Squashed commit of the following:

drivers/serial:  Add Ctrl-C/Ctrl-X support.  This is an initial working implementation that still requires that several details be resolved.

    sched/task/task_start.c: Add default signal action to SIGKILL.

TODO

@@ -1,4 +1,4 @@
-NuttX TODO List (Last updated June 21, 2018)
+NuttX TODO List (Last updated August 26, 2018)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This file summarizes known NuttX bugs, limitations, inconsistencies with
@@ -21,7 +21,7 @@ nuttx/:
   (5)  Binary loaders (binfmt/)
  (16)  Network (net/, drivers/net)
   (4)  USB (drivers/usbdev, drivers/usbhost)
-  (2)  Other drivers (drivers/)
+  (1)  Other drivers (drivers/)
  (12)  Libraries (libc/, libm/)
  (10)  File system/Generic drivers (fs/, drivers/)
  (10)  Graphics Subsystem (graphics/)
@@ -2138,14 +2138,6 @@ o Other drivers (drivers/)
                debug if you could see all of the SYSLOG output up to the
                time of the crash.  But not essential.
 
-  Title:       ADD SUPPORT FOR CONTROL-C
-  Description: Add support for control-C interrupts and perhaps other
-               interrupts generated from a keyboard.
-  Status:      Open
-  Priority:    Low.  This would make working with tasks at the NSH terminal
-               more like working with processes via a Bash shell.  That is
-               a feature enhancement.
-
 o Linux/Cywgin simulation (arch/sim)
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

drivers/serial/Kconfig

@@ -19,6 +19,18 @@ config SERIAL_CONSOLE
 	bool
 	default n
 
+config SERIAL_SIGKILL_CHAR
+	int "Serial parse SIGKILL characters"
+	default 3 if SERIAL_CONSOLE
+	default 4 if !SERIAL_CONSOLE
+	depends on SIG_SIGKILL
+	---help---
+		Use ASCII 3 (Ctrl-c) or 4 (ctrl-d) inputs to determine whether to
+		send a SIGKILL event.  Other charcters may also be selected.
+
+		REVISIT:  Traditionally Ctrl-C would generate SIGINT.  Ctrl-D is the
+		End-of-File character that should close the stream.
+
 menuconfig 16550_UART
 	bool "16550 UART Chip support"
 	default n

drivers/serial/serial.c

@@ -1,7 +1,7 @@
 /************************************************************************************
  * drivers/serial/serial.c
  *
- *   Copyright (C) 2007-2009, 2011-2013, 2016-2017 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011-2013, 2016-2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -703,14 +703,7 @@ static int uart_close(FAR struct file *filep)
    * a thread currently blocking on any of them.
    */
 
-  nxsem_reset(&dev->xmitsem,  0);
+  uart_reset_sem(dev);
-  nxsem_reset(&dev->recvsem,  0);
-  nxsem_reset(&dev->xmit.sem, 1);
-  nxsem_reset(&dev->recv.sem, 1);
-#ifndef CONFIG_DISABLE_POLL
-  nxsem_reset(&dev->pollsem,  1);
-#endif
-
   uart_givesem(&dev->closesem);
   return OK;
 }
@@ -1376,6 +1369,25 @@ static int uart_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
             }
             break;
 #endif
+
+#ifdef CONFIG_SERIAL_SIGKILL_CHAR
+          case TIOCSCTTY:
+            {
+              /* REVISIT:  This only applies to console devices (TTYs).  In
+               * reality, this feature should be controlled by TERMIOS ISIG
+               * c_lflag setting.
+               */
+
+             if (dev->isconsole)
+               {
+                  /* Save the PID of the recipient of the SIGKILL signal. */
+
+                  dev->pid = (pid_t)arg;
+                  DEBUGASSERT((unsigned long)dev->pid = arg);
+               }
+            }
+            break;
+#endif
         }
     }
 
