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Commit a05d2eba authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

xen: fix allocation and use of large ldts 



When the ldt gets to more than 1 page in size, the kernel uses vmalloc
to allocate it.  This means that:

 - when making the ldt RO, we must update the pages in both the vmalloc
   mapping and the linear mapping to make sure there are no RW aliases.

 - we need to use arbitrary_virt_to_machine to compute the machine addr
   for each update

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 64f53a04

arch/x86/xen/enlighten.c

+41 −10
Original line number Diff line number Diff line
@@ -325,24 +325,55 @@ static unsigned long xen_store_tr(void) 
	return 0;

}



/*

 * If 'v' is a vmalloc mapping, then find the linear mapping of the

 * page (if any) and also set its protections to match:

 */

static void set_aliased_prot(void *v, pgprot_t prot)

{

	int level;

	pte_t *ptep;

	pte_t pte;

	unsigned long pfn;

	struct page *page;



	ptep = lookup_address((unsigned long)v, &level);

	BUG_ON(ptep == NULL);



	pfn = pte_pfn(*ptep);

	page = pfn_to_page(pfn);



	pte = pfn_pte(pfn, prot);



	if (HYPERVISOR_update_va_mapping((unsigned long)v, pte, 0))

		BUG();



	if (!PageHighMem(page)) {

		void *av = __va(PFN_PHYS(pfn));



		if (av != v)

			if (HYPERVISOR_update_va_mapping((unsigned long)av, pte, 0))

				BUG();

	} else

		kmap_flush_unused();

}



static void xen_alloc_ldt(struct desc_struct *ldt, unsigned entries)

{

	unsigned pages = roundup(entries * LDT_ENTRY_SIZE, PAGE_SIZE);

	void *v = ldt;

	const unsigned entries_per_page = PAGE_SIZE / LDT_ENTRY_SIZE;

	int i;



	for(i = 0; i < pages; i += PAGE_SIZE)

		make_lowmem_page_readonly(v + i);

	for(i = 0; i < entries; i += entries_per_page)

		set_aliased_prot(ldt + i, PAGE_KERNEL_RO);

}



static void xen_free_ldt(struct desc_struct *ldt, unsigned entries)

{

	unsigned pages = roundup(entries * LDT_ENTRY_SIZE, PAGE_SIZE);

	void *v = ldt;

	const unsigned entries_per_page = PAGE_SIZE / LDT_ENTRY_SIZE;

	int i;



	for(i = 0; i < pages; i += PAGE_SIZE)

		make_lowmem_page_readwrite(v + i);

	for(i = 0; i < entries; i += entries_per_page)

		set_aliased_prot(ldt + i, PAGE_KERNEL);

}



static void xen_set_ldt(const void *addr, unsigned entries)
@@ -446,7 +477,7 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum, 
				const void *ptr)

{

	unsigned long lp = (unsigned long)&dt[entrynum];

	xmaddr_t mach_lp = virt_to_machine(lp);

	xmaddr_t mach_lp = arbitrary_virt_to_machine(lp);

	u64 entry = *(u64 *)ptr;



	preempt_disable();