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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index e2767c2..b011e4a 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -325,24 +325,55 @@
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 @@
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_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);