diff --git a/kernel/Makefile b/kernel/Makefile
index 0991c56..b4b4a76 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -63,6 +63,7 @@ SRCFILES += $(call GRABSRC, \
 							rbuf \
 							ipc/pipe \
 							drivers/ps2kb \
+							drivers/serial \
 							dev \
             )
 
diff --git a/kernel/dev/dev.c b/kernel/dev/dev.c
index c1351f5..9a5fedb 100644
--- a/kernel/dev/dev.c
+++ b/kernel/dev/dev.c
@@ -6,6 +6,7 @@
 #include "hal/hal.h"
 #include "termdev.h"
 #include "ps2kbdev.h"
+#include "serialdev.h"
 
 DevTable DEVTABLE;
 
@@ -15,4 +16,5 @@ void dev_init(void) {
 
   termdev_init();
   ps2kbdev_init();
+  serialdev_init();
 }
diff --git a/kernel/dev/dev.h b/kernel/dev/dev.h
index 00410fb..3cfeefe 100644
--- a/kernel/dev/dev.h
+++ b/kernel/dev/dev.h
@@ -12,6 +12,7 @@ typedef struct {
   int _hshtbstate;
   char ident[0x100];
   DevFn fns[DEV_FNS_MAX];
+  SpinLock spinlock;
 } Dev;
 
 
diff --git a/kernel/dev/ps2kbdev.c b/kernel/dev/ps2kbdev.c
index 5f0b029..b5b7e95 100644
--- a/kernel/dev/ps2kbdev.c
+++ b/kernel/dev/ps2kbdev.c
@@ -33,5 +33,6 @@ void ps2kbdev_init(void) {
 
