144 lines
5.6 KiB
ArmAsm
144 lines
5.6 KiB
ArmAsm
/************************************************************************************
|
|
* arch/arm/src/armv6-m/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>
|
|
|
|
#include "up_vfork.h"
|
|
|
|
/************************************************************************************
|
|
* Pre-processor Definitions
|
|
************************************************************************************/
|
|
|
|
/************************************************************************************
|
|
* Global Symbols
|
|
************************************************************************************/
|
|
|
|
.cpu cortex-m0
|
|
.file "vfork.S"
|
|
.globl up_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 up_vfork() with the vfork()
|
|
* context as an argument. The overall sequence is:
|
|
*
|
|
* 1) User code calls vfork(). vfork() collects context information and
|
|
* transfers control up up_vfork().
|
|
* 2) up_vfork()and calls task_vforksetup().
|
|
* 3) task_vforksetup() allocates and configures the child task's TCB. This
|
|
* consists of:
|
|
* - Allocation of the child task's TCB.
|
|
* - Initialization of file descriptors and streams
|
|
* - Configuration of environment variables
|
|
* - Setup the intput parameters for the task.
|
|
* - Initialization of the TCB (including call to up_initial_state()
|
|
* 4) up_vfork() provides any additional operating context. up_vfork must:
|
|
* - Allocate and initialize the stack
|
|
* - Initialize special values in any CPU registers that were not
|
|
* already configured by up_initial_state()
|
|
* 5) up_vfork() then calls task_vforkstart()
|
|
* 6) task_vforkstart() then executes the child thread.
|
|
*
|
|
* 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.
|
|
*
|
|
************************************************************************************/
|
|
|
|
.align 2
|
|
.code 16
|
|
.thumb_func
|
|
.globl vfork
|
|
.type vfork, function
|
|
vfork:
|
|
/* Create a stack frame */
|
|
|
|
mov r0, sp /* Save the value of the stack on entry */
|
|
sub sp, sp, #VFORK_SIZEOF /* Allocate the structure on the stack */
|
|
|
|
/* CPU registers */
|
|
/* Save the volatile registers */
|
|
|
|
mov r1, sp
|
|
stmia r1!, {r4-r7} /* Save r4-r7 in the structure */
|
|
mov r4, r8 /* Copy high registers to low registers */
|
|
mov r5, r9
|
|
mov r6, r10
|
|
mov r7, fp
|
|
stmia r1!, {r4-r7} /* Save r8-r10 and fp in the structure */
|
|
mov r5, lr /* Copy lr to a low register */
|
|
stmia r1!, {r0,r5} /* Save sp and lr in the structure */
|
|
|
|
/* Then, call up_vfork(), passing it a pointer to the stack structure */
|
|
|
|
mov r0, sp
|
|
bl up_vfork
|
|
|
|
/* Recover r4-r7 that were destroyed before up_vfork was called */
|
|
|
|
mov r1, sp
|
|
ldmia r1!, {r4-r7}
|
|
|
|
/* Release the stack data and return the value returned by up_vfork */
|
|
|
|
ldr r1, [sp, #VFORK_LR_OFFSET]
|
|
mov r14, r1
|
|
add sp, sp, #VFORK_SIZEOF
|
|
bx lr
|
|
.size vfork, .-vfork
|
|
.end
|
|
|