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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 20 Jun 2021 19:17:57 -0700
Message-ID: <CAHk-=wip8KgrNUcU68wsLZqbWV+3NWg9kqqQwygHGAA8-xOwMA@mail.gmail.com>
Subject: Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
To:     Michael Schmitz <schmitzmic@gmail.com>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>, Oleg Nesterov <oleg@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Richard Henderson <rth@twiddle.net>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        alpha <linux-alpha@vger.kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        linux-m68k <linux-m68k@lists.linux-m68k.org>,
        Arnd Bergmann <arnd@kernel.org>,
        Ley Foon Tan <ley.foon.tan@intel.com>,
        Tejun Heo <tj@kernel.org>, Kees Cook <keescook@chromium.org>
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On Sun, Jun 20, 2021 at 7:01 PM Michael Schmitz <schmitzmic@gmail.com> wrote:
>
> instrumenting get_reg on m68k and using a similar patch to yours to warn
> when unsaved registers are accessed on the switch stack, I get a hit
> from getegid and getegid32, just by running a simple ptrace on ls.
>
> Going to wack those two moles now ...

I don't see what's going on. Those system calls don't use the register
state, afaik. What's the call chain, exactly?

           Linus