Fix 21051:bcc09eb7379f "x86_32: Relocate multiboot modules to below 1GB."

Copy the modules in ascending order in memory, rather than decsending
order. This reduces the likelihood of the second relocation (in
setup.c) corrupting modules through accidental overwriting.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

1 files changed, 22 insertions, 14 deletions

diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
index 233a94f347..47b558b29c 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -68,29 +68,37 @@ multiboot_info_t *reloc(multiboot_info_t *mbi_old)
     {
         module_t *mods = reloc_mbi_struct(
             (module_t *)mbi->mods_addr, mbi->mods_count * sizeof(module_t));
+        u32 max_addr = 0;
+
         mbi->mods_addr = (u32)mods;
+
         for ( i = 0; i < mbi->mods_count; i++ )
         {
-#if XEN_BITSPERLONG == 32
-            /*
-             * 32-bit Xen only maps bottom 1GB of memory at boot time.
-             * Relocate modules which extend beyond this (GRUB2 in particular
-             * likes to place modules as high as possible below 4GB).
-             */
+            if ( mods[i].string )
+                mods[i].string = (u32)reloc_mbi_string((char *)mods[i].string);
+            if ( mods[i].mod_end > max_addr )
+                max_addr = mods[i].mod_end;
+        }
+
+        /*
+         * 32-bit Xen only maps bottom 1GB of memory at boot time. Relocate 
+         * modules which extend beyond this (GRUB2 in particular likes to 
+         * place modules as high as possible below 4GB).
+         */
 #define BOOTMAP_END (1ul<<30) /* 1GB */
-            static void *mod_alloc = (void *)BOOTMAP_END;
-            u32 mod_len = mods[i].mod_end - mods[i].mod_start;
-            if ( mods[i].mod_end > BOOTMAP_END )
+        if ( (XEN_BITSPERLONG == 32) && (max_addr > BOOTMAP_END) )
+        {
+            char *mod_alloc = (char *)BOOTMAP_END;
+            for ( i = 0; i < mbi->mods_count; i++ )
+                mod_alloc -= mods[i].mod_end - mods[i].mod_start;
+            for ( i = 0; i < mbi->mods_count; i++ )
             {
-                mod_alloc = (void *)
-                    (((unsigned long)mod_alloc - mod_len) & ~15ul);
+                u32 mod_len = mods[i].mod_end - mods[i].mod_start;
                 mods[i].mod_start = (u32)memcpy(
                     mod_alloc, (char *)mods[i].mod_start, mod_len);
                 mods[i].mod_end = mods[i].mod_start + mod_len;
+                mod_alloc += mod_len;
             }
-#endif
-            if ( mods[i].string )
-                mods[i].string = (u32)reloc_mbi_string((char *)mods[i].string);
         }
     }