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

/*-
* Copyright (c) 2006,2008-2010 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 <sys/queue.h>

#include <assert.h>
#include <errno.h>
#include <gelf.h>
#include <libelf.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>

#include "_libelf.h"

__RCSID("$NetBSD: elf_scn.c,v 1.5 2024/03/03 17:37:33 christos Exp $");

/*
* Load an ELF section table and create a list of Elf_Scn structures.
*/
int
_libelf_load_section_headers(Elf *e, void *ehdr)
{
       Elf_Scn *scn;
       uint64_t shoff;
       Elf32_Ehdr *eh32;
       Elf64_Ehdr *eh64;
       int ec, swapbytes;
       unsigned char *src;
       size_t fsz, i, shnum;
       _libelf_translator_function *xlator;

       assert(e != NULL);
       assert(ehdr != NULL);
       assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);

#define CHECK_EHDR(E,EH)        do {                            \
               uintmax_t rawsize = (uintmax_t) e->e_rawsize;   \
               if (shoff > (uintmax_t) e->e_rawsize ||         \
                   fsz != (EH)->e_shentsize ||                 \
                   shnum > SIZE_MAX / fsz ||                   \
                   fsz * shnum > rawsize - shoff) {            \
                       LIBELF_SET_ERROR(HEADER, 0);            \
                       return (0);                             \
               }                                               \
       } while (/* CONSTCOND */ 0)

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

       shnum = e->e_u.e_elf.e_nscn;

       if (ec == ELFCLASS32) {
               eh32 = (Elf32_Ehdr *) ehdr;
               shoff = (uint64_t) eh32->e_shoff;
               CHECK_EHDR(e, eh32);
       } else {
               eh64 = (Elf64_Ehdr *) ehdr;
               shoff = eh64->e_shoff;
               CHECK_EHDR(e, eh64);
       }

       xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
           _libelf_elfmachine(e));

       swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
       if (shoff > SSIZE_MAX) {
               LIBELF_SET_ERROR(HEADER, 0);
               return (0);
       }
       src = e->e_rawfile + (ssize_t)shoff;

       /*
        * If the file is using extended numbering then section #0
        * would have already been read in.
        */

       i = 0;
       if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
               assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
                   STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));

               i = 1;
               src += fsz;
       }

       for (; i < shnum; i++, src += fsz) {
               if ((scn = _libelf_allocate_scn(e, i)) == NULL)
                       return (0);

               (*xlator)((void *) &scn->s_shdr, sizeof(scn->s_shdr),
                   src, (size_t) 1, swapbytes);

               if (ec == ELFCLASS32) {
                       scn->s_offset = scn->s_rawoff =
                           scn->s_shdr.s_shdr32.sh_offset;
                       scn->s_size = scn->s_shdr.s_shdr32.sh_size;
               } else {
                       scn->s_offset = scn->s_rawoff =
                           scn->s_shdr.s_shdr64.sh_offset;
                       scn->s_size = scn->s_shdr.s_shdr64.sh_size;
               }
       }

       e->e_flags |= LIBELF_F_SHDRS_LOADED;

       return (1);
}


Elf_Scn *
elf_getscn(Elf *e, size_t index)
{
       int ec;
       void *ehdr;
       Elf_Scn *s;

       if (e == NULL || e->e_kind != ELF_K_ELF ||
           ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
               LIBELF_SET_ERROR(ARGUMENT, 0);
               return (NULL);
       }

       if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
               return (NULL);

       if (e->e_cmd != ELF_C_WRITE &&
           (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
           _libelf_load_section_headers(e, ehdr) == 0)
               return (NULL);

       STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
               if (s->s_ndx == index)
                       return (s);

       LIBELF_SET_ERROR(ARGUMENT, 0);
       return (NULL);
}

size_t
elf_ndxscn(Elf_Scn *s)
{
       if (s == NULL) {
               LIBELF_SET_ERROR(ARGUMENT, 0);
               return (SHN_UNDEF);
       }
       return (s->s_ndx);
}

Elf_Scn *
elf_newscn(Elf *e)
{
       int ec;
       void *ehdr;
       Elf_Scn *scn;

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

       if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
               LIBELF_SET_ERROR(CLASS, 0);
               return (NULL);
       }

       if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
               return (NULL);

       /*
        * The application may be asking for a new section descriptor
        * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
        * need to bring in the existing section information before
        * appending a new one to the list.
        *
        * Per the ELF(3) API, an application is allowed to open a
        * file using ELF_C_READ, mess with its internal structure and
        * use elf_update(...,ELF_C_NULL) to compute its new layout.
        */
       if (e->e_cmd != ELF_C_WRITE &&
           (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
           _libelf_load_section_headers(e, ehdr) == 0)
               return (NULL);

       if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
               assert(e->e_u.e_elf.e_nscn == 0);
               if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
                   NULL)
                       return (NULL);
               e->e_u.e_elf.e_nscn++;
       }

       assert(e->e_u.e_elf.e_nscn > 0);

       if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
               return (NULL);

       e->e_u.e_elf.e_nscn++;

       (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);

       return (scn);
}

Elf_Scn *
elf_nextscn(Elf *e, Elf_Scn *s)
{
       if (e == NULL || (e->e_kind != ELF_K_ELF) ||
           (s && s->s_elf != e)) {
               LIBELF_SET_ERROR(ARGUMENT, 0);
               return (NULL);
       }

       return (s == NULL ? elf_getscn(e, (size_t) 1) :
           STAILQ_NEXT(s, s_next));
}

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