[Qemu-devel] [PATCH V2] Add "tee" option to qemu char device

[Chunyan Liu]

Add "tee" backend to char device. It could be used as follows:
    -serial tee:filepath,pty
    -chardev tee,tee_fpath=path,tee_backend=pty,,path=path,,[mux=on|off]
With "tee" option, "pty" output would be duplicated to filepath.
Related thread:
http://lists.nongnu.org/archive/html/qemu-devel/2011-07/msg00105.html

V2 changes:
    -implement "tee" as a new backend. V1 implemented "tee" as a option.
    -add documentation in qemu-options.hx.

Please review. Thanks.

---
 qemu-char.c     |  168 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 qemu-config.c   |    6 ++
 qemu-options.hx |   25 ++++++++-
 3 files changed, 197 insertions(+), 2 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index fb13b28..99e49a9 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -228,6 +228,156 @@ static CharDriverState *qemu_chr_open_null(QemuOpts *opts)
     return chr;
 }
 
+/* Tee driver */
+typedef struct {
+    CharDriverState *basechr; /* base io*/
+    CharDriverState *filechr; /* duplicate output to file */
+} TeeDriver;
+
+static void tee_init(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->init) {
+        s->basechr->init(s->basechr);
+    }
+    if (s->filechr->init) {
+        s->filechr->init(s->filechr);
+    }
+}
+
+static void tee_chr_update_read_handler(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    qemu_chr_add_handlers(s->basechr, chr->chr_can_read, chr->chr_read,
+                              chr->chr_event, chr->handler_opaque);
+}
+
+/* tee_chr_write will return the write result of basechr, write result to file
+ * will be ignored. FIX ME. */
+static int tee_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->filechr->chr_write) {
+        s->filechr->chr_write(s->filechr, buf, len);
+    }
+    if (s->basechr->chr_write) {
+        return s->basechr->chr_write(s->basechr, buf, len);
+    }
+    return 0;
+}
+
+static void tee_chr_close(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_close) {
+        s->basechr->chr_close(s->basechr);
+    }
+    if (s->filechr->chr_close) {
+        s->filechr->chr_close(s->filechr);
+    }
+    qemu_free(s);
+}
+
+static int tee_chr_ioctl(CharDriverState *chr, int cmd, void *arg)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_ioctl) {
+        return s->basechr->chr_ioctl(s->basechr, cmd, arg);
+    }
+    return 0;
+}
+
+static int tee_get_msgfd(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->get_msgfd) {
+        return s->basechr->get_msgfd(s->basechr);
+    }
+    return -1;
+}
+
+static void tee_chr_send_event(CharDriverState *chr, int event)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_send_event) {
+        s->basechr->chr_send_event(s->basechr, event);
+    }
+}
+
+static void tee_chr_accept_input(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_accept_input) {
+        s->basechr->chr_accept_input(s->basechr);
+    }
+}
+static void tee_chr_set_echo(CharDriverState *chr, bool echo)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_set_echo) {
+        s->basechr->chr_set_echo(s->basechr, echo);
+    }
+}
+static void tee_chr_guest_open(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_guest_open) {
+        s->basechr->chr_guest_open(s->basechr);
+    }
+}
+static void tee_chr_guest_close(CharDriverState *chr)
+{
+    TeeDriver *s = chr->opaque;
+    if (s->basechr->chr_guest_close) {
+        s->basechr->chr_guest_close(s->basechr);
+    }
+}
+
+static CharDriverState *qemu_chr_open_tee(QemuOpts *opts)
+{
+    CharDriverState *chr;
+    TeeDriver *d;
+    CharDriverState *basechr;
+    CharDriverState *filechr;
+    const char *label = qemu_opts_id(opts);
+    const char *tee_fpath = qemu_opt_get(opts, "tee_fpath");
+    const char *tee_backend = qemu_opt_get(opts, "tee_backend");
+    char *new_label, *new_filename;
+    int sz;
+
+    chr = qemu_mallocz(sizeof(CharDriverState));
+    d = qemu_mallocz(sizeof(TeeDriver));
+
+    sz = strlen(label)+3;
+    new_label = qemu_malloc(sz);
+    snprintf(new_label, sz, "%s-0", label);
+    basechr = qemu_chr_open(new_label, tee_backend, NULL);
+
+    snprintf(new_label, sz, "%s-1", label);
+    sz = strlen(tee_fpath)+6;
+    new_filename = qemu_malloc(sz);
+    snprintf(new_filename, sz, "file:%s", tee_fpath);
+    filechr = qemu_chr_open(new_label, new_filename, NULL);
+    qemu_free(new_label);
+    qemu_free(new_filename);
+
+    d->basechr = basechr;
+    d->filechr = filechr;
+    chr->opaque = d;
+    chr->init = tee_init;
+    chr->chr_write = tee_chr_write;
+    chr->chr_close = tee_chr_close;
+    chr->chr_update_read_handler = tee_chr_update_read_handler;
+    chr->chr_ioctl = tee_chr_ioctl;
+    chr->get_msgfd = tee_get_msgfd;
+    chr->chr_send_event = tee_chr_send_event;
+    chr->chr_accept_input = tee_chr_accept_input;
+    chr->chr_set_echo = tee_chr_set_echo;
+    chr->chr_guest_open = tee_chr_guest_open;
+    chr->chr_guest_close = tee_chr_guest_close;
+
+    return chr;
+}
 /* MUX driver for serial I/O splitting */
 #define MAX_MUX 4
 #define MUX_BUFFER_SIZE 32     /* Must be a power of 2.  */
@@ -2356,6 +2506,16 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const 
char *filename)
         qemu_opt_set(opts, "mux", "on");
     }
 
