Implement a simple vfork(). ARM only for now

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5486 42af7a65-404d-4744-a932-0658087f49c3

19 files changed, 389 insertions, 52 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index f4f697563..e2d8a586b 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3878,5 +3878,6 @@
 	* sched/os_bringup.c:  Remove support for CONFIG_BUILTIN_APP_START.
 	  This is not really a useful feature and creates a violation of the
 	  OS layered architecture.
-
+	* include/unistd.h, arch/arch/src/*:  Implement a simple vfork().
+	  On initial checkin, this API is available only for ARM platforms.
 
diff --git a/nuttx/arch/arm/src/arm/up_vfork.S b/nuttx/arch/arm/src/arm/up_vfork.S
new file mode 100644
index 000000000..23e975c30
--- /dev/null
+++ b/nuttx/arch/arm/src/arm/up_vfork.S
@@ -0,0 +1,92 @@
+/************************************************************************************
+ * arch/arm/src/arm/up_vfork.S
+ *
+ *   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>
+
+/************************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Global Symbols
+ ************************************************************************************/
+
+	.file	"up_vfork.S"
+	.globl	__vfork
+
+/************************************************************************************
+ * Public Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: vfork
+ *
+ * Description:
+ *   The vfork() function has the same effect as fork(), except that the behavior is
+ *   undefined if the process created by vfork() either modifies any data other than
+ *   a variable of type pid_t used to store the return value from vfork(), or returns
+ *   from the function in which vfork() was called, or calls any other function before
+ *   successfully calling _exit() or one of the exec family of functions. 
+ *
+ *   This thin layer implements vfork by simply calling __vfork() with the vfork()
+ *   return address as an argument.
+ *
+ * Input Paremeters:
+ *   None
+ *
+ * Return:
+ *   Upon successful completion, vfork() returns 0 to the child process and returns
+ *   the process ID of the child process to the parent process. Otherwise, -1 is
+ *   returned to the parent, no child process is created, and errno is set to
+ *   indicate the error. 
+ *
+ ************************************************************************************/
+
+	.globl	vfork
+	.type	vfork, function
+vfork:
+
+    /* I know, I could have used the GCC's return address builtin and done this all
+     * in C.  But this works even if there is no builtin.
+     */
+
+	mov		r0, lr
+	b		__vfork
+	.size	vfork, .-vfork
+	.end
diff --git a/nuttx/arch/arm/src/armv7-m/up_vfork.S b/nuttx/arch/arm/src/armv7-m/up_vfork.S
new file mode 100644
index 000000000..65ccc4535
--- /dev/null
+++ b/nuttx/arch/arm/src/armv7-m/up_vfork.S
@@ -0,0 +1,96 @@
+/************************************************************************************
+ * arch/arm/src/armv7-m/up_vfork.S
+ *
+ *   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>
+
+/************************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Global Symbols
+ ************************************************************************************/
+
+	.syntax	unified
+	.thumb
+	.file	"up_vfork.S"
+	.globl	__vfork
+
+/************************************************************************************
+ * Public Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: vfork
+ *
+ * Description:
+ *   The vfork() function has the same effect as fork(), except that the behavior is
+ *   undefined if the process created by vfork() either modifies any data other than
+ *   a variable of type pid_t used to store the return value from vfork(), or returns
+ *   from the function in which vfork() was called, or calls any other function before
+ *   successfully calling _exit() or one of the exec family of functions. 
+ *
+ *   This thin layer implements vfork by simply calling __vfork() with the vfork()
+ *   return address as an argument.
+ *
+ * Input Paremeters:
+ *   None
+ *
+ * Return:
+ *   Upon successful completion, vfork() returns 0 to the child process and returns
+ *   the process ID of the child process to the parent process. Otherwise, -1 is
+ *   returned to the parent, no child process is created, and errno is set to
+ *   indicate the error. 
+ *
+ ************************************************************************************/
+
+	.thumb_func
+	.globl	vfork
+	.type	vfork, function
+vfork:
+
+    /* I know, I could have used the GCC's return address builtin and done this all
+     * in C.  But this works even if there is no builtin.
+     */
+
+	mov		r0, lr
+	b		__vfork
+	.size	vfork, .-vfork
+	.end
+
diff --git a/nuttx/arch/arm/src/c5471/Make.defs b/nuttx/arch/arm/src/c5471/Make.defs
index 2bc396fd3..89c3aaf0b 100644
--- a/nuttx/arch/arm/src/c5471/Make.defs
+++ b/nuttx/arch/arm/src/c5471/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # c5471/Make.defs
 #
-#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2007, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -35,14 +35,14 @@
 
