Debugging , Tracing...

Debugging , Tracing...

[Auge Mike]

Hi all,

      I have asked before few weeks about tracing the execution of the 
kernel or debugging it. Unfortunately, I faced some problems in using Kgdb, 
especially that the patch was not successful on my redhat 7.3.
     Whatever, lets say that kgdb worked successfully, how can I trace the 
execution of “a specific system call” (lets say printf), so I can see how it 
works internally. Is there any other utility for that? How can I do that 
with kgdb?

     Thanx for your help in advance.

Yours,

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Re: Debugging , Tracing...

[Richard B. Johnson]

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On Sun, 6 Jul 2003, Auge Mike wrote:

> Hi all,
>
>       I have asked before few weeks about tracing the execution of the
> kernel or debugging it. Unfortunately, I faced some problems in using Kgdb,
> especially that the patch was not successful on my redhat 7.3.
>      Whatever, lets say that kgdb worked successfully, how can I trace the
> execution of “a specific system call” (lets say printf), so I can see how it
> works internally. Is there any other utility for that? How can I do that
> with kgdb?
>
>      Thanx for your help in advance.
>
> Yours,

printf() is not a system call. It is some procedure within the
'C' runtime library. Eventually, that library makes a call to
write() which is a kernel system call. You can use strace to see
the execution of all the system calls.

If you want to single-step through the 'C' runtime library, you
need to get their sources and compile them with the '-g' parameter
(for debugging). I don't know why you would want to do that, because
you would then have the sources so you can actually read the source
of what happens with a particular call.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

Re: Debugging , Tracing...

[Slack Ware]

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From: "Auge Mike" 
To: linux-kernel@vger.kernel.org
Subject: Debugging , Tracing...
On Sun, 06 Jul 2003 23:48:17 +0400, Auge Mike wrote:

>Hi all,

>      I have asked before few weeks about tracing the
>execution of the 
>kernel or debugging it. Unfortunately, I faced some
>problems in using Kgdb, 
>especially that the patch was not successful on my
>redhat 7.3.
Hi, Auge. I think that the kernel execution cannot be
debugged nor traced by gdb (kgdb is just a frontend
for the GNU DeBugger), it can be used to trace/debug
the execution of any other program, including modules.
>     Whatever, lets say that kgdb worked
>successfully, how can I trace the 
>execution of “a specific system call” (lets say
>printf), so I can see how it 
>works internally. Is there any other utility for
>that? How can I do that 
>with kgdb?
Other thing, printf() is not a system call, you use
write() (syscall #4) for printing things in screen.
A recommendation: don't use gdb or kgdb for tracing
programs execution, use "strace [program] [arguments]"
in your console, instead. GDB is useful for debugging
things, like when a program received a SIGSEGV (it
generates a coredump) in a file "core", and you can
debug it for searching the error that caused that
signal.
Strace is a tool that you use for tracing programs
syscalls during it execution.
I hope this will be useful for you.
Regards,
                                           Slack

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