On 2025-08-23 12:40, Thomas Gleixner wrote:
> exit_to_user_mode_prepare() is used for both interrupts and syscalls, but
> there is extra rseq work, which is only required for in the interrupt exit
> case.
>
> Split up the function and provide wrappers for syscalls and interrupts,
> which allows to seperate the rseq exit work in the next step.
separate
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> include/linux/entry-common.h | 2 -
> include/linux/irq-entry-common.h | 42 ++++++++++++++++++++++++++++++++++-----
> 2 files changed, 38 insertions(+), 6 deletions(-)
>
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -156,7 +156,7 @@ static __always_inline void syscall_exit
> if (unlikely(work & SYSCALL_WORK_EXIT))
> syscall_exit_work(regs, work);
> local_irq_disable_exit_to_user();
> - exit_to_user_mode_prepare(regs);
> + syscall_exit_to_user_mode_prepare(regs);
> }
>
> /**
> --- a/include/linux/irq-entry-common.h
> +++ b/include/linux/irq-entry-common.h
> @@ -201,7 +201,7 @@ void arch_do_signal_or_restart(struct pt
> unsigned long exit_to_user_mode_loop(struct pt_regs *regs, unsigned long ti_work);
>
> /**
> - * exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
> + * __exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
> * @regs: Pointer to pt_regs on entry stack
> *
> * 1) check that interrupts are disabled
> @@ -209,8 +209,10 @@ unsigned long exit_to_user_mode_loop(str
> * 3) call exit_to_user_mode_loop() if any flags from
> * EXIT_TO_USER_MODE_WORK are set
> * 4) check that interrupts are still disabled
> + *
> + * Don't invoke directly, use the syscall/irqentry_ prefixed variants below
> */
> -static __always_inline void exit_to_user_mode_prepare(struct pt_regs *regs)
> +static __always_inline void __exit_to_user_mode_prepare(struct pt_regs *regs)
> {
> unsigned long ti_work;
>
> @@ -224,15 +226,45 @@ static __always_inline void exit_to_user
> ti_work = exit_to_user_mode_loop(regs, ti_work);
>
> arch_exit_to_user_mode_prepare(regs, ti_work);
> +}
>
> - rseq_exit_to_user_mode();
> -
> +static __always_inline void __exit_to_user_mode_validate(void)
> +{
> /* Ensure that kernel state is sane for a return to userspace */
> kmap_assert_nomap();
> lockdep_assert_irqs_disabled();
> lockdep_sys_exit();
> }
>
> +
> +/**
> + * syscall_exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
> + * @regs: Pointer to pt_regs on entry stack
> + *
> + * Wrapper around __exit_to_user_mode_prepare() to seperate the exit work for
separate
> + * syscalls and interrupts.
> + */
> +static __always_inline void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
> +{
> + __exit_to_user_mode_prepare(regs);
> + rseq_exit_to_user_mode();
> + __exit_to_user_mode_validate();
> +}
> +
> +/**
> + * irqentry_exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
> + * @regs: Pointer to pt_regs on entry stack
> + *
> + * Wrapper around __exit_to_user_mode_prepare() to seperate the exit work for
separate
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> + * syscalls and interrupts.
> + */
> +static __always_inline void irqentry_exit_to_user_mode_prepare(struct pt_regs *regs)
> +{
> + __exit_to_user_mode_prepare(regs);
> + rseq_exit_to_user_mode();
> + __exit_to_user_mode_validate();
> +}
> +
> /**
> * exit_to_user_mode - Fixup state when exiting to user mode
> *
> @@ -297,7 +329,7 @@ static __always_inline void irqentry_ent
> static __always_inline void irqentry_exit_to_user_mode(struct pt_regs *regs)
> {
> instrumentation_begin();
> - exit_to_user_mode_prepare(regs);
> + irqentry_exit_to_user_mode_prepare(regs);
> instrumentation_end();
> exit_to_user_mode();
> }
>
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com