llvm/lib/ExecutionEngine/Orc/JITLinkRedirectableSymbolManager.cpp

   1 //===-- JITLinkRedirectableSymbolManager.cpp - JITLink redirection in Orc -===//
   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 #include "llvm/ExecutionEngine/Orc/JITLinkRedirectableSymbolManager.h"
  10 #include "llvm/ExecutionEngine/Orc/Core.h"
  11
  12 #define DEBUG_TYPE "orc"
  13
  14 using namespace llvm;
  15 using namespace llvm::orc;
  16
  17 namespace {
  18 constexpr StringRef JumpStubSectionName = "__orc_stubs";
  19 constexpr StringRef StubPtrSectionName = "__orc_stub_ptrs";
  20 constexpr StringRef StubSuffix = "$__stub_ptr";
  21 } // namespace
  22
  23 void JITLinkRedirectableSymbolManager::emitRedirectableSymbols(
  24     std::unique_ptr<MaterializationResponsibility> R, SymbolMap InitialDests) {
  25
  26   auto &ES = ObjLinkingLayer.getExecutionSession();
  27   Triple TT = ES.getTargetTriple();
  28
  29   auto G = std::make_unique<jitlink::LinkGraph>(
  30       ("<indirect stubs graph #" + Twine(++StubGraphIdx) + ">").str(),
  31       ES.getSymbolStringPool(), TT, TT.isArch64Bit() ? 8 : 4,
  32       TT.isLittleEndian() ? endianness::little : endianness::big,
  33       jitlink::getGenericEdgeKindName);
  34   auto &PointerSection =
  35       G->createSection(StubPtrSectionName, MemProt::Write | MemProt::Read);
  36   auto &StubsSection =
  37       G->createSection(JumpStubSectionName, MemProt::Exec | MemProt::Read);
  38
  39   SymbolFlagsMap NewSymbols;
  40   for (auto &[Name, Def] : InitialDests) {
  41     jitlink::Symbol *TargetSym = nullptr;
  42     if (Def.getAddress())
  43       TargetSym = &G->addAbsoluteSymbol(
  44           G->allocateName(*Name + "$__init_tgt"), Def.getAddress(), 0,
  45           jitlink::Linkage::Strong, jitlink::Scope::Local, false);
  46
  47     auto PtrName = ES.intern((*Name + StubSuffix).str());
  48     auto &Ptr = AnonymousPtrCreator(*G, PointerSection, TargetSym, 0);
  49     Ptr.setName(PtrName);
  50     Ptr.setScope(jitlink::Scope::Hidden);
  51     auto &Stub = PtrJumpStubCreator(*G, StubsSection, Ptr);
  52     Stub.setName(Name);
  53     Stub.setScope(jitlink::Scope::Default);
  54     NewSymbols[std::move(PtrName)] = JITSymbolFlags();
  55   }
  56
  57   // Try to claim responsibility for the new stub symbols.
  58   if (auto Err = R->defineMaterializing(std::move(NewSymbols))) {
  59     ES.reportError(std::move(Err));
  60     return R->failMaterialization();
  61   }
  62
  63   ObjLinkingLayer.emit(std::move(R), std::move(G));
  64 }
  65
  66 Error JITLinkRedirectableSymbolManager::redirect(JITDylib &JD,
  67                                                  const SymbolMap &NewDests) {
  68   auto &ES = ObjLinkingLayer.getExecutionSession();
  69   SymbolLookupSet LS;
  70   DenseMap<NonOwningSymbolStringPtr, SymbolStringPtr> PtrToStub;
  71   for (auto &[StubName, Sym] : NewDests) {
  72     auto PtrName = ES.intern((*StubName + StubSuffix).str());
  73     PtrToStub[NonOwningSymbolStringPtr(PtrName)] = StubName;
  74     LS.add(std::move(PtrName));
  75   }
  76   auto PtrSyms =
  77       ES.lookup({{&JD, JITDylibLookupFlags::MatchAllSymbols}}, std::move(LS));
  78   if (!PtrSyms)
  79     return PtrSyms.takeError();
  80
  81   std::vector<tpctypes::PointerWrite> PtrWrites;
  82   for (auto &[PtrName, PtrSym] : *PtrSyms) {
  83     auto DestSymI = NewDests.find(PtrToStub[NonOwningSymbolStringPtr(PtrName)]);
  84     assert(DestSymI != NewDests.end() && "Bad ptr -> stub mapping");
  85     auto &DestSym = DestSymI->second;
  86     PtrWrites.push_back({PtrSym.getAddress(), DestSym.getAddress()});
  87   }
  88
  89   return ObjLinkingLayer.getExecutionSession()
  90       .getExecutorProcessControl()
  91       .getMemoryAccess()
  92       .writePointers(PtrWrites);
  93 }