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

1 files changed, 96 insertions, 0 deletions

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
+