lib/ExecutionEngine/JITLink/JITLinkGeneric.h - llvm - Git at Google

 //===------ JITLinkGeneric.h - Generic JIT linker utilities -----*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Generic JITLinker utilities. E.g. graph pruning, eh-frame parsing.
 //
 //===----------------------------------------------------------------------===//

 #ifndef LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
 #define LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H

 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ExecutionEngine/JITLink/JITLink.h"

 #define DEBUG_TYPE "jitlink"

 namespace llvm {

 class MemoryBufferRef;

 namespace jitlink {

 /// Base class for a JIT linker.
 ///
 /// A JITLinkerBase instance links one object file into an ongoing JIT
 /// session. Symbol resolution and finalization operations are pluggable,
 /// and called using continuation passing (passing a continuation for the
 /// remaining linker work) to allow them to be performed asynchronously.
 class JITLinkerBase {
 public:
   JITLinkerBase(std::unique_ptr<JITLinkContext> Ctx, PassConfiguration Passes)
       : Ctx(std::move(Ctx)), Passes(std::move(Passes)) {
     assert(this->Ctx && "Ctx can not be null");
   }

   virtual ~JITLinkerBase();

 protected:
   struct SegmentLayout {
     using SectionAtomsList = std::vector<DefinedAtom *>;
     struct SectionLayout {
       SectionLayout(Section &S) : S(&S) {}

       Section *S;
       SectionAtomsList Atoms;
     };

     using SectionLayoutList = std::vector<SectionLayout>;

     SectionLayoutList ContentSections;
     SectionLayoutList ZeroFillSections;
   };

   using SegmentLayoutMap = DenseMap<unsigned, SegmentLayout>;

   // Phase 1:
   //   1.1: Build atom graph
   //   1.2: Run pre-prune passes
   //   1.2: Prune graph
   //   1.3: Run post-prune passes
   //   1.4: Sort atoms into segments
   //   1.5: Allocate segment memory
   //   1.6: Identify externals and make an async call to resolve function
   void linkPhase1(std::unique_ptr<JITLinkerBase> Self);

   // Phase 2:
   //   2.1: Apply resolution results
   //   2.2: Fix up atom contents
   //   2.3: Call OnResolved callback
   //   2.3: Make an async call to transfer and finalize memory.
   void linkPhase2(std::unique_ptr<JITLinkerBase> Self,
                   Expected<AsyncLookupResult> LookupResult);

   // Phase 3:
   //   3.1: Call OnFinalized callback, handing off allocation.
   void linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err);

   // Build a graph from the given object buffer.
   // To be implemented by the client.
   virtual Expected<std::unique_ptr<AtomGraph>>
   buildGraph(MemoryBufferRef ObjBuffer) = 0;

   // For debug dumping of the atom graph.
   virtual StringRef getEdgeKindName(Edge::Kind K) const = 0;

 private:
   // Run all passes in the given pass list, bailing out immediately if any pass
   // returns an error.
   Error runPasses(AtomGraphPassList &Passes, AtomGraph &G);

   // Copy atom contents and apply relocations.
   // Implemented in JITLinker.
   virtual Error
   copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
                        JITLinkMemoryManager::Allocation &Alloc) const = 0;

   void layOutAtoms();
   Error allocateSegments(const SegmentLayoutMap &Layout);
   DenseSet<StringRef> getExternalSymbolNames() const;
   void applyLookupResult(AsyncLookupResult LR);

   void dumpGraph(raw_ostream &OS);

   std::unique_ptr<JITLinkContext> Ctx;
   PassConfiguration Passes;
   std::unique_ptr<AtomGraph> G;
   SegmentLayoutMap Layout;
   std::unique_ptr<JITLinkMemoryManager::Allocation> Alloc;
 };

 template <typename LinkerImpl> class JITLinker : public JITLinkerBase {
 public:
   using JITLinkerBase::JITLinkerBase;

   /// Link constructs a LinkerImpl instance and calls linkPhase1.
   /// Link should be called with the constructor arguments for LinkerImpl, which
   /// will be forwarded to the constructor.
   template <typename... ArgTs> static void link(ArgTs &&... Args) {
     auto L = llvm::make_unique<LinkerImpl>(std::forward<ArgTs>(Args)...);

