Commit 22f66e7e authored by Mark Rutland's avatar Mark Rutland Committed by Thomas Gleixner
Browse files

entry: Remove local_irq_{enable,disable}_exit_to_user() 

local_irq_enable_exit_to_user() and local_irq_disable_exit_to_user() 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:

  97d935fa ("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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Reviewed-by: default avatarJinjie Ruan <ruanjinjie@huawei.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260407131650.3813777-3-mark.rutland@arm.com
parent 1f0d117c

include/linux/entry-common.h

+1 −1
Original line number Diff line number Diff line
@@ -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();

include/linux/irq-entry-common.h

+0 −31
Original line number Diff line number Diff line
@@ -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.

kernel/entry/common.c

+2 −2
Original line number Diff line number Diff line
@@ -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();