194 lines
7.0 KiB
C
194 lines
7.0 KiB
C
/****************************************************************************
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* libc/unistd/lib_execl.c
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*
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* Copyright (C) 2013 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdarg.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#ifdef CONFIG_LIBC_EXECFUNCS
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* This is an artificial limit to detect error conditions where an argv[]
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* list is not properly terminated.
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*/
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#define MAX_EXECL_ARGS 256
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: execl
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*
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* Description:
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* The standard 'exec' family of functions will replace the current process
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* image with a new process image. The new image will be constructed from a
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* regular, executable file called the new process image file. There will
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* be no return from a successful exec, because the calling process image
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* is overlaid by the new process image.
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*
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* Simplified 'execl()' and 'execv()' functions are provided by NuttX for
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* compatibility. NuttX is a tiny embedded RTOS that does not support
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* processes and hence the concept of overlaying a tasks process image with
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* a new process image does not make any sense. In NuttX, these functions
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* are wrapper functions that:
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*
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* 1. Call the non-standard binfmt function 'exec', and then
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* 2. exit(0).
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*
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* Note the inefficiency when 'exec[l|v]()' is called in the normal, two-
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* step process: (1) first call vfork() to create a new thread, then (2)
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* call 'exec[l|v]()' to replace the new thread with a program from the
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* file system. Since the new thread will be terminated by the
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* 'exec[l|v]()' call, it really served no purpose other than to support
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* Unix compatility.
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*
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* The non-standard binfmt function 'exec()' needs to have (1) a symbol
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* table that provides the list of symbols exported by the base code, and
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* (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:
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*
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* CONFIG_LIBC_EXECFUNCS : Enable exec[l|v] support
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* CONFIG_EXECFUNCS_SYMTAB : Symbol table used by exec[l|v]
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* CONFIG_EXECFUNCS_NSYMBOLS : Number of symbols in the table
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*
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* As a result of the above, the current implementations of 'execl()' and
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* 'execv()' suffer from some incompatibilities that may or may not be
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* addressed in a future version of NuttX. Other than just being an
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* inefficient use of MCU resource, the most serious of these is that
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* the exec'ed task will not have the same task ID as the vfork'ed
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* function. So the parent function cannot know the ID of the exec'ed
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* task.
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*
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* Input Parameters:
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* path - The path to the program to be executed. If CONFIG_BINFMT_EXEPATH
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* is defined in the configuration, then this may be a relative path
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* from the current working directory. Otherwise, path must be the
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* absolute path to the program.
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* ... - A list of the string arguments to be recevied by the
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* program. Zero indicates the end of the list.
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*
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* Returned Value:
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* This function does not return on success. On failure, it will return
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* -1 (ERROR) and will set the 'errno' value appropriately.
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*
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****************************************************************************/
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int execl(FAR const char *path, ...)
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{
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FAR char **argv = (FAR char **)NULL;
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size_t nargs;
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va_list ap;
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int argc;
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int ret;
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/* Count the number of arguments */
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va_start(ap, path);
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for (nargs = 0, argc = 0; argv[argc]; argc++)
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{
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/* Increment the number of args. Here is a sanity check to prevent
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* running away with an unterminated argv[] list. MAX_EXECL_ARGS
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* should be sufficiently large that this never happens in normal
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* usage.
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*/
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if (++nargs > MAX_EXECL_ARGS)
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{
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set_errno(E2BIG);
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va_end(ap);
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return ERROR;
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}
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}
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va_end(ap);
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/* Allocate a temporary argv[] array */
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if (nargs > 0)
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{
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argv = (FAR char **)malloc((nargs + 1) * sizeof(FAR char *));
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if (argv == (FAR char **)NULL)
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{
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set_errno(ENOMEM);
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return ERROR;
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}
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/* Collect the arguments into the argv[] array */
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va_start(ap, path);
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for (argc = 0; argc < nargs; argc++)
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{
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argv[argc] = va_arg(ap, FAR char *);
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}
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argv[nargs] = NULL;
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va_end(ap);
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}
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/* Then let execv() do the real work */
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ret = execv(path, (FAR char * const *)argv);
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/* Free the allocated argv[] list */
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if (argv)
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{
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free(argv);
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}
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return ret;
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}
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#endif /* CONFIG_LIBC_EXECFUNCS */
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