[U-Boot] [PATCH RFC] armv7: fixloop: don't fixup if location is NULL

[Andreas Bießmann]

Dear Minkyu Kang,

Am 11.01.2011 14:00, schrieb Andreas Bießmann:
> Dear Minkyu Kang,
> 
> Am 11.01.2011 11:57, schrieb Minkyu Kang:
> 
>>> Regardless of the patch, if your code writes to panel_info or any other BSS
>>> variable before relocation it will trash the relocation tables that exist at
>>> BSS location at this point.
>>>
>>> IOW, accessing BSS before relocation is forbidden, not just out of fancy,
>>> but for a serious reason.
>>
>> This patch is not for accessing BSS before relocation,
>> it's for prevent exceptions.
> 
> The real error is writing to BSS before relocation. This leads to a
> corrupted .rel.dyn section which is placed at the same address as .bss
> at this moment (bss is overloaded to save space).
> 
> If you look in your ELF (e.g. readelf -R .rel.dyn u-boot) you may see,
> that the .rel.dyn section does _not_ include a pointer to 0x0 with
> relative relocation (0x17) as you showed in a previous post.
> If you look in your u-boot.map you may find the function in question
> (test_func() was it in your example) is placed in .bss section. Setting
> the function pointer to 0 (e.g. test_func() = NULL, as described in
> previous mail) before relocation will destroy your .rel.dyn section and
> then you will see a zero in .rel.dyn section at some place ... please
> investigate the ELF and do not step through the code to find those issues.

You may have a look at http://patchwork.ozlabs.org/patch/73760 for an
TEST approach to see the damaged .rel.dyn, if you like this hackish
approach.

regards

Andreas Bießmann