How to use images in the new image format ========================================= Author: Bartlomiej Sieka Overview -------- The new uImage format allows more flexibility in handling images of various types (kernel, ramdisk, etc.), it also enhances integrity protection of images with sha1 and md5 checksums. Two auxiliary tools are needed on the development host system in order to create an uImage in the new format: mkimage and dtc, although only one (mkimage) is invoked directly. dtc is called from within mkimage and operates behind the scenes, but needs to be present in the $PATH nevertheless. It is important that the dtc used has support for binary includes -- refer to git://git.kernel.org/pub/scm/utils/dtc/dtc.git for its latest version. mkimage (together with dtc) takes as input an image source file, which describes the contents of the image and defines its various properties used during booting. By convention, image source file has the ".its" extension, also, the details of its format are given in doc/uImage.FIT/source_file_format.txt. The actual data that is to be included in the uImage (kernel, ramdisk, etc.) is specified in the image source file in the form of paths to appropriate data files. The outcome of the image creation process is a binary file (by convention with the ".itb" extension) that contains all the referenced data (kernel, ramdisk, etc.) and other information needed by U-Boot to handle the uImage properly. The uImage file is then transferred to the target (e.g., via tftp) and booted using the bootm command. To summarize the prerequisites needed for new uImage creation: - mkimage - dtc (with support for binary includes) - image source file (*.its) - image data file(s) Here's a graphical overview of the image creation and booting process: image source file mkimage + dtc transfer to target + ---------------> image file --------------------> bootm image data file(s) SPL usage --------- The SPL can make use of the new image format as well, this traditionally is used to ship multiple device tree files within one image. Code in the SPL will choose the one matching the current board and append this to the U-Boot proper binary to be automatically used up by it. Aside from U-Boot proper and one device tree blob the SPL can load multiple, arbitrary image files as well. These binaries should be specified in their own subnode under the /images node, which should then be referenced from one or multiple /configurations subnodes. The required images must be enumerated in the "loadables" property as a list of strings. If a platform specific image source file (.its) is shipped with the U-Boot source, it can be specified using the CONFIG_SPL_FIT_SOURCE Kconfig symbol. In this case it will be automatically used by U-Boot's Makefile to generate the image. If a static source file is not flexible enough, CONFIG_SPL_FIT_GENERATOR can point to a script which generates this image source file during the build process. It gets passed a list of device tree files (taken from the CONFIG_OF_LIST symbol). Example 1 -- old-style (non-FDT) kernel booting ----------------------------------------------- Consider a simple scenario, where a PPC Linux kernel built from sources on the development host is to be booted old-style (non-FDT) by U-Boot on an embedded target. Assume that the outcome of the build is vmlinux.bin.gz, a file which contains a gzip-compressed PPC Linux kernel (the only data file in this case). The uImage can be produced using the image source file doc/uImage.FIT/kernel.its (note that kernel.its assumes that vmlinux.bin.gz is in the current working directory; if desired, an alternative path can be specified in the kernel.its file). Here's how to create the image and inspect its contents: [on the host system] $ mkimage -f kernel.its kernel.itb DTC: dts->dtb on file "kernel.its" $ $ mkimage -l kernel.itb FIT description: Simple image with single Linux kernel Created: Tue Mar 11 17:26:15 2008 Image 0 (kernel) Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Size: 943347 Bytes = 921.24 kB = 0.90 MB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2ae2bb40 Hash algo: sha1 Hash value: 3c200f34e2c226ddc789240cca0c59fc54a67cf4 Default Configuration: 'config-1' Configuration 0 (config-1) Description: Boot Linux kernel Kernel: kernel The resulting image file kernel.itb can be now transferred to the target, inspected and booted (note that first three U-Boot commands below are shown for completeness -- they are part of the standard booting procedure and not specific to the new image format). [on the target system] => print nfsargs nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} => print addip addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}:${netdev}:off panic=1 => run nfsargs addip => tftp 900000 /path/to/tftp/location/kernel.itb Using FEC device TFTP from server 192.168.1.1; our IP address is 192.168.160.5 Filename '/path/to/tftp/location/kernel.itb'. Load address: 0x900000 Loading: ################################################################# done Bytes transferred = 944464 (e6950 hex) => iminfo ## Checking Image at 00900000 ... FIT image found FIT description: Simple image with single Linux kernel Created: 2008-03-11 16:26:15 UTC Image 0 (kernel) Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Start: 0x009000e0 Data Size: 943347 