From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
Sathvika Vasireddy <sv@linux.ibm.com>
Cc: "aik@ozlabs.ru" <aik@ozlabs.ru>,
"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mbenes@suse.cz" <mbenes@suse.cz>,
"mpe@ellerman.id.au" <mpe@ellerman.id.au>,
"peterz@infradead.org" <peterz@infradead.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>
Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount
Date: Tue, 24 May 2022 10:20:17 +0000 [thread overview]
Message-ID: <d45030be-3f6b-ebeb-3d63-bf7a96d3ff3b@csgroup.eu> (raw)
In-Reply-To: <1653386854.o7nss9hzc9.naveen@linux.ibm.com>
Le 24/05/2022 à 12:15, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>>
>>
>> Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
>>> Architectures can select HAVE_NOP_MCOUNT if they choose
>>> to nop out mcount call sites. If that config option is
>>> selected, then --mnop is passed as an option to objtool,
>>> along with --mcount.
>>>
>>
>> Is there a reason not to nop out mcount call sites on powerpc as well ?
>
> Yes, if there are functions that are out of range of _mcount(), then the
> linker would have inserted long branch trampolines. We detect such cases
> during boot. But, if we nop out the _mcount call sites during build
> time, we will need some other way to identify these.
>
But does it really matter whether _mcount is reachable or not ?
_mcount is never used, and the function we want to call in lieu of
_mcount might be reachable while _mcount is not or might be unreachable
while _mcount is.
Christophe
next prev parent reply other threads:[~2022-05-24 10:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-23 17:55 [RFC PATCH 0/4] objtool: Enable and implement --mcount option on powerpc Sathvika Vasireddy
2022-05-23 17:55 ` [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount Sathvika Vasireddy
2022-05-24 8:54 ` Christophe Leroy
2022-05-24 10:15 ` Naveen N. Rao
2022-05-24 10:20 ` Christophe Leroy [this message]
2022-05-24 10:31 ` Naveen N. Rao
2022-05-25 11:36 ` Peter Zijlstra
2022-05-26 11:51 ` Naveen N. Rao
2022-05-23 17:55 ` [RFC PATCH 2/4] objtool: Enable objtool to run only on files with ftrace enabled Sathvika Vasireddy
2022-05-24 8:57 ` Christophe Leroy
2022-05-24 10:53 ` Sathvika Vasireddy
2022-05-24 13:28 ` Christophe Leroy
2022-05-23 17:55 ` [RFC PATCH 3/4] objtool/powerpc: Enable objtool to be built on ppc Sathvika Vasireddy
2022-05-24 9:13 ` Christophe Leroy
2022-05-23 17:55 ` [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation Sathvika Vasireddy
2022-05-24 9:35 ` Christophe Leroy
2022-05-24 11:00 ` Sathvika Vasireddy
2022-05-24 13:33 ` Christophe Leroy
2022-05-25 17:27 ` Christophe Leroy
2022-05-31 6:20 ` Christophe Leroy
2022-06-16 13:34 ` Naveen N. Rao
2022-06-16 13:40 ` Christophe Leroy
2022-06-16 13:57 ` Peter Zijlstra
2022-06-16 14:06 ` Christophe Leroy
2022-06-17 14:04 ` Naveen N. Rao
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