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Rao" Subject: Re: [PATCH] kexec_file: Drop pr_err in weak implementations of arch_kexec_apply_relocations[_add] To: Baoquan He References: <20220425174128.11455-1-naveen.n.rao@linux.vnet.ibm.com> In-Reply-To: User-Agent: astroid/4d6b06ad (https://github.com/astroidmail/astroid) Message-Id: <1652782155.56t7mah8ib.naveen@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 3VF1AMtnPOAhP9HZz_RcBqZuj551GDIq X-Proofpoint-GUID: GMmMoVdAmJIpiPaER6o347wEx1mnozOB Content-Transfer-Encoding: quoted-printable X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-17_01,2022-05-17_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxlogscore=999 bulkscore=0 lowpriorityscore=0 clxscore=1015 priorityscore=1501 mlxscore=0 adultscore=0 malwarescore=0 impostorscore=0 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205170060 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: linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, Eric Biederman , linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Baoquan He wrote: > On 04/25/22 at 11:11pm, Naveen N. Rao wrote: >> kexec_load_purgatory() can fail for many reasons - there is no need to >> print an error when encountering unsupported relocations. >>=20 >> This solves a build issue on powerpc with binutils v2.36 and newer [1]. >> Since commit d1bcae833b32f1 ("ELF: Don't generate unused section >> symbols") [2], binutils started dropping section symbols that it thought >=20 > I am not familiar with binutils, while wondering if this exists in other > ARCHes except of ppc. Arm64 doesn't have the ARCH override either, do we > have problem with it? I'm not aware of this specific file causing a problem on other=20 architectures - perhaps the config options differ enough. There are=20 however more reports of similar issues affecting other architectures=20 with the llvm integrated assembler: https://github.com/ClangBuiltLinux/linux/issues/981 >=20 >> were unused. This isn't an issue in general, but with kexec_file.c, gcc >> is placing kexec_arch_apply_relocations[_add] into a separate >> .text.unlikely section and the section symbol ".text.unlikely" is being >> dropped. Due to this, recordmcount is unable to find a non-weak symbol >=20 > But arch_kexec_apply_relocations_add is weak symbol on ppc. Yes. Note that it is just the section symbol that gets dropped. The=20 section is still present and will continue to hold the symbols for the=20 functions themselves. >=20 >> in .text.unlikely to generate a relocation record against. Dropping >> pr_err() calls results in these functions being left in .text section, >=20 > Why dropping pr_err() can make arch_kexec_apply_relocations_add put in > .text? I'm not actually sure, though Josh suspected that printk() might be=20 cold: http://lkml.kernel.org/r/20210214155147.3owdimqv2lyhu6by@treble - Naveen