[eresi-dev] Welcome to Eduardo + GOT[] question

[machi at0]

Julien,

thanks for your quick reply.
Actually, I am doing the following:

************************************************************
> cat test.c
int main(void)
{
  __asm__ __volatile__("int3");
}

> gcc -o test test.c -g

> gdb test
(gdb) x &_GLOBAL_OFFSET_TABLE_
0x6007e0 <_GLOBAL_OFFSET_TABLE_>:       0x00600638  <------------- OK
(gdb) r
Starting program: /tmp/test

Program received signal SIGTRAP, Trace/breakpoint trap.
main () at test.c:4
4       }
(gdb) x &_GLOBAL_OFFSET_TABLE_
0x21cf80:       Cannot access memory at address 0x21cf80  <------------- ??
(gdb) x _GLOBAL_OFFSET_TABLE_
Cannot access memory at address 0x21cf80
************************************************************



Sounds like the GOT address is changing somehow. I haven't more investigated
on that yet.

c0

On Tue, Sep 1, 2009 at 5:57 PM, Julien Vanegue <julien.vanegue at gmail.com>wrote:

> The _GLOBAL_OFFSET_TABLE is not a variable but a symbol. It points on the
> .got section. The address you mention is really strange, it looks like a
> relative address. Maybe you were looking at a .so file ? In that case, all
> addresses are relative and the base will be added at runtime, once the
> loader decided where the library will be mapped.
>
> Julien
>
> On Tue, Sep 1, 2009 at 3:09 AM, machi at0 <camoroz0 at gmail.com> wrote:
>
>> Hi guys,
>>
>> I'll profit of this email to welcome Eduardo.
>>
>> When I was hacking around with the GOT, I noticed that the
>> _GLOBAL_OFFSET_TABLE_ variable takes a fancy value in runtime (Something
>> like 0x1cef8). Is that normal or has it been added for security reasons ?
>>
>> Thanks,
>>
>> c0
>>
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>>
>
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