     // Ownership of the linker is passed into the linker's doLink function to
     // allow it to be passed on to async continuations.
     //
     // FIXME: Remove LTmp once we have c++17.
     // C++17 sequencing rules guarantee that function name expressions are
     // sequenced before arguments, so L->linkPhase1(std::move(L), ...) will be
     // well formed.
     auto &LTmp = *L;
     LTmp.linkPhase1(std::move(L));
   }

 private:
   const LinkerImpl &impl() const {
     return static_cast<const LinkerImpl &>(*this);
   }

   Error
   copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
                        JITLinkMemoryManager::Allocation &Alloc) const override {
     LLVM_DEBUG(dbgs() << "Copying and fixing up atoms:\n");
     for (auto &KV : Layout) {
       auto &Prot = KV.first;
       auto &SegLayout = KV.second;

       auto SegMem = Alloc.getWorkingMemory(
           static_cast<sys::Memory::ProtectionFlags>(Prot));
       char *LastAtomEnd = SegMem.data();
       char *AtomDataPtr = nullptr;

       LLVM_DEBUG({
         dbgs() << "  Processing segment "
                << static_cast<sys::Memory::ProtectionFlags>(Prot) << " [ "
                << (const void *)SegMem.data() << " .. "
                << (const void *)((char *)SegMem.data() + SegMem.size())
                << " ]\n    Processing content sections:\n";
       });

       for (auto &SI : SegLayout.ContentSections) {
         LLVM_DEBUG(dbgs() << "    " << SI.S->getName() << ":\n");
         for (auto *DA : SI.Atoms) {
           AtomDataPtr = LastAtomEnd;

           // Align.
           AtomDataPtr += alignmentAdjustment(AtomDataPtr, DA->getAlignment());
           LLVM_DEBUG({
             dbgs() << "      Bumped atom pointer to "
                    << (const void *)AtomDataPtr << " to meet alignment of "
                    << DA->getAlignment() << "\n";
           });

           // Zero pad up to alignment.
           LLVM_DEBUG({
             if (LastAtomEnd != AtomDataPtr)
               dbgs() << "      Zero padding from " << (const void *)LastAtomEnd
                      << " to " << (const void *)AtomDataPtr << "\n";
           });
           while (LastAtomEnd != AtomDataPtr)
             *LastAtomEnd++ = 0;

           // Copy initial atom content.
           LLVM_DEBUG({
             dbgs() << "      Copying atom " << *DA << " content, "
                    << DA->getContent().size() << " bytes, from "
                    << (const void *)DA->getContent().data() << " to "
                    << (const void *)AtomDataPtr << "\n";
           });
           memcpy(AtomDataPtr, DA->getContent().data(), DA->getContent().size());

           // Copy atom data and apply fixups.
           LLVM_DEBUG(dbgs() << "      Applying fixups.\n");
           for (auto &E : DA->edges()) {

             // Skip non-relocation edges.
             if (!E.isRelocation())
               continue;

             // Dispatch to LinkerImpl for fixup.
             if (auto Err = impl().applyFixup(*DA, E, AtomDataPtr))
               return Err;
           }

           // Point the atom's content to the fixed up buffer.
           DA->setContent(StringRef(AtomDataPtr, DA->getContent().size()));

           // Update atom end pointer.
           LastAtomEnd = AtomDataPtr + DA->getContent().size();
         }
       }

       // Zero pad the rest of the segment.
       LLVM_DEBUG({
         dbgs() << "    Zero padding end of segment from "
                << (const void *)LastAtomEnd << " to "
                << (const void *)((char *)SegMem.data() + SegMem.size()) << "\n";
       });
       while (LastAtomEnd != SegMem.data() + SegMem.size())
         *LastAtomEnd++ = 0;
     }

     return Error::success();
   }
 };

 /// Dead strips and replaces discarded definitions with external atoms.
 ///
 /// Finds the set of nodes reachable from any node initially marked live
 /// (nodes marked should-discard are treated as not live, even if they are
 /// reachable). All nodes not marked as live at the end of this process,
 /// are deleted. Nodes that are live, but marked should-discard are replaced
 /// with external atoms and all edges to them are re-written.
 void prune(AtomGraph &G);

 Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
                  StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
                  Edge::Kind FDEToCIERelocKind, Edge::Kind FDEToTargetRelocKind);

 } // end namespace jitlink
 } // end namespace llvm

 #undef DEBUG_TYPE // "jitlink"

