[JITLink] Add initial Aarch64 support

weliveindetail · weliveindetail · commit 2ed91da0f1f3 · 2021-09-03T10:48:06.000+02:00
Set up basic infrastructure for 64-bit ARM architecture support in JITLink. It allows for loading a minimal object file and resolving a single relocation. Advanced features like GOT and PLT handling or relaxations were intentionally left out for the moment. This patch follows the idea to keep implementations for ARM (32-bit) and Aaarch64 (64-bit) separate, because: * it might be easier to share code with the MachO "arm64" JITLink backend * LLVM has individual targets for ARM and Aaarch64 as well Reviewed By: lhames Differential Revision: https://reviews.llvm.org/D108986
diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/ELF_aarch64.h b/llvm/include/llvm/ExecutionEngine/JITLink/ELF_aarch64.h
@@ -0,0 +1,39 @@
+//===--- ELF_aarch64.h - JIT link functions for ELF/aarch64 --*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+//===----------------------------------------------------------------------===//
+//
+// jit-link functions for ELF/aarch64.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_ELF_AARCH64_H
+#define LLVM_EXECUTIONENGINE_JITLINK_ELF_AARCH64_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm {
+namespace jitlink {
+
+/// Create a LinkGraph from an ELF/aarch64 relocatable object
+///
+/// Note: The graph does not take ownership of the underlying buffer, nor copy
+/// its contents. The caller is responsible for ensuring that the object buffer
+/// outlives the graph.
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_aarch64(MemoryBufferRef ObjectBuffer);
+
+/// jit-link the given object buffer, which must be a ELF aarch64 relocatable
+/// object file.
+void link_ELF_aarch64(std::unique_ptr<LinkGraph> G,
+                      std::unique_ptr<JITLinkContext> Ctx);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_ELF_AARCH64_H
diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h b/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
@@ -0,0 +1,38 @@
+//=== aarch64.h - Generic JITLink aarch64 edge kinds, 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 utilities for graphs representing aarch64 objects.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_AARCH64_H
+#define LLVM_EXECUTIONENGINE_JITLINK_AARCH64_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm {
+namespace jitlink {
+namespace aarch64 {
+
+/// Represets aarch64 fixups
+enum EdgeKind_aarch64 : Edge::Kind {
+
+  /// Set a CALL immediate field to bits [27:2] of X = Target - Fixup + Addend
+  R_AARCH64_CALL26 = Edge::FirstRelocation,
+
+};
+
+/// Returns a string name for the given aarch64 edge. For debugging purposes
+/// only
+const char *getEdgeKindName(Edge::Kind K);
+
+} // namespace aarch64
+} // namespace jitlink
+} // namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_AARCH64_H
diff --git a/llvm/lib/ExecutionEngine/JITLink/CMakeLists.txt b/llvm/lib/ExecutionEngine/JITLink/CMakeLists.txt
@@ -13,13 +13,14 @@ add_llvm_component_library(LLVMJITLink
   MachOLinkGraphBuilder.cpp
 
   # ELF
-
   ELF.cpp
   ELFLinkGraphBuilder.cpp
+  ELF_aarch64.cpp
   ELF_riscv.cpp
   ELF_x86_64.cpp
 
   # Architectures:
+  aarch64.cpp
   riscv.cpp
   x86_64.cpp
 
@@ -35,7 +36,7 @@ add_llvm_component_library(LLVMJITLink
   OrcTargetProcess
   Support
   )
- 
+
 target_link_libraries(LLVMJITLink
   PRIVATE
   LLVMObject
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF.cpp
@@ -13,6 +13,7 @@
 #include "llvm/ExecutionEngine/JITLink/ELF.h"
 
 #include "llvm/BinaryFormat/ELF.h"
+#include "llvm/ExecutionEngine/JITLink/ELF_aarch64.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_riscv.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_x86_64.h"
 #include "llvm/Object/ELF.h"
@@ -64,6 +65,8 @@ createLinkGraphFromELFObject(MemoryBufferRef ObjectBuffer) {
     return TargetMachineArch.takeError();
 
