Add support for calling to and returning from signal handlers in in user-mode threads

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5750 42af7a65-404d-4744-a932-0658087f49c3

27 files changed, 679 insertions, 88 deletions

diff --git a/nuttx/arch/arm/include/armv6-m/irq.h b/nuttx/arch/arm/include/armv6-m/irq.h
index db5c82913..75aed8ff1 100644
--- a/nuttx/arch/arm/include/armv6-m/irq.h
+++ b/nuttx/arch/arm/include/armv6-m/irq.h
@@ -161,6 +161,14 @@ struct xcptcontext
   uint32_t saved_pc;
   uint32_t saved_basepri;
   uint32_t saved_xpsr;
+
+# ifdef CONFIG_NUTTX_KERNEL
+  /* This is the saved address to use when returning from a user-space
+   * signal handler.
+   */
+
+  uint32_t sigreturn;
+# endif
 #endif
 
 #ifdef CONFIG_NUTTX_KERNEL
diff --git a/nuttx/arch/arm/include/armv6-m/syscall.h b/nuttx/arch/arm/include/armv6-m/syscall.h
index f92dea7e8..9548ae494 100644
--- a/nuttx/arch/arm/include/armv6-m/syscall.h
+++ b/nuttx/arch/arm/include/armv6-m/syscall.h
@@ -54,8 +54,22 @@
  * Pro-processor Definitions
  ****************************************************************************/
 
+/* This is the value used as the argument to the SVC instruction.  It is not
+ * used.
+ */
+
 #define SYS_syscall 0x00
 
+/* The SYS_signal_handler_return is executed here... its value is not always
+ * available in this context and so is assumed to be 7.
+ */
+
+#ifndef SYS_signal_handler_return
+#  define SYS_signal_handler_return (7)
+#elif SYS_signal_handler_return != 7
+#  error "SYS_signal_handler_return was assumed to be 7"
+#endif
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -218,6 +232,18 @@ static inline uintptr_t sys_call6(unsigned int nbr, uintptr_t parm1,
   return reg0;
 }
 
+/* This inline function is used by user-space code in order to return from
+ * a signal handler.
+ */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
+static inline void signal_handler_return(void) noreturn_function;
+static inline void signal_handler_return(void)
+{
+  sys_call0(SYS_signal_handler_return);
+}
+#endif
+
 /****************************************************************************
  * Public Variables
  ****************************************************************************/
diff --git a/nuttx/arch/arm/include/armv7-m/irq.h b/nuttx/arch/arm/include/armv7-m/irq.h
index 7556d0747..afeebdb4f 100644
--- a/nuttx/arch/arm/include/armv7-m/irq.h
+++ b/nuttx/arch/arm/include/armv7-m/irq.h
@@ -124,6 +124,14 @@ struct xcptcontext
   uint32_t saved_primask;
 #endif
   uint32_t saved_xpsr;
+
+# ifdef CONFIG_NUTTX_KERNEL
+  /* This is the saved address to use when returning from a user-space
+   * signal handler.
+   */
+
+  uint32_t sigreturn;
+# endif
 #endif
 
 #ifdef CONFIG_NUTTX_KERNEL
diff --git a/nuttx/arch/arm/include/armv7-m/syscall.h b/nuttx/arch/arm/include/armv7-m/syscall.h
index 4278c3a36..91220f359 100644
--- a/nuttx/arch/arm/include/armv7-m/syscall.h
+++ b/nuttx/arch/arm/include/armv7-m/syscall.h
@@ -54,8 +54,22 @@
  * Pro-processor Definitions
  ****************************************************************************/
 
+/* This is the value used as the argument to the SVC instruction.  It is not
+ * used.
+ */
+
 #define SYS_syscall 0x00
 
+/* The SYS_signal_handler_return is executed here... its value is not always
+ * available in this context and so is assumed to be 7.
+ */
+
+#ifndef SYS_signal_handler_return
+#  define SYS_signal_handler_return (7)
+#elif SYS_signal_handler_return != 7
+#  error "SYS_signal_handler_return was assumed to be 7"
+#endif
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -218,6 +232,18 @@ static inline uintptr_t sys_call6(unsigned int nbr, uintptr_t parm1,
   return reg0;
 }
 
+/* This inline function is used by user-space code in order to return from
+ * a signal handler.
+ */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
+static inline void signal_handler_return(void) noreturn_function;
+static inline void signal_handler_return(void)
+{
+  sys_call0(SYS_signal_handler_return);
+}
+#endif
+
 /****************************************************************************
  * Public Variables
  ****************************************************************************/
diff --git a/nuttx/arch/arm/src/armv6-m/svcall.h b/nuttx/arch/arm/src/armv6-m/svcall.h
index c7f2013fc..daa70a0c0 100644
--- a/nuttx/arch/arm/src/armv6-m/svcall.h
+++ b/nuttx/arch/arm/src/armv6-m/svcall.h
@@ -57,9 +57,9 @@
 
