/**************************************************************************** * sched/task/task_posixspawn.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 #include #include #include #include #include #include #include #include "sched/sched.h" #include "group/group.h" #include "task/spawn.h" #include "task/task.h" /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: nxposix_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_LIB_ENVPATH 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 nxposix_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_spawn(path, (FAR char * const *)argv, symtab, nsymbols, attr); if (pid < 0) { ret = -pid; 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) { spawn_execattrs(pid, attr); } /* Re-enable pre-emption and return */ errout: sched_unlock(); return ret; } /**************************************************************************** * Name: nxposix_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 nxtask_start() * to perform these operations after the file is loaded from * the file system? * A: That existing nxtask_starthook() implementation cannot be used in * this context; any of nxtask_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 nxposix_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. */ DEBUGASSERT(g_spawn_parms.file_actions || (g_spawn_parms.attr && (g_spawn_parms.attr->flags & POSIX_SPAWN_SETSIGMASK) != 0)); /* 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 = nxposix_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_LIB_ENVPATH 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_LIB_ENVPATH: If * CONFIG_LIB_ENVPATH 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_LIB_ENVPATH 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. */ if ((file_actions == NULL || *file_actions == NULL) && (attr == NULL || (attr->flags & POSIX_SPAWN_SETSIGMASK) == 0)) { return nxposix_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 */ ret = spawn_semtake(&g_spawn_parmsem); if (ret < 0) { serr("ERROR: spawn_semtake failed: %d\n", ret); return -ret; } /* 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 = nxsched_get_param(0, ¶m); if (ret < 0) { serr("ERROR: nxsched_get_param failed: %d\n", ret); spawn_semgive(&g_spawn_parmsem); return -ret; } /* Disable pre-emption so that the proxy does not run until waitpid * is called. This is probably unnecessary since the nxposix_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 = kthread_create("nxposix_spawn_proxy", param.sched_priority, CONFIG_POSIX_SPAWN_PROXY_STACKSIZE, (main_t)nxposix_spawn_proxy, (FAR char * const *)NULL); if (proxy < 0) { ret = -proxy; serr("ERROR: Failed to start nxposix_spawn_proxy: %d\n", ret); goto errout_with_lock; } /* Wait for the proxy to complete its job */ #ifdef CONFIG_SCHED_WAITPID /* REVISIT: This should not call waitpid() directly. waitpid is a * cancellation point and modifies the errno value. It is inappropriate * for use within the OS. */ ret = waitpid(proxy, &status, 0); if (ret < 0) { ret = -get_errno(); serr("ERROR: waitpid() failed: %d\n", ret); goto errout_with_lock; } #else ret = spawn_semtake(&g_spawn_execsem); if (ret < 0) { serr("ERROR: spawn_semtake() failed: %d\n", ret); goto errout_with_lock; } #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; }