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Rao" Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount To: Peter Zijlstra References: <20220523175548.922671-1-sv@linux.ibm.com> <20220523175548.922671-2-sv@linux.ibm.com> <26c7bfc8-3089-034a-70c0-8857d7cd3a99@csgroup.eu> <1653386854.o7nss9hzc9.naveen@linux.ibm.com> <1653388084.w21cyb07gc.naveen@linux.ibm.com> In-Reply-To: MIME-Version: 1.0 User-Agent: astroid/4d6b06ad (https://github.com/astroidmail/astroid) Message-Id: <1653564857.f06fbbl3vg.naveen@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: VqH70ghrPi37x42qUQ2pBbdsMKAQow1X X-Proofpoint-ORIG-GUID: Peo3i2FCPjcZkXQWaKkjXDOKpPv7Iwnc X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-26_06,2022-05-25_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 phishscore=0 clxscore=1015 suspectscore=0 bulkscore=0 mlxlogscore=654 spamscore=0 adultscore=0 impostorscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2205260054 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "aik@ozlabs.ru" , "linux-kernel@vger.kernel.org" , Sathvika Vasireddy , "rostedt@goodmis.org" , "jpoimboe@redhat.com" , "mbenes@suse.cz" , "linuxppc-dev@lists.ozlabs.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Peter Zijlstra wrote: > On Tue, May 24, 2022 at 04:01:48PM +0530, Naveen N. Rao wrote: >=20 >> We need to know for sure either way. Nop'ing out the _mcount locations a= t >> boot allows us to discover existing long branch trampolines. If we want = to >> avoid it, we need to note down those locations during build time. >>=20 >> Do you have a different approach in mind? >=20 > If you put _mcount in a separate section then the compiler cannot tell > where it is and is forced to always emit a long branch trampoline. >=20 > Does that help? That's an interesting thought. Depending on the type of trampoline the=20 compiler emits, I might be able to use this approach. We will still need=20 objtool on powerpc so that we can note down those trampoline locations. Thanks, Naveen