 HEAD_ASRC	= up_nommuhead.S
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
 		  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c up_doirq.c \
 		  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
 		  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
 		  up_releasestack.c up_reprioritizertr.c up_schedulesigaction.c \
 		  up_sigdeliver.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c
+		  up_undefinedinsn.c up_usestack.c up__vfork.c
 
 ifeq ($(CONFIG_ELF),y)
 CMN_CSRCS += up_elf.c
diff --git a/nuttx/arch/arm/src/calypso/Make.defs b/nuttx/arch/arm/src/calypso/Make.defs
index 4b53c3b7c..957d4e677 100644
--- a/nuttx/arch/arm/src/calypso/Make.defs
+++ b/nuttx/arch/arm/src/calypso/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # calypso/Make.defs
 #
-#   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2007, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 #   Copyright (C) 2011 Stefan Richter. All rights reserved.
@@ -39,14 +39,14 @@
 HEAD_ASRC = calypso_head.S
 
 CMN_ASRCS = up_saveusercontext.S up_fullcontextrestore.S up_vectors.S \
-            up_nommuhead.S
+            up_nommuhead.S up_vfork.S
 CMN_CSRCS = up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
             up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c up_doirq.c \
             up_exit.c up_idle.c up_initialstate.c up_initialize.c \
             up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
             up_releasestack.c up_reprioritizertr.c up_schedulesigaction.c \
             up_sigdeliver.c up_syscall.c up_unblocktask.c \
-            up_undefinedinsn.c up_usestack.c calypso_power.c
+            up_undefinedinsn.c up_usestack.c calypso_power.c up__vfork.c
 
 ifeq ($(CONFIG_ELF),y)
 CMN_CSRCS += up_elf.c
diff --git a/nuttx/arch/arm/src/common/up__vfork.c b/nuttx/arch/arm/src/common/up__vfork.c
new file mode 100644
index 000000000..a1081faa8
--- /dev/null
+++ b/nuttx/arch/arm/src/common/up__vfork.c
@@ -0,0 +1,134 @@
+/****************************************************************************
+ * arch/arm/src/common/up__vfork
+ *
+ *   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 <sched.h>
+
+#include <nuttx/sched.h>
+
+#include "os_internal.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* ARM requires at least a 4-byte stack alignment.  For use with EABI and
+ * floating point, the stack must be aligned to 8-byte addresses.
+ */
+
+#ifndef CONFIG_STACK_ALIGNMENT
+
+/* The symbol  __ARM_EABI__ is defined by GCC if EABI is being used.  If you
+ * are not using GCC, make sure that CONFIG_STACK_ALIGNMENT is set correctly!
+ */
+
+#  ifdef __ARM_EABI__
+#    define CONFIG_STACK_ALIGNMENT 8
+#  else
+#    define CONFIG_STACK_ALIGNMENT 4
+#  endif
+#endif
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: __vfork
+ *
+ * Description:
+ *   The vfork() function has the same effect as fork(), except that the
+ *   behavior is undefined if the process created by vfork() either modifies
+ *   any data other than a variable of type pid_t used to store the return
+ *   value from vfork(), or returns from the function in which vfork() was
+ *   called, or calls any other function before successfully calling _exit()
+ *   or one of the exec family of functions. 
+ *
+ *   This thin layer starts the vfork child by simply spawning a new thread
+ *   that begins at the return address of vfork().
+ *
+ * Input Paremeters:
+ *   retaddr - The return address of vfork()
+ *
+ * Return:
+ *   Upon successful completion, vfork() returns 0 to the child process and
+ *   returns the process ID of the child process to the parent process.
+ *   Otherwise, -1 is returned to the parent, no child process is created,
+ *   and errno is set to indicate the error. 
+ *
+ ****************************************************************************/
+
+pid_t __vfork(uint32_t retaddr)
+{
+  FAR _TCB *parent = (FAR _TCB *)g_readytorun.head;
+  size_t stacksize;
+  int priority;
+
+  /* Get the size of the parent task's stack.  Due to alignment operations,
+   * the adjusted stack size may be smaller than the stack size originally
+   * requrested.
+   */
+
+  stacksize = parent->adj_stack_size + CONFIG_STACK_ALIGNMENT - 1;
+
+  /* Get the current priority of the parent task */
+
+#ifdef CONFIG_PRIORITY_INHERITANCE
+  priority = parent->base_priority;  /* "Normal," unboosted priority */
+#else
+  priority = parent->sched_priority;  /* Current priority */
+#endif
+
+ /* Start the child thread at the vfork return address.  TASK_CREATE will
+  * return the PID of the new thread.  Otherwise a negative value will be
+  * returned and the errno will be set appropriately.
+  *
+  * When the registers are initialized, the return value in R0 should be
+  * cleared to zero, providing the indication to the newly started child
+  * thread.
+  */
+
+  return TASK_CREATE("init", priority, stacksize, (main_t)retaddr,
+                     (const char **)NULL);
+}
diff --git a/nuttx/arch/arm/src/dm320/Make.defs b/nuttx/arch/arm/src/dm320/Make.defs
index 9087708ef..52e65c0e8 100644
--- a/nuttx/arch/arm/src/dm320/Make.defs
+++ b/nuttx/arch/arm/src/dm320/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # dm320/Make.defs
 #
-#   Copyright (C) 2007, 2010 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2007, 2010, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -36,14 +36,14 @@
 HEAD_ASRC	= up_head.S
 
