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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=v+FpjDALSMEE3YToTyyoSh5dhgN0urRtPwHsB1+RBqo=; b=i2DFS3iY2p6ZSUDbKff9iqyM4wgXvffNgWFB63FS5hxt77MRFl45YzsGDYMByHRree JtRfzadqPip6K2b93AXON+STVdImmIhYkOVUhYZPNMzf4d10EBL0iTUpsUbyHgUtG5XO WVOEgtYZx3GEAtL/WgtoW0KEMrRMmz5sb3ENeDHq3Um4bfBO/OakD2bbAZq/mnsrOGzg KXOYLnTHQw00RSKQI+kMzE3WpY65F9y8FvbvV0/gOriHpXK1o3YHRPE3Gf0kPStgUz3y jaw7Y0TrraiD6DHmemtgIAsyT5Sk7Tk2N4khq66IQvQw6NHyKGxnTae7lvXouwXSWRFQ wahw== X-Gm-Message-State: AGi0PuaUTc7nQ7SMGJZfPF1vjJxBX/0/mbhtgwXfXnGOtBHGB/Az6fsP 5ADIMm8Z2znRLtlAHz5tplN2evTxCed0WqlIH+Y= X-Google-Smtp-Source: APiQypJFs2LuRTbNsCDtN/g/2Dzd+U0S8ccpzr5nO2MdW7DPIurrW0+QxGuzgOdLZ6sO3fXFhdLkcQx/1PSGVXyeSjg= X-Received: by 2002:a17:90a:8989:: with SMTP id v9mr6124346pjn.119.1587053579583; Thu, 16 Apr 2020 09:12:59 -0700 (PDT) Date: Thu, 16 Apr 2020 09:12:37 -0700 In-Reply-To: <20200416161245.148813-1-samitolvanen@google.com> Message-Id: <20200416161245.148813-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200416161245.148813-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.1.301.g55bc3eb7cb9-goog Subject: [PATCH v11 04/12] scs: disable when