arm64/vdso: Restrict splitting VVAR VMA (bcf99643) · 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. Signed-off-by:

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

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

Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200624083321.144975-6-avagin@gmail.com Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/vdso.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -223,6 +223,17 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
		return vmf_insert_pfn(vma, vmf->address, pfn);
		}

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

		if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
		return -EINVAL;

		return 0;
		}

		static int __setup_additional_pages(enum vdso_abi abi,
		struct mm_struct *mm,
		struct linux_binprm *bprm,
		@@ -302,6 +313,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
		[AA32_MAP_VVAR] = {
		.name = "[vvar]",
		.fault = vvar_fault,
		.mremap = vvar_mremap,
		},
		[AA32_MAP_VDSO] = {
		.name = "[vdso]",
		@@ -468,6 +480,7 @@ static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
		[AA64_MAP_VVAR] = {
		.name = "[vvar]",
		.fault = vvar_fault,
		.mremap = vvar_mremap,
		},
		[AA64_MAP_VDSO] = {
		.name = "[vdso]",

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