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SubjectRe: ftrace/kprobes: Warning when insmod two modules
(2014/03/24 23:59), Steven Rostedt wrote:
> On Mon, 24 Mar 2014 20:26:05 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
>
>
>> Thank you for reporting with this pretty backtrace :)
>> Steven, I think this is not the kprobe bug but ftrace (and perhaps, module).
>
> Looks to be more of a module issue than a ftrace issue.
>
>>
>> If the ftrace can set loading module text read only before the module subsystem
>> expected, I think it should be protected by the module subsystem itself
>> (e.g. set_all_modules_text_ro(rw) skips the modules which is MODULE_STATE_COMING)
>>
>
> Does this patch fix it?

Yep, I tested using my reproducer and confirmed that this patch fixed
this issue, thanks!

Thanks,
Takao Indoh

>
> In-review-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 5a50539..a1acabf 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -207,10 +207,11 @@ struct module_use {
> };
>
> enum module_state {
> - MODULE_STATE_LIVE, /* Normal state. */
> - MODULE_STATE_COMING, /* Full formed, running module_init. */
> - MODULE_STATE_GOING, /* Going away. */
> - MODULE_STATE_UNFORMED, /* Still setting it up. */
> + MODULE_STATE_LIVE, /* Normal state. */
> + MODULE_STATE_COMING, /* Full formed, running module_init. */
> + MODULE_STATE_COMING_FINAL, /* Ready to be changed to read only. */
> + MODULE_STATE_GOING, /* Going away. */
> + MODULE_STATE_UNFORMED, /* Still setting it up. */
> };
>
> /**
> diff --git a/kernel/module.c b/kernel/module.c
> index d24fcf2..0905bed 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1805,7 +1805,8 @@ void set_all_modules_text_ro(void)
>
> mutex_lock(&module_mutex);
> list_for_each_entry_rcu(mod, &modules, list) {
> - if (mod->state == MODULE_STATE_UNFORMED)
> + if (mod->state == MODULE_STATE_UNFORMED ||
> + mod->state == MODULE_STATE_COMING)
> continue;
> if ((mod->module_core) && (mod->core_text_size)) {
> set_page_attributes(mod->module_core,
> @@ -3020,6 +3021,13 @@ static int do_init_module(struct module *mod)
> blocking_notifier_call_chain(&module_notify_list,
> MODULE_STATE_COMING, mod);
>
> + /*
> + * This module must not be changed by set_all_modules_text_ro()
> + * until we get here. Otherwise notifiers that change text
> + * (like ftrace does) will break.
> + */
> + mod->state = MODULE_STATE_COMING_FINAL;
> +
> /* Set RO and NX regions for core */
> set_section_ro_nx(mod->module_core,
> mod->core_text_size,
>
>
>


--
印藤隆夫(INDOH Takao)
E-Mail : indou.takao@jp.fujitsu.com
TEL : 7551-4832(055-924-7241)
富士通(株) PFソ事本)Linux開発統括部 開発部



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