[PATCH v2 0/4] nios2: Add architecture support for clone3

[Simon Schuster via B4 Relay <devnull+schuster.simon.siemens-energy.com@kernel.org>]

This series adds support for the clone3 system call to the nios2
architecture. This addresses the build-time warning "warning: clone3()
entry point is missing, please fix" introduced in 505d66d1abfb9
("clone3: drop __ARCH_WANT_SYS_CLONE3 macro"). The implementation passes
the relevant clone3 tests of kselftest when applied on top of
next-20250815:

	./run_kselftest.sh
	TAP version 13
	1..4
	# selftests: clone3: clone3
	ok 1 selftests: clone3: clone3
	# selftests: clone3: clone3_clear_sighand
	ok 2 selftests: clone3: clone3_clear_sighand
	# selftests: clone3: clone3_set_tid
	ok 3 selftests: clone3: clone3_set_tid
	# selftests: clone3: clone3_cap_checkpoint_restore
	ok 4 selftests: clone3: clone3_cap_checkpoint_restore

The series also includes a small patch to kernel/fork.c that ensures
that clone_flags are passed correctly on architectures where unsigned
long is insufficient to store the u64 clone_flags. It is marked as a fix
for stable backporting.

As requested, in v2, this series now further tries to correct this type
error throughout the whole code base. Thus, it now touches a larger
number of subsystems and all architectures.

Therefore, another test was performed for ARCH=x86_64 (as a
representative for 64-bit architectures). Here, the series builds cleanly
without warnings on defconfig with CONFIG_SECURITY_APPARMOR=y and
CONFIG_SECURITY_TOMOYO=y (to compile-check the LSM-related changes).
The build further successfully passes testing/selftests/clone3 (with the
patch from 20241105062948.1037011-1-zhouyuhang1010@163.com to prepare
clone3_cap_checkpoint_restore for compatibility with the newer libcap
version on my system).

Is there any option to further preflight check this patch series via
lkp/KernelCI/etc. for a broader test across architectures, or is this
degree of testing sufficient to eventually get the series merged?

N.B.: The series is not checkpatch clean right now:
 - include/linux/cred.h, include/linux/mnt_namespace.h:
   function definition arguments without identifier name
 - include/trace/events/task.h:
   space prohibited after that open parenthesis

I did not fix these warnings to keep my changes minimal and reviewable,
as the issues persist throughout the files and they were not introduced
by me; I only followed the existing code style and just replaced the
types. If desired, I'd be happy to make the changes in a potential v3,
though.

Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
---
Changes in v2:
- Introduce "Fixes:" and "Cc: stable@vger.kernel.org" where necessary
- Factor out "Fixes:" when adapting the datatype of clone_flags for
  easier backports
- Fix additional instances where `unsigned long` clone_flags is used
- Reword commit message to make it clearer that any 32-bit arch is
  affected by this bug
- Link to v1: https://lore.kernel.org/r/20250821-nios2-implement-clone3-v1-0-1bb24017376a@siemens-energy.com

---
Simon Schuster (4):
      copy_sighand: Handle architectures where sizeof(unsigned long) < sizeof(u64)
      copy_process: pass clone_flags as u64 across calltree
      arch: copy_thread: pass clone_flags as u64
      nios2: implement architecture-specific portion of sys_clone3

 arch/alpha/kernel/process.c       |  2 +-
 arch/arc/kernel/process.c         |  2 +-
 arch/arm/kernel/process.c         |  2 +-
 arch/arm64/kernel/process.c       |  2 +-
 arch/csky/kernel/process.c        |  2 +-
 arch/hexagon/kernel/process.c     |  2 +-
 arch/loongarch/kernel/process.c   |  2 +-
 arch/m68k/kernel/process.c        |  2 +-
 arch/microblaze/kernel/process.c  |  2 +-
 arch/mips/kernel/process.c        |  2 +-
 arch/nios2/include/asm/syscalls.h |  1 +
 arch/nios2/include/asm/unistd.h   |  2 --
 arch/nios2/kernel/entry.S         |  6 ++++++
 arch/nios2/kernel/process.c       |  2 +-
 arch/nios2/kernel/syscall_table.c |  1 +
 arch/openrisc/kernel/process.c    |  2 +-
 arch/parisc/kernel/process.c      |  2 +-
 arch/powerpc/kernel/process.c     |  2 +-
 arch/riscv/kernel/process.c       |  2 +-
 arch/s390/kernel/process.c        |  2 +-
 arch/sh/kernel/process_32.c       |  2 +-
 arch/sparc/kernel/process_32.c    |  2 +-
 arch/sparc/kernel/process_64.c    |  2 +-
 arch/um/kernel/process.c          |  2 +-
 arch/x86/include/asm/fpu/sched.h  |  2 +-
 arch/x86/include/asm/shstk.h      |  4 ++--
 arch/x86/kernel/fpu/core.c        |  2 +-
 arch/x86/kernel/process.c         |  2 +-
 arch/x86/kernel/shstk.c           |  2 +-
 arch/xtensa/kernel/process.c      |  2 +-
 block/blk-ioc.c                   |  2 +-
 fs/namespace.c                    |  2 +-
 include/linux/cgroup.h            |  4 ++--
 include/linux/cred.h              |  2 +-
 include/linux/iocontext.h         |  6 +++---
 include/linux/ipc_namespace.h     |  4 ++--
 include/linux/lsm_hook_defs.h     |  2 +-
 include/linux/mnt_namespace.h     |  2 +-
 include/linux/nsproxy.h           |  2 +-
 include/linux/pid_namespace.h     |  4 ++--
 include/linux/rseq.h              |  4 ++--
 include/linux/sched/task.h        |  2 +-
 include/linux/security.h          |  4 ++--
 include/linux/sem.h               |  4 ++--
 include/linux/time_namespace.h    |  4 ++--
 include/linux/uprobes.h           |  4 ++--
 include/linux/user_events.h       |  4 ++--
 include/linux/utsname.h           |  4 ++--
 include/net/net_namespace.h       |  4 ++--
 include/trace/events/task.h       |  6 +++---
 ipc/namespace.c                   |  2 +-
 ipc/sem.c                         |  2 +-
 kernel/cgroup/namespace.c         |  2 +-
 kernel/cred.c                     |  2 +-
 kernel/events/uprobes.c           |  2 +-
 kernel/fork.c                     | 10 +++++-----
 kernel/nsproxy.c                  |  4 ++--
 kernel/pid_namespace.c            |  2 +-
 kernel/sched/core.c               |  4 ++--
 kernel/sched/fair.c               |  2 +-
 kernel/sched/sched.h              |  4 ++--
 kernel/time/namespace.c           |  2 +-
 kernel/utsname.c                  |  2 +-
 net/core/net_namespace.c          |  2 +-
 security/apparmor/lsm.c           |  2 +-
 security/security.c               |  2 +-
 security/selinux/hooks.c          |  2 +-
 security/tomoyo/tomoyo.c          |  2 +-
 68 files changed, 95 insertions(+), 89 deletions(-)
---
base-commit: 1357b2649c026b51353c84ddd32bc963e8999603
change-id: 20250818-nios2-implement-clone3-7f252c20860b

Best regards,
-- 
Simon Schuster <schuster.simon@siemens-energy.com>