 #endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
	//===------ JITLinkGeneric.h - Generic JIT linker utilities ------ C++ --===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	// Generic JITLinker utilities. E.g. graph pruning, eh-frame parsing.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
	#define LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H

	#include "llvm/ADT/DenseSet.h"
	#include "llvm/ExecutionEngine/JITLink/JITLink.h"

	#define DEBUG_TYPE "jitlink"

	namespace llvm {

	class MemoryBufferRef;

	namespace jitlink {

	/// Base class for a JIT linker.
	///
	/// A JITLinkerBase instance links one object file into an ongoing JIT
	/// session. Symbol resolution and finalization operations are pluggable,
	/// and called using continuation passing (passing a continuation for the
	/// remaining linker work) to allow them to be performed asynchronously.
	class JITLinkerBase {
	public:
	JITLinkerBase(std::unique_ptr<JITLinkContext> Ctx, PassConfiguration Passes)
	: Ctx(std::move(Ctx)), Passes(std::move(Passes)) {
	assert(this->Ctx && "Ctx can not be null");
	}

	virtual ~JITLinkerBase();

	protected:
	struct SegmentLayout {
	using SectionAtomsList = std::vector<DefinedAtom *>;
	struct SectionLayout {
	SectionLayout(Section &S) : S(&S) {}

	Section *S;
	SectionAtomsList Atoms;
	};

	using SectionLayoutList = std::vector<SectionLayout>;

	SectionLayoutList ContentSections;
	SectionLayoutList ZeroFillSections;
	};

	using SegmentLayoutMap = DenseMap<unsigned, SegmentLayout>;

	// Phase 1:
	// 1.1: Build atom graph
	// 1.2: Run pre-prune passes
	// 1.2: Prune graph
	// 1.3: Run post-prune passes
	// 1.4: Sort atoms into segments
	// 1.5: Allocate segment memory
	// 1.6: Identify externals and make an async call to resolve function
	void linkPhase1(std::unique_ptr<JITLinkerBase> Self);

	// Phase 2:
	// 2.1: Apply resolution results
	// 2.2: Fix up atom contents
	// 2.3: Call OnResolved callback
	// 2.3: Make an async call to transfer and finalize memory.
	void linkPhase2(std::unique_ptr<JITLinkerBase> Self,
	Expected<AsyncLookupResult> LookupResult);

	// Phase 3:
	// 3.1: Call OnFinalized callback, handing off allocation.
	void linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err);

	// Build a graph from the given object buffer.
	// To be implemented by the client.
	virtual Expected<std::unique_ptr<AtomGraph>>
	buildGraph(MemoryBufferRef ObjBuffer) = 0;

	// For debug dumping of the atom graph.
	virtual StringRef getEdgeKindName(Edge::Kind K) const = 0;

	private:
	// Run all passes in the given pass list, bailing out immediately if any pass
	// returns an error.
	Error runPasses(AtomGraphPassList &Passes, AtomGraph &G);

	// Copy atom contents and apply relocations.
	// Implemented in JITLinker.
	virtual Error
	copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
	JITLinkMemoryManager::Allocation &Alloc) const = 0;

	void layOutAtoms();
	Error allocateSegments(const SegmentLayoutMap &Layout);
	DenseSet<StringRef> getExternalSymbolNames() const;
	void applyLookupResult(AsyncLookupResult LR);

	void dumpGraph(raw_ostream &OS);

	std::unique_ptr<JITLinkContext> Ctx;
	PassConfiguration Passes;
	std::unique_ptr<AtomGraph> G;
	SegmentLayoutMap Layout;
	std::unique_ptr<JITLinkMemoryManager::Allocation> Alloc;
	};

	template <typename LinkerImpl> class JITLinker : public JITLinkerBase {
	public:
	using JITLinkerBase::JITLinkerBase;

	/// Link constructs a LinkerImpl instance and calls linkPhase1.
	/// Link should be called with the constructor arguments for LinkerImpl, which
	/// will be forwarded to the constructor.
	template <typename... ArgTs> static void link(ArgTs &&... Args) {
	auto L = llvm::make_unique<LinkerImpl>(std::forward<ArgTs>(Args)...);

