malloc: use variable for ZoneHigh size

Use the variable highram_size instead of the BUILD_MAX_HIGHTABLE #define
for the ZoneHigh size. Initialize the new variable with the old #define,
so behavior does not change.

This allows to easily adjust the ZoneHigh size at runtime in a followup
patch.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

src/malloc.c

@@ -422,7 +422,8 @@ malloc_preinit(void)
     e820_add(BUILD_BIOS_ADDR, BUILD_BIOS_SIZE, E820_RESERVED);
 
     // Populate temp high ram
-    u32 highram = 0;
+    u32 highram_start = 0;
+    u32 highram_size = BUILD_MAX_HIGHTABLE;
     int i;
     for (i=e820_count-1; i>=0; i--) {
         struct e820entry *en = &e820_list[i];
@@ -432,10 +433,10 @@ malloc_preinit(void)
         if (en->type != E820_RAM || end > 0xffffffff)
             continue;
         u32 s = en->start, e = end;
-        if (!highram) {
-            u32 newe = ALIGN_DOWN(e - BUILD_MAX_HIGHTABLE, MALLOC_MIN_ALIGN);
+        if (!highram_start) {
+            u32 newe = ALIGN_DOWN(e - highram_size, MALLOC_MIN_ALIGN);
             if (newe <= e && newe >= s) {
-                highram = newe;
+                highram_start = newe;
                 e = newe;
             }
         }
@@ -444,9 +445,9 @@ malloc_preinit(void)
 
     // Populate regions
     alloc_add(&ZoneTmpLow, BUILD_STACK_ADDR, BUILD_EBDA_MINIMUM);
-    if (highram) {
-        alloc_add(&ZoneHigh, highram, highram + BUILD_MAX_HIGHTABLE);
-        e820_add(highram, BUILD_MAX_HIGHTABLE, E820_RESERVED);
+    if (highram_start) {
+        alloc_add(&ZoneHigh, highram_start, highram_start + highram_size);
+        e820_add(highram_start, highram_size, E820_RESERVED);
     }
 }