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Date:   Mon, 22 Jun 2020 15:57:21 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Fangrui Song <maskray@google.com>
Cc:     Borislav Petkov <bp@suse.de>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <natechancellor@gmail.com>,
        clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS
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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