1 files changed, 267 insertions, 0 deletions
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
new file mode 100644
index 000000000000..1fee38821a49
--- /dev/null
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -0,0 +1,267 @@
+//===-- ARMELFObjectWriter.cpp - ARM ELF Writer ---------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/ARMFixupKinds.h"
+#include "MCTargetDesc/ARMMCTargetDesc.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELFObjectWriter.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstdint>
+
+using namespace llvm;
+
+namespace {
+
+  class ARMELFObjectWriter : public MCELFObjectTargetWriter {
+    enum { DefaultEABIVersion = 0x05000000U };
+
+    unsigned GetRelocTypeInner(const MCValue &Target, const MCFixup &Fixup,
+                               bool IsPCRel, MCContext &Ctx) const;
+
+  public:
+    ARMELFObjectWriter(uint8_t OSABI);
+
+    ~ARMELFObjectWriter() override = default;
+
+    unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                          const MCFixup &Fixup, bool IsPCRel) const override;
+
+    bool needsRelocateWithSymbol(const MCSymbol &Sym,
+                                 unsigned Type) const override;
+
+    void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec) override;
+  };
+
+} // end anonymous namespace
+
+ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
+  : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
+                            ELF::EM_ARM,
+                            /*HasRelocationAddend*/ false) {}
+
+bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
+                                                 unsigned Type) const {
+  // FIXME: This is extremely conservative. This really needs to use a
+  // whitelist with a clear explanation for why each realocation needs to
+  // point to the symbol, not to the section.
+  switch (Type) {
+  default:
+    return true;
+
+  case ELF::R_ARM_PREL31:
+  case ELF::R_ARM_ABS32:
+    return false;
+  }
+}
+
+// Need to examine the Fixup when determining whether to
+// emit the relocation as an explicit symbol or as a section relative
+// offset
+unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
+                                          const MCFixup &Fixup,
+                                          bool IsPCRel) const {
+  return GetRelocTypeInner(Target, Fixup, IsPCRel, Ctx);
+}
+
+unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
+                                               const MCFixup &Fixup,
+                                               bool IsPCRel,
+                                               MCContext &Ctx) const {
+  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
+
+  if (IsPCRel) {
+    switch (Fixup.getTargetKind()) {
+    default:
+      Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol");
+      return ELF::R_ARM_NONE;
+    case FK_Data_4:
+      switch (Modifier) {
+      default:
+        llvm_unreachable("Unsupported Modifier");
+      case MCSymbolRefExpr::VK_None:
+        return ELF::R_ARM_REL32;
+      case MCSymbolRefExpr::VK_GOTTPOFF:
+        return ELF::R_ARM_TLS_IE32;
+      case MCSymbolRefExpr::VK_ARM_GOT_PREL:
+        return ELF::R_ARM_GOT_PREL;
+      case MCSymbolRefExpr::VK_ARM_PREL31:
+        return ELF::R_ARM_PREL31;
+      }
+    case ARM::fixup_arm_blx:
+    case ARM::fixup_arm_uncondbl:
+      switch (Modifier) {
+      case MCSymbolRefExpr::VK_PLT:
+        return ELF::R_ARM_CALL;
+      case MCSymbolRefExpr::VK_TLSCALL:
+        return ELF::R_ARM_TLS_CALL;
+      default:
+        return ELF::R_ARM_CALL;
+      }
+    case ARM::fixup_arm_condbl:
+    case ARM::fixup_arm_condbranch:
+    case ARM::fixup_arm_uncondbranch:
+      return ELF::R_ARM_JUMP24;
+    case ARM::fixup_t2_condbranch:
+      return ELF::R_ARM_THM_JUMP19;
+    case ARM::fixup_t2_uncondbranch:
+      return ELF::R_ARM_THM_JUMP24;
+    case ARM::fixup_arm_movt_hi16:
+      return ELF::R_ARM_MOVT_PREL;
+    case ARM::fixup_arm_movw_lo16:
+      return ELF::R_ARM_MOVW_PREL_NC;
+    case ARM::fixup_t2_movt_hi16:
+      return ELF::R_ARM_THM_MOVT_PREL;
+    case ARM::fixup_t2_movw_lo16:
