On Wed, Jun 24, 2020 at 01:33:17AM -0700, Andrei Vagin wrote: > The order of vvar pages depends on whether a task belongs to the root > time namespace or not. In the root time namespace, a task doesn't have a > per-namespace page. In a non-root namespace, the VVAR page which contains > the system-wide VDSO data is replaced with a namespace specific page > that contains clock offsets. > > Whenever a task changes its namespace, the VVAR page tables are cleared > and then they will be re-faulted with a corresponding layout. > > A task can switch its time namespace only if its ->mm isn't shared with > another task. > > Reviewed-by: Vincenzo Frascino <[email protected]> > Reviewed-by: Dmitry Safonov <[email protected]> > Signed-off-by: Andrei Vagin <[email protected]> > --- > arch/arm64/kernel/vdso.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > index 7c4620451fa5..bdf492a17dff 100644 > --- a/arch/arm64/kernel/vdso.c > +++ b/arch/arm64/kernel/vdso.c > @@ -124,6 +124,37 @@ static int __vdso_init(enum vdso_abi abi) > return 0; > } > > +#ifdef CONFIG_TIME_NS > +/* > + * The vvar mapping contains data for a specific time namespace, so when a > task > + * changes namespace we must unmap its vvar data for the old namespace. > + * Subsequent faults will map in data for the new namespace. > + * > + * For more details see timens_setup_vdso_data(). > + */ > +int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) > +{ > + struct mm_struct *mm = task->mm; > + struct vm_area_struct *vma; > + > + mmap_read_lock(mm);
Perfect, thanks! I'll adapt my patches so that my change and this change don't conflict and can go in together. Once they're landed we can simply turn int vdso_join_timens() into void vdso_join_timens() everywhere. Reviewed-by: Christian Brauner <[email protected]> Thanks! Christian
