Windows Server 2003 sulks if we feed it an empty region in base memory

as a result of our memory map editing, so strip out any empty regions.

diff --git a/src/arch/i386/firmware/pcbios/e820mangler.S b/src/arch/i386/firmware/pcbios/e820mangler.S
index 9464a5c..288f499 100644 (file)
--- a/src/arch/i386/firmware/pcbios/e820mangler.S
+++ b/src/arch/i386/firmware/pcbios/e820mangler.S
@@ -296,11 +296,19 @@ patch_e820:
        .size patch_e820, . - patch_e820
 
 /****************************************************************************
- * INT 15,e820 handler
+ * Split E820 memory map entry if necessary
+ *
+ * Parameters:
+ *   As for INT 15,e820
+ * Returns:
+ *   As for INT 15,e820
+ *
+ * Calls the underlying INT 15,e820 and returns a modified memory map.
+ * Regions will be split around any hidden regions.
  ****************************************************************************
  */
        .section ".text16"
-int15_e820:
+split_e820:
        pushw   %si
        pushw   %bp
        /* Caller's %bx => %si, real %ebx to %ebx, call previous handler */
@@ -334,13 +342,43 @@ int15_e820:
        popfw
        popw    %bp
        popw    %si
-       lret    $2
-       .size int15_e820, . - int15_e820
+       ret
+       .size split_e820, . - split_e820
 
        .section ".text16.data"
 real_ebx:
        .long 0
        .size real_ebx, . - real_ebx
+
+/****************************************************************************
+ * INT 15,e820 handler
+ ****************************************************************************
+ */
+       .section ".text16"
+int15_e820:
+       pushl   %eax
+       pushl   %ecx
+       pushl   %edx    
+       call    split_e820
+       pushfw
+       jc      1f
+       /* Check for an empty region */
+       pushl   %eax
+       movl    %es:8(%di), %eax
+       orl     %es:12(%di), %eax
+       popl    %eax
+       jnz     1f
+       /* Strip empty regions out of the returned map */
+       popfw
+       popl    %edx
+       popl    %ecx
+       popl    %eax
+       jmp     int15_e820
+       /* Restore flags from original INT 15,e820 call and return */
+1:     popfw
+       leal    12(%esp), %esp /* avoid changing flags */
+       lret    $2
+       .size int15_e820, . - int15_e820
        
 /****************************************************************************
  * INT 15,e801 handler