   switch (*TargetMachineArch) {
+  case ELF::EM_AARCH64:
+    return createLinkGraphFromELFObject_aarch64(ObjectBuffer);
   case ELF::EM_RISCV:
     return createLinkGraphFromELFObject_riscv(ObjectBuffer);
   case ELF::EM_X86_64:
@@ -78,6 +81,9 @@ createLinkGraphFromELFObject(MemoryBufferRef ObjectBuffer) {
 void link_ELF(std::unique_ptr<LinkGraph> G,
               std::unique_ptr<JITLinkContext> Ctx) {
   switch (G->getTargetTriple().getArch()) {
+  case Triple::aarch64:
+    link_ELF_aarch64(std::move(G), std::move(Ctx));
+    return;
   case Triple::riscv32:
   case Triple::riscv64:
     link_ELF_riscv(std::move(G), std::move(Ctx));
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp
@@ -0,0 +1,220 @@
+//===----- ELF_aarch64.cpp - JIT linker implementation for ELF/aarch64 ----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// ELF/aarch64 jit-link implementation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/ELF_aarch64.h"
+#include "ELFLinkGraphBuilder.h"
+#include "JITLinkGeneric.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/ExecutionEngine/JITLink/aarch64.h"
+#include "llvm/Object/ELFObjectFile.h"
+
+#define DEBUG_TYPE "jitlink"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+
+namespace llvm {
+namespace jitlink {
+
+class ELFJITLinker_aarch64 : public JITLinker<ELFJITLinker_aarch64> {
+  friend class JITLinker<ELFJITLinker_aarch64>;
+
+public:
+  ELFJITLinker_aarch64(std::unique_ptr<JITLinkContext> Ctx,
+                       std::unique_ptr<LinkGraph> G,
+                       PassConfiguration PassConfig)
+      : JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {}
+
+private:
+  Error applyFixup(LinkGraph &G, Block &B, const Edge &E) const {
+    using namespace aarch64;
+    using namespace llvm::support;
+
+    char *BlockWorkingMem = B.getAlreadyMutableContent().data();
+    char *FixupPtr = BlockWorkingMem + E.getOffset();
+    JITTargetAddress FixupAddress = B.getAddress() + E.getOffset();
+    switch (E.getKind()) {
+    case aarch64::R_AARCH64_CALL26: {
+      assert((FixupAddress & 0x3) == 0 && "Call-inst is not 32-bit aligned");
+      int64_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
+
+      if (static_cast<uint64_t>(Value) & 0x3)
+        return make_error<JITLinkError>("Call target is not 32-bit aligned");
+
+      if (!fitsRangeSignedInt<27>(Value))
+        return makeTargetOutOfRangeError(G, B, E);
+
+      uint32_t RawInstr = *(little32_t *)FixupPtr;
+      assert((RawInstr & 0x7fffffff) == 0x14000000 &&
+             "RawInstr isn't a B or BR immediate instruction");
+      uint32_t Imm = (static_cast<uint32_t>(Value) & ((1 << 28) - 1)) >> 2;
+      uint32_t FixedInstr = RawInstr | Imm;
+      *(little32_t *)FixupPtr = FixedInstr;
+      break;
+    }
+    }
+    return Error::success();
+  }
+
+  template <uint8_t Bits> static bool fitsRangeSignedInt(int64_t Value) {
+    return Value >= -(1 << Bits) && Value < (1 << Bits);
+  }
+};
+
+template <typename ELFT>
+class ELFLinkGraphBuilder_aarch64 : public ELFLinkGraphBuilder<ELFT> {
+private:
+  static Expected<aarch64::EdgeKind_aarch64>
+  getRelocationKind(const uint32_t Type) {
+    using namespace aarch64;
+    switch (Type) {
+    case ELF::R_AARCH64_CALL26:
+      return EdgeKind_aarch64::R_AARCH64_CALL26;
+    }
+
+    return make_error<JITLinkError>("Unsupported aarch64 relocation:" +
+                                    formatv("{0:d}", Type));
+  }
+
+  Error addRelocations() override {
+    using Base = ELFLinkGraphBuilder<ELFT>;
+    LLVM_DEBUG(dbgs() << "Adding relocations\n");
+
+    // Iterate sections and only process the interesting ones.
+    for (auto &SecRef : Base::Sections) {
+      if (SecRef.sh_type != ELF::SHT_RELA && SecRef.sh_type != ELF::SHT_REL)
+        continue;
+      auto RelSectName = Base::Obj.getSectionName(SecRef);
+      if (!RelSectName)
+        return RelSectName.takeError();
+
+      LLVM_DEBUG({
+        dbgs() << "Adding relocations from section " << *RelSectName << "\n";
+      });
+
+      auto UpdateSect = Base::Obj.getSection(SecRef.sh_info);
+      if (!UpdateSect)
+        return UpdateSect.takeError();
+
+      auto UpdateSectName = Base::Obj.getSectionName(**UpdateSect);
+      if (!UpdateSectName)
+        return UpdateSectName.takeError();
+
+      // Don't process relocations for debug sections.
+      if (Base::isDwarfSection(*UpdateSectName)) {
+        LLVM_DEBUG({
+          dbgs() << "  Target is dwarf section " << *UpdateSectName
+                 << ". Skipping.\n";
+        });
+        continue;
+      }
+      LLVM_DEBUG(dbgs() << "  For target section " << *UpdateSectName << "\n");
