[U-Boot] [PATCH v4 1/2] dlmalloc: fix malloc range at end of ram

[Simon Goldschmidt]

On Thu, Apr 25, 2019 at 1:59 AM Simon Glass <sjg at chromium.org> wrote:
>
> Hi,
>
> On Wed, 24 Apr 2019 at 05:53, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Wed, Apr 24, 2019 at 01:49:52PM +0200, Simon Goldschmidt wrote:
> > > On Wed, Apr 24, 2019 at 1:27 PM Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > On Tue, Apr 23, 2019 at 09:54:10PM -0600, Simon Glass wrote:
> > > > > On Mon, 1 Apr 2019 at 14:01, Simon Goldschmidt
> > > > > <simon.k.r.goldschmidt at gmail.com> wrote:
> > > > > >
> > > > > > If the malloc range passed to mem_malloc_init() is at the end of address
> > > > > > range and 'start + size' overflows to 0, following allocations fail as
> > > > > > mem_malloc_end is zero (which looks like uninitialized).
> > > > > >
> > > > > > Fix this by subtracting 1 of 'start + size' overflows to zero.
> > > > > >
> > > > > > Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> > > > > > ---
> > > > > >
> > > > > > Changes in v4: None
> > > > > > Changes in v3: None
> > > > > >
> > > > > >  common/dlmalloc.c | 4 ++++
> > > > > >  1 file changed, 4 insertions(+)
> > > > >
> > > > > Reviewed-by: Simon Glass <sjg at chromium.org>
> > > >
> > > > So, the problem with this patch is that it increases the generic malloc
> > > > code size ever so slightly and blows up smartweb :(
> > >
> > > Ehrm, ok, so how do we proceed?
> >
> > A good question.  Take a look at spl/u-boot-spl.map on smartweb and see
> > if, of the malloc functions it doesn't discard there's something that
> > maybe could be optimized somewhere?
>
> I wonder if we should have a Kconfig option like SPL_CHECKS which
> enables these sorts of minor checks, which may only fix one board at
> the cost of code size?
>
> Then it could be enabled by default, but disabled on this board?

For a bigger change, this might be an idea, but for a change that I can cut
down to 16 or even 8 bytes code size increasement, I don't think having a
new option would be good.

Anyway, I just tried at work and I don't get the overflow. Tom, which gcc
are you using to get the size error? It works for me on Debian 9 but doesn't
work with Ubuntu (both times, default cross compiler toolchain installed).

Regards,
Simon