+ va_start (args, fs);
+ err = vasprintf (&msg, fs, args);
+ va_end (args);
+
+ if (err < 0) return;
+
+ gettimeofday (&tv, NULL);
+
+ fprintf (stderr, "[%05" PRIi64 "ms] %s\n",
+ timeval_diff (&g->launch_t, &tv), msg);
+
+ free (msg);
+}
+
+static int read_all (guestfs_h *g, FILE *fp, char **ret);
+
+/* Test qemu binary (or wrapper) runs, and do 'qemu -help' and
+ * 'qemu -version' so we know what options this qemu supports and
+ * the version.
+ */
+static int
+test_qemu (guestfs_h *g)
+{
+ char cmd[1024];
+ FILE *fp;
+
+ snprintf (cmd, sizeof cmd, "LC_ALL=C '%s' -nographic -help", g->qemu);
+
+ fp = popen (cmd, "r");
+ /* qemu -help should always work (qemu -version OTOH wasn't
+ * supported by qemu 0.9). If this command doesn't work then it
+ * probably indicates that the qemu binary is missing.
+ */
+ if (!fp) {
+ /* XXX This error is never printed, even if the qemu binary
+ * doesn't exist. Why?
+ */
+ error:
+ perrorf (g, _("%s: command failed: If qemu is located on a non-standard path, try setting the LIBGUESTFS_QEMU environment variable."), cmd);
+ return -1;
+ }
+
+ if (read_all (g, fp, &g->qemu_help) == -1)
+ goto error;
+
+ if (pclose (fp) == -1)
+ goto error;
+
+ snprintf (cmd, sizeof cmd, "LC_ALL=C '%s' -nographic -version 2>/dev/null",
+ g->qemu);
+
+ fp = popen (cmd, "r");
+ if (fp) {
+ /* Intentionally ignore errors. */
+ read_all (g, fp, &g->qemu_version);
+ pclose (fp);
+ }
+
+ return 0;
+}
+
+static int
+read_all (guestfs_h *g, FILE *fp, char **ret)
+{
+ int r, n = 0;
+ char *p;
+
+ again:
+ if (feof (fp)) {
+ *ret = safe_realloc (g, *ret, n + 1);
+ (*ret)[n] = '\0';
+ return n;
+ }
+
+ *ret = safe_realloc (g, *ret, n + BUFSIZ);
+ p = &(*ret)[n];
+ r = fread (p, 1, BUFSIZ, fp);
+ if (ferror (fp)) {
+ perrorf (g, "read");
+ return -1;
+ }
+ n += r;
+ goto again;
+}
+
+/* Test if option is supported by qemu command line (just by grepping
+ * the help text).
+ *
+ * The first time this is used, it has to run the external qemu
+ * binary. If that fails, it returns -1.
+ *
+ * To just do the first-time run of the qemu binary, call this with
+ * option == NULL, in which case it will return -1 if there was an
+ * error doing that.
+ */
+static int
+qemu_supports (guestfs_h *g, const char *option)
+{
+ if (!g->qemu_help) {
+ if (test_qemu (g) == -1)
+ return -1;
+ }
+
+ if (option == NULL)
+ return 1;
+
+ return strstr (g->qemu_help, option) != NULL;
+}
+
+/* Check if a file can be opened. */
+static int
+is_openable (guestfs_h *g, const char *path, int flags)
+{
+ int fd = open (path, flags);
+ if (fd == -1) {
+ if (g->verbose)
+ perror (path);
+ return 0;
+ }
+ close (fd);
+ return 1;
+}
+
+/* Check the peer effective UID for a TCP socket. Ideally we'd like
+ * SO_PEERCRED for a loopback TCP socket. This isn't possible on
+ * Linux (but it is on Solaris!) so we read /proc/net/tcp instead.
+ */
+static int
+check_peer_euid (guestfs_h *g, int sock, uid_t *rtn)
+{
+#if CAN_CHECK_PEER_EUID
+ struct sockaddr_in peer;
+ socklen_t addrlen = sizeof peer;
+
+ if (getpeername (sock, (struct sockaddr *) &peer, &addrlen) == -1) {
+ perrorf (g, "getpeername");