nuttx/libs/libc/unistd/lib_execv.c

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/****************************************************************************
* libs/libc/unistd/lib_execv.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 <unistd.h>
#ifdef CONFIG_LIBC_EXECFUNCS
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: execv
*
* Description:
* The standard 'exec' family of functions will replace the current process
* image with a new process image. The new image will be constructed from a
* regular, executable file called the new process image file. There will
* be no return from a successful exec, because the calling process image
* is overlaid by the new process image.
*
* Simplified 'execl()' and 'execv()' functions are provided by NuttX for
* compatibility. NuttX is a tiny embedded RTOS that does not support
* processes and hence the concept of overlaying a tasks process image with
* a new process image does not make any sense. In NuttX, these functions
* are wrapper functions that:
*
* 1. Call the non-standard binfmt function 'exec', and then
* 2. exit(0).
*
* Note the inefficiency when 'exec[l|v]()' is called in the normal, two-
* step process: (1) first call vfork() to create a new thread, then (2)
* call 'exec[l|v]()' to replace the new thread with a program from the
* file system. Since the new thread will be terminated by the
* 'exec[l|v]()' call, it really served no purpose other than to support
* Unix compatility.
*
* The non-standard binfmt function 'exec()' needs to have (1) a symbol
* table that provides the list of symbols exported by the base code, and
* (2) the number of symbols in that table. This information is currently
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* provided to 'exec()' from 'exec[l|v]()' via NuttX configuration
* settings:
*
* CONFIG_LIBC_EXECFUNCS : Enable exec[l|v] support
* CONFIG_EXECFUNCS_HAVE_SYMTAB : Defined if there is a pre-defined
* symbol table
* CONFIG_EXECFUNCS_SYMTAB_ARRAY : Symbol table name used by exec[l|v]
* CONFIG_EXECFUNCS_NSYMBOLS_VAR : Variable holding number of symbols
* in the table
*
* As a result of the above, the current implementations of 'execl()' and
* 'execv()' suffer from some incompatibilities that may or may not be
* addressed in a future version of NuttX. Other than just being an
* inefficient use of MCU resource, the most serious of these is that
* the exec'ed task will not have the same task ID as the vfork'ed
* function. So the parent function cannot know the ID of the exec'ed
* task.
*
* Input Parameters:
* path - The path to the program to be executed. If CONFIG_LIBC_ENVPATH
* is defined in the configuration, then this may be a relative path
* from the current working directory. Otherwise, path must be the
* absolute path to the program.
* argv - A pointer to an array of string arguments. The end of the
* array is indicated with a NULL entry.
*
* Returned Value:
* This function does not return on success. On failure, it will return
* -1 (ERROR) and will set the 'errno' value appropriately.
*
****************************************************************************/
int execv(FAR const char *path, FAR char * const argv[])
{
return execve(path, argv, NULL);
}
#endif /* CONFIG_LIBC_EXECFUNCS */