 #ifdef CONFIG_NUTTX_KERNEL
 #  ifndef CONFIG_SYS_RESERVED
-#    error "CONFIG_SYS_RESERVED must be defined to the value 6"
-#  elif CONFIG_SYS_RESERVED != 6
-#    error "CONFIG_SYS_RESERVED must have the value 6"
+#    error "CONFIG_SYS_RESERVED must be defined to have the value 8"
+#  elif CONFIG_SYS_RESERVED != 8
+#    error "CONFIG_SYS_RESERVED must have the value 8"
 #  endif
 #endif
 
@@ -70,21 +70,21 @@
  * int up_saveusercontext(uint32_t *saveregs);
  */
 
-#define SYS_save_context    (0)
+#define SYS_save_context          (0)
 
 /* SYS call 1:
  *
  * void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
  */
 
-#define SYS_restore_context (1)
+#define SYS_restore_context       (1)
 
 /* SYS call 2:
  *
  * void up_switchcontext(uint32_t *saveregs, uint32_t *restoreregs);
  */
 
-#define SYS_switch_context  (2)
+#define SYS_switch_context        (2)
 
 #ifdef CONFIG_NUTTX_KERNEL
 /* SYS call 3:
@@ -92,21 +92,38 @@
  * void up_syscall_return(void);
  */
 
-#define SYS_syscall_return  (3)
+#define SYS_syscall_return        (3)
 
 /* SYS call 4:
  *
- * void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_function;
+ * void up_task_start(main_t taskentry, int argc, FAR char *argv[])
+ *        noreturn_function;
  */
 
-#define SYS_task_start      (4)
+#define SYS_task_start            (4)
 
 /* SYS call 5:
  *
- * void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg) noreturn_function
+ * void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg)
+ *        noreturn_function
  */
 
-#define SYS_pthread_start   (5)
+#define SYS_pthread_start         (5)
+
+/* SYS call 6:
+ *
+ * void signal_handler(_sa_sigaction_t sighand, int signo, FAR siginfo_t *info,
+ *                     FAR void *ucontext);
+ */
+
+#define SYS_signal_handler        (6)
+
+/* SYS call 7:
+ *
+ * void signal_handler_return(void);
+ */
+
+#define SYS_signal_handler_return (7)
 #endif
 
 /************************************************************************************
diff --git a/nuttx/arch/arm/src/armv6-m/up_sigdeliver.c b/nuttx/arch/arm/src/armv6-m/up_sigdeliver.c
index ca60b68c5..83a064e12 100644
--- a/nuttx/arch/arm/src/armv6-m/up_sigdeliver.c
+++ b/nuttx/arch/arm/src/armv6-m/up_sigdeliver.c
@@ -122,7 +122,7 @@ void up_sigdeliver(void)
 
   irqrestore((uint8_t)regs[REG_BASEPRI]);
 
-  /* Deliver the signals */
+  /* Deliver the signal */
 
   sigdeliver(rtcb);
 
diff --git a/nuttx/arch/arm/src/armv6-m/up_svcall.c b/nuttx/arch/arm/src/armv6-m/up_svcall.c
index ac99cabe0..745800532 100644
--- a/nuttx/arch/arm/src/armv6-m/up_svcall.c
+++ b/nuttx/arch/arm/src/armv6-m/up_svcall.c
@@ -344,6 +344,78 @@ int up_svcall(int irq, FAR void *context)
         break;
 #endif
 
+      /* R0=SYS_signal_handler:  This a user signal handler callback
+       *
+       * void signal_handler(_sa_sigaction_t sighand, int signo,
+       *                     FAR siginfo_t *info, FAR void *ucontext);
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   R0 = SYS_signal_handler
+       *   R1 = sighand
+       *   R2 = signo
+       *   R3 = info
+       *        ucontext (on the stack)
+       */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
+      case SYS_signal_handler:
+        {
+          struct tcb_s *rtcb   = sched_self();
+
+          /* Remember the caller's return address */
+
+          DEBUGASSERT(rtcb->xcp.sigreturn == 0);
+          rtcb->xcp.sigreturn  = regs[REG_PC];
+
+          /* Set up to return to the user-space pthread start-up function in
+           * unprivileged mode.
+           */
+
+          regs[REG_PC]         = (uint32_t)USERSPACE->signal_handler;
+          regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR;
+
+          /* Change the parameter ordering to match the expectation of struct
+           * userpace_s signal_handler.
+           */
+
+          regs[REG_R0]         = regs[REG_R1]; /* sighand */
+          regs[REG_R1]         = regs[REG_R2]; /* signal */
+          regs[REG_R2]         = regs[REG_R3]; /* info */
+
+          /* The last parameter, arg, is trickier.  The arg parameter will
+           * reside at an offset of 4 from the stack pointer.
+           */
+
+          regs[REG_R3]         = *(uint32_t*)(regs[REG_SP+4]);
+        }
+        break;
+#endif
+
+      /* R0=SYS_signal_handler_return:  This a user signal handler callback
+       *
+       *   void signal_handler_return(void);
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   R0 = SYS_signal_handler_return
+       */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
+      case SYS_signal_handler_return:
+        {
+          struct tcb_s *rtcb   = sched_self();
+
+          /* Set up to return to the kernel-mode signal dispatching logic. */
+
+          DEBUGASSERT(rtcb->xcp.sigreturn != 0);
+
+          regs[REG_PC]         = rtcb->xcp.sigreturn;
+          regs[REG_EXC_RETURN] = EXC_RETURN_PRIVTHR;
+        }
+        break;
+#endif
+
       /* This is not an architecture-specific system call.  If NuttX is built
        * as a standalone kernel with a system call interface, then all of the
        * additional system calls must be handled as in the default case.
@@ -356,7 +428,7 @@ int up_svcall(int irq, FAR void *context)
 
