by Alexandre Ghiti

[permalink] [raw]

Subject: Re: [PATCH v4 00/24] Remove COMMAND_LINE_SIZE from uapi

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/[email protected]/>:
>> * 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/[email protected]/>:
>> * Fix sh, csky and ia64 builds, as reported by kernel test robot
>>
>> Changes since v1
>> <https://lore.kernel.org/all/[email protected]/>:
>> * 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