   Dev *ps2kbdev;
   HSHTB_ALLOC(DEVTABLE.devs, ident, "ps2kbdev", ps2kbdev);
+  spinlock_init(&ps2kbdev->spinlock);
   ps2kbdev->fns[0] = &ps2kbdev_readch;
 }
diff --git a/kernel/dev/serialdev.c b/kernel/dev/serialdev.c
new file mode 100644
index 0000000..ed0dd91
--- /dev/null
+++ b/kernel/dev/serialdev.c
@@ -0,0 +1,42 @@
+#include <stdint.h>
+#include <stddef.h>
+#include "dev.h"
+#include "serialdev.h"
+#include "errors.h"
+#include "util/util.h"
+#include "hshtb.h"
+#include "sysdefs/devctl.h"
+#include "drivers/serial/serial.h"
+#include "kprintf.h"
+
+int32_t serialdev_sendb(uint8_t *buffer, size_t len, void *extra) {
+  (void)len; (void)extra;
+  serial_sendb(buffer[0]);
+  return E_OK;
+}
+
+int32_t serialdev_sendready(uint8_t *buffer, size_t len, void *extra) {
+  (void)buffer; (void)len; (void) extra;
+  return serial_sendready();
+}
+
+int32_t serialdev_recvb(uint8_t *buffer, size_t len, void *extra) {
+  (void)buffer; (void)len; (void)extra;
+  return serial_recvb();
+}
+
+int32_t serialdev_recvready(uint8_t *buffer, size_t len, void *extra) {
+  (void)buffer; (void)len; (void)extra;
+  return serial_recvready();
+}
+
+void serialdev_init(void) {
+  Dev *serialdev = NULL;
+  HSHTB_ALLOC(DEVTABLE.devs, ident, "serialdev", serialdev);
+  serialdev->fns[DEV_SERIALDEV_SENDB] = &serialdev_sendb;
+  serialdev->fns[DEV_SERIALDEV_SENDREADY] = &serialdev_sendready;
+  serialdev->fns[DEV_SERIALDEV_RECVB] = &serialdev_recvb;
+  serialdev->fns[DEV_SERIALDEV_RECVREADY] = &serialdev_recvready;
+  spinlock_init(&serialdev->spinlock);
+  serial_init();
+}
diff --git a/kernel/dev/serialdev.h b/kernel/dev/serialdev.h
new file mode 100644
index 0000000..43ee298
--- /dev/null
+++ b/kernel/dev/serialdev.h
@@ -0,0 +1,10 @@
+#ifndef DEV_SERIALDEV_H_
+#define DEV_SERIALDEV_H_
+
+int32_t serialdev_sendb(uint8_t *buffer, size_t len, void *extra);
+int32_t serialdev_sendready(uint8_t *buffer, size_t len, void *extra);
+int32_t serialdev_recvb(uint8_t *buffer, size_t len, void *extra);
+int32_t serialdev_recvready(uint8_t *buffer, size_t len, void *extra);
+void serialdev_init(void);
+
+#endif // DEV_SERIALDEV_H_
diff --git a/kernel/dev/termdev.c b/kernel/dev/termdev.c
index 2723a5d..7e3c489 100644
--- a/kernel/dev/termdev.c
+++ b/kernel/dev/termdev.c
@@ -17,4 +17,5 @@ void termdev_init(void) {
   Dev *termdev = NULL;
   HSHTB_ALLOC(DEVTABLE.devs, ident, "termdev", termdev);
   termdev->fns[0] = &termdev_putch;
+  spinlock_init(&termdev->spinlock);
 }
diff --git a/kernel/drivers/serial/serial.c b/kernel/drivers/serial/serial.c
new file mode 100644
index 0000000..811ae80
--- /dev/null
+++ b/kernel/drivers/serial/serial.c
@@ -0,0 +1,42 @@
+#include <stdint.h>
+#include "hal/hal.h"
+#include "kprintf.h"
+
+// https://wiki.osdev.org/Serial_Ports
+
+#define PORT 0x3f8
+
+void serial_init(void) {
+  io_out8(PORT+1, 0x00);
+  io_out8(PORT+3, 0x80);
+  io_out8(PORT+0, 0x03);
+  io_out8(PORT+1, 0x00);
+  io_out8(PORT+3, 0x03);
+  io_out8(PORT+2, 0xC7);
+  io_out8(PORT+4, 0x0B);
+  io_out8(PORT+4, 0x1E);
+  io_out8(PORT+0, 0xAE);
+
+  if (io_in8(PORT+0) != 0xAE) {
+    ERR("serial", "serial is faulty!\n");
+    return;
+  }
+
+  io_out8(PORT+4, 0x0F);
+}
+
+int serial_recvready(void) {
+  return io_in8(PORT+5) & 1;
+}
+
+uint8_t serial_recvb(void) {
+  return io_in8(PORT);
+}
+
+int serial_sendready(void) {
+  return io_in8(PORT+5) & 0x20;
+}
+
+void serial_sendb(uint8_t b) {
+  io_out8(PORT, b);
+}
diff --git a/kernel/drivers/serial/serial.h b/kernel/drivers/serial/serial.h
new file mode 100644
index 0000000..c2538e2
--- /dev/null
+++ b/kernel/drivers/serial/serial.h
@@ -0,0 +1,12 @@
+#ifndef DRIVERS_SERIAL_SERIAL_H_
+#define DRIVERS_SERIAL_SERIAL_H_
+
+#include <stdint.h>
+
+void serial_init(void);
+int serial_recvready(void);
+uint8_t serial_recvb(void);
+int serial_sendready(void);
+void serial_sendb(uint8_t b);
+
+#endif // DRIVERS_SERIAL_SERIAL_H_
diff --git a/kernel/hshtb.h b/kernel/hshtb.h
index 307805e..cbcca3b 100644
--- a/kernel/hshtb.h
+++ b/kernel/hshtb.h
@@ -26,13 +26,17 @@ enum {
   HSHTB_TOMB = 2,
 };
 
+#define __HSHTB_ARRAY_LEN(tb) \
+ ((void)sizeof(struct { int _[!!(sizeof(tb) % sizeof((tb)[0]) == 0)]; }) , (sizeof(tb) / sizeof((tb)[0])))
+
 #define HSHTB_ALLOC(tb, keyfield, k, out) \
   do { \
-    size_t __len = sizeof((tb)) / sizeof((tb)[0]); \
+    size_t __len = __HSHTB_ARRAY_LEN(tb); \
     uint32_t __h = hshtb_fnv32((k), hal_strlen((k))); \
     size_t __idx = __h % __len; \
     size_t __start = __idx; \
     typeof(&(tb)[0]) __tomb = NULL; \
+    (out) = NULL; \
     do { \
       if ((tb)[__idx]._hshtbstate == HSHTB_EMPTY) { \
         typeof(&(tb)[0]) __slot = __tomb ? __tomb : &(tb)[__idx]; \
@@ -55,7 +59,7 @@ enum {
 
