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Peter Anvin" To: Palmer Dabbelt , hca@linux.ibm.com CC: geert@linux-m68k.org, alexghiti@rivosinc.com, corbet@lwn.net, Richard Henderson , ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, Catalin Marinas , Will Deacon , chenhuacai@kernel.org, kernel@xen0n.name, monstr@monstr.eu, tsbogend@alpha.franken.de, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, Paul Walmsley , aou@eecs.berkeley.edu, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.osdn.me, dalias@libc.org, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, chris@zankel.net, jcmvbkbc@gmail.com, Arnd Bergmann , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org Subject: Re: [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi User-Agent: K-9 Mail for Android In-Reply-To: References: Message-ID: <21F95EC4-71EA-4154-A7DC-8A5BA54F174B@zytor.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230302_115423_600925_2CCC5F1F X-CRM114-Status: GOOD ( 29.17 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org On March 1, 2023 7:17:18 PM PST, Palmer Dabbelt wrote: >On Tue, 14 Feb 2023 01:19:02 PST (-0800), hca@linux.ibm.com wrote: >> On Tue, Feb 14, 2023 at 09:58:17AM +0100, Geert Uytterhoeven wrote: >>> Hi Heiko, >>> >>> On Tue, Feb 14, 2023 at 9:39 AM Heiko Carstens wrote: >>> > 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. > >Thanks, I guess I'd missed that one. At some point I think there was some discussion of making this a Kconfig for everyone, which seems reasonable to me -- our use case for this being extended is syzkaller, but we're sort of just picking a value that's big enough for now and running with it. > >Probably best to get it out of uapi first, though, as that way at least it's clear that it's not uABI. > >>> Commit 622021cd6c560ce7 ("s390: make command line configurable"), >>> I assume? >> >> Yes, sorry for that. I got distracted while writing and used the wrong >> branch to look this up. > >Alex: Probably worth adding that to the list in the cover letter as it looks like you were planning on a v4 anyway (which I guess you now have to do, given that I just added the issue to RISC-V). The only use that is uapi is the *default* length of the command line if the kernel header doesn't include it (in the case of x86, it is in the bzImage header, but that is atchitecture- or even boot format-specific.) _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc