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Tue, 21 Oct 2025 13:16:36 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 56C1620043; Tue, 21 Oct 2025 13:16:36 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A8E0F20040; Tue, 21 Oct 2025 13:16:35 +0000 (GMT) Received: from osiris (unknown [9.155.211.25]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 21 Oct 2025 13:16:35 +0000 (GMT) Date: Tue, 21 Oct 2025 15:16:33 +0200 From: Heiko Carstens To: Geert Uytterhoeven Cc: Doug Anderson , Randy Dunlap , linux-kernel@vger.kernel.org, Andrew Chant , Alexander Shishkin , Andrew Morton , Brian Gerst , Christian Brauner , Francesco Valla , Guo Weikang , Huacai Chen , Jan Hendrik Farr , Jeff Xu , Kees Cook , Masahiro Yamada , Michal =?iso-8859-1?Q?Koutn=FD?= , Miguel Ojeda , "Mike Rapoport (Microsoft)" , Nathan Chancellor , Peter Zijlstra , Shakeel Butt , Tejun Heo , Thomas Gleixner , Thomas =?iso-8859-1?Q?Wei=DFschuh?= , "Uladzislau Rezki (Sony)" , Sven Schnelle , linux-s390 Subject: Re: [PATCH] init/main.c: Wrap long kernel cmdline when printing to logs Message-ID: <20251021131633.26700Dd6-hca@linux.ibm.com> References: <20251019100605.1.I095f1e2c6c27f9f4de0b4841f725f356c643a13f@changeid> <2d514d61-121d-44fc-aec7-637dd0920de8@infradead.org> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: I-TIS4kR6Ou-Mb55i_Ay1degV3_Mx5Fl X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDE4MDAyMiBTYWx0ZWRfX6yB+urCIgoIi 6bgTPbTtxdzNQuDNbAlPfWyFzsZP0czUuCRqBrGQ88yR0qkjrAKBbvZFihPM5atVCrL1llTI+4E yFBwgZI0xe/HCzDvfZNVZ+8m9FiJCObDMlhwTgFw2D7vXWN5wHTFrscIsKQxg+BdtX++42p8u3a yTeRh81CNcqc4r8/eat0UTCsZ4yQNAQuI4oLrXukmeHQmfu9Dm1LRnlZvCB0IIj5hbjLbxV7ZoX BjeVDEU+uwGEc2V7KalslNq9VLJVmwGBkgtd3JFns3p9crNjSOnNQbJu/80R9aauto1pZoW3YsU gEPo2uFohFGSMDV+qM2UuWXJFODG1WHy4N7beZGdchGF8Qp+VF4qFija1D5Q9FrxZclXZQQyGlh Pruam5GVj+kawSChWFczG/9Qv9qq3Q== X-Authority-Analysis: v=2.4 cv=MIJtWcZl c=1 sm=1 tr=0 ts=68f787b7 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=cm27Pg_UAAAA:8 a=tBb2bbeoAAAA:8 a=EHDhFRfyqMhxxtNxYo4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=Oj-tNtZlA1e06AYgeCfH:22 a=nl4s5V0KI7Kw-pW0DWrs:22 a=pHzHmUro8NiASowvMSCR:22 a=xoEH_sTeL_Rfw54TyV31:22 X-Proofpoint-ORIG-GUID: vs11V-hue1blIi2oIbSzP3wDj86PAYS3 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-21_01,2025-10-13_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 phishscore=0 lowpriorityscore=0 adultscore=0 clxscore=1011 impostorscore=0 bulkscore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510180022 On Tue, Oct 21, 2025 at 09:05:48AM +0200, Geert Uytterhoeven wrote: > On Mon, 20 Oct 2025 at 18:04, Doug Anderson wrote: > > On Mon, Oct 20, 2025 at 8:42 AM Geert Uytterhoeven wrote: > > > On Mon, 20 Oct 2025 at 17:33, Doug Anderson wrote: > > > > Printing the command line to the kernel log buffer is one of the very > > > > rare cases where: > > > > * There's a legitimate reason to print a (potentially) very long > > > > string to the kernel buffer. > > > > > > arch/s390/Kconfig: > > > > > > config COMMAND_LINE_SIZE > > > int "Maximum size of kernel command line" > > > default 4096 > > > range 896 1048576 > > > > > > Yummy... > > > > Wow, what are they expecting to stuff in there? An encoded initramfs > > or something? I kinda feel like the 1MB number isn't something anyone > > expects but is a number picked to effectively be "unlimited". > > Dunno, commit 622021cd6c560ce7 ("s390: make command line configurable") > lacks the "why" part. That was just a follow-on patch of commit 5ecb2da660ab ("s390: support command lines longer than 896 bytes") which solved the real problem with a too short maximum command line size back then. In order to never have to deal with this sort of problem again it was made configurable. But I doubt that anybody will change the default ever.