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/****************************************************************************
* libc/unistd/lib_execl.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 <stdarg.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#ifdef CONFIG_LIBC_EXECFUNCS
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* This is an artificial limit to detect error conditions where an argv[]
* list is not properly terminated.
*/
#define MAX_EXECL_ARGS 256
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: execl
*
* 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
* provided to 'exec()' from 'exec[l|v]()' via NuttX configuration settings:
*
* CONFIG_LIBC_EXECFUNCS : Enable exec[l|v] support
* CONFIG_EXECFUNCS_SYMTAB : Symbol table used by exec[l|v]
* CONFIG_EXECFUNCS_NSYMBOLS : 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_BINFMT_EXEPATH
* 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.
* ... - A list of the string arguments to be recevied by the
* program. Zero indicates the end of the list.
*
* Returned Value:
* This function does not return on success. On failure, it will return
* -1 (ERROR) and will set the 'errno' value appropriately.
*
****************************************************************************/
int execl(FAR const char *path, ...)
{
FAR char **argv = (FAR char **)NULL;
size_t nargs;
va_list ap;
int argc;
int ret;
/* Count the number of arguments */
va_start(ap, path);
for (nargs = 0, argc = 0; argv[argc]; argc++)
{
/* Increment the number of args. Here is a sanity check to prevent
* running away with an unterminated argv[] list. MAX_EXECL_ARGS
* should be sufficiently large that this never happens in normal
* usage.
*/
if (++nargs > MAX_EXECL_ARGS)
{
set_errno(E2BIG);
return ERROR;
}
}
va_end(ap);
/* Allocate a temporary argv[] array */
if (nargs > 0)
{
argv = (FAR char **)malloc((nargs + 1) * sizeof(FAR char *));
if (argv == (FAR char **)NULL)
{
set_errno(ENOMEM);
return ERROR;
}
/* Collect the arguments into the argv[] array */
va_start(ap, path);
for (argc = 0; argc < nargs; argc++)
{
argv[argc] = va_arg(ap, FAR char *);
}
argv[nargs] = NULL;
va_end(ap);
}
/* Then let execv() do the real work */
ret = execv(path, (FAR char * const *)argv);
/* Free the allocated argv[] list */
if (argv)
{
free(argv);
}
return ret;
}
#endif /* CONFIG_LIBC_EXECFUNCS */
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