linux-kernel - Re: [PATCH v2 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall

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Date:   Tue, 30 Apr 2019 09:46:54 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     X86 ML <x86@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Oleg Nesterov <oleg@...hat.com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Richard Weinberger <richard@....at>,
        Jeff Dike <jdike@...toit.com>,
        Steve Capper <Steve.Capper@....com>,
        Haibo Xu <haibo.xu@....com>, Bin Lu <bin.lu@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2 3/6] x86: clean up _TIF_SYSCALL_EMU handling using
 ptrace_syscall_enter hook

On Mon, Mar 18, 2019 at 3:49 AM Sudeep Holla <sudeep.holla@....com> wrote:
>
> Now that we have a new hook ptrace_syscall_enter that can be called from
> syscall entry code and it handles PTRACE_SYSEMU in generic code, we
> can do some cleanup using the same in syscall_trace_enter.
>
> Further the extra logic to find single stepping PTRACE_SYSEMU_SINGLESTEP
> in syscall_slow_exit_work seems unnecessary. Let's remove the same.
>

Unless the patch set contains a selftest that exercises all the
interesting cases here, NAK.  To be clear, there needs to be a test
that passes on an unmodified kernel and still passes on a patched
kernel.  And that test case needs to *fail* if, for example, you force
"emulated" to either true or false rather than reading out the actual
value.

--Andy