Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
To:     Peter Oberparleiter <oberpar@linux.ibm.com>,
        Leon Romanovsky <leon@kernel.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Leon Romanovsky <leonro@nvidia.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
References: <20200904155808.4997-1-leon@kernel.org>
 <6fac3754-f8db-85f5-bdb1-b4c8e7ccc046@linux.ibm.com>
From:   Colin Ian King <colin.king@canonical.com>
Autocrypt: addr=colin.king@canonical.com; prefer-encrypt=mutual; keydata=
 mQINBE6TJCgBEACo6nMNvy06zNKj5tiwDsXXS+LhT+LwtEsy9EnraKYXAf2xwazcICSjX06e
 fanlyhB0figzQO0n/tP7BcfMVNG7n1+DC71mSyRK1ZERcG1523ajvdZOxbBCTvTitYOy3bjs
 +LXKqeVMhK3mRvdTjjmVpWnWqJ1LL+Hn12ysDVVfkbtuIm2NoaSEC8Ae8LSSyCMecd22d9Pn
 LR4UeFgrWEkQsqROq6ZDJT9pBLGe1ZS0pVGhkRyBP9GP65oPev39SmfAx9R92SYJygCy0pPv
 BMWKvEZS/7bpetPNx6l2xu9UvwoeEbpzUvH26PHO3DDAv0ynJugPCoxlGPVf3zcfGQxy3oty
 dNTWkP6Wh3Q85m+AlifgKZudjZLrO6c+fAw/jFu1UMjNuyhgShtFU7NvEzL3RqzFf9O1qM2m
 uj83IeFQ1FZ65QAiCdTa3npz1vHc7N4uEQBUxyXgXfCI+A5yDnjHwzU0Y3RYS52TA3nfa08y
 LGPLTf5wyAREkFYou20vh5vRvPASoXx6auVf1MuxokDShVhxLpryBnlKCobs4voxN54BUO7m
 zuERXN8kadsxGFzItAyfKYzEiJrpUB1yhm78AecDyiPlMjl99xXk0zs9lcKriaByVUv/NsyJ
 FQj/kmdxox3XHi9K29kopFszm1tFiDwCFr/xumbZcMY17Yi2bQARAQABtCVDb2xpbiBLaW5n
 IDxjb2xpbi5raW5nQGNhbm9uaWNhbC5jb20+iQI2BBMBCAAhBQJOkyQoAhsDBQsJCAcDBRUK
 CQgLBRYCAwEAAh4BAheAAAoJEGjCh9/GqAImsBcP9i6C/qLewfi7iVcOwqF9avfGzOPf7CVr
 n8CayQnlWQPchmGKk6W2qgnWI2YLIkADh53TS0VeSQ7Tetj8f1gV75eP0Sr/oT/9ovn38QZ2
 vN8hpZp0GxOUrzkvvPjpH+zdmKSaUsHGp8idfPpZX7XeBO0yojAs669+3BrnBcU5wW45SjSV
 nfmVj1ZZj3/yBunb+hgNH1QRcm8ZPICpjvSsGFClTdB4xu2AR28eMiL/TTg9k8Gt72mOvhf0
 fS0/BUwcP8qp1TdgOFyiYpI8CGyzbfwwuGANPSupGaqtIRVf+/KaOdYUM3dx/wFozZb93Kws
 gXR4z6tyvYCkEg3x0Xl9BoUUyn9Jp5e6FOph2t7TgUvv9dgQOsZ+V9jFJplMhN1HPhuSnkvP
 5/PrX8hNOIYuT/o1AC7K5KXQmr6hkkxasjx16PnCPLpbCF5pFwcXc907eQ4+b/42k+7E3fDA
 Erm9blEPINtt2yG2UeqEkL+qoebjFJxY9d4r8PFbEUWMT+t3+dmhr/62NfZxrB0nTHxDVIia
 u8xM+23iDRsymnI1w0R78yaa0Eea3+f79QsoRW27Kvu191cU7QdW1eZm05wO8QUvdFagVVdW
 Zg2DE63Fiin1AkGpaeZG9Dw8HL3pJAJiDe0KOpuq9lndHoGHs3MSa3iyQqpQKzxM6sBXWGfk
 EkK5Ag0ETpMkKAEQAMX6HP5zSoXRHnwPCIzwz8+inMW7mJ60GmXSNTOCVoqExkopbuUCvinN
 4Tg+AnhnBB3R1KTHreFGoz3rcV7fmJeut6CWnBnGBtsaW5Emmh6gZbO5SlcTpl7QDacgIUuT
 v1pgewVHCcrKiX0zQDJkcK8FeLUcB2PXuJd6sJg39kgsPlI7R0OJCXnvT/VGnd3XPSXXoO4K
 cr5fcjsZPxn0HdYCvooJGI/Qau+imPHCSPhnX3WY/9q5/WqlY9cQA8tUC+7mgzt2VMjFft1h
 rp/CVybW6htm+a1d4MS4cndORsWBEetnC6HnQYwuC4bVCOEg9eXMTv88FCzOHnMbE+PxxHzW
 3Gzor/QYZGcis+EIiU6hNTwv4F6fFkXfW6611JwfDUQCAHoCxF3B13xr0BH5d2EcbNB6XyQb
 IGngwDvnTyKHQv34wE+4KtKxxyPBX36Z+xOzOttmiwiFWkFp4c2tQymHAV70dsZTBB5Lq06v
 6nJs601Qd6InlpTc2mjd5mRZUZ48/Y7i+vyuNVDXFkwhYDXzFRotO9VJqtXv8iqMtvS4xPPo
 2DtJx6qOyDE7gnfmk84IbyDLzlOZ3k0p7jorXEaw0bbPN9dDpw2Sh9TJAUZVssK119DJZXv5
 2BSc6c+GtMqkV8nmWdakunN7Qt/JbTcKlbH3HjIyXBy8gXDaEto5ABEBAAGJAh8EGAEIAAkF
 Ak6TJCgCGwwACgkQaMKH38aoAiZ4lg/+N2mkx5vsBmcsZVd3ys3sIsG18w6RcJZo5SGMxEBj
 t1UgyIXWI9lzpKCKIxKx0bskmEyMy4tPEDSRfZno/T7p1mU7hsM4owi/ic0aGBKP025Iok9G
 LKJcooP/A2c9dUV0FmygecRcbIAUaeJ27gotQkiJKbi0cl2gyTRlolKbC3R23K24LUhYfx4h
 pWj8CHoXEJrOdHO8Y0XH7059xzv5oxnXl2SD1dqA66INnX+vpW4TD2i+eQNPgfkECzKzGj+r
 KRfhdDZFBJj8/e131Y0t5cu+3Vok1FzBwgQqBnkA7dhBsQm3V0R8JTtMAqJGmyOcL+JCJAca
 3Yi81yLyhmYzcRASLvJmoPTsDp2kZOdGr05Dt8aGPRJL33Jm+igfd8EgcDYtG6+F8MCBOult
 TTAu+QAijRPZv1KhEJXwUSke9HZvzo1tNTlY3h6plBsBufELu0mnqQvHZmfa5Ay99dF+dL1H
 WNp62+mTeHsX6v9EACH4S+Cw9Q1qJElFEu9/1vFNBmGY2vDv14gU2xEiS2eIvKiYl/b5Y85Q
 QLOHWV8up73KK5Qq/6bm4BqVd1rKGI9un8kezUQNGBKre2KKs6wquH8oynDP/baoYxEGMXBg
 GF/qjOC6OY+U7kNUW3N/A7J3M2VdOTLu3hVTzJMZdlMmmsg74azvZDV75dUigqXcwjE=
Subject: Re: [PATCH -rc v1] gcov: Disable gcov build with GCC 10
Message-ID: <4ef0af4b-869a-91e1-55b5-c67705625ab7@canonical.com>
Date:   Thu, 10 Sep 2020 20:19:52 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <6fac3754-f8db-85f5-bdb1-b4c8e7ccc046@linux.ibm.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/09/2020 13:52, Peter Oberparleiter wrote:
> On 04.09.2020 17:58, Leon Romanovsky wrote:
>> GCOV built with GCC 10 doesn't initialize n_function variable.
>> This produces different kernel panics as was seen by Colin in
>> Ubuntu [1] and me in FC 32 [2].
>>
>> As a workaround, let's disable GCOV build for broken GCC 10 version.
>>
>> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1891288
>> [2] https://lore.kernel.org/lkml/20200827133932.3338519-1-leon@kernel.org
>> Cc: Colin Ian King <colin.king@canonical.com>
>> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> 
> The following patch should fix the problem with gcov and GCC 10.
> I successfully tested it with kernel 5.9-rc4 on s390 using GCC 10.1.1
> and also with GCC 9.1.1 to see that it didn't break support for previous
> GCC versions. In both cases there were no kernel panics and gcov worked
> fine.
> 
> Could you try this patch to see if it also fixes the problem in your
> environment?
> 

