From:   Alexandre Ghiti <alexghiti@rivosinc.com>
To:     Jonathan Corbet <corbet@lwn.net>,
        Richard Henderson <richard.henderson@linaro.org>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        Vineet Gupta <vgupta@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Michal Simek <monstr@monstr.eu>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        "James E . J . Bottomley" <James.Bottomley@HansenPartnership.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>,
        "David S . Miller" <davem@davemloft.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>, Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, 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@lists.linux-m68k.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
Cc:     Alexandre Ghiti <alexghiti@rivosinc.com>
Subject: [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi
Date:   Tue, 14 Feb 2023 08:49:01 +0100
Message-Id: <20230214074925.228106-1-alexghiti@rivosinc.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Changes since v2 <https://lore.kernel.org/all/20221211061358.28035-1-palmer@rivosinc.com/>:
* Fix sh, csky and ia64 builds, as reported by kernel test robot

Changes since v1 <https://lore.kernel.org/all/20210423025545.313965-1-palmer@dabbelt.com/>:
* Touches every arch.

base-commit-tag: next-20230207

Palmer Dabbelt (24):
  alpha: Remove COMMAND_LINE_SIZE from uapi
  arm64: Remove COMMAND_LINE_SIZE from uapi
  arm: Remove COMMAND_LINE_SIZE from uapi
  ia64: Remove COMMAND_LINE_SIZE from uapi
  m68k: Remove COMMAND_LINE_SIZE from uapi
  microblaze: Remove COMMAND_LINE_SIZE from uapi
  mips: Remove COMMAND_LINE_SIZE from uapi
  parisc: Remove COMMAND_LINE_SIZE from uapi
  powerpc: Remove COMMAND_LINE_SIZE from uapi
  sparc: Remove COMMAND_LINE_SIZE from uapi
  xtensa: Remove COMMAND_LINE_SIZE from uapi
  asm-generic: Remove COMMAND_LINE_SIZE from uapi
  alpha: Remove empty <uapi/asm/setup.h>
  arc: Remove empty <uapi/asm/setup.h>
  m68k: Remove empty <uapi/asm/setup.h>
  arm64: Remove empty <uapi/asm/setup.h>
  microblaze: Remove empty <uapi/asm/setup.h>
  sparc: Remove empty <uapi/asm/setup.h>
  parisc: Remove empty <uapi/asm/setup.h>
  x86: Remove empty <uapi/asm/setup.h>
  xtensa: Remove empty <uapi/asm/setup.h>
  powerpc: Remove empty <uapi/asm/setup.h>
  mips: Remove empty <uapi/asm/setup.h>
  s390: Remove empty <uapi/asm/setup.h>

 .../admin-guide/kernel-parameters.rst         |  2 +-
 arch/alpha/include/asm/setup.h                |  4 +--
 arch/alpha/include/uapi/asm/setup.h           |  7 -----
 arch/arc/include/asm/setup.h                  |  1 -
 arch/arc/include/uapi/asm/setup.h             |  6 -----
 arch/arm/include/asm/setup.h                  |  1 +
 arch/arm/include/uapi/asm/setup.h             |  2 --
 arch/arm64/include/asm/setup.h                |  3 ++-
 arch/arm64/include/uapi/asm/setup.h           | 27 -------------------
 arch/ia64/include/asm/setup.h                 | 10 +++++++
 arch/ia64/include/uapi/asm/setup.h            |  6 ++---
 arch/loongarch/include/asm/setup.h            |  2 +-
 arch/m68k/include/asm/setup.h                 |  3 +--
 arch/m68k/include/uapi/asm/setup.h            | 17 ------------
 arch/microblaze/include/asm/setup.h           |  2 +-
 arch/microblaze/include/uapi/asm/setup.h      | 20 --------------
 arch/mips/include/asm/setup.h                 |  3 ++-
 arch/mips/include/uapi/asm/setup.h            |  8 ------
 arch/parisc/include/{uapi => }/asm/setup.h    |  0
 arch/powerpc/include/asm/setup.h              |  2 +-
 arch/powerpc/include/uapi/asm/setup.h         |  7 -----
 arch/s390/include/asm/setup.h                 |  1 -
 arch/s390/include/uapi/asm/setup.h            |  1 -
 arch/sh/include/asm/setup.h                   |  2 +-
 arch/sparc/include/asm/setup.h                |  6 ++++-
 arch/sparc/include/uapi/asm/setup.h           | 16 -----------
 arch/x86/include/asm/setup.h                  |  2 --
 arch/x86/include/uapi/asm/setup.h             |  1 -
 arch/xtensa/include/{uapi => }/asm/setup.h    |  0
 include/asm-generic/Kbuild                    |  1 +
 include/{uapi => }/asm-generic/setup.h        |  0
 include/uapi/asm-generic/Kbuild               |  1 -
 32 files changed, 31 insertions(+), 133 deletions(-)
 delete mode 100644 arch/alpha/include/uapi/asm/setup.h
 delete mode 100644 arch/arc/include/uapi/asm/setup.h
 delete mode 100644 arch/arm64/include/uapi/asm/setup.h
 create mode 100644 arch/ia64/include/asm/setup.h
 delete mode 100644 arch/m68k/include/uapi/asm/setup.h
 delete mode 100644 arch/microblaze/include/uapi/asm/setup.h
 delete mode 100644 arch/mips/include/uapi/asm/setup.h
 rename arch/parisc/include/{uapi => }/asm/setup.h (100%)
 delete mode 100644 arch/powerpc/include/uapi/asm/setup.h
 delete mode 100644 arch/s390/include/uapi/asm/setup.h
 delete mode 100644 arch/sparc/include/uapi/asm/setup.h
 delete mode 100644 arch/x86/include/uapi/asm/setup.h
 rename arch/xtensa/include/{uapi => }/asm/setup.h (100%)
 rename include/{uapi => }/asm-generic/setup.h (100%)

-- 
2.37.2