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Copyright (c) 2004, Sun Microsystems, Inc., All Rights Reserved
The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
gelf, gelf_checksum, gelf_fsize, gelf_getcap, gelf_getclass, gelf_getdyn, gelf_getehdr, gelf_getmove, gelf_getphdr, gelf_getrel, gelf_getrela, gelf_getshdr, gelf_getsym, gelf_getsyminfo, gelf_getsymshndx, gelf_newehdr, gelf_newphdr, gelf_update_cap, gelf_update_dyn, gelf_update_ehdr, gelf_update_getmove, gelf_update_move, gelf_update_phdr, gelf_update_rel, gelf_update_rela, gelf_update_shdr, gelf_update_sym, gelf_update_symshndx, gelf_update_syminfo, gelf_xlatetof, gelf_xlatetom - generic class-independent ELF interface

cc [ flag... ] file... -lelf [ library... ]
#include <gelf.h>

long gelf_checksum(Elf *elf);

size_t gelf_fsize(Elf *elf, Elf_Type type, size_t cnt, unsigned ver);

int gelf_getcap(Elf_Data *src, int ndx, GElf_Cap *dst);

int gelf_getclass(Elf *elf);

GElf_Dyn *gelf_getdyn(Elf_Data *src, int ndx, GElf_Dyn *dst);

GElf_Ehdr *gelf_getehdr(Elf *elf, GElf_Ehdr *dst);

GElf_Move *gelf_getmove(Elf_Data *src, int ndx, GElf_Move *dst);

GElf_Phdr *gelf_getphdr(Elf *elf, int ndx, GElf_Phdr *dst);

GElf_Rel *gelf_getrel(Elf_Data *src, int ndx, GElf_Rel *dst);

GElf_Rela *gelf_getrela(Elf_Data *src, int ndx, GElf_Rela *dst);

GElf_Shdr *gelf_getshdr(Elf_Scn *scn, GElf_Shdr *dst);

GElf_Sym *gelf_getsym(Elf_Data *src, int ndx, GElf_Sym *dst);

GElf_Syminfo *gelf_getsyminfo(Elf_Data *src, int ndx, GElf_Syminfo *dst);

GElf_Sym *gelf_getsymshndx(Elf_Data *symsrc, Elf_Data *shndxsrc,
 int ndx, GElf_Sym *symdst, Elf32_Word *shndxdst);

unsigned long gelf_newehdr(Elf *elf, int class);

unsigned long gelf_newphdr(Elf *elf, size_t phnum);

int gelf_update_cap(Elf_Data *dst, int ndx, GElf_Cap *src);

int gelf_update_dyn(Elf_Data *dst, int ndx, GElf_Dyn *src);

int gelf_update_ehdr(Elf *elf, GElf_Ehdr *src);

int gelf_update_move(Elf_Data *dst, int ndx, GElf_Move *src);

int gelf_update_phdr(Elf *elf, int ndx, GElf_Phdr *src);

int gelf_update_rel(Elf_Data *dst, int ndx, GElf_Rel *src);

int gelf_update_rela(Elf_Data *dst, int ndx, GElf_Rela *src);

int gelf_update_shdr(Elf_Scn *dst, GElf_Shdr *src);

int gelf_update_sym(Elf_Data *dst, int ndx, GElf_Sym *src);

int gelf_update_syminfo(Elf_Data *dst, int ndx, GElf_Syminfo *src);

int gelf_update_symshndx(Elf_Data *symdst, Elf_Data *shndxdst, int ndx,
 GElf_Sym *symsrc, Elf32_Word shndxsrc);

Elf_Data *gelf_xlatetof(Elf *elf, Elf_Data *dst, const Elf_Data *src,
 unsigned encode);

Elf_Data *gelf_xlatetom(Elf *elf, Elf_Data *dst, const Elf_Data *src,
 unsigned encode);

GElf is a generic, ELF class-independent API for manipulating ELF object files. GElf provides a single, common interface for handling 32-bit and 64-bit ELF format object files. GElf is a translation layer between the application and the class-dependent parts of the ELF library. Thus, the application can use GElf, which in turn, will call the corresponding elf32_ or elf64_ functions on behalf of the application. The data structures returned are all large enough to hold 32-bit and 64-bit data.

