linux-kernel - Re: [PATCH] ARM: module: treat exit sections the same as init sections when !CONFIG_MODULE

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Message-ID: <YJU3KrZzSRYNH6Zt@gunter>
Date:   Fri, 7 May 2021 14:48:42 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: module: treat exit sections the same as init
 sections when !CONFIG_MODULE_UNLOAD

+++ Russell King - ARM Linux admin [07/05/21 13:30 +0100]:
>On Fri, May 07, 2021 at 02:13:22PM +0200, Jessica Yu wrote:
>> Dynamic code patching (alternatives, jump_label and static_call) can
>> have sites in __exit code, even if __exit is never executed. Therefore
>> __exit must be present at runtime, at least for as long as __init code is.
>...
>> Previously, the module loader never loaded the exit sections in the first
>> place when CONFIG_MODULE_UNLOAD=n. Commit 33121347fb1c ("module: treat exit
>> sections the same as init sections when !CONFIG_MODULE_UNLOAD") addressed
>> the issue by having the module loader load the exit sections and then making
>> __exit identify as __init for !MODULE_UNLOAD. Then, since they are treated
>> like init sections, they will be also discarded after init.
>>
>> That commit satisfied the above requirements for jump_labels and
>> static_calls by modifying the checks in the core module_init_section()
>> function in kernel/module.c to include exit sections. However, ARM
>> overrides these and implements their own module_{init,exit}_section()
>> functions. Add a similar check for exit sections to ARM's
>> module_init_section() function so that all arches are on the same page.
>
>Shouldn't the module core code itself be doing:
>
>	module_init_section(name) || module_exit_section(name)
>
>itself when CONFIG_MODULE_UNLOAD is not set, rather than pushing this
>logic down into every module_init_section() implementation?

Yeah, that sounds better. Originally, I had wanted to keep the #ifndef
in one place to keep the churn to a minimum.

But seeing that we have to patch up ARM too, it's probably the less
ugly option now. Let me cook up an alternative patch and resend.

Thanks,

Jessica