linux-kernel - Re: [RFC PATCH 2/3] objtool: Enable and implement 'mcount' subcommand

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Message-Id: <1647855901.ds85pb94ut.naveen@linux.ibm.com>
Date:   Mon, 21 Mar 2022 15:18:47 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>
Cc:     "aik@...abs.ru" <aik@...abs.ru>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>
Subject: Re: [RFC PATCH 2/3] objtool: Enable and implement 'mcount' subcommand

Christophe Leroy wrote:
> 
> 
> Le 21/03/2022 à 09:19, Naveen N. Rao a écrit :
>> Christophe Leroy wrote:
>> 
>> We don't enable ftrace for vdso, so I suspect objtool run above will be 
>> a no-op. This needs to be confirmed, of course.
>> 
> 
> I just checked without the series: recordmcount isn't run for VDSO, so 
> objtool shouldn't be run either when the series is applied.

Agree. I was only pointing out that it would be harmless, but it is good 
to ensure objtool is skipped for files/directories where ftrace isn't 
enabled. recordmcount keys off the presence of CC_FLAGS_FTRACE, and we 
should do the same for 'objtool --mcount'.


- Naveen