Re: [Qemu-devel] Qemu as Instruction Set Simulator without any OS

[Anitha Boyapati]

Hello Robin,

>> 1. For a microcontroller which doesn't have any OS support, can QEMU be
>> ported without any OS ?
>

> On the other hand, if your question could be rephrased as 'I want to add 
> support for a new microcontroller to qemu but I only want to run "bare-metal" 
> (not an OS or an application under an OS) software on the model', I think 
> that is certainly possible.
>


Yes,  this is what I have been looking for. Adding support for a new
micro-controller which doesn't support any OS yet.

>> 2. Can QEMU be used as a simple instruction set simulator with probably
>> gdb support for remote debugging? My guess is this would require a
>> bootloader to load the application to run the application program (full
>> system emulation mode or just machine emulation if there is something
>> like that). If yes, what else can be the blocker to have gdb support?
>
> IMHO, gdb support if available, is available irrespective of the type and 
> nature of the software being run on qemu. For example, you can create a 
> bare-metal application that executes from the reset vector for say, the ARM 
> or the MIPS models and have gdb support right from the outset. There is no 
> explicit need for running boot firmware and/or a loader to load an 
> application program. Not sure if that's what you were after.
>

My exact requirement is to test a gcc cross-compiler using DejaGnu for
a given target (AVR32). While the cross-compiler is ready, there is no
simulator. Since there is not much of OS support, I am trying to
evaluate if Qemu can still be considered for this purpose.

The usage scenario probably goes like this:

1. Qemu-target should be invoked with the application (yes,
bare-metal) waiting for some gdb connection.
2. target-gdb is invoked with the same application

I am referring to the example given in
http://wiki.qemu.org/download/qemu-doc.html#gdb_005fusage :

> qemu -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append 
> "root=/dev/hda"

However, in my case kernel image doesn't exist. As to the requirement
of bootloader, I need to investigate further as various types of
memories (FLASH & SRAM for program and data sections) exist.

> This does require system-mode emulation support as opposed to user-mode 
> emulation for your microcontroller to be implemented.

Agreed. System-mode emulation is what is required.

Thanks
Anitha