())
 111         LastSym = Sym;
 112
 113       if (isGOTSection || isStubsSection) {
 114         if (isGOTSection) {
 115           // Skip the GOT start symbol
 116           if (Sym->getSize() != 0)
 117             if (Error E = FileInfo.registerGOTEntry(G, *Sym, getCOFFGOTTarget))
 118               return E;
 119         } else {
 120           if (Error E = FileInfo.registerStubEntry(G, *Sym, getCOFFStubTarget))
 121             return E;
 122         }
 123         SectionContainsContent = true;
 124       }
 125
 126       if (Sym->hasName()) {
 127         if (Sym->isSymbolZeroFill()) {
 128           S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
 129                                            Sym->getAddress().getValue()};
 130           SectionContainsZeroFill = true;
 131         } else {
 132           S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
 133                                            Sym->getAddress().getValue(),
 134                                            Sym->getTargetFlags()};
 135           SectionContainsContent = true;
 136         }
 137       }
 138     }
 139
 140     auto SecAddr = FirstSym->getAddress();
 141     auto SecSize =
 142         (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
 143         SecAddr;
 144
 145     if (SectionContainsZeroFill && SectionContainsContent)
 146       return make_error<StringError>("Mixed zero-fill and content sections not "
 147                                      "supported yet",
 148                                      inconvertibleErrorCode());
 149
 150     if (SectionContainsZeroFill)
 151       FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
 152     else
 153       FileInfo.SectionInfos[Sec.getName()] = {
 154           ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
 155           SecAddr.getValue(), FirstSym->getTargetFlags()};
 156   }
 157
 158   return Error::success();
 159 }
 160
 161 } // end namespace llvm