powerpc: Introduce syscall exit arch functions

Add PowerPC-specific implementations of the generic syscall exit hooks
used by the generic entry/exit framework:

 - arch_exit_to_user_mode_work_prepare()
 - arch_exit_to_user_mode_work()

These helpers handle user state restoration when returning from the
kernel to userspace, including FPU/VMX/VSX state, transactional memory,
KUAP restore, and per-CPU accounting.

Additionally, move check_return_regs_valid() from interrupt.c to
interrupt.h so it can be shared by the new entry/exit logic.

No functional change is intended with this patch.

Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
Tested-by: Samir M <samir@linux.ibm.com>
Tested-by: David Gow <davidgow@google.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260427122742.210074-5-mkchauras@gmail.com
This commit is contained in:
Mukesh Kumar Chaurasiya 2026-04-27 17:57:38 +05:30 • committed by Madhavan Srinivasan
commit 02565a782c