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Diffstat (limited to 'nuttx/arch/mips/src/mips32/vfork.S')
-rw-r--r-- | nuttx/arch/mips/src/mips32/vfork.S | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/nuttx/arch/mips/src/mips32/vfork.S b/nuttx/arch/mips/src/mips32/vfork.S new file mode 100644 index 000000000..2b7d180d3 --- /dev/null +++ b/nuttx/arch/mips/src/mips32/vfork.S @@ -0,0 +1,154 @@ +/************************************************************************************ + * arch/mips/src/mips32/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 + ************************************************************************************/ + + .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. + * + ************************************************************************************/ + + .text + .align 2 + .globl vfork + .type vfork, function + .set nomips16 + .ent vfork + +vfork: + /* Create a stack frame */ + + move $t0, $sp /* Save the value of the stack on entry */ + addiu $sp, $sp, -VFORK_SIZEOF /* Allocate the structure on the stack */ + + /* CPU registers */ + /* Save the saved registers */ + + sw $s0, VFORK_S0_OFFSET($sp) + sw $s1, VFORK_S1_OFFSET($sp) + sw $s2, VFORK_S2_OFFSET($sp) + sw $s3, VFORK_S3_OFFSET($sp) + sw $s4, VFORK_S4_OFFSET($sp) + sw $s5, VFORK_S5_OFFSET($sp) + sw $s6, VFORK_S6_OFFSET($sp) + sw $s7, VFORK_S7_OFFSET($sp) + +#ifdef CONFIG_MIPS32_FRAMEPOINTER + sw $fp, VFORK_FP_OFFSET($sp) +#else + sw $s8, VFORK_S8_OFFSET($sp) +#endif + + /* Save the global pointer, stack pointer, and return address */ + + sw $t0, VFORK_SP_OFFSET($sp) + sw $ra, VFORK_RA_OFFSET($sp) +#ifdef MIPS32_SAVE_GP + sw $gp, VFORK_GP_OFFSET($sp) +#endif + + /* Floating point registers (not yet) */ + + /* Then, call up_vfork(), passing it a pointer to the stack structure */ + + move $a0, $sp + jal up_vfork + nop + + /* Release the stack data and return the value returned by up_vfork */ + + lw $ra, VFORK_RA_OFFSET($sp) + addiu $sp, $sp, VFORK_SIZEOF + j $ra + + .end vfork + .size vfork, .-vfork |