[tip: x86/entry] x86/entry: Provide idtentry_enter/exit_user()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     d4b1f51731fd10a836e46f54c96a8913d945735b
Gitweb:        https://git.kernel.org/tip/d4b1f51731fd10a836e46f54c96a8913d945735b
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Thu, 21 May 2020 22:05:18 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 26 May 2020 19:06:27 +02:00

x86/entry: Provide idtentry_enter/exit_user()

As there are exceptions which already handle entry from user mode and from
kernel mode separately, providing explicit user entry/exit handling callbacks
makes sense and makes the code easier to understand.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200521202117.289548561@xxxxxxxxxxxxx
---
 arch/x86/entry/common.c         | 31 +++++++++++++++++++++++++++++++
 arch/x86/include/asm/idtentry.h |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index a7f5846..b7fcb13 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -658,3 +658,34 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
 			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);
+}
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index a116b80..b3aca72 100644
--- 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);