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xen: fix allocation and use of large ldts

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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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge 2008-07-27 08:45:02 -07:00 committed by Ingo Molnar
parent 64f53a0492
commit a05d2ebab2
1 changed files with 41 additions and 10 deletions
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51
arch/x86/xen/enlighten.c
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@ -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();
@ -579,7 +610,7 @@ static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
}
static void xen_load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
struct thread_struct *thread)
{
struct multicall_space mcs = xen_mc_entry(0);
MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);