Messages in this thread | | | Subject | Re: [RFC PATCH] gcov: add basic gcov_info validation to gcov initialization | From | Peter Oberparleiter <> | Date | Mon, 7 Jun 2021 11:59:45 +0200 |
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On 02.06.2021 12:24, Luis Henriques wrote: > Add a basic gcov_info struct validation helper to gcc to ensure we have > sane from the compiler. > > Signed-off-by: Luis Henriques <lhenriques@suse.de> > --- > Hi! > > I know this won't really validate the gcov_info struct, but it will at > least prevent kernel crashes in simple scenarios (such as the one I'm > seeing with gcc 9.3.1).
Thanks for your suggestion of adding validity checking for the gcov_info struct. The goal you aim at is definitely something that we want to have to reduce the impact of fallout from changes to GCC's gcov_info struct.
In my opinion though the approach you described - looking at the contents of specific fields in gcov_info - isn't the correct way to go forward. Since you cannot know how gcov_info changed, accessing any data in it is very dangerous. Even if there's no out-of-bounds access (if the struct's size was reduced) the field you are checking could have moved elsewhere so the meaningfulness of the check is very limited.
In a previous discussion on the same topic I proposed a different approach for a build-time check that would fully check the compatibility of kernel code and GCC-emitted gcov-related data structures. See:
https://lore.kernel.org/patchwork/patch/1393585/#1592411
Unfortunately I have not yet found the time to implement this approach but it's still on my to-do-list.
Regarding the cause of the error you're seeing I'll have a look at the corresponding GCC source to see if there's anything that could be causing the issue.
Regards, Peter Oberparleiter
-- Peter Oberparleiter Linux on Z Development - IBM Germany
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