After elf is loaded into memory, how is the symbol table updated?

Hi, 


If I want to set a breakpoint on a function, I can read the elf file/dwarf to get the relative position of the function.


After entering the `run` command, how does gdb know the virtual address of the function, and when to update the symbol table, I did not find the relevant function;


For example, function 1: address 0x6aaf in the elf file
After run address function 1: address 0x55555556aaf


Who can give me a hint? 
Thank you so much;