I've attached a description to each one which will provide some
guidance as to proceed with it. If you need more details, contact me
or send mail off to the uml-devel list.
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Add a mechanism for rereading module symbols when the module is reloaded.
The problem is that when you are debugging a module, and you rebuild it,
rmmod the old one, and insmod the new one, gdb remembers the symbols
from the previous module, and it's a pain to update the symbols
because you have to throw out all symbols, reload UML's symbol table,
and reload the module symbol table as described
here.
I'd like to have this done automatically by putting a breakpoint in
sys_init_module and have something do all the symbol refreshing. The
problem is that gdb isn't programmable enough to do it, so I'm
thinking about sticking a perl script between UML and gdb which will
watch things go back and forth, and when it sees that breakpoint being
hit, it will refresh all the symbols.
-
My attempts to run the Debian install procedure hung UML while it was
probing disks. I never figured out what was happening.
If someone verifies that UML can run a Debian installation, I'll
consider this fixed.
-
I need to figure out why some people
see 'Unexpectedly got signal 4 in signals'. This has been reported a
couple of times, but I've never got any information that would help me
debug it.
This popped up a few times, a long time ago. If no one complains
about it again when UML V1.0 is imminent, I'll just consider it fixed.
-
Make UML build without warnings
I've been knocking these off one by one. The remaining ones are
mostly cries for reorganization. There are pieces of userspace code
in kernel files which call libc functions without there being
declarations in scope. Mostly, these things need to be separated from
whatever kernel code they're in, and moved to a userspace file.
An exception to this is the pair of warnings from kernel/timer.c. I'm
going to fix this by bumping UML's HZ to 50.
Remember the errno redefinition warning in user_syms.c during the deb build.
-
Make sure that each clock tick gets counted
If you run UML under load for a while, you'll notice that clock ticks
are being missed. You can see this by doing a 'ps uax' every once in
a while, and noticing that process start times are moving. I made an
attempt to fix this by never having SIGVTALRM or SIGALRM blocked and
doing some fancy flag checking to make sure that the IRQ handler is
only called if it's safe, and otherwise just bumping a count of missed
ticks. The next time it's safe, the IRQ handler will be called once
for the current tick and once for each previously missed tick,
catching the system up with the real time.
This doesn't fix it for some reason. The only reason I can think of
is that the signals are getting stacked because a second one comes in
before the first one has been collected by the handler. I have a hard
time believing that the host can be so bogged down that it can't call
the signal handler within 1/HZ seconds of the alarm happening. The
signal is going through the tracing thread courtesy of ptrace, so
maybe that's introducing enough delay to stack the signals.
-
Figure out the hostfs crash that Larent Bonnaud is seeing
Laurent hasn't complained about this recently. If he doesn't, I'll
just consider this fixed.
-
make 'gdb=pty' work
Run UML with 'debug gdb=pty' on the command line, attach to whatever
pty gdb gets, and you'll see the problem. There's some major problem
with the terminal modes that I've never figured out.
-
protect kernel memory from userspace
Fixing this will make it impossible for a nasty UML user to escape
from UML and execute arbitrary system calls on the host. It has four
pieces:
-
Write-protect kernel physical and virtual memory whenever UML is in
userspace. The exception to this is the process kernel stack, which
needs to be writable in order for a signal handler to be run on it.
This is OK because whatever the process puts there will just be
overwritten by the signal handler. This is partially implemented -
kernel physical memory is protected, except for the four pages making
up the task structure and stack. Protecting the task structure is
complicated because there is some UML code which effectively runs in
userspace which calls the process signal handler to deliver signals.
It needs to be able to write to the task structure. I think this fix
is to move that code to before the signal starts being delivered,
which will involve redoing parts of the signal delivery code.
Protecting kernel virtual memory is a matter of walking the kernel
page tables and write-protecting everything that's mapped there.
-
Locating and disabling all drivers that provide access to kernel
memory through interfaces such as /proc/kcore.
-
Fixing the access_ok macro so it rejects any attempt to fake the
kernel into changing its own memory by passing a kernel address as an
argument to a system call.
-
In the host kernel, adding a new personality which segfaults any
attempt to execute a SysV system call. These are not traced by
ptrace, so a process that knows how to use them is not jailed inside UML.
-
Figure out why the io_thread loses its parent and its connection to the kernel
This happened once, a long time ago. The system hung because the IO
thread lost its connection to UML somehow. I haven't seen it since,
so this will probably be considered fixed.
-
Get either Myrtal Meep or Matt Clay
to confirm (or not) that they can no longer crash UML with
Apache/Perl/MySQL. This will probably be fixed with the new network drivers.
The new network drivers probably fixed these problems. This will be
considered fixed unless people start complaining about it again.
-
Someone needs to try booting UML as a diskless client via bootp and
make sure that it works.
People have complained that this doesn't work. We need to check it
and make sure that it does now.
-
I have a bug that says that diskless booting doesn't work because it's
impossible to assign an address to a network interface from the
command line. However, I've heard of someone booting diskless
successfully, so this needs to be cleared up.
This probably works. Someone just needs to confirm it.
-
I have an old bug that claims that UML can be crashed with a ping
flood. I haven't seen this happen recently, so if anyone else has,
you'd better let me know.
This is probably fixed. I do ping floods fairly regularly and haven't
seen any problems.
-
Disable SIGIO on file descriptors which are already being handled.
