[openwrt/openwrt] scripts: sercomm-kernel-header.py: improve compatibility

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch openwrt-23.05:
https://git.openwrt.org/63942b569e08a6190ec9096a03d184127b8f3f71

commit 63942b569e08a6190ec9096a03d184127b8f3f71
Author: Mikhail Zhilkin <csharper2005 at gmail.com>
AuthorDate: Fri Dec 2 15:26:17 2022 +0000

    scripts: sercomm-kernel-header.py: improve compatibility
    
    This improves compatibility with the elder stock firmwares of the
    following devices, which have not yet been merged into OpenWrt:
     - Beeline SmartBox Pro
     - Beeline SmartBox Turbo+
     - WiFire S1500.NBN
    
    Without this, OpenWrt factory image installation may fail.
    
    Signed-off-by: Mikhail Zhilkin <csharper2005 at gmail.com>
    Signed-off-by: Maximilian Weinmann <x1 at disroot.org>
    (cherry picked from commit 35a4418d3966ccf6229916b0021bd18871ef22dd)
---
 scripts/sercomm-kernel-header.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/sercomm-kernel-header.py b/scripts/sercomm-kernel-header.py
index bfb29c6fe0..40bcbb1385 100755
--- a/scripts/sercomm-kernel-header.py
+++ b/scripts/sercomm-kernel-header.py
@@ -48,12 +48,12 @@ def get_kernel_header(args):
 	struct.pack_into('<L', header, 0x2c, rootfs_size)
 	struct.pack_into('<L', header, 0x30, crc)
 
-	rootfs_end_offset = args.rootfs_offset + rootfs_size
-	struct.pack_into('<L', header, 0x4, rootfs_end_offset)
-
 	kernel_size = os.path.getsize(args.kernel_file)
 	struct.pack_into('<L', header, 0x14, kernel_size)
 
+	kernel_end_offset = args.kernel_offset + kernel_size
+	struct.pack_into('<L', header, 0x4, kernel_end_offset)
+
 	buf = open(args.kernel_file,'rb').read()
 	crc = binascii.crc32(buf) & 0xffffffff
 	struct.pack_into('<L', header, 0x18, crc)