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:

quoted

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.

...

quoted

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

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