[U-Boot-Users] [PATCH] Off-by-two bug when relocating GOT

[Thomas Lange]

Vlad Lungu wrote:
> Thomas Lange wrote:
>> Vlad Lungu wrote:
>>   
>>> Shinya Kuribayashi wrote:
>>>     
>>>> Vlad Lungu wrote:
>>>>   
>>>>       
>>>>> The first two entries are skipped but the number of relocated entries
>>>>> is not adjusted; as a result, the first __u_boot_cmd_* structure is
>>>>> smashed and no commands can be issued.
>>>>>     
>>>>>         
>>>> This is a known, long stading, pretty critical, but not fixed problem. See below:
>>>>
>>>> http://search.gmane.org/search.php?group=gmane.comp.boot-loaders.u-boot&query=mips+got
>>>>
>>>> I'm going to look closely into this.
>>>>   
>>>>       
>>> The thing I don't get is why skip the top two entries in the first place? Is it because 
>>> _gp=ALIGN(16) ? Maybe Robert has a point:
>>>
>>> http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/25533
>>>     
>> Yes, Roberts patch sent 12/15/06 09:53 worked for me when my command
>> table suddenly got corrupted.
>>   
> 
> That's my case:
>                 0x00000000bfc1d950                _gp = ALIGN (0x10)
>                 0x00000000bfc1d94c                __got_start = .
> 
> .got            0x00000000bfc1d950      0x500
>  *(.got)
>  .got           0x00000000bfc1d950      0x500 cpu/mips/start.o
>                 0x00000000bfc1d950                _GLOBAL_OFFSET_TABLE_
>                 0x00000000bfc1de50                __got_end = .
>                 0x00000000bfc1de50                . = .
>                 0x00000000bfc1de50                __u_boot_cmd_start = .
> 
>  The thing is,  num_got_entries=(__got_end - __got_start)>>2 and that's 
> 0x141 and it should be only 0x140.
> That is what triggers the bug. In start.S, lines 353-354, $t4 is loaded 
> with $gp+8 and $t2 with 2 and not with 0, so in effect
> if I substract 2 from $t3 I'm not relocating the last entry, and with 
> Robert's patch I'm not relocating the last two.
> One more point: loading  $gp with _GLOBAL_OFFSET_TABLE_ is not a good  
> idea, it should be loaded with _gp. The value
> is the same at the moment, but it's not guaranteed at all, someone could 
> start playing with the link scripts and break this.
>> It is still not applied to sources.
>>
>> Is it rejected/pending/forgotten?
>>   
> Well, it was not a "proper" patch so it kind of fell trought the cracks, 
> probably.
> This one is a "proper" patch but it's actually wrong, so please don't 
> apply it.

Hmm, are we talking about the same patch?

[PATCH] Fix: Bug in MIPS linker scripts
http://article.gmane.org/gmane.comp.boot-loaders.u-boot/25541/

Looks proper to me.

/Thomas