lxcsu

   1 #!/usr/bin/python
   2
   3
   4 import setns
   5 import os
   6 import sys
   7
   8 from argparse import ArgumentParser
   9
  10 drop_capabilities='cap_sys_admin,cap_sys_boot,cap_sys_module'
  11
  12 debug = False
  13
  14 def getarch(f):
  15     output = os.popen('readelf -h %s 2>&1'%f).readlines()
  16     if debug: print "readelf output %s lines"%len(output)
  17     classlines = [x for x in output if ('Class' in x.split(':')[0])]
  18     line = classlines[0]
  19     c = line.split(':')[1]
  20     if ('ELF64' in c):
  21         return 'x86_64'
  22     elif ('ELF32' in c):
  23         return 'i686'
  24     else:
  25         raise Exception('Could not determine architecture')
  26
  27 def umount(fs_dir):
  28     output = os.popen('/bin/umount %s 2>&1'%fs_dir).read()
  29     return ('device is busy' not in fs_dir)
  30
  31 def main ():
  32     parser = ArgumentParser()
  33     parser.add_argument("-n", "--nonet",
  34                         action="store_true", dest="netns", default=False,
  35                         help="Don't enter network namespace")
  36     parser.add_argument("-m", "--nomnt",
  37                         action="store_true", dest="mntns", default=False,
  38                         help="Don't enter mount namespace")
  39     parser.add_argument("-p", "--nopid",
  40                         action="store_true", dest="pidns", default=False,
  41                         help="Don't enter pid namespace")
  42     parser.add_argument("-r", "--root",
  43                         action="store_true", dest="root", default=False,
  44                         help="Enter as root: be careful")
  45     parser.add_argument("-d","--debug",
  46                         action='store_true', dest='debug', default=False,
  47                         help="debug option")
  48     parser.add_argument ("slice_name")
  49     parser.add_argument ("command_to_run",nargs="*")
  50
  51     options = parser.parse_args()
  52     slice_name=options.slice_name
  53     global debug
  54     debug=options.debug
  55
  56     try:
  57         cmd = 'grep %s /proc/*/cgroup | grep freezer'%slice_name
  58         output = os.popen(cmd).readlines()
  59         if debug: print "output of grep freezer has %s lines"%len(output)
  60     except:
  61         print "Error finding slice %s"%slice_name
  62         exit(1)
  63
  64     slice_spec = None
  65
  66     # provide a default as this is not always properly computed
  67     arch = None
  68
  69     for e in output:
  70         try:
  71             l = e.rstrip()
  72             path = l.split(':')[0]
  73             comp = l.rsplit(':')[-1]
  74             slice_name_check = comp.rsplit('/')[-1]
  75             if debug: print "dealing with >%s<"%slice_name_check
  76
  77             if (slice_name_check == slice_name):
  78                 if debug: print "found %s"%slice_name
  79                 slice_path = path
  80                 pid = slice_path.split('/')[2]
  81                 cmdline = open('/proc/%s/cmdline'%pid).read().rstrip('\n\x00')
  82                 if (cmdline == '/sbin/init'):
  83                     slice_spec = slice_path
  84                     arch = getarch('/proc/%s/exe'%pid)
  85                     if debug: print "setting arch",arch
  86                     break
  87         except Exception,e:
  88             if debug:
  89                 import traceback
  90                 print "BEG lxcsu - ignoring exception"
  91                 traceback.print_exc()
  92                 print "END lxcsu - ignoring exception"
  93             pass
  94
  95     if (not slice_spec or not pid):
  96         print "Not started: %s"%slice_name
  97         exit(1)
  98
  99     if arch is None:
 100         arch = 'x86_64'
 101         if debug: print "WARNING: setting arch to default x86_64"
 102
 103     # Enter cgroups
 104     try:
 105         for subsystem in ['cpuset','memory','blkio']:
 106             open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))
 107
 108     except:
 109         print "Error assigning resources: %s"%slice_name
 110         exit(1)
 111
 112     try:
 113         open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))
 114     except:
 115         print "Error assigning cpuacct: %s" % slice_name
 116         exit(1)
 117
 118     # If the slice is frozen, then we'll get an EBUSY when trying to write to the task
 119     # list for the freezer cgroup. Since the user couldn't do anything anyway, it's best
 120     # in this case to error out the shell. (an alternative would be to un-freeze it,
 121     # add the task, and re-freeze it)
 122     try:
 123         f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')
 124         f.write(str(os.getpid()))
 125         # note: we need to call f.close() explicitly, or we'll get an exception in
 126         # the object destructor, which will not be caught
 127         f.close()
 128     except:
 129         print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name
 130         exit(1)
 131
 132     setns.chcontext('/proc/%s/ns/uts'%pid)
 133     setns.chcontext('/proc/%s/ns/ipc'%pid)
 134
 135     if (not options.netns):
 136         setns.chcontext('/proc/%s/ns/net'%pid)
 137
 138     if (not options.mntns):
 139         open('/proc/lxcsu','w').write(pid)
 140
 141     if (not options.pidns):
 142         open('/proc/pidsu','w').write(pid)
 143
 144     # cgroups is not yet LXC-safe, so we need to use the course grained access control
 145     # strategy of unmounting the filesystem
 146
 147     umount_result = True
 148     for subsystem in ['cpuset','cpu,cpuacct','memory','devices','freezer','net_cls','blkio','perf_event']:
 149         fs_path = '/sys/fs/cgroup/%s'%subsystem
 150         if (not umount(fs_path)):
 151             print "Error disabling cgroup access"
 152             exit(1)
 153
 154     if (not umount('/sys/fs/cgroup')):
 155         print "Error disabling cgroup access"
 156         exit(1)
 157
 158     pid = os.fork()
 159
 160     if (pid == 0):
 161         cap_arg = '--drop='+drop_capabilities
 162
 163         if (not options.root):
 164             exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--','--login']+options.command_to_run
 165         else:
 166             exec_args = [arch,'/usr/sbin/capsh','--','--login']+options.command_to_run
 167
 168         if debug:
 169             print "exec'ing"
 170             for arg in exec_args: print ">%s<"%arg
 171         os.environ['SHELL'] = '/bin/sh'
 172         os.execv('/usr/bin/setarch',exec_args)
 173     else:
 174         _,status = os.waitpid(pid,0)
 175         exit(os.WEXITSTATUS(status))
 176
 177 if __name__ == '__main__':
 178     main()