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); + + for (vma = mm->mmap; vma; vma = vma->vm_next) { + unsigned long size = vma->vm_end - vma->vm_start; + + if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) + zap_page_range(vma, vma->vm_start, size); +#ifdef CONFIG_COMPAT_VDSO + if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) + zap_page_range(vma, vma->vm_start, size); +#endif + } + + mmap_read_unlock(mm); + return 0; +} +#endif + static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, struct vm_area_struct *vma, struct vm_fault *vmf) { -- 2.24.1