+
+      auto *JITSection = Base::G->findSectionByName(*UpdateSectName);
+      if (!JITSection)
+        return make_error<llvm::StringError>(
+            "Refencing a section that wasn't added to graph" + *UpdateSectName,
+            llvm::inconvertibleErrorCode());
+
+      auto Relocations = Base::Obj.relas(SecRef);
+      if (!Relocations)
+        return Relocations.takeError();
+
+      for (const auto &Rela : *Relocations) {
+        auto Type = Rela.getType(false);
+
+        LLVM_DEBUG({
+          dbgs() << "Relocation Type: " << Type << "\n"
+                 << "Name: " << Base::Obj.getRelocationTypeName(Type) << "\n";
+        });
+
+        auto SymbolIndex = Rela.getSymbol(false);
+        auto Symbol = Base::Obj.getRelocationSymbol(Rela, Base::SymTabSec);
+        if (!Symbol)
+          return Symbol.takeError();
+
+        auto BlockToFix = *(JITSection->blocks().begin());
+        auto *TargetSymbol = Base::getGraphSymbol(SymbolIndex);
+
+        if (!TargetSymbol) {
+          return make_error<llvm::StringError>(
+              "Could not find symbol at given index, did you add it to "
+              "JITSymbolTable? index: " +
+                  std::to_string(SymbolIndex) + ", shndx: " +
+                  std::to_string((*Symbol)->st_shndx) + " Size of table: " +
+                  std::to_string(Base::GraphSymbols.size()),
+              llvm::inconvertibleErrorCode());
+        }
+        int64_t Addend = Rela.r_addend;
+        JITTargetAddress FixupAddress = (*UpdateSect)->sh_addr + Rela.r_offset;
+
+        LLVM_DEBUG({
+          dbgs() << "Processing relocation at "
+                 << format("0x%016" PRIx64, FixupAddress) << "\n";
+        });
+        auto Kind = getRelocationKind(Type);
+        if (!Kind)
+          return Kind.takeError();
+
+        BlockToFix->addEdge(*Kind, FixupAddress - BlockToFix->getAddress(),
+                            *TargetSymbol, Addend);
+      }
+    }
+    return Error::success();
+  }
+
+public:
+  ELFLinkGraphBuilder_aarch64(StringRef FileName,
+                              const object::ELFFile<ELFT> &Obj, const Triple T)
+      : ELFLinkGraphBuilder<ELFT>(Obj, std::move(T), FileName,
+                                  aarch64::getEdgeKindName) {}
+};
+
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_aarch64(MemoryBufferRef ObjectBuffer) {
+  LLVM_DEBUG({
+    dbgs() << "Building jitlink graph for new input "
+           << ObjectBuffer.getBufferIdentifier() << "...\n";
+  });
+
+  auto ELFObj = object::ObjectFile::createELFObjectFile(ObjectBuffer);
+  if (!ELFObj)
+    return ELFObj.takeError();
+
+  assert((*ELFObj)->getArch() == Triple::aarch64 &&
+         "Only AArch64 (little endian) is supported for now");
+
+  auto &ELFObjFile = cast<object::ELFObjectFile<object::ELF64LE>>(**ELFObj);
+  return ELFLinkGraphBuilder_aarch64<object::ELF64LE>((*ELFObj)->getFileName(),
+                                                      ELFObjFile.getELFFile(),
+                                                      (*ELFObj)->makeTriple())
+      .buildGraph();
+}
+
+void link_ELF_aarch64(std::unique_ptr<LinkGraph> G,
+                      std::unique_ptr<JITLinkContext> Ctx) {
+  PassConfiguration Config;
+  const Triple &TT = G->getTargetTriple();
+  if (Ctx->shouldAddDefaultTargetPasses(TT)) {
+    if (auto MarkLive = Ctx->getMarkLivePass(TT))
+      Config.PrePrunePasses.push_back(std::move(MarkLive));
+    else
+      Config.PrePrunePasses.push_back(markAllSymbolsLive);
+  }
+  if (auto Err = Ctx->modifyPassConfig(*G, Config))
+    return Ctx->notifyFailed(std::move(Err));
+
+  ELFJITLinker_aarch64::link(std::move(Ctx), std::move(G), std::move(Config));
+}
+
+} // namespace jitlink
+} // namespace llvm
diff --git a/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp b/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp
@@ -0,0 +1,30 @@
+//===---- aarch64.cpp - Generic JITLink aarch64 edge kinds, utilities -----===//
+//
+// 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 utilities for graphs representing aarch64 objects.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/aarch64.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+namespace jitlink {
+namespace aarch64 {
+
+const char *getEdgeKindName(Edge::Kind K) {
+  switch (K) {
+  case R_AARCH64_CALL26:
+    return "R_AARCH64_CALL26";
+  }
+  return getGenericEdgeKindName(K);
+}
+} // namespace aarch64
+} // namespace jitlink
+} // namespace llvm
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_minimal.s b/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_minimal.s
