Re: [RFC PATCH 12/25] kvx: Add system call support

Thomas Gleixner
2023-01-09T21:00:18Z

On Tue, Jan 03 2023 at 17:43, Yann Sionneau wrote:
> +/***********************************************************************
> +* Common exception return path
> +***********************************************************************/
> +/**
> + * Restore registers after exception
> + * When entering this macro, $sp must be located right before regs
> + * storage.
> + */
> +EXCEPTION_ENTRY(return_from_exception)
> +#ifdef CONFIG_DEBUG_EXCEPTION_STACK
> + ld $r1 = 0[$sp]
> + ;;
> + sbfd $r1 = $r1, $sp
> + ;;
> + cb.deqz $r1, _check_ok
> + ;;
> + make $r2 = panic
> + make $r0 = stack_error_panic_str_label
> + ;;
> + icall $r2
> + ;;
> +_check_ok:
> + addd $sp = $sp, STACK_REG_SIZE
> + ;;
> +#endif
> + get $r11 = $sr
> + /* Load sps value from saved registers */
> + ld $r6 = PT_SPS[$sp]
> + ;;
> + /* Disable interrupt to check task flags atomically */
> + disable_interrupt $r60
> + ;;
> + /* Check PL bit of sps, if set, then it means we are returning
> + * to a lower privilege level (ie to user), if so, we need to
> + * check work pending. If coming from kernel, directly go to
> + * register restoration */
> + cb.even $r6? _restore_regs
> + ld $r1 = TASK_TI_FLAGS[$r11]
> + ;;
> + /* Do we have work pending ? */
> + andd $r5 = $r1, _TIF_WORK_MASK

Please use the generic entry code to handle pending work, tracing etc.

All over the place....

Thanks,

tglx