linux-kernel - RE: [PATCH] kallsyms: optimize kallsyms_lookup

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Message-Id: <1493140505.ixalh10597.astroid@naverao1-tp.none>
Date:   Tue, 25 Apr 2017 17:17:49 +0000
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     David Laight <David.Laight@...LAB.COM>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Paul Clarke <pc@...ibm.com>
Subject: RE: [PATCH] kallsyms: optimize kallsyms_lookup_name() for a few cases

Excerpts from David Laight's message of April 25, 2017 22:06:
> From: Naveen N. Rao
>> Sent: 25 April 2017 17:18
>> 1. Fail early for invalid/zero length symbols.
>> 2. Detect names of the form <mod:name> and skip checking for kernel
>> symbols in that case.
>> 
>> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
>> ---
>> Masami, Michael,
>> I have added two very simple checks here, which I felt is good to have,
>> rather than the elaborate checks in the previous version. Given the
>> change in module code to use strnchr(), the checks are now safe and
>> further tests are not probably not that useful.
> ...
>> +	if (strnchr(name, MODULE_NAME_LEN, ':'))
>> +		return module_kallsyms_lookup_name(name);
> 
> Should that be MODULE_NAME_LEN - 1 ?

The ':' character _follows_ the module name, which can itself be upto 
MODULE_NAME_LEN - 1 characters. So, we should look for it till 
MODULE_NAME_LEN.

Thanks for the review,
- Naveen