Re: TARGET_SYS_HEAPINFO and Cortex-A15 memory map

[Peter Maydell]

On Mon, 25 Jul 2022 at 18:02, Liviu Ionescu <ilg@livius.net> wrote:
> > On 25 Jul 2022, at 19:02, Peter Maydell <peter.maydell@linaro.org> wrote:
> > The one where SYS_HEAPINFO produces the bogus result putting the
> > heap at 0x04000000, that you mentioned in the original report with
> > the command line
> >
> > .../qemu-system-arm "--machine" "virt" "--cpu" "cortex-a15"
> > "--nographic" "-d" "unimp,guest_errors" "--semihosting-config"
> > "enable=on,target=native,arg=sample-test,arg=one,arg=two" -s -S
>
> ah, the bogus one... that's a bit more complicated, since it happened in the 
> early tests, and I don't remember how I did it, it might be that I tried to 
> load my code in flash and my data in ram, but I'm not sure.
>
> try to check the logic and avoid the cases when flash addresses are returned 
> for heap, if possible.

Yeah, that's my plan. I think it'll be a one-line fix. But it'll
be much easier to be sure it works if I have a test case that
triggers the problem. I'll try a setup with code in flash and
data in RAM, that sounds like it might be a way to cause the
problem if there's not much code and a lot of data (because
then the remaining space in the flash is larger than the
remaining space in the RAM.)

> btw, this might be a different topic, but on Cortex-M devices
> I'm used to configure the linker scripts to allocate the text
> in flash and the data+bss in ram; for qemu aarch32/64 devices
> I could not make this work, and I had to allocate everything
> in ram, which is functional, but probably not very accurate
> for some tests, that might fail when running from flash.

I'm not a linker/toolchain expert, I'm afraid. Certainly in
theory it should be possible to have a split text/data setup
on A-profile devices, the same as M-profile ones.

thanks
-- PMM