Hi
? If an ISA simulator is used, how could we do the same way as to the
remote target in order to keep track of communication between GDB and
the inferior ISA?
Thanks
--Xinan
-----Original Message-----
From: gdb-owner@sources.redhat.com on behalf of Jim Ingham
Sent: Thu 9/30/2004 10:30 AM
To: gdb@sources.redhat.com
Subject: Re: breakpoint instruction isn't shown in disassemble or
examine (x) commands?
gdb will always hide the breakpoint trap from you, and show you the
instruction that is actually going to be run when you get to that pc
instead.? This is on purpose, it would be very confusing, and not at
all helpful, for folks to see trap instructions showing up in their
disassembly.
Is there some reason, other than curiosity, the leads you to want to
see the trap there?
If you are just curious, try running gdb with:
(gdb) set debug target 1
You can see gdb copy out the actual instruction and lay down the traps,
and lots of other things you may or may not want to know about...
Jim
On Sep 29, 2004, at 11:36 PM, gdb-digest-help@sources.redhat.com wrote:
>
>
> Hi,
>
> I am trying to understand the inner workings of a debugger and I
found
> a gdb behaviour that puzzles me.
>
> I understand that if I set a software breakpoint (as opposed to
> an hw breakpoint), gdb will insert an architecture-dependent
> instruction
> in the .text section that will cause an exception, that will be
handled
> by gdb.
>
> I am using gdb 6.1.1 on FreeBSD i386, so looking at the gdb source,
> the i386 has the breakpoint instruction 0xcc.
>
> I tought of doing something like (in various incantations):
>
> (gdb) disassemble foo
> (gdb) break foo
> (gdb) disassemble foo
>
> and was expecting of seeing the 0xcc instruction in the output of
> the second disassemble command; instead the output is the same
> as the first disassemble. Same results with the x command.
> It seems that gdb wants to "protect" me from seing that the
executable
> is changed?
>
> Finally I came up with a function that scans the .text section of
> the same program (a sort of very naive debugger detector)
> and hex dumps it. I ran the same program with and without
> breakpoint and my scan function works as expected: when the
breakpoint
> is
> set I see it in the hex dump.
>
> So somehow I have my sanity back, but the question remains: how
> can I see the breakpoint instruction from gdb itself?
>
> thanks
> marco
> --
> panic("The moon has moved again.");
>