qga: guest exec functionality

Guest-exec rewritten in platform-independent style with glib spawn.

Child process is spawn asynchronously and exit status can later
be picked up by guest-exec-status command.

stdin/stdout/stderr of the child now is redirected to /dev/null
Later we will add ability to specify stdin in guest-exec command
and to get collected stdout/stderr with guest-exec-status.

Signed-off-by: Yuri Pudgorodskiy <yur@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
* use g_new0 in place of g_malloc for GuestExec struct
* commit msg spelling fixes
* s/inp-data/input-data
* document capture-input mode as false by default
* use GetProcessId() for pids on w32 instead of casting HANDLE
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

qga/commands.c

@@ -70,3 +70,202 @@ struct GuestAgentInfo *qmp_guest_info(Error **errp)
     qmp_for_each_command(qmp_command_info, info);
     return info;
 }
+
+struct GuestExecInfo {
+    GPid pid;
+    int64_t pid_numeric;
+    gint status;
+    bool finished;
+    QTAILQ_ENTRY(GuestExecInfo) next;
+};
+typedef struct GuestExecInfo GuestExecInfo;
+
+static struct {
+    QTAILQ_HEAD(, GuestExecInfo) processes;
+} guest_exec_state = {
+    .processes = QTAILQ_HEAD_INITIALIZER(guest_exec_state.processes),
+};
+
+static int64_t gpid_to_int64(GPid pid)
+{
+#ifdef G_OS_WIN32
+    return GetProcessId(pid);
+#else
+    return (int64_t)pid;
+#endif
+}
+
+static GuestExecInfo *guest_exec_info_add(GPid pid)
+{
+    GuestExecInfo *gei;
+
+    gei = g_new0(GuestExecInfo, 1);
+    gei->pid = pid;
+    gei->pid_numeric = gpid_to_int64(pid);
+    QTAILQ_INSERT_TAIL(&guest_exec_state.processes, gei, next);
+
+    return gei;
+}
+
+static GuestExecInfo *guest_exec_info_find(int64_t pid_numeric)
+{
+    GuestExecInfo *gei;
+
+    QTAILQ_FOREACH(gei, &guest_exec_state.processes, next) {
+        if (gei->pid_numeric == pid_numeric) {
+            return gei;
+        }
+    }
+
+    return NULL;
+}
+
+GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error **err)
+{
+    GuestExecInfo *gei;
+    GuestExecStatus *ges;
+
+    slog("guest-exec-status called, pid: %u", (uint32_t)pid);
+
+    gei = guest_exec_info_find(pid);
+    if (gei == NULL) {
+        error_setg(err, QERR_INVALID_PARAMETER, "pid");
+        return NULL;
+    }
+
+    ges = g_new0(GuestExecStatus, 1);
+    ges->exited = gei->finished;
+
+    if (gei->finished) {
+        /* Glib has no portable way to parse exit status.
+         * On UNIX, we can get either exit code from normal termination
+         * or signal number.
+         * On Windows, it is either the same exit code or the exception
+         * value for an unhandled exception that caused the process
+         * to terminate.
+         * See MSDN for GetExitCodeProcess() and ntstatus.h for possible
+         * well-known codes, e.g. C0000005 ACCESS_DENIED - analog of SIGSEGV
+         * References:
+         *   https://msdn.microsoft.com/en-us/library/windows/desktop/ms683189(v=vs.85).aspx
+         *   https://msdn.microsoft.com/en-us/library/aa260331(v=vs.60).aspx
+         */
+#ifdef G_OS_WIN32
+        /* Additionally WIN32 does not provide any additional information
+         * on whetherthe child exited or terminated via signal.
+         * We use this simple range check to distingish application exit code
+         * (usually value less then 256) and unhandled exception code with
+         * ntstatus (always value greater then 0xC0000005). */
+        if ((uint32_t)gei->status < 0xC0000000U) {
+            ges->has_exitcode = true;
+            ges->exitcode = gei->status;
+        } else {
+            ges->has_signal = true;
+            ges->signal = gei->status;
+        }
+#else
+        if (WIFEXITED(gei->status)) {
+            ges->has_exitcode = true;
+            ges->exitcode = WEXITSTATUS(gei->status);
+        } else if (WIFSIGNALED(gei->status)) {
+            ges->has_signal = true;
+            ges->signal = WTERMSIG(gei->status);
+        }
+#endif
+        QTAILQ_REMOVE(&guest_exec_state.processes, gei, next);
+        g_free(gei);
+    }
+
+    return ges;
+}
+
+/* Get environment variables or arguments array for execve(). */
+static char **guest_exec_get_args(const strList *entry, bool log)
+{
+    const strList *it;
+    int count = 1, i = 0;  /* reserve for NULL terminator */
+    char **args;
+    char *str; /* for logging array of arguments */
+    size_t str_size = 1;
+
+    for (it = entry; it != NULL; it = it->next) {
+        count++;
+        str_size += 1 + strlen(it->value);
+    }
+
+    str = g_malloc(str_size);
+    *str = 0;
+    args = g_malloc(count * sizeof(char *));
+    for (it = entry; it != NULL; it = it->next) {
+        args[i++] = it->value;
+        pstrcat(str, str_size, it->value);
+        if (it->next) {
+            pstrcat(str, str_size, " ");
+        }
+    }
+    args[i] = NULL;
+
+    if (log) {
+        slog("guest-exec called: \"%s\"", str);
+    }
+    g_free(str);
+
+    return args;
+}
+
+static void guest_exec_child_watch(GPid pid, gint status, gpointer data)
+{
+    GuestExecInfo *gei = (GuestExecInfo *)data;
+
+    g_debug("guest_exec_child_watch called, pid: %d, status: %u",
+            (int32_t)gpid_to_int64(pid), (uint32_t)status);
+
+    gei->status = status;
+    gei->finished = true;
+
+    g_spawn_close_pid(pid);
+}
+
+GuestExec *qmp_guest_exec(const char *path,
+                       bool has_arg, strList *arg,
+                       bool has_env, strList *env,
+                       bool has_input_data, const char *input_data,
+                       bool has_capture_output, bool capture_output,
+                       Error **err)
+{
+    GPid pid;
+    GuestExec *ge = NULL;
+    GuestExecInfo *gei;
+    char **argv, **envp;
+    strList arglist;
+    gboolean ret;
+    GError *gerr = NULL;
+
+    arglist.value = (char *)path;
+    arglist.next = has_arg ? arg : NULL;
+
+    argv = guest_exec_get_args(&arglist, true);
+    envp = guest_exec_get_args(has_env ? env : NULL, false);
+
+    ret = g_spawn_async_with_pipes(NULL, argv, envp,
+            G_SPAWN_SEARCH_PATH |
+            G_SPAWN_DO_NOT_REAP_CHILD |
+            G_SPAWN_STDOUT_TO_DEV_NULL | G_SPAWN_STDERR_TO_DEV_NULL,
+            NULL, NULL, &pid, NULL, NULL, NULL, &gerr);
+    if (!ret) {
+        error_setg(err, QERR_QGA_COMMAND_FAILED, gerr->message);
+        g_error_free(gerr);
+        goto done;
+    }
+
+    ge = g_new0(GuestExec, 1);
+    ge->pid = gpid_to_int64(pid);
+
+    gei = guest_exec_info_add(pid);
+    g_child_watch_add(pid, guest_exec_child_watch, gei);
+
+done:
+    g_free(argv);
+    g_free(envp);
+
+    return ge;
+}

