The spapr-vty device implements the PAPR defined virtual console,
which is also implemented by IBM's proprietary PowerVM hypervisor.
PowerVM's implementation has a bug where it inserts an extra \0 after
every \r going to the guest. Because of that Linux's guest side
driver has a workaround which strips \0 characters that appear
immediately after a \r.
That means that when running under qemu, sending a binary stream from
host to guest via spapr-vty which happens to include a \r\0 sequence
will get corrupted by that workaround.
To deal with that, this patch duplicates PowerVM's bug, inserting an
extra \0 after each \r. Ugly, but the best option available.
Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
---
hw/char/spapr_vty.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
index 0fa416ca6b..a95e5e91a7 100644
--- a/hw/char/spapr_vty.c
+++ b/hw/char/spapr_vty.c
@@ -58,6 +58,24 @@ static int vty_getchars(VIOsPAPRDevice *sdev, uint8_t *buf,
int max)
while ((n < max) && (dev->out != dev->in)) {
buf[n++] = dev->buf[dev->out++ % VTERM_BUFSIZE];
+
+ /* PowerVM's vty implementation has a bug where it inserts a
+ * \0 after every \r going to the guest. Existing guests have
+ * a workaround for this which removes every \0 immediately
+ * following a \r, so here we make ourselves bug-for-bug
+ * compatible, so that the guest won't drop a real \0-after-\r
+ * that happens to occur in a binary stream. */
+ if (buf[n-1] == '\r') {
+ if (n < max) {
+ buf[n++] = '\0';
+ } else {
+ /* No room for the extra \0, roll back and try again
+ * next time */
+ dev->out--;
+ n--;
+ break;
+ }
+ }
}
qemu_chr_fe_accept_input(&dev->chardev);
--
2.14.3
