/****************************************************************************
* sched/task/task_vfork.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/wait.h>
#include <stdint.h>
#include <sched.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/queue.h>
#include "sched/sched.h"
#include "environ/environ.h"
#include "group/group.h"
#include "task/task.h"
#include "tls/tls.h"
/* vfork() requires architecture-specific support as well as waipid(). */
#if defined(CONFIG_ARCH_HAVE_VFORK) && defined(CONFIG_SCHED_WAITPID)
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxtask_setup_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 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 nxtask_setup_vfork().
* 3) nxtask_setup_vfork() 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
* - Allocate and initialize the stack
* - 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:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) up_vfork() then calls nxtask_start_vfork()
* 6) nxtask_start_vfork() then executes the child thread.
*
* Input Parameters:
* retaddr - Return address
* argsize - Location to return the argument size
*
* Returned Value:
* Upon successful completion, nxtask_setup_vfork() 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 *nxtask_setup_vfork(start_t retaddr)
{
FAR struct tcb_s *ptcb = this_task();
FAR struct tcb_s *parent;
FAR struct task_tcb_s *child;
size_t stack_size;
uint8_t ttype;
int priority;
int ret;
DEBUGASSERT(retaddr != NULL);
/* Get the type of the fork'ed task (kernel or user) */
if ((ptcb->flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_KERNEL)
{
/* Fork'ed from a kernel thread */
ttype = TCB_FLAG_TTYPE_KERNEL;
parent = ptcb;
}
else
{
/* Fork'ed from a user task or pthread */
ttype = TCB_FLAG_TTYPE_TASK;
if ((ptcb->flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_TASK)
{
parent = ptcb;
}
else
{
parent = nxsched_get_tcb(ptcb->group->tg_pid);
if (parent == NULL)
{
ret = -ENOENT;
goto errout;
}
}
}
/* 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");
ret = -ENOMEM;
goto errout;
}
/* Allocate a new task group with the same privileges as the parent */
ret = group_allocate(child, ttype);
if (ret < 0)
{
goto errout_with_tcb;
}
/* Duplicate the parent tasks environment */
ret = env_dup(child->cmn.group, environ);
if (ret < 0)
{
goto errout_with_tcb;
}
/* Associate file descriptors with the new task */
ret = group_setuptaskfiles(child);
if (ret < OK)
{
goto errout_with_tcb;
}
/* Allocate the stack for the TCB */
stack_size = (uintptr_t)ptcb->stack_base_ptr -
(uintptr_t)ptcb->stack_alloc_ptr + ptcb->adj_stack_size;
ret = up_create_stack(&child->cmn, stack_size, ttype);
if (ret < OK)
{
goto errout_with_tcb;
}
/* Setup thread local storage */
ret = tls_dup_info(&child->cmn, parent);
if (ret < OK)
{
goto errout_with_tcb;
}
/* Get the priority of the parent task */
#ifdef CONFIG_PRIORITY_INHERITANCE
priority = ptcb->base_priority; /* "Normal," unboosted priority */
#else
priority = ptcb->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 = nxtask_setup_scheduler(child, priority, retaddr,
ptcb->entry.main, ttype);
if (ret < OK)
{
goto errout_with_tcb;
}
/* Setup to pass parameters to the new task */
ret = nxtask_setup_arguments(child, parent->group->tg_info->argv[0],
&parent->group->tg_info->argv[1]);
if (ret < OK)
{
goto errout_with_tcb;
}
/* Now we have enough in place that we can join the group */
group_initialize(child);
sinfo("parent=%p, returning child=%p\n", parent, child);
return child;
errout_with_tcb:
nxsched_release_tcb((FAR struct tcb_s *)child, ttype);
errout:
set_errno(-ret);
return NULL;
}
/****************************************************************************
* Name: nxtask_start_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 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
* nxtask_setup_vfork().
* 3) nxtask_setup_vfork() 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
* - Allocate and initialize the stack
* - 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:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) vfork() then calls nxtask_start_vfork()
* 6) nxtask_start_vfork() 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 nxtask_start_vfork(FAR struct task_tcb_s *child)
{
pid_t pid;
int rc = 0;
int ret;
sinfo("Starting Child TCB=%p\n", child);
DEBUGASSERT(child);
/* Get the assigned pid before we start the task */
pid = child->cmn.pid;
/* Eliminate a race condition by disabling pre-emption. The child task
* can be instantiated, but cannot run until we call waitpid(). This
* assures us that we cannot miss the death-of-child signal (only
* needed in the SMP case).
*/
sched_lock();
/* Activate the task */
nxtask_activate((FAR struct tcb_s *)child);
/* The child task has not yet ran because pre-emption is disabled.
* The child task has the same priority as the parent task, so that
* would typically be the case anyway. However, in the SMP
* configuration, the child thread might have already ran on
* another CPU if pre-emption were not disabled.
*
* 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 assure that by waiting for the child thread to exit before
* returning to the parent thread. NOTE that pre-emption will be
* re-enabled while we are waiting, giving the child thread the
* opportunity to run.
*/
ret = waitpid(pid, &rc, 0);
if (ret < 0)
{
serr("ERROR: waitpid failed: %d\n", get_errno());
}
sched_unlock();
return pid;
}
/****************************************************************************
* Name: nxtask_abort_vfork
*
* Description:
* Recover from any errors after nxtask_setup_vfork() was called.
*
* Returned Value:
* None
*
****************************************************************************/
void nxtask_abort_vfork(FAR struct task_tcb_s *child, int errcode)
{
/* The TCB was added to the active task list by nxtask_setup_scheduler() */
dq_rem((FAR dq_entry_t *)child, &g_inactivetasks);
/* Release the TCB */
nxsched_release_tcb((FAR struct tcb_s *)child,
child->cmn.flags & TCB_FLAG_TTYPE_MASK);
set_errno(errcode);
}
#endif /* CONFIG_ARCH_HAVE_VFORK && CONFIG_SCHED_WAITPID */