Retrieve symbol name of RELA in ELF executable - c

Question

I am trying to retrieve the symbol name of RELA jump slots found in an ELF executable. Using libElf, I have managed to retrieve the address of the RELA but still trying to figure out how to get the symbol(-name).
According to How can I get the symbol name in struct "Elf64_Rela", the symbol is stored in the DYNSYM section which I tried to query but without satisfying results.
Here is what I've got so far (a little dirty though):
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <libelf.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <gelf.h>
#define LIB_PATH "/tmp/a.out"
int main(void)
{
int fd = open(LIB_PATH, O_RDONLY);
Elf *elf;
Elf_Scn *scn;
Elf_Data *rela_data = NULL;
Elf_Data *sym_data = NULL;
GElf_Shdr shdr_rela;
GElf_Shdr shdr_sym;
GElf_Rela rela;
GElf_Sym sym;
int count = 0;
elf_version(EV_CURRENT);
elf = elf_begin(fd, ELF_C_READ, NULL);
if (!elf)
fprintf(stderr, "ERROR: %s\n", elf_errmsg(elf_errno()));
for (scn = elf_getscn(elf, 0); scn; scn = elf_nextscn(elf, scn))
{
gelf_getshdr(scn, &shdr_sym);
if (shdr_sym.sh_type == SHT_DYNSYM)
break;
}
sym_data = elf_getdata(scn, sym_data);
for (scn = elf_getscn(elf, 0); scn; scn = elf_nextscn(elf, scn))
{
gelf_getshdr(scn, &shdr_rela);
if (shdr_rela.sh_type == SHT_RELA)
break;
}
scn = elf_nextscn(elf, scn);
gelf_getshdr(scn, &shdr_rela);
rela_data = elf_getdata(scn, rela_data);
for (unsigned int it = 0; it < (shdr_rela.sh_size / shdr_rela.sh_entsize); ++it)
{
gelf_getrela(rela_data, it, &rela);
gelf_getsym(sym_data, GELF_R_SYM(rela.r_info), &sym);
printf("[%-8p]: (%d) %s\n", rela.r_offset, GELF_R_SYM(rela.r_info), elf_strptr(elf, shdr_rela.sh_link, sym.st_shndx));
}
elf_end(elf);
close(fd);
return 0;
}
How can I retrieve the name of the RELA present in my ELF executable ?

Answer 1

There are two incorrect arguments in the call to elf_strptr(). To find the symbol names, use:
elf_strptr(elf, shdr_sym.sh_link, sym.st_name)
Explanation: the names are in the dynsym section (shdr_sym), not the rela section, and the index of the name is identified by the field st_name not st_shndx.
This answer is obviously too late to be useful for the OP, but may be of interest to others trying to do the same.