[U-Boot] [RFC] arm926ejs: fix jump to RAM nand_boot

[Albert ARIBAUD]

Le 01/11/2010 10:15, Wolfgang Denk a écrit :
> Dear Albert ARIBAUD,
>
> In message<4CCDF5FC.4060704 at free.fr>  you wrote:
>>
>> Wolfgang, could you:
>>
>> - make available to me the exact source tree you're compiling, including
>> my patches as you applied them plus your changes to them, either as a
>> clonable git repo or as a patch set to apply on the current u-boot
>> master branch;
>
> Please see git://git.denx.de/u-boot-testing.git , branch reloc-tests
>
>> - indicate exactly how you build your u-boot;
>
> Both with ELDK and CS tools:
>
> ../MAKELL tx25
>
>> - provide the u-boot binary that you last built (the one that has no
>> output).
>
> Will send two tarballs (built with ELDK and CS) in PM.
>
>> My goal here is to reproduce an u-boot identical to yours, in order to
>> make sur I can produce controlled u-boots for tx25, and then build some
>> specific tx25 u-boots for you to run.
>
> Thanks!

Thanks. With all this I am able to rebuild u-boot identically to yours; 
our maps only differ by the absolute path of the source code.

Also, I understand why the second RFC change I did was harmful to tx25. 
Contrary to u-boot itself, u-boot-spl is not compiled to be position 
independent; it actually loads at a given address then copies itself, 
without relocating, to its home location.

I also think I might have found out what hit tx25.

include/configs/tx25 defines the size of u-boot which SPL will use to 
load from NAND into RAM. currently it is defined thus:

#define CONFIG_SYS_NAND_U_BOOT_SIZE	0x30000

However, looking at the output of 'readelf -a dump of u-boot' 
(whitespace compressed to preserve formatting):

Section Headers:
[Nr] Name        Type     Addr     Off    Size   ES Flg Lk Inf Al
[ 0]             NULL     00000000 000000 000000 00      0   0  0
[ 1] .text       PROGBITS 81200000 008000 01b550 00  AX  0   0 32
[ 2] .rodata     PROGBITS 8121b550 023550 006082 00   A  0   0  4
[ 3] .hash       HASH     812215d4 0295d4 00003c 04   A  9   0  4
[ 4] .data       PROGBITS 81221610 029610 001de4 00  WA  0   0  4
[ 5] .got.plt    PROGBITS 812233f4 02b3f4 00000c 04  WA  0   0  4
[ 6] .u_boot_cmd PROGBITS 81223400 02b400 0003f0 00  WA  0   0  4
[ 7] .bss        NOBITS   812237f0 02b7f0 009108 00  WA  0   0  8
[ 8] .rel.dyn    REL      8122c8f8 02c8f8 003c60 08   A  9   0  4
[ 9] .dynsym     DYNSYM   81230558 030558 0000a0 10   A  0   3  4

See how .rel.dyn crosses the limit of 0x812230000, and .dynsym is 
completely beyond this limit? That means the SPL won't load the whole of 
rel.dyn and won't load any of .dynsym, but u-boot does not know it, so:

- it will run the fixup loop beyond 0x81230000 nnd up to 0x81230558, at 
best doing no harm if no 'relocation record' in that area is of type 2 
or 23, at most corrupting memory randomly if any 'relocation record' in 
that area happens to be type 2 or 23;

- it will not apply the fixup records generated by the linker and which 
landed at 0x81230000 and beyond.

Wolfgang, please try the following:

- on u-boot-testing, branch reloc_tests, revert commit 7fab02d... 
(that's "arm926ejs: fix jump to RAM nand_boot") as this 'fix' is a mistake.

- in include/configs/tx25.h, increasing CONFIG_SYS_NAND_U_BOOT_SIZE to 
0x31000

Let me know if building tx25 after these two corrections makes things 
better.

Amicalement,
-- 
Albert.