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@xxxxxxxxxxxx/>:
* 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@xxxxxxxxxxxx/>:
* Fix sh, csky and ia64 builds, as reported by kernel test robot
Changes since v1 <https://lore.kernel.org/all/20210423025545.313965-1-palmer@xxxxxxxxxxx/>:
* 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