GElf provides a simple, class-independent layer of indirection over the class-dependent ELF32 and ELF64 API's. GElf is stateless, and may be used along side the ELF32 and ELF64 API's.

GElf always returns a copy of the underlying ELF32 or ELF64 structure, and therefore the programming practice of using the address of an ELF header as the base offset for the ELF's mapping into memory should be avoided. Also, data accessed by type-casting the Elf_Data buffer to a class-dependent type and treating it like an array, for example, a symbol table, will not work under GElf, and the gelf_get functions must be used instead. See the EXAMPLE section.

Programs that create or modify ELF files using libelf(3LIB) need to perform an extra step when using GElf. Modifications to GElf values must be explicitly flushed to the underlying ELF32 or ELF64 structures by way of the gelf_update_ interfaces. Use of elf_update or elf_flagelf and the like remains the same.

The sizes of versioning structures remain the same between ELF32 and ELF64. The GElf API only defines types for versioning, rather than a functional API. The processing of versioning information will stay the same in the GElf environment as it was in the class-dependent ELF environment.

gelf_checksum()

gelf_fsize()

gelf_getcap()

gelf_getclass()

gelf_getdyn()

gelf_getehdr()

gelf_getmove()

gelf_getphdr()

gelf_getrel()

gelf_getrela()

gelf_getshdr()

gelf_getsym()

gelf_getsyminfo()

gelf_getsymshndx()

gelf_newehdr()

gelf_newphdr()

gelf_update_cap()

gelf_update_dyn()

gelf_update_ehdr()

gelf_update_move()

gelf_update_phdr()

gelf_update_rel()

gelf_update_rela()

gelf_update_shdr()

gelf_update_sym()

gelf_update_syminfo()

gelf_update_symshndx()

gelf_xlatetof()

gelf_xlatetom()

Upon failure, all GElf functions return 0 and set elf_errno. See elf_errno(3ELF)

Example 1 Printing the ELF Symbol Table

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libelf.h>
#include <gelf.h>

void
main(int argc, char **argv)
{
 Elf *elf;
 Elf_Scn *scn = NULL;
 GElf_Shdr shdr;
 Elf_Data *data;
 int fd, ii, count;

 elf_version(EV_CURRENT);

 fd = open(argv[1], O_RDONLY);
 elf = elf_begin(fd, ELF_C_READ, NULL);

 while ((scn = elf_nextscn(elf, scn)) != NULL) {
 gelf_getshdr(scn, &shdr);
 if (shdr.sh_type == SHT_SYMTAB) {
 /* found a symbol table, go print it. */
 break;
 }
 }

 data = elf_getdata(scn, NULL);
 count = shdr.sh_size / shdr.sh_entsize;

 /* print the symbol names */
 for (ii = 0; ii < count; ++ii) {
 GElf_Sym sym;
 gelf_getsym(data, ii, &sym);
 printf("%s\en", elf_strptr(elf, shdr.sh_link, sym.st_name));
 }
 elf_end(elf);
 close(fd);
}

ELF Extended Sections are employed to allow an ELF file to contain more than 0xff00 (SHN_LORESERVE) section. See the Linker and Libraries Guide for more information.

/lib/libelf.so.1

/lib/64/libelf.so.1

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Stable
MT Level	MT-Safe

elf(3ELF), elf32_checksum(3ELF), elf32_fsize(3ELF), elf32_getehdr(3ELF), elf32_newehdr(3ELF), elf32_getphdr(3ELF), elf32_newphdr(3ELF), elf32_getshdr(3ELF), elf32_xlatetof(3ELF), elf32_xlatetom(3ELF), elf_errno(3ELF), libelf(3LIB), attributes(5)

Linker and Libraries Guide