How to build the kernel without any optimization?

How to build the kernel without any optimization?

[Shawn Jin]

Hi,

I'm tracing the execution of ds1307_probe() and find that some of
variables or function arguments cannot be printed in gdb because they
are optimized out or not in the current context. This really gives
some headache. Is there a way to build the kernel without any
optimization? What gcc option shall I disable or add?

I already added the following to arch/powerpc/Makefile.

# Prevent GDB from jumping around in the code when trying to single step
ifeq ($(CONFIG_DEBUG_KERNEL),y)
KBUILD_CFLAGS           += -fno-schedule-insns -fno-schedule-insns2
endif

Thanks,
-Shawn.

Re: How to build the kernel without any optimization?

[Nicholas Mc Guire]

On Fri, 20 Aug 2010, Shawn Jin wrote:

> Hi,
> 
> I'm tracing the execution of ds1307_probe() and find that some of
> variables or function arguments cannot be printed in gdb because they
> are optimized out or not in the current context. This really gives
> some headache. Is there a way to build the kernel without any
> optimization? What gcc option shall I disable or add?
> 
> I already added the following to arch/powerpc/Makefile.
> 
> # Prevent GDB from jumping around in the code when trying to single step
> ifeq ($(CONFIG_DEBUG_KERNEL),y)
> KBUILD_CFLAGS           += -fno-schedule-insns -fno-schedule-insns2
> endif
>

much of the kernel can not be build without optimization - what you 
can do though is slectively try to disable optimization for specific
files by putting 

 CFLAGS_REMOVE_objfilenam.o = -SOME_OPT

in the Makefile. I think that is safer than what you did above as this would
always depend on the order of options that ultimately get passed to gcc.

hofrat 

Re: How to build the kernel without any optimization?

[Shawn Jin]

>> I already added the following to arch/powerpc/Makefile.
>>
>> # Prevent GDB from jumping around in the code when trying to single step
>> ifeq ($(CONFIG_DEBUG_KERNEL),y)
>> KBUILD_CFLAGS =A0 =A0 =A0 =A0 =A0 +=3D -fno-schedule-insns -fno-schedule=
-insns2
>> endif
>>
>
> much of the kernel can not be build without optimization - what you
> can do though is slectively try to disable optimization for specific
> files by putting
>
> =A0CFLAGS_REMOVE_objfilenam.o =3D -SOME_OPT
>
> in the Makefile. I think that is safer than what you did above as this wo=
uld
> always depend on the order of options that ultimately get passed to gcc.

With this CLAGS_REMOVE, building the objfilenam.o uses only the
-SOME_OPT instead of the default CFLAGS defined? The most I found for
-SOME_OPT is the -pg.

Thanks,
-Shawn.