1. breakpoint at 0x000000000040cef6

(gdb) break *0x40CEF6
Breakpoint 1 at 0x40cef6
(gdb) run
Starting program: /path/to/executable
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, 0x000000000040cef6 in ?? ()
(gdb) x/4x $rdx
0x2a09690:	0x724a5bac	0xa90b86f0	0xff9d8546	0x9910582b

2. breakpoint at 0x000000000040cefe

(gdb) break *0x0040CEFE
Breakpoint 1 at 0x40cefe
(gdb) run
Starting program: /path/to/executable
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, 0x000000000040cefe in ?? ()
(gdb) x/4x $rdx
0x2a09690:	0x724a5bac	0xa90b86f0	0xff9d8546	0x9910582b