[Qemu-devel] qemu static elf boot

[Qemu-devel] qemu static elf boot

[Nicolas Ollinger]

Hi,

I just tried qemu and I am really impressed by its speed!

By reading vl.c, more precisely the part that loads the bzImage, I
realized how messy the linux boot process is (please don't flame :-)).

Would it be possible to have a program in the spirit of vl which will
just run a standard static ELF binary, passing the command line parameters
to it. This would allow booting some other OS's kernel with more direct
boot process, like for example NetBSD.

A sample (gzipped) ELF kernel is available at the URL

ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-1.6/i386/binary/kernel/netbsd-GENERIC.gz

Regards,
Nicolas.
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Re: [Qemu-devel] qemu static elf boot

[Fabrice Bellard]

Hi,

A static ELF loader would be easy to add, but I don't know what is the 
standard way to pass command line parameters to an OS. I agree that it 
is an important feature. Do you have images of a complete netbsd system 
(kernel with serial console + small disk image) ?

Fabrice.

Nicolas Ollinger wrote:
> Hi,
> 
> I just tried qemu and I am really impressed by its speed!
> 
> By reading vl.c, more precisely the part that loads the bzImage, I
> realized how messy the linux boot process is (please don't flame :-)).
> 
> Would it be possible to have a program in the spirit of vl which will
> just run a standard static ELF binary, passing the command line parameters
> to it. This would allow booting some other OS's kernel with more direct
> boot process, like for example NetBSD.
> 
> A sample (gzipped) ELF kernel is available at the URL
> 
> ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-1.6/i386/binary/kernel/netbsd-GENERIC.gz
> 
> Regards,
> Nicolas.

Re: [Qemu-devel] qemu static elf boot

[Nicolas Ollinger]

Hi,

> A static ELF loader would be easy to add, but I don't know what is the
> standard way to pass command line parameters to an OS. I agree that it
> is an important feature. Do you have images of a complete netbsd system
> (kernel with serial console + small disk image) ?

I put a small disk image, kernels, and some files and instructions to use
them under bochs (for comparison purpose) at the following URL:

http://www.ens-lyon.fr/~nollinge/netbsd_bochs/

It works under bochs but it is quite slow (PII/333 here).

Concerning the boot process, I think the following files are worth
reading, even if they are very NetBSD involved:

http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/i386/stand/boot/boot2.c?rev=1.1&content-type=text/x-cvsweb-markup
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/i386/stand/lib/exec.c?rev=1.18&content-type=text/x-cvsweb-markup
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/lib/libsa/loadfile.c?rev=1.7.4.2&content-type=text/x-cvsweb-markup
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/i386/stand/lib/startprog.S?rev=1.3&content-type=text/x-cvsweb-markup

=> [bootit] calls [exec_netbsd] calls [loadfile] calls [startprog].

Some involved headers:

http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/sys/reboot.h?rev=1.20&content-type=text/x-cvsweb-markup
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/sys/boot_flag.h?rev=1.3&content-type=text/x-cvsweb-markup
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/i386/stand/lib/bootinfo.h?rev=1.5&content-type=text/x-cvsweb-markup

A more general source of information concerning multi-OS booting would be
a complex bootloader like GRUB.

Nicolas.
-- 

Re: [Qemu-devel] qemu static elf boot

[Nicolas Ollinger]

Hi,

On Thu, 24 Jul 2003, Nicolas Ollinger wrote:

> I put a small disk image, kernels, and some files and instructions to use
> them under bochs (for comparison purpose) at the following URL:
>
> http://www.ens-lyon.fr/~nollinge/netbsd_bochs/

I just updated the content of the above webpage, it now contains a
bootable NetBSD/i386 filesystem which runs just (slowly) fine under bochs.

The kernel inside the filesystem is now relocated at 0x90000000 in order
to allow qemu boot. So with Fabrice's recent addition of real mode support
in qemu, vl is now able to charge the kernel into memory using the usual
bootloader. Unfortunately, for some reason, the kernel do not boot at all.
No abortion, no fatal error, just... void.

Regards,
Nicolas.
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