           /* Verify that the SYS call number is within range */
 
-          DEBUGASSERT(cmd < SYS_maxsyscall);
+          DEBUGASSERT(cmd >= CONFIG_SYS_RESERVED && cmd < SYS_maxsyscall);
 
           /* Make sure that there is a no saved syscall return address.  We
            * cannot yet handle nested system calls.
diff --git a/nuttx/arch/arm/src/armv7-m/svcall.h b/nuttx/arch/arm/src/armv7-m/svcall.h
index 333dfb6d0..2c4735335 100644
--- a/nuttx/arch/arm/src/armv7-m/svcall.h
+++ b/nuttx/arch/arm/src/armv7-m/svcall.h
@@ -57,9 +57,9 @@
 
 #ifdef CONFIG_NUTTX_KERNEL
 #  ifndef CONFIG_SYS_RESERVED
-#    error "CONFIG_SYS_RESERVED must be defined to the value 6"
-#  elif CONFIG_SYS_RESERVED != 6
-#    error "CONFIG_SYS_RESERVED must have the value 6"
+#    error "CONFIG_SYS_RESERVED must be defined to have the value 8"
+#  elif CONFIG_SYS_RESERVED != 8
+#    error "CONFIG_SYS_RESERVED must have the value 8"
 #  endif
 #endif
 
@@ -70,21 +70,21 @@
  * int up_saveusercontext(uint32_t *saveregs);
  */
 
-#define SYS_save_context    (0)
+#define SYS_save_context          (0)
 
 /* SYS call 1:
  *
  * void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
  */
 
-#define SYS_restore_context (1)
+#define SYS_restore_context       (1)
 
 /* SYS call 2:
  *
  * void up_switchcontext(uint32_t *saveregs, uint32_t *restoreregs);
  */
 
-#define SYS_switch_context  (2)
+#define SYS_switch_context        (2)
 
 #ifdef CONFIG_NUTTX_KERNEL
 /* SYS call 3:
@@ -92,21 +92,38 @@
  * void up_syscall_return(void);
  */
 
-#define SYS_syscall_return  (3)
+#define SYS_syscall_return        (3)
 
 /* SYS call 4:
  *
- * void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_function;
+ * void up_task_start(main_t taskentry, int argc, FAR char *argv[])
+ *        noreturn_function;
  */
 
-#define SYS_task_start      (4)
+#define SYS_task_start            (4)
 
 /* SYS call 5:
  *
- * void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg) noreturn_function
+ * void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg)
+ *        noreturn_function
  */
 
-#define SYS_pthread_start   (5)
+#define SYS_pthread_start         (5)
+
+/* SYS call 6:
+ *
+ * void signal_handler(_sa_sigaction_t sighand, int signo, FAR siginfo_t *info,
+ *                     FAR void *ucontext);
+ */
+
+#define SYS_signal_handler        (6)
+
+/* SYS call 7:
+ *
+ * void signal_handler_return(void);
+ */
+
+#define SYS_signal_handler_return (7)
 #endif
 
 /************************************************************************************
diff --git a/nuttx/arch/arm/src/armv7-m/up_sigdeliver.c b/nuttx/arch/arm/src/armv7-m/up_sigdeliver.c
index 2e75d254a..e9c7a9523 100644
--- a/nuttx/arch/arm/src/armv7-m/up_sigdeliver.c
+++ b/nuttx/arch/arm/src/armv7-m/up_sigdeliver.c
@@ -125,7 +125,7 @@ void up_sigdeliver(void)
   irqrestore((uint16_t)regs[REG_PRIMASK]);
 #endif
 
-  /* Deliver the signals */
+  /* Deliver the signal */
 
   sigdeliver(rtcb);
 
diff --git a/nuttx/arch/arm/src/armv7-m/up_svcall.c b/nuttx/arch/arm/src/armv7-m/up_svcall.c
index 1a153dead..ab313671c 100644
--- a/nuttx/arch/arm/src/armv7-m/up_svcall.c
+++ b/nuttx/arch/arm/src/armv7-m/up_svcall.c
@@ -348,6 +348,78 @@ int up_svcall(int irq, FAR void *context)
         break;
 #endif
 
