RE: [uml-devel] DDD 3.3.1 + UML_2.4.24 - can't debug

["Pedro Estrela" <pedro.estrela@inesc.pt>]

Hello, and thanks for your quick reply.

I've tried just as you said, but the problem remains the same.

Also, I've now switched to an environment where I can be root on host,
but the situation hasn't changed. 

///////////////////////////////////

However, I've managed successfully to attach linux to an already running
gdb:

1 - start "gdb linux"
2 - check its gdb pid
3 - start "linux root=<...> debug gdb-pid=<pid>"  
(the execution of linux stops very early)

4 - in gdb: do an "att 1" 
(gdb attaches to linux, and I can check breakpoints, list code, etc,
exactly as spawning an xterm + gdb.)

5 - in gdb: "c" to continue linux.

///////////////////////////////////

Back to my original problem: using ddd, with both "debug" or
"debug=parent" options the result is always this:

GNU DDD 3.3.1 (i686-pc-linux-gnu), by Dorothea L(gdb) run
ubd0=../Debian-3.0r0.ext2 debug gdb-pid=7343
Program received signal SIGTRAP, Trace/breakpoint trap.
0xa000b000 in _start () at af_packet.c:1900
/root/linux-2.4.24/net/packet/af_packet.c:1900:42852:beg:0xa000b000
(gdb) att 1
ptrace: Operation not permitted.
(gdb) c
The program is not being run.

///////////////////////////////////

A variation is that, if I don't try to "att 1", and do only "c" instead,
gives this result:

GNU DDD 3.3.1 (i686-pc-linux-gnu), by Dorothea L(gdb) run
ubd0=../Debian-3.0r0.ext2 debug gdb-pid=20877
Program received signal SIGTRAP, Trace/breakpoint trap.
0xa000b000 in _start () at af_packet.c:1900
/root/linux-2.4.24/net/packet/af_packet.c:1900:42852:beg:0xa000b000
(gdb) c
Checking for the skas3 patch in the host...not found
Checking for /proc/mm...not found
tracing thread pid = 20884
^C^C^C
<no response from uml linux>

As it can be seen, linux continues to boot, but hangs, and ddd's gdb
can't attach to it. In this situation, after closing ddd, it remains 2
linux and 1 gdb processes that must be killed with "killall -9 linux"

////////////////////////////////////

To be completely sure, I've started all over again, with the simplest
environment that I could do to check this problem:
1 - get linux 2.4.24
2 - patch it with uml-2.4.24-1
3 - compile it
4 - install latest uml_tools
5 - run "ddd linux"
6 - run program with options "udb0=<...> debug gdb-pid=<pid>"

In this situation, I would ask very politely if someone who have ddd
working to help me, possibly by recreating this simple environment, as
I'm totally stuck.

Thanks, 
Pedro Estrela



> > 1 - started "ddd linux" on the host
> > 2 - i've noted the gdb pid that ddd swapned
> > 3 - started program with arguments: "root=<my-root-fs> debug=parent
gdb-
> pid=<pid>"
> 
> Try with just
> 
>   root=<rootfs> debug gdb-pid=<pid>
> 
> Also try the same on a stand-alone GDB.
> 
> Regards
> Henrik





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