getting virtual memory address(vma) of linker symbols - c

Question

I'm playing around the bfd library (<bfd.h>), and I was able to implement my own version of objdump -h on binary files by printing out sections, their vmas, size, etc. Now, I'm having trouble implementing nm. I'm able to use the bfd library to obtain all the different symbols of a binary executable file, but how can I get each symbol's (main, etc) vma using asection/asymbol struct data? Here's the code I have that prints out every symbol name:
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <bfd.h>
int main(int argc, char *argv[])
{
bfd *ibfd = NULL;
if (!argv[1])
{
printf("Please supply a second argument\n");
return -1;
}
else
{
// initialize bfd so we can use it
bfd_init();
// open the supplied argument file
const char *str = argv[1];
ibfd = bfd_openr(str, "elf64-x86-64");
// if issue opening
if (!ibfd)
{
bfd_perror("open failure\n");
return -1;
}
// if file isnt elf binary file
if (!bfd_check_format(ibfd, bfd_object))
{
printf("not an object file\n");
return -1;
}
int spaceNeeded = bfd_get_symtab_upper_bound(ibfd);
if (spaceNeeded < 0)
{
return -1;
}
else if (spaceNeeded == 0)
{
return 1;
}
asymbol **symTable = malloc(spaceNeeded);
long numSyms = bfd_canonicalize_symtab(ibfd, symTable);
if (numSyms < 0)
return -1;
for (int i = 0, count = 0; i < numSyms; i++)
{
printf("%s\n", symTable[i]->name);
}
bfd_close(ibfd);
}
// success code
return 1;
}

Answer 1

nm uses the function bfd_symbol_info to fetch the virtual memory addresses of the symbols. You can read the source code for that function to get an idea as to the implementation.
void
bfd_symbol_info (symbol, ret)
asymbol *symbol;
symbol_info *ret;
{
ret->type = bfd_decode_symclass (symbol);
if (bfd_is_undefined_symclass (ret->type))
ret->value = 0;
else
ret->value = symbol->value + symbol->section->vma;
ret->name = symbol->name;
}