+      /* R0=SYS_signal_handler:  This a user signal handler callback
+       *
+       * void signal_handler(_sa_sigaction_t sighand, int signo,
+       *                     FAR siginfo_t *info, FAR void *ucontext);
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   R0 = SYS_signal_handler
+       *   R1 = sighand
+       *   R2 = signo
+       *   R3 = info
+       *        ucontext (on the stack)
+       */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
+      case SYS_signal_handler:
+        {
+          struct tcb_s *rtcb   = sched_self();
+
+          /* Remember the caller's return address */
+
+          DEBUGASSERT(rtcb->xcp.sigreturn == 0);
+          rtcb->xcp.sigreturn  = regs[REG_PC];
+
+          /* Set up to return to the user-space pthread start-up function in
+           * unprivileged mode.
+           */
+
+          regs[REG_PC]         = (uint32_t)USERSPACE->signal_handler;
+          regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR;
+
+          /* Change the parameter ordering to match the expectation of struct
+           * userpace_s signal_handler.
+           */
+
+          regs[REG_R0]         = regs[REG_R1]; /* sighand */
+          regs[REG_R1]         = regs[REG_R2]; /* signal */
+          regs[REG_R2]         = regs[REG_R3]; /* info */
+
+          /* The last parameter, arg, is trickier.  The arg parameter will
+           * reside at an offset of 4 from the stack pointer.
+           */
+
+          regs[REG_R3]         = *(uint32_t*)(regs[REG_SP+4]);
+        }
+        break;
+#endif
+
+      /* R0=SYS_signal_handler_return:  This a user signal handler callback
+       *
+       *   void signal_handler_return(void);
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   R0 = SYS_signal_handler_return
+       */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
+      case SYS_signal_handler_return:
+        {
+          struct tcb_s *rtcb   = sched_self();
+
+          /* Set up to return to the kernel-mode signal dispatching logic. */
+
+          DEBUGASSERT(rtcb->xcp.sigreturn != 0);
+
+          regs[REG_PC]         = rtcb->xcp.sigreturn;
+          regs[REG_EXC_RETURN] = EXC_RETURN_PRIVTHR;
+        }
+        break;
+#endif
+
       /* This is not an architecture-specific system call.  If NuttX is built
        * as a standalone kernel with a system call interface, then all of the
        * additional system calls must be handled as in the default case.
@@ -360,7 +432,7 @@ int up_svcall(int irq, FAR void *context)
 
           /* Verify that the SYS call number is within range */
 
-          DEBUGASSERT(cmd < SYS_maxsyscall);
+          DEBUGASSERT(cmd >= CONFIG_SYS_RESERVED && cmd < SYS_maxsyscall);
 
           /* Make sure that there is a no saved syscall return address.  We
            * cannot yet handle nested system calls.
diff --git a/nuttx/arch/arm/src/common/up_signal_handler.c b/nuttx/arch/arm/src/common/up_signal_handler.c
new file mode 100644
index 000000000..34407885e
--- /dev/null
+++ b/nuttx/arch/arm/src/common/up_signal_handler.c
@@ -0,0 +1,100 @@
+/****************************************************************************
+ * arch/arm/src/common/up_task_start.c
+ *
+ *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/arch.h>
+
+#include "svcall.h"
+#include "up_internal.h"
+
+#if defined(CONFIG_NUTTX_KERNEL) && defined(__KERNEL__) && !defined(CONFIG_DISABLE_SIGNALS)
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: up_signal_handler
+ *
+ * Description:
+ *   In this kernel mode build, this function will be called to execute a
+ *   a signal handler in user-space.  When the signal is delivered, a
+ *   kernel-mode stub will first run to perform some housekeeping functions.
+ *   This kernel-mode stub will then be called transfer control to the user
+ *   mode signal handler by calling this function.
+ *
+ *   Normally the a user-mode signalling handling stub will also execute
+ *   before the ultimate signal handler is called.  See
+ *   libc/signal/signal_handler.c  This function is the user-space, signal
+ *   handler trampoline function.  It is called from up_signal_handler() in
+ *   user-mode.
+ *
+ * Inputs:
+ *   sighand - The address user-space signal handling function
+ *   signo, info, and ucontext - Standard arguments to be passed to the
+ *     signal handling function.
+ *
+ * Return:
+ *   None.  This function does not return in the normal sense.  It returns
+ *   via signal_handler_return (below)
+ *
+ ****************************************************************************/
+
+void up_signal_handler(_sa_sigaction_t sighand, int signo,
+                       FAR siginfo_t *info, FAR void *ucontext)
+{
+  /* Let sys_call4() do all of the work */
+
+  sys_call4(SYS_signal_handler, (uintptr_t)sighand, (uintptr_t)signo,
+            (uintptr_t)info, (uintptr_t)ucontext);
+}
+
+#endif /* CONFIG_NUTTX_KERNEL && __KERNEL__ && !CONFIG_DISABLE_SIGNALS */
diff --git a/nuttx/arch/arm/src/common/up_task_start.c b/nuttx/arch/arm/src/common/up_task_start.c
index c006f9595..0a3f3c4a4 100644
--- a/nuttx/arch/arm/src/common/up_task_start.c
+++ b/nuttx/arch/arm/src/common/up_task_start.c
@@ -90,7 +90,8 @@ void up_task_start(main_t taskentry, int argc, FAR char *argv[])
 {
   /* Let sys_call3() do all of the work */
 
