diff options
Diffstat (limited to 'nuttx/arch/mips/src/mips32/up_vfork.c')
| -rw-r--r-- | nuttx/arch/mips/src/mips32/up_vfork.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/nuttx/arch/mips/src/mips32/up_vfork.c b/nuttx/arch/mips/src/mips32/up_vfork.c new file mode 100644 index 000000000..6b7e27f31 --- /dev/null +++ b/nuttx/arch/mips/src/mips32/up_vfork.c @@ -0,0 +1,254 @@ +/**************************************************************************** + * arch/mips/src/mips32/up_vfork.c + * + * 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 <stdint.h> +#include <string.h> +#include <assert.h> +#include <errno.h> +#include <debug.h> + +#include <nuttx/sched.h> +#include <nuttx/arch.h> +#include <arch/irq.h> + +#include "up_vfork.h" +#include "os_internal.h" + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +#ifndef CONFIG_STACK_ALIGNMENT +# define CONFIG_STACK_ALIGNMENT 4 +#endif + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: up_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. + * + * 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. + * + * task_vforkabort() may be called if an error occurs between steps 3 and 6. + * + * Input Paremeters: + * context - Caller context information saved by 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 up_vfork(const struct vfork_s *context) +{ + _TCB *parent = (FAR _TCB *)g_readytorun.head; + _TCB *child; + size_t stacksize; + uint32_t newsp; +#if CONFIG_MIPS32_FRAMEPOINTER + uint32_t newfp; +#endif + uint32_t stackutil; + int ret; + + svdbg("s0:%08x s1:%08x s2:%08x s3:%08x s4:%08x\n", + context->s0, context->s1, context->s2, context->s3, context->s4); +#if CONFIG_MIPS32_FRAMEPOINTER + svdbg("s5:%08x s6:%08x s7:%08x\n", + context->s5, context->s6, context->s7); +#ifdef MIPS32_SAVE_GP + svdbg("fp:%08x sp:%08x ra:%08x gp:%08x\n", + context->fp, context->sp, context->ra, context->gp); +#else + svdbg("fp:%08x sp:%08x ra:%08x\n", + context->fp context->sp, context->ra); +#endif +#else + svdbg("s5:%08x s6:%08x s7:%08x s8:%08x\n", + context->s5, context->s6, context->s7, context->s8); +#ifdef MIPS32_SAVE_GP + svdbg("sp:%08x ra:%08x gp:%08x\n", + context->sp, context->ra, context->gp); +#else + svdbg("sp:%08x ra:%08x\n", + context->sp, context->ra); +#endif +#endif + + /* Allocate and initialize a TCB for the child task. */ + + child = task_vforksetup((start_t)context->ra); + if (!child) + { + sdbg("task_vforksetup failed\n"); + return (pid_t)ERROR; + } + + svdbg("Parent=%p Child=%p\n", parent, child); + + /* 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; + + /* Allocate the stack for the TCB */ + + ret = up_create_stack(child, stacksize); + if (ret != OK) + { + sdbg("up_create_stack failed: %d\n", ret); + task_vforkabort(child, -ret); + return (pid_t)ERROR; + } + + /* How much of the parent's stack was utilized? The MIPS uses + * a push-down stack so that the current stack pointer should + * be lower than the initial, adjusted stack pointer. The + * stack usage should be the difference between those two. + */ + + DEBUGASSERT((uint32_t)parent->adj_stack_ptr > context->sp); + stackutil = (uint32_t)parent->adj_stack_ptr - context->sp; + + svdbg("stacksize:%d stackutil:%d\n", stacksize, stackutil); + + /* Make some feeble effort to perserve the stack contents. This is + * feeble because the stack surely contains invalid pointers and other + * content that will not work in the child context. However, if the + * user follows all of the caveats of vfor() usage, even this feeble + * effort is overkill. + */ + + newsp = (uint32_t)child->adj_stack_ptr - stackutil; + memcpy((void *)newsp, (const void *)context->sp, stackutil); + + /* Was there a frame pointer in place before? */ + +#if CONFIG_MIPS32_FRAMEPOINTER + if (context->fp <= (uint32_t)parent->adj_stack_ptr && + context->fp >= (uint32_t)parent->adj_stack_ptr - stacksize) + { + uint32_t frameutil = (uint32_t)parent->adj_stack_ptr - context->fp; + newfp = (uint32_t)child->adj_stack_ptr - frameutil; + } + else + { + newfp = context->fp; + } + + svdbg("Old stack base:%08x SP:%08x FP:%08x\n", + parent->adj_stack_ptr, context->sp, context->fp); + svdbg("New stack base:%08x SP:%08x FP:%08x\n", + child->adj_stack_ptr, newsp, newfp); +#else + svdbg("Old stack base:%08x SP:%08x\n", + parent->adj_stack_ptr, context->sp); + svdbg("New stack base:%08x SP:%08x\n", + child->adj_stack_ptr, newsp); +#endif + + /* Update the stack pointer, frame pointer, global pointer and saved + * registers. When the child TCB was initialized, all of the values + * were set to zero. up_initial_state() altered a few values, but the + * return value in v0 should be cleared to zero, providing the + * indication to the newly started child thread. + */ + + child->xcp.regs[REG_S0] = context->s0; /* Saved register s0 */ + child->xcp.regs[REG_S1] = context->s1; /* Saved register s1 */ + child->xcp.regs[REG_S2] = context->s2; /* Saved register s2 */ + child->xcp.regs[REG_S3] = context->s3; /* Volatile register s3 */ + child->xcp.regs[REG_S4] = context->s4; /* Volatile register s4 */ + child->xcp.regs[REG_S5] = context->s5; /* Volatile register s5 */ + child->xcp.regs[REG_S6] = context->s6; /* Volatile register s6 */ + child->xcp.regs[REG_S7] = context->s7; /* Volatile register s7 */ +#if CONFIG_MIPS32_FRAMEPOINTER + child->xcp.regs[REG_FP] = newfp; /* Frame pointer */ +#else + child->xcp.regs[REG_S8] = context->s8; /* Volatile register s8 */ +#endif + child->xcp.regs[REG_SP] = newsp; /* Stack pointer */ +#if MIPS32_SAVE_GP + child->xcp.regs[REG_GP] = newsp; /* Global pointer */ +#endif + + /* And, finally, start the child task. On a failure, task_vforkstart() + * will discard the TCB by calling task_vforkabort(). + */ + + return task_vforkstart(child); +} |