@@ -1584,6 +1596,12 @@ errout:
 
 int uart_register(FAR const char *path, FAR uart_dev_t *dev)
 {
+#ifdef CONFIG_SERIAL_SIGKILL_CHAR
+  /* Initialize  of the task that will receive SIGKILL signals. */
+
+  dev->pid = -1;
+#endif
+
   /* Initialize semaphores */
 
   nxsem_init(&dev->xmit.sem, 0, 1);
@@ -1728,3 +1746,23 @@ void uart_connected(FAR uart_dev_t *dev, bool connected)
   leave_critical_section(flags);
 }
 #endif
+
+/************************************************************************************
+ * Name: uart_reset_sem
+ *
+ * Description:
+ *   This function is called when need reset uart semphore, this may used in kill one
+ *   process, but this process was reading/writing with the semphore.
+ *
+ ************************************************************************************/
+
+void uart_reset_sem(FAR uart_dev_t *dev)
+{
+  nxsem_reset(&dev->xmitsem,  0);
+  nxsem_reset(&dev->recvsem,  0);
+  nxsem_reset(&dev->xmit.sem, 1);
+  nxsem_reset(&dev->recv.sem, 1);
+#ifndef CONFIG_DISABLE_POLL
+  nxsem_reset(&dev->pollsem,  1);
+#endif
+}

drivers/serial/serial_dma.c

@@ -1,7 +1,7 @@
 /************************************************************************************
  * drivers/serial/serial_dma.c
  *
- *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author:  Max Neklyudov <macscomp@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -48,6 +48,67 @@
 
 #ifdef CONFIG_SERIAL_DMA
 
+/************************************************************************************
+ * Private Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: uart_check_sigkill
+ *
+ * Description:
+ *   Check if the SIGKILL character is in the contiguous Rx DMA buffer region.
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SIG_SIGKILL
+static bool uart_check_sigkill(const char *buf, size_t size)
+{
+  size_t i;
+
+  for (i = 0; i < size; i++)
+    {
+      if (buf[i] == CONFIG_SERIAL_SIGKILL_CHAR)
+        {
+          return true;
+        }
+    }
+
+  return false;
+}
+#endif
+
+/************************************************************************************
+ * Name: uart_recvchars_sigkill
+ *
+ * Description:
+ *   Check if the SIGKILL character is anywhere in the newly received DMA buffer.
+ *
+ *   REVISIT:  We must also remove the SIGKILL character from the Rx buffer.  It
+ *   should not be read as normal data by the caller.
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SIG_SIGKILL
+static bool uart_recvchars_sigkill(FAR uart_dev_t *dev)
+{
+  FAR struct uart_dmaxfer_s *xfer = &dev->dmarx;
+
+  if (xfer->nbytes <= xfer->length)
+    {
+      return uart_check_sigkill(xfer->buffer, xfer->nbytes);
+    }
+  else
+    {
+      if (uart_check_sigkill(xfer->buffer, xfer->length))
+        {
+          return true;
+        }
+
+      return uart_check_sigkill(xfer->nbuffer, xfer->nbytes - xfer->length);
+    }
+}
+#endif
+
 /************************************************************************************
  * Public Functions
  ************************************************************************************/
@@ -250,6 +311,16 @@ void uart_recvchars_done(FAR uart_dev_t *dev)
   FAR struct uart_dmaxfer_s *xfer = &dev->dmarx;
   FAR struct uart_buffer_s *rxbuf = &dev->recv;
   size_t nbytes = xfer->nbytes;
+#ifdef CONFIG_SIG_SIGKILL
+  bool needkill = false;
+
+  /* Check if the SIGKILL character is anywhere in the newly received DMA buffer. */
+
+  if (dev->pid >= 0 && uart_recvchars_sigkill(dev))
+    {
+      needkill = true;
+    }
+#endif
 
