On Wed, Oct 23, 2019 at 5:31 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Interrupt state tracing can be safely done in C code. The few stack
> operations in assembly do not need to be covered.
>
> Remove the now pointless indirection via .Lsyscall_32_done and jump to
> swapgs_restore_regs_and_return_to_usermode directly.

This doesn't look right.

>  #define SYSCALL_EXIT_WORK_FLAGS                                \
> @@ -279,6 +282,9 @@ static void syscall_slow_exit_work(struc
>  {
>         struct thread_info *ti;
>
> +       /* User to kernel transition disabled interrupts. */
> +       trace_hardirqs_off();
> +

So you just traced IRQs off, but...

>         enter_from_user_mode();
>         local_irq_enable();

Now they're on and traced on again?

I also don't see how your patch handles the fastpath case.

How about the attached patch instead?