linux-kernel - Re: [PATCH v3 17/30] init: lto: ensure initcall ordering

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Message-ID: <202009181428.3C45B57DA@keescook>
Date:   Fri, 18 Sep 2020 14:29:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v3 17/30] init: lto: ensure initcall ordering

On Fri, Sep 18, 2020 at 01:14:23PM -0700, Sami Tolvanen wrote:
> With LTO, the compiler doesn't necessarily obey the link order for
> initcalls, and initcall variables need globally unique names to avoid
> collisions at link time.
> 
> This change exports __KBUILD_MODNAME and adds the initcall_id() macro,
> which uses it together with __COUNTER__ and __LINE__ to help ensure
> these variables have unique names, and moves each variable to its own
> section when LTO is enabled, so the correct order can be specified using
> a linker script.
> 
> The generate_initcall_ordering.pl script uses nm to find initcalls from
> the object files passed to the linker, and generates a linker script
> that specifies the same order for initcalls that we would have without
> LTO. With LTO enabled, the script is called in link-vmlinux.sh through
> jobserver-exec to limit the number of jobs spawned.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Thanks for the update; using jobserver-exec looks much better for
controlling the build resources. :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook