Minimum.exe Text Size Outliers

Joel Sherrill joel at rtems.org
Wed May 26 17:23:10 UTC 2021


On Wed, May 26, 2021 at 6:02 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 25/05/2021 20:33, Christian Mauderer wrote:
> >
> >>
> >> I thought Sebastian added a "malloc" for the BSP to use before the
> >> heap was initialized. But I don't remember the name. Am I remembering
> >> correctly?
> >
> > I don't really know that malloc. But I doubt that it works that early.
> > Again: Copying the FDT is one of the first things that these BSPs do. If
> > you want to know the exact location: For ARM it's here:
> >
> > https://git.rtems.org/rtems/tree/bsps/arm/shared/start/start.S#n325
> >
> > So it's really basic setup before that. It's interrupt stack, switching
> > modes, setup stack pointer and then it's already copy FDT.
>
> Yes, there is an early "malloc". This is _Memory_Allocate() using
> _Memory_Get(). However, for the device tree copy this is not early
> enough. We don't know the device tree location provided by the boot
> loader. It could be somewhere in the memory area used by the
> application. So, it is important to copy this very early into a fixed
> location. Also, the device tree may be used to get the size of the
> memory provided by _Memory_Get().
>

I assume read-only is only from the perspective of higher level
language code. Is it possible that being read-only it could be
mapped to Flash?

For the purposes of minimum size analysis, I will subtract the
size of the FDT block from the minimum .text size and if it
is still over 64, flag it.

--joel

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