replay: character devices

This patch implements record and replay of character devices.
It records chardevs communication in replay mode. Recorded information
include data read from backend and counter of bytes written
from frontend to backend to preserve frontend internal state.
If character device was configured through the command line in record mode,
then in replay mode it should be also added to command line. Backend of
the character device could be changed in replay mode.
Replaying of devices that perform ioctl and get_msgfd operations is not
supported.
gdbstub which also acts as a backend is not recorded to allow controlling
the replaying through gdb. Monitor backends are also not recorded.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20160314074436.4980.83856.stgit@PASHA-ISP>
[Add stubs. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/include/sysemu/char.h b/include/sysemu/char.h
index e46884f367..4c2f777ad1 100644
--- a/include/sysemu/char.h
+++ b/include/sysemu/char.h
@@ -86,6 +86,7 @@ struct CharDriverState {
     int is_mux;
     guint fd_in_tag;
     QemuOpts *opts;
+    bool replay;
     QTAILQ_ENTRY(CharDriverState) next;
 };
 
@@ -139,6 +140,22 @@ CharDriverState *qemu_chr_new(const char *label, const char *filename,
                               void (*init)(struct CharDriverState *s));
 
 /**
+ * @qemu_chr_new_noreplay:
+ *
+ * Create a new character backend from a URI.
+ * Character device communications are not written
+ * into the replay log.
+ *
+ * @label the name of the backend
+ * @filename the URI
+ * @init not sure..
+ *
+ * Returns: a new character backend
+ */
+CharDriverState *qemu_chr_new_noreplay(const char *label, const char *filename,
+                                       void (*init)(struct CharDriverState *s));
+
+/**
  * @qemu_chr_delete:
  *
  * Destroy a character backend and remove it from the list of
@@ -341,6 +358,15 @@ int qemu_chr_be_can_write(CharDriverState *s);
  */
 void qemu_chr_be_write(CharDriverState *s, uint8_t *buf, int len);
 
+/**
+ * @qemu_chr_be_write_impl:
+ *
+ * Implementation of back end writing. Used by replay module.
+ *
+ * @buf a buffer to receive data from the front end
+ * @len the number of bytes to receive from the front end
+ */
+void qemu_chr_be_write_impl(CharDriverState *s, uint8_t *buf, int len);
 
 /**
  * @qemu_chr_be_event: