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Commit 87154938 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
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arm64: vdso: put vdso datapage in a separate vma 



The VDSO datapage doesn't need to be executable (no code there) or
CoW-able (the kernel writes the page, so a private copy is totally
useless).

This patch moves the datapage into its own VMA, identified as "[vvar]"
in /proc/<pid>/maps.

Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent b2f8c07b

arch/arm64/kernel/vdso.c

+26 −8
Original line number Diff line number Diff line
@@ -138,11 +138,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, 
				int uses_interp)

{

	struct mm_struct *mm = current->mm;

	unsigned long vdso_base, vdso_mapping_len;

	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;

	int ret;



	vdso_text_len = vdso_pages << PAGE_SHIFT;

	/* Be sure to map the data page */

	vdso_mapping_len = (vdso_pages + 1) << PAGE_SHIFT;

	vdso_mapping_len = vdso_text_len + PAGE_SIZE;



	down_write(&mm->mmap_sem);

	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
@@ -152,35 +153,52 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, 
	}

	mm->context.vdso = (void *)vdso_base;



	ret = install_special_mapping(mm, vdso_base, vdso_mapping_len,

	ret = install_special_mapping(mm, vdso_base, vdso_text_len,

				      VM_READ|VM_EXEC|

				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,

				      vdso_pagelist);

	if (ret) {

		mm->context.vdso = NULL;

	if (ret)

		goto up_fail;



	vdso_base += vdso_text_len;

	ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,

				      VM_READ|VM_MAYREAD,

				      vdso_pagelist + vdso_pages);

	if (ret)

		goto up_fail;

	}



up_fail:

	up_write(&mm->mmap_sem);

	return 0;



up_fail:

	mm->context.vdso = NULL;

	up_write(&mm->mmap_sem);

	return ret;

}



const char *arch_vma_name(struct vm_area_struct *vma)

{

	unsigned long vdso_text;



	if (!vma->vm_mm)

		return NULL;



	vdso_text = (unsigned long)vma->vm_mm->context.vdso;



	/*

	 * We can re-use the vdso pointer in mm_context_t for identifying

	 * the vectors page for compat applications. The vDSO will always

	 * sit above TASK_UNMAPPED_BASE and so we don't need to worry about

	 * it conflicting with the vectors base.

	 */

	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) {

	if (vma->vm_start == vdso_text) {

#ifdef CONFIG_COMPAT

		if (vma->vm_start == AARCH32_VECTORS_BASE)

			return "[vectors]";

#endif

		return "[vdso]";

	} else if (vma->vm_start == (vdso_text + (vdso_pages << PAGE_SHIFT))) {

		return "[vvar]";

	}



	return NULL;