test/py/u_boot_spawn.py

   1 # Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
   2 #
   3 # SPDX-License-Identifier: GPL-2.0
   4
   5 # Logic to spawn a sub-process and interact with its stdio.
   6
   7 import os
   8 import re
   9 import pty
  10 import signal
  11 import select
  12 import time
  13
  14 class Timeout(Exception):
  15     """An exception sub-class that indicates that a timeout occurred."""
  16     pass
  17
  18 class Spawn(object):
  19     """Represents the stdio of a freshly created sub-process. Commands may be
  20     sent to the process, and responses waited for.
  21     """
  22
  23     def __init__(self, args, cwd=None):
  24         """Spawn (fork/exec) the sub-process.
  25
  26         Args:
  27             args: array of processs arguments. argv[0] is the command to
  28               execute.
  29             cwd: the directory to run the process in, or None for no change.
  30
  31         Returns:
  32             Nothing.
  33         """
  34
  35         self.waited = False
  36         self.buf = ''
  37         self.logfile_read = None
  38         self.before = ''
  39         self.after = ''
  40         self.timeout = None
  41         # http://stackoverflow.com/questions/7857352/python-regex-to-match-vt100-escape-sequences
  42         # Note that re.I doesn't seem to work with this regex (or perhaps the
  43         # version of Python in Ubuntu 14.04), hence the inclusion of a-z inside
  44         # [] instead.
  45         self.re_vt100 = re.compile('(\x1b\[|\x9b)[^@-_a-z]*[@-_a-z]|\x1b[@-_a-z]')
  46
  47         (self.pid, self.fd) = pty.fork()
  48         if self.pid == 0:
  49             try:
  50                 # For some reason, SIGHUP is set to SIG_IGN at this point when
  51                 # run under "go" (www.go.cd). Perhaps this happens under any
  52                 # background (non-interactive) system?
  53                 signal.signal(signal.SIGHUP, signal.SIG_DFL)
  54                 if cwd:
  55                     os.chdir(cwd)
  56                 os.execvp(args[0], args)
  57             except:
  58                 print 'CHILD EXECEPTION:'
  59                 import traceback
  60                 traceback.print_exc()
  61             finally:
  62                 os._exit(255)
  63
  64         try:
  65             self.poll = select.poll()
  66             self.poll.register(self.fd, select.POLLIN | select.POLLPRI | select.POLLERR | select.POLLHUP | select.POLLNVAL)
  67         except:
  68             self.close()
  69             raise
  70
  71     def kill(self, sig):
  72         """Send unix signal "sig" to the child process.
  73
  74         Args:
  75             sig: The signal number to send.
  76
  77         Returns:
  78             Nothing.
  79         """
  80
  81         os.kill(self.pid, sig)
  82
  83     def isalive(self):
  84         """Determine whether the child process is still running.
  85
  86         Args:
  87             None.
  88
  89         Returns:
  90             Boolean indicating whether process is alive.
  91         """
  92
  93         if self.waited:
  94             return False
  95
  96         w = os.waitpid(self.pid, os.WNOHANG)
  97         if w[0] == 0:
  98             return True
  99
 100         self.waited = True
 101         return False
 102
 103     def send(self, data):
 104         """Send data to the sub-process's stdin.
 105
 106         Args:
 107             data: The data to send to the process.
 108
 109         Returns:
 110             Nothing.
 111         """
 112
 113         os.write(self.fd, data)
 114
 115     def expect(self, patterns):
 116         """Wait for the sub-process to emit specific data.
 117
 118         This function waits for the process to emit one pattern from the
 119         supplied list of patterns, or for a timeout to occur.
 120
 121         Args:
 122             patterns: A list of strings or regex objects that we expect to
 123                 see in the sub-process' stdout.
 124
 125         Returns:
 126             The index within the patterns array of the pattern the process
 127             emitted.
 128
 129         Notable exceptions:
 130             Timeout, if the process did not emit any of the patterns within
 131             the expected time.
 132         """
 133
 134         for pi in xrange(len(patterns)):
 135             if type(patterns[pi]) == type(''):
 136                 patterns[pi] = re.compile(patterns[pi])
 137
 138         tstart_s = time.time()
 139         try:
 140             while True:
 141                 earliest_m = None
 142                 earliest_pi = None
 143                 for pi in xrange(len(patterns)):
 144                     pattern = patterns[pi]
 145                     m = pattern.search(self.buf)
 146                     if not m:
 147                         continue
 148                     if earliest_m and m.start() >= earliest_m.start():
 149                         continue
 150                     earliest_m = m
 151                     earliest_pi = pi
 152                 if earliest_m:
 153                     pos = earliest_m.start()
 154                     posafter = earliest_m.end()
 155                     self.before = self.buf[:pos]
 156                     self.after = self.buf[pos:posafter]
 157                     self.buf = self.buf[posafter:]
 158                     return earliest_pi
 159                 tnow_s = time.time()
 160                 if self.timeout:
 161                     tdelta_ms = (tnow_s - tstart_s) * 1000
 162                     poll_maxwait = self.timeout - tdelta_ms
 163                     if tdelta_ms > self.timeout:
 164                         raise Timeout()
 165                 else:
 166                     poll_maxwait = None
 167                 events = self.poll.poll(poll_maxwait)
 168                 if not events:
 169                     raise Timeout()
 170                 c = os.read(self.fd, 1024)
 171                 if not c:
 172                     raise EOFError()
 173                 if self.logfile_read:
 174                     self.logfile_read.write(c)
 175                 self.buf += c
 176                 # count=0 is supposed to be the default, which indicates
 177                 # unlimited substitutions, but in practice the version of
 178                 # Python in Ubuntu 14.04 appears to default to count=2!
 179                 self.buf = self.re_vt100.sub('', self.buf, count=1000000)
 180         finally:
 181             if self.logfile_read:
 182                 self.logfile_read.flush()
 183
 184     def close(self):
 185         """Close the stdio connection to the sub-process.
 186
 187         This also waits a reasonable time for the sub-process to stop running.
 188
 189         Args:
 190             None.
 191
 192         Returns:
 193             Nothing.
 194         """
 195
 196         os.close(self.fd)
 197         for i in xrange(100):
 198             if not self.isalive():
 199                 break
 200             time.sleep(0.1)