From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko Carstens Subject: Re: [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi Date: Tue, 14 Feb 2023 09:38:47 +0100 Message-ID: References: <20230214074925.228106-1-alexghiti@rivosinc.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=N9Dr6deziRiYIJA5gCEMcSyyPwD9fDBGorSmYJxpwHQ=; b=SketelRUP0tC08 LaCJJ0vPkkN9aPmdTcxD1/NtH9TOLgFHEumAikpKXKxTN4OHmkiBFokjjLEre9Qu4HlugTLqJOZHU BO0PVcHBW0gL/JVBa8YgI8q82liHhQDktn3RzLV0FBpYuIWwHEHhJLOPFSbrENq+UK2iA+huBKXf+ cuZ5/o5gch7tYlQSWUpS1QAZlYx7wekDhObakEzJQAjnIaTq6rXgRUU3+r5rnikqdvObKEpDvHIH/ j9imb0J51DYJR+QtdZZy86qU/4yoQYchfmjS6MRWYwMG8QQdz4FaQV6akXBMjX58fR0OaXzi5SbZT jWuK7o5KCthAe9YrcOlQ==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=pp1; bh=XmTTRTqN8QHhuqqaK0B4wcZMFk6wbx4+9SlCVYUudEg=; b=q0CFhD00GHRgiAn5Lc7+9XPoIXhbH37jo9LPP5gO0FR/vTvQM2oqGpmnUzQ/izmDF9v0 KdAdBX+lzRH997zibc6I+ZDhX9NkR3s4PeteSiWnk3qMLqykhF7VHts/j4ounccd62iV 6zcE2d9N3AcFvu42RVPJGqHk19n5kfAfYcELyf5vZX21pLHO9cWuVpRgVcF4ehkFPB9o K9L59Nu09a5yT/SgLgfiy57OTzuJRb0tm23G7nl+ZAEOvsDYZRkFKkNDE7G+veUt0tTq kDWPNL6pCGB2ooJtc34IbfhYfLJPh8EqpCM4gyBz9pzkOASeQq1W919Hg2daScb2Sld3 rg== Content-Disposition: inline In-Reply-To: <20230214074925.228106-1-alexghiti@rivosinc.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane-mx.org@lists.infradead.org To: Alexandre Ghiti Cc: Jonathan Corbet , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Geert Uytterhoeven , Michal Simek , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Pa 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.