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, 134 insertions, 0 deletions

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);
+}