doc/uImage.FIT/x86-fit-boot.txt

5 ----------
10 binary which contains all sorts of parameters and a compressed self-extracting
11 binary for the kernel itself, often with a small built-in serial driver to
15 understanding is that an x86 CPU (even a really new one) starts up in a 16-bit
16 'real' mode where only 1MB of memory is visible, moves to 32-bit 'protected'
18 then to 64-bit 'long' mode if 64-bit execution is required.
20 Partly the self-extracting nature of Linux was introduced to cope with boot
21 loaders that were barely capable of loading anything. Even changing to 32-bit
25 Bit by bit more and more logic has been added to this post-boot pre-Linux
28 - Changing to 32-bit mode
29 - Decompression
30 - Serial output (with drivers for various chips)
31 - Load address randomisation
32 - Elf loader complete with relocation (for the above)
33 - Random number generator via 3 methods (again for the above)
34 - Some sort of EFI mini-loader (1000+ glorious lines of code)
35 - Locating and tacking on a device tree and ramdisk
48 or in the boot loader rather than adding a self-relocator to put it in the
64 ----------------
66 Note: these instructions assume a 32-bit kernel. U-Boot also supports directly
67 booting a 64-bit kernel by jumping into 64-bit mode first (see below).
72 $ objdump -h vmlinux
74 vmlinux:     file format elf32-i386
160 U-Boot although I suppose you could mostly script it. This would permit the
167 ------------
169 To create a FIT you will need a source file describing what should go in the
171 the 'arch' value for booting 64-bit kernels if desired. Put this into a file
177 address so that U-Boot doesn't overwrite it when decompressing. Something like
184    objcopy -O binary vmlinux vmlinux.bin
190    mkimage -f image.its image.fit
192 (be careful to run the mkimage from your U-Boot tools directory since it
197 $ dumpimage -l image.fit
227 ---------------
240 tree then x86 doesn't normally use those - it has ACPI instead.
244 -----------
247 2. It allows use of the standard U-Boot boot file format
248 3. It allows U-Boot to perform decompression - problems will provide an error
250 4. It avoids all the pre-loader code in the kernel which is quite complex to
253 added to the pre-Linux
260 ----------
263 the kernel including the setup.bin format. This is handled in U-Boot in
269 --
272 7-Oct-2014