ext/libelf/elf_begin.c

/*-
 * Copyright (c) 2006 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/types.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <ar.h>
#include <ctype.h>
#include "libelf.h"

#include "_libelf.h"

static Elf *
_libelf_open_object(int fd, Elf_Cmd c)
{
        Elf *e;
        void *m;
        struct stat sb;

        /*
         * 'Raw' files are always mapped with 'PROT_READ'.  At
         * elf_update(3) time for files opened with ELF_C_RDWR the
         * mapping is unmapped, file data is written to using write(2)
         * and then the raw data is immediately mapped back in.
         */
        if (fstat(fd, &sb) < 0) {
                LIBELF_SET_ERROR(IO, errno);
                return (NULL);
        }

        m = NULL;
        if ((m = mmap(NULL, (size_t) sb.st_size, PROT_READ, MAP_PRIVATE, fd,
            (off_t) 0)) == MAP_FAILED) {
                LIBELF_SET_ERROR(IO, errno);
                return (NULL);
        }

        if ((e = elf_memory(m, (size_t) sb.st_size)) == NULL) {
                (void) munmap(m, (size_t) sb.st_size);
                return (NULL);
        }

        e->e_flags |= LIBELF_F_MMAP;
        e->e_fd = fd;
        e->e_cmd = c;

        if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
                (void) elf_end(e);
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        return (e);
}

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:

                if (a != NULL) { /* not allowed for ar(1) archives. */
                        LIBELF_SET_ERROR(ARGUMENT, 0);
                        return (NULL);
                }

                /*
                 * Check writeability of `fd' immediately and fail if
                 * not writeable.
                 */
                if (ftruncate(fd, (off_t) 0) < 0) {
                        LIBELF_SET_ERROR(IO, errno);
                        return (NULL);
                }

                if ((e = _libelf_allocate_elf()) != NULL) {
                        _libelf_init_elf(e, ELF_K_ELF);
                        e->e_byteorder = LIBELF_PRIVATE(byteorder);
                        e->e_fd = fd;
                        e->e_cmd = c;
                }
                return (e);

        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 (a && (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);
        else if (a->e_kind == ELF_K_AR)
                e = _libelf_ar_open_member(fd, c, a);
        else
                (e = a)->e_activations++;

        return (e);
}