From bcc63f775e265df69963a4ad7805b8678ace68f0 Mon Sep 17 00:00:00 2001
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From: Alistair Francis <alistair.francis@xilinx.com>
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Date: Thu, 21 Dec 2017 11:35:16 -0800
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Subject: [PATCH] chardev: connect socket to a spawned command
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The command is started in a shell (sh -c) with stdin connect to QEMU
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via a Unix domain stream socket. QEMU then exchanges data via its own
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end of the socket, just like it normally does.
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"-chardev socket" supports some ways of connecting via protocols like
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telnet, but that is only a subset of the functionality supported by
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tools socat. To use socat instead, for example to connect via a socks
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proxy, use:
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-chardev 'socket,id=socat,cmd=exec socat FD:0 SOCKS4A:socks-proxy.localdomain:example.com:9999,,socksuser=nobody' \
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-device usb-serial,chardev=socat
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Beware that commas in the command must be escaped as double commas.
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Or interactively in the console:
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(qemu) chardev-add socket,id=cat,cmd=cat
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(qemu) device_add usb-serial,chardev=cat
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^ac
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# cat >/dev/ttyUSB0
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hello
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hello
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Another usage is starting swtpm from inside QEMU. swtpm will
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automatically shut down once it looses the connection to the parent
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QEMU, so there is no risk of lingering processes:
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-chardev 'socket,id=chrtpm0,cmd=exec swtpm socket --terminate --ctrl type=unixio,,clientfd=0 --tpmstate dir=... --log file=swtpm.log' \
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-tpmdev emulator,id=tpm0,chardev=chrtpm0 \
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-device tpm-tis,tpmdev=tpm0
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The patch was discussed upstream, but QEMU developers believe that the
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code calling QEMU should be responsible for managing additional
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processes. In OE-core, that would imply enhancing runqemu and
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oeqa. This patch is a simpler solution.
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Because it is not going upstream, the patch was written so that it is
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as simple as possible.
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Upstream-Status: Inappropriate [embedded specific]
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Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
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---
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chardev/char-socket.c | 101 ++++++++++++++++++++++++++++++++++++++++++
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chardev/char.c | 3 ++
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qapi/char.json | 5 +++
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3 files changed, 109 insertions(+)
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Index: qemu-6.0.0/chardev/char-socket.c
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===================================================================
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--- qemu-6.0.0.orig/chardev/char-socket.c
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+++ qemu-6.0.0/chardev/char-socket.c
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@@ -1362,6 +1362,67 @@ static bool qmp_chardev_validate_socket(
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return true;
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}
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+#ifndef _WIN32
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+static void chardev_open_socket_cmd(Chardev *chr,
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+ const char *cmd,
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+ Error **errp)
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+{
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+ int fds[2] = { -1, -1 };
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+ QIOChannelSocket *sioc = NULL;
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+ pid_t pid = -1;
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+ const char *argv[] = { "/bin/sh", "-c", cmd, NULL };
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+
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+ /*
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+ * We need a Unix domain socket for commands like swtpm and a single
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+ * connection, therefore we cannot use qio_channel_command_new_spawn()
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+ * without patching it first. Duplicating the functionality is easier.
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+ */
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+ if (socketpair(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, fds)) {
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+ error_setg_errno(errp, errno, "Error creating socketpair(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC)");
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+ goto error;
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+ }
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+
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+ pid = qemu_fork(errp);
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+ if (pid < 0) {
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+ goto error;
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+ }
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+
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+ if (!pid) {
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+ /* child */
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+ dup2(fds[1], STDIN_FILENO);
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+ execv(argv[0], (char * const *)argv);
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+ _exit(1);
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+ }
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+
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+ /*
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+ * Hand over our end of the socket pair to the qio channel.
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+ *
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+ * We don't reap the child because it is expected to keep
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+ * running. We also don't support the "reconnect" option for the
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+ * same reason.
