Re: Cannot access memory beyond end of bootstrap direct-map area

[Keir Fraser <keir.fraser@eu.citrix.com>]

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On 24/03/2010 07:16, "Florian Wagner" <f_wagner@syscomp.de> wrote:

>> Okay, please try the attached patch. You only need to rebuild/install
>> the hypervisor itself (xen.gz). If it works okay for you I will apply
>> it to the next stable releases of 4.0 and 3.4.
> 
> The patch didn't apply cleanly to the xen 3.4.2 release so I modified
> it to do so (see attached reloc-3.4.2).
> 
> All it did is turn the original problem into another one. I now get a
> "elf_init: not an ELF binary" error instead.

Please try the attached patch, which applies on top of the previous patch.

  -- Keir


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diff -r 0475c567c708 xen/arch/x86/boot/reloc.c
--- a/xen/arch/x86/boot/reloc.c	Tue Mar 23 09:37:59 2010 +0000
+++ b/xen/arch/x86/boot/reloc.c	Wed Mar 24 08:32:36 2010 +0000
@@ -68,29 +68,37 @@
     {
         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);
         }
     }
 

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