   /* Move head for nbytes. */
 
@@ -265,6 +336,16 @@ void uart_recvchars_done(FAR uart_dev_t *dev)
     {
       uart_datareceived(dev);
     }
+
+#ifdef CONFIG_SIG_SIGKILL
+  /* Send the SIGKILL signal if needed */
+
+  if (needkill)
+    {
+      kill(dev->pid, SIGKILL);
+      uart_reset_sem(dev);
+    }
+#endif
 }
 
 #endif /* CONFIG_SERIAL_DMA */

drivers/serial/serial_io.c

@@ -1,7 +1,7 @@
 /************************************************************************************
  * drivers/serial/serial_io.c
  *
- *   Copyright (C) 2007-2009, 2011, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -122,6 +122,9 @@ void uart_recvchars(FAR uart_dev_t *dev)
   FAR struct uart_buffer_s *rxbuf = &dev->recv;
 #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
   unsigned int watermark;
+#endif
+#ifdef CONFIG_SIG_SIGKILL
+  bool needkill = false;
 #endif
   unsigned int status;
   int nexthead = rxbuf->head + 1;
@@ -194,8 +197,24 @@ void uart_recvchars(FAR uart_dev_t *dev)
 #endif
 #endif
 
+      /* Get this next character from the hardware */
+
       ch = uart_receive(dev, &status);
 
+#ifdef CONFIG_SIG_SIGKILL
+      /* Is this the special character that will generate the SIGKILL signal? */
+
+      if (dev->pid >= 0 && ch == CONFIG_SERIAL_SIGKILL_CHAR)
+        {
+          /* Yes.. not the the kill is needed and do not put the character into
+           * the Rx buffer.  It should not be read as normal data.
+           */
+
+          needkill = true;
+        }
+      else
+#endif
+
       /* If the RX buffer becomes full, then the serial data is discarded.  This is
        * necessary because on most serial hardware, you must read the data in order
        * to clear the RX interrupt. An option on some hardware might be to simply
@@ -229,4 +248,14 @@ void uart_recvchars(FAR uart_dev_t *dev)
     {
       uart_datareceived(dev);
     }
+
+#ifdef CONFIG_SIG_SIGKILL
+  /* Send the SIGKILL signal if needed */
+
+  if (needkill)
+    {
+      kill(dev->pid, SIGKILL);
+      uart_reset_sem(dev);
+    }
+#endif
 }

include/nuttx/serial/serial.h

@@ -1,7 +1,7 @@
 /************************************************************************************
  * include/nuttx/serial/serial.h
  *
- *   Copyright (C) 2007-2008, 2012-2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2008, 2012-2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -288,6 +288,10 @@ struct uart_dev_s
   tcflag_t             tc_lflag;     /* Local modes */
 #endif
 
+#ifdef CONFIG_SERIAL_SIGKILL_CHAR
+  pid_t                 pid;         /* Thread PID to receive SIGKILL signals (-1 if none) */
+#endif
+
   /* Semaphores */
 
   sem_t                closesem;     /* Locks out new open while close is in progress */
@@ -481,6 +485,17 @@ void uart_recvchars_dma(FAR uart_dev_t *dev);
 void uart_recvchars_done(FAR uart_dev_t *dev);
 #endif
 
+/************************************************************************************
+ * Name: uart_reset_sem
+ *
+ * Description:
+ *   This function is called when need reset uart semphore, this may used in kill one
+ *   process, but this process was reading/writing with the semphore.
+ *
+ ************************************************************************************/
+
+void uart_reset_sem(FAR uart_dev_t *dev);
+
 #undef EXTERN
 #if defined(__cplusplus)
 }

include/signal.h

@@ -1,7 +1,7 @@
 /********************************************************************************
  * include/signal.h
  *
- *   Copyright (C) 2007-2009, 2011, 2013-2017 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2013-2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -169,6 +169,14 @@
 #  endif
 #endif
 