This works perfectly, tested with gcc 10.2 on linux 5.9-rc4 (tip) on an
ARM64 Socionext Synquacer E-Series (Cortex A-53) system.

thanks!

Tested-and-Acked-by: Colin Ian King <colin.king@canonical.com>

> ---8<---
> From: Peter Oberparleiter <oberpar@linux.ibm.com>
> Subject: [PATCH] gcov: add support for GCC 10.1
> 
> Using gcov to collect coverage data for kernels compiled with GCC 10.1
> causes random malfunctions and kernel crashes. This is the result of a
> changed GCOV_COUNTERS value in GCC 10.1 that causes a mismatch between
> the layout of the gcov_info structure created by GCC profiling code and
> the related structure used by the kernel.
> 
> Fix this by updating the in-kernel GCOV_COUNTERS value. Also re-enable
> config GCOV_KERNEL for use with GCC 10.
> 
> Reported-by: Colin Ian King <colin.king@canonical.com>
> Reported-by: Leon Romanovsky <leonro@nvidia.com>
> Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
> ---
>  kernel/gcov/Kconfig   | 1 -
>  kernel/gcov/gcc_4_7.c | 4 +++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
> index bb4b680e8455..3110c77230c7 100644
> --- a/kernel/gcov/Kconfig
> +++ b/kernel/gcov/Kconfig
> @@ -4,7 +4,6 @@ menu "GCOV-based kernel profiling"
>  config GCOV_KERNEL
>  	bool "Enable gcov-based kernel profiling"
>  	depends on DEBUG_FS
> -	depends on !CC_IS_GCC || GCC_VERSION < 100000
>  	select CONSTRUCTORS if !UML
>  	default n
>  	help
> diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
> index 908fdf5098c3..53c67c87f141 100644
> --- a/kernel/gcov/gcc_4_7.c
> +++ b/kernel/gcov/gcc_4_7.c
> @@ -19,7 +19,9 @@
>  #include <linux/vmalloc.h>
>  #include "gcov.h"
> 
> -#if (__GNUC__ >= 7)
> +#if (__GNUC__ >= 10)
> +#define GCOV_COUNTERS			8
> +#elif (__GNUC__ >= 7)
>  #define GCOV_COUNTERS			9
>  #elif (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
>  #define GCOV_COUNTERS			10
>