 CMN_ASRCS	= up_cache.S up_fullcontextrestore.S up_saveusercontext.S \
-		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S
+		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 		  up_dataabort.c up_mdelay.c up_udelay.c up_exit.c up_idle.c \
 		  up_initialize.c up_initialstate.c up_interruptcontext.c \
 		  up_prefetchabort.c up_releasepending.c up_releasestack.c \
 		  up_reprioritizertr.c up_schedulesigaction.c \
 		  up_sigdeliver.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c
+		  up_undefinedinsn.c up_usestack.c up__vfork.c
 
 ifeq ($(CONFIG_ELF),y)
 CMN_CSRCS += up_elf.c
diff --git a/nuttx/arch/arm/src/imx/Make.defs b/nuttx/arch/arm/src/imx/Make.defs
index a1c2e72e6..a7c0ceebd 100644
--- a/nuttx/arch/arm/src/imx/Make.defs
+++ b/nuttx/arch/arm/src/imx/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/imx/Make.defs
 #
-#   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2009, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -36,14 +36,14 @@
 HEAD_ASRC	= up_head.S
 
 CMN_ASRCS	= up_cache.S up_fullcontextrestore.S up_saveusercontext.S \
-		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S
+		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 		  up_dataabort.c up_mdelay.c up_udelay.c up_exit.c up_idle.c \
 		  up_initialize.c up_initialstate.c up_interruptcontext.c \
 		  up_prefetchabort.c up_releasepending.c up_releasestack.c \
 		  up_reprioritizertr.c up_schedulesigaction.c \
 		  up_sigdeliver.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c
+		  up_undefinedinsn.c up_usestack.c up__vfork.c
 
 ifeq ($(CONFIG_ELF),y)
 CMN_CSRCS += up_elf.c
diff --git a/nuttx/arch/arm/src/kinetis/Make.defs b/nuttx/arch/arm/src/kinetis/Make.defs
index 65bc7b465..bad2946e2 100644
--- a/nuttx/arch/arm/src/kinetis/Make.defs
+++ b/nuttx/arch/arm/src/kinetis/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/kinetis/Make.defs
 #
-#   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2011, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -39,14 +39,16 @@ HEAD_ASRC	= kinetis_vectors.S
 
 # Common ARM and Cortex-M3 files
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S \
+			  up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
 			  up_createstack.c up_mdelay.c up_udelay.c up_exit.c up_initialize.c \
 			  up_memfault.c up_initialstate.c up_interruptcontext.c \
 			  up_modifyreg8.c up_modifyreg16.c up_modifyreg32.c \
 			  up_releasestack.c up_reprioritizertr.c up_schedulesigaction.c \
 			  up_releasepending.c up_sigdeliver.c up_unblocktask.c up_usestack.c \
-			  up_doirq.c up_hardfault.c up_svcall.c up_checkstack.c
+			  up_doirq.c up_hardfault.c up_svcall.c up_checkstack.c \
+			  up__vfork.c
 
 ifeq ($(CONFIG_ARCH_MEMCPY),y)
 CMN_ASRCS	+= up_memcpy.S
diff --git a/nuttx/arch/arm/src/lm3s/Make.defs b/nuttx/arch/arm/src/lm3s/Make.defs
index 8d2918027..c745e1953 100644
--- a/nuttx/arch/arm/src/lm3s/Make.defs
+++ b/nuttx/arch/arm/src/lm3s/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/lm3s/Make.defs
 #
-#   Copyright (C) 2009-2011 Gregory Nutt. All rights reserved.
+#   Copyright (C) 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
@@ -35,14 +35,16 @@
 
