arm64/vdso: Zap vvar pages when switching to a time namespace (1b6867d2) · Commits · 戴 / test

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. Signed-off-by:

Andrei Vagin <avagin@gmail.com> Reviewed-by:

Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by:

Dmitry Safonov <dima@arista.com> Reviewed-by:

Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20200624083321.144975-3-avagin@gmail.com Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/vdso.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -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)
		{

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