powerpc/debug: implement HAVE_USER_RETURN_NOTIFIER

@@ -277,6 +277,7 @@ config PPC
 	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
 	select HAVE_STATIC_CALL			if PPC32
 	select HAVE_SYSCALL_TRACEPOINTS
+	select HAVE_USER_RETURN_NOTIFIER
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select HOTPLUG_SMT			if HOTPLUG_CPU

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ARCH_POWERPC_ENTRY_COMMON_H
+#define ARCH_POWERPC_ENTRY_COMMON_H
+
+#include <linux/user-return-notifier.h>
+
+static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
+						  unsigned long ti_work)
+{
+	if (ti_work & _TIF_USER_RETURN_NOTIFY)
+		fire_user_return_notifiers();
+}
+
+#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
+
+#endif

@@ -117,6 +117,7 @@ void arch_setup_new_exec(void);
 #endif
 #define TIF_POLLING_NRFLAG	19	/* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_32BIT		20	/* 32 bit binary */
+#define TIF_USER_RETURN_NOTIFY	21	/* notify kernel of userspace return */
 
 /* as above, but as bit values */
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)

@@ -125,6 +126,7 @@ void arch_setup_new_exec(void);
 #define _TIF_NOTIFY_SIGNAL	(1<<TIF_NOTIFY_SIGNAL)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 #define _TIF_32BIT		(1<<TIF_32BIT)
+#define _TIF_USER_RETURN_NOTIFY	(1<<TIF_USER_RETURN_NOTIFY)
 #define _TIF_RESTORE_TM		(1<<TIF_RESTORE_TM)
 #define _TIF_PATCH_PENDING	(1<<TIF_PATCH_PENDING)
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)

@@ -38,6 +38,7 @@
 #include <linux/uaccess.h>
 #include <linux/pkeys.h>
 #include <linux/seq_buf.h>
+#include <linux/user-return-notifier.h>
 
 #include <asm/interrupt.h>
 #include <asm/io.h>

@@ -1386,6 +1387,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	if (current->thread.regs)
 		restore_math(current->thread.regs);
 #endif /* CONFIG_PPC_BOOK3S_64 */
+	propagate_user_return_notify(prev, new);
 
 	return last;
 }