+      return ELF::R_ARM_THM_MOVW_PREL_NC;
+    case ARM::fixup_arm_thumb_br:
+      return ELF::R_ARM_THM_JUMP11;
+    case ARM::fixup_arm_thumb_bcc:
+      return ELF::R_ARM_THM_JUMP8;
+    case ARM::fixup_arm_thumb_bl:
+    case ARM::fixup_arm_thumb_blx:
+      switch (Modifier) {
+      case MCSymbolRefExpr::VK_TLSCALL:
+        return ELF::R_ARM_THM_TLS_CALL;
+      default:
+        return ELF::R_ARM_THM_CALL;
+      }
+    case ARM::fixup_bf_target:
+      return ELF::R_ARM_THM_BF16;
+    case ARM::fixup_bfc_target:
+      return ELF::R_ARM_THM_BF12;
+    case ARM::fixup_bfl_target:
+      return ELF::R_ARM_THM_BF18;
+    }
+  }
+  switch (Fixup.getTargetKind()) {
+  default:
+    Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol");
+    return ELF::R_ARM_NONE;
+  case FK_NONE:
+    return ELF::R_ARM_NONE;
+  case FK_Data_1:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_ABS8;
+    }
+  case FK_Data_2:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("unsupported modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_ABS16;
+    }
+  case FK_Data_4:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_ARM_NONE:
+      return ELF::R_ARM_NONE;
+    case MCSymbolRefExpr::VK_GOT:
+      return ELF::R_ARM_GOT_BREL;
+    case MCSymbolRefExpr::VK_TLSGD:
+      return ELF::R_ARM_TLS_GD32;
+    case MCSymbolRefExpr::VK_TPOFF:
+      return ELF::R_ARM_TLS_LE32;
+    case MCSymbolRefExpr::VK_GOTTPOFF:
+      return ELF::R_ARM_TLS_IE32;
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_ABS32;
+    case MCSymbolRefExpr::VK_GOTOFF:
+      return ELF::R_ARM_GOTOFF32;
+    case MCSymbolRefExpr::VK_ARM_GOT_PREL:
+      return ELF::R_ARM_GOT_PREL;
+    case MCSymbolRefExpr::VK_ARM_TARGET1:
+      return ELF::R_ARM_TARGET1;
+    case MCSymbolRefExpr::VK_ARM_TARGET2:
+      return ELF::R_ARM_TARGET2;
+    case MCSymbolRefExpr::VK_ARM_PREL31:
+      return ELF::R_ARM_PREL31;
+    case MCSymbolRefExpr::VK_ARM_SBREL:
+      return ELF::R_ARM_SBREL32;
+    case MCSymbolRefExpr::VK_ARM_TLSLDO:
+      return ELF::R_ARM_TLS_LDO32;
+    case MCSymbolRefExpr::VK_TLSCALL:
+      return ELF::R_ARM_TLS_CALL;
+    case MCSymbolRefExpr::VK_TLSDESC:
+      return ELF::R_ARM_TLS_GOTDESC;
+    case MCSymbolRefExpr::VK_TLSLDM:
+      return ELF::R_ARM_TLS_LDM32;
+    case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
+      return ELF::R_ARM_TLS_DESCSEQ;
+    }
+  case ARM::fixup_arm_condbranch:
+  case ARM::fixup_arm_uncondbranch:
+    return ELF::R_ARM_JUMP24;
+  case ARM::fixup_arm_movt_hi16:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_MOVT_ABS;
+    case MCSymbolRefExpr::VK_ARM_SBREL:
+      return ELF::R_ARM_MOVT_BREL;
+    }
+  case ARM::fixup_arm_movw_lo16:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_MOVW_ABS_NC;
+    case MCSymbolRefExpr::VK_ARM_SBREL:
+      return ELF::R_ARM_MOVW_BREL_NC;
+    }
+  case ARM::fixup_t2_movt_hi16:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_THM_MOVT_ABS;
+    case MCSymbolRefExpr::VK_ARM_SBREL:
+      return ELF::R_ARM_THM_MOVT_BREL;
+    }
+  case ARM::fixup_t2_movw_lo16:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_ARM_THM_MOVW_ABS_NC;
+    case MCSymbolRefExpr::VK_ARM_SBREL:
+      return ELF::R_ARM_THM_MOVW_BREL_NC;
+    }
+  }
+}
+
+void ARMELFObjectWriter::addTargetSectionFlags(MCContext &Ctx,
+                                               MCSectionELF &Sec) {
+  // The mix of execute-only and non-execute-only at link time is
+  // non-execute-only. To avoid the empty implicitly created .text
+  // section from making the whole .text section non-execute-only, we
+  // mark it execute-only if it is empty and there is at least one
+  // execute-only section in the object.
+  MCSectionELF *TextSection =
+      static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
+  if (Sec.getKind().isExecuteOnly() && !TextSection->hasInstructions() &&
+      !TextSection->hasData()) {
+    TextSection->setFlags(TextSection->getFlags() | ELF::SHF_ARM_PURECODE);
+  }
+}
+
+std::unique_ptr<MCObjectTargetWriter>
+llvm::createARMELFObjectWriter(uint8_t OSABI) {
+  return std::make_unique<ARMELFObjectWriter>(OSABI);
+}