[PATCH v4 00/24] Remove COMMAND_LINE_SIZE from uapi

[Alexandre Ghiti]

On 3/2/23 11:06, Alexandre Ghiti wrote:
> Hi Arnd,
>
> On 3/2/23 10:35, 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.
>>
>> This issue was already considered in s390 and they reached the same
>> conclusion in commit 622021cd6c56 ("s390: make command line
>> configurable").
>>
>> 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 v3 
>> <https://lore.kernel.org/all/20230214074925.228106-1-alexghiti@rivosinc.com/>:
>> * Added RB/AB
>> * Added a mention to commit 622021cd6c56 ("s390: make command line
>>    configurable") in the cover letter
>>
>> 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%)
>>
> Björn noticed that I should also remove the command line size for 
> riscv since it was picked up in 6.3 by Palmer...I send a v6 right now, 
> sorry about that.
>
> Alex
>

Hmmm when implementing the riscv patch, I noticed that the patches that 
introduce a new include/asm/setup.h file add the following SPDX header:

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

To me we should not add "WITH Linux-syscall-note" as this header is not 
part of the user visible headers: any opinion before I send the v5?

Thanks,

Alex