[PATCH v2 15/28] init: lto: ensure initcall ordering

[Sami Tolvanen]

On Thu, Sep 10, 2020 at 10:25:40AM +0100, David Woodhouse wrote:
> On Thu, 2020-09-03 at 13:30 -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 intended order. With LTO, the script is called in
> > link-vmlinux.sh.
> 
> Is this guaranteed to give you the *same* initcall ordering with LTO as
> without?

Yes. It follows the link order, just like the linker without LTO, and
also preserves the order within each file.

Sami