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Thu, 15 Feb 2024 10:50:40 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6AB8720043; Thu, 15 Feb 2024 10:50:38 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 001502004B; Thu, 15 Feb 2024 10:50:37 +0000 (GMT) Received: from localhost (unknown [9.171.10.232]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 15 Feb 2024 10:50:37 +0000 (GMT) Date: Thu, 15 Feb 2024 11:50:36 +0100 From: Vasily Gorbik To: Sumanth Korikkar Cc: linux-s390@vger.kernel.org, jpoimboe@kernel.org, joe.lawrence@redhat.com, hca@linux.ibm.com, iii@linux.ibm.com, agordeev@linux.ibm.com Subject: Re: [PATCH 1/4] s390/vdso64: filter out munaligned-symbols flag for vdso Message-ID: References: <20240213104707.673053-1-sumanthk@linux.ibm.com> <20240213104707.673053-2-sumanthk@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240213104707.673053-2-sumanthk@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: MKJA6GuuViohE2hMm7JImk3iveRw7KDQ X-Proofpoint-GUID: XfT_nh4YExtRFc3GE5V4j4Pqc2dkvt4b X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-15_10,2024-02-14_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 adultscore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 malwarescore=0 spamscore=0 priorityscore=1501 mlxlogscore=921 suspectscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2402150086 On Tue, Feb 13, 2024 at 11:47:04AM +0100, Sumanth Korikkar wrote: > Gcc recently implemented an optimization [1] for loading symbols without > explicit alignment, aligning with the IBM Z ELF ABI. This ABI mandates > symbols to reside on a 2-byte boundary, enabling the use of the larl > instruction. However, kernel linker scripts may still generate unaligned > symbols. To address this, a new -munaligned-symbols option has been > introduced [2] in recent gcc versions. > > [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-June/622872.html > [2] https://gcc.gnu.org/pipermail/gcc-patches/2023-August/625986.html > > However, when -munaligned-symbols is used in vdso code, it leads to the > following compilation error: > `.data.rel.ro.local' referenced in section `.text' of > arch/s390/kernel/vdso64/vdso64_generic.o: defined in discarded section > `.data.rel.ro.local' of arch/s390/kernel/vdso64/vdso64_generic.o > > vdso linker script discards .data section to make it lightweight. > However, -munaligned-symbols in vdso object files references literal > pool and accesses _vdso_data. Hence, compile vdso code without > -munaligned-symbols. This means in the future, vdso code should deal > with alignment of newly introduced unaligned linker symbols. > > Signed-off-by: Sumanth Korikkar > --- > arch/s390/kernel/vdso64/Makefile | 1 + > 1 file changed, 1 insertion(+) Acked-by: Vasily Gorbik