-  sys_call3(SYS_task_start, (uintptr_t)taskentry, (uintptr_t)argc, (uintptr_t)argv);
+  sys_call3(SYS_task_start, (uintptr_t)taskentry, (uintptr_t)argc,
+            (uintptr_t)argv);
 }
 
 #endif /* CONFIG_NUTTX_KERNEL */
diff --git a/nuttx/arch/arm/src/lpc17xx/Make.defs b/nuttx/arch/arm/src/lpc17xx/Make.defs
index e6d007902..2bedbf5b3 100644
--- a/nuttx/arch/arm/src/lpc17xx/Make.defs
+++ b/nuttx/arch/arm/src/lpc17xx/Make.defs
@@ -65,6 +65,9 @@ endif
 
 ifeq ($(CONFIG_NUTTX_KERNEL),y)
 CMN_CSRCS += up_mpu.c up_task_start.c up_pthread_start.c
+ifneq ($(CONFIG_DISABLE_SIGNALS),y)
+CMN_CSRCS += up_signal_handler.c
+endif
 endif
 
 ifeq ($(CONFIG_NET),y)
diff --git a/nuttx/arch/arm/src/sam3u/Make.defs b/nuttx/arch/arm/src/sam3u/Make.defs
index a2047a78a..14cc68d49 100644
--- a/nuttx/arch/arm/src/sam3u/Make.defs
+++ b/nuttx/arch/arm/src/sam3u/Make.defs
@@ -57,6 +57,9 @@ endif
 
 ifeq ($(CONFIG_NUTTX_KERNEL),y)
 CMN_CSRCS += up_mpu.c up_task_start.c up_pthread_start.c
+ifneq ($(CONFIG_DISABLE_SIGNALS),y)
+CMN_CSRCS += up_signal_handler.c
+endif
 endif
 
 ifeq ($(CONFIG_ELF),y)
diff --git a/nuttx/configs/open1788/kernel/up_userspace.c b/nuttx/configs/open1788/kernel/up_userspace.c
index 3947af1cd..2263bc3f5 100644
--- a/nuttx/configs/open1788/kernel/up_userspace.c
+++ b/nuttx/configs/open1788/kernel/up_userspace.c
@@ -44,7 +44,6 @@
 #include <nuttx/userspace.h>
 #include <nuttx/wqueue.h>
 #include <nuttx/mm.h>
-#include <nuttx/sched.h>
 
 #if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
 
@@ -102,13 +101,19 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
   .us_bssstart      = (uintptr_t)&_sbss,
   .us_bssend        = (uintptr_t)&_ebss,
 
-  /* Task/thread startup stubs */
+  /* Task/thread startup routines */
 
   .task_startup     = task_startup,
 #ifndef CONFIG_DISABLE_PTHREAD
   .pthread_startup  = pthread_startup,
 #endif
 
+  /* Signal handler trampoline */
+
+#ifndef CONFIG_DISABLE_SIGNALS
+  .signal_handler   = signal_handler,
+#endif
+
   /* Memory manager entry points (declared in include/nuttx/mm.h) */
 
   .mm_initialize    = umm_initialize,
diff --git a/nuttx/configs/open1788/knsh/defconfig b/nuttx/configs/open1788/knsh/defconfig
index b8d36e6fd..addfd82ad 100755
--- a/nuttx/configs/open1788/knsh/defconfig
+++ b/nuttx/configs/open1788/knsh/defconfig
@@ -344,7 +344,7 @@ CONFIG_IDLETHREAD_STACKSIZE=1024
 CONFIG_USERMAIN_STACKSIZE=2048
 CONFIG_PTHREAD_STACK_MIN=256
 CONFIG_PTHREAD_STACK_DEFAULT=2048
-CONFIG_SYS_RESERVED=6
+CONFIG_SYS_RESERVED=8
 
 #
 # Device Drivers
diff --git a/nuttx/configs/sam3u-ek/kernel/up_userspace.c b/nuttx/configs/sam3u-ek/kernel/up_userspace.c
index ee61d1b69..484cdc2d0 100644
--- a/nuttx/configs/sam3u-ek/kernel/up_userspace.c
+++ b/nuttx/configs/sam3u-ek/kernel/up_userspace.c
@@ -101,13 +101,19 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
   .us_bssstart      = (uintptr_t)&_sbss,
   .us_bssend        = (uintptr_t)&_ebss,
 
-  /* Task/thread startup stubs */
+  /* Task/thread startup routines */
 
   .task_startup     = task_startup,
 #ifndef CONFIG_DISABLE_PTHREAD
   .pthread_startup  = pthread_startup,
 #endif
 
+  /* Signal handler trampoline */
+
+#ifndef CONFIG_DISABLE_SIGNALS
+  .signal_handler   = signal_handler,
+#endif
+
   /* Memory manager entry points (declared in include/nuttx/mm.h) */
 
