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incubator-nuttx/sched/task/task_posixspawn.c

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/****************************************************************************
* sched/task/task_posixspawn.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 <sys/wait.h>
#include <spawn.h>
#include <debug.h>
#include <nuttx/kthread.h>
#include <nuttx/binfmt/binfmt.h>
#include <nuttx/binfmt/symtab.h>
#include "sched/sched.h"
#include "group/group.h"
#include "task/spawn.h"
#include "task/task.h"
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: posix_spawn_exec
*
* Description:
* Execute the task from the file system.
*
* Input Parameters:
*
* pidp - Upon successful completion, this will return the task ID of the
* child task in the variable pointed to by a non-NULL 'pid' argument.|
*
* path - The 'path' argument identifies the file to execute. If
* CONFIG_BINFMT_EXEPATH is defined, this may be either a relative or
* or an absolute path. Otherwise, it must be an absolute path.
*
* attr - If the value of the 'attr' parameter is NULL, the all default
* values for the POSIX spawn attributes will be used. Otherwise, the
* attributes will be set according to the spawn flags. The
* following spawn flags are supported:
*
* - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
* value.
* - POSIX_SPAWN_SETSCHEDULER: Set the new tasks scheduler priority to
* the sched_policy value.
*
* NOTE: POSIX_SPAWN_SETSIGMASK is handled in ps_proxy().
*
* argv - argv[] is the argument list for the new task. argv[] is an
* array of pointers to null-terminated strings. The list is terminated
* with a null pointer.
*
* Returned Value:
* This function will return zero on success. Otherwise, an error number
* will be returned as the function return value to indicate the error.
* This errno value may be that set by execv(), sched_setpolicy(), or
* sched_setparam().
*
****************************************************************************/
static int posix_spawn_exec(FAR pid_t *pidp, FAR const char *path,
FAR const posix_spawnattr_t *attr,
FAR char * const argv[])
{
FAR const struct symtab_s *symtab;
int nsymbols;
int pid;
int ret = OK;
DEBUGASSERT(path);
/* Get the current symbol table selection */
exec_getsymtab(&symtab, &nsymbols);
/* Disable pre-emption so that we can modify the task parameters after
* we start the new task; the new task will not actually begin execution
* until we re-enable pre-emption.
*/
sched_lock();
/* Start the task */
pid = exec(path, (FAR char * const *)argv, symtab, nsymbols);
if (pid < 0)
{
ret = get_errno();
serr("ERROR: exec failed: %d\n", ret);
goto errout;
}
/* Return the task ID to the caller */
if (pid)
{
*pidp = pid;
}
/* Now set the attributes. Note that we ignore all of the return values
* here because we have already successfully started the task. If we
* return an error value, then we would also have to stop the task.
*/
if (attr)
{
(void)spawn_execattrs(pid, attr);
}
/* Re-enable pre-emption and return */
errout:
sched_unlock();
return ret;
}
/****************************************************************************
* Name: posix_spawn_proxy
*
* Description:
* Perform file_actions, then execute the task from the file system.
*
* Do we really need this proxy task? Isn't that wasteful?
*
* Q: Why not use a starthook so that there is callout from task_start()
* to perform these operations after the file is loaded from
* the file system?
* A: That existing task_starthook() implementation cannot be used in
* this context; any of task_starthook() will also conflict with
* binfmt's use of the start hook to call C++ static initializers.
* task_restart() would also be an issue.
*
* Input Parameters:
* Standard task start-up parameters
*
* Returned Value:
* Standard task return value.
*
****************************************************************************/
static int posix_spawn_proxy(int argc, FAR char *argv[])
{
int ret;
/* Perform file actions and/or set a custom signal mask. We get here only
* if the file_actions parameter to posix_spawn[p] was non-NULL and/or the
* option to change the signal mask was selected.
*/
#ifndef CONFIG_DISABLE_SIGNALS
DEBUGASSERT(g_spawn_parms.file_actions ||
(g_spawn_parms.attr &&
(g_spawn_parms.attr->flags & POSIX_SPAWN_SETSIGMASK) != 0));
#else
DEBUGASSERT(g_spawn_parms.file_actions);
#endif
/* Set the attributes and perform the file actions as appropriate */
ret = spawn_proxyattrs(g_spawn_parms.attr, g_spawn_parms.file_actions);
if (ret == OK)
{
/* Start the task */
ret = posix_spawn_exec(g_spawn_parms.pid, g_spawn_parms.u.posix.path,
g_spawn_parms.attr, g_spawn_parms.argv);
#ifdef CONFIG_SCHED_HAVE_PARENT
if (ret == OK)
{
/* Change of the parent of the task we just spawned to our parent.