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+ */
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+ sioc = qio_channel_socket_new_fd(fds[0], errp);
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+ if (!sioc) {
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+ goto error;
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+ }
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+ fds[0] = -1;
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+
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+ g_free(chr->filename);
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+ chr->filename = g_strdup_printf("cmd:%s", cmd);
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+ tcp_chr_new_client(chr, sioc);
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+
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+ error:
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+ if (fds[0] >= 0) {
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+ close(fds[0]);
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+ }
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+ if (fds[1] >= 0) {
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+ close(fds[1]);
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+ }
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+ if (sioc) {
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+ object_unref(OBJECT(sioc));
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+ }
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+}
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+#endif
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static void qmp_chardev_open_socket(Chardev *chr,
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ChardevBackend *backend,
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@@ -1370,6 +1431,9 @@ static void qmp_chardev_open_socket(Char
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{
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SocketChardev *s = SOCKET_CHARDEV(chr);
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ChardevSocket *sock = backend->u.socket.data;
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+#ifndef _WIN32
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+ const char *cmd = sock->cmd;
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+#endif
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bool do_nodelay = sock->has_nodelay ? sock->nodelay : false;
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bool is_listen = sock->has_server ? sock->server : true;
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bool is_telnet = sock->has_telnet ? sock->telnet : false;
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@@ -1446,6 +1510,14 @@ static void qmp_chardev_open_socket(Char
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update_disconnected_filename(s);
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+#ifndef _WIN32
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+ if (cmd) {
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+ chardev_open_socket_cmd(chr, cmd, errp);
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+
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+ /* everything ready (or failed permanently) before we return */
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+ *be_opened = true;
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+ } else
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+#endif
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if (s->is_listen) {
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if (qmp_chardev_open_socket_server(chr, is_telnet || is_tn3270,
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is_waitconnect, errp) < 0) {
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@@ -1465,6 +1537,9 @@ static void qemu_chr_parse_socket(QemuOp
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const char *host = qemu_opt_get(opts, "host");
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const char *port = qemu_opt_get(opts, "port");
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const char *fd = qemu_opt_get(opts, "fd");
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+#ifndef _WIN32
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+ const char *cmd = qemu_opt_get(opts, "cmd");
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+#endif
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#ifdef CONFIG_LINUX
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bool tight = qemu_opt_get_bool(opts, "tight", true);
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bool abstract = qemu_opt_get_bool(opts, "abstract", false);
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@@ -1472,6 +1547,20 @@ static void qemu_chr_parse_socket(QemuOp
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SocketAddressLegacy *addr;
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ChardevSocket *sock;
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+#ifndef _WIN32
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+ if (cmd) {
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+ /*
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+ * Here we have to ensure that no options are set which are incompatible with
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+ * spawning a command, otherwise unmodified code that doesn't know about
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+ * command spawning (like socket_reconnect_timeout()) might get called.
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+ */
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+ if (path || sock->server || sock->has_telnet || sock->has_tn3270 || sock->reconnect || host || port || sock->tls_creds) {
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+ error_setg(errp, "chardev: socket: cmd does not support any additional options");
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+ return;
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+ }
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+ } else
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+#endif
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+
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if ((!!path + !!fd + !!host) != 1) {
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error_setg(errp,
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"Exactly one of 'path', 'fd' or 'host' required");
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@@ -1522,13 +1611,24 @@ static void qemu_chr_parse_socket(QemuOp
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sock->tls_creds = g_strdup(qemu_opt_get(opts, "tls-creds"));
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sock->has_tls_authz = qemu_opt_get(opts, "tls-authz");
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sock->tls_authz = g_strdup(qemu_opt_get(opts, "tls-authz"));
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+#ifndef _WIN32
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+ sock->cmd = g_strdup(cmd);
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+#endif
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addr = g_new0(SocketAddressLegacy, 1);
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+#ifndef _WIN32
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+ if (path || cmd) {
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+#else
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if (path) {
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+#endif
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UnixSocketAddress *q_unix;
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addr->type = SOCKET_ADDRESS_LEGACY_KIND_UNIX;
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q_unix = addr->u.q_unix.data = g_new0(UnixSocketAddress, 1);
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+#ifndef _WIN32
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+ q_unix->path = cmd ? g_strdup_printf("cmd:%s", cmd) : g_strdup(path);
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+#else
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q_unix->path = g_strdup(path);
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+#endif
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#ifdef CONFIG_LINUX
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q_unix->has_tight = true;
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q_unix->tight = tight;
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Index: qemu-6.0.0/chardev/char.c
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===================================================================
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--- qemu-6.0.0.orig/chardev/char.c
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+++ qemu-6.0.0/chardev/char.c
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@@ -840,6 +840,9 @@ QemuOptsList qemu_chardev_opts = {
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.name = "path",
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.type = QEMU_OPT_STRING,
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},{
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+ .name = "cmd",
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+ .type = QEMU_OPT_STRING,
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+ },{
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.name = "host",
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.type = QEMU_OPT_STRING,
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},{
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Index: qemu-6.0.0/qapi/char.json
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===================================================================
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--- qemu-6.0.0.orig/qapi/char.json
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+++ qemu-6.0.0/qapi/char.json
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@@ -250,6 +250,10 @@
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#
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# @addr: socket address to listen on (server=true)
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# or connect to (server=false)
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+# @cmd: command to run via "sh -c" with stdin as one end of
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+# a AF_UNIX SOCK_DSTREAM socket pair. The other end
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+# is used by the chardev. Either an addr or a cmd can
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+# be specified, but not both.
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# @tls-creds: the ID of the TLS credentials object (since 2.6)
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# @tls-authz: the ID of the QAuthZ authorization object against which
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# the client's x509 distinguished name will be validated. This
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@@ -276,6 +280,7 @@
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##
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{ 'struct': 'ChardevSocket',
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'data': { 'addr': 'SocketAddressLegacy',
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+ '*cmd': 'str',
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'*tls-creds': 'str',
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'*tls-authz' : 'str',
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'*server': 'bool',
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