[PATCH v4 00/24] Remove COMMAND_LINE_SIZE from uapi

[Alexandre Ghiti]

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