[patch V9 05/39] x86/entry: Provide idtentry_enter/exit_user()

[Thomas Gleixner]

As there are exceptions which already handle entry from user mode and from
kernel mode separately having an explicit user handling makes sense and
makes the code easier to understand.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
V9: New patch
---
 arch/x86/entry/common.c         |   31 +++++++++++++++++++++++++++++++
 arch/x86/include/asm/idtentry.h |    3 +++
 2 files changed, 34 insertions(+)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -655,3 +655,34 @@ void noinstr idtentry_exit_cond_rcu(stru
 			rcu_irq_exit();
 	}
 }
+
+/**
+ * idtentry_enter_user - Handle state tracking on idtentry from user mode
+ * @regs:	Pointer to pt_regs of interrupted context
+ *
+ * Invokes enter_from_user_mode() to establish the proper context for
+ * NOHZ_FULL. Otherwise scheduling on exit would not be possible.
+ */
+void noinstr idtentry_enter_user(struct pt_regs *regs)
+{
+	enter_from_user_mode();
+}
+
+/**
+ * idtentry_exit_user - Handle return from exception to user mode
+ * @regs:	Pointer to pt_regs (exception entry regs)
+ *
+ * Runs the necessary preemption and work checks and returns to the caller
+ * with interrupts disabled and no further work pending.
+ *
+ * This is the last action before returning to the low level ASM code which
+ * just needs to return to the appropriate context.
+ *
+ * Counterpart to idtentry_enter_user().
+ */
+void noinstr idtentry_exit_user(struct pt_regs *regs)
+{
+	lockdep_assert_irqs_disabled();
+
+	prepare_exit_to_usermode(regs);
+}
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -7,6 +7,9 @@
 
 #ifndef __ASSEMBLY__
 
+void idtentry_enter_user(struct pt_regs *regs);
+void idtentry_exit_user(struct pt_regs *regs);
+
 bool idtentry_enter_cond_rcu(struct pt_regs *regs, bool cond_rcu);
 void idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit);