[User-mode-linux-devel] new syscall, nits, quirks, and blue sky.

[William S. <wst...@po...>]

Good evening, Jeff,

On Sat, 11 Mar 2000, Jeff Dike wrote:

> > [wstearns@sparrow uml]$ touch vm_file 
> > [wstearns@sparrow uml]$ ./linux-2.3.49 devfs=nomount 
> > open: File exists 
> 
> The one thing that's important about vm_file is that it not exist beforehand.  
> That's the file that holds the kernel's physical memory.  It is opened (and 
> created) and then unlinked.

	Makes sense.

> What seems to be the problem is that your /dev/ttyp* files aren't usable by 
> anyone besides root.  Loosening up protections would help a lot.  Mine look 
> like this:
> 	crw-rw-rw-   1 root     tty        3,   0 May  5  1998 /dev/ttyp0

	Hmmm - tough to preassign modes when devfs (in the host OS)
creates them on the fly.  I'm sure there's some trickery in devfsd.conf
that would cause this to happen, but it's not clear what.  Oh well, use
root for the moment.

> Which reminds me that I'd better switch everything over to use /dev/pts 
> sometime...
> 
> Those diffs are innocuous.  Here's what they mean:
[snip]

	I have no problem believing that - thanks for the
explanation.


Unimplemented Syscall:
	And now to new business.  2.3.51-uml, debian root_fs-2.3.51,
started as root on a host 2.3.51.  I have the redhat root_fs loaded as
well (fhd1=rh6.2-root_fs on the command line, manually mounted inside
uml on /mnt/fhd1/; nifty trick, by the way!).
	I was trying to get a bash prompt completely inside the redhat
root partition, and thought that chroot would do the trick:
usermode:/etc/init.d# chroot /mnt/fhd1 /bin/bash
	uml hung on all three terminals.  Main console showed, slightly
mangled as I was running Midnight commander on it at the time:
Unimplemented syscall : 61
                          Untested (8987) [0x10171428]: syscall_kern.c line 696
	I take it this is the syscall for chroot?
	I suspect that simply doing the above with two copies of the
debian root_fs on fhd0 and fhd1 would _probably_ produce the same
effect; I don't _think_ this is some quirk of trying to switch between
debian and redhat.


Cosmetic:
	The terminals (console and both xterms) don't appear to be handle
some application requests.  Specifically, when booting redhat, their [ OK
] and [ FAILED ] prompts change color using, for example:
echo -en "\t\t\tWelcome to "
[ "$BOOTUP" != "serial" ] && echo -en "\\033[1;31m"
echo -en "Red Hat"
[ "$BOOTUP" != "serial" ] && echo -en "\\033[0;39m"
echo " Linux"
	to change the color of the words Red Hat.  Everything comes out
B&W.  Also, Midnight commander shows up (and even changes background color
via ncurses, but has incorrect line drawing characters on both the main
console and the xterms.  It also suffers from the same limitation that
SecureCRT on Windows has; the Function keys don't come through, so one
must use Esc-2 instead of F2.


Quirks:
...
Started device management daemon for /dev
Cleaning: /tmp /var/lock /var/runexec of "/sbin/rm" returned -2
exec of "/sbin/rm" returned -2
exec of "/sbin/rm" returned -2
...
	in booting.  Is this some search path quirk in Debian?  I've seen
this also in booting RH; it looks like that message may show up when an
application is searched for in each search directory.

...
INIT: Entering runlevel: 2
Starting system log daemon: syslogd  syslogd: /dev/xconsole: No such file
or directory
 klogd.
...
	I don't show /dev/xconsole on my system at all.  Is it needed?


Future:
	What are the chances that I might someday be able to pass off host
character or block devices to a uml incarnation?  For example:
./linux-2.3.51 ttyS0=/dev/ttyS0
./linux-2.3.51 fd0=/dev/fd0
	or perhaps better yet:
dd if=/dev/zero of=/home/wstearns/fakefloppy bs=1k count=1440
./linux-2.3.51 fd0=/home/wstearns/fakefloppy
	and have that host file accessed only when the uml mounts on its
own /dev/fd0?
	Granted, only one uml at a time could use a particular device in
the host, but...


2 points:
	Running top in the host OS is pretty cool - all the uml threads
label themelves with their job in the uml environment.  Nice touch!


	I've got to tell you, Jeff, it boggles my mind that one can do
this stuff at all!  Thanks again for all your work and patience with me.  
Let me know if I'm getting too nit-picky.
	Cheers,
	- Bill

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William Stearns (wst...@po...).  Mason, Buildkernel, named2hosts, 
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