Index: llvm/lib/Target/X86/X86AsmPrinter.cpp =================================================================== --- llvm/lib/Target/X86/X86AsmPrinter.cpp +++ llvm/lib/Target/X86/X86AsmPrinter.cpp @@ -19,6 +19,7 @@ #include "X86InstrInfo.h" #include "X86MachineFunctionInfo.h" #include "llvm/BinaryFormat/COFF.h" +#include "llvm/BinaryFormat/ELF.h" #include "llvm/CodeGen/MachineConstantPool.h" #include "llvm/CodeGen/MachineModuleInfoImpls.h" #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h" @@ -30,6 +31,7 @@ #include "llvm/MC/MCContext.h" #include "llvm/MC/MCExpr.h" #include "llvm/MC/MCSectionCOFF.h" +#include "llvm/MC/MCSectionELF.h" #include "llvm/MC/MCSectionMachO.h" #include "llvm/MC/MCStreamer.h" #include "llvm/MC/MCSymbol.h" @@ -539,6 +541,42 @@ void X86AsmPrinter::EmitStartOfAsmFile(Module &M) { const Triple &TT = TM.getTargetTriple(); + if (TT.isOSBinFormatELF()) { + // Assemble feature flags that may require creation of a note section. + unsigned FeatureFlagsAnd = 0; + if (M.getModuleFlag("cf-protection-branch")) + FeatureFlagsAnd |= ELF::GNU_PROPERTY_X86_FEATURE_1_IBT; + if (M.getModuleFlag("cf-protection-return")) + FeatureFlagsAnd |= ELF::GNU_PROPERTY_X86_FEATURE_1_SHSTK; + + if (FeatureFlagsAnd) { + // Emit a .note.gnu.property section with the flags. + if (!TT.isArch32Bit() && !TT.isArch64Bit()) + llvm_unreachable("CFProtection used on invalid architecture!"); + MCSection *Cur = OutStreamer->getCurrentSectionOnly(); + MCSection *Nt = MMI->getContext().getELFSection( + ".note.gnu.property", ELF::SHT_NOTE, ELF::SHF_ALLOC); + OutStreamer->SwitchSection(Nt); + + // Emitting note header. + int WordSize = TT.isArch64Bit() ? 8 : 4; + EmitAlignment(WordSize == 4 ? 2 : 3); + OutStreamer->EmitIntValue(4, 4 /*size*/); // data size for "GNU\0" + OutStreamer->EmitIntValue(8 + WordSize, 4 /*size*/); // Elf_Prop size + OutStreamer->EmitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4 /*size*/); + OutStreamer->EmitBytes(StringRef("GNU", 4)); // note name + + // Emitting an Elf_Prop for the CET properties. + OutStreamer->EmitIntValue(ELF::GNU_PROPERTY_X86_FEATURE_1_AND, 4); + OutStreamer->EmitIntValue(WordSize, 4); // data size + OutStreamer->EmitIntValue(FeatureFlagsAnd, WordSize); // data + EmitAlignment(WordSize == 4 ? 2 : 3); // padding + + OutStreamer->endSection(Nt); + OutStreamer->SwitchSection(Cur); + } + } + if (TT.isOSBinFormatMachO()) OutStreamer->SwitchSection(getObjFileLowering().getTextSection()); Index: llvm/test/CodeGen/X86/note-cet-property.ll =================================================================== --- /dev/null +++ llvm/test/CodeGen/X86/note-cet-property.ll @@ -0,0 +1,32 @@ +; RUN: llc -mtriple i686-pc-linux < %s | FileCheck %s --check-prefix=X86 +; RUN: llc -mtriple x86_64-pc-linux < %s | FileCheck %s --check-prefix=X86_64 + +; This test checks that the compiler emits a .note.gnu.property section for +; modules with "cf-protection" module flags. + +; X86: .section .note.gnu.property,"a",@note +; X86-NEXT: .p2align 2 +; X86-NEXT: .long 4 +; X86-NEXT: .long 12 +; X86-NEXT: .long 5 +; X86-NEXT: .asciz "GNU" +; X86-NEXT: .long 3221225474 +; X86-NEXT: .long 4 +; X86-NEXT: .long 3 +; X86-NEXT: .p2align 2 + +; X86_64: .section .note.gnu.property,"a",@note +; X86_64-NEXT: .p2align 3 +; X86_64-NEXT: .long 4 +; X86_64-NEXT: .long 16 +; X86_64-NEXT: .long 5 +; X86_64-NEXT: .asciz "GNU" +; X86_64-NEXT: .long 3221225474 +; X86_64-NEXT: .long 8 +; X86_64-NEXT: .quad 3 +; X86_64-NEXT: .p2align 3 + +!llvm.module.flags = !{!0, !1} + +!0 = !{i32 4, !"cf-protection-return", i32 1} +!1 = !{i32 4, !"cf-protection-branch", i32 1}