linux-kernel - [PATCH v2 4/5] entry: add exit_to_user

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Date:   Tue,  1 Dec 2020 15:27:54 +0100
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Sven Schnelle <svens@...ux.ibm.com>
Subject: [PATCH v2 4/5] entry: add exit_to_user_mode() wrapper

Can be called from architecture dependent code, and simply
calls __exit_to_user_mode(). This way __exit_to_user_mode()
can still be inlined because it is declared static.

Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
---
 include/linux/entry-common.h | 15 +++++++++++++++
 kernel/entry/common.c        | 17 +++++------------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 28a8554fad7d..112007525f50 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -413,4 +413,19 @@ void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
  * 3) Trace interrupts off state
  */
 void enter_from_user_mode(struct pt_regs *regs);
+
+/**
+ * exit_to_user_mode - Fixup state when exiting to user mode
+ *
+ * Syscall/interrupt exit enables interrupts, but the kernel state is
+ * interrupts disabled when this is invoked. Also tell RCU about it.
+ *
+ * 1) Trace interrupts on state
+ * 2) Invoke context tracking if enabled to adjust RCU state
+ * 3) Invoke architecture specific last minute exit code, e.g. speculation
+ *    mitigations, etc.
+ * 4) Tell lockdep that interrupts are enabled
+ */
+
+void exit_to_user_mode(void);
 #endif
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index ee588ee9f122..e696f6912642 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -105,18 +105,6 @@ noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
 	instrumentation_end();
 }
 
-/**
- * __exit_to_user_mode - Fixup state when exiting to user mode
- *
- * Syscall/interupt exit enables interrupts, but the kernel state is
- * interrupts disabled when this is invoked. Also tell RCU about it.
- *
- * 1) Trace interrupts on state
- * 2) Invoke context tracking if enabled to adjust RCU state
- * 3) Invoke architecture specific last minute exit code, e.g. speculation
- *    mitigations, etc.
- * 4) Tell lockdep that interrupts are enabled
- */
 static __always_inline void __exit_to_user_mode(void)
 {
 	instrumentation_begin();
@@ -129,6 +117,11 @@ static __always_inline void __exit_to_user_mode(void)
 	lockdep_hardirqs_on(CALLER_ADDR0);
 }
 
+void noinstr exit_to_user_mode(void)
+{
+	__exit_to_user_mode();
+}
+
 /* Workaround to allow gradual conversion of architecture code */
 void __weak arch_do_signal(struct pt_regs *regs) { }
 
-- 
2.17.1