qga/qapi-schema.json

@@ -930,3 +930,65 @@
 ##
 { 'command': 'guest-get-memory-block-info',
   'returns': 'GuestMemoryBlockInfo' }
+
+# @GuestExecStatus:
+#
+# @exited: true if process has already terminated.
+# @exitcode: #optional process exit code if it was normally terminated.
+# @signal: #optional signal number (linux) or unhandled exception code
+#       (windows) if the process was abnormally terminated.
+# @out-data: #optional base64-encoded stdout of the process
+# @err-data: #optional base64-encoded stderr of the process
+#       Note: @out-data and @err-data are present only
+#       if 'capture-output' was specified for 'guest-exec'
+#
+# Since: 2.5
+##
+{ 'struct': 'GuestExecStatus',
+  'data': { 'exited': 'bool', '*exitcode': 'int', '*signal': 'int',
+            '*out-data': 'str', '*err-data': 'str' }}
+##
+# @guest-exec-status
+#
+# Check status of process associated with PID retrieved via guest-exec.
+# Reap the process and associated metadata if it has exited.
+#
+# @pid: pid returned from guest-exec
+#
+# Returns: GuestExecStatus on success.
+#
+# Since 2.5
+##
+{ 'command': 'guest-exec-status',
+  'data':    { 'pid': 'int' },
+  'returns': 'GuestExecStatus' }
+
+##
+# @GuestExec:
+# @pid: pid of child process in guest OS
+#
+#Since: 2.5
+##
+{ 'struct': 'GuestExec',
+  'data': { 'pid': 'int'} }
+
+##
+# @guest-exec:
+#
+# Execute a command in the guest
+#
+# @path: path or executable name to execute
+# @arg: #optional argument list to pass to executable
+# @env: #optional environment variables to pass to executable
+# @input-data: #optional data to be passed to process stdin (base64 encoded)
+# @capture-output: #optional bool flag to enable capture of
+#                  stdout/stderr of running process. defaults to false.
+#
+# Returns: PID on success.
+#
+# Since: 2.5
+##
+{ 'command': 'guest-exec',
+  'data':    { 'path': 'str', '*arg': ['str'], '*env': ['str'],
+               '*input-data': 'str', '*capture-output': 'bool' },
+  'returns': 'GuestExec' }