Assemble the blob in memory before writing it out.

index 151d16e..caff758 100644
@@ -310,6 +310,7 @@ static struct data flatten_reserve_list(struct reserve_info *reservelist,
 	
 	return d;
 }
+
 static void make_bph(struct boot_param_header *bph,
 		     struct version_info *vi,
 		     int reservesize, int dtsize, int strsize,

@@ -332,19 +333,8 @@ static void make_bph(struct boot_param_header *bph,
 	bph->off_dt_struct = cpu_to_be32(reserve_off + reservesize);
 	bph->off_dt_strings = cpu_to_be32(reserve_off + reservesize
 					  + dtsize);
-	bph->totalsize = reserve_off + reservesize + dtsize + strsize;
-	if (minsize > 0) {
-		if (bph->totalsize >= minsize) {
-			if (quiet < 1)
-				fprintf(stderr,
-					"Warning: blob size %d >= minimum size %d\n",
-					bph->totalsize, minsize);
+	bph->totalsize = cpu_to_be32(reserve_off + reservesize + dtsize + strsize);
 
-		} else
-			bph->totalsize = minsize;
-	}
-	bph->totalsize = cpu_to_be32(bph->totalsize);
-		
 	if (vi->flags & FTF_BOOTCPUID)
 		bph->boot_cpuid_phys = cpu_to_be32(boot_cpuid_phys);
 	if (vi->flags & FTF_STRTABSIZE)

@@ -358,11 +348,11 @@ void dt_to_blob(FILE *f, struct boot_info *bi, int version,
 {
 	struct version_info *vi = NULL;
 	int i;
-	struct data dtbuf = empty_data;
-	struct data strbuf = empty_data;
-	struct data reservebuf;
+	struct data blob       = empty_data;
+	struct data reservebuf = empty_data;
+	struct data dtbuf      = empty_data;
+	struct data strbuf     = empty_data;
 	struct boot_param_header bph;
-	struct reserve_entry termre = {.address = 0, .size = 0};
 
 	for (i = 0; i < ARRAY_SIZE(version_table); i++) {
 		if (version_table[i].version == version)

@@ -371,9 +361,6 @@ void dt_to_blob(FILE *f, struct boot_info *bi, int version,
 	if (!vi)
 		die("Unknown device tree blob version %d\n", version);
 
-	dtbuf = empty_data;
-	strbuf = empty_data;
-
 	flatten_tree(bi->dt, &bin_emitter, &dtbuf, &strbuf, vi);
 	bin_emit_cell(&dtbuf, OF_DT_END);
 

@@ -383,28 +370,46 @@ void dt_to_blob(FILE *f, struct boot_info *bi, int version,
 	make_bph(&bph, vi, reservebuf.len, dtbuf.len, strbuf.len,
 		 boot_cpuid_phys);
 
-	fwrite(&bph, vi->hdr_size, 1, f);
-
-	/* Align the reserve map to an 8 byte boundary */
-	for (i = vi->hdr_size; i < be32_to_cpu(bph.off_mem_rsvmap); i++)
-		fputc(0, f);
+	/*
+	 * Assemble the blob: start with the header, add with alignment
+	 * the reserve buffer, add the reserve map terminating zeroes,
+	 * the device tree itself, and finally the strings.
+	 */
+	blob = data_append_data(blob, &bph, sizeof(bph));
+	blob = data_append_align(blob, 8);
+	blob = data_merge(blob, reservebuf);
+	blob = data_append_zeroes(blob, sizeof(struct reserve_entry));
+	blob = data_merge(blob, dtbuf);
+	blob = data_merge(blob, strbuf);
 
 	/*
-	 * Reserve map entries.
-	 * Each entry is an (address, size) pair of u64 values.
-	 * Always supply a zero-sized temination entry.
+	 * If the user asked for more space than is used, pad out the blob.
 	 */
-	fwrite(reservebuf.val, reservebuf.len, 1, f);
-	fwrite(&termre, sizeof(termre), 1, f);
+	if (minsize > 0) {
+		int padlen = minsize - be32_to_cpu(bph.totalsize);
+
+fprintf(stderr, "minsize = %d, totalsize = %d, padlen = %d\n", minsize, be32_to_cpu(bph.totalsize), padlen);
+		if (padlen > 0) {
+			blob = data_append_zeroes(blob, padlen);
+			bph.totalsize = cpu_to_be32(minsize);
+		} else {
+			if (quiet < 1)
+				fprintf(stderr,
+					"Warning: blob size %d >= minimum size %d\n",
+					be32_to_cpu(bph.totalsize), minsize);
+		}
+	}
 
-	fwrite(dtbuf.val, dtbuf.len, 1, f);
-	fwrite(strbuf.val, strbuf.len, 1, f);
+	fwrite(blob.val, blob.len, 1, f);
 
 	if (ferror(f))
 		die("Error writing device tree blob: %s\n", strerror(errno));
 
-	data_free(dtbuf);
-	data_free(strbuf);
+	/*
+	 * data_merge() frees the right-hand element so only the blob
+	 * remains to be freed.
+	 */
+	data_free(blob);
 }
 
 static void dump_stringtable_asm(FILE *f, struct data strbuf)

@@ -447,7 +452,7 @@ void dt_to_asm(FILE *f, struct boot_info *bi, int version, int boot_cpuid_phys)
 	emit_label(f, symprefix, "blob_start");
 	emit_label(f, symprefix, "header");
 	fprintf(f, "\t.long\tOF_DT_HEADER /* magic */\n");
-	fprintf(f, "\t.long\t_%s_blob_end - _%s_blob_start /* totalsize */\n",
+	fprintf(f, "\t.long\t_%s_blob_abs_end - _%s_blob_start /* totalsize */\n",
 		symprefix, symprefix);
 	fprintf(f, "\t.long\t_%s_struct_start - _%s_blob_start /* off_dt_struct */\n",
 		symprefix, symprefix);

@@ -504,6 +509,15 @@ void dt_to_asm(FILE *f, struct boot_info *bi, int version, int boot_cpuid_phys)
 
 	emit_label(f, symprefix, "blob_end");
 
+	/*
+	 * If the user asked for more space than is used, pad it out.
+	 */
+	if (minsize > 0) {
+		fprintf(f, "\t.space\t%d - (_%s_blob_end - _%s_blob_start), 0\n", 
+			minsize, symprefix, symprefix);
+	}
+	emit_label(f, symprefix, "blob_abs_end");
+
 	data_free(strbuf);
 }