[PATCH] D159179: [MC][ELF] Don't emit .note.GNU-stack sections on Solaris

[Rainer Orth via Phabricator via llvm-commits]

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LLVM currently emits `.note.GNU-stack` sections on all ELF targets.

However, Solaris ld doesn't know/care about them.  Even worse, with the revised Solaris GNU ld patch (D85309 <https://reviews.llvm.org/D85309>), there are hundreds of warnings:

  /usr/gnu/bin/ld: warning: /usr/lib/amd64/crtn.o: missing .note.GNU-stack section implies executable stack
  /usr/gnu/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker

The Solaris crts are not going to change here, and even if they were, GNU ld would emit `PT_GNU_STACK` segments that Solaris `ld.so.1` ignores.

So the note sections are completely useless on Solaris and this patch disables their creation.

Instead, Solaris has its own mechanisms to control stack executability: `PT_SUNW_STACK`, `DT_SUNW_SX_NXSTACK` and the system-wide control via `sxadm` where `nxstack` defaults to on.

Tested on `amd64-pc-solaris2.11` and `sparcv9-sun-solaris2.11` with Solaris ld and GNU ld, and `x86_64-pc-linux-gnu`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159179

Files:
  llvm/lib/MC/MCAsmInfoELF.cpp


Index: llvm/lib/MC/MCAsmInfoELF.cpp
===================================================================
--- llvm/lib/MC/MCAsmInfoELF.cpp
+++ llvm/lib/MC/MCAsmInfoELF.cpp
@@ -21,7 +21,12 @@
 void MCAsmInfoELF::anchor() {}
 
 MCSection *MCAsmInfoELF::getNonexecutableStackSection(MCContext &Ctx) const {
-  return Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0);
+  // Solaris doesn't know/doesn't care about .note.GNU-stack sections, so
+  // don't emit them.
+  if (Ctx.getTargetTriple().isOSSolaris())
+    return nullptr;
+  else
+    return Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0);
 }
 
 MCAsmInfoELF::MCAsmInfoELF() {


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