linux-stable.git/arch/s390/kernel/process.c, branch linux-rolling-lts

s390/process: Fix kernel thread function pointer type

2026-07-24T14:16:08+00:00

[ Upstream commit d0478f5d3cba1095bfdeb43a9b063c10cdebef14 ]

In case of a kernel thread __ret_from_fork() calls the specified function
indirectly. Fix the kernel thread function pointer, since kernel threads
return an int instead of void.

Fixes: 56e62a737028 ("s390: convert to generic entry")
Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev 
Signed-off-by: Sasha Levin

arch: copy_thread: pass clone_flags as u64

2025-09-01T13:31:34+00:00

With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.

While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.

Thus, this commit fixes all relevant interfaces of the copy_thread
function that is called from copy_process to consistently pass
clone_flags as u64, so that no truncation to 32-bit integers occurs on
32-bit architectures.

Signed-off-by: Simon Schuster 
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-3-53fcf5577d57@siemens-energy.com
Fixes: c5febea0956fd387 ("fork: Pass struct kernel_clone_args into copy_thread")
Acked-by: Guo Ren (Alibaba Damo Academy) 
Acked-by: Andreas Larsson  # sparc
Acked-by: David Hildenbrand 
Acked-by: Geert Uytterhoeven  # m68k
Reviewed-by: Arnd Bergmann 
Signed-off-by: Christian Brauner

s390: Remove unnecessary include

2025-06-17T16:18:02+00:00

Remove include  from all files which do not contain an
EXPORT_SYMBOL().

See commit 7d95680d64ac ("scripts/misc-check: check unnecessary #include
 when W=1") for more details.

Acked-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev

s390: Replace S390_lowcore by get_lowcore()

2024-06-18T15:01:33+00:00

Replace all S390_lowcore usages in arch/s390/ by get_lowcore().

Acked-by: Heiko Carstens 
Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

s390/fpu: Remove comment about TIF_FPU

2024-05-14T11:37:08+00:00

It has been removed in commit 2c6b96762fbd ("s390/fpu: remove TIF_FPU"),
so we should not mention TIF_FPU in the comment here anymore. Since the
remaining parts of the comment just document the obvious fact that
save_user_fpu_regs() saves the FPU state, simply remove the comment now
completely.

Signed-off-by: Thomas Huth 
Acked-by: Heiko Carstens 
Link: https://lore.kernel.org/r/20240503080648.81461-1-thuth@redhat.com
Signed-off-by: Alexander Gordeev

s390/fpu: remove regs member from struct fpu

2024-02-16T13:30:16+00:00

KVM was the only user which modified the regs pointer in struct fpu. Remove
the pointer and convert the rest of the core fpu code to directly access
the save area embedded within struct fpu.

Reviewed-by: Claudio Imbrenda 
Signed-off-by: Heiko Carstens

s390/fpu: make kernel fpu context preemptible

2024-02-16T13:30:15+00:00

Make the kernel fpu context preemptible. Add another fpu structure to the
thread_struct, and use it to save and restore the kernel fpu context if its
task uses fpu registers when it is preempted.

Reviewed-by: Claudio Imbrenda 
Signed-off-by: Heiko Carstens

s390/fpu: rename save_fpu_regs() to save_user_fpu_regs(), etc

2024-02-16T13:30:15+00:00

Rename save_fpu_regs(), load_fpu_regs(), and struct thread_struct's fpu
member to save_user_fpu_regs(), load_user_fpu_regs(), and ufpu. This way
the function and variable names reflect for which context they are supposed
to be used.

This large and trivial conversion is a prerequisite for making the kernel
fpu usage preemptible.

Reviewed-by: Claudio Imbrenda 
Signed-off-by: Heiko Carstens

s390/fpu: convert FPU CIF flag to regular TIF flag

2024-02-16T13:30:15+00:00

The FPU state, as represented by the CIF_FPU flag reflects the FPU state of
a task, not the CPU it is running on. Therefore convert the flag to a
regular TIF flag.

This removes the magic in switch_to() where a save_fpu_regs() call for the
currently (previous) running task sets the per-cpu CIF_FPU flag, which is
required to restore FPU register contents of the next task, when it returns
to user space.

Signed-off-by: Heiko Carstens

s390/fpu: provide and use lfpc, sfpc, and stfpc inline assemblies

2024-02-16T13:30:15+00:00

Instead of open-coding lfpc, sfpc, and stfpc inline assemblies at
several locations, provide an fpu_* function for each instruction and
use the function instead.

Reviewed-by: Claudio Imbrenda 
Signed-off-by: Heiko Carstens