gdbserver "load" command

gdbserver "load" command

[Venkata Subbarao]

Hi,

I am trying to debug a i386 program using gdb. All I wanted to do is
to run gdbserver without the binary file and load the program using
"load" command. So following were the steps followed by me. I request
you to help me in this regard.

I have downloaded and installed GNU debugger. I ran the gdbserver as follows.

gdbserver --multi :9999


Then I ran the gdb client and tried to load the program using the
following command

gdb> target remote :9999
(This resulted in error The target is not running (try
extended-remote?). So I had to use the following command)
gdb> target extended-remote :9999
gdb> load

This printed following error.
Loading section .interp, size 0x13 lma 0x8048114
Load failed

I have following questions:

1) What is the difference between gdbserver and gdb stub ?
2) How can i load a program dynamically using "load" command in gdb ?

I kindly request you to help me in this regard.

Thanks in advance,

-- Subbarao.

Re: gdbserver "load" command

[Pedro Alves]

On Monday 17 May 2010 08:38:34, Venkata Subbarao wrote:

> 2) How can i load a program dynamically using "load" command in gdb ?

Use "run" instead.

-- 
Pedro Alves

Re: gdbserver "load" command

[Venkata Subbarao]

Sorry, But how can I run without loading the file.

I have tried with "remote put" and I have succeeded with it. But I
wanted to use "load" followed by "continue" command.

I am also curious to know what actually happens when we say "load"
command. Where does it dump the file contents ? I request you to
kindly help me.

Thanks in advance,
--Subbarao

On Mon, May 17, 2010 at 2:47 PM, Pedro Alves <pedro@codesourcery.com> wrote:
> On Monday 17 May 2010 08:38:34, Venkata Subbarao wrote:
>
>> 2) How can i load a program dynamically using "load" command in gdb ?
>
> Use "run" instead.
>
> --
> Pedro Alves
>

Re: gdbserver "load" command

[Pedro Alves]

On Tuesday 18 May 2010 16:05:17, Venkata Subbarao wrote:
> Sorry, But how can I run without loading the file.

You don't need to, and shouldn't use load when debugging
an unix like process.  "load" only makes sense for embedded
debugging --- it copies the program straight into the target's
memory.  When debugging on linux, or full blown OS, you want to 
create a new process, and that's what "run" does.

> I have tried with "remote put" and I have succeeded with it.

That's good.  After that, tell gdbserver which program to run
with "(gdb) set remote exec-file myprog".  Then you can just
type "run" to launch a new process, just like you were
debugging natively.

If you instead start gdbserver like so:

 $ gdbserver :9999 myprog

gdbserver will start the myprog program for you; This means
there'll already by a process running when you connect with
gdb.

> But I
> wanted to use "load" followed by "continue" command.

Don't.

> I am also curious to know what actually happens when we say "load"
> command. Where does it dump the file contents ?

To the debuggee/`inferior process' memory.  It doesn't make much sense
to use "load" when debugging a unix-like process.

-- 
Pedro Alves

Re: gdbserver "load" command

[Venkata Subbarao]

Thank you very much.

--Subbarao

On Tue, May 18, 2010 at 8:51 PM, Pedro Alves <pedro@codesourcery.com> wrote:
> On Tuesday 18 May 2010 16:05:17, Venkata Subbarao wrote:
>> Sorry, But how can I run without loading the file.
>
> You don't need to, and shouldn't use load when debugging
> an unix like process.  "load" only makes sense for embedded
> debugging --- it copies the program straight into the target's
> memory.  When debugging on linux, or full blown OS, you want to
> create a new process, and that's what "run" does.
>
>> I have tried with "remote put" and I have succeeded with it.
>
> That's good.  After that, tell gdbserver which program to run
> with "(gdb) set remote exec-file myprog".  Then you can just
> type "run" to launch a new process, just like you were
> debugging natively.
>
> If you instead start gdbserver like so:
>
>  $ gdbserver :9999 myprog
>
> gdbserver will start the myprog program for you; This means
> there'll already by a process running when you connect with
> gdb.
>
>> But I
>> wanted to use "load" followed by "continue" command.
>
> Don't.
>
>> I am also curious to know what actually happens when we say "load"
>> command. Where does it dump the file contents ?
>
> To the debuggee/`inferior process' memory.  It doesn't make much sense
> to use "load" when debugging a unix-like process.
>
> --
> Pedro Alves
>