pop an address from the stack..

GDB shows retq instruction

(gdb) disassemble
Dump of assembler code for function __read_nocancel:
   0x00007fbd743e0e89 :	mov    $0x0,%eax
   0x00007fbd743e0e8e :	syscall
=> 0x00007fbd743e0e90 :	cmp    $0xfffffffffffff001,%rax
   0x00007fbd743e0e96 :	jae    0x7fbd743e0ec9 
   0x00007fbd743e0e98 :	retq
End of assembler dump.
(gdb)

Process Involved

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GS>

Explanation

retq = pop an address from the stack and go to that address.
it is an AMD64 instruction.


source : people.freebsd.org/~lstewart/references/amd64.pdf
source : http://www.powerbasic.com/support/help/pbwin/html/
          Opcodes_and_Mnemonics.htm