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

[Tom Rini]

On Mon, Apr 29, 2019 at 03:16:02PM +0200, Simon Goldschmidt wrote:
> Hello Heiko,
> 
> On Mon, Apr 29, 2019 at 3:06 PM Heiko Schocher <hs at denx.de> wrote:
> >
> > Hello Simon,
> >
> > Am 25.04.2019 um 21:24 schrieb Simon Goldschmidt:
> > > Am 25.04.2019 um 12:50 schrieb Tom Rini:
> > >> On Thu, Apr 25, 2019 at 09:32:22AM +0200, Simon Goldschmidt wrote:
> > >>> 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).
> > >>
> > >> I'm using the gcc-7.3 from kernel.org that we use in travis/etc.
> > >
> > > Ok, so I have gcc-7.3 on my Ubuntu machine as well. I don't know why 6.3 seems to produce smaller
> > > binaries (I thought they were getting smaller with new versions, not larger).
> > >
> > > However, I've stripped down that patch to +8 Bytes only and sent v5.
> >
> > Thanks!
> >
> > Sorry for digging so late in, but I was on vacation...
> >
> > Hmm.. the smartweb board has only 4k sram for SPL, and I have no chance
> > to convert it to DM to get rid of some compiler warnings ...
> >
> > I am unsure what to do now with this hardware ...
> 
> And things even get worse: as I wrote in the other thread, after updating to
> Ubuntu 19.04 as build system, I get gcc 8.3 as cross compiler and smartweb
> fails to build with that compiler (as the SPL binary is exactly 4k now).

Which reminds me that fixing the various warnings we get with gcc-8.x
would be a good general thing to do. :(

-- 
Tom
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