Commit 5056c2c5 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
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s390/vdso: put vdso datapage in a separate vma 



Add a separate "[vvar]" mapping for the vdso datapage, since it
doesn't need to be executable or COW-able.

This is actually the s390 implementation of commit 87154938
("arm64: vdso: put vdso datapage in a separate vma")

Reviewed-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent dfc11c98

arch/s390/kernel/vdso.c

+35 −20
Original line number Diff line number Diff line
@@ -40,6 +40,14 @@ static int __init vdso_setup(char *str) 
}

__setup("vdso=", vdso_setup);



static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,

			     struct vm_area_struct *vma, struct vm_fault *vmf)

{

	if (vmf->pgoff == 0)

		return vmf_insert_pfn(vma, vmf->address, virt_to_pfn(vdso_data));

	return VM_FAULT_SIGBUS;

}



static int vdso_mremap(const struct vm_special_mapping *sm,

		       struct vm_area_struct *vma)

{
@@ -47,6 +55,11 @@ static int vdso_mremap(const struct vm_special_mapping *sm, 
	return 0;

}



static struct vm_special_mapping vvar_mapping = {

	.name = "[vvar]",

	.fault = vvar_fault,

};



static struct vm_special_mapping vdso_mapping = {

	.name = "[vdso]",

	.mremap = vdso_mremap,
@@ -61,38 +74,41 @@ early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 


int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

{

	unsigned long addr, vdso_text_start, vdso_text_len, vdso_mapping_len;

	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma;

	unsigned long vdso_base;

	int rc;



	if (!vdso_enabled || is_compat_task())

		return 0;

	if (mmap_write_lock_killable(mm))

		return -EINTR;

	vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);

	rc = vdso_base;

	if (IS_ERR_VALUE(vdso_base))

	vdso_text_len = vdso_pages << PAGE_SHIFT;

	vdso_mapping_len = vdso_text_len + PAGE_SIZE;

	addr = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);

	rc = addr;

	if (IS_ERR_VALUE(addr))

		goto out;

	/*

	 * our vma flags don't have VM_WRITE so by default, the process

	 * isn't allowed to write those pages.

	 * gdb can break that with ptrace interface, and thus trigger COW

	 * on those pages but it's then your responsibility to never do that

	 * on the "data" page of the vDSO or you'll stop getting kernel

	 * updates and your nice userland gettimeofday will be totally dead.

	 * It's fine to use that for setting breakpoints in the vDSO code

	 * pages though.

	 */

	vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,

	/* VM_MAYWRITE for COW so gdb can set breakpoints */

	vdso_text_start = addr;

	vma = _install_special_mapping(mm, addr, vdso_text_len,

				       VM_READ|VM_EXEC|

				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,

				       &vdso_mapping);

	rc = PTR_ERR(vma);

	if (IS_ERR(vma))

		goto out;

	current->mm->context.vdso_base = vdso_base;

	addr += vdso_text_len;

	vma = _install_special_mapping(mm, addr, PAGE_SIZE,

				       VM_READ|VM_MAYREAD|VM_PFNMAP,

				       &vvar_mapping);

	if (IS_ERR(vma)) {

		do_munmap(mm, vdso_text_start, vdso_text_len, NULL);

		rc = PTR_ERR(vma);

	} else {

		current->mm->context.vdso_base = vdso_text_start;

		rc = 0;

	}

out:

	mmap_write_unlock(mm);

	return rc;
@@ -103,15 +119,14 @@ static int __init vdso_init(void) 
	struct page **pages;

	int i;



	vdso_pages = ((vdso64_end - vdso64_start) >> PAGE_SHIFT) + 1;

	vdso_pages = (vdso64_end - vdso64_start) >> PAGE_SHIFT;

	pages = kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);

	if (!pages) {

		vdso_enabled = 0;

		return -ENOMEM;

	}

	for (i = 0; i < vdso_pages - 1; i++)

	for (i = 0; i < vdso_pages; i++)

		pages[i] = virt_to_page(vdso64_start + i * PAGE_SIZE);

	pages[vdso_pages - 1] = virt_to_page(vdso_data);

	pages[vdso_pages] = NULL;

	vdso_mapping.pages = pages;

	return 0;