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From: Petr Mladek <>
To: Cheng Jian <>
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: <>

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

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,

  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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