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Wire Alpha into the generic entry code for syscall entry/exit and
return-to-user handling, while keeping the low-level PALcode return paths
Alpha-specific.
Move most of the syscall entry/exit logic out of entSys and into C helpers
built around the generic entry API. Syscall entry now uses
syscall_enter_from_user_mode(), records Alpha-local syscall metadata in
thread_info, handles the ptrace/seccomp skip decision, and selects the
syscall table target in C. The final target call remains in entry.S so
Alpha can preserve its existing syscall ABI and assembly syscall-table
wrappers.
On return from syscalls, finish Alpha's r0/r19 result encoding and
skipped-syscall restart handling in C before calling
syscall_exit_to_user_mode(). Non-syscall returns to user mode use a
separate alpha_exit_to_user_mode() helper, which disables interrupts,
runs irqentry_exit_to_user_mode_prepare(), and then enters the common
exit_to_user_mode() path.
Keep the remaining PALcode restore handling in assembly. In particular,
kernel-mode returns still need Alpha-specific lockdep IRQ-state annotation
based on the saved processor status, while user-mode returns are handed to
the generic exit-to-user code.
Add the generic-entry support bits needed by common code, including
thread_info.syscall_work, syscall trace support, ptrace sysemu request
numbers, and arch_syscall_is_vdso_sigreturn().
This has been tested by booting Alpha with GENERIC_ENTRY enabled, checking
lockdep IRQ-state accounting, running fork/clone-heavy package builds, and
running the seccomp as well as strace test suites.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://lore.kernel.org/r/20260902184058.198679-2-linmag7@gmail.com
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
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