basememsize() updates the BIOS FBMS counter at 40:13.

diff --git a/src/arch/i386/firmware/pcbios/memsizes.c b/src/arch/i386/firmware/pcbios/memsizes.c
index 3284e1efdd9c7fdd88c27deec4df22d9011f1d54..25e9fb192147c6f6c23f5a7052deef80902bf67c 100644 (file)
--- a/src/arch/i386/firmware/pcbios/memsizes.c
+++ b/src/arch/i386/firmware/pcbios/memsizes.c
@@ -2,14 +2,11 @@
 #include "stddef.h"
 #include "realmode.h"
 #include "init.h"
+#include "etherboot.h"
 #include "memsizes.h"
 
 #define CF ( 1 << 0 )
 
-#ifndef MEMSIZES_DEBUG 
-#define MEMSIZES_DEBUG 0
-#endif
-
 /* by Eric Biederman */
 
 struct meminfo meminfo;
@@ -19,10 +16,18 @@ BASEMEMSIZE - Get size of the conventional (base) memory
 **************************************************************************/
 static unsigned short basememsize ( void ) {
        uint16_t int12_basememsize, fbms_basememsize;
+       uint16_t basememsize;
 
        /* There are two methods for retrieving the base memory size:
         * INT 12 and the BIOS FBMS counter at 40:13.  We read both
         * and use the smaller value, to be paranoid.
+        * 
+        * We then store the smaller value in the BIOS FBMS counter so
+        * that other code (e.g. basemem.c) can rely on it and not
+        * have to use INT 12.  This is especially important because
+        * basemem.c functions can be called in a context in which
+        * there is no real-mode stack (e.g. when trying to allocate
+        * memory for a real-mode stack...)
         */
 
        REAL_EXEC ( rm_basememsize,
@@ -34,8 +39,12 @@ static unsigned short basememsize ( void ) {
 
        get_real ( fbms_basememsize, 0x40, 0x13 );
 
-       return ( int12_basememsize < fbms_basememsize ?
-                int12_basememsize : fbms_basememsize );
+       basememsize = ( int12_basememsize < fbms_basememsize ?
+                       int12_basememsize : fbms_basememsize );
+
+       put_real ( basememsize, 0x40, 0x13 );
+
+       return basememsize;
 }
 
 /**************************************************************************
@@ -204,7 +213,7 @@ void get_memsizes ( void ) {
                }
        }
 
-#if MEMSIZES_DEBUG
+#ifdef DEBUG_MEMSIZES
        printf ( "basememsize %d\n", meminfo.basememsize );
        printf ( "memsize %d\n",     meminfo.memsize );
        printf ( "Memory regions(%d):\n", meminfo.map_count );