Re: [Qemu-arm] Booting Cortex-M3 Linux kernels in qemu

[Guenter Roeck <linux@roeck-us.net>]

Hi Peter,

On Wed, Jun 20, 2018 at 09:52:00AM +0100, Peter Maydell wrote:
> On 19 June 2018 at 18:43, Guenter Roeck <linux@roeck-us.net> wrote:
> > Thanks a lot for the link; that gave me enough information to find
> > a solution that is not too invasive and works for me.
> >
> > I need to be able to run a single kernel image against multiple
> > devicetree files and root file systems. This doesn't work with
> > above solution since it bundles everything together (or, rather,
> > it would break my workflow). However, it was easy enough to tweak the
> > boot wrapper and load it using "-bios". I added support for "-bios",
> > "-initrd", and "-dtb" to mps2_common_init(). That change is simple
> > enough to carry in my private qemu branch.
> 
> Glad you found something that works for you.
> 
> It is also possible to write a bootwrapper that loads a
> kernel/initrd via the semihosting ABI (assuming you trust
> your guest, since semihosting lets it read/write arbitrary
> host files).
> https://git.linaro.org/arm/models/boot-wrapper.git/
> is an example of doing that for A-profile.
> 

The simple bootloader does its job, and I prefer to have a uniform user
interface - it would really be nice to have consistent support for -bios,
-initrd, and -dtb in qemu. Getting it with ~70 LOC are worth it, even
if I'll have to carry the code along myself.

The last problem I had was that either uclibc-ng or Linux doesn't support
pthreads without MM. With pthreads disabled in buildroot (and with the
cmsdk-apb-timer fix I submitted), I am able to boot an-385 to shell.

Thanks,
Guenter