--- ./arch/ppc64/kernel/prom.c.orig	2004-03-17 14:28:46.000000000 -0500
+++ ./arch/ppc64/kernel/prom.c	2004-03-24 08:09:02.000000000 -0500
@@ -155,6 +155,15 @@ char *bootdevice = 0;
 int boot_cpuid = 0;
 #define MAX_CPU_THREADS 2

+/*
+ * 'ramdisk_start' is used to ensure the initrd image is not overwritten
+ * when the device tree is constructed in memory.
+ */
+#ifdef CONFIG_BLK_DEV_INITRD
+static unsigned long ramdisk_start = 0;
+#endif
+
+
 struct device_node *allnodes = 0;
 /* use when traversing tree through the allnext, child, sibling,
  * or parent members of struct device_node.
@@ -1796,6 +1805,9 @@ copy_device_tree(unsigned long mem_start
 	unsigned long offset = reloc_offset();
 	unsigned long mem_end = mem_start + (8<<20);

+#ifdef CONFIG_BLK_DEV_INITRD
+	mem_end = RELOC(ramdisk_start) - 1;
+#endif
 	root = call_prom(RELOC("peer"), 1, 1, (phandle)0);
 	if (root == (phandle)0) {
 		prom_panic(RELOC("couldn't get device tree root\n"));
@@ -1804,6 +1816,15 @@ copy_device_tree(unsigned long mem_start
 	mem_start = DOUBLEWORD_ALIGN(mem_start);
 	new_start = inspect_node(root, 0, mem_start, mem_end, &allnextp);
 	*allnextp = 0;
+	if (new_start > mem_end) {
+		prom_print(RELOC("Insufficient space for device tree:"));
+		prom_print(RELOC("  size allocated = 0x"));
+		prom_print_hex(mem_end - mem_start);
+		prom_print(RELOC(",  size required = 0x"));
+		prom_print_hex(new_start - mem_start);
+		prom_print_nl();
+		prom_exit();
+	}
 	return new_start;
 }

@@ -3242,6 +3263,7 @@ prom_bi_rec_reserve(unsigned long mem)
 			switch (rec->tag) {
 #ifdef CONFIG_BLK_DEV_INITRD
 			case BI_INITRD:
+				RELOC(ramdisk_start) = rec->data[0];
 				lmb_reserve(rec->data[0], rec->data[1]);
 				break;
 #endif /* CONFIG_BLK_DEV_INITRD */