/*-
 * 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/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <errno.h>
#include <libelf.h>
#include <stdlib.h>
#include <unistd.h>

#include "_libelf.h"

#if     ELFTC_HAVE_MMAP
#include <sys/mman.h>
#endif

ELFTC_VCSID("$Id: libelf_open.c,v 1.1 2019/02/01 05:27:38 jsg Exp $");

#define _LIBELF_INITSIZE        (64*1024)

/*
 * Read from a device file, pipe or socket.
 */
static void *
_libelf_read_special_file(int fd, size_t *fsz)
{
        ssize_t readsz;
        size_t bufsz, datasz;
        unsigned char *buf, *t;

        datasz = 0;
        readsz = 0;
        bufsz = _LIBELF_INITSIZE;
        if ((buf = malloc(bufsz)) == NULL)
                goto resourceerror;

        /*
         * Read data from the file descriptor till we reach EOF, or
         * till an error is encountered.
         */
        do {
                /* Check if we need to expand the data buffer. */
                if (datasz == bufsz) {
                        bufsz *= 2;
                        if ((t = realloc(buf, bufsz)) == NULL)
                                goto resourceerror;
                        buf = t;
                }

                do {
                        assert(bufsz - datasz > 0);
                        t = buf + datasz;
                        if ((readsz = read(fd, t, bufsz - datasz)) <= 0)
                                break;
                        datasz += (size_t) readsz;
                } while (datasz < bufsz);

        } while (readsz > 0);

        if (readsz < 0) {
                LIBELF_SET_ERROR(IO, errno);
                goto error;
        }

        assert(readsz == 0);

        /*
         * Free up extra buffer space.
         */
        if (bufsz > datasz) {
                if (datasz > 0) {
                        if ((t = realloc(buf, datasz)) == NULL)
                                goto resourceerror;
                        buf = t;
                } else {        /* Zero bytes read. */
                        LIBELF_SET_ERROR(ARGUMENT, 0);
                        free(buf);
                        buf = NULL;
                }
        }

        *fsz = datasz;
        return (buf);

resourceerror:
        LIBELF_SET_ERROR(RESOURCE, 0);
error:
        if (buf != NULL)
                free(buf);
        return (NULL);
}

/*
 * Read the contents of the file referenced by the file descriptor
 * 'fd'.
 */

Elf *
_libelf_open_object(int fd, Elf_Cmd c, int reporterror)
{
        Elf *e;
        void *m;
        mode_t mode;
        size_t fsize;
        struct stat sb;
        unsigned int flags;

        assert(c == ELF_C_READ || c == ELF_C_RDWR || c == ELF_C_WRITE);

        if (fstat(fd, &sb) < 0) {
                LIBELF_SET_ERROR(IO, errno);
                return (NULL);
        }

        mode = sb.st_mode;
        fsize = (size_t) sb.st_size;

        /*
         * Reject unsupported file types.
         */
        if (!S_ISREG(mode) && !S_ISCHR(mode) && !S_ISFIFO(mode) &&
            !S_ISSOCK(mode)) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        /*
         * For ELF_C_WRITE mode, allocate and return a descriptor.
         */
        if (c == ELF_C_WRITE) {
                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;
                        if (!S_ISREG(mode))
                                e->e_flags |= LIBELF_F_SPECIAL_FILE;
                }

                return (e);
        }


        /*
         * ELF_C_READ and ELF_C_RDWR mode.
         */
        m = NULL;
        flags = 0;
        if (S_ISREG(mode)) {

                /*
                 * Reject zero length files.
                 */
                if (fsize == 0) {
                        LIBELF_SET_ERROR(ARGUMENT, 0);
                        return (NULL);
                }

#if     ELFTC_HAVE_MMAP
                /*
                 * Always map regular files in with 'PROT_READ'
                 * permissions.
                 *
                 * For objects opened in ELF_C_RDWR mode, when
                 * elf_update(3) is called, we remove this mapping,
                 * write file data out using write(2), and map the new
                 * contents back.
                 */
                m = mmap(NULL, fsize, PROT_READ, MAP_PRIVATE, fd, (off_t) 0);

                if (m == MAP_FAILED)
                        m = NULL;
                else
                        flags = LIBELF_F_RAWFILE_MMAP;
#endif

                /*
                 * Fallback to a read() if the call to mmap() failed,
                 * or if mmap() is not available.
                 */
                if (m == NULL) {
                        if ((m = malloc(fsize)) == NULL) {
                                LIBELF_SET_ERROR(RESOURCE, 0);
                                return (NULL);
                        }

                        if (read(fd, m, fsize) != (ssize_t) fsize) {
                                LIBELF_SET_ERROR(IO, errno);
                                free(m);
                                return (NULL);
                        }

                        flags = LIBELF_F_RAWFILE_MALLOC;
                }
        } else if ((m = _libelf_read_special_file(fd, &fsize)) != NULL)
                flags = LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE;
        else
                return (NULL);

        if ((e = _libelf_memory(m, fsize, reporterror)) == NULL) {
                assert((flags & LIBELF_F_RAWFILE_MALLOC) ||
                    (flags & LIBELF_F_RAWFILE_MMAP));
                if (flags & LIBELF_F_RAWFILE_MALLOC)
                        free(m);
#if     ELFTC_HAVE_MMAP
                else
                        (void) munmap(m, fsize);
#endif
                return (NULL);
        }

        /* ar(1) archives aren't supported in RDWR mode. */
        if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
                (void) elf_end(e);
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

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

        return (e);
}