[U-Boot-Users] Question About how the CPU find the right string address in U-boot binary file ?

[Kenneth Johansson <kenneth@southpole.se>]

On Thu, 2008-06-05 at 09:50 +0800, wang baohua wrote:
> Dear Johansson,
>  Thanks for your reply. Your reply is very clear, that's just my
> question. In fact, I am study a
> MIPS binary file, but I cannot find any resource, so I turn to PowerPC
> platform and try to get
> clear understand about the string loading process.

I'm not sure how similar MIPS is to ppc ABI.  

> I want to ask according to your reply:
> 1. fff0358c: 80 7e 80 00     lwz r3,-32768(r30)
>    Is the -32768 stand for  " entry 0 in the .got table" ?  Why such a
> translate in objdump?

It's not objectdump that do this it's the compiler that generate the
code like this. r30 is a pointer to the GOT table but the pointer is
located so that it's possible to use the full range of the 16 bit signed
offset. that is if the GOT table only have one entry the r30 value would
be pointing outside of the table but since it's accessed with a singed
offset it will still work. 

> 2. I found the .got2 section in the U-boot.map, can you tell me how to
> calc the right string address (traps.o) ?
>    .reloc          0xfff34000     0x1578
>    *(.got)
>                      0xfff34000                _GOT2_TABLE_ = .
>   *(.got2)
>  .got2          0xfff34000       0x24 cpu/mpc8260/start.o
>  .got2          0xfff34024       0x4c cpu/mpc8260/libmpc8260.a(traps.o)

?? I thought this was obvious. to get the entry from the code take the
offset value used in the load and subtract -32768 to get the offset into
the .got2 section. at that address will be a 32 bit address that is the
address of the string. 

> thanks!