[U-Boot] [PATCH v3 0/9] Add a pre-relocation malloc() implementation

[Simon Glass]

Hi Tom,

On 14 July 2014 16:28, Tom Rini <trini at ti.com> wrote:
>
> On Thu, Jul 10, 2014 at 10:23:24PM -0600, Simon Glass wrote:
>
> > There has been talk on and off of a pre-relocation malloc() implementation.
> > Driver model needs this so that it can work before relocation.
> >
> > A previous implementation was sent in a v1 series.
> >
> > This implementation works by allocating space on the stack. The benefit is
> > that boards do not need to specify the address of the malloc() area, only
> > the size. The down-side is that due to the way board_init_f() is called,
> > architecture-specific code needs to be used to allocate the space.
> >
> > No clever algorithms are used to allocate space, free() is a nop and
> > realloc() is not supported. This fits well with the desire to avoid wasting
> > space on bucket tables and the hassle of supporting BSS data before
> > relocation. We don't expect 'churn' in the pre-relocation case - we just
> > want to allocate small amounts of memory temporarily.
> >
> > After relocation a new malloc() pool is created and the old one is lost,
> > although pointers into it will survive the immediate process of relocation.
> >
> > Implementations are provided for sandbox and arm (32-bit only).
> >
> > A related change is made to the early init for each arch to make this work.
>
> My concern without a fix right now is how to make use of this in SPL,
> when we're able to move SPL over to using still more generic code rather
> than re-inventing the board_init_{f,r} wheels, in the case where we init
> DRAM.

One option would be to split this new code out into a separate file,
and have two malloc() implementations:

- big one - falls back to small one pre-relocation
- small one - used for SPL

Regards,
Simon