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debugging a callq command


Hi,
Trying to debug an assembly code with gdb, I see that a call function to a valid address exists but the control won't go to the target address.

As you can see, the first instruction is a jmp to 0x7fffffffde7d and there, it will call 0x7fffffffde70. However, the next instruction is something else while the program receives seg fault.

(gdb) nexti
0x00007fffffffde6e in ?? ()
1: x/20i $pc
=> 0x7fffffffde6e:    jmp    0x7fffffffde7d
   0x7fffffffde70:    pop    %rsi
   0x7fffffffde71:    xor    %ecx,%ecx
   0x7fffffffde73:    mov    $0x21,%cl
   0x7fffffffde75:    xorb   $0x35,(%rsi)
   0x7fffffffde78:    rex.RX loop 0x7fffffffde75
   0x7fffffffde7b:    jmp    0x7fffffffde82
   0x7fffffffde7d:    callq  0x7fffffffde70
   0x7fffffffde82:    pop    %rdi
   0x7fffffffde83:    jae    0x7fffffffdef2
(gdb) nexti
0x00007fffffffde6e in ?? ()
1: x/20i $pc
=> 0x7fffffffde6e:    jmp    0x7fffffffde7d
   0x7fffffffde70:    pop    %rsi
   0x7fffffffde71:    xor    %ecx,%ecx
   0x7fffffffde73:    mov    $0x21,%cl
   0x7fffffffde75:    xorb   $0x35,(%rsi)
   0x7fffffffde78:    rex.RX loop 0x7fffffffde75
   0x7fffffffde7b:    jmp    0x7fffffffde82
   0x7fffffffde7d:    callq  0x7fffffffde70
   0x7fffffffde82:    pop    %rdi
   0x7fffffffde83:    jae    0x7fffffffdef2
(gdb) nexti

Program received signal SIGSEGV, Segmentation fault.
0x00007fffffffde8c in ?? ()
1: x/20i $pc
=> 0x7fffffffde8c:    out    %eax,$0x5f
   0x7fffffffde8e:    ds insl (%dx),%es:(%rdi)
   0x7fffffffde90:    addr32 pop %rbp
   0x7fffffffde92:    sbb    0x46(%rdi),%cl
   0x7fffffffde95:    pop    %rbp
   0x7fffffffde96:    pop    %rbp
   0x7fffffffde97:    sbb    0x5c(%rdi),%dl




What is happening there? Any idea?



Regards,
Mahmood

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