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Subject: Re: gcov: NULL pointer dereference with gcc 9.3.1
To:     Luis Henriques <lhenriques@suse.de>
Cc:     linux-kernel@vger.kernel.org
References: <YLZYwgs5hyzFZMlw@suse.de>
From:   Peter Oberparleiter <oberpar@linux.ibm.com>
Message-ID: <0a013450-75eb-de2c-f90a-3df193800cea@linux.ibm.com>
Date:   Wed, 2 Jun 2021 14:35:31 +0200
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On 01.06.2021 17:56, Luis Henriques wrote:
> Hi!
> 
> Maybe this is a known (gcc?) issue, but I'm seeing a NULL pointer splat if
> I instrument my kernel (or a module, more specifically) using gcc 9.3.1.
> 
> It looks like, during initialization in __gcov_init(), gcov_info struct is
> invalid: the filename seems to be correct but ->function is NULL and
> ->n_functions contains garbage.

Thanks for reporting this issue. The symptoms you're seeing look similar
to those that occur when the struct gcov_info layout emitted by GCC does
not match the one used by the kernel. In particular a change in the
GCOV_COUNTER value can cause this behavior.

I've checked upstream GCC 9.3.1 and it seems to match what is used by
the kernel for that GCC version. Could you provide the exact version of
the compiler you are using? Both 'gcc --version' output and the GCC
package version should help. Also what architecture are you seeing this on?


Regards,
  Peter Oberparleiter

-- 
Peter Oberparleiter
Linux on Z Development - IBM Germany