   .mm_initialize    = umm_initialize,
diff --git a/nuttx/configs/sam3u-ek/knsh/defconfig b/nuttx/configs/sam3u-ek/knsh/defconfig
index 9bdb33004..71c646083 100755
--- a/nuttx/configs/sam3u-ek/knsh/defconfig
+++ b/nuttx/configs/sam3u-ek/knsh/defconfig
@@ -249,7 +249,7 @@ CONFIG_IDLETHREAD_STACKSIZE=1024
 CONFIG_USERMAIN_STACKSIZE=2048
 CONFIG_PTHREAD_STACK_MIN=256
 CONFIG_PTHREAD_STACK_DEFAULT=2048
-CONFIG_SYS_RESERVED=6
+CONFIG_SYS_RESERVED=8
 
 #
 # Device Drivers
diff --git a/nuttx/include/nuttx/arch.h b/nuttx/include/nuttx/arch.h
index ed461b50d..afd385ea6 100644
--- a/nuttx/include/nuttx/arch.h
+++ b/nuttx/include/nuttx/arch.h
@@ -373,7 +373,7 @@ void up_schedule_sigaction(FAR struct tcb_s *tcb, sig_deliver_t sigdeliver);
  *   task in user-space.  When the task is first started, a kernel-mode
  *   stub will first run to perform some housekeeping functions.  This
  *   kernel-mode stub will then be called transfer control to the user-mode
- *   task.
+ *   task by calling this function.
  *
  *   Normally the a user-mode start-up stub will also execute before the
  *   task actually starts.  See libc/sched/task_startup.c
@@ -391,7 +391,8 @@ void up_schedule_sigaction(FAR struct tcb_s *tcb, sig_deliver_t sigdeliver);
  ****************************************************************************/
 
 #if defined(CONFIG_NUTTX_KERNEL) && defined(__KERNEL__)
-void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_function;
+void up_task_start(main_t taskentry, int argc, FAR char *argv[])
+       noreturn_function;
 #endif
 
 /****************************************************************************
@@ -402,7 +403,7 @@ void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_functi
  *   pthread in user-space.  When the pthread is first started, a kernel-mode
  *   stub will first run to perform some housekeeping functions.  This
  *   kernel-mode stub will then be called transfer control to the user-mode
- *   pthread.
+ *   pthread by calling this function.
  *
  *   Normally the a user-mode start-up stub will also execute before the
  *   pthread actually starts.  See libc/pthread/pthread_startup.c
@@ -419,10 +420,65 @@ void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_functi
  ****************************************************************************/
 
 #if defined(CONFIG_NUTTX_KERNEL) && defined(__KERNEL__) && !defined(CONFIG_DISABLE_PTHREAD)
-void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg) noreturn_function;
+void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg)
+       noreturn_function;
 #endif
 
 /****************************************************************************
+ * Name: up_signal_handler
+ *
+ * Description:
+ *   In this kernel mode build, this function will be called to execute a
+ *   a signal handler in user-space.  When the signal is delivered, a
+ *   kernel-mode stub will first run to perform some housekeeping functions.
+ *   This kernel-mode stub will then be called transfer control to the user
+ *   mode signal handler by calling this function.
+ *
+ *   Normally the a user-mode signalling handling stub will also execute
+ *   before the ultimate signal handler is called.  See
+ *   libc/signal/signal_handler.c  This function is the user-space, signal
+ *   handler trampoline function.  It is called from up_signal_handler() in
+ *   user-mode.
+ *
+ * Inputs:
+ *   sighand - The address user-space signal handling function
+ *   signo, info, and ucontext - Standard arguments to be passed to the
+ *     signal handling function.
+ *
+ * Return:
+ *   None.  This function does not return in the normal sense.  It returns
+ *   via signal_handler_return (below)
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_NUTTX_KERNEL) && defined(__KERNEL__) && !defined(CONFIG_DISABLE_SIGNALS)
+void up_signal_handler(_sa_sigaction_t sighand, int signo,
+                       FAR siginfo_t *info, FAR void *ucontext);
+#endif
+
+/****************************************************************************
+ * Name: signal_handler_return
+ *
+ * Description:
+ *   This function is the user-space, signal handler return function.  It
+ *   is called from the signal_handler() in user-mode.  This function has the
+ *   general prototype:
+ *
+ *     void signal_handler_return(void);
+ *
+ *   However, it it not prototyped here because it should be implemented as
+ *   an inline function or macro that can be obtain by including the file
+ *   include/arch/syscall.h.
+ *
+ * Inputs:
+ *   None.
+ *
+ * Return:
+ *   None.  This function does not return.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
  * Name: up_allocate_heap
  *
  * Description:
diff --git a/nuttx/include/nuttx/sched.h b/nuttx/include/nuttx/sched.h
index 9101a2876..2641dd9d1 100644
--- a/nuttx/include/nuttx/sched.h
+++ b/nuttx/include/nuttx/sched.h
@@ -682,46 +682,6 @@ FAR struct task_tcb_s *task_vforksetup(start_t retaddr);
 pid_t task_vforkstart(FAR struct task_tcb_s *child);
 void task_vforkabort(FAR struct task_tcb_s *child, int errcode);
 