+#ifdef CONFIG_SIG_SIGKILL
+#  ifndef CONFIG_SIG_KILL
+#    define SIGKILL     9  /* Sent when ctrl-c event (vs. standard SIGINT)  */
+#  else
+#    define SIGKILL     CONFIG_SIG_KILL
+#  endif
+#endif
+
 /* The following are non-standard signal definitions */
 
 #ifndef CONFIG_DISABLE_PTHREAD

sched/Kconfig

@@ -1184,6 +1184,15 @@ config SIG_EVTHREAD
 		different mechanism would need to be development to support this
 		feature on the PROTECTED or KERNEL build.
 
+config SIG_SIGKILL
+	bool "Support SIGKILL"
+	default n
+	depends on !DISABLE_SIGNALS
+	---help---
+		Whether support Ctrl-c/x event, or kill -9 cmd.
+
+		NOTE: SIGINT is normally sent by Ctrl-C in other systems.
+
 menu "Signal Numbers"
 	depends on !DISABLE_SIGNALS
 
@@ -1223,6 +1232,16 @@ config SIG_POLL
 		The SIGPOLL signal is sent to a process when an asynchronous I/O
 		event occurs (meaning it has been polled).  Default: 5
 
+config SIG_KILL
+	int "SIGKILL"
+	default 9
+	depends on SIG_SIGKILL
+	---help---
+		The SIGKILL signal is sent to a process when Ctrl-c/x event,
+		or cmd kill -9 xx happened.
+
+		NOTE: SIGINT is normally sent by Ctrl-C in other systems.
+
 config SIG_SIGCONDTIMEDOUT
 	int "SIGCONDTIMEDOUT"
 	default 16

sched/task/task_start.c

@@ -42,22 +42,85 @@
 #include <stdlib.h>
 #include <sched.h>
 #include <debug.h>
+#include <string.h>
 
 #include <nuttx/arch.h>
 #include <nuttx/sched.h>
 
+#include "group/group.h"
 #include "sched/sched.h"
 #include "task/task.h"
 
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
+
 /* This is an artificial limit to detect error conditions where an argv[]
  * list is not properly terminated.
  */
 
 #define MAX_START_ARGS 256
 
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: task_sigkill_action
+ *
+ * Description:
+ *   This is the default action for the SIGKILL signal.
+ *
+ *   REVISIT:  I think there is an issue here in the PROTECTED and KERNEL
+ *   build modes.  In those cases, the signal handler will go through a
+ *   trampoline that drops to user mode for execution of the signal handler.
+ *   In the PROTECTED mode, this will forward the call to here in user mode
+ *   which will result in a crash.  The behavior in KERNEL mode in
+ *   indeterminate.
+ *
+ * Input Parameters:
+ *   Standard signal handler parameters
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SIG_SIGKILL
+static void task_sigkill_action(int signo, siginfo_t *siginfo, void *arg)
+{
+#ifdef HAVE_GROUP_MEMBERS
+  FAR struct task_tcb_s *tcb = (FAR struct task_tcb_s *)this_task();
+  group_killchildren(tcb);
+#endif
+  exit(EXIT_FAILURE);
+}
+
+/****************************************************************************
+ * Name: task_setup_sigkill
+ *
+ * Description:
+ *   Setup the default action for the SIGKILL signal
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline void task_setup_sigkill(void)
+{
+  struct sigaction sa;
+
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = task_sigkill_action;
+  sa.sa_flags     = SA_SIGINFO;
+  sigaction(SIGKILL, &sa, NULL);
+}
+#endif
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -86,6 +149,12 @@ void task_start(void)
 
   DEBUGASSERT((tcb->cmn.flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD);
 
+  /* Set up default signal actions */
+
+#ifdef CONFIG_SIG_SIGKILL
+  task_setup_sigkill();
+#endif
+
   /* Execute the start hook if one has been registered */
 
 #ifdef CONFIG_SCHED_STARTHOOK