qemu: Add test qemu_nobody test

This test checks groups when guest is started as
nobody [v2] using qemu -runas option to exec the qemu.
Signed-off-by: NYunping Zheng <yunzheng@redhat.com>

qemu/tests/cfg/qemu_nobody.cfg

+- qemu_nobody:
+    start_vm = no
+    user_runas = nobody
+    type = qemu_nobody
+    requires_root = yes

qemu/tests/qemu_nobody.py

+import logging, re
+from autotest.client.shared import utils, error
+from virttest import env_process
+
+@error.context_aware
+def run_qemu_nobody(test, params, env):
+    """
+    Check smbios table :
+    1) Run the qemu command as nobody
+    2) check the process is same as the user's
+
+    @param test: QEMU test object.
+    @param params: Dictionary with the test parameters.
+    @param env: Dictionary with test environment.
+    """
+    def get_user_ugid(username):
+        """
+        return user uid and gid as a list
+        """
+        user_uid = utils.system_output("id -u %s" % username).split()
+        user_gid = utils.system_output("id -g %s" % username).split()
+        return(user_uid , user_gid)
+
+    def get_ugid_from_processid(pid):
+        """
+        return a list[uid,euid,suid,fsuid,gid,egid,sgid,fsgid] of pid
+        """
+        grep_ugid_cmd = "cat /proc/%s/status | grep -iE '^(U|G)id'"
+        o = utils.system_output(grep_ugid_cmd % pid.strip())
+        ugid = re.findall("(\d+)", o)
+        #real UID, effective UID, saved set UID, and file system UID
+        if ugid:
+            return ugid
+        else:
+            raise error.TestError("Could not find the correct UID for process %s"
+                                  % pid)
+
+    exec_username = params.get("user_runas", "nobody")
+
+    error.base_context("Run QEMU %s test:" % exec_username)
+    error.context("Get the user uid and gid,using 'id -u/g username'")
+    (exec_uid, exec_gid) = get_user_ugid(exec_username)
+
+    error.context("Run the qemu as user '%s'" % exec_username)
+    logging.info("The user %s :uid='%s', gid='%s'" %
+                                            (exec_username,exec_uid, exec_gid))
+
+    params["extra_params"] = " -runas %s" % exec_username
+    params["start_vm"] = "yes"
+    env_process.preprocess_vm(test, params, env, params.get("main_vm"))
+    vm = env.get_vm(params["main_vm"])
+
+    failures = []
+    for pid in utils.get_children_pids(vm.get_shell_pid()):
+        error.context("Get the process '%s' u/gid, using 'cat /proc/%s/status'"
+                       %(pid, pid), logging.info)
+        qemu_ugid = get_ugid_from_processid(pid)
+        logging.info("Process run as uid=%s,euid=%s,suid=%s,fsuid=%s"
+                     % tuple(qemu_ugid[0:4]))
+        logging.info("Process run as gid=%s,egid=%s,sgid=%s,fsgid=%s"
+                     % tuple(qemu_ugid[4:]))
+
+        error.context("Check if the user %s ugid is equal to the process %s"
+                       % (exec_username, pid))
+        #generate user uid, euid, suid, fsuid, gid, egid, sgid, fsgid
+        user_ugid_extend = exec_uid * 4 +  exec_gid * 4
+        if cmp(user_ugid_extend, qemu_ugid) != 0:
+            e_msg = ("Process %s error, expect ugid is %s, real is %s"
+                      % (pid, user_ugid_extend, qemu_ugid))
+            failures.append(e_msg)
+
+    if failures:
+        raise error.TestFail("FAIL: Test reported %s failures:\n%s" %
+                                 (len(failures), "\n".join(failures)))