* What should we do in the event of a failure?
*/
int tmp = task_reparent(0, *g_spawn_parms.pid);
if (tmp < 0)
{
serr("ERROR: task_reparent() failed: %d\n", tmp);
}
}
#endif
}
/* Post the semaphore to inform the parent task that we have completed
* what we need to do.
*/
g_spawn_parms.result = ret;
#ifndef CONFIG_SCHED_WAITPID
spawn_semgive(&g_spawn_execsem);
#endif
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: posix_spawn
*
* Description:
* The posix_spawn() and posix_spawnp() functions will create a new,
* child task, constructed from a regular executable file.
*
* Input Parameters:
*
* pid - Upon successful completion, posix_spawn() and posix_spawnp() will
* return the task ID of the child task to the parent task, in the
* variable pointed to by a non-NULL 'pid' argument. If the 'pid'
* argument is a null pointer, the process ID of the child is not
* returned to the caller.
*
* path - The 'path' argument to posix_spawn() is the absolute path that
* identifies the file to execute. The 'path' argument to posix_spawnp()
* may also be a relative path and will be used to construct a pathname
* that identifies the file to execute. In the case of a relative path,
* the path prefix for the file will be obtained by a search of the
* directories passed as the environment variable PATH.
*
* NOTE: NuttX provides only one implementation: If
* CONFIG_BINFMT_EXEPATH is defined, then only posix_spawnp() behavior
* is supported; otherwise, only posix_spawn behavior is supported.
*
* file_actions - If 'file_actions' is a null pointer, then file
* descriptors open in the calling process will remain open in the
* child process (unless CONFIG_FDCLONE_STDIO is defined). If
* 'file_actions' is not NULL, then the file descriptors open in the
* child process will be those open in the calling process as modified
* by the spawn file actions object pointed to by file_actions.
*
* attr - If the value of the 'attr' parameter is NULL, the all default
* values for the POSIX spawn attributes will be used. Otherwise, the
* attributes will be set according to the spawn flags. The
* posix_spawnattr_t spawn attributes object type is defined in spawn.h.
* It will contains these attributes, not all of which are supported by
* NuttX:
*
* - POSIX_SPAWN_SETPGROUP: Setting of the new task's process group is
* not supported. NuttX does not support process groups.
* - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
* value.
* - POSIX_SPAWN_SETSCHEDULER: Set the new task's scheduler policy to
* the sched_policy value.
* - POSIX_SPAWN_RESETIDS: Resetting of the effective user ID of the child
* process is not supported. NuttX does not support effective user
* IDs.
* - POSIX_SPAWN_SETSIGMASK: Set the new task's signal mask.
* - POSIX_SPAWN_SETSIGDEF: Resetting signal default actions is not
* supported. NuttX does not support default signal actions.
*
* argv - argv[] is the argument list for the new task. argv[] is an
* array of pointers to null-terminated strings. The list is terminated
* with a null pointer.
*
* envp - The envp[] argument is not used by NuttX and may be NULL. In
* standard implementations, envp[] is an array of character pointers to
* null-terminated strings that provide the environment for the new
* process image. The environment array is terminated by a null pointer.
* In NuttX, the envp[] argument is ignored and the new task will simply
* inherit the environment of the parent task.
*
* Returned Value:
* posix_spawn() and posix_spawnp() will return zero on success.
* Otherwise, an error number will be returned as the function return
* value to indicate the error:
*
* - EINVAL: The value specified by 'file_actions' or 'attr' is invalid.
* - Any errors that might have been return if vfork() and excec[l|v]()
* had been called.
*
* Assumptions/Limitations:
* - NuttX provides only posix_spawn() or posix_spawnp() behavior
* depending upon the setting of CONFIG_BINFMT_EXEPATH: If
* CONFIG_BINFMT_EXEPATH is defined, then only posix_spawnp() behavior
* is supported; otherwise, only posix_spawn behavior is supported.
* - The 'envp' argument is not used and the 'environ' variable is not
* altered (NuttX does not support the 'environ' variable).