Bytes = 921.2 kB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2ae2bb40 Hash algo: sha1 Hash value: 3c200f34e2c226ddc789240cca0c59fc54a67cf4 Default Configuration: 'config-1' Configuration 0 (config-1) Description: Boot Linux kernel Kernel: kernel => bootm ## Booting kernel from FIT Image at 00900000 ... Using 'config-1' configuration Trying 'kernel' kernel subimage Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Start: 0x009000e0 Data Size: 943347 Bytes = 921.2 kB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2ae2bb40 Hash algo: sha1 Hash value: 3c200f34e2c226ddc789240cca0c59fc54a67cf4 Verifying Hash Integrity ... crc32+ sha1+ OK Uncompressing Kernel Image ... OK Memory BAT mapping: BAT2=256Mb, BAT3=0Mb, residual: 0Mb Linux version 2.4.25 (m8@hekate) (gcc version 4.0.0 (DENX ELDK 4.0 4.0.0)) #2 czw lip 5 17:56:18 CEST 2007 On node 0 totalpages: 65536 zone(0): 65536 pages. zone(1): 0 pages. zone(2): 0 pages. Kernel command line: root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-4.1/ppc_6xx ip=192.168.160.5:192.168.1.1::255.255.0.0:lite5200b:eth0:off panic=1 Calibrating delay loop... 307.20 BogoMIPS Example 2 -- new-style (FDT) kernel booting ------------------------------------------- Consider another simple scenario, where a PPC Linux kernel is to be booted new-style, i.e., with a FDT blob. In this case there are two prerequisite data files: vmlinux.bin.gz (Linux kernel) and target.dtb (FDT blob). The uImage can be produced using image source file doc/uImage.FIT/kernel_fdt.its like this (note again, that both prerequisite data files are assumed to be present in the current working directory -- image source file kernel_fdt.its can be modified to take the files from some other location if needed): [on the host system] $ mkimage -f kernel_fdt.its kernel_fdt.itb DTC: dts->dtb on file "kernel_fdt.its" $ $ mkimage -l kernel_fdt.itb FIT description: Simple image with single Linux kernel and FDT blob Created: Tue Mar 11 16:29:22 2008 Image 0 (kernel) Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Size: 1092037 Bytes = 1066.44 kB = 1.04 MB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2c0cc807 Hash algo: sha1 Hash value: 264b59935470e42c418744f83935d44cdf59a3bb Image 1 (fdt-1) Description: Flattened Device Tree blob Type: Flat Device Tree Compression: uncompressed Data Size: 16384 Bytes = 16.00 kB = 0.02 MB Architecture: PowerPC Hash algo: crc32 Hash value: 0d655d71 Hash algo: sha1 Hash value: 25ab4e15cd4b8a5144610394560d9c318ce52def Default Configuration: 'conf-1' Configuration 0 (conf-1) Description: Boot Linux kernel with FDT blob Kernel: kernel FDT: fdt-1 The resulting image file kernel_fdt.itb can be now transferred to the target, inspected and booted: [on the target system] => tftp 900000 /path/to/tftp/location/kernel_fdt.itb Using FEC device TFTP from server 192.168.1.1; our IP address is 192.168.160.5 Filename '/path/to/tftp/location/kernel_fdt.itb'. Load address: 0x900000 Loading: ################################################################# ########### done Bytes transferred = 1109776 (10ef10 hex) => iminfo ## Checking Image at 00900000 ... FIT image found FIT description: Simple image with single Linux kernel and FDT blob Created: 2008-03-11 15:29:22 UTC Image 0 (kernel) Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Start: 0x009000ec Data Size: 1092037 Bytes = 1 MB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2c0cc807 Hash algo: sha1 Hash value: 264b59935470e42c418744f83935d44cdf59a3bb Image 1 (fdt-1) Description: Flattened Device Tree blob Type: Flat Device Tree Compression: uncompressed Data Start: 0x00a0abdc Data Size: 16384 Bytes = 16 kB Architecture: PowerPC Hash algo: crc32 Hash value: 0d655d71 Hash algo: sha1 Hash value: 25ab4e15cd4b8a5144610394560d9c318ce52def Default Configuration: 'conf-1' Configuration 0 (conf-1) Description: Boot Linux kernel with FDT blob Kernel: kernel FDT: fdt-1 => bootm ## Booting kernel from FIT Image at 00900000 ... Using 'conf-1' configuration Trying 'kernel' kernel subimage Description: Vanilla Linux kernel Type: Kernel Image Compression: gzip compressed Data Start: 0x009000ec Data Size: 1092037 Bytes = 1 MB Architecture: PowerPC OS: Linux Load Address: 0x00000000 Entry Point: 0x00000000 Hash algo: crc32 Hash value: 2c0cc807 Hash algo: sha1 Hash value: 264b59935470e42c418744f83935d44cdf59a3bb Verifying Hash Integrity ... crc32+ sha1+ OK Uncompressing Kernel Image ... OK ## Flattened Device Tree from FIT Image at 00900000 Using 'conf-1' configuration Trying 'fdt-1' FDT blob subimage Description: Flattened Device Tree blob Type: Flat Device Tree Compression: uncompressed Data Start: 0x00a0abdc Data Size: 16384 Bytes = 16 kB Architecture: PowerPC Hash algo: crc32 Hash value: 0d655d71 Hash algo: sha1 Hash value: 25ab4e15cd4b8a5144610394560d9c318ce52def Verifying Hash Integrity ... crc32+ sha1+ OK Booting using the fdt blob at 0xa0abdc Loading Device Tree to 007fc000, end 007fffff ... OK [ 0.000000] Using lite5200 machine description [ 0.000000] Linux version 2.6.24-rc6-gaebecdfc (m8@hekate) (gcc version 4.0.0 (DENX ELDK 4.1 4.0.0)) #1 Sat Jan 12 15:38:48 CET 2008 Example 3 -- advanced booting ----------------------------- Refer to doc/uImage.FIT/multi.its for an image source file that allows more sophisticated booting scenarios (multiple kernels, ramdisks and fdt blobs).