/*      $NetBSD: libelf_ehdr.c,v 1.5 2024/03/03 17:37:34 christos Exp $ */

/*-
* Copyright (c) 2006,2008 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.
*/

#if HAVE_NBTOOL_CONFIG_H
# include "nbtool_config.h"
#endif

#include <sys/cdefs.h>

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

#include "_libelf.h"

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

/*
* 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)
{
       size_t fsz;
       Elf_Scn *scn;
       uint32_t shtype;
       _libelf_translator_function *xlator;

       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 (shoff + fsz < shoff) {      /* Numeric overflow. */
               LIBELF_SET_ERROR(HEADER, 0);
               return (0);
       }

       if ((uint64_t) e->e_rawsize < shoff + fsz) {
               LIBELF_SET_ERROR(HEADER, 0);
               return (0);
       }

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

       if (shoff > SSIZE_MAX) {
               LIBELF_SET_ERROR(HEADER, 0);
               return (0);
       }

       xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
           _libelf_elfmachine(e));
       (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
           (unsigned char *) 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 (GET_SHDR_MEMBER(sh_size) > UINT_MAX) {
               LIBELF_SET_ERROR(HEADER, 0);
               return (0);
       }

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

       e->e_u.e_elf.e_nscn = (size_t) 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) & 0xFFU; \
               eh->e_machine = EM_NONE;                                \
               eh->e_type    = ELF_K_NONE;                             \
               eh->e_version = LIBELF_PRIVATE(version);                \
       } while (/* CONSTCOND */ 0)

void *
_libelf_ehdr(Elf *e, int ec, int allocate)
{
       void *ehdr;
       size_t fsz, msz;
       uint16_t phnum, shnum, strndx;
       uint64_t shoff;
       int (*xlator)(unsigned char *_d, size_t _dsz, unsigned 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 < (off_t) fsz) {
               LIBELF_SET_ERROR(HEADER, 0);
               return (NULL);
       }

       if ((msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT)) == 0)
               return (NULL);

       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,
           _libelf_elfmachine(e));
       (*xlator)((unsigned char*) ehdr, msz, e->e_rawfile, (size_t) 1,
           e->e_byteorder != LIBELF_PRIVATE(byteorder));

       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 extended numbering is being used, read the correct
        * number of sections and program header entries.
        */
       if ((shnum == 0 && shoff != 0) || phnum == PN_XNUM || strndx == SHN_XINDEX) {
               if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
                       return (NULL);
       } else {
               /* 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;
       }

       return (ehdr);
}

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