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

Kees Cook
2020-09-18T21:31:11Z

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@google.com>

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

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

--
Kees Cook