ext/libelf/libelf_ehdr.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.
 *
 * $FreeBSD: src/lib/libelf/libelf_ehdr.c,v 1.2 2006/12/25 02:22:22 jkoshy Exp $
 */

#include <assert.h>
#include "gelf.h"
#include "libelf.h"
#include <stdlib.h>

#include "_libelf.h"

/*
 * Retrieve counts for sections, phdrs and the section string table index
 * from section header #0 of the ELF object.
 */
static int
_libelf_load_extended(Elf *e, int ec, uint64_t shoff, uint16_t phnum,
    uint16_t strndx)
{
        Elf_Scn *scn;
        size_t fsz;
        void (*xlator)(char *_d, char *_s, size_t _c, int _swap);
        uint32_t shtype;

        assert(STAILQ_EMPTY(&e->e_u.e_elf.e_scn));

        fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, 1);
        assert(fsz > 0);

        if (e->e_rawsize < shoff + fsz) { /* raw file too small */
                LIBELF_SET_ERROR(HEADER, 0);
                return (0);
        }

        if ((scn = _libelf_allocate_scn(e, (size_t) 0)) == NULL)
                return (0);

        xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
        (*xlator)((char *) &scn->s_shdr, e->e_rawfile + shoff, (size_t) 1,
            e->e_byteorder != LIBELF_PRIVATE(byteorder));

#define	GET_SHDR_MEMBER(M) ((ec == ELFCLASS32) ? scn->s_shdr.s_shdr32.M : \
                scn->s_shdr.s_shdr64.M)

        if ((shtype = GET_SHDR_MEMBER(sh_type)) != SHT_NULL) {
                LIBELF_SET_ERROR(SECTION, 0);
                return (0);
        }

        e->e_u.e_elf.e_nscn = GET_SHDR_MEMBER(sh_size);
        e->e_u.e_elf.e_nphdr = (phnum != PN_XNUM) ? phnum :
            GET_SHDR_MEMBER(sh_info);
        e->e_u.e_elf.e_strndx = (strndx != SHN_XINDEX) ? strndx :
            GET_SHDR_MEMBER(sh_link);
#undef	GET_SHDR_MEMBER

        return (1);
}

#define	EHDR_INIT(E,SZ)	 do {						\
                Elf##SZ##_Ehdr *eh = (E);				\
                eh->e_ident[EI_MAG0] = ELFMAG0;				\
                eh->e_ident[EI_MAG1] = ELFMAG1;				\
                eh->e_ident[EI_MAG2] = ELFMAG2;				\
                eh->e_ident[EI_MAG3] = ELFMAG3;				\
                eh->e_ident[EI_CLASS] = ELFCLASS##SZ;			\
                eh->e_ident[EI_DATA]  = ELFDATANONE;			\
                eh->e_ident[EI_VERSION] = LIBELF_PRIVATE(version);	\
                eh->e_machine = EM_NONE;				\
                eh->e_type    = ELF_K_NONE;				\
                eh->e_version = LIBELF_PRIVATE(version);		\
        } while (0)

void *
_libelf_ehdr(Elf *e, int ec, int allocate)
{
        void *ehdr;
        size_t fsz, msz;
        uint16_t phnum, shnum, strndx;
        uint64_t shoff;
        void (*xlator)(char *_d, char *_s, size_t _c, int _swap);

        assert(ec == ELFCLASS32 || ec == ELFCLASS64);

        if (e == NULL || e->e_kind != ELF_K_ELF) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        if (e->e_class != ELFCLASSNONE && e->e_class != ec) {
                LIBELF_SET_ERROR(CLASS, 0);
                return (NULL);
        }

        if (e->e_version != EV_CURRENT) {
                LIBELF_SET_ERROR(VERSION, 0);
                return (NULL);
        }

        if (e->e_class == ELFCLASSNONE)
                e->e_class = ec;

        if (ec == ELFCLASS32)
                ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr32;
        else
                ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr64;

        if (ehdr != NULL)	/* already have a translated ehdr */
                return (ehdr);

        fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
        assert(fsz > 0);

        if (e->e_cmd != ELF_C_WRITE && e->e_rawsize < fsz) {
                LIBELF_SET_ERROR(HEADER, 0);
                return (NULL);
        }

        msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT);

        assert(msz > 0);

        if ((ehdr = calloc((size_t) 1, msz)) == NULL) {
                LIBELF_SET_ERROR(RESOURCE, 0);
                return (NULL);
        }

        if (ec == ELFCLASS32) {
                e->e_u.e_elf.e_ehdr.e_ehdr32 = ehdr;
                EHDR_INIT(ehdr,32);
        } else {
                e->e_u.e_elf.e_ehdr.e_ehdr64 = ehdr;
                EHDR_INIT(ehdr,64);
        }

        if (allocate)
                e->e_flags |= ELF_F_DIRTY;

        if (e->e_cmd == ELF_C_WRITE)
                return (ehdr);

        xlator = _libelf_get_translator(ELF_T_EHDR, ELF_TOMEMORY, ec);
        (*xlator)(ehdr, e->e_rawfile, (size_t) 1,
            e->e_byteorder != LIBELF_PRIVATE(byteorder));

        /*
         * If extended numbering is being used, read the correct
         * number of sections and program header entries.
         */
        if (ec == ELFCLASS32) {
                phnum = ((Elf32_Ehdr *) ehdr)->e_phnum;
                shnum = ((Elf32_Ehdr *) ehdr)->e_shnum;
                shoff = ((Elf32_Ehdr *) ehdr)->e_shoff;
                strndx = ((Elf32_Ehdr *) ehdr)->e_shstrndx;
        } else {
                phnum = ((Elf64_Ehdr *) ehdr)->e_phnum;
                shnum = ((Elf64_Ehdr *) ehdr)->e_shnum;
                shoff = ((Elf64_Ehdr *) ehdr)->e_shoff;
                strndx = ((Elf64_Ehdr *) ehdr)->e_shstrndx;
        }

        if (shnum >= SHN_LORESERVE ||
            (shoff == 0LL && (shnum != 0 || phnum == PN_XNUM ||
                strndx == SHN_XINDEX))) {
                LIBELF_SET_ERROR(HEADER, 0);
                return (NULL);
        }

        if (shnum != 0 || shoff == 0LL) { /* not using extended numbering */
                e->e_u.e_elf.e_nphdr = phnum;
                e->e_u.e_elf.e_nscn = shnum;
                e->e_u.e_elf.e_strndx = strndx;
        } else if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
                return (NULL);

        return (ehdr);
}