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[Qemu-devel] qemu-system-arm and bootloader emulation


From: Peter Chubb
Subject: [Qemu-devel] qemu-system-arm and bootloader emulation
Date: Thu, 29 Sep 2011 12:26:20 +1000
User-agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (Goj┼Ź) APEL/10.8 Emacs/23.3 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO)

Currently, qemu-system-arm attempts to emulate a simple boot-loader if 
it thinks it is booting a u-boot image or a raw image (see
hw/arm-boot.c), and not if it's booting an ELF image.

I think this is a little backwards: when I give a raw ROM image as
argument I want no boot-loader, and when I give an ELF image I want
a bootloader to do its stuff, particularly when emulating an MP
system.

And sometimes a uimage is something that is a rom image (and doesn't
need a bootloader) and sometimes it is a Linux or other OS kernel
(that may need some bootloader support).

I'm not sure what the `right' thing to do is: but I would like more
control over whether the bootloader code is executed.  One possibility
is to provide an environment variable, say, `QEMU_RAW'.  Another is to
look at the load address --- if it's equal to boot_info->loader_start
then this is a raw ROM image and qemu should treate the first few
bytes as the reset vector, and otherwise emulate the boot-loader.

What do you think?
--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia



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