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Tue, 14 Feb 2023 08:38:49 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DDF1E20043; Tue, 14 Feb 2023 08:38:48 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C3EAF20040; Tue, 14 Feb 2023 08:38:47 +0000 (GMT) Received: from osiris (unknown [9.152.212.244]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 14 Feb 2023 08:38:47 +0000 (GMT) Date: Tue, 14 Feb 2023 09:38:47 +0100 From: Heiko Carstens To: Alexandre Ghiti Subject: Re: [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi Message-ID: References: <20230214074925.228106-1-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230214074925.228106-1-alexghiti@rivosinc.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: lcWVAyn8KN60Dj6qJ5LWCkwvnMHsQyNY X-Proofpoint-GUID: QnuEgtAeE2k8CuQJG5mickOtwsFFWUEl X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.170.22 definitions=2023-02-14_05,2023-02-13_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 spamscore=0 phishscore=0 priorityscore=1501 impostorscore=0 adultscore=0 mlxscore=0 bulkscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302140067 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: Rich Felker , linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org, Catalin Marinas , Dave Hansen , x86@kernel.org, linux-mips@vger.kernel.org, "James E . J . Bottomley" , Max Filippov , "H . Peter Anvin" , sparclinux@vger.kernel.org, WANG Xuerui , Will Deacon , Alexander Gordeev , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, Arnd Bergmann , Yoshinori Sato , Jonathan Corbet , linux-sh@vger.kernel.org, Helge Deller , Huacai Chen , Russell King , Ingo Molnar , Geert Uytterhoeven , Vineet Gupta , Matt Turner , Christian Borntraeger , linux-xtensa@linux-xtensa.org, Albert Ou , Vasily Gorbik , Richard Henderson , Nicholas Piggin , linux-m68k@lists.linux-m68k.org, Ivan Kokshaysky , loongarch@lists.linux.dev, Paul Walmsley , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Chris Zankel , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Palmer Dabbelt , Sven Schnelle , linux-alpha@vger.kernel.org, Borislav Petkov , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Feb 14, 2023 at 08:49:01AM +0100, Alexandre Ghiti wrote: > This all came up in the context of increasing COMMAND_LINE_SIZE in the > RISC-V port. In theory that's a UABI break, as COMMAND_LINE_SIZE is the > maximum length of /proc/cmdline and userspace could staticly rely on > that to be correct. > > Usually I wouldn't mess around with changing this sort of thing, but > PowerPC increased it with a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE > to 2048"). There are also a handful of examples of COMMAND_LINE_SIZE > increasing, but they're from before the UAPI split so I'm not quite sure > what that means: e5a6a1c90948 ("powerpc: derive COMMAND_LINE_SIZE from > asm-generic"), 684d2fd48e71 ("[S390] kernel: Append scpdata to kernel > boot command line"), 22242681cff5 ("MIPS: Extend COMMAND_LINE_SIZE"), > and 2b74b85693c7 ("sh: Derive COMMAND_LINE_SIZE from > asm-generic/setup.h."). > > It seems to me like COMMAND_LINE_SIZE really just shouldn't have been > part of the uapi to begin with, and userspace should be able to handle > /proc/cmdline of whatever length it turns out to be. I don't see any > references to COMMAND_LINE_SIZE anywhere but Linux via a quick Google > search, but that's not really enough to consider it unused on my end. > > The feedback on the v1 seemed to indicate that COMMAND_LINE_SIZE really > shouldn't be part of uapi, so this now touches all the ports. I've > tried to split this all out and leave it bisectable, but I haven't > tested it all that aggressively. Just to confirm this assumption a bit more: that's actually the same conclusion that we ended up with when commit 3da0243f906a ("s390: make command line configurable") went upstream.