 HEAD_ASRC	= lm3s_vectors.S
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S \
+			  up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
 			  up_createstack.c up_mdelay.c up_udelay.c up_exit.c \
 			  up_idle.c up_initialize.c up_initialstate.c up_interruptcontext.c \
 			  up_memfault.c up_modifyreg8.c up_modifyreg16.c up_modifyreg32.c \
 			  up_releasepending.c up_releasestack.c up_reprioritizertr.c \
 			  up_schedulesigaction.c up_sigdeliver.c up_unblocktask.c \
-			  up_usestack.c up_doirq.c up_hardfault.c up_svcall.c
+			  up_usestack.c up_doirq.c up_hardfault.c up_svcall.c \
+			  up__vfork.c
 
 ifeq ($(CONFIG_ARCH_MEMCPY),y)
 CMN_ASRCS	+= up_memcpy.S
diff --git a/nuttx/arch/arm/src/lpc17xx/Make.defs b/nuttx/arch/arm/src/lpc17xx/Make.defs
index c7ef4a147..1ea0183a1 100644
--- a/nuttx/arch/arm/src/lpc17xx/Make.defs
+++ b/nuttx/arch/arm/src/lpc17xx/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/lpc17xx/Make.defs
 #
-#   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2010-2011, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -39,14 +39,15 @@ HEAD_ASRC	= lpc17_vectors.S
 
 # Common ARM and Cortex-M3 files
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S \
+			  up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 			  up_mdelay.c up_udelay.c up_exit.c up_initialize.c up_memfault.c \
 			  up_initialstate.c up_interruptcontext.c up_modifyreg8.c \
 			  up_modifyreg16.c up_modifyreg32.c up_releasepending.c \
 			  up_releasestack.c up_reprioritizertr.c up_schedulesigaction.c \
 			  up_sigdeliver.c up_unblocktask.c up_usestack.c up_doirq.c \
-			  up_hardfault.c up_svcall.c up_checkstack.c
+			  up_hardfault.c up_svcall.c up_checkstack.c up__vfork.c
 
 ifeq ($(CONFIG_ARCH_MEMCPY),y)
 CMN_ASRCS	+= up_memcpy.S
diff --git a/nuttx/arch/arm/src/lpc214x/Make.defs b/nuttx/arch/arm/src/lpc214x/Make.defs
index ae5ed15fb..6821d512b 100644
--- a/nuttx/arch/arm/src/lpc214x/Make.defs
+++ b/nuttx/arch/arm/src/lpc214x/Make.defs
@@ -1,7 +1,7 @@
 ##############################################################################
 # lpc214x/Make.defs
 #
-#   Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2007, 2008, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -35,13 +35,14 @@
 
 HEAD_ASRC	= lpc214x_head.S
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S \
+			  up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
 		  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c \
 		  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
 		  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
 		  up_releasestack.c up_reprioritizertr.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c up_lowputs.c
+		  up_undefinedinsn.c up_usestack.c up_lowputs.c up__vfork.c
 
 ifneq ($(CONFIG_DISABLE_SIGNALS),y)
 CMN_CSRCS	+= up_schedulesigaction.c up_sigdeliver.c
diff --git a/nuttx/arch/arm/src/lpc2378/Make.defs b/nuttx/arch/arm/src/lpc2378/Make.defs
index 4fe75d924..3d3c15926 100644
--- a/nuttx/arch/arm/src/lpc2378/Make.defs
+++ b/nuttx/arch/arm/src/lpc2378/Make.defs
@@ -1,7 +1,7 @@
 ##############################################################################
 # lpc23xx/Make.defs
 #
-#   Copyright (C) 2010 Rommel Marcelo. All rights reserved.
+#   Copyright (C) 2010, 2013 Rommel Marcelo. All rights reserved.
 #   Author: Rommel Marcelo
 #
 # This file is part of the NuttX RTOS and based on the lpc2148 port:
@@ -40,13 +40,14 @@
 
