[U-Boot] [PATCH v2] SPL: tiny-printf: avoid any BSS usage

[Simon Glass]

Hi,

On 9 July 2016 at 11:27, André Przywara <andre.przywara at arm.com> wrote:
> On 09/07/16 15:38, Simon Glass wrote:
>> On 8 July 2016 at 08:18, Andre Przywara <andre.przywara at arm.com> wrote:
>>> As printf calls may be executed quite early, we should avoid using any
>>> BSS stored variables, since some boards put BSS in DRAM, which may not
>>> have been initialised yet.
>>> Explicitly mark those "static global" variables as belonging to the
>>> .data section, to keep tiny-printf clear of any BSS usage.
>>>
>>> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
>>
>> Reviewed-by: Simon Glass <sjg at chromium.org>
>>
>> Another approach would be to put these vars in a struct, declare it as
>> a local variable and pass it around. But this works OK too.
>
> Yeah, I was thinking about this too. Actually fixing the issue that we
> need global variables in the first place.
> But a quick look revealed that this is not trivial, so I reverted to
> this simpler approach for the quick fix. Also I am not sure this will
> eventually work against this "tiny" idea, we will see.
>
> To be honest I think the real proper fix(TM) would be to provide a
> separate BSS section for any code that runs _before_ DRAM init. This
> should be a few bytes only and could easily live in SRAM.
> If the loading part of the SPL requires a bigger BSS, that's fine as it
> could still live in DRAM.
> I might bake a patch when I get bored ...

For reference I sent a patch to remove use of the data section:

http://patchwork.ozlabs.org/patch/656024/

>
> Cheers,
> Andre.

Regards,
Simon