linux-kernel - Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS

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Message-ID: <202006221555.45BB6412F@keescook>
Date:   Mon, 22 Jun 2020 15:57:21 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Fangrui Song <maskray@...gle.com>
Cc:     Borislav Petkov <bp@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        clang-built-linux@...glegroups.com, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS

On Mon, Jun 22, 2020 at 03:52:37PM -0700, Fangrui Song wrote:
> > And it's not in the output:
> > 
> > $ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
> > No version information found in this file.
> > 
> > So... for the kernel we need to silence it right now.
> 
> Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
> sections come from?

It's not reporting it correctly:

.gnu.version_d  0x00000000008966b0        0x0
 .gnu.version_d
                0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o

.gnu.version    0x00000000008966b0        0x0
 .gnu.version   0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o

.gnu.version_r  0x00000000008966b0        0x0
 .gnu.version_r
                0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o

it just reports whatever file is listed on the link command line first.

> If it is a bug, we should probably figure out which version of binutils
> has fixed the bug.

I see this with binutils 2.34...

-- 
Kees Cook