[libc-commits] [clang-tools-extra] [libc] [clang] [flang] [llvm] [compiler-rt] [X86] Do not end 'note.gnu.property' section with -fcf-protection (PR #79360)

[Adhemerval Zanella via libc-commits]

https://github.com/zatrazz updated https://github.com/llvm/llvm-project/pull/79360

>From 240ec1a6b9dda5e6c625e096c52d70eb6458180b Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella at linaro.org>
Date: Wed, 24 Jan 2024 16:49:30 -0300
Subject: [PATCH] [X86] Do not end 'note.gnu.property' section with
 -fcf-protection

The glibc now adds the required minimum ISA level for libc-nonshared.a
(linked on all programs) and this is done with a inline asm along with
.note.gnu.property an .pushsection/.popsection.  However, x86 backend
always end the 'note.gnu.property' section when building with
-fcf-protection, leading to assert failure:

llvm/llvm-project-git/llvm/lib/MC/MCStreamer.cpp:1251: virtual void
llvm::MCStreamer::switchSection(llvm::MCSection*, const llvm::MCExpr*):
Assertion `!Section->hasEnded() && "Section already ended"' failed.

[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86/isa-level.c;h=3f1b269848a52f994275bab6f60dded3ded6b144;hb=HEAD
---
 llvm/lib/Target/X86/X86AsmPrinter.cpp         |  1 -
 .../X86/note-cet-property-inlineasm.ll        | 30 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/X86/note-cet-property-inlineasm.ll

diff --git a/llvm/lib/Target/X86/X86AsmPrinter.cpp b/llvm/lib/Target/X86/X86AsmPrinter.cpp
index 9f0fd4d0938e97f..87ec8aa23080e00 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86AsmPrinter.cpp
@@ -877,7 +877,6 @@ void X86AsmPrinter::emitStartOfAsmFile(Module &M) {
       OutStreamer->emitInt32(FeatureFlagsAnd);            // data
       emitAlignment(WordSize == 4 ? Align(4) : Align(8)); // padding
 
-      OutStreamer->endSection(Nt);
       OutStreamer->switchSection(Cur);
     }
   }
diff --git a/llvm/test/CodeGen/X86/note-cet-property-inlineasm.ll b/llvm/test/CodeGen/X86/note-cet-property-inlineasm.ll
new file mode 100644
index 000000000000000..a0e5b4add1b386e
--- /dev/null
+++ b/llvm/test/CodeGen/X86/note-cet-property-inlineasm.ll
@@ -0,0 +1,30 @@
+; RUN: llc -mtriple x86_64-unknown-linux-gnu %s -o %t.o -filetype=obj
+; RUN: llvm-readobj -n %t.o | FileCheck %s
+
+module asm ".pushsection \22.note.gnu.property\22,\22a\22, at note"
+module asm "     .p2align 3"
+module asm "     .long 1f - 0f"
+module asm "     .long 4f - 1f"
+module asm "     .long 5"
+module asm "0:   .asciz \22GNU\22"
+module asm "1:   .p2align 3"
+module asm "     .long 0xc0008002"
+module asm "     .long 3f - 2f"
+module asm "2:   .long ((1U << 0) | 0 | 0 | 0)"
+module asm "3:   .p2align 3"
+module asm "4:"
+module asm " .popsection"
+
+!llvm.module.flags = !{!0, !1}
+
+!0 = !{i32 4, !"cf-protection-return", i32 1}
+!1 = !{i32 4, !"cf-protection-branch", i32 1}
+
+; CHECK:      Type: NT_GNU_PROPERTY_TYPE_0
+; CHECK-NEXT: Property [
+; CHECK-NEXT:   x86 feature: IBT, SHSTK
+; CHECK-NEXT: ]
+; CHECK:      Type: NT_GNU_PROPERTY_TYPE_0
+; CHECK-NEXT: Property [
+; CHECK-NEXT:   x86 ISA needed: x86-64-baseline
+; CHECK-NEXT: ]