diff --git a/xen/arch/arm/early_printk.c b/xen/arch/arm/early_printk.c
index 97466a12b1..333073d97e 100644
--- a/xen/arch/arm/early_printk.c
+++ b/xen/arch/arm/early_printk.c
@@ -17,9 +17,10 @@
 void early_putch(char c);
 void early_flush(void);
 
-void early_puts(const char *s)
+void early_puts(const char *s, size_t nr)
 {
-    while (*s != '\0') {
+    while ( nr-- > 0 )
+    {
         if (*s == '\n')
             early_putch('\r');
         early_putch(*s);
diff --git a/xen/common/gdbstub.c b/xen/common/gdbstub.c
index 07095e1ec7..6234834a20 100644
--- a/xen/common/gdbstub.c
+++ b/xen/common/gdbstub.c
@@ -68,7 +68,7 @@ static void gdb_smp_resume(void);
 static char __initdata opt_gdb[30];
 string_param("gdb", opt_gdb);
 
-static void gdbstub_console_puts(const char *str);
+static void gdbstub_console_puts(const char *str, size_t nr);
 
 /* value <-> char (de)serialzers */
 static char
@@ -546,14 +546,14 @@ __gdb_ctx = {
 static struct gdb_context *gdb_ctx = &__gdb_ctx;
 
 static void
-gdbstub_console_puts(const char *str)
+gdbstub_console_puts(const char *str, size_t nr)
 {
     const char *p;
 
     gdb_start_packet(gdb_ctx);
     gdb_write_to_packet_char('O', gdb_ctx);
 
-    for ( p = str; *p != '\0'; p++ )
+    for ( p = str; nr > 0; p++, nr-- )
     {
         gdb_write_to_packet_char(hex2char((*p>>4) & 0x0f), gdb_ctx );
         gdb_write_to_packet_char(hex2char((*p) & 0x0f), gdb_ctx );
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index d728e737d1..23fe0296df 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -326,9 +326,9 @@ long read_console_ring(struct xen_sysctl_readconsole *op)
 static char serial_rx_ring[SERIAL_RX_SIZE];
 static unsigned int serial_rx_cons, serial_rx_prod;
 
-static void (*serial_steal_fn)(const char *) = early_puts;
+static void (*serial_steal_fn)(const char *, size_t nr) = early_puts;
 
-int console_steal(int handle, void (*fn)(const char *))
+int console_steal(int handle, void (*fn)(const char *, size_t nr))
 {
     if ( (handle == -1) || (handle != sercon_handle) )
         return 0;
@@ -346,15 +346,15 @@ void console_giveback(int id)
         serial_steal_fn = NULL;
 }
 
-static void sercon_puts(const char *s)
+static void sercon_puts(const char *s, size_t nr)
 {
     if ( serial_steal_fn != NULL )
-        (*serial_steal_fn)(s);
+        serial_steal_fn(s, nr);
     else
-        serial_puts(sercon_handle, s);
+        serial_puts(sercon_handle, s, nr);
 
     /* Copy all serial output into PV console */
-    pv_console_puts(s);
+    pv_console_puts(s, nr);
 }
 
 static void dump_console_ring_key(unsigned char key)
@@ -387,10 +387,9 @@ static void dump_console_ring_key(unsigned char key)
         sofar += len;
         c += len;
     }
-    buf[sofar] = '\0';
 
-    sercon_puts(buf);
-    video_puts(buf);
+    sercon_puts(buf, sofar);
+    video_puts(buf, sofar);
 
     free_xenheap_pages(buf, order);
 }
@@ -528,7 +527,7 @@ static inline void xen_console_write_debug_port(const char *buf, size_t len)
 static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
 {
     char kbuf[128];
-    int kcount = 0;
+    unsigned int kcount = 0;
     struct domain *cd = current->domain;
 
     while ( count > 0 )
@@ -541,25 +540,22 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
         kcount = min_t(int, count, sizeof(kbuf)-1);
         if ( copy_from_guest(kbuf, buffer, kcount) )
             return -EFAULT;
-        kbuf[kcount] = '\0';
 
         if ( is_hardware_domain(cd) )
         {
             /* Use direct console output as it could be interactive */
             spin_lock_irq(&console_lock);
 
-            sercon_puts(kbuf);
-            video_puts(kbuf);
+            sercon_puts(kbuf, kcount);
+            video_puts(kbuf, kcount);
 
