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Date:   Sat, 24 Nov 2018 20:17:26 -1000
From:   Joey Pabalinas <joeypabalinas@gmail.com>
To:     "Dmitry V. Levin" <ldv@altlinux.org>
Cc:     Joey Pabalinas <joeypabalinas@gmail.com>,
        Elvira Khabirova <lineprinter@altlinux.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Eugene Syromyatnikov <esyr@redhat.com>,
        linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
        strace-devel@lists.strace.io
Subject: Re: Re: [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in
 ptrace_message
Message-ID: <20181125061726.jtalb5t4tgigzzue@gmail.com>
Mail-Followup-To: Joey Pabalinas <joeypabalinas@gmail.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Elvira Khabirova <lineprinter@altlinux.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>,
        Eugene Syromyatnikov <esyr@redhat.com>, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org, strace-devel@lists.strace.io
References: <20181125022150.46258a20@akathisia>
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 <20181125021059.GA1190@altlinux.org>
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On Sun, Nov 25, 2018 at 05:10:59AM +0300, Dmitry V. Levin wrote:
> Given that without this patch the value returned by PTRACE_GETEVENTMSG
> during syscall stop is undefined, we need two different ptrace_message
> values that cannot be set by other ptrace events to enable reliable
> identification of syscall-enter-stop and syscall-exit-stop in userspace:
> if we make PTRACE_GETEVENTMSG return 0 or any other value routinely set by
> other ptrace events, it would be hard for userspace to find out whether
> the kernel implements new semantics or not.

Ah, I see, I agree that definitely makes sense.

--=20
Cheers,
Joey Pabalinas

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