/*checksum.c - implementation of the elf{32,64}_checksum(3) functions.Copyright (C) 1995 - 2001 Michael Riepe <michael@stud.uni-hannover.de>This library is free software; you can redistribute it and/ormodify it under the terms of the GNU Library General PublicLicense as published by the Free Software Foundation; eitherversion 2 of the License, or (at your option) any later version.This library is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNULibrary General Public License for more details.You should have received a copy of the GNU Library General PublicLicense along with this library; if not, write to the Free SoftwareFoundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.*/#include <private.h>#ifndef lintstatic const char rcsid[] = "@(#) $Id: checksum.c,v 1.3 2003/05/22 23:16:24 michael Exp $";#endif /* lint *//* * Compatibility note: * * The algorithm used in {elf32,elf64,gelf}_checksum() does not seem to * be documented.  I hope I got it right.  My implementation does the * following: * *   - skip sections that do not have the SHF_ALLOC flag set *   - skip sections of type SHT_NULL, SHT_NOBITS, SHT_DYNSYM and *     SHT_DYNAMIC *   - add all data bytes from the remaining sections, modulo 2**32 *   - add upper and lower half of the result *   - subtract 0xffff if the result is > 0xffff *   - if any error occurs, return 0L */static intskip_section(Elf_Scn *scn, unsigned cls) {    if (cls == ELFCLASS32) {	Elf32_Shdr *shdr = &scn->s_shdr32;	if (!(shdr->sh_flags & SHF_ALLOC)) {	    return 1;	}	switch (shdr->sh_type) {	    case SHT_NULL:	    case SHT_NOBITS:	    /* Solaris seems to ignore these, too */	    case SHT_DYNSYM:	    case SHT_DYNAMIC:		return 1;	}    }#if __LIBELF64    else if (cls == ELFCLASS64) {	Elf64_Shdr *shdr = &scn->s_shdr64;	if (!(shdr->sh_flags & SHF_ALLOC)) {	    return 1;	}	switch (shdr->sh_type) {	    case SHT_NULL:	    case SHT_NOBITS:	    /* Solaris seems to ignore these, too */	    case SHT_DYNSYM:	    case SHT_DYNAMIC:		return 1;	}    }#endif /* __LIBELF64 */    else {	seterr(ERROR_UNIMPLEMENTED);    }    return 0;}static longadd_bytes(unsigned char *ptr, size_t len) {    long csum = 0;    while (len--) {	csum += *ptr++;    }    return csum;}static long_elf_csum(Elf *elf) {    long csum = 0;    Elf_Data *data;    Elf_Scn *scn;    if (!elf->e_ehdr && !_elf_cook(elf)) {	/* propagate errors from _elf_cook */	return 0L;    }    seterr(0);    for (scn = elf->e_scn_1; scn; scn = scn->s_link) {	if (scn->s_index == SHN_UNDEF || skip_section(scn, elf->e_class)) {	    continue;	}	data = NULL;	while ((data = elf_getdata(scn, data))) {	    if (data->d_size) {		if (data->d_buf == NULL) {		    seterr(ERROR_NULLBUF);		    return 0L;		}		csum += add_bytes(data->d_buf, data->d_size);	    }	}    }    if (_elf_errno) {	return 0L;    }    csum = (csum & 0xffff) + ((csum >> 16) & 0xffff);    if (csum > 0xffff) {	csum -= 0xffff;    }    return csum;}longelf32_checksum(Elf *elf) {    if (elf) {	if (elf->e_kind != ELF_K_ELF) {	    seterr(ERROR_NOTELF);	}	else if (elf->e_class != ELFCLASS32) {	    seterr(ERROR_CLASSMISMATCH);	}	else {	    return _elf_csum(elf);	}    }    return 0L;}#if __LIBELF64longelf64_checksum(Elf *elf) {    if (elf) {	if (elf->e_kind != ELF_K_ELF) {	    seterr(ERROR_NOTELF);	}	else if (elf->e_class != ELFCLASS64) {	    seterr(ERROR_CLASSMISMATCH);	}	else {	    return _elf_csum(elf);	}    }    return 0L;}longgelf_checksum(Elf *elf) {    if (elf) {	if (elf->e_kind != ELF_K_ELF) {	    seterr(ERROR_NOTELF);	}	else if (!valid_class(elf->e_class)) {	    seterr(ERROR_UNKNOWN_CLASS);	}	else {	    return _elf_csum(elf);	}    }    return 0L;}#endif /* __LIBELF64 */