 #ifdef CONFIG_X86
             if ( opt_console_xen )
             {
-                size_t len = strlen(kbuf);
-
                 if ( xen_guest )
-                    xen_hypercall_console_write(kbuf, len);
+                    xen_hypercall_console_write(kbuf, kcount);
                 else
-                    xen_console_write_debug_port(kbuf, len);
+                    xen_console_write_debug_port(kbuf, kcount);
             }
 #endif
 
@@ -576,19 +572,20 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
             char *kin = kbuf, *kout = kbuf, c;
 
             /* Strip non-printable characters */
-            for ( ; ; )
+            do
             {
                 c = *kin++;
-                if ( c == '\0' || c == '\n' )
+                if ( c == '\n' )
                     break;
                 if ( isprint(c) || c == '\t' )
                     *kout++ = c;
-            }
+            } while ( --kcount > 0 );
+
             *kout = '\0';
             spin_lock(&cd->pbuf_lock);
+            kcount = kin - kbuf;
             if ( c == '\n' )
             {
-                kcount = kin - kbuf;
                 cd->pbuf[cd->pbuf_idx] = '\0';
                 guest_printk(cd, XENLOG_G_DEBUG "%s%s\n", cd->pbuf, kbuf);
                 cd->pbuf_idx = 0;
@@ -667,16 +664,16 @@ static bool_t console_locks_busted;
 
 static void __putstr(const char *str)
 {
+    size_t len = strlen(str);
+
     ASSERT(spin_is_locked(&console_lock));
 
-    sercon_puts(str);
-    video_puts(str);
+    sercon_puts(str, len);
+    video_puts(str, len);
 
 #ifdef CONFIG_X86
     if ( opt_console_xen )
     {
-        size_t len = strlen(str);
-
         if ( xen_guest )
             xen_hypercall_console_write(str, len);
         else
@@ -1250,6 +1247,7 @@ void debugtrace_printk(const char *fmt, ...)
     char          cntbuf[24];
     va_list       args;
     unsigned long flags;
+    unsigned int nr;
 
     if ( debugtrace_bytes == 0 )
         return;
@@ -1261,14 +1259,15 @@ void debugtrace_printk(const char *fmt, ...)
     ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
 
     va_start(args, fmt);
-    vsnprintf(buf, sizeof(buf), fmt, args);
+    nr = vscnprintf(buf, sizeof(buf), fmt, args);
     va_end(args);
 
     if ( debugtrace_send_to_console )
     {
-        snprintf(cntbuf, sizeof(cntbuf), "%u ", ++count);
-        serial_puts(sercon_handle, cntbuf);
-        serial_puts(sercon_handle, buf);
+        unsigned int n = scnprintf(cntbuf, sizeof(cntbuf), "%u ", ++count);
+
+        serial_puts(sercon_handle, cntbuf, n);
+        serial_puts(sercon_handle, buf, nr);
     }
     else
     {
@@ -1381,7 +1380,7 @@ void panic(const char *fmt, ...)
  * **************************************************************
  */
 
-static void suspend_steal_fn(const char *str) { }
+static void suspend_steal_fn(const char *str, size_t nr) { }
 static int suspend_steal_id;
 
 int console_suspend(void)
diff --git a/xen/drivers/char/consoled.c b/xen/drivers/char/consoled.c
index 552abf5766..222e018442 100644
--- a/xen/drivers/char/consoled.c
+++ b/xen/drivers/char/consoled.c
@@ -77,16 +77,13 @@ size_t consoled_guest_rx(void)
 
         if ( idx >= BUF_SZ )
         {
-            pv_console_puts(buf);
+            pv_console_puts(buf, BUF_SZ);
             idx = 0;
         }
     }
 
     if ( idx )
-    {
-        buf[idx] = '\0';
-        pv_console_puts(buf);
-    }
+        pv_console_puts(buf, idx);
 
     /* No need for a mem barrier because every character was already consumed */
     barrier();
diff --git a/xen/drivers/char/serial.c b/xen/drivers/char/serial.c
index 221a14c092..88cd876790 100644
--- a/xen/drivers/char/serial.c
+++ b/xen/drivers/char/serial.c
@@ -223,11 +223,10 @@ void serial_putc(int handle, char c)
     spin_unlock_irqrestore(&port->tx_lock, flags);
 }
 
-void serial_puts(int handle, const char *s)
+void serial_puts(int handle, const char *s, size_t nr)
 {
     struct serial_port *port;
     unsigned long flags;
-    char c;
 
     if ( handle == -1 )
         return;
@@ -238,8 +237,10 @@ void serial_puts(int handle, const char *s)
 
     spin_lock_irqsave(&port->tx_lock, flags);
 
