kernel: mtdsplit: add support for brnImages

This adds brnImage (used with the brnboot bootloader) firmware parsing
support. brnboot verifies the integrity of the firmware stored on the
"Code Image" partitions by looking at the 12 byte footer at the very end
of the partition. This footer contains the checksum of the original
brnImage (kernel + rootfs/squashfs) and must not be touched (by our JFFS2
rootfs_data - otherwise the image will not be bootable anymore).

Big thanks to Mathias Kresin for analyzing the brnImage structure and
finding out the information how to keep images valid even when adding a
nested rootfs_data partition.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48261 3c298f89-4303-0410-b956-a3cf2f4a3e73

3 files changed, 110 insertions, 0 deletions

diff --git a/target/linux/generic/files/drivers/mtd/mtdsplit/Kconfig b/target/linux/generic/files/drivers/mtd/mtdsplit/Kconfig
index c4e3418854..0370a21c9f 100644
--- a/target/linux/generic/files/drivers/mtd/mtdsplit/Kconfig
+++ b/target/linux/generic/files/drivers/mtd/mtdsplit/Kconfig
@@ -49,3 +49,8 @@ config MTD_SPLIT_TRX_FW
 	bool "TRX image based firmware partition parser"
 	depends on MTD_SPLIT_SUPPORT
 	select MTD_SPLIT
+
+config MTD_SPLIT_BRNIMAGE_FW
+	bool "brnImage (brnboot image) firmware parser"
+	depends on MTD_SPLIT_SUPPORT
+	select MTD_SPLIT
diff --git a/target/linux/generic/files/drivers/mtd/mtdsplit/Makefile b/target/linux/generic/files/drivers/mtd/mtdsplit/Makefile
index e09476bc20..ca24c717dc 100644
--- a/target/linux/generic/files/drivers/mtd/mtdsplit/Makefile
+++ b/target/linux/generic/files/drivers/mtd/mtdsplit/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_MTD_SPLIT_FIT_FW) += mtdsplit_fit.o
 obj-$(CONFIG_MTD_SPLIT_LZMA_FW) += mtdsplit_lzma.o
 obj-$(CONFIG_MTD_SPLIT_TPLINK_FW) += mtdsplit_tplink.o
 obj-$(CONFIG_MTD_SPLIT_TRX_FW) += mtdsplit_trx.o
+obj-$(CONFIG_MTD_SPLIT_BRNIMAGE_FW) += mtdsplit_brnimage.o
diff --git a/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_brnimage.c b/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_brnimage.c
new file mode 100644
index 0000000000..7ddd69b7b7
--- /dev/null
+++ b/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_brnimage.c
@@ -0,0 +1,104 @@
+/*
+ *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
+ *  Copyright (C) 2015 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/byteorder/generic.h>
+
+#include "mtdsplit.h"
+
+#define BRNIMAGE_NR_PARTS	2
+
+#define BRNIMAGE_ALIGN_BYTES	0x400
+#define BRNIMAGE_FOOTER_SIZE	12
+
+#define BRNIMAGE_MIN_OVERHEAD	(BRNIMAGE_FOOTER_SIZE)
+#define BRNIMAGE_MAX_OVERHEAD	(BRNIMAGE_ALIGN_BYTES + BRNIMAGE_FOOTER_SIZE)
+
+static int mtdsplit_parse_brnimage(struct mtd_info *master,
+				struct mtd_partition **pparts,
+				struct mtd_part_parser_data *data)
+{
+	struct mtd_partition *parts;
+	uint32_t buf;
+	unsigned long rootfs_offset, rootfs_size, kernel_size;
+	size_t len;
+	int ret;
+
+	for (rootfs_offset = 0; rootfs_offset < master->size;
+	     rootfs_offset += BRNIMAGE_ALIGN_BYTES) {
+		ret = mtd_check_rootfs_magic(master, rootfs_offset);
+		if (!ret)
+			break;
+	}
+
+	if (ret)
+		return ret;
+
+	if (rootfs_offset >= master->size)
+		return -EINVAL;
+
+	ret = mtd_read(master, rootfs_offset - BRNIMAGE_FOOTER_SIZE, 4, &len,
+			(void *)&buf);
+	if (ret)
+		return ret;
+
+	if (len != 4)
+		return -EIO;
+
+	kernel_size = le32_to_cpu(buf);
+
+	if (kernel_size > (rootfs_offset - BRNIMAGE_MIN_OVERHEAD))
+		return -EINVAL;
+
+	if (kernel_size < (rootfs_offset - BRNIMAGE_MAX_OVERHEAD))
+		return -EINVAL;
+
+	/*
+	 * The footer must be untouched as it contains the checksum of the
+	 * original brnImage (kernel + squashfs)!
+	 */
+	rootfs_size = master->size - rootfs_offset - BRNIMAGE_FOOTER_SIZE;
+
+	parts = kzalloc(BRNIMAGE_NR_PARTS * sizeof(*parts), GFP_KERNEL);
+	if (!parts)
+		return -ENOMEM;
+
+	parts[0].name = KERNEL_PART_NAME;
+	parts[0].offset = 0;
+	parts[0].size = kernel_size;
+
+	parts[1].name = ROOTFS_PART_NAME;
+	parts[1].offset = rootfs_offset;
+	parts[1].size = rootfs_size;
+
+	*pparts = parts;
+	return BRNIMAGE_NR_PARTS;
+}
+
+static struct mtd_part_parser mtdsplit_brnimage_parser = {
+	.owner = THIS_MODULE,
+	.name = "brnimage-fw",
+	.parse_fn = mtdsplit_parse_brnimage,
+	.type = MTD_PARSER_TYPE_FIRMWARE,
+};
+
+static int __init mtdsplit_brnimage_init(void)
+{
+	register_mtd_parser(&mtdsplit_brnimage_parser);
+
+	return 0;
+}
+
+subsys_initcall(mtdsplit_brnimage_init);