entry: rseq: Call rseq_handle_notify_resume() in tracehook_notify_resume()

Invoke rseq_handle_notify_resume() from tracehook_notify_resume() now
that the two function are always called back-to-back by architectures
that have rseq.  The rseq helper is stubbed out for architectures that
don't support rseq, i.e. this is a nop across the board.

Note, tracehook_notify_resume() is horribly named and arguably does not
belong in tracehook.h as literally every line of code in it has nothing
to do with tracing.  But, that's been true since commit a42c6ded
("move key_repace_session_keyring() into tracehook_notify_resume()")
first usurped tracehook_notify_resume() back in 2012.  Punt cleaning that
mess up to future patches.

No functional change intended.
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210901203030.1292304-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm/kernel/signal.c

@@ -628,7 +628,6 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 				uprobe_notify_resume(regs);
 			} else {
 				tracehook_notify_resume(regs);
-				rseq_handle_notify_resume(NULL, regs);
 			}
 		}
 		local_irq_disable();

arch/arm64/kernel/signal.c

@@ -940,10 +940,8 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
 			if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 				do_signal(regs);
 
-			if (thread_flags & _TIF_NOTIFY_RESUME) {
+			if (thread_flags & _TIF_NOTIFY_RESUME)
 				tracehook_notify_resume(regs);
-				rseq_handle_notify_resume(NULL, regs);
-			}
 
 			if (thread_flags & _TIF_FOREIGN_FPSTATE)
 				fpsimd_restore_current_state();

arch/csky/kernel/signal.c

@@ -260,8 +260,6 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
 	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 		do_signal(regs);
 
-	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+	if (thread_info_flags & _TIF_NOTIFY_RESUME)
 		tracehook_notify_resume(regs);
-		rseq_handle_notify_resume(NULL, regs);
-	}
 }

arch/mips/kernel/signal.c

@@ -906,10 +906,8 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
 	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 		do_signal(regs);
 
-	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+	if (thread_info_flags & _TIF_NOTIFY_RESUME)
 		tracehook_notify_resume(regs);
-		rseq_handle_notify_resume(NULL, regs);
-	}
 
 	user_enter();
 }

arch/powerpc/kernel/signal.c

@@ -293,10 +293,8 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 		do_signal(current);
 	}
 
-	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+	if (thread_info_flags & _TIF_NOTIFY_RESUME)
 		tracehook_notify_resume(regs);
-		rseq_handle_notify_resume(NULL, regs);
-	}
 }
 
 static unsigned long get_tm_stackpointer(struct task_struct *tsk)

include/linux/tracehook.h

@@ -197,6 +197,8 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
 
 	mem_cgroup_handle_over_high();
 	blkcg_maybe_throttle_current();
+
+	rseq_handle_notify_resume(NULL, regs);
 }
 
 /*

kernel/entry/common.c

@@ -171,10 +171,8 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 			handle_signal_work(regs, ti_work);
 
-		if (ti_work & _TIF_NOTIFY_RESUME) {
+		if (ti_work & _TIF_NOTIFY_RESUME)
 			tracehook_notify_resume(regs);
-			rseq_handle_notify_resume(NULL, regs);
-		}
 
 		/* Architecture specific TIF work */
 		arch_exit_to_user_mode_work(regs, ti_work);

kernel/entry/kvm.c

@@ -19,10 +19,8 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 		if (ti_work & _TIF_NEED_RESCHED)
 			schedule();
 
-		if (ti_work & _TIF_NOTIFY_RESUME) {
+		if (ti_work & _TIF_NOTIFY_RESUME)
 			tracehook_notify_resume(NULL);
-			rseq_handle_notify_resume(NULL, NULL);
-		}
 
 		ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
 		if (ret)