Initial commit of virtme.

Signed-off-by: Andy Lutomirski <[email protected]>

.gitignore

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+*~
+__pycache__

README.md

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+What is virtme?
+===============
+
+Virtme is a set of simple tools to run a virtualized Linux kernel that
+uses the host Linux distribution instead of a separate image.
+
+Virtme is tiny, easy to use, and makes testing kernel changes quite simple.
+
+Some day this might be useful as a sort of sandbox.  Right now it's not
+really configurable enough for that.
+
+How to use virtme
+=================
+
+You'll need a Linux kernel compiled with these options:
+
+    CONFIG_VIRTIO=y
+    CONFIG_VIRTIO_PCI=y
+    CONFIG_NET_9P=y
+    CONFIG_NET_9P_VIRTIO=y
+    CONFIG_9P_FS=y
+
+
+Virtme does not (yet) support modular virtio or 9p, so you can't use your
+distro kernel.  Fixing this is a high priority.
+
+Once you have such a kernel, run:
+
+    virtme-runkernel PATH_TO_BZIMAGE
+
+On x86, you can usually find a bzImage in `arch/x86/boot/bzImage` once you've
+compiled your kernel.  To save time (since modules aren't supported yet),
+build your kernel with `make bzImage`.
+
+You can then do things like `cd /home/username` and you will have readonly
+access to all your files.
+
+Upcoming features
+=================
+
+In the near term, the high-priority features are:
+
+* Support for modular virtfs and 9p.
+* Some way to configure writable mounts.

cpiowriter.py

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+#!/usr/bin/python3
+# -*- mode: python -*-
+import sys
+
+class CpioWriter(object):
+    TYPE_DIR =     0o0040000
+    TYPE_REG =     0o0100000
+    TYPE_SYMLINK = 0o0120000
+    TYPE_MASK =    0o0170000
+
+    def __init__(self, f):
+        self.__f = f
+        self.__totalsize = 0
+        self.__next_ino = 0
+
+    def __write(self, data):
+        self.__f.write(data)
+        self.__totalsize += len(data)
+
+    def write_object(self, name, body, mode, ino=None, nlink=None,
+                     uid=0, gid=0, mtime=0, devmajor=0, devminor=0,
+                     rdevmajor=0, rdevminor=0):
+        if nlink is None:
+            nlink = (2 if (mode & CpioWriter.TYPE_MASK) == CpioWriter.TYPE_DIR
+                     else 1)
+
+        if b'\0' in name:
+            raise ValueError('Filename cannot contain a NUL')
+
+        namesize = len(name) + 1
+
+        if isinstance(body, bytes):
+            filesize = len(body)
+        else:
+            filesize = body.seek(0, 2)
+            body.seek(0)
+
+        if ino is None:
+            ino = self.__next_ino
+            self.__next_ino += 1
+
+        fields = [ino, mode, uid, gid, nlink, mtime, filesize,
+                  devmajor, devminor, rdevmajor, rdevminor, namesize, 0]
+        hdr = ('070701' + ''.join('%08X' % f for f in fields)).encode('ascii')
+
+        self.__write(hdr)
+        self.__write(name)
+        self.__write(b'\0')
+        self.__write(((2-namesize) % 4) * b'\0')
+
+        if isinstance(body, bytes):
+            self.__write(body)
+        else:
+            while True:
+                buf = body.read(65536)
+                if buf == b'':
+                    break
+                self.__write(buf)
+
+        self.__write(((-filesize) % 4) * b'\0')
+
+    def write_trailer(self):
+        self.write_object(name=b'TRAILER!!!', body=b'', mode=0, ino=0, nlink=1)
+        self.__write(((-self.__totalsize) % 512) * b'\0')
+
+    def mkdir(self, name, mode):
+        self.write_object(name=name, mode=CpioWriter.TYPE_DIR | mode, body=b'')
+
+    def symlink(self, src, dst):
+        self.write_object(name=dst, mode=CpioWriter.TYPE_SYMLINK | 0o777,
+                          body=src)
+
+    def write_file(self, name, body, mode):
+        self.write_object(name=name, body=body, mode=CpioWriter.TYPE_REG | mode)

