On 2025-08-23 12:40, Thomas Gleixner wrote:
> Make the syscall exit debug mechanism available via the static branch on
> architectures which utilize the generic entry code.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> ---
> include/linux/entry-common.h | 2 +-
> include/linux/rseq_entry.h | 9 +++++++++
> kernel/rseq.c | 19 +++++++++++++------
> 3 files changed, 23 insertions(+), 7 deletions(-)
>
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -146,7 +146,7 @@ static __always_inline void syscall_exit
> local_irq_enable();
> }
>
> - rseq_syscall(regs);
> + rseq_debug_syscall_return(regs);
>
> /*
> * Do one-time syscall specific work. If these work items are
> --- a/include/linux/rseq_entry.h
> +++ b/include/linux/rseq_entry.h
> @@ -286,9 +286,18 @@ static __always_inline void rseq_exit_to
> ev->events = 0;
> }
>
> +void __rseq_debug_syscall_return(struct pt_regs *regs);
> +
> +static inline void rseq_debug_syscall_return(struct pt_regs *regs)
> +{
> + if (static_branch_unlikely(&rseq_debug_enabled))
> + __rseq_debug_syscall_return(regs);
> +}
> +
> #else /* CONFIG_RSEQ */
> static inline void rseq_note_user_irq_entry(void) { }
> static inline void rseq_exit_to_user_mode(void) { }
> +static inline void rseq_debug_syscall_return(struct pt_regs *regs) { }
> #endif /* !CONFIG_RSEQ */
>
> #endif /* _LINUX_RSEQ_ENTRY_H */
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -470,12 +470,7 @@ void __rseq_handle_notify_resume(struct
> force_sigsegv(sig);
> }
>
> -#ifdef CONFIG_DEBUG_RSEQ
> -/*
> - * Terminate the process if a syscall is issued within a restartable
> - * sequence.
> - */
> -void rseq_syscall(struct pt_regs *regs)
> +void __rseq_debug_syscall_return(struct pt_regs *regs)
> {
> struct task_struct *t = current;
> u64 csaddr;
> @@ -493,6 +488,18 @@ void rseq_syscall(struct pt_regs *regs)
> fail:
> force_sig(SIGSEGV);
> }
> +
> +#ifdef CONFIG_DEBUG_RSEQ
> +/*
> + * Kept around to keep GENERIC_ENTRY=n architectures supported.
> + *
> + * Terminate the process if a syscall is issued within a restartable
> + * sequence.
> + */
> +void rseq_syscall(struct pt_regs *regs)
> +{
> + __rseq_debug_syscall_return(regs);
> +}
> #endif
>
> /*
>
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com