[Xen-changelog] Fix x86/64 pagetable initialisation so that only things that

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID c42a9e2f6c5b270cbcbfc9b918de9b66750448b3
# Parent  bca2fd76995ea8c811cc52a7edaabaeae03a677a
Fix x86/64 pagetable initialisation so that only things that
need to be are mapped read-only.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r bca2fd76995e -r c42a9e2f6c5b 
linux-2.6-xen-sparse/arch/xen/x86_64/mm/init.c
--- a/linux-2.6-xen-sparse/arch/xen/x86_64/mm/init.c    Wed Aug 24 15:21:48 2005
+++ b/linux-2.6-xen-sparse/arch/xen/x86_64/mm/init.c    Wed Aug 24 15:22:44 2005
@@ -441,6 +441,31 @@
        *dst = val;
 }
 
+static inline int make_readonly(unsigned long paddr)
+{
+    int readonly = 0;
+
+    /* Make new page tables read-only. */
+    if ((paddr < ((table_start << PAGE_SHIFT) + tables_space)) &&
+        (paddr >= (table_start << PAGE_SHIFT)))
+        readonly = 1;
+
+    /* Make old page tables read-only. */
+    if ((paddr < ((xen_start_info.pt_base - __START_KERNEL_map) +
+                  (xen_start_info.nr_pt_frames << PAGE_SHIFT))) &&
+        (paddr >= (xen_start_info.pt_base - __START_KERNEL_map)))
+        readonly = 1;
+
+    /*
+     * No need for writable mapping of kernel image. This also ensures that
+     * page and descriptor tables embedded inside don't have writable mappings.
+     */
+    if ((paddr >= __pa_symbol(&_text)) && (paddr < __pa_symbol(&_end)))
+        readonly = 1;
+
+    return readonly;
+}
+
 void __init phys_pud_init(pud_t *pud, unsigned long address, unsigned long end)
 { 
         long i, j, k; 
@@ -477,9 +502,7 @@
                         pte = alloc_low_page(&pte_phys);
                         pte_save = pte;
                         for (k = 0; k < PTRS_PER_PTE; pte++, k++, paddr += 
PTE_SIZE) {
-                                if (paddr < (table_start << PAGE_SHIFT) 
-                                    + tables_space)
-                                {
+                                if (make_readonly(paddr)) {
                                         __set_pte(pte, 
                                                 __pte(paddr | (_KERNPG_TABLE & 
~_PAGE_RW)));
                                         continue;
diff -r bca2fd76995e -r c42a9e2f6c5b xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Wed Aug 24 15:21:48 2005
+++ b/xen/arch/x86/mm.c Wed Aug 24 15:22:44 2005
@@ -1449,8 +1449,10 @@
                     if ( ((x & PGT_type_mask) != PGT_l2_page_table) ||
                          ((type & PGT_type_mask) != PGT_l1_page_table) )
                         MEM_LOG("Bad type (saw %" PRtype_info
-                                "!= exp %" PRtype_info ") for pfn %lx",
-                                x, type, page_to_pfn(page));
+                                "!= exp %" PRtype_info ") "
+                                "for mfn %lx (pfn %x)",
+                                x, type, page_to_pfn(page),
+                                machine_to_phys_mapping[page_to_pfn(page)]);
                     return 0;
                 }
                 else if ( (x & PGT_va_mask) == PGT_va_mutable )

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