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Date:   Tue, 5 Nov 2019 09:04:26 +0000
From:   Mark Rutland <mark.rutland@arm.com>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Jann Horn <jannh@google.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 10/17] arm64: disable kretprobes with SCS
Message-ID: <20191105090426.GA4743@lakrids.cambridge.arm.com>
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On Mon, Nov 04, 2019 at 03:42:09PM -0800, Sami Tolvanen wrote:
> On Mon, Nov 4, 2019 at 9:05 AM Mark Rutland <mark.rutland@arm.com> wrote:
> > I'm a bit confused as to why that's the case -- could you please
> > elaborate on how this is incompatible?
> >
> > IIUC kretrobes works by patching the function entry point with a BRK, so
> > that it can modify the LR _before_ it is saved to the stack. I don't see
> > how SCS affects that.
> 
> You're correct. While this may not be optimal for reducing attack
> surface, I just tested this to confirm that there's no functional
> conflict. I'll drop this and related patches from v5.

Great; thanks for confirming!

Mark.