x86: Better bzimage_headroom() crash fix.

Signed-off-by:  Joseph Cihula <joseph.cihula@intel.com>

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 1955b65684e2701b63b5e746968f14161b4b5234..6fbe1e4e4ae67d36e72a34fd325b46238450bd18 100644 (file)
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -417,7 +417,7 @@ void __init __start_xen(unsigned long mbi_p)
     unsigned int initrdidx = 1;
     multiboot_info_t *mbi = __va(mbi_p);
     module_t *mod = (module_t *)__va(mbi->mods_addr);
-    unsigned long nr_pages, modules_length, modules_headroom = -1;
+    unsigned long nr_pages, modules_length, modules_headroom;
     unsigned long allocator_bitmap_end;
     int i, e820_warn = 0, bytes = 0;
     struct ns16550_defaults ns16550 = {
@@ -618,6 +618,12 @@ void __init __start_xen(unsigned long mbi_p)
      */
     modules_length = mod[mbi->mods_count-1].mod_end - mod[0].mod_start;
 
+    /* ensure mod[0] is mapped before parsing */
+    bootstrap_map(mod[0].mod_start, mod[0].mod_end);
+    modules_headroom = bzimage_headroom(
+                      (char *)(unsigned long)mod[0].mod_start,
+                      (unsigned long)(mod[0].mod_end - mod[0].mod_start));
+
     for ( i = boot_e820.nr_map-1; i >= 0; i-- )
     {
         uint64_t s, e, mask = (1UL << L2_PAGETABLE_SHIFT) - 1;
@@ -721,11 +727,6 @@ void __init __start_xen(unsigned long mbi_p)
         }
 #endif
 
-        if ( modules_headroom == -1 )
-            modules_headroom = bzimage_headroom(
-                      (char *)(unsigned long)mod[0].mod_start,
-                      (unsigned long)(mod[0].mod_end - mod[0].mod_start));
-
         /* Is the region suitable for relocating the multiboot modules? */
         if ( !initial_images_start && (s < e) &&
              ((e-s) >= (modules_length+modules_headroom)) )