/**************************************************************************** * sched/task/task_vfork * * Copyright (C) 2013-2014 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #include #include "sched/sched.h" #include "group/group.h" #include "task/task.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* vfork() requires architecture-specific support as well as waipid(). */ #if defined(CONFIG_ARCH_HAVE_VFORK) && defined(CONFIG_SCHED_WAITPID) /* This is an artificial limit to detect error conditions where an argv[] * list is not properly terminated. */ #define MAX_VFORK_ARGS 256 /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: vfork_namesetup * * Description: * Copy the task name. * * Input Parameters: * tcb - Address of the new task's TCB * name - Name of the new task * * Return Value: * None * ****************************************************************************/ #if CONFIG_TASK_NAME_SIZE > 0 static inline void vfork_namesetup(FAR struct tcb_s *parent, FAR struct task_tcb_s *child) { /* Copy the name from the parent into the child TCB */ strncpy(child->cmn.name, parent->name, CONFIG_TASK_NAME_SIZE); } #else # define vfork_namesetup(p,c) #endif /* CONFIG_TASK_NAME_SIZE */ /**************************************************************************** * Name: vfork_stackargsetup * * Description: * Clone the task arguments in the same relative positions on the child's * stack. * * Input Parameters: * parent - Address of the parent task's TCB * child - Address of the child task's TCB * * Return Value: * Zero (OK) on success; a negated errno on failure. * ****************************************************************************/ static inline int vfork_stackargsetup(FAR struct tcb_s *parent, FAR struct task_tcb_s *child) { /* Is the parent a task? or a pthread? Only tasks (and kernel threads) * have command line arguments. */ child->argv = NULL; if ((parent->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD) { FAR struct task_tcb_s *ptcb = (FAR struct task_tcb_s *)parent; uintptr_t offset; int argc; /* Get the address correction */ offset = child->cmn.xcp.regs[REG_SP] - parent->xcp.regs[REG_SP]; /* Change the child argv[] to point into its stack (instead of its * parent's stack). */ child->argv = (FAR char **)((uintptr_t)ptcb->argv + offset); /* Copy the adjusted address for each argument */ argc = 0; while (ptcb->argv[argc]) { uintptr_t newaddr = (uintptr_t)ptcb->argv[argc] + offset; child->argv[argc] = (FAR char *)newaddr; /* Increment the number of args. Here is a sanity check to * prevent running away with an unterminated argv[] list. * MAX_VFORK_ARGS should be sufficiently large that this never * happens in normal usage. */ if (++argc > MAX_VFORK_ARGS) { return -E2BIG; } } /* Put a terminator entry at the end of the child argv[] array. */ child->argv[argc] = NULL; } return OK; } /**************************************************************************** * Name: vfork_argsetup * * Description: * Clone the argument list from the parent to the child. * * Input Parameters: * parent - Address of the parent task's TCB * child - Address of the child task's TCB * * Return Value: * Zero (OK) on success; a negated errno on failure. * ****************************************************************************/ static inline int vfork_argsetup(FAR struct tcb_s *parent, FAR struct task_tcb_s *child) { /* Clone the task name */ vfork_namesetup(parent, child); /* Adjust and copy the argv[] array. */ return vfork_stackargsetup(parent, child); } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: task_vforksetup * * 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 function provides one step in the overall vfork() sequence: It * Allocates and initializes the child task's TCB. The overall sequence is: * * 1) User code calls vfork(). vfork() is provided in architecture-specific * code. * 2) 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 input 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 Parameters: * parent - Address of the parent task's TCB * child - Address of the child task's TCB * * Returned Value: * Upon successful completion, task_vforksetup() returns a pointer to * newly allocated and initialized child task's TCB. NULL is returned * on any failure and the errno is set appropriately. * ****************************************************************************/ FAR struct task_tcb_s *task_vforksetup(start_t retaddr) { struct tcb_s *parent = this_task(); struct task_tcb_s *child; uint8_t ttype; int priority; int ret; DEBUGASSERT(retaddr); /* Get the type of the fork'ed task (kernel or user) */ if ((parent->flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_KERNEL) { /* Fork'ed from a kernel thread */ ttype = TCB_FLAG_TTYPE_KERNEL; } else { /* Fork'ed from a user task or pthread */ ttype = TCB_FLAG_TTYPE_TASK; } /* Allocate a TCB for the