linux-kernel - Re: [PATCH v2 2/3] module: Use the same logic for setting and unsetting RO/NX

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Date:	Mon, 09 Nov 2015 06:10:45 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>
Cc:	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	"Cyril B." <cbay@...aysdata.com>, Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2 2/3] module: Use the same logic for setting and unsetting RO/NX

Josh Poimboeuf <jpoimboe@...hat.com> writes:
> When setting a module's RO and NX permissions, set_section_ro_nx() is
> used, but when clearing them, unset_module_{init,core}_ro_nx() are used.
> The unset functions don't have the same checks the set function has for
> partial page protections.  It's probably harmless, but it's still
> confusingly asymmetrical.
>
> Instead, use the same logic to do both.  Also add some new
> set_module_{init,core}_ro_nx() helper functions for more symmetry with
> the unset functions.

Yes, this seems sensible.

One nit to pick:

> +			unsigned long total_size,
> +			int (*set_ro)(unsigned long start, int num_pages),
> +			int (*set_nx)(unsigned long start, int num_pages))

...
> +	set_section_ro_nx(mod->module_core, mod->core_text_size,
> +			  mod->core_ro_size, mod->core_size,
> +			  set_memory_rw, set_memory_x);

set_ro == set_memory_rw here.  That's just confusing.

I think we have to avoid the word "set" in the function parameters
since it may unset instead.

Suggest "alter_ro" or "frob_ro" instead?

Thanks,
Rusty.
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