[CRIU] [PATCHv4 17/28] x86/vdso: Switch image on setns()/unshare()/clone()

[Thomas Gleixner]

On Wed, 12 Jun 2019, Dmitry Safonov wrote:
>  
> +#ifdef CONFIG_TIME_NS
> +int vdso_join_timens(struct task_struct *task)
> +{
> +	struct mm_struct *mm = task->mm;
> +	struct vm_area_struct *vma;
> +
> +	if (down_write_killable(&mm->mmap_sem))
> +		return -EINTR;
> +
> +	for (vma = mm->mmap; vma; vma = vma->vm_next) {
> +		unsigned long size = vma->vm_end - vma->vm_start;
> +
> +		if (vma_is_special_mapping(vma, &vvar_mapping) ||
> +		    vma_is_special_mapping(vma, &vdso_mapping))
> +			zap_page_range(vma, vma->vm_start, size);
> +	}
> +
> +	up_write(&mm->mmap_sem);
> +	return 0;
> +}
> +#else /* CONFIG_TIME_NS */
> +int vdso_join_timens(struct task_struct *task)
> +{
> +	return -ENXIO;
> +}

Is that else path really required? The callsite is only compiled when
CONFIG_TIME_NS is enabled, right?

Thanks,

	tglx