child task. */ child = (FAR struct task_tcb_s *)kmm_zalloc(sizeof(struct task_tcb_s)); if (!child) { serr("ERROR: Failed to allocate TCB\n"); set_errno(ENOMEM); return NULL; } /* Allocate a new task group with the same privileges as the parent */ #ifdef HAVE_TASK_GROUP ret = group_allocate(child, parent->flags); if (ret < 0) { goto errout_with_tcb; } #endif /* Associate file descriptors with the new task */ #if CONFIG_NFILE_DESCRIPTORS > 0 || CONFIG_NSOCKET_DESCRIPTORS > 0 ret = group_setuptaskfiles(child); if (ret < OK) { goto errout_with_tcb; } #endif /* Get the priority of the parent task */ #ifdef CONFIG_PRIORITY_INHERITANCE priority = parent->base_priority; /* "Normal," unboosted priority */ #else priority = parent->sched_priority; /* Current priority */ #endif /* Initialize the task control block. This calls up_initial_state() */ sinfo("Child priority=%d start=%p\n", priority, retaddr); ret = task_schedsetup(child, priority, retaddr, parent->entry.main, ttype); if (ret < OK) { goto errout_with_tcb; } sinfo("parent=%p, returning child=%p\n", parent, child); return child; errout_with_tcb: sched_releasetcb((FAR struct tcb_s *)child, ttype); set_errno(-ret); return NULL; } /**************************************************************************** * Name: task_vforkstart * * 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 function provides one step in the overall vfork() sequence: It * starts execution of the previously initialized TCB. The overall * sequence is: * * 1) User code calls vfork() * 2) Architecture-specific code provides 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 input parameters for the task. * - Initialization of the TCB (including call to up_initial_state() * 4) vfork() provides any additional operating context. vfork must: * - Allocate and initialize the stack * - Initialize special values in any CPU registers that were not * already configured by up_initial_state() * 5) vfork() then calls task_vforkstart() * 6) task_vforkstart() then executes the child thread. * * Input Parameters: * retaddr - The return address from vfork() where the child task * will be started. * * Returned Value: * 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 task_vforkstart(FAR struct task_tcb_s *child) { struct tcb_s *parent = this_task(); pid_t pid; int rc; int ret; sinfo("Starting Child TCB=%p, parent=%p\n", child, this_task()); DEBUGASSERT(child); /* Duplicate the original argument list in the forked child TCB */ ret = vfork_argsetup(parent, child); if (ret < 0) { task_vforkabort(child, -ret); return ERROR; } /* Now we have enough in place that we can join the group */ #ifdef HAVE_TASK_GROUP ret = group_initialize(child); if (ret < 0) { task_vforkabort(child, -ret); return ERROR; } #endif /* Get the assigned pid before we start the task */ pid = (int)child->cmn.pid; /* Activate the task */ ret = task_activate((FAR struct tcb_s *)child); if (ret < OK) { task_vforkabort(child, -ret); return ERROR; } /* Since the child task has the same priority as the parent task, it is * now ready to run, but has not yet ran. It is a requirement that * the parent environment be stable while vfork runs; the child thread * is still dependent on things in the parent thread... like the pointers * into parent thread's stack which will still appear in the child's * registers and environment. * * We do not have SIG_CHILD, so we have to do some silly things here. * The simplest way to make sure that the child thread runs to completion * is simply to yield here. Since the child can only do exit() or * execv/l(), that should be all that is needed. * * Hmmm.. this is probably not sufficient. What if we are running * SCHED_RR? What if the child thread is suspended and rescheduled * after the parent thread again? */ /* We can also exploit a bug in the execv() implementation: The PID * of the task exec'ed by the child will not be the same as the PID of * the child task. Therefore, waitpid() on the child task's PID will * accomplish what we need to do. */ rc = 0; #ifdef CONFIG_DEBUG_FEATURES ret = waitpid(pid, &rc, 0); if (ret < 0) { serr("ERROR: waitpid failed: %d\n", errno); } #else (void)waitpid(pid, &rc, 0); #endif return pid; } /**************************************************************************** * Name: task_vforkabort * * Description: * Recover from any errors after task_vforksetup() was called. * * Returned Value: * None * ****************************************************************************/ void task_vforkabort(FAR struct task_tcb_s *child, int errcode) { /* The TCB was added to the active task list by task_schedsetup() */ dq_rem((FAR dq_entry_t *)child, (FAR dq_queue_t *)&g_inactivetasks); /* Release the TCB */ sched_releasetcb((FAR struct tcb_s *)child, child->cmn.flags & TCB_FLAG_TTYPE_MASK); set_errno(errcode); } #endif /* CONFIG_ARCH_HAVE_VFORK && CONFIG_SCHED_WAITPID */