* - Process groups are not supported (POSIX_SPAWN_SETPGROUP).
* - Effective user IDs are not supported (POSIX_SPAWN_RESETIDS).
* - Signal default actions cannot be modified in the newly task executed
* because NuttX does not support default signal actions
* (POSIX_SPAWN_SETSIGDEF).
*
* POSIX Compatibility
* - The value of the argv[0] received by the child task is assigned by
* NuttX. For the caller of posix_spawn(), the provided argv[0] will
* correspond to argv[1] received by the new task.
*
****************************************************************************/
#ifdef CONFIG_BINFMT_EXEPATH
int posix_spawnp(FAR pid_t *pid, FAR const char *path,
FAR const posix_spawn_file_actions_t *file_actions,
FAR const posix_spawnattr_t *attr,
FAR char *const argv[], FAR char *const envp[])
#else
int posix_spawn(FAR pid_t *pid, FAR const char *path,
FAR const posix_spawn_file_actions_t *file_actions,
FAR const posix_spawnattr_t *attr,
FAR char *const argv[], FAR char *const envp[])
#endif
{
struct sched_param param;
pid_t proxy;
#ifdef CONFIG_SCHED_WAITPID
int status;
#endif
int ret;
DEBUGASSERT(path);
sinfo("pid=%p path=%s file_actions=%p attr=%p argv=%p\n",
pid, path, file_actions, attr, argv);
/* If there are no file actions to be performed and there is no change to
* the signal mask, then start the new child task directly from the parent task.
*/
#ifndef CONFIG_DISABLE_SIGNALS
if ((file_actions == NULL || *file_actions == NULL) &&
(attr == NULL || (attr->flags & POSIX_SPAWN_SETSIGMASK) == 0))
#else
if (file_actions == NULL || *file_actions == NULL)
#endif
{
return posix_spawn_exec(pid, path, attr, argv);
}
/* Otherwise, we will have to go through an intermediary/proxy task in order
* to perform the I/O redirection. This would be a natural place to fork().
* However, true fork() behavior requires an MMU and most implementations
* of vfork() are not capable of these operations.
*
* Even without fork(), we can still do the job, but parameter passing is
* messier. Unfortunately, there is no (clean) way to pass binary values
* as a task parameter, so we will use a semaphore-protected global
* structure.
*/
/* Get exclusive access to the global parameter structure */
spawn_semtake(&g_spawn_parmsem);
/* Populate the parameter structure */
g_spawn_parms.result = ENOSYS;
g_spawn_parms.pid = pid;
g_spawn_parms.file_actions = file_actions ? *file_actions : NULL;
g_spawn_parms.attr = attr;
g_spawn_parms.argv = argv;
g_spawn_parms.u.posix.path = path;
/* Get the priority of this (parent) task */
ret = sched_getparam(0, &param);
if (ret < 0)
{
int errcode = get_errno();
serr("ERROR: sched_getparam failed: %d\n", errcode);
spawn_semgive(&g_spawn_parmsem);
return errcode;
}
/* Disable pre-emption so that the proxy does not run until waitpid
* is called. This is probably unnecessary since the posix_spawn_proxy has
* the same priority as this thread; it should be schedule behind this
* task in the ready-to-run list.
*/
#ifdef CONFIG_SCHED_WAITPID
sched_lock();
#endif
/* Start the intermediary/proxy task at the same priority as the parent
* task.
*/
proxy = kernel_thread("posix_spawn_proxy", param.sched_priority,
CONFIG_POSIX_SPAWN_PROXY_STACKSIZE,
(main_t)posix_spawn_proxy,
(FAR char * const *)NULL);
if (proxy < 0)
{
ret = get_errno();
serr("ERROR: Failed to start posix_spawn_proxy: %d\n", ret);
goto errout_with_lock;
}
/* Wait for the proxy to complete its job */
#ifdef CONFIG_SCHED_WAITPID
ret = waitpid(proxy, &status, 0);
if (ret < 0)
{
serr("ERROR: waitpid() failed: %d\n", errno);
goto errout_with_lock;
}
#else
spawn_semtake(&g_spawn_execsem);
#endif
/* Get the result and relinquish our access to the parameter structure */
ret = g_spawn_parms.result;
errout_with_lock:
#ifdef CONFIG_SCHED_WAITPID
sched_unlock();
#endif
spawn_semgive(&g_spawn_parmsem);
return ret;
}
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