u-boot/test/py/u_boot_spawn.py

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# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
#
# SPDX-License-Identifier: GPL-2.0
# Logic to spawn a sub-process and interact with its stdio.
import os
import re
import pty
import signal
import select
import time
class Timeout(Exception):
"""An exception sub-class that indicates that a timeout occurred."""
pass
class Spawn(object):
"""Represents the stdio of a freshly created sub-process. Commands may be
sent to the process, and responses waited for.
Members:
output: accumulated output from expect()
"""
def __init__(self, args, cwd=None):
"""Spawn (fork/exec) the sub-process.
Args:
args: array of processs arguments. argv[0] is the command to
execute.
cwd: the directory to run the process in, or None for no change.
Returns:
Nothing.
"""
self.waited = False
self.buf = ''
self.output = ''
self.logfile_read = None
self.before = ''
self.after = ''
self.timeout = None
# http://stackoverflow.com/questions/7857352/python-regex-to-match-vt100-escape-sequences
# Note that re.I doesn't seem to work with this regex (or perhaps the
# version of Python in Ubuntu 14.04), hence the inclusion of a-z inside
# [] instead.
self.re_vt100 = re.compile('(\x1b\[|\x9b)[^@-_a-z]*[@-_a-z]|\x1b[@-_a-z]')
(self.pid, self.fd) = pty.fork()
if self.pid == 0:
try:
# For some reason, SIGHUP is set to SIG_IGN at this point when
# run under "go" (www.go.cd). Perhaps this happens under any
# background (non-interactive) system?
signal.signal(signal.SIGHUP, signal.SIG_DFL)
if cwd:
os.chdir(cwd)
os.execvp(args[0], args)
except:
print 'CHILD EXECEPTION:'
import traceback
traceback.print_exc()
finally:
os._exit(255)
try:
self.poll = select.poll()
self.poll.register(self.fd, select.POLLIN | select.POLLPRI | select.POLLERR | select.POLLHUP | select.POLLNVAL)
except:
self.close()
raise
def kill(self, sig):
"""Send unix signal "sig" to the child process.
Args:
sig: The signal number to send.
Returns:
Nothing.
"""
os.kill(self.pid, sig)
def isalive(self):
"""Determine whether the child process is still running.
Args:
None.
Returns:
Boolean indicating whether process is alive.
"""
if self.waited:
return False
w = os.waitpid(self.pid, os.WNOHANG)
if w[0] == 0:
return True
self.waited = True
return False
def send(self, data):
"""Send data to the sub-process's stdin.
Args:
data: The data to send to the process.
Returns:
Nothing.
"""
os.write(self.fd, data)
def expect(self, patterns):
"""Wait for the sub-process to emit specific data.
This function waits for the process to emit one pattern from the
supplied list of patterns, or for a timeout to occur.
Args:
patterns: A list of strings or regex objects that we expect to
see in the sub-process' stdout.
Returns:
The index within the patterns array of the pattern the process
emitted.
Notable exceptions:
Timeout, if the process did not emit any of the patterns within
the expected time.
"""
for pi in xrange(len(patterns)):
if type(patterns[pi]) == type(''):
patterns[pi] = re.compile(patterns[pi])
tstart_s = time.time()
try:
while True:
earliest_m = None
earliest_pi = None
for pi in xrange(len(patterns)):
pattern = patterns[pi]
m = pattern.search(self.buf)
if not m:
continue
if earliest_m and m.start() >= earliest_m.start():
continue
earliest_m = m
earliest_pi = pi
if earliest_m:
pos = earliest_m.start()
posafter = earliest_m.end()
self.before = self.buf[:pos]
self.after = self.buf[pos:posafter]
self.output += self.buf[:posafter]
self.buf = self.buf[posafter:]
return earliest_pi
tnow_s = time.time()
test/py: support running sandbox under gdbserver Implement command--line option --gdbserver COMM, which does two things: a) Run the sandbox process under gdbserver, using COMM as gdbserver's communication channel. b) Disables all timeouts, so that if U-Boot is halted under the debugger, tests don't fail. If the user gives up in the middle of a debugging session, they can simply CTRL-C the test script to abort it. This allows easy debugging of test failures without having to manually re-create the failure conditions. Usage is: Window 1: ./test/py/test.py --bd sandbox --gdbserver localhost:1234 Window 2: gdb ./build-sandbox/u-boot -ex 'target remote localhost:1234' When using this option, it likely makes sense to use pytest's -k option to limit the set of tests that are executed. Simply running U-Boot directly under gdb (rather than gdbserver) was also considered. However, this was rejected because: a) gdb's output would then be processed by the test script, and likely confuse it causing false failures. b) pytest by default hides stdout from tests, which would prevent the user from interacting with gdb. While gdb can be told to redirect the debugee's stdio to a separate PTY, this would appear to leave gdb's stdio directed at the test scripts and the debugee's stdio directed elsewhere, which is the opposite of the desired effect. Perhaps some complicated PTY muxing and process hierarchy could invert this. However, the current scheme is simple to implement and use, so it doesn't seem worth complicating matters. c) Using gdbserver allows arbitrary debuggers to be used, even those with a GUI. If the test scripts invoked the debugger themselves, they'd have to know how to execute arbitary applications. While the user could hide this all in a wrapper script, this feels like extra complication. An interesting future idea might be a --gdb-screen option, which could spawn both U-Boot and gdb separately, and spawn the screen into a newly created window under screen. Similar options could be envisaged for creating a new xterm/... too. --gdbserver currently only supports sandbox, and not real hardware. That's primarily because the test hooks are responsible for all aspects of hardware control, so there's nothing for the test scripts themselves can do to enable gdbserver on real hardware. We might consider introducing a separate --disable-timeouts option to support use of debuggers on real hardware, and having --gdbserver imply that option. Signed-off-by: Stephen Warren <swarren@nvidia.com>
2016-02-04 23:11:50 +00:00
if self.timeout:
tdelta_ms = (tnow_s - tstart_s) * 1000
poll_maxwait = self.timeout - tdelta_ms
if tdelta_ms > self.timeout:
raise Timeout()
else:
poll_maxwait = None
events = self.poll.poll(poll_maxwait)
if not events:
raise Timeout()
c = os.read(self.fd, 1024)
if not c:
raise EOFError()
if self.logfile_read:
self.logfile_read.write(c)
self.buf += c
# count=0 is supposed to be the default, which indicates
# unlimited substitutions, but in practice the version of
# Python in Ubuntu 14.04 appears to default to count=2!
self.buf = self.re_vt100.sub('', self.buf, count=1000000)
finally:
if self.logfile_read:
self.logfile_read.flush()
def close(self):
"""Close the stdio connection to the sub-process.
This also waits a reasonable time for the sub-process to stop running.
Args:
None.
Returns:
Nothing.
"""
os.close(self.fd)
for i in xrange(100):
if not self.isalive():
break
time.sleep(0.1)
def get_expect_output(self):
"""Return the output read by expect()
Returns:
The output processed by expect(), as a string.
"""
return self.output