linux-kernel - Re: [PATCH] kallsyms: fix nonconverging kallsyms table with lld

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK8P3a2cVpJf+r2b-8YCbknOeOA4w=bY8njr-+vmzbmm8AAC3Q@mail.gmail.com>
Date:   Wed, 9 Jun 2021 13:24:18 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        David Brazdil <dbrazdil@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Mikhail Petrov <Mikhail.Petrov@....dev>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        mfaltesek@...gle.com
Subject: Re: [PATCH] kallsyms: fix nonconverging kallsyms table with lld

On Wed, Jun 9, 2021 at 1:05 PM Guenter Roeck <linux@...ck-us.net> wrote:
> On Thu, Feb 04, 2021 at 04:29:47PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > ARM randconfig builds with lld sometimes show a build failure
> > from kallsyms:
> >
> >   Inconsistent kallsyms data
> >   Try make KALLSYMS_EXTRA_PASS=1 as a workaround
> >
> > The problem is the veneers/thunks getting added by the linker extend
> > the symbol table, which in turn leads to more veneers being needed,
> > so it may take a few extra iterations to converge.
> >
> > This bug has been fixed multiple times before, but comes back every time
> > a new symbol name is used. lld uses a different set of idenitifiers from
> > ld.bfd, so the additional ones need to be added as well.
> >
> > I looked through the sources and found that arm64 and mips define similar
> > prefixes, so I'm adding those as well, aside from the ones I observed. I'm
> > not sure about powerpc64, which seems to already be handled through a
> > section match, but if it comes back, the "__long_branch_" and "__plt_"
> > prefixes would have to get added as well.
> >
>
> This is such a whack-a-mole. The problem is hitting us yet again. I suspect
> it may be due to a new version of lld using new symbols, but I didn't really
> try to track it down. Is there an easy way to search for missed symbols ?

The way I did it previously was to hack Kbuild to not remove the temporary
files after a failure, and then compare the "objdump --syms" output of the
last two stages.

I suppose we could improve the situation if scripts/link-vmlinux.sh was able
to do that automatically, and compare the kallsyms output .S file between
steps 1 and 2.

        Arnd