-/****************************************************************************
- * Name: task_startup
- *
- * Description:
- *   This function is the user-space, task startup function.  It is called
- *   from up_task_start() in user-mode.
- *
- * Inputs:
- *   entrypt - The user-space address of the task entry point
- *   argc and argv - Standard arguments for the task entry point
- *
- * Return:
- *   None.  This function does not return.
- *
- ****************************************************************************/
-
-#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
-void task_startup(main_t entrypt, int argc, FAR char *argv[]);
-#endif
-
-/****************************************************************************
- * Name: pthread_startup
- *
- * Description:
- *   This function is the user-space, pthread startup function.  It is called
- *   from up_pthread_start() in user-mode.
- *
- * Inputs:
- *   entrypt - The user-space address of the pthread entry point
- *   arg     - Standard argument for the pthread entry point
- *
- * Return:
- *   None.  This function does not return.
- *
- ****************************************************************************/
-
-#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__) && !defined(CONFIG_DISABLE_PTHREAD)
-void pthread_startup(pthread_startroutine_t entrypt, pthread_addr_t arg);
-#endif
-
 #undef EXTERN
 #if defined(__cplusplus)
 }
diff --git a/nuttx/include/nuttx/userspace.h b/nuttx/include/nuttx/userspace.h
index 842870664..38e123bc2 100644
--- a/nuttx/include/nuttx/userspace.h
+++ b/nuttx/include/nuttx/userspace.h
@@ -44,6 +44,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <signal.h>
 #include <pthread.h>
 
 #ifdef CONFIG_NUTTX_KERNEL
@@ -114,9 +115,18 @@ struct userspace_s
 
   /* Task/thread startup routines */
 
-  void (*task_startup)(main_t entrypt, int argc, FAR char *argv[]) noreturn_function;
+  void (*task_startup)(main_t entrypt, int argc, FAR char *argv[])
+    noreturn_function;
 #ifndef CONFIG_DISABLE_PTHREAD
-  void (*pthread_startup)(pthread_startroutine_t entrypt, pthread_addr_t arg);
+  void (*pthread_startup)(pthread_startroutine_t entrypt,
+    pthread_addr_t arg);
+#endif
+
+  /* Signal handler trampoline */
+
+#ifndef CONFIG_DISABLE_SIGNALS
+  void (*signal_handler)(_sa_sigaction_t sighand, int signo,
+    FAR siginfo_t *info, FAR void *ucontext);
 #endif
 
   /* Memory manager entry points */
@@ -154,6 +164,69 @@ extern "C"
  * Public Function Prototypes
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: task_startup
+ *
+ * Description:
+ *   This function is the user-space, task startup function.  It is called
+ *   from up_task_start() in user-mode.
+ *
+ * Inputs:
+ *   entrypt - The user-space address of the task entry point
+ *   argc and argv - Standard arguments for the task entry point
+ *
+ * Return:
+ *   None.  This function does not return.
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
+void task_startup(main_t entrypt, int argc, FAR char *argv[]);
+#endif
+
+/****************************************************************************
+ * Name: pthread_startup
+ *
+ * Description:
+ *   This function is the user-space, pthread startup function.  It is called
+ *   from up_pthread_start() in user-mode.
+ *
+ * Inputs:
+ *   entrypt - The user-space address of the pthread entry point
+ *   arg     - Standard argument for the pthread entry point
+ *
+ * Return:
+ *   None.  This function does not return.
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__) && !defined(CONFIG_DISABLE_PTHREAD)
+void pthread_startup(pthread_startroutine_t entrypt, pthread_addr_t arg);
+#endif
+
+/****************************************************************************
+ * Name: signal_handler
+ *
+ * Description:
+ *   This function is the user-space, signal handler trampoline function.  It
+ *   is called from up_signal_handler() in user-mode.
+ *
+ * Inputs:
+ *   sighand - The address user-space signal handling function
+ *   signo, info, and ucontext - Standard arguments to be passed to the
+ *     signal handling function.
+ *
+ * Return:
+ *   None.  This function does not return in the normal sense.  It returns
+ *   via signal_handler_return (see include/nuttx/arch.h)
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__) && !defined(CONFIG_DISABLE_SIGNALS)
+void signal_handler(_sa_sigaction_t sighand, int signo, FAR siginfo_t *info,
+                    FAR void *ucontext);
+#endif
+
 #undef EXTERN
 #ifdef __cplusplus
 }
diff --git a/nuttx/include/signal.h b/nuttx/include/signal.h
index a02170242..a31e62ff2 100644
--- a/nuttx/include/signal.h
+++ b/nuttx/include/signal.h
@@ -1,7 +1,7 @@
 /********************************************************************************
  * include/signal.h
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -206,19 +206,28 @@ struct siginfo
 
 typedef struct siginfo siginfo_t;
 
+/* Non-standard convenience definition of signal handling function types.
+ * These should be used only internally within the NuttX signal logic.
+ */
+
+typedef CODE void (*_sa_handler_t)(int);
+typedef CODE void (*_sa_sigaction_t)(int, FAR siginfo_t *, FAR void *);
+
 /* The following structure defines the action to take for given signal */
 
 struct sigaction
 {
   union
   {
-    CODE void (*_sa_handler)(int);
-    CODE void (*_sa_sigaction)(int, FAR siginfo_t *, FAR void *);
+    _sa_handler_t   _sa_handler;
+    _sa_sigaction_t _sa_sigaction;
   } sa_u;
-  sigset_t         sa_mask;
-  int              sa_flags;
+  sigset_t          sa_mask;
+  int               sa_flags;
 };
 
