Hi Wolfgang,
So far U-Boot is actually a 32 bit boot loader; address calculations like this "just wrap around". So far this has not caused problems yet; what has caused problems is that we can have overlapping sections on 4xx. Also it's probably overkill that each board has it's own linker script.
I added some debug and came to the same conclusion about the wrapping math.
Full ack on the linker script consolidation.
I would like to see this fixed in this process. Maybe Stefan finds some spare cycles to address this.
Where is BSS on 44x boards? I dont see any reason we shouldn't be able to put it at the same location.
From the XPedite1000:
[ 0] NULL 00000000 000000 000000 00 0 0 0 [ 1] .resetvec PROGBITS fffffffc 03f2e4 000004 00 AX 0 0 1 [ 2] .bootpg PROGBITS fffff000 03e2e8 000250 00 AX 0 0 1 [ 3] .text PROGBITS fff80000 000094 0303b0 00 AX 0 0 4 [ 4] .rodata PROGBITS fffb03b0 030444 00a14c 00 A 0 0 4 [ 5] .reloc PROGBITS fffba500 03a594 002280 00 WA 0 0 4 [ 6] .data PROGBITS fffbc780 03c814 00088c 00 WA 0 0 4 [ 7] .data.rel.local PROGBITS fffbd00c 03d0a0 000a98 00 WA 0 0 4 [ 8] .data.rel.ro.loca PROGBITS fffbdaa4 03db38 0000b0 00 WA 0 0 4 [ 9] .data.rel PROGBITS fffbdb54 03dbe8 000100 00 WA 0 0 4 [10] .u_boot_cmd PROGBITS fffbdc54 03dce8 000600 00 WA 0 0 4 [11] .bss NOBITS fffbe300 03e2e8 011c44 00 WA 0 0 4
I shied away from this for the 2 reasons above - the bootpg section will be wiped out when the bss is cleared for images near their maximum size
I think it will not be needed any more by then.
Its not currently used (at least on 85xx), but I know using it had been mentioned in the past. There's a >3K chunk that's sitting empty right now that could be used. All things being equal I think it would be ideal not to trash a section of U-Boot code - it could be useful and at some point someone's going to be banging their head on the wall trying to figure out why some chunk of assembly code isn't working.
If everyone is OK with the limitation of #1 above I can make the 85xx act like the other PPC boards. The only downside I see is that we could never put any non-reset related code in the bootpg.
What about my suggestion to chose a fixed (random, non-zero) address?
I'd vote against this. It'd have to be some area in low memory and people would be bound to accidentally stomp on it and cause all sorts of odd errors- like overwriting the exception vectors, but harder to debug. I personally like the current implementation of putting the bss after the entire U-Boot image. It keeps U-Boot's code, malloc pool, stack, bss, etc all in the same general area which is nice, and has the side benefit that the bootpg won't be overwritten.
I know ORing in 0x10 is a bit ugly, but what's the real downside of doing it?
Best, Peter