	// Ownership of the linker is passed into the linker's doLink function to
	// allow it to be passed on to async continuations.
	//
	// FIXME: Remove LTmp once we have c++17.
	// C++17 sequencing rules guarantee that function name expressions are
	// sequenced before arguments, so L->linkPhase1(std::move(L), ...) will be
	// well formed.
	auto &LTmp = *L;
	LTmp.linkPhase1(std::move(L));
	}

	private:
	const LinkerImpl &impl() const {
	return static_cast<const LinkerImpl &>(*this);
	}

	Error
	copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
	JITLinkMemoryManager::Allocation &Alloc) const override {
	LLVM_DEBUG(dbgs() << "Copying and fixing up atoms:\n");
	for (auto &KV : Layout) {
	auto &Prot = KV.first;
	auto &SegLayout = KV.second;

	auto SegMem = Alloc.getWorkingMemory(
	static_cast<sys::Memory::ProtectionFlags>(Prot));
	char *LastAtomEnd = SegMem.data();
	char *AtomDataPtr = nullptr;

	LLVM_DEBUG({
	dbgs() << " Processing segment "
	<< static_cast<sys::Memory::ProtectionFlags>(Prot) << " [ "
	<< (const void *)SegMem.data() << " .. "
	<< (const void )((char )SegMem.data() + SegMem.size())
	<< " ]\n Processing content sections:\n";
	});

	for (auto &SI : SegLayout.ContentSections) {
	LLVM_DEBUG(dbgs() << " " << SI.S->getName() << ":\n");
	for (auto *DA : SI.Atoms) {
	AtomDataPtr = LastAtomEnd;

	// Align.
	AtomDataPtr += alignmentAdjustment(AtomDataPtr, DA->getAlignment());
	LLVM_DEBUG({
	dbgs() << " Bumped atom pointer to "
	<< (const void *)AtomDataPtr << " to meet alignment of "
	<< DA->getAlignment() << "\n";
	});

	// Zero pad up to alignment.
	LLVM_DEBUG({
	if (LastAtomEnd != AtomDataPtr)
	dbgs() << " Zero padding from " << (const void *)LastAtomEnd
	<< " to " << (const void *)AtomDataPtr << "\n";
	});
	while (LastAtomEnd != AtomDataPtr)
	*LastAtomEnd++ = 0;

	// Copy initial atom content.
	LLVM_DEBUG({
	dbgs() << " Copying atom " << *DA << " content, "
	<< DA->getContent().size() << " bytes, from "
	<< (const void *)DA->getContent().data() << " to "
	<< (const void *)AtomDataPtr << "\n";
	});
	memcpy(AtomDataPtr, DA->getContent().data(), DA->getContent().size());

	// Copy atom data and apply fixups.
	LLVM_DEBUG(dbgs() << " Applying fixups.\n");
	for (auto &E : DA->edges()) {

	// Skip non-relocation edges.
	if (!E.isRelocation())
	continue;

	// Dispatch to LinkerImpl for fixup.
	if (auto Err = impl().applyFixup(*DA, E, AtomDataPtr))
	return Err;
	}

	// Point the atom's content to the fixed up buffer.
	DA->setContent(StringRef(AtomDataPtr, DA->getContent().size()));

	// Update atom end pointer.
	LastAtomEnd = AtomDataPtr + DA->getContent().size();
	}
	}

	// Zero pad the rest of the segment.
	LLVM_DEBUG({
	dbgs() << " Zero padding end of segment from "
	<< (const void *)LastAtomEnd << " to "
	<< (const void )((char )SegMem.data() + SegMem.size()) << "\n";
	});
	while (LastAtomEnd != SegMem.data() + SegMem.size())
	*LastAtomEnd++ = 0;
	}

	return Error::success();
	}
	};

	/// Dead strips and replaces discarded definitions with external atoms.
	///
	/// Finds the set of nodes reachable from any node initially marked live
	/// (nodes marked should-discard are treated as not live, even if they are
	/// reachable). All nodes not marked as live at the end of this process,
	/// are deleted. Nodes that are live, but marked should-discard are replaced
	/// with external atoms and all edges to them are re-written.
	void prune(AtomGraph &G);

	Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
	StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
	Edge::Kind FDEToCIERelocKind, Edge::Kind FDEToTargetRelocKind);

	} // end namespace jitlink
	} // end namespace llvm

	#undef DEBUG_TYPE // "jitlink"

	#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H