143 lines
5.5 KiB
ArmAsm
143 lines
5.5 KiB
ArmAsm
/************************************************************************************
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* arch/arm/src/armv7-m/vfork.S
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*
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* Copyright (C) 2013 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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************************************************************************************/
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/************************************************************************************
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* Included Files
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************************************************************************************/
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#include <nuttx/config.h>
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#include "up_vfork.h"
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/************************************************************************************
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* Pre-processor Definitions
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************************************************************************************/
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/************************************************************************************
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* Global Symbols
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************************************************************************************/
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.syntax unified
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.thumb
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.file "vfork.S"
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.globl up_vfork
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/************************************************************************************
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* Public Functions
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************************************************************************************/
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/************************************************************************************
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* Name: vfork
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*
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* Description:
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* The vfork() function has the same effect as fork(), except that the behavior is
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* undefined if the process created by vfork() either modifies any data other than
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* a variable of type pid_t used to store the return value from vfork(), or returns
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* from the function in which vfork() was called, or calls any other function before
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* successfully calling _exit() or one of the exec family of functions.
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*
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* This thin layer implements vfork by simply calling up_vfork() with the vfork()
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* context as an argument. The overall sequence is:
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*
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* 1) User code calls vfork(). vfork() collects context information and
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* transfers control up up_vfork().
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* 2) up_vfork()and calls task_vforksetup().
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* 3) task_vforksetup() allocates and configures the child task's TCB. This
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* consists of:
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* - Allocation of the child task's TCB.
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* - Initialization of file descriptors and streams
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* - Configuration of environment variables
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* - Setup the intput parameters for the task.
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* - Initialization of the TCB (including call to up_initial_state()
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* 4) up_vfork() provides any additional operating context. up_vfork must:
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* - Allocate and initialize the stack
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* - Initialize special values in any CPU registers that were not
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* already configured by up_initial_state()
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* 5) up_vfork() then calls task_vforkstart()
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* 6) task_vforkstart() then executes the child thread.
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*
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* Input Paremeters:
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* None
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*
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* Return:
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* Upon successful completion, vfork() returns 0 to the child process and returns
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* the process ID of the child process to the parent process. Otherwise, -1 is
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* returned to the parent, no child process is created, and errno is set to
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* indicate the error.
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*
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************************************************************************************/
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.thumb_func
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.globl vfork
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.type vfork, function
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vfork:
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/* Create a stack frame */
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mov r0, sp /* Save the value of the stack on entry */
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sub sp, sp, #VFORK_SIZEOF /* Allocate the structure on the stack */
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/* CPU registers */
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/* Save the volatile registers */
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str r4, [sp, #VFORK_R4_OFFSET]
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str r5, [sp, #VFORK_R5_OFFSET]
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str r6, [sp, #VFORK_R6_OFFSET]
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str r7, [sp, #VFORK_R7_OFFSET]
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str r8, [sp, #VFORK_R8_OFFSET]
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str r9, [sp, #VFORK_R9_OFFSET]
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str r10, [sp, #VFORK_R10_OFFSET]
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/* Save the frame pointer, stack pointer, and return address */
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str fp, [sp, #VFORK_FP_OFFSET]
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str r0, [sp, #VFORK_SP_OFFSET]
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str lr, [sp, #VFORK_LR_OFFSET]
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/* Floating point registers (not yet) */
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/* Then, call up_vfork(), passing it a pointer to the stack structure */
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mov r0, sp
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bl up_vfork
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/* Release the stack data and return the value returned by up_vfork */
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ldr lr, [sp, #VFORK_LR_OFFSET]
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add sp, sp, #VFORK_SIZEOF
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bx lr
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.size vfork, .-vfork
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.end
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