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Re: [Ltib] turning off -O2

From: Kallol Biswas
Subject: Re: [Ltib] turning off -O2
Date: Fri, 10 Dec 2010 10:42:18 -0800

I use vmlinux with powerpc-gnu-gdb.

However can not single step linux kernel code from gdb prompt properly or set breakpoint. Breakpoint works from bdi prompt.

Looks like optimization issue.

On Fri, Dec 10, 2010 at 10:23 AM, Stuart Hughes <address@hidden> wrote:
Hi Kallol,

If you have the kernel building (by enabling debug in the kernel config)
then for use with BDI2000 you need vmlinux (the elf image) not the
normal image IIRC.

Failing this, you probably need some help from the kernel experts at

Regards, Stuart

Kallol Biswas wrote:
> There is an issue with removing -O2. Dead codes are not eliminated
> resulting undefined references in linking phase.
> I have compiled manually in linux directory after checking out with ltib
> -m prep -p kernel.
> Even after fixing unresolved symbols the kernel did not boot, while
> inflating uboot complained saying  "Error: Inflate returned -5".
> So to get -g version of kernel working more work in necessary. Do not
> know how people use gdb with BDI2000 for the powerpc
> p4080 platforms.
> On Fri, Dec 10, 2010 at 4:29 AM, Stuart Hughes <address@hidden
> <mailto:address@hidden>> wrote:
>     Hi Kallol,
>     If you don't mind turning it off for all applications and getting a full
>     rebuild, you can run:
>     ./ltib --configure
>     and then under "Enter any CFLAGS for gcc/g++" click enter and then add
>     -O0 or whatever you need.
>     Another option to adjust just the kernel may be to run ./ltib
>     --configure and then select: [*] Configure the kernel
>     This will then build the kernel and drop you to the kernel's config
>     system.  If you enable debugging that will add -g and it may drop the
>     optimisation level down (I don't know though, depends on your
>     source/platform).  There could be other kernel config options that let
>     you do what you want (again kernel dependent).
>     Failing that, Matt's advice is good, edit the appropriate Makefile under
>      arch/powerpc after running ./ltib -p kernel -m prep
>     and then complete the build with ./ltib -p kernel -m scdeploy
>     Regards, Stuart
>     Kallol Biswas wrote:
>     > Hi,
>     >     I would like to turn off -O2 while compiling kernel with ltib.
>     >
>     > The target processor is p4080.
>     >
>     > What is the best way to achieve this?
>     >
>     > Kallol
>     >

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