+/* Definitions that adjust the non-standard naming */
+
 #define sa_handler   sa_u._sa_handler
 #define sa_sigaction sa_u._sa_sigaction
 
diff --git a/nuttx/libc/pthread/pthread_startup.c b/nuttx/libc/pthread/pthread_startup.c
index dee9826fc..50aa263e4 100644
--- a/nuttx/libc/pthread/pthread_startup.c
+++ b/nuttx/libc/pthread/pthread_startup.c
@@ -42,7 +42,7 @@
 #include <pthread.h>
 #include <assert.h>
 
-#include <nuttx/sched.h>
+#include <nuttx/userspace.h>
 
 #if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
 
diff --git a/nuttx/libc/sched/task_startup.c b/nuttx/libc/sched/task_startup.c
index 8795faa7a..72cffbaaa 100644
--- a/nuttx/libc/sched/task_startup.c
+++ b/nuttx/libc/sched/task_startup.c
@@ -42,7 +42,7 @@
 #include <stdlib.h>
 #include <assert.h>
 
-#include <nuttx/sched.h>
+#include <nuttx/userspace.h>
 
 #if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
 
diff --git a/nuttx/libc/signal/Make.defs b/nuttx/libc/signal/Make.defs
index fe7eb180e..0264cce25 100644
--- a/nuttx/libc/signal/Make.defs
+++ b/nuttx/libc/signal/Make.defs
@@ -39,6 +39,10 @@ ifneq ($(CONFIG_DISABLE_SIGNALS),y)
 
 CSRCS += sig_emptyset.c sig_fillset.c sig_addset.c sig_delset.c sig_ismember.c
 
+ifeq ($(CONFIG_NUTTX_KERNEL),y)
+CSRCS += signal_handler.c
+endif
+
 # Add the signal directory to the build
 
 DEPPATH += --dep-path signal
diff --git a/nuttx/libc/signal/signal_handler.c b/nuttx/libc/signal/signal_handler.c
new file mode 100644
index 000000000..0a0996bae
--- /dev/null
+++ b/nuttx/libc/signal/signal_handler.c
@@ -0,0 +1,110 @@
+/****************************************************************************
+ * libc/signal/signal_handler.c
+ *
+ *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <signal.h>
+#include <assert.h>
+
+#include <arch/syscall.h>
+#include <nuttx/userspace.h>
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: signal_handler
+ *
+ * Description:
+ *   This function is the user-space, signal handler trampoline function.  It
+ *   is called from up_signal_handler() in user-mode.
+ *
+ * Inputs:
+ *   sighand - The address user-space signal handling function
+ *   signo, info, and ucontext - Standard arguments to be passed to the
+ *     signal handling function.
+ *
+ * Return:
+ *   None.  This function does not return in the normal sense.  It returns
+ *   via signal_handler_return (see include/nuttx/arch.h)
+ *
+ ****************************************************************************/
+
+void signal_handler(_sa_sigaction_t sighand, int signo, FAR siginfo_t *info,
+                    FAR void *ucontext)
+{
+  DEBUGASSERT(sighand);
+
+  /* Execute the signal handler. */
+
+  sighand(signo, info, ucontext);
+
+  /* And return from the signal handler */
+
+  signal_handler_return();
+}
+
+#endif /* CONFIG_NUTTX_KERNEL && !__KERNEL__ */
diff --git a/nuttx/sched/sig_deliver.c b/nuttx/sched/sig_deliver.c
index 3f0adc6d5..bb6ca71a4 100644
--- a/nuttx/sched/sig_deliver.c
+++ b/nuttx/sched/sig_deliver.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * sched/sig_deliver.c
  *
- *   Copyright (C) 2007, 2008, 2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2008, 2012-2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -127,9 +127,24 @@ void sig_deliver(FAR struct tcb_s *stcb)
       savesigprocmask = stcb->sigprocmask;
       stcb->sigprocmask = savesigprocmask | sigq->mask | SIGNO2SET(sigq->info.si_signo);
 
-      /* Deliver the signal */
+      /* Deliver the signal.  In the kernel build this has to be handled
+       * differently if we are dispatching to a signal handler in a user-
+       * space task or thread; we have to switch to user-mode before
+       * calling the task.
+       */
 
-      (*sigq->action.sighandler)(sigq->info.si_signo, &sigq->info, NULL);
+#ifdef CONFIG_NUTTX_KERNEL
+      if ((stcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_KERNEL)
+        {
+          up_signal_handler(sigq->action.sighandler, sigq->info.si_signo,
+                            &sigq->info, NULL);
+        }
+      else
+#endif
+        {
+          (*sigq->action.sighandler)(sigq->info.si_signo, &sigq->info,
+                                     NULL);
+        }
 
       /* Restore the original sigprocmask */