virtme-init

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+#!/bin/sh
+# virtme-init: virtme's basic init (PID 1) process
+# Copyright © 2013 Andy Lutomirski
+# Licensed under the GPLv2, which is available in the virtme distribution
+# as a file called LICENSE with SHA-256 hash:
+# 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643
+
+export PATH=/bin:/sbin:/usr/bin:/usr/sbin
+export TERM=linux
+
+# Set up a minimally functional system
+mount -t proc -o nosuid,noexec,nodev /proc/
+mount -t sysfs -o nosuid,noexec,nodev /sys/
+
+mount -t tmpfs tmpfs /tmp/
+mount -t tmpfs tmpfs /run/
+
+# Find udevd
+if [[ -x /usr/lib/systemd/systemd-udevd ]]; then
+    udevd=/usr/lib/systemd/systemd-udevd
+else
+    udevd=`which udevd`
+fi
+
+# Ideally we'll use devtmpfs
+if mount -t devtmpfs -o mode=0755,nosuid,noexec none /dev &>/dev/null; then
+    "$udevd" --daemon --resolve-names=never
+else
+    # The running kernel doesn't have devtmpfs.  Use regular tmpfs.
+    mount -t tmpfs -o mode=0755,nosuid,noexec none /dev
+
+    # Make some basic devices first, let udev handle the rest
+    mknod -m 0666 /dev/null c 1 3
+    mknod -m 0660 /dev/kmsg c 1 11
+    mknod -m 0600 /dev/console c 5 1
+
+    # Try to get udevd to coldplug everything
+    "$udevd" --daemon --resolve-names=never
+    udevadm trigger --action=add  >/dev/null 2>&1
+    udevadm settle
+fi
+
+mkdir -p -m 0755 /dev/shm /dev/pts
+mount -t devpts -o gid=tty,mode=620,noexec,nosuid devpts /dev/pts
+mount -t tmpfs -o mode=1777,nosuid,nodev tmpfs /dev/shm
+
+# Bring up networking
+ip link set dev lo up
+
+# Create some VTs
+deallocvt
+openvt -c 2 -- /bin/bash
+openvt -c 3 -- /bin/bash
+openvt -c 4 -- /bin/bash
+
+# Figure out what the main console is
+consdev="`grep ' ... (.C' /proc/consoles  |cut -d' ' -f1`"
+if [[ -z "$consdev" ]]; then
+    echo "Can't deduce console device" >&2
+    exec bash --login  # At least try to be helpful
+fi
+if [[ "$consdev" == "tty0" ]]; then
+    consdev=tty1  # sigh
+fi
+if [[ ! -e "/dev/$consdev" ]]; then
+    echo "/dev/$consdev doesn't exist."
+    exec bash --login
+fi
+
+echo "virtme-init: console is $consdev"
+
+# Bring up a functioning shell on the console.  This is a bit magical:
+# We have no controlling terminal because we're attached to a fake
+# console device (probably something like /dev/console), which can't
+# be a controlling terminal.  We are also not a member of a session.
+# Init apparently can't setsid (whether that's a limitation of the
+# setsid binary or the system call, I don't know).
+while true; do
+    setsid bash 0<>"/dev/$consdev" 1>&0 2>&0
+    echo "Shell died.  Will respawn."
+    sleep 0.5
+done

virtme-mkinitramfs

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+#!/usr/bin/python3
+# -*- mode: python -*-
+# virtme-mkinitramfs: Generate an initramfs image for virtme
+# Copyright © 2013 Andy Lutomirski
+# Licensed under the GPLv2, which is available in the virtme distribution
+# as a file called LICENSE with SHA-256 hash:
+# 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643
+
+import argparse
+import shutil
+import cpiowriter
+import inspect
+import io
+import os.path
+import shlex
+
+def make_base_layout(cw):
+    for dir in (b'lib', b'bin', b'var', b'etc', b'newroot'):
+        cw.mkdir(dir, 0o755)
+
+    cw.symlink(b'bin', b'sbin')
+    cw.symlink(b'lib', b'lib64')
+
+def install_busybox(cw):
+    bbpath = shutil.which('busybox')
+    with open(bbpath, 'rb') as busybox:
+        cw.write_file(name=b'bin/busybox', body=busybox, mode=0o755)
+
+    for tool in ('sh', 'mount', 'umount', 'modprobe', 'switch_root'):
+        cw.symlink(b'busybox', ('bin/%s' % tool).encode('ascii'))
+
+def generate_init():
+    mypath = os.path.dirname(os.path.abspath(
+        inspect.getfile(inspect.currentframe())))
+
+    out = io.StringIO()
+    out.write('#!/bin/sh\n')
+    out.write('echo \'Mounting hostfs...\'\n')
+    out.write('/bin/mount -t 9p -o ro,version=9p2000.L,trans=virtio,access=any hostroot /newroot/\n')    
+
+    out.write('exec /bin/switch_root /newroot %s\n' % shlex.quote(os.path.join(mypath, 'virtme-init')))
+    return out.getvalue().encode('utf-8')
+
+def main():
+    import sys
+    cw = cpiowriter.CpioWriter(sys.stdout.buffer)
+    make_base_layout(cw)
+    install_busybox(cw)
+    cw.write_file(b'init', body=generate_init(), mode=0o755)
+    cw.write_trailer()
+    return 0
+
+if __name__ == '__main__':
+    exit(main())

virtme-runkernel

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+#!/bin/bash
+# virtme-runkernel: A silly script to run a kernel image
+# Copyright © 2013 Andy Lutomirski
+# Licensed under the GPLv2, which is available in the virtme distribution
+# as a file called LICENSE with SHA-256 hash:
+# 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643
+
+# This is a giant hack.  I'll make it better at some point.
+
+tmpfile="`mktemp --tmpdir initramfs.XXXXXXXXXX`"
+exec 3<>"$tmpfile"
+rm "$tmpfile"
+
+v_mki="$(dirname $0)/virtme-mkinitramfs"
+"$v_mki" >&3
+
+exec qemu-kvm -virtfs local,id=rootfs,path=/,security_model=passthrough,mount_tag=hostroot,readonly -initrd /proc/self/fd/3 -kernel "$@"