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/****************************************************************************
* 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);
}
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