linux-kernel - Re: [PATCH] ftrace/module: Allow ftrace to make only loaded module text read-write

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Date:   Mon, 14 Oct 2019 14:31:21 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] ftrace/module: Allow ftrace to make only loaded module
 text read-write

+++ Steven Rostedt [10/10/19 08:58 -0400]:
>On Wed, 9 Oct 2019 22:36:38 -0400
>Steven Rostedt <rostedt@...dmis.org> wrote:
>
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -2029,6 +2029,37 @@ static void module_enable_nx(const struct module *mod)
>>  	frob_writable_data(&mod->init_layout, set_memory_nx);
>>  }
>>
>
>Also, if you are worried about these being used anywhere else, we can
>add:
>
>> +void set_module_text_rw(const struct module *mod)
>> +{
>> +	if (!rodata_enabled)
>> +		return;
>> +
>> +	mutex_lock(&module_mutex);
>> +	if (mod->state == MODULE_STATE_UNFORMED)
>
>	if (mod->state == MODULE_STATE_UNFORMED ||
>	    mod->state == MODULE_STATE_LIVE)
>
>As this will keep it from being used on modules that are executing.

Yeah, that'd be good. Aside from the big ftrace_module_init/enable
debate, I'm fine with this patch itself (with the change above), feel
free to include my Ack in case you want to include it with the rest of
the ftrace text_poke stuff.

Acked-by: Jessica Yu <jeyu@...nel.org>

Thanks,

Jessica

>> +		goto out;
>> +
>> +	frob_text(&mod->core_layout, set_memory_rw);
>> +	frob_text(&mod->init_layout, set_memory_rw);
>> +out:
>> +	mutex_unlock(&module_mutex);
>> +}
>> +
>> +void set_module_text_ro(const struct module *mod)
>> +{
>> +	if (!rodata_enabled)
>> +		return;
>> +
>> +	mutex_lock(&module_mutex);
>> +	if (mod->state == MODULE_STATE_UNFORMED ||
>> +	    mod->state == MODULE_STATE_GOING)
>> +		goto out;
>> +
>> +	frob_text(&mod->core_layout, set_memory_ro);
>> +	frob_text(&mod->init_layout, set_memory_ro);
>> +out:
>> +	mutex_unlock(&module_mutex);
>> +}
>> +