+	; --------- check for signals/restore-sigmask ------------
+	bbit0  r9, TIF_SIGPENDING, chk_next_work
+
+	; save CALLEE Regs.
+	; (i)  If this signal causes coredump - full regfile needed
+	; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
+	;      tracer might call PEEKUSR for a CALLEE reg
+	;
+	; NOTE: SP will grow up by size of CALLEE Reg-File
+	SAVE_CALLEE_SAVED_USER		; clobbers r12
+
+	; save location of saved Callee Regs @ thread_struct->callee
+	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
+	st  sp, [r10, THREAD_CALLEE_REG]
+
+	bl  @do_signal
+
+	; unwind SP for cheap discard of Callee saved Regs
+	DISCARD_CALLEE_SAVED_USER

Uh-oh...  And what if tracer wanted to modify callee-saved regs?

+	b      resume_user_mode_begin	; loop back to start of U mode ret
+
+	; --- notify_resume ---
+chk_next_work:
+	btst   r9, TIF_NOTIFY_RESUME
+	blnz   @do_notify_resume
+
+	;--------- All things done, go back to Userland ------
+
+	b restore_regs

No.  After NOTIFY_RESUME stuff you need to recheck SIGPENDING.  This should
go to resume_user_mode_begin, not restore regs.  Another problem here is
IRQ handling - you hit do_signal()/do_notify_resume() with IRQs disabled,
which is broken - you need to re-enable it before going into either.