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Date:   Thu, 3 Nov 2022 08:22:44 +0100
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Subject: Re: [RFC PATCH] kbuild: pass objects instead of archives to linker
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To:     Masahiro Yamada <masahiroy@kernel.org>,
        Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-kbuild@vger.kernel.org, Michael Matz <matz@suse.de>,
        Kees Cook <keescook@chromium.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Fangrui Song <maskray@google.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
References: <20221102091308.11568-1-masahiroy@kernel.org>
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 <CAK7LNASjBm=WWpkSaL1+QuLokhnepUucvhYyP3CCeZYx6nOTHA@mail.gmail.com>
From:   Jiri Slaby <jirislaby@kernel.org>
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On 02. 11. 22, 10:44, Masahiro Yamada wrote:
> Jiri Slaby reported that the (not-upstreamed) GCC-LTO tree got broken
> due to 321648455061 ("kbuild: use obj-y instead extra-y for objects
> placed at the head")
> 
> https://lore.kernel.org/linux-kbuild/ea468b86-abb7-bb2b-1e0a-4c8959d23f1c@kernel.org/
> 
> 
> I am not pretty sure because I did not check the downstream code.
> 
> 
> If I understood his report correctly, the reason for the breakage is
> because I put all objects into the thin archive, expecting
> the linker would preserve the object order in the archive.
> 
> By specifying the object order directly in the command line,
> GCC-LTO should get back working again.

...

> I think my patch is unneeded (hence RFC), but I just wanted to know
> if linkers (gnu ld and lld) see any difference.

Yes, including your patch (instead of vmlinux.S and /compressed/* 
changes) also fixes the issue. So the linker (gcc-ld) indeed respects 
command line, but not order of objects in .a.

thanks,
-- 
js
suse labs