/*      $NetBSD: elf_begin.c,v 1.5 2024/03/03 17:37:33 christos Exp $   */

/*-
* Copyright (c) 2006,2008-2011 Joseph Koshy
* All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/

#include <sys/cdefs.h>

#include <libelf.h>

#include "_libelf.h"

__RCSID("$NetBSD: elf_begin.c,v 1.5 2024/03/03 17:37:33 christos Exp $");
ELFTC_VCSID("Id: elf_begin.c 3977 2022-05-01 06:45:34Z jkoshy");

Elf *
elf_begin(int fd, Elf_Cmd c, Elf *a)
{
       Elf *e;

       e = NULL;

       if (LIBELF_PRIVATE(version) == EV_NONE) {
               LIBELF_SET_ERROR(SEQUENCE, 0);
               return (NULL);
       }

       switch (c) {
       case ELF_C_NULL:
               return (NULL);

       case ELF_C_WRITE:
               /*
                * The ELF_C_WRITE command is required to ignore the
                * descriptor passed in.
                */
               a = NULL;
               break;

       case ELF_C_RDWR:
               if (a != NULL) { /* not allowed for ar(1) archives. */
                       LIBELF_SET_ERROR(ARGUMENT, 0);
                       return (NULL);
               }
               /*FALLTHROUGH*/
       case ELF_C_READ:
               /*
                * Descriptor `a' could be for a regular ELF file, or
                * for an ar(1) archive.  If descriptor `a' was opened
                * using a valid file descriptor, we need to check if
                * the passed in `fd' value matches the original one.
                */
               if (a &&
                   ((a->e_fd != -1 && a->e_fd != fd) || c != a->e_cmd)) {
                       LIBELF_SET_ERROR(ARGUMENT, 0);
                       return (NULL);
               }
               break;

       default:
               LIBELF_SET_ERROR(ARGUMENT, 0);
               return (NULL);

       }

       if (a == NULL)
               e = _libelf_open_object(fd, c, 1);
       else if (a->e_kind == ELF_K_AR)
               e = _libelf_ar_open_member(a->e_fd, c, a);
       else
               (e = a)->e_activations++;

       return (e);
}