From: loody <miloody@gmail.com>
To: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: gdb@sourceware.org
Subject: Re: some questions about kernel debugging
Date: Fri, 09 Jul 2010 15:56:00 -0000 [thread overview]
Message-ID: <AANLkTim51qdgX_X0AO3fj3XjC5QKuKORstbmnO8ttoz1@mail.gmail.com> (raw)
In-Reply-To: <20100709130708.GA13468@host0.dyn.jankratochvil.net>
hi:
thanks for your kind reply :)
2010/7/9 Jan Kratochvil <jan.kratochvil@redhat.com>:
> On Fri, 09 Jul 2010 13:52:31 +0200, loody wrote:
>> I enable kernel hacking options about kernel debugging on my mips platform.
>> I can successfully connect to the target board.
>> My question is:
>> 1. why I cannot p/x the value of variable?
>> I have enabled CONFIG_ARCH_WANT_FRAME_POINTERS and CONFIG_FRAME_POINTER
>> but I still get the message which tell me "value optimized out".
>> did I miss anything?
>> my kernel version is 2.6.30.9?
>
> This is not a GDB problem, you should report it to GCC (you need a minimal
> reproducer for the bugreport).
>
> The problem is Linux kernel cannot (at least could not) compile with -O0, it
> requires -O2 to successfully build. -O2 was always mostly unsupported
> together with -g (=debuggingo information). For -O2 -g you should use the
> latest GCC - SVN HEAD best - and definitely at least 4.5 (for VTA
> - var-tracking-assignments).
>
> Besides resolving this -O2 -g problem at GCC the easy way is always to just
> `disassemble' the code in GDB, guess from the code+source in which
> register/memory is the value probably located and access it directly there.
I tried compile the kernel with -O1 -g but it still fail.
does that mean only program compiled with -O0 -g will not get the
error message when trying to see the variable?
appreciate your help,
miloody
next prev parent reply other threads:[~2010-07-09 15:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-09 11:52 loody
2010-07-09 13:07 ` Jan Kratochvil
2010-07-09 15:56 ` loody [this message]
2010-07-09 16:20 ` Jan Kratochvil
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