x86/vdso: Restrict splitting VVAR VMA (6f74acfd) · Commits · 戴 / test

Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the amount of corner-cases to consider while working further on VDSO time namespace support. As the offset from timens to VVAR page is computed compile-time, the pages in VVAR should stay together and not being partically mremap()'ed. Co-developed-by:

Andrei Vagin <avagin@openvz.org> Signed-off-by:

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

Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-20-dima@arista.com

arch/x86/entry/vdso/vma.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -84,6 +84,18 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
		return 0;
		}

		static int vvar_mremap(const struct vm_special_mapping *sm,
		struct vm_area_struct *new_vma)
		{
		const struct vdso_image *image = new_vma->vm_mm->context.vdso_image;
		unsigned long new_size = new_vma->vm_end - new_vma->vm_start;

		if (new_size != -image->sym_vvar_start)
		return -EINVAL;

		return 0;
		}

		static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
		struct vm_area_struct vma, struct vm_fault vmf)
		{
		@@ -136,6 +148,7 @@ static const struct vm_special_mapping vdso_mapping = {
		static const struct vm_special_mapping vvar_mapping = {
		.name = "[vvar]",
		.fault = vvar_fault,
		.mremap = vvar_mremap,
		};

		/*

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