Re: [PATCH v5 00/26] Remove COMMAND_LINE_SIZE from uapi

Hi Arnd,

On Mon, Mar 6, 2023 at 11:05 AM Alexandre Ghiti <[email protected]> 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 v4 <https://lore.kernel.org/all/[email protected]/>:
> * Add my own SoB as suggested by Geert
> * Add riscv patches as suggested by Björn
> * Remove "WITH Linux-syscall-note" from new setup.h not in uapi/, as
>   suggested by Greg KH, his quoted answer below:
>
> "The "syscall note" makes no sense at all for any files not in the uapi/
> directory, so you can remove it just fine as that WITH doesn't mean
> anything _UNLESS_ the file is in the uapi directory."
>
> 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
>
> Alexandre Ghiti (2):
>   riscv: Remove COMMAND_LINE_SIZE from uapi
>   riscv: Remove empty <uapi/asm/setup.h>
>
> 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    |  2 +-
>  arch/powerpc/include/asm/setup.h              |  2 +-
>  arch/powerpc/include/uapi/asm/setup.h         |  7 -----
>  arch/riscv/include/asm/setup.h                |  7 +++++
>  arch/riscv/include/uapi/asm/setup.h           |  8 ------
>  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    |  2 +-
>  include/asm-generic/Kbuild                    |  1 +
>  include/{uapi => }/asm-generic/setup.h        |  0
>  include/uapi/asm-generic/Kbuild               |  1 -
>  34 files changed, 40 insertions(+), 143 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 (63%)
>  delete mode 100644 arch/powerpc/include/uapi/asm/setup.h
>  create mode 100644 arch/riscv/include/asm/setup.h
>  delete mode 100644 arch/riscv/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 (84%)
>  rename include/{uapi => }/asm-generic/setup.h (100%)
>
> --
> 2.37.2
>

I don't see this series in 6.4-rc1, I don't mean to bother you, I just
want to make sure it did not get lost :)

Thanks,

Alex