don't get too scared about the subject line.
LAR is a very capable format. With two simple extensions, we can use LAR to replace all that we are using ELF for now. This change can really make life better: 1. we can use streaming decompress instead of the current "uncompress elf to memory and then copy segments" approach. So we can get rid of THIS hardcode: #define UNCOMPRESS_AREA (0x400000) 2. A simple lar l can show ALL segments, including payload segments 3. It's really easy to see where things will go in memory, and catch problems 4. We can figure out an ELF input file is bogus BEFORE we flash, not AFTER we flash and try to boot it 5. did I mention streaming decompress? 6. We no longer have to worry about where we decompress the elf in memory (this problem was causing trouble when the payload was a linux kernel -- it was so big) 7. Since we have a load address, we can create this lar entry: normal/cmdline and specify that it be loaded at a place where linux will find it as the cmdline. 8. The decision on whether to XIP can be made in the LAR entry, not in hardcode. For example, if initram needs to be XIP, set the load address to 0xffffffff. Done.
The change is simple. Add a load address and entry point to the lar header. Extend the lar tool to parse the elf file and create multiple lar segments. It looks like this: normal/payload0 (33192 bytes, lzma compressed to 18088 bytes @0x38 load @0x100000, entry 0x105258) normal/payload1 (72 bytes, lzma compressed to 47 bytes @0x4718 load @0x1225a0, entry 0x105258) normal/option_table (932 bytes @0x4798 load @0, entry 0) normal/stage2 (33308 bytes, lzma compressed to 15474 bytes @0x4b78 load @0, entry 0) normal/initram (4208 bytes @0x8828 load @0, entry 0) linuxbios.bootblock (16384 bytes @0xfc000 load @0, entry 0)
note that the payload is now payload0, payload1, etc. I've extended linuxbios to look for these. Note that you can now see all the things that get loaded ;they're no longer hidden in an ELF header somewhere. Elf failures are gone!
Note that I've left legacy elf support in, for now, but recommend we get rid of it as soon as possible.
patch attached. This is a first pass. lar.c needs some refactoring but I want to get the comments going. You can now have a linux payload and it will uncompress with no problems.
This has been tested with filo and BOCHS.
ron