[X32][CET] Fix size and alignment of .note.gnu.property section

[hvdijk]

Summary

X32 uses 32-bit ELF object files with 32-bit alignment, so the .note.gnu.property section needs to be emitted as it is for X86.

[MaskRay]

LGTM.

llvm/lib/Target/X86/X86AsmPrinter.cpp

646–647

While here, const int

llvm/test/CodeGen/X86/note-cet-property.ll

3

you can omit <

[hvdijk]

It wasn't just the alignment that was wrong, the section contains its own size as a field, which had an incorrect value as a result of the alignment.

[hvdijk]

llvm/test/CodeGen/X86/note-cet-property.ll

3

llc writes to stdout by default when reading from stdin, and writes to <file>.s otherwise, so just dropping < doesn't work. It's possible to use -o - instead to explicitly specify writing to stdout but the other lines in this file and the other three CET test files all use llc < %s rather than llc %s -o -, so for consistency I'd rather leave it if that's okay too?

[MaskRay]

llvm/test/CodeGen/X86/note-cet-property.ll

3

I forgot it:)

llvm/lib/Target/X86/X86AsmPrinter.cpp

if (FeatureFlagsAnd) {
       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;
+      const int WordSize =
+          TT.isArch64Bit() && TT.getEnvironment() != Triple::GNUX32 ? 8 : 4;
       emitAlignment(WordSize == 4 ? Align(4) : Align(8));
       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->emitInt32(ELF::GNU_PROPERTY_X86_FEATURE_1_AND);

llvm/test/CodeGen/X86/note-cet-property.ll

 ; 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
+; RUN: llc -mtriple x86_64-pc-linux-gnux32 < %s | FileCheck %s --check-prefix=X86
 
 ; 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