Changing symbol in dynamic symbol table of shared library

Question

Suppose I have a library, for example, the following tmp.c:

extern int counter;


void increment_counter() {
  counter = counter + 1;
}

I can link it into a shared library, using the commands:

gcc -c -fPIC tmp.c -o tmp.o
gcc -shared -o libtmp.so tmp.o

This produces a shared library libtmp.so with the following dynamic symbol table:

objdump -TC libtmp.so 

libtmp.so:     file format elf64-x86-64

DYNAMIC SYMBOL TABLE:
0000000000000000  w   D  *UND*  0000000000000000  Base        _ITM_deregisterTMCloneTable
0000000000000000  w   D  *UND*  0000000000000000  Base        __gmon_start__
0000000000000000      D  *UND*  0000000000000000  Base        counter
0000000000000000  w   D  *UND*  0000000000000000  Base        _ITM_registerTMCloneTable
0000000000000000  w   DF *UND*  0000000000000000 (GLIBC_2.2.5) __cxa_finalize
00000000000010e9 g    DF .text  000000000000001c  Base        increment_counter

Great! Now I want to change the counter symbol from an undefined external symbol, to a symbol which points to a specific address (which I only know at runtime).

I actually know how to do this if I re-link the library with a linker script. If I have the following linker_script.ld:

counter = 0xabababababababab;

and I link with it, I will get the correct thing:

gcc -shared -o libtmp_with_script.so -T linker_script.ld tmp.o 
objdump -TC libtmp_with_script.so

libtmp_with_script.so:     file format elf64-x86-64

DYNAMIC SYMBOL TABLE:
0000000000000000  w   D  *UND*  0000000000000000  Base        _ITM_deregisterTMCloneTable
0000000000000000  w   D  *UND*  0000000000000000  Base        __gmon_start__
0000000000000000  w   D  *UND*  0000000000000000  Base        _ITM_registerTMCloneTable
0000000000000000  w   DF *UND*  0000000000000000 (GLIBC_2.2.5) __cxa_finalize
abababababababab g    D  *ABS*  0000000000000000  Base        counter
00000000000000c9 g    DF .text  000000000000001c  Base        increment_counter

What I'm wondering is: is there a way of doing this if I only have access to the .so file?

I.e., I want a command that will take libtmp.so and convert it into libtmp_with_script.so.