+    if (strstart(filename, "tee:", &p)) {
+        char tee_fpath[1024];
+        p = get_opt_value(tee_fpath, sizeof(tee_fpath), p);
+        filename = p+1;
+        qemu_opt_set(opts, "tee_backend", filename);
+        qemu_opt_set(opts, "tee_fpath", tee_fpath);
+        qemu_opt_set(opts, "backend", "tee");
+        return opts;
+   }
+
     if (strcmp(filename, "null")    == 0 ||
         strcmp(filename, "pty")     == 0 ||
         strcmp(filename, "msmouse") == 0 ||
@@ -2468,6 +2628,7 @@ static const struct {
     const char *name;
     CharDriverState *(*open)(QemuOpts *opts);
 } backend_table[] = {
+    { .name = "tee",       .open = qemu_chr_open_tee },
     { .name = "null",      .open = qemu_chr_open_null },
     { .name = "socket",    .open = qemu_chr_open_socket },
     { .name = "udp",       .open = qemu_chr_open_udp },
@@ -2536,7 +2697,12 @@ CharDriverState *qemu_chr_open_opts(QemuOpts *opts,
 
     if (!chr->filename)
         chr->filename = qemu_strdup(qemu_opt_get(opts, "backend"));
-    chr->init = init;
+    if (strcmp(qemu_opt_get(opts, "backend"), "tee") == 0) {
+        TeeDriver *s = chr->opaque;
+        s->basechr->init = init;
+    } else {
+        chr->init = init;
+    }
     QTAILQ_INSERT_TAIL(&chardevs, chr, next);
 
     if (qemu_opt_get_bool(opts, "mux", 0)) {
diff --git a/qemu-config.c b/qemu-config.c
index c63741c..b82516f 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -151,6 +151,12 @@ static QemuOptsList qemu_chardev_opts = {
         },{
             .name = "debug",
             .type = QEMU_OPT_NUMBER,
+        },{
+            .name = "tee_backend",
+            .type = QEMU_OPT_STRING,
+        },{
+            .name = "tee_fpath",
+            .type = QEMU_OPT_STRING,
         },
         { /* end of list */ }
     },
diff --git a/qemu-options.hx b/qemu-options.hx
index e6d7adc..1496f34 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1428,6 +1428,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
 #if defined(CONFIG_SPICE)
     "-chardev spicevmc,id=id,name=name[,debug=debug]\n"
 #endif
+    "-chardev tee,id=id,tee_backend=dev_string,tee_fpath=path\n"
     , QEMU_ARCH_ALL
 )
 
@@ -1453,7 +1454,8 @@ Backend is one of:
 @option{braille},
 @option{tty},
 @option{parport},
address@hidden
address@hidden,
address@hidden
 The specific backend will determine the applicable options.
 
 All devices must have an id, which can be any string up to 127 characters long.
@@ -1639,6 +1641,18 @@ required.
 Connect to a spice virtual machine channel, such as vdiport.
 #endif
 
address@hidden -chardev tee ,address@hidden ,address@hidden ,address@hidden
+
address@hidden any kind of char device specified above. Double each comma
+in device string to ensure the whole device string is the option value, "id" in
+device string could be ignored. For example:
+tee_backend=stdio,,mux=on,,signal=on
+
address@hidden file path where char device output content is duplicated to.
+
+Connect to a device specified by dev_string, and duplicate output content of
+that device to a file.
+
 @end table
 ETEXI
 
@@ -1878,6 +1892,15 @@ A unix domain socket is used instead of a tcp socket.  
The option works the
 same as if you had specified @code{-serial tcp} except the unix domain socket
 @var{path} is used for connections.
 
address@hidden tee:@var{path},@var{dev_string}
+Tee can duplicate output content of a serial device to a file.
address@hidden is the file path where output content is duplicated to.
address@hidden should be any one of the serial devices specified
+above. An example would be:
address@hidden @code
address@hidden -serial tee:/var/log/test.log,pty
address@hidden table
+
 @item mon:@var{dev_string}
 This is a special option to allow the monitor to be multiplexed onto
 another serial port.  The monitor is accessed with key sequence of
-- 
1.7.3.4