linux-kernel - Freeing alternatives sections after module init?

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Message-ID: <20160627210727.GA27476@packer-debian-8-amd64.digitalocean.com>
Date:	Mon, 27 Jun 2016 17:07:27 -0400
From:	Jessica Yu <jeyu@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org
Subject: Freeing alternatives sections after module init?

Hi Rusty,

I noticed that the module loader keeps .altinstructions and
.altinstr_replacement (which are normally freed after kernel init) in
core memory after module init, so these sections are never freed for
modules.

In fact, the module loader seems to keep a number of sections normally
marked between __init_begin and __init_end (which are then freed in
free_initmem()) in module core memory, for example on x86, there's
also .parainstructions and .altinstr_aux.

I was just wondering if this discrepancy was intentional :-)
Shouldn't these sections be freed after init? Though it probably
doesn't hurt to keep some of these sections in memory,
.altinstr_replacement is (for whatever reason) an executable section,
and is technically not needed anymore after apply_alternatives()
copies the replacement instructions, so it might be good to free it.

Thanks,
Jessica