rot13-gdb

(gdb) disas rot
Dump of assembler code for function rot:
   0x0000000000000832 <+0>: push   rbp
   0x0000000000000833 <+1>: mov    rbp,rsp
   0x0000000000000836 <+4>: push   rbx
   0x0000000000000837 <+5>: sub    rsp,0x98
   0x000000000000083e <+12>:    mov    QWORD PTR [rbp-0x98],rdi
   0x0000000000000845 <+19>:    mov    DWORD PTR [rbp-0x9c],esi
   0x000000000000084b <+25>:    mov    rax,QWORD PTR fs:0x28
   0x0000000000000854 <+34>:    mov    QWORD PTR [rbp-0x18],rax
   0x0000000000000858 <+38>:    xor    eax,eax
   0x000000000000085a <+40>:    mov    DWORD PTR [rbp-0x8c],0x0
   0x0000000000000864 <+50>:    jmp    0x911 <rot+223>
   0x0000000000000869 <+55>:    mov    eax,DWORD PTR [rbp-0x8c]
   0x000000000000086f <+61>:    movsxd rdx,eax
   0x0000000000000872 <+64>:    mov    rax,QWORD PTR [rbp-0x98]
   0x0000000000000879 <+71>:    add    rax,rdx
   0x000000000000087c <+74>:    movzx  eax,BYTE PTR [rax]
   0x000000000000087f <+77>:    movsx  eax,al
   0x0000000000000882 <+80>:    mov    esi,eax
   0x0000000000000884 <+82>:    lea    rdi,[rip+0x200785]        # 0x201010 <alphabet>
   0x000000000000088b <+89>:    call   0x680 <strchr@plt>
   0x0000000000000890 <+94>:    mov    QWORD PTR [rbp-0x88],rax
   0x0000000000000897 <+101>:   cmp    QWORD PTR [rbp-0x88],0x0
   0x000000000000089f <+109>:   je     0x8e7 <rot+181>
   0x00000000000008a1 <+111>:   mov    rdx,QWORD PTR [rbp-0x88]
   0x00000000000008a8 <+118>:   lea    rax,[rip+0x200761]        # 0x201010 <alphabet>
   0x00000000000008af <+125>:   sub    rdx,rax
   0x00000000000008b2 <+128>:   mov    eax,DWORD PTR [rbp-0x9c]
   0x00000000000008b8 <+134>:   cdqe
   0x00000000000008ba <+136>:   add    rax,rdx
   0x00000000000008bd <+139>:   mov    rbx,rax
   0x00000000000008c0 <+142>:   lea    rdi,[rip+0x200749]        # 0x201010 <alphabet>
   0x00000000000008c7 <+149>:   call   0x660 <strlen@plt>
   0x00000000000008cc <+154>:   mov    rcx,rax
   0x00000000000008cf <+157>:   mov    rax,rbx
   0x00000000000008d2 <+160>:   mov    edx,0x0
   0x00000000000008d7 <+165>:   div    rcx
   0x00000000000008da <+168>:   lea    rax,[rip+0x20072f]        # 0x201010 <alphabet>
   0x00000000000008e1 <+175>:   movzx  eax,BYTE PTR [rdx+rax*1]
   0x00000000000008e5 <+179>:   jmp    0x8fd <rot+203>
   0x00000000000008e7 <+181>:   mov    eax,DWORD PTR [rbp-0x8c]
   0x00000000000008ed <+187>:   movsxd rdx,eax
   0x00000000000008f0 <+190>:   mov    rax,QWORD PTR [rbp-0x98]
   0x00000000000008f7 <+197>:   add    rax,rdx
   0x00000000000008fa <+200>:   movzx  eax,BYTE PTR [rax]
   0x00000000000008fd <+203>:   mov    edx,DWORD PTR [rbp-0x8c]
   0x0000000000000903 <+209>:   movsxd rdx,edx
   0x0000000000000906 <+212>:   mov    BYTE PTR [rbp+rdx*1-0x80],al
   0x000000000000090a <+216>:   add    DWORD PTR [rbp-0x8c],0x1
   0x0000000000000911 <+223>:   mov    eax,DWORD PTR [rbp-0x8c]
   0x0000000000000917 <+229>:   movsxd rbx,eax
   0x000000000000091a <+232>:   mov    rax,QWORD PTR [rbp-0x98]
   0x0000000000000921 <+239>:   mov    rdi,rax
   0x0000000000000924 <+242>:   call   0x660 <strlen@plt>
   0x0000000000000929 <+247>:   cmp    rbx,rax
   0x000000000000092c <+250>:   jb     0x869 <rot+55>
   0x0000000000000932 <+256>:   lea    rax,[rbp-0x80]
   0x0000000000000936 <+260>:   mov    rdi,rax
   0x0000000000000939 <+263>:   call   0x650 <puts@plt>
   0x000000000000093e <+268>:   nop
   0x000000000000093f <+269>:   mov    rax,QWORD PTR [rbp-0x18]
   0x0000000000000943 <+273>:   xor    rax,QWORD PTR fs:0x28
   0x000000000000094c <+282>:   je     0x953 <rot+289>
   0x000000000000094e <+284>:   call   0x670 <__stack_chk_fail@plt>
   0x0000000000000953 <+289>:   add    rsp,0x98
   0x000000000000095a <+296>:   pop    rbx
   0x000000000000095b <+297>:   pop    rbp
   0x000000000000095c <+298>:   ret
End of assembler dump.
(gdb) break *rot+260
Breakpoint 1 at 0x936: file ../rot.c, line 25.
(gdb) r rotations_are_cool 13
Starting program: /home/michael/Desktop/rotation rotations_are_cool 13

Breakpoint 1, 0x0000555555554936 in rot (
    t=0x7fffffffe2d2 "rotations_are_cool", r=13) at ../rot.c:25
25      printf("%s\n", result);
(gdb) x/s $rbp-0x80
0x7fffffffdde0: "ebgngvbaf_ner_pbby\377\367\377\177" <- Here is the strange data
(gdb) quit
A debugging session is active.

    Inferior 1 [process 27971] will be killed.

Quit anyway? (y or n) y