First version

src/arch/i386/core/load_buffer.c

@@ -0,0 +1,64 @@
+#include "limits.h"
+#include "io.h"
+#include "memsizes.h"
+#include "init.h"
+#include "buffer.h"
+
+/*
+ * Initialise a buffer in an unused portion of memory, to be used for
+ * loading an image
+ *
+ */
+
+/* Under KEEP_IT_REAL, always use 07c0:0000 as the buffer.  Otherwise,
+ * use a reset_fn that finds the largest available block of RAM.
+ */
+struct buffer load_buffer = {
+	.start = 0x7c00,
+	.end = 0xa0000,
+};
+
+#ifndef KEEP_IT_REAL
+
+extern char _text[];
+
+static void init_load_buffer ( void ) {
+	unsigned int i;
+	unsigned long size = 0;
+
+	load_buffer.start = 0;
+	load_buffer.end = 0;
+
+	/* Find the largest usable segment in memory */
+	for ( i = 0 ; i < meminfo.map_count ; i++ ) {
+		unsigned long r_start, r_end;
+
+		if ( meminfo.map[i].type != E820_RAM )
+			continue;
+
+		if ( meminfo.map[i].addr + meminfo.map[i].size > ULONG_MAX )
+			continue;
+
+		r_start = meminfo.map[i].addr;
+		r_end = meminfo.map[i].size;
+
+		/* Avoid overlap with Etherboot.  Etherboot will be
+		 * located towards the top of a segment, so we need
+		 * only consider one-sided truncation.
+		 */
+		if ( ( r_start <= virt_to_phys ( _text ) ) &&
+		     ( virt_to_phys ( _text ) < r_end ) ) {
+			r_end = virt_to_phys ( _text );
+		}
+
+		if ( r_end - r_start > size ) {
+			size = r_end - r_start;
+			load_buffer.start = r_start;
+			load_buffer.end = r_end;
+		}
+	}
+}
+
+INIT_FN ( INIT_HEAP, init_load_buffer, init_load_buffer, NULL );
+		 
+#endif