# add this to your .gdbinit file
define vdis
if $argc != 2
  help vdis
else
 set $_icount = $arg1
 set $_iptr = $arg0

while ( $_icount > 0 )
 x/2i $_iptr
 echo \033[1A
 echo \033[K
 set $_nbytes = ($_ - $_iptr)
 set $_bcount = 0
 while ( $_bcount < $_nbytes )
  printf "%02X ", *(unsigned char*)($_iptr + $_bcount)
  set $_bcount++
 end
 printf "\n"
 set $_iptr = $_iptr + $_nbytes
 set $_icount--
end
end
end

document vdis
Verbose Display of Disassembly mnemonics with machine code bytes 
Usage: vdis address number
Example: 
(gdb) vdis $pc 3
0x400c30 <main>:	push   %rbx
53 
0x400c31 <main+1>:	sub    $0x20,%rsp
48 83 EC 20 
0x400c35 <main+5>:	mov    0x200604(%rip),%rax        # 0x601240
48 8B 05 04 06 20 00 
end

# Init parameters
#set output-radix 0x10
#set input-radix 0x10
#set disassembly-flavor intel
set disassembly-flavor att