linux-kernel - Re: [PATCH v6 00/29] Warn on orphan section placement

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Date:   Tue, 1 Sep 2020 11:02:02 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 00/29] Warn on orphan section placement

On Tue, Sep 1, 2020 at 8:17 AM Kees Cook <keescook@...omium.org> wrote:
>
> On Tue, Sep 01, 2020 at 10:16:47AM +0200, Ingo Molnar wrote:
> >
> > * Ingo Molnar <mingo@...nel.org> wrote:
> >
> > >
> > > * Ingo Molnar <mingo@...nel.org> wrote:
> > >
> > > >
> > > > * Kees Cook <keescook@...omium.org> wrote:
> > > >
> > > > > On Fri, Aug 21, 2020 at 12:42:41PM -0700, Kees Cook wrote:
> > > > > > Hi Ingo,
> > > > > >
> > > > > > Based on my testing, this is ready to go. I've reviewed the feedback on
> > > > > > v5 and made a few small changes, noted below.
> > > > >
> > > > > If no one objects, I'll pop this into my tree for -next. I'd prefer it
> > > > > go via -tip though! :)
> > > > >
> > > > > Thanks!
> > > >
> > > > I'll pick it up today, it all looks very good now!
> > >
> > > One thing I found in testing is that it doesn't handler older LD
> > > versions well enough:
> > >
> > >   ld: unrecognized option '--orphan-handling=warn'
>
> Oh! Uhm, yikes. Thanks for noticing this.
>
> > > Could we just detect the availability of this flag, and emit a warning
> > > if it doesn't exist but otherwise not abort the build?
>
> Yeah, I'll respin those patches.
>
> > > This is with:
> > >
> > >   GNU ld version 2.25-17.fc23
>
> (At best, this is from 2015 ... but yes, min binutils in 2.23.)

Ah, crap! Indeed arch/powerpc/Makefile wraps this in ld-option.

Uh oh, the ppc vdso uses cc-ldoption which was removed! (I think by
me; let me send patches)  How is that not an error?  Yes, guilty,
officer.
commit 055efab3120b ("kbuild: drop support for cc-ldoption").
Did I not know how to use grep, or?  No, it is
commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
that is wrong.
-- 
Thanks,
~Nick Desaulniers