[U-Boot] EABI 4.2

[Praveen G K]

On Thu, Mar 11, 2010 at 4:11 AM, Martin Krause <Martin.Krause at tqs.de> wrote:
> Joakim Tjernlund wrote on Wednesday, March 10, 2010 6:29 PM:
>> "Martin Krause" <Martin.Krause at tqs.de> wrote on 2010/03/10 17:52:40:
>>>
>>> Hi Jocke,
>>>
>>> Joakim Tjernlund wrote on Wednesday, March 10, 2010 5:36 PM:
>>>>> Andrew Dyer wrote on Wednesday, March 10, 2010 4:50 PM: [SNIP]
>>>>>
>>>>> Hm, on the wikipedia article for the 'variable length arrays'
>>>>> (VLA) I read, that the GNU C compiler always uses the stack for
>>>>> this type of variables. So I think, if the stack is working for
>>>>> all other local variables, it should not be an memory layout
>>>>> problem.
>>>>>
>>>>> Eventually the following might be interesting. I have tried to make
>>>>> the VLA much bigger, to eliminate 'normal' buffer overrun problems:
>>>>>
>>>>> char filename[dirent.namelen + 1 + 2048]
>>>>>
>>>>> But this leads to the same result, U-Boot dies. With an fixed
>>>>> length array of comparable length it works:
>>>>>
>>>>> char filename[2048]
>>>>>
>>>>> Both (local) variables should end up on the stack.
>>>>
>>>> Try alloca to see if stack allocs works at all in your toolchain.
>>>
>>> I didn't find alloca(), so I tried it with __builtin_alloca().
>>
>> Did you do #include <alloca.h> ?
>
> Yes, but then I get an "ext2fs.c:31:20: error: alloca.h: No such file
> or directory" error. I'm using an older Version of U-Boot, though ...
> (U-Boot 1.3.4).
>
>> __builtin_alloca should work too.
>>
>>> The result is the same as with variable length array - u-boot
>>> dies during the ext2ls command call.
>>>
>>> Does this mean, my toolchain is broken? I use ELDK4.2 for ARM.
>>
>> I belive so, how many bytes is in dirent.namelen? alloca can not
>
> In the first call 2 bytes, in the second call 3 bytes, and then
> U-Boot dies.
So, should I send a message to the gcc mailing list explaining the issue?
>> handle to big allocs (arch dependant) and will silently fail is it is
>> too big.
>>
>> VLA might be impl. using alloca so if alloca is broken, probably VLA
>> too.
>
> This sounds plausible.
>
> I compiled the original code with VLA with ELDK4.1 and there
> everything works. And also the '__builtin_alloca' Version works
> with ELDK4.1.
>
> Regards,
> Martin
>
>