Re: TARGET_SYS_HEAPINFO and Cortex-A15 memory map

[Liviu Ionescu]

> On 25 Jul 2022, at 19:02, Peter Maydell <peter.maydell@linaro.org> wrote:
> 
> 
> We document what the guest can assume about the virt board
> memory layout here:
> 
> https://www.qemu.org/docs/master/system/arm/virt.html#hardware-configuration-information-for-bare-metal-programming
> 
> Flash at 0, RAM at 0x4000_0000, must look in the DTB blob
> for all other information.

ah, ok, I probably missed this. :-(

btw, looking in the dtb blob is probably not a problem for a linux kernel, but 
if I want only to write a simple test that needs a timer, getting the timer 
address is probably more complicated than my entire test... :-(

> 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.

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.


regards,

Liviu