-    while ( (c = *s++) != '\0' )
+    for ( ; nr > 0; nr--, s++ )
     {
+        char c = *s;
+
         if ( (c == '\n') && (handle & SERHND_COOKED) )
             __serial_putc(port, '\r' | ((handle & SERHND_HI) ? 0x80 : 0x00));
 
diff --git a/xen/drivers/char/xen_pv_console.c b/xen/drivers/char/xen_pv_console.c
index cc1c1d743f..612784b074 100644
--- a/xen/drivers/char/xen_pv_console.c
+++ b/xen/drivers/char/xen_pv_console.c
@@ -129,13 +129,13 @@ size_t pv_console_rx(struct cpu_user_regs *regs)
     return recv;
 }
 
-static size_t pv_ring_puts(const char *buf)
+static size_t pv_ring_puts(const char *buf, size_t nr)
 {
     XENCONS_RING_IDX cons, prod;
     size_t sent = 0, avail;
     bool put_r = false;
 
-    while ( buf[sent] != '\0' || put_r )
+    while ( sent < nr || put_r )
     {
         cons = ACCESS_ONCE(cons_ring->out_cons);
         prod = cons_ring->out_prod;
@@ -156,7 +156,7 @@ static size_t pv_ring_puts(const char *buf)
             continue;
         }
 
-        while ( avail && (buf[sent] != '\0' || put_r) )
+        while ( avail && (sent < nr || put_r) )
         {
             if ( put_r )
             {
@@ -185,7 +185,7 @@ static size_t pv_ring_puts(const char *buf)
     return sent;
 }
 
-void pv_console_puts(const char *buf)
+void pv_console_puts(const char *buf, size_t nr)
 {
     unsigned long flags;
 
@@ -193,7 +193,7 @@ void pv_console_puts(const char *buf)
         return;
 
     spin_lock_irqsave(&tx_lock, flags);
-    pv_ring_puts(buf);
+    pv_ring_puts(buf, nr);
     spin_unlock_irqrestore(&tx_lock, flags);
 }
 
diff --git a/xen/drivers/video/lfb.c b/xen/drivers/video/lfb.c
index 5022195ae5..75b749b330 100644
--- a/xen/drivers/video/lfb.c
+++ b/xen/drivers/video/lfb.c
@@ -53,14 +53,15 @@ static void lfb_show_line(
 }
 
 /* Fast mode which redraws all modified parts of a 2D text buffer. */
-void lfb_redraw_puts(const char *s)
+void lfb_redraw_puts(const char *s, size_t nr)
 {
     unsigned int i, min_redraw_y = lfb.ypos;
-    char c;
 
     /* Paste characters into text buffer. */
-    while ( (c = *s++) != '\0' )
+    for ( ; nr > 0; nr--, s++ )
     {
+        char c = *s;
+
         if ( (c == '\n') || (lfb.xpos >= lfb.lfbp.text_columns) )
         {
             if ( ++lfb.ypos >= lfb.lfbp.text_rows )
@@ -97,13 +98,14 @@ void lfb_redraw_puts(const char *s)
 }
 
 /* Slower line-based scroll mode which interacts better with dom0. */
-void lfb_scroll_puts(const char *s)
+void lfb_scroll_puts(const char *s, size_t nr)
 {
     unsigned int i;
-    char c;
 
-    while ( (c = *s++) != '\0' )
+    for ( ; nr > 0; nr--, s++ )
     {
+        char c = *s;
+
         if ( (c == '\n') || (lfb.xpos >= lfb.lfbp.text_columns) )
         {
             unsigned int bytes = (lfb.lfbp.width *
diff --git a/xen/drivers/video/lfb.h b/xen/drivers/video/lfb.h
index ac40a66379..e743ccdd6b 100644
--- a/xen/drivers/video/lfb.h
+++ b/xen/drivers/video/lfb.h
@@ -35,8 +35,8 @@ struct lfb_prop {
     unsigned int text_rows;
 };
 
-void lfb_redraw_puts(const char *s);
-void lfb_scroll_puts(const char *s);
+void lfb_redraw_puts(const char *s, size_t nr);
+void lfb_scroll_puts(const char *s, size_t nr);
 void lfb_carriage_return(void);
 void lfb_free(void);
 
diff --git a/xen/drivers/video/vga.c b/xen/drivers/video/vga.c
index 454457ade8..666f2e2509 100644
--- a/xen/drivers/video/vga.c
+++ b/xen/drivers/video/vga.c
@@ -18,9 +18,9 @@ static int vgacon_keep;
 static unsigned int xpos, ypos;
 static unsigned char *video;
 
