[Xen-changelog] Fix the writable pagetable error paths. Some of them are genuine Xen

[BitKeeper B. <ri...@su...>]

ChangeSet 1.1404, 2004/10/20 17:23:51+01:00, ka...@fr...

	Fix the writable pagetable error paths. Some of them are genuine Xen
	bugs if they trigger. Otehrs now properly clean wrpt state before
	crashing the domain, so we don't leave any refcnts inconsistent.



 memory.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)


diff -Nru a/xen/arch/x86/memory.c b/xen/arch/x86/memory.c
--- a/xen/arch/x86/memory.c	2004-10-20 13:00:38 -04:00
+++ b/xen/arch/x86/memory.c	2004-10-20 13:00:38 -04:00
@@ -1604,7 +1604,11 @@
     if ( unlikely(__get_user(pte, ptep)) )
     {
         MEM_LOG("ptwr: Could not read pte at %p\n", ptep);
-        domain_crash();
+        /*
+         * Really a bug. We could read this PTE during the initial fault,
+         * and pagetables can't have changed meantime. XXX Multi-proc guests?
+         */
+        BUG();
     }
     PTWR_PRINTK("[%c] disconnected_l1va at %p is %08lx\n",
                 PTWR_PRINT_WHICH, ptep, pte);
@@ -1627,7 +1631,11 @@
     if ( unlikely(__put_user(pte, ptep)) )
     {
         MEM_LOG("ptwr: Could not update pte at %p\n", ptep);
-        domain_crash();
+        /*
+         * Really a bug. We could write this PTE during the initial fault,
+         * and pagetables can't have changed meantime. XXX Multi-proc guests?
+         */
+        BUG();
     }
 
     /* Ensure that there are no stale writable mappings in any TLB. */
@@ -1668,6 +1676,12 @@
         if ( unlikely(!get_page_from_l1e(nl1e, d)) )
         {
             MEM_LOG("ptwr: Could not re-validate l1 page\n");
+            /*
+             * Make the remaining p.t's consistent before crashing, so the
+             * reference counts are correct.
+             */
+            memcpy(&pl1e[i], &ptwr_info[cpu].ptinfo[which].page[i],
+                   (ENTRIES_PER_L1_PAGETABLE - i) * sizeof(l1_pgentry_t));
             domain_crash();
         }
         
@@ -1781,6 +1795,9 @@
     {
         MEM_LOG("ptwr: Could not update pte at %p\n", (unsigned long *)
                 &linear_pg_table[addr>>PAGE_SHIFT]);
+        /* Toss the writable pagetable state and crash. */
+        unmap_domain_mem(ptwr_info[cpu].ptinfo[which].pl1e);
+        ptwr_info[cpu].ptinfo[which].l1va = 0;
         domain_crash();
     }