Re: How to display instructions around the current instuction?

[Peng Yu <pengyu.ut@gmail.com>]

Hi Stefan,

> display/10i $rip-10
>
> I don't think x86-64 instructions have fixed width, so that won't
> always print the same number of instructions before the current one,
> but it's probably a good approximation.

Have you tried it? If $rip-5 is not right at the start of an
instruction, it does not even disassmble correctly. Please test your
recommendation before sending it out. It is not appropriate to waste
other people's time.

(gdb) 1: x/10i $rip-5
<error: No registers.>
(gdb) Temporary breakpoint 1 at 0x401134
Starting program: /mnt/macosx/pengy/mrrdir/test/gnu/gdb/cmd/display/main.exe

Temporary breakpoint 1, 0x0000000000401134 in main ()
1: x/10i $rip-5
   0x40112f <frame_dummy+15>:	add    BYTE PTR [rbp+0x48],dl
   0x401132 <main+2>:	mov    ebp,esp
=> 0x401134 <main+4>:	sub    rsp,0x10
   0x401138 <main+8>:	movabs rdi,0x402004
   0x401142 <main+18>:	mov    al,0x0
   0x401144 <main+20>:	call   0x401030 <printf@plt>
   0x401149 <main+25>:	xor    ecx,ecx
   0x40114b <main+27>:	mov    DWORD PTR [rbp-0x4],eax
   0x40114e <main+30>:	mov    eax,ecx
   0x401150 <main+32>:	add    rsp,0x10
(gdb) 0x0000000000401138 in main ()
1: x/10i $rip-5
   0x401133 <main+3>:	in     eax,0x48
   0x401135 <main+5>:	sub    esp,0x10
=> 0x401138 <main+8>:	movabs rdi,0x402004
   0x401142 <main+18>:	mov    al,0x0
   0x401144 <main+20>:	call   0x401030 <printf@plt>
   0x401149 <main+25>:	xor    ecx,ecx
   0x40114b <main+27>:	mov    DWORD PTR [rbp-0x4],eax
   0x40114e <main+30>:	mov    eax,ecx
   0x401150 <main+32>:	add    rsp,0x10
   0x401154 <main+36>:	pop    rbp
(gdb) 0x0000000000401142 in main ()
1: x/10i $rip-5
   0x40113d <main+13>:	add    BYTE PTR [rax],al
   0x40113f <main+15>:	add    BYTE PTR [rax],al
   0x401141 <main+17>:	add    BYTE PTR [rax-0x1181800],dh
   0x401147 <main+23>:	(bad)
   0x401148 <main+24>:	push   QWORD PTR [rcx]
   0x40114a <main+26>:	leave
   0x40114b <main+27>:	mov    DWORD PTR [rbp-0x4],eax
   0x40114e <main+30>:	mov    eax,ecx
   0x401150 <main+32>:	add    rsp,0x10
   0x401154 <main+36>:	pop    rbp

-- 
Regards,
Peng