-static void vga_text_puts(const char *s);
-static void vga_noop_puts(const char *s) {}
-void (*video_puts)(const char *) = vga_noop_puts;
+static void vga_text_puts(const char *s, size_t nr);
+static void vga_noop_puts(const char *s, size_t nr) {}
+void (*video_puts)(const char *, size_t nr) = vga_noop_puts;
 
 /*
  * 'vga=<mode-specifier>[,keep]' where <mode-specifier> is one of:
@@ -174,12 +174,12 @@ void __init video_endboot(void)
     }
 }
 
-static void vga_text_puts(const char *s)
+static void vga_text_puts(const char *s, size_t nr)
 {
-    char c;
-
-    while ( (c = *s++) != '\0' )
+    for ( ; nr > 0; nr--, s++ )
     {
+        char c = *s;
+
         if ( (c == '\n') || (xpos >= columns) )
         {
             if ( ++ypos >= lines )
diff --git a/xen/include/xen/console.h b/xen/include/xen/console.h
index b4f9463936..ba914f9e5b 100644
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -38,7 +38,7 @@ struct domain *console_input_domain(void);
  * Steal output from the console. Returns +ve identifier, else -ve error.
  * Takes the handle of the serial line to steal, and steal callback function.
  */
-int console_steal(int handle, void (*fn)(const char *));
+int console_steal(int handle, void (*fn)(const char *, size_t nr));
 
 /* Give back stolen console. Takes the identifier returned by console_steal. */
 void console_giveback(int id);
diff --git a/xen/include/xen/early_printk.h b/xen/include/xen/early_printk.h
index 2c3e1b3519..0f76c3a74f 100644
--- a/xen/include/xen/early_printk.h
+++ b/xen/include/xen/early_printk.h
@@ -5,7 +5,7 @@
 #define __XEN_EARLY_PRINTK_H__
 
 #ifdef CONFIG_EARLY_PRINTK
-void early_puts(const char *s);
+void early_puts(const char *s, size_t nr);
 #else
 #define early_puts NULL
 #endif
diff --git a/xen/include/xen/pv_console.h b/xen/include/xen/pv_console.h
index cb92539666..4745f46f2d 100644
--- a/xen/include/xen/pv_console.h
+++ b/xen/include/xen/pv_console.h
@@ -8,7 +8,7 @@
 void pv_console_init(void);
 void pv_console_set_rx_handler(serial_rx_fn fn);
 void pv_console_init_postirq(void);
-void pv_console_puts(const char *buf);
+void pv_console_puts(const char *buf, size_t nr);
 size_t pv_console_rx(struct cpu_user_regs *regs);
 evtchn_port_t pv_console_evtchn(void);
 
@@ -17,7 +17,7 @@ evtchn_port_t pv_console_evtchn(void);
 static inline void pv_console_init(void) {}
 static inline void pv_console_set_rx_handler(serial_rx_fn fn) { }
 static inline void pv_console_init_postirq(void) { }
-static inline void pv_console_puts(const char *buf) { }
+static inline void pv_console_puts(const char *buf, size_t nr) { }
 static inline size_t pv_console_rx(struct cpu_user_regs *regs) { return 0; }
 evtchn_port_t pv_console_evtchn(void)
 {
diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
index f2994d4093..6548f0b0a9 100644
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -114,8 +114,8 @@ int serial_parse_handle(char *conf);
 /* Transmit a single character via the specified COM port. */
 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 a string via the specified COM port. */
+void serial_puts(int handle, const char *s, size_t nr);
 
 /*
  * An alternative to registering a character-receive hook. This function
diff --git a/xen/include/xen/video.h b/xen/include/xen/video.h
index 2e897f9df5..96f8a50132 100644
--- a/xen/include/xen/video.h
+++ b/xen/include/xen/video.h
@@ -13,11 +13,11 @@
 
 #ifdef CONFIG_VIDEO
 void video_init(void);
-extern void (*video_puts)(const char *);
+extern void (*video_puts)(const char *, size_t nr);
 void video_endboot(void);
 #else
 #define video_init()    ((void)0)
-#define video_puts(s)   ((void)0)
+static inline void video_puts(const char *str, size_t nr) {}
 #define video_endboot() ((void)0)
 #endif