Hi Michael,
> Currently, Pearcolator simulates a linux environment by intercepting
> system calls and handling these, as if the binary was running on
> linux.
Right, that's like qemu's "user emulation" IIRC.
http://fabrice.bellard.free.fr/qemu/status.html
> However, I would like to extend that research project so that
> Pearcolator can also simulate enough hardware, to actually boot a
> simple operating system instead of "only" intercepting the system
> calls. Currently, I am simulating all ARM instructions, but no
> additional hardware at all. Therefore, I was wondering what kind of
> hardware I would actually have to simulate to get a basic linux
> running - is simulating a memory mapped serial interface enough or do
> I also need a DMA controller, HD controller or ...?
I think Michael Dales covered this, but IIRC Linux needs a processor,
clock, memory controller, and interrupt controller. You normally want
some I/O on top of that, e.g. a UART for a serial port. An initial RAM
disk can contain your user-space programs that you want to run once the
kernel boots, avoiding the need to emulate a hard disc interface.
> The reason I was asking here is that you seem to be experts on
> simulating hardware, considering arcem is able to emulate quite a lot.
> I knew about QEMU, but until know I though they would also only
> intercept the system calls - but according to your interesting links,
> they also seem to be able to simulate a bit of hardware, too.
Yes, their "system emulation" means they're emulating the hardware of
the machine. I run the x86 emulator in this mode with Ubuntu 7.04
running on top of it. The Linux kernel in Ubuntu thinks it's talking to
real hardware.
> On your homepage, you are also offering an ARMLinux ROM image
> (http://arcem.sourceforge.net/linuxrom.zip). Do you know what kind of
> hardware emulation is required to run this image?
That (very old) version of ARMLinux was intended to run on an Acorn,
like arcem emulates. You really don't want to do that as it means
emulating VIDC, etc., and that's all old hardware that no one other than
Acorn emulator people are interested in anymore.
I'd suggest talking to the ARM qemu guys, or examining the source, to
find a simple embedded ARM development board that qemu's system
emulation implements. One that's modern enough to have up to date Linux
support. You'll be able to pick up pre-configured kernels for qemu that
you can run under qemu to observe. At the same time qemu's source will
show what bits of hardware are emulated and how. You may be able to
drop support for some of the bits, e.g. network interface, in your
emulator once you're happy reconfiguring the kernel compilation.
Cheers,
Ralph.
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