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Date:   Fri, 3 May 2019 15:54:26 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     Qais Yousef <qais.yousef@arm.com>, linux-kernel@vger.kernel.org,
        Michal Gregorczyk <michalgr@live.com>,
        Adrian Ratiu <adrian.ratiu@collabora.com>,
        Mohammad Husain <russoue@gmail.com>,
        Srinivas Ramana <sramana@codeaurora.org>,
        duyuchao <yuchao.du@unisoc.com>,
        Manjo Raja Rao <linux@manojrajarao.com>,
        Karim Yaghmour <karim.yaghmour@opersys.com>,
        Tamir Carmeli <carmeli.tamir@gmail.com>,
        Yonghong Song <yhs@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Brendan Gregg <brendan.d.gregg@gmail.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Kees Cook <keescook@chromium.org>, kernel-team@android.com,
        Daniel Borkmann <daniel@iogearbox.net>,
        Ingo Molnar <mingo@redhat.com>, netdev@vger.kernel.org
Subject: Re: [PATCH RFC] bpf: Add support for reading user pointers
Message-ID: <20190503135426.GA2606@hirez.programming.kicks-ass.net>
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 <20190503134935.GA253329@google.com>
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On Fri, May 03, 2019 at 09:49:35AM -0400, Joel Fernandes wrote:
> In
> particular, we learnt with extensive discussions that user/kernel pointers
> are not necessarily distinguishable purely based on their address.

This is correct; a number of architectures have a completely separate
user and kernel address space. Much like how the old i386 4G:4G patches
worked.