diff options
Diffstat (limited to 'nuttx/arch/arm/src/armv7-m/vfork.S')
-rw-r--r-- | nuttx/arch/arm/src/armv7-m/vfork.S | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/nuttx/arch/arm/src/armv7-m/vfork.S b/nuttx/arch/arm/src/armv7-m/vfork.S new file mode 100644 index 000000000..f36ff23aa --- /dev/null +++ b/nuttx/arch/arm/src/armv7-m/vfork.S @@ -0,0 +1,142 @@ +/************************************************************************************ + * arch/arm/src/armv7-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 + ************************************************************************************/ + + .syntax unified + .thumb + .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. + * + ************************************************************************************/ + + .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 */ + + str r4, [sp, #VFORK_R4_OFFSET] + str r5, [sp, #VFORK_R5_OFFSET] + str r6, [sp, #VFORK_R6_OFFSET] + str r7, [sp, #VFORK_R7_OFFSET] + str r8, [sp, #VFORK_R8_OFFSET] + str r9, [sp, #VFORK_R9_OFFSET] + str r10, [sp, #VFORK_R10_OFFSET] + + /* Save the frame pointer, stack pointer, and return address */ + + str fp, [sp, #VFORK_FP_OFFSET] + str r0, [sp, #VFORK_SP_OFFSET] + str lr, [sp, #VFORK_LR_OFFSET] + + /* Floating point registers (not yet) */ + + /* Then, call up_vfork(), passing it a pointer to the stack structure */ + + mov r0, sp + bl up_vfork + + /* Release the stack data and return the value returned by up_vfork */ + + ldr lr, [sp, #VFORK_LR_OFFSET] + add sp, sp, #VFORK_SIZEOF + bx lr + .size vfork, .-vfork + .end + |