What is __i686.get_pc_thunk.bx? Why do we need this call?

Question

When I disassemble my small function, I happened to see this call

call   0xf60d2f47 <__i686.get_pc_thunk.bx>.

I have no clue why I need t

Answer 1

Adding more to the information by example:

Suppose after you do disass on gdb inside function startup, then you will find something like this:

0x012c17a3  :     call   0x12b2ce7 <__i686.get_pc_thunk.bx>
0x012c17a8 :     add    $0x10d6518,%ebx

Then after you have called __i686.get_pc_thunk.bx, register ebx will be populated by value 0x012c17a8, which is the address of next instruction.

You can read the function as get_pc(program counter).

I found this article very nice for better understanding:

https://www.technovelty.org/linux/plt-and-got-the-key-to-code-sharing-and-dynamic-libraries.html