runqemu: fix handling of SIGTERM and the problem of line wrapping

The current handling of SIGTERM is incorrect as the process pid returned
by Popen call with shell setting to True is actualy the shell instead of
the qemu process. So use shlex to split cmd so that we can avoid using
shell=True. This ensures the child process is the actual qemu process.

Also, as we install a SIGTERM handler, we need handle the situation of
qemu terminated by SIGTERM, otherwise we will get ERROR message in such
case.

Besides, we have a problem that after running qemu, the terminal's behavior
is incorrect regarding long lines or long commands. Long commands or long
outputs should appear in multiple lines, but they appear in the same line,
overriding previous output. Use `tput smam' to fix this problem.

(From OE-Core rev: e8acef383767cfd1ef0c3d3c45d9d6eb1c83b3e7)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/runqemu

@@ -1202,6 +1202,7 @@ class BaseConfig(object):
                 self.qemu_opt += " -serial mon:vc -serial null"
 
     def start_qemu(self):
+        import shlex
         if self.kernel:
             kernel_opts = "-kernel %s -append '%s %s %s %s'" % (self.kernel, self.kernel_cmdline,
                                                                 self.kernel_cmdline_script, self.get('QB_KERNEL_CMDLINE_APPEND'),
@@ -1211,11 +1212,16 @@ class BaseConfig(object):
         else:
             kernel_opts = ""
         cmd = "%s %s" % (self.qemu_opt, kernel_opts)
+        cmds = shlex.split(cmd)
         logger.info('Running %s\n' % cmd)
-        process = subprocess.Popen(cmd, shell=True, stderr=subprocess.PIPE)
+        process = subprocess.Popen(cmds, stderr=subprocess.PIPE)
         self.qemupid = process.pid
-        if process.wait():
-            logger.error("Failed to run qemu: %s", process.stderr.read().decode())
+        retcode = process.wait()
+        if retcode:
+            if retcode == -signal.SIGTERM:
+                logger.info("Qemu terminated by SIGTERM")
+            else:
+                logger.error("Failed to run qemu: %s", process.stderr.read().decode())
 
     def cleanup(self):
         if self.cleaned:
@@ -1310,6 +1316,7 @@ def main():
             logger.info("SIGTERM received")
             os.kill(config.qemupid, signal.SIGTERM)
             config.cleanup()
+            subprocess.run(["tput", "smam"])
         signal.signal(signal.SIGTERM, sigterm_handler)
 
         config.check_args()
@@ -1331,6 +1338,7 @@ def main():
         return 1
     finally:
         config.cleanup()
+        subprocess.run(["tput", "smam"])
 
 if __name__ == "__main__":
     sys.exit(main())