[U-Boot] [PATCH v3 2/2] MIPS: Stop building position independent code

[Álvaro Fernández Rojas]

Hi Paul,

El 31/07/2017 a las 19:13, Paul Burton escribió:
> On Monday, 31 July 2017 03:52:57 PDT Daniel Schwierzeck wrote:
>> 2017-07-30 18:04 GMT+02:00 Álvaro Fernández Rojas <noltari at gmail.com>:
>>> El 30/07/2017 a las 16:05, Daniel Schwierzeck escribió:
>>>> Am 30.07.2017 um 14:27 schrieb Álvaro Fernández Rojas:
>>>>> I've been a bit busy lately and I couldn't test this until now, but I
>>>>> have to say that this commit breaks u-boot bmips support :(
>>>>>
>>>>> BTW, I tried this on several bmips boards (one of them is a Netgear
>>>>> CG3100D, which uses u-boot.bin instead of u-boot.elf)
>>>>>
>>>>> Do you have any idea on what could be hapenning?
>>>>
>>>> maybe you need to specify "--emit-relocs" too when linking u-boot.elf
>>>> from u-boot-elf.o. But u-boot-elf.o should already contain the correct
>>>> .reloc section with the updated relocation entries so you don't need to
>>>> rerun the reloc-tool on u-boot.elf.
>>>
>>> I tried that and it doesn't work.
>>> However, I've just found out that if I remove the relocs call it boots
>>> again... https://gist.github.com/Noltari/ce3a6a9dda69e74caf7ba33c9c8ade9a
>>
>> I wonder how this can work. Even the u-boot.elf now contains
>> position-dependent code so that an update of the relocation entries is
>> required there too. Without the updated entries, U-Boot can't execute
>> after jumping from relocate_code() to board_init_r(). Did you use a
>> clean build if U-Boot?
> 
> Indeed - without the .rel section being generated by the mips-relocs tool I'd 
> expect relocate_code() to either apply some bogus relocations or none at all 
> (depending what's in the memory starting from __rel_start) and then, if it 
> gets there at all, for the "relocated" U-Boot to fall over pretty quickly.
Is it possible that CFE is taking care of that?
For what I've seen in old versions of CFE, it looks like it does some parsing of the .elf files:
https://github.com/Noltari/cfe_bcm63xx/blob/master/cfe/cfe/main/cfe_ldr_elf.c
"This program parses ELF executables and loads them into memory"

> 
> Fernandez - I don't suppose you're aware of an emulated version of any of the 
> supported bmips systems? That would be an easy way for me to take a look. FYI 
> the systems I use most (Boston & Malta) also use u-boot.bin or derivatives 
> thereof & I'm sure the .rel section is copied across to it, so I doubt it has 
> anything to do with binary formats.
Nope, sorry but I've never emulated any bmips hardware...

> 
> Thanks,
>     Paul
> 

Regards,
Álvaro.