[PATCH 02/10] entry: Remove local_irq_{enable,disable}_exit_to_user()

[Mark Rutland]

The local_irq_enable_exit_to_user() and local_irq_disable_exit_to_user()
functions are never overridden by architecture code, and are always
equivalent to local_irq_enable() and local_irq_disable().

These functions were added on the assumption that arm64 would override
them to manage 'DAIF' exception masking, as described by Thomas Gleixner
in these threads:

  https://lore.kernel.org/all/20190919150809.340471236@linutronix.de/
  https://lore.kernel.org/all/alpine.DEB.2.21.1910240119090.1852@nanos.tec.linutronix.de/

In practice arm64 did not need to override either. Prior to moving to
the generic irqentry code, arm64's management of DAIF was reworked in
commit:

  97d935faacde ("arm64: Unmask Debug + SError in do_notify_resume()")

Since that commit, arm64 only masks interrupts during the 'prepare' step
when returning to user mode, and masks other DAIF exceptions later.
Within arm64_exit_to_user_mode(), the arm64 entry code is as follows:

	local_irq_disable();
	exit_to_user_mode_prepare_legacy(regs);
	local_daif_mask();
	mte_check_tfsr_exit();
	exit_to_user_mode();

Remove the unnecessary local_irq_enable_exit_to_user() and
local_irq_disable_exit_to_user() functions.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Andy Lutomirski <luto at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Jinjie Ruan <ruanjinjie at huawei.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at kernel.org>
Cc: Vladimir Murzin <vladimir.murzin at arm.com>
Cc: Will Deacon <will at kernel.org>
---
 include/linux/entry-common.h     |  2 +-
 include/linux/irq-entry-common.h | 31 -------------------------------
 kernel/entry/common.c            |  4 ++--
 3 files changed, 3 insertions(+), 34 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index f83ca0abf2cdb..dbaa153100f44 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -321,7 +321,7 @@ static __always_inline void syscall_exit_to_user_mode(struct pt_regs *regs)
 {
 	instrumentation_begin();
 	syscall_exit_to_user_mode_work(regs);
-	local_irq_disable_exit_to_user();
+	local_irq_disable();
 	syscall_exit_to_user_mode_prepare(regs);
 	instrumentation_end();
 	exit_to_user_mode();
diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
index 3cf4d21168ba1..93b4b551f7ae4 100644
--- a/include/linux/irq-entry-common.h
+++ b/include/linux/irq-entry-common.h
@@ -100,37 +100,6 @@ static __always_inline void enter_from_user_mode(struct pt_regs *regs)
 	instrumentation_end();
 }
 
-/**
- * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
- * @ti_work:	Cached TIF flags gathered with interrupts disabled
- *
- * Defaults to local_irq_enable(). Can be supplied by architecture specific
- * code.
- */
-static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
-
-#ifndef local_irq_enable_exit_to_user
-static __always_inline void local_irq_enable_exit_to_user(unsigned long ti_work)
-{
-	local_irq_enable();
-}
-#endif
-
-/**
- * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
- *
- * Defaults to local_irq_disable(). Can be supplied by architecture specific
- * code.
- */
-static inline void local_irq_disable_exit_to_user(void);
-
-#ifndef local_irq_disable_exit_to_user
-static __always_inline void local_irq_disable_exit_to_user(void)
-{
-	local_irq_disable();
-}
-#endif
-
 /**
  * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
  *				 to user mode.
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 9ef63e4147913..b5e05d87ba391 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -47,7 +47,7 @@ static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *re
 	 */
 	while (ti_work & EXIT_TO_USER_MODE_WORK_LOOP) {
 
-		local_irq_enable_exit_to_user(ti_work);
+		local_irq_enable();
 
 		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
 			if (!rseq_grant_slice_extension(ti_work & TIF_SLICE_EXT_DENY))
@@ -74,7 +74,7 @@ static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *re
 		 * might have changed while interrupts and preemption was
 		 * enabled above.
 		 */
-		local_irq_disable_exit_to_user();
+		local_irq_disable();
 
 		/* Check if any of the above work has queued a deferred wakeup */
 		tick_nohz_user_enter_prepare();
-- 
2.30.2