[all-commits] [llvm/llvm-project] 6ef767: [MC][ELF] Don't emit .note.GNU-stack sections on S...

rorth via All-commits all-commits at lists.llvm.org
Fri Sep 1 02:21:28 PDT 2023

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6ef767c0758512b285a357436358e0814e72fe9e
  Author: Rainer Orth <ro at gcc.gnu.org>
  Date:   2023-09-01 (Fri, 01 Sep 2023)

  Changed paths:
    M llvm/lib/MC/MCAsmInfoELF.cpp
    A llvm/test/CodeGen/X86/execstack.ll

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

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`.

Differential Revision: https://reviews.llvm.org/D159179

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