linux-kernel - Re: [PATCH] x86: assemble with -Wa,--noexecstack to avoid BFD 2.39 warning

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Date:   Mon, 8 Aug 2022 14:08:17 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Nick Clifton <nickc@...hat.com>,
        Fangrui Song <maskray@...gle.com>,
        Jens Axboe <axboe@...nel.dk>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Tom Rix <trix@...hat.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Nicolas Schier <n.schier@....de>,
        Brijesh Singh <brijesh.singh@....com>,
        Michael Roth <michael.roth@....com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Ben Dooks <ben-linux@...ff.org>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Subject: Re: [PATCH] x86: assemble with -Wa,--noexecstack to avoid BFD 2.39 warning

On Mon, Aug 8, 2022 at 1:32 PM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
>
> Thanks for the link; I recall Ard mentioning the ELF segments are
> ignored by the kernels loader in another thread.

Yeah, the kernel loader is not some generic ELF loader thing.

> Perhaps we should be adding
> --no-warn-execstack
> wrapped in an ld-option check to KBUILD_LDFLAGS at the top level?

I think both the linker flag and the assembler flag are the "correct"
thing to do.

And yes, I don't think there is anything architecture-specific about
it, and the top-level Makefile is likely the right thing to modify.

I'm a tiny bit worried about "what versions of as/ld accept those
flags", though.

              Linus