 #define HSHTB_GET(tb, keyfield, k, out) \
   do { \
-    size_t __len = sizeof((tb)) / sizeof((tb)[0]); \
+    size_t __len = __HSHTB_ARRAY_LEN(tb); \
     uint32_t __h = hshtb_fnv32((k), hal_strlen((k))); \
     size_t __idx = __h % __len; \
     size_t __start = __idx; \
@@ -77,7 +81,7 @@ enum {
     typeof(&(tb)[0]) __e; \
     HSHTB_GET((tb), (keyfield), (k), __e); \
     if (__e) { \
-      __e->state = HSHTB_TOMB; \
+      __e->_hshtbstate = HSHTB_TOMB; \
     } \
   } while(0)
 
diff --git a/kernel/kmain.c b/kernel/kmain.c
index fc077a6..cc75f77 100644
--- a/kernel/kmain.c
+++ b/kernel/kmain.c
@@ -11,8 +11,7 @@
 #include "storedev/storedev.h"
 #include "util/util.h"
 #include "proc/proc.h"
-#include "dev/termdev.h"
-#include "dev/ps2kbdev.h"
+#include "dev/dev.h"
 
 const char *human_size(uint64_t bytes, char *buf, size_t bufsize) {
   static const char *units[] = { "B", "KiB", "MiB", "GiB", "TiB", "PiB" };
@@ -66,8 +65,7 @@ void kmain(void) {
   storedev_init();
   baseimg_init();
   vfs_init();
-  termdev_init();
-  ps2kbdev_init();
+  dev_init();
   proc_init();
 
   for(;;);
diff --git a/kernel/syscall/devctl.c b/kernel/syscall/devctl.c
index c8aae23..11763e4 100644
--- a/kernel/syscall/devctl.c
+++ b/kernel/syscall/devctl.c
@@ -27,8 +27,10 @@ int32_t SYSCALL5(sys_devctl, devh1, cmd1, buffer1, len1, extra1) {
         goto done;
       }
 
+      spinlock_acquire(&DEVTABLE.spinlock);
       Dev *founddev;
       HSHTB_GET(DEVTABLE.devs, ident, ident, founddev);
+      spinlock_release(&DEVTABLE.spinlock);
 
       if (founddev == NULL) {
         ret = E_NOENTRY;
@@ -66,7 +68,9 @@ int32_t SYSCALL5(sys_devctl, devh1, cmd1, buffer1, len1, extra1) {
         ret = E_NOENTRY;
         goto done;
       }
+      spinlock_acquire(&dev->spinlock);
       ret = dev->fns[cmd]((uint8_t *)buffer1, (size_t)len1, (void *)extra1);
+      spinlock_release(&dev->spinlock);
     } break;
   }
 
diff --git a/share/sysdefs/devctl.h b/share/sysdefs/devctl.h
index 658ce0e..f5ce38b 100644
--- a/share/sysdefs/devctl.h
+++ b/share/sysdefs/devctl.h
@@ -3,6 +3,15 @@
 
 #define DEVCTL_GET_HANDLE 100
 
+#define DEV_TERMDEV_PUTCH 0
+
+#define DEV_PS2KBDEV_READCH 0
+
+#define DEV_SERIALDEV_SENDB     0
+#define DEV_SERIALDEV_SENDREADY 1
+#define DEV_SERIALDEV_RECVB     2
+#define DEV_SERIALDEV_RECVREADY 3
+
 #if !defined(__ASSEMBLER__)
 
 typedef uint64_t Dev_t;
diff --git a/ulib/dev.h b/ulib/dev.h
deleted file mode 100644
index 26346fd..0000000
--- a/ulib/dev.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef ULIB_DEV_H_
-#define ULIB_DEV_H_
-
-#define DEV_TERMDEV_PUTCH 0
-
-#define DEV_PS2KBDEV_READCH 0
-
-#endif // ULIB_DEV_H_
diff --git a/ulib/ulib.h b/ulib/ulib.h
index f759138..0d66b84 100644
--- a/ulib/ulib.h
+++ b/ulib/ulib.h
@@ -16,7 +16,6 @@
 #include <log.h>
 #include <assert.h>
 #include <umalloc/umalloc.h>
-#include <dev.h>
 #include <fs/path.h>
 
 #include <errors.h>
diff --git a/user/init/main.c b/user/init/main.c
index 0d99c0b..95f0176 100644
--- a/user/init/main.c
+++ b/user/init/main.c
@@ -35,6 +35,11 @@ void main(void) {
   PID = (uint64_t)processctl(-1, PCTL_GETPID, 0, 0, 0);
   devctl(&ps2kbdev, DEVCTL_GET_HANDLE, (uint8_t *)"ps2kbdev", 0, 0);
 
+  Dev_t serialdev;
+  int32_t err = devctl(&serialdev, DEVCTL_GET_HANDLE, (uint8_t *)"serialdev", 0, 0);
+  uint8_t a = 'A';
+  devctl(&serialdev, DEV_SERIALDEV_SENDB, &a, 1, 0);
+
   tb_runinitscript();
 
   uprintf("Shell exited! Please reboot the system.\n");