Re: need help to debug SIGSEGV in ssl3_get_message

[Michael Menge]

Quoting Martin Simmons <mar...@lispworks.com>:

On Thu, 25 Sep 2014 11:24:36 +0200, Michael Menge said:

Quoting Andy Polyakov <ap...@openssl.org>:

>>> in that case it crashes here:
>>>
>>>         if (s->msg_callback)
>>>                 s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
>>> s->init_buf->data, (size_t)s->init_num + 4, s, s->msg_callback_arg);
>>>
>>
>> So is the pointer to the callback wrong, or is the SIGSEGV in the
>> called function?
>
> What happens if you type just 'disass' at debugger prompt. Question is
> if you see meaningful code at point of failure, at 0x80e130 in original
> example. If you see meaningful instruction with reference to memory,
> issue even 'info reg'. If you don't see meaningful code, then it's
> likely that pointer to callback is wrong. In which case 'print $r10'
> would print address of failure. $r10 is because we already established
> that it was called with call *%r10.
>

(gdb) disass
No function contains program counter for selected frame.
(gdb) disass 0x000000000080e130
No function contains specified address.
(gdb) print $r10
$1 = 8446256

8446256 = 0x000000000080e130

so the pointer was wrong in the first place,
got changed or the function is not there anymore

I suggest you try 'x/16i 0x80e130' as well, because disass can report "No
function contains specified address." for an address that has no symbol
information, even if it contains code.

(gdb) x/16i 0x80e130
=> 0x80e130:    loopne 0x80e138
   0x80e132:    addl   $0x0,(%rax)
   0x80e138:    rclb   0x7e(%rdx)
   0x80e13b:    add    %al,(%rax)
   0x80e13d:    add    %al,(%rax)
   0x80e13f:    add    %dh,%al
   0x80e141:    push   %rdx
   0x80e142:    jle    0x80e144
   0x80e144:    add    %al,(%rax)
   0x80e146:    add    %al,(%rax)
   0x80e148:    add    %eax,(%rax)
   0x80e14a:    add    %al,(%rax)
   0x80e14c:    add    (%rax),%eax
   0x80e14e:    add    %al,(%rax)
   0x80e150:    orb    $0x0,0x0(%rax,%rax,4)
   0x80e158:    add    %al,(%rax)

You could also try 'info target' to see if gdb associates that address with
anything.

(gdb) info target
        [...]
        0x00000000007a3000 - 0x0000000000825000 is load4
        [...]


--------------------------------------------------------------------------------
M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912

Wächterstraße 76
72074 Tübingen

Zentrum für Datenverarbeitung mail: michael.me...@zdv.uni-tuebingen.de

smime.p7s
Description: S/MIME Signatur