Re: [patch V6 15/31] rseq: Record interrupt from user space

[Mathieu Desnoyers]

On 2025-10-27 04:44, Thomas Gleixner wrote:
[...]
> @@ -281,6 +281,7 @@ static __always_inline void exit_to_user
>   static __always_inline void irqentry_enter_from_user_mode(struct pt_regs *regs)
>   {
>   	enter_from_user_mode(regs);
> +	rseq_note_user_irq_entry();
>   }
>   
Looking at x86, both exc_debug_user() and exc_int3() invoke
irqentry_enter_from_user_mode(), but there are various
other traps that can come from userspace (e.g. math_error,
exc_general_protection, ...). Some of those traps don't
necessarily end with a signal delivery to the offending
process. And some of those traps enable interrupts.

So what happens if such a trap is triggered from userspace,
and then scheduling happens on top of this trap ? Is this
skipping rseq ip fixup and rseq fields updates ?

Thanks,

Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com