This will cut off some interrupt recursion.
This is an efficiency thing and stack depth precaution. We don't want
sigio_handler to run recursively on the same descriptor because the
descriptor will be handled at the top level.
-
Figure out why gdb can't use fd chan (blinky@gmx.net)
One of the ioctls that sets up the terminal for gdb returns EPERM.
-
Figure out why repeated 'tail /dev/zero' with swap causes process segfaults
I stopped being able to reproduce this, so it might be considered
mysteriously fixed at some point.
-
The ptrace proxy should handle wait correctly for non-UML subprocesses of gdb
Shelling out of the kernel debugger will cause a hang. That's because
the ptrace proxy is not prepared for a real wait for a real child to
happen.
-
Set SA_RESTART on SIGPROF
This will prevent SIGPROF from causing system calls on the host from
returning EINTR and messing things up inside UML.
-
Figure out why hostfs panics when it's on an nfs directory on the host
(David Coulson)
For some reason, hostfs is confused by an NFS filesystem on the host
even though it shouldn't be able to tell the difference from a normal
local filesystem.
-
Figure out why the Debian ping is slower than the Slackware ping
I think this is because one version of ping is calling a system call
that returns times in units of clock ticks and doing calculations
based on the assumption that HZ == 100.
-
Support SIGWINCH
This involves the chan code catching SIGWINCH and passing it to the
process through the tty system. This is now supported on the main
console. The problem with supporting it everywhere else is that those
terminals aren't controlling terminals, so they don't deliver SIGWINCH.
-
Allow registration of sockets for panics and console output
This involves some work on the mconsole client side to support making
the requests and work in UML to add the mconsole notification to the
panic_notify_chain and to somehow get console output to the client.
My best idea on doing this is to add support for multiple channels on
consoles and support for write-only channels. Then the mconsole
client can stack a write-only channel to a socket or something on top
of whatever channel is already there.
-
Replace dentry_name with d_name
Cleanup - I implemented dentry_name, not knowing about d_name, which
does the same thing. One problem might be that dentry_name expects
the file to exist, which might cause something to break when d_name
returns a '/foo/bar/baz (deleted)' name.
-
Bind a UML unix socket to a host unix socket
This is a cute feature which would involve passing something like
'hostsock=/tmp/.X11-unix/X0,X' on the command line, which would cause
the hostsock driver to create a /proc/hostsock/X unix socket inside
UML and pass all operations and data on it through to the host's
/tmp/.X11-unix/X0. Then, you'd create /tmp/.X11-unix/X0 in UML as a
link to /proc/hostsock/X and be able to run X clients on the host X
server without needing the network up.
-
Dynamically allocate all driver descriptors
The static arrays in the drivers should go away and be replaced by
dynamically allocated buffers, maybe in a list. This will turn
lookups of particular devices into O(N) operations, but maybe that's
OK. Also, the transport arrays in the various transports should
similarly go away.
-
Make slip_tramp conditional in slip_close
slip_open doesn't always invoke the helper through slip_tramp, so
slip_close similarly shouldn't.
-
Version the mconsole and uml_router interfaces
This is to provide some backward compatibility and detection of
incompatible tools and kernels.
-
Implement thread_saved_pc
This is an unimplemented piece of the SysRq support.
-
many du / causes slab cache corruption
This wasn't entirely reproducable, but I did see a couple cases of
panics with slab corruption when running a lot of du's. I fixed the
process segfault problem, and this problem has probably disappeared as
well.
-
ddd doesn't work with gdb-pid
ddd seems to be doing something strange wrt gdb. When 'att 1' is done,
gdb just dies and becomes a zombie.
-
Removing a block device with the mconsole doesn't remove its entry in
/proc/partitions
I looked at this briefly and didn't see where the entry is getting added
in the first place.
-
Adding an eth device via the mconsole (and probably the command line)
won't necessarily configure the device that was named
The kernel does its own ordering of devices, so configuring eth1 without
configuring eth0 gives you eth0.
-
Figure out why running a properly built UML under UML doesn't work
-
Allow a COW file to change its backing file with
'ubdx=cow-file,new-backing-file'
This assigns some potentially useful semantics to a syntax that is
currently meaningless. Currently, the backing-file argument is
ignored for an already-existing COW file.
-
Implement /proc/umid
This would let UML be configured on the inside with knowledge of what
instance it is.
-
Figure out why leaning on the space bar when top is running causes an FPE.
I'm suspicious that this is caused by UML not saving floating point
state when it enters the kernel and somehow munging the process
floating point registers.
-
'i reg' to gdb inside UML doesn't print the fp registers
-
Get the fp registers in core files correctly.
-
Fix the ubd rounding bug spotted by Steve Schmidtke and Roman Zippel.
If the number of sectors isn't a multiple of 8, then the bitmap will
be a a byte shorter than it should be.
-
Byte-swap the ubd bitmap (Roman Zippel)
-
gdb should be the last thing to be shut down so that breakpoints can
be set late in the shutdown process.
-
The register state in the sigcontext passed in to a signal handler should
be copied into the process registers when the handler returns.
-
Have the __uml_exitcall handlers check to see if they need to do anything.
If UML is ^C-ed before things are set up, then the cleanup handlers are
cleaning up after things which were never initialized.
-
Using strace as an external debugger doesn't work. strace sees no system
calls starting at the delay calibration.