Messages in this thread | | | Date | Tue, 8 Jun 2021 13:46:22 +0100 | From | Luis Henriques <> | Subject | Re: gcov: NULL pointer dereference with gcc 9.3.1 |
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On Mon, Jun 07, 2021 at 04:32:14PM +0200, Peter Oberparleiter wrote: > On 02.06.2021 16:22, Luis Henriques wrote: > > On Wed, Jun 02, 2021 at 02:35:31PM +0200, Peter Oberparleiter wrote: > >> 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? > > > > Here's the output of 'gcc --version': > > > > gcc (SUSE Linux) 9.3.1 20200903 [revision 9790fa53b48f3a48e0f7a7ad65e2bbf3b206a7b0] > > Copyright (C) 2019 Free Software Foundation, Inc. > > This is free software; see the source for copying conditions. There is NO > > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. > > > > This is the version shipped with openSUSE Tumbleweed, and I'm using it to > > compile an x86_64 kernel. Regarding the 'package version', I'm assuming > > the packages as per the distro package version, right? Here's the data > > from 'zypper info': > > > > Information for package gcc9: > > ----------------------------- > > Repository : Main Repository (OSS) > > Name : gcc9 > > Version : 9.3.1+git1684-3.5 > > Arch : x86_64 > > Vendor : openSUSE > > Installed Size : 94.6 MiB > > Installed : Yes (automatically) > > Status : up-to-date > > Source package : gcc9-9.3.1+git1684-3.5.src > > I've checked the source you referenced and found that it contains a > backport of a change to gcov_info that was only introduced with GCC 10 > to upstream source: the value of GCOV_COUNTERS was reduced from 9 to 8. > > Since I don't think it's feasible to implement support for such > vendor-specific changes in the upstream kernel source my suggestion for > you would be to either > > a) fall back to a vanilla GCC version, > b) fall back to a known-to-work vendor-specific GCC version (GCC 10 > should be fine), or > c) to manually change the GCOV_COUNTERS value in > linux/kernel/gcov/gcc_4_7.c to 8.
Thanks a lot for looking Peter, I've already reported this issue to the maintainers. Hopefully it'll soon be looked at. Anyway, to be honest I just hit this issue accidentally -- I don't really have a requirement on using this version specifically.
Cheers, -- Luís
> > Do you have a link with binaries I could test for upstream 9.3.1? I > > checked [1] but there's only 9.3.0. > > I'm not sure there is any. My analysis was based on source code for > 9.3.0 alone. > > > Regards, > Peter Oberparleiter > > -- > Peter Oberparleiter > Linux on Z Development - IBM Germany
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