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From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
	"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 15:45:20 +0530	[thread overview]
Message-ID: <1653386854.o7nss9hzc9.naveen@linux.ibm.com> (raw)
In-Reply-To: <26c7bfc8-3089-034a-70c0-8857d7cd3a99@csgroup.eu>

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.

- Naveen


WARNING: multiple messages have this Message-ID (diff)
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	Sathvika Vasireddy <sv@linux.ibm.com>
Cc: "aik@ozlabs.ru" <aik@ozlabs.ru>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
	"mbenes@suse.cz" <mbenes@suse.cz>
Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount
Date: Tue, 24 May 2022 15:45:20 +0530	[thread overview]
Message-ID: <1653386854.o7nss9hzc9.naveen@linux.ibm.com> (raw)
In-Reply-To: <26c7bfc8-3089-034a-70c0-8857d7cd3a99@csgroup.eu>

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.

- Naveen


  reply	other threads:[~2022-05-24 10:16 UTC|newest]

Thread overview: 49+ 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 ` Sathvika Vasireddy
2022-05-23 17:55 ` [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount Sathvika Vasireddy
2022-05-23 17:55   ` Sathvika Vasireddy
2022-05-24  8:54   ` Christophe Leroy
2022-05-24  8:54     ` Christophe Leroy
2022-05-24 10:15     ` Naveen N. Rao [this message]
2022-05-24 10:15       ` Naveen N. Rao
2022-05-24 10:20       ` Christophe Leroy
2022-05-24 10:20         ` Christophe Leroy
2022-05-24 10:31         ` Naveen N. Rao
2022-05-24 10:31           ` Naveen N. Rao
2022-05-25 11:36           ` Peter Zijlstra
2022-05-25 11:36             ` Peter Zijlstra
2022-05-26 11:51             ` Naveen N. Rao
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
2022-05-23 17:55   ` Sathvika Vasireddy
2022-05-24  8:57   ` Christophe Leroy
2022-05-24  8:57     ` Christophe Leroy
2022-05-24 10:53     ` Sathvika Vasireddy
2022-05-24 10:53       ` Sathvika Vasireddy
2022-05-24 13:28       ` Christophe Leroy
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
2022-05-23 17:55   ` Sathvika Vasireddy
2022-05-24  9:13   ` Christophe Leroy
2022-05-24  9:13     ` Christophe Leroy
2022-05-23 17:55 ` [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation Sathvika Vasireddy
2022-05-23 17:55   ` Sathvika Vasireddy
2022-05-24  9:35   ` Christophe Leroy
2022-05-24  9:35     ` Christophe Leroy
2022-05-24 11:00     ` Sathvika Vasireddy
2022-05-24 11:00       ` Sathvika Vasireddy
2022-05-24 13:33       ` Christophe Leroy
2022-05-24 13:33         ` Christophe Leroy
2022-05-25 17:27         ` Christophe Leroy
2022-05-31  6:20           ` Christophe Leroy
2022-05-31  6:20             ` Christophe Leroy
2022-06-16 13:34             ` Naveen N. Rao
2022-06-16 13:34               ` Naveen N. Rao
2022-06-16 13:40               ` Christophe Leroy
2022-06-16 13:40                 ` Christophe Leroy
2022-06-16 13:57                 ` Peter Zijlstra
2022-06-16 13:57                   ` Peter Zijlstra
2022-06-16 14:06                   ` Christophe Leroy
2022-06-16 14:06                     ` Christophe Leroy
2022-06-17 14:04                     ` Naveen N. Rao
2022-06-17 14:04                       ` Naveen N. Rao

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