Re: kmalloc - Crashing

On Wed, Aug 18, 2021 at 06:07:26PM +0530, Lloyd wrote:

On Wed, Aug 18, 2021 at 5:38 PM Greg KH [off-list ref] wrote:

quoted

On Wed, Aug 18, 2021 at 05:03:07PM +0530, Lloyd wrote:

quoted

Hi,

I am starting to write linux kernel mode code. I am on Ubuntu 20.04. I

have

quoted

written the following code

The line   DynPage[i]=0; //CRASH  causes a crash. Can you please guide on
the reason for the crash?

Thanks a lot in advance,
  Lloyd

#pragma GCC push_options
#pragma GCC optimize("O0")

Why are you using these options?  Try removing them and see what
happens.

Thanks a lot Greg. Yes, the code works now.

The assignment inside the for loop (DynPage[i]=0) is not used
anywhere below. I thought that, when the compiler optimizes the code, it
can remove that line. I am writing a small benchmarking application. So, I
don't want that line to be removed by the compiler. Is there a better way
to achieve this?

I am also surprised to see that disabling compiler optimization for
a function caused my code to crash!!

Be careful, and do not modify any of the existing compiler options that
the kernel uses, as they are set very specifically so that stuff like
this will not crash.

And writing benchmarks is an art, be careful to determine what you are
trying to test, and to see if what you are writing actually tests that.

good luck!

greg k-h

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