 HEAD_ASRC	= lpc23xx_head.S
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S \
+			  up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
-		  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c \
-		  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
-		  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
-		  up_releasestack.c up_reprioritizertr.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c up_lowputs.c
+			  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c \
+			  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
+			  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
+			  up_releasestack.c up_reprioritizertr.c up_syscall.c up_unblocktask.c \
+			  up_undefinedinsn.c up_usestack.c up_lowputs.c up__vfork.c
 
 ifneq ($(CONFIG_DISABLE_SIGNALS),y)
 CMN_CSRCS	+= up_schedulesigaction.c up_sigdeliver.c
diff --git a/nuttx/arch/arm/src/lpc31xx/Make.defs b/nuttx/arch/arm/src/lpc31xx/Make.defs
index db63563ef..b3a9746b4 100644
--- a/nuttx/arch/arm/src/lpc31xx/Make.defs
+++ b/nuttx/arch/arm/src/lpc31xx/Make.defs
@@ -36,7 +36,7 @@
 HEAD_ASRC	= up_head.S
 
 CMN_ASRCS	= up_cache.S up_fullcontextrestore.S up_saveusercontext.S \
-		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S
+		  up_vectors.S up_vectoraddrexcptn.S up_vectortab.S up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 		  up_dataabort.c up_mdelay.c up_udelay.c up_exit.c up_idle.c \
 		  up_initialize.c up_initialstate.c up_interruptcontext.c \
@@ -44,7 +44,7 @@ CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 		  up_prefetchabort.c up_releasepending.c up_releasestack.c \
 		  up_reprioritizertr.c up_schedulesigaction.c \
 		  up_sigdeliver.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c
+		  up_undefinedinsn.c up_usestack.c up__vfork.c
 
 ifeq ($(CONFIG_PAGING),y)
 CMN_CSRCS	+= up_pginitialize.c up_checkmapping.c up_allocpage.c up_va2pte.c
diff --git a/nuttx/arch/arm/src/lpc43xx/Make.defs b/nuttx/arch/arm/src/lpc43xx/Make.defs
index cd78ddd5b..211f9bee3 100644
--- a/nuttx/arch/arm/src/lpc43xx/Make.defs
+++ b/nuttx/arch/arm/src/lpc43xx/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/lpc43xx/Make.defs
 #
-#   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012-2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,16 +33,18 @@
 #
 ############################################################################
 
-HEAD_ASRC  = 
+HEAD_ASRC  =
 
 CMN_ASRCS  = up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
-CMN_CSRCS += up_assert.c up_blocktask.c up_copystate.c
+CMN_ASRCS += up_vfork.S
+
+CMN_CSRCS  = up_assert.c up_blocktask.c up_copystate.c
 CMN_CSRCS += up_createstack.c up_mdelay.c up_udelay.c up_exit.c
 CMN_CSRCS += up_initialize.c up_initialstate.c up_interruptcontext.c
 CMN_CSRCS += up_memfault.c up_modifyreg8.c up_modifyreg16.c up_modifyreg32.c
 CMN_CSRCS += up_releasepending.c up_releasestack.c up_reprioritizertr.c
 CMN_CSRCS += up_schedulesigaction.c up_sigdeliver.c up_unblocktask.c
-CMN_CSRCS += up_usestack.c up_doirq.c up_hardfault.c up_svcall.c
+CMN_CSRCS += up_usestack.c up_doirq.c up_hardfault.c up_svcall.c up__vfork.c
 
 ifeq ($(CONFIG_ARMV7M_CMNVECTOR),y)
 CMN_ASRCS += up_exception.S
diff --git a/nuttx/arch/arm/src/sam3u/Make.defs b/nuttx/arch/arm/src/sam3u/Make.defs
index daa129169..4682ea83d 100644
--- a/nuttx/arch/arm/src/sam3u/Make.defs
+++ b/nuttx/arch/arm/src/sam3u/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/sam3u/Make.defs
 #
-#   Copyright (C) 2009-2011 Gregory Nutt. All rights reserved.
+#   Copyright (C) 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
@@ -39,14 +39,15 @@ HEAD_ASRC	= sam3u_vectors.S
 
 # Common ARM and Cortex-M3 files
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S \
+			  up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
 			  up_mdelay.c up_udelay.c up_exit.c up_idle.c up_initialize.c \
 			  up_initialstate.c up_interruptcontext.c up_memfault.c up_modifyreg8.c \
 			  up_modifyreg16.c up_modifyreg32.c up_releasepending.c \
 			  up_releasestack.c up_reprioritizertr.c up_schedulesigaction.c \
 			  up_sigdeliver.c up_unblocktask.c up_usestack.c up_doirq.c \
-			  up_hardfault.c up_svcall.c
+			  up_hardfault.c up_svcall.c up__vfork.c
 
 # Configuration-dependent common files
 
diff --git a/nuttx/arch/arm/src/stm32/Make.defs b/nuttx/arch/arm/src/stm32/Make.defs
index 1e6c0c401..89c291791 100644
--- a/nuttx/arch/arm/src/stm32/Make.defs
+++ b/nuttx/arch/arm/src/stm32/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/stm32/Make.defs
 #
-#   Copyright (C) 2009, 2011-2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 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
@@ -39,14 +39,16 @@ else
 HEAD_ASRC	= stm32_vectors.S
 endif
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_switchcontext.S \
+			  up_vfork.S
 CMN_CSRCS	= up_assert.c up_blocktask.c up_copystate.c \
 			  up_createstack.c up_mdelay.c up_udelay.c up_exit.c \
 			  up_initialize.c up_initialstate.c up_interruptcontext.c \
 			  up_memfault.c up_modifyreg8.c up_modifyreg16.c up_modifyreg32.c \
 			  up_releasepending.c up_releasestack.c up_reprioritizertr.c \
 			  up_schedulesigaction.c up_sigdeliver.c up_systemreset.c \
-			  up_unblocktask.c up_usestack.c up_doirq.c up_hardfault.c up_svcall.c
+			  up_unblocktask.c up_usestack.c up_doirq.c up_hardfault.c \
+			  up_svcall.c up__vfork.c
 
 ifeq ($(CONFIG_ARMV7M_CMNVECTOR),y)
 CMN_ASRCS	+= up_exception.S
diff --git a/nuttx/arch/arm/src/str71x/Make.defs b/nuttx/arch/arm/src/str71x/Make.defs
index 32eaddcdb..3612950a6 100644
--- a/nuttx/arch/arm/src/str71x/Make.defs
+++ b/nuttx/arch/arm/src/str71x/Make.defs
@@ -1,7 +1,7 @@
 ##############################################################################
 # arch/arm/src/str71x/Make.defs
 #
-#   Copyright (C) 2008 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2008, 2013 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -35,13 +35,14 @@
 
 HEAD_ASRC	= str71x_head.S
 
-CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S
+CMN_ASRCS	= up_saveusercontext.S up_fullcontextrestore.S up_vectors.S \
+			  up_vfork.S
 CMN_CSRCS	= up_allocateheap.c up_assert.c up_blocktask.c up_copystate.c \
-		  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c \
-		  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
-		  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
-		  up_releasestack.c up_reprioritizertr.c up_syscall.c up_unblocktask.c \
-		  up_undefinedinsn.c up_usestack.c up_lowputs.c
+			  up_createstack.c up_dataabort.c up_mdelay.c up_udelay.c \
+			  up_exit.c up_idle.c up_initialize.c up_initialstate.c \
+			  up_interruptcontext.c up_prefetchabort.c up_releasepending.c \
+			  up_releasestack.c up_reprioritizertr.c up_syscall.c up_unblocktask.c \
+			  up_undefinedinsn.c up_usestack.c up_lowputs.c up__vfork.c
 
 ifneq ($(CONFIG_DISABLE_SIGNALS),y)
 CMN_CSRCS	+= up_schedulesigaction.c up_sigdeliver.c
diff --git a/nuttx/include/unistd.h b/nuttx/include/unistd.h
index 681ce9e63..ddb6880f4 100644
--- a/nuttx/include/unistd.h
+++ b/nuttx/include/unistd.h
@@ -1,7 +1,7 @@
 /****************************************************************************
  * include/unistd.h
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -129,6 +129,7 @@ EXTERN int       optopt; /* unrecognized option character */
 
 /* Task Control Interfaces */
 
+EXTERN pid_t   vfork(void);
 EXTERN pid_t   getpid(void);
 EXTERN void    _exit(int status) noreturn_function;
 EXTERN unsigned int sleep(unsigned int seconds);