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Message-ID: <20200116173950.GB21396@willie-the-truck>
Date: Thu, 16 Jan 2020 17:39:51 +0000
From: Will Deacon <will@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Mark Rutland <mark.rutland@....com>,
Dave Martin <Dave.Martin@....com>,
Kees Cook <keescook@...omium.org>,
Laura Abbott <labbott@...hat.com>, Marc Zyngier <maz@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Jann Horn <jannh@...gle.com>,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
clang-built-linux@...glegroups.com,
kernel-hardening@...ts.openwall.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 08/15] arm64: disable function graph tracing with SCS
On Fri, Dec 06, 2019 at 02:13:44PM -0800, Sami Tolvanen wrote:
> The graph tracer hooks returns by modifying frame records on the
> (regular) stack, but with SCS the return address is taken from the
> shadow stack, and the value in the frame record has no effect. As we
> don't currently have a mechanism to determine the corresponding slot
> on the shadow stack (and to pass this through the ftrace
> infrastructure), for now let's disable the graph tracer when SCS is
> enabled.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Mark Rutland <mark.rutland@....com>
> ---
> arch/arm64/Kconfig | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1b4476ddb83..49e5f94ff4af 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -149,7 +149,7 @@ config ARM64
> select HAVE_FTRACE_MCOUNT_RECORD
> select HAVE_FUNCTION_TRACER
> select HAVE_FUNCTION_ERROR_INJECTION
> - select HAVE_FUNCTION_GRAPH_TRACER
> + select HAVE_FUNCTION_GRAPH_TRACER if !SHADOW_CALL_STACK
> select HAVE_GCC_PLUGINS
> select HAVE_HW_BREAKPOINT if PERF_EVENTS
> select HAVE_IRQ_TIME_ACCOUNTING
I think this is the wrong way around, as we support the graph tracer
today and so I think SHADOW_CALL_STACK should depend on !GRAPH_TRACER
and possibly even EXPERT until this is resolved.
Will
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