From: Petr Mladek <pmladek@suse.com>
To: Cheng Jian <cj.chengjian@huawei.com>
Cc: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
chenwandun@huawei.com, xiexiuqi@huawei.com,
bobo.shaobowang@huawei.com, huawei.libin@huawei.com,
jeyu@kernel.org, jikos@kernel.org
Subject: Re: [PATCH] module: make module symbols visible after init
Date: Thu, 4 Jun 2020 10:57:12 +0200 [thread overview]
Message-ID: <20200604085712.GD22497@linux-b0ei> (raw)
In-Reply-To: <20200603141200.17745-1-cj.chengjian@huawei.com>
On Wed 2020-06-03 14:12:00, Cheng Jian wrote:
> When lookup the symbols of module by module_kallsyms_lookup_name(),
> the symbols address is visible only if the module's status isn't
> MODULE_STATE_UNFORMED, This is problematic.
>
> When complete_formation is done, the state of the module is modified
> to MODULE_STATE_COMING, and the symbol of module is visible to the
> outside.
>
> At this time, the init function of the module has not been called,
> so if the address of the function symbol has been found and called,
> it may cause some exceptions.
It is really handful that module symbols can be found already when
the module is MODULE_STATE_COMING state. It is used by livepatching,
ftrace, and maybe some other subsystems.
The problem is that nobody is allowed to use (call) module symbols
before mod->init() is called and the module is moved to
MODULE_STATE_LIVE.
By other words. Any code that calls module symbols before the module
is fully initialized is buggy. The caller should get fixed,
not the kallsyms side.
Have you seen such a problem in the real life, please?
Best Regards,
Petr
next prev parent reply other threads:[~2020-06-04 8:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 14:12 [PATCH] module: make module symbols visible after init Cheng Jian
2020-06-03 17:00 ` Miroslav Benes
2020-06-04 9:49 ` Jessica Yu
2020-06-04 8:57 ` Petr Mladek [this message]
2020-06-04 12:55 ` chengjian (D)
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