[Xen-devel] [PATCH] vixen: transmit NUL characters received from guest serial port

[Sarah Newman <srn@xxxxxxxxx>]

Certain programs, such as the NetBSD installer, include NUL characters
in their output. Using null-terminated strings for transmitting data
from the guest to the L0 hypervisor meant the output was being corrupted.

This makes only the required changes for vixen to work properly.
Future work could include generally switching away from null-terminated
strings within the xen console code.

Signed-off-by: Sarah Newman <srn@xxxxxxxxx>
---
 xen/arch/x86/guest/vixen.c |  4 ++--
 xen/drivers/char/console.c | 14 +++++++++++---
 xen/drivers/char/serial.c  | 35 +++++++++++++++++++++++++++++++++++
 xen/include/xen/lib.h      |  2 +-
 xen/include/xen/serial.h   |  3 +++
 5 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/guest/vixen.c b/xen/arch/x86/guest/vixen.c
index 9cb1a80..1b1d2e0 100644
--- a/xen/arch/x86/guest/vixen.c
+++ b/xen/arch/x86/guest/vixen.c
@@ -304,7 +304,7 @@ bool vixen_ring_process(uint16_t port)
         char ch = r->out[MASK_XENCONS_IDX(r->out_cons, r->out)];
         if (n == sizeof(buffer) - 1) {
             buffer[n] = 0;
-            guest_puts(hardware_domain, buffer);
+            guest_putsn(hardware_domain, buffer, n);
             n = 0;
         }
         buffer[n++] = ch;
@@ -314,7 +314,7 @@ bool vixen_ring_process(uint16_t port)
 
     if (n) {
         buffer[n] = 0;
-        guest_puts(hardware_domain, buffer);
+        guest_putsn(hardware_domain, buffer, n);
     }
 
     spin_unlock(&vixen_xencons_lock);
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 38a5d67..ba22cdf 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -341,6 +341,14 @@ static void sercon_puts(const char *s)
         serial_puts(sercon_handle, s);
 }
 
+static void sercon_putsn(const char *s, unsigned int count)
+{
+    if ( serial_steal_fn != NULL )
+        (*serial_steal_fn)(s);
+    else
+        serial_putsn(sercon_handle, s, count);
+}
+
 static void dump_console_ring_key(unsigned char key)
 {
     uint32_t idx, len, sofar, c;
@@ -461,7 +469,7 @@ static long 
guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
             /* Use direct console output as it could be interactive */
             spin_lock_irq(&console_lock);
 
-            sercon_puts(kbuf);
+            sercon_putsn(kbuf, count);
             video_puts(kbuf);
 
             if ( opt_console_to_ring )
@@ -761,11 +769,11 @@ void guest_printk(const struct domain *d, const char 
*fmt, ...)
     va_end(args);
 }
 
-void guest_puts(const struct domain *d, const char *kbuf)
+void guest_putsn(const struct domain *d, const char *kbuf, unsigned int count)
 {
     spin_lock_irq(&console_lock);
 
-    sercon_puts(kbuf);
+    sercon_putsn(kbuf, count);
     video_puts(kbuf);
 
     if ( opt_console_to_ring )
diff --git a/xen/drivers/char/serial.c b/xen/drivers/char/serial.c
index 09a20ac..e90378a 100644
--- a/xen/drivers/char/serial.c
+++ b/xen/drivers/char/serial.c
@@ -223,6 +223,41 @@ void serial_putc(int handle, char c)
     spin_unlock_irqrestore(&port->tx_lock, flags);
 }
 
+void serial_putsn(int handle, const char *s, unsigned int count)
+{
+    struct serial_port *port;
+    unsigned long flags;
+    char c;
+
+    if ( handle == -1 )
+        return;
+
+    port = &com[handle & SERHND_IDX];
+    if ( !port->driver || !port->driver->putc )
+        return;
+
+    spin_lock_irqsave(&port->tx_lock, flags);
+
+    for (unsigned int i = 0; i < count; i++)
+    {
+        c = *s++;
+        if ( (c == '\n') && (handle & SERHND_COOKED) )
+            __serial_putc(port, '\r' | ((handle & SERHND_HI) ? 0x80 : 0x00));
+
+        if ( handle & SERHND_HI )
+            c |= 0x80;
+        else if ( handle & SERHND_LO )
+            c &= 0x7f;
+
+        __serial_putc(port, c);
+    }
+
+    if ( port->driver->flush )
+        port->driver->flush(port);
+
+    spin_unlock_irqrestore(&port->tx_lock, flags);
+}
+
 void serial_puts(int handle, const char *s)
 {
     struct serial_port *port;
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index 5359fa4..baccae0 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -91,7 +91,7 @@ extern void printk(const char *format, ...)
     __attribute__ ((format (printf, 1, 2)));
 extern void guest_printk(const struct domain *d, const char *format, ...)
     __attribute__ ((format (printf, 2, 3)));
-extern void guest_puts(const struct domain *d, const char *message);
+extern void guest_putsn(const struct domain *d, const char *message, unsigned 
int count);
 extern void noreturn panic(const char *format, ...)
     __attribute__ ((format (printf, 1, 2)));
 extern long vm_assist(struct domain *, unsigned int cmd, unsigned int type,
diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
index 1212a12..87dbdcf 100644
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -115,6 +115,9 @@ void serial_putc(int handle, char c);
 /* Transmit a NULL-terminated string via the specified COM port. */
 void serial_puts(int handle, const char *s);
 
+/* Transmit "count" characters via the specified COM port. */
+void serial_putsn(int handle, const char *s, unsigned int count);
+
 /*
  * An alternative to registering a character-receive hook. This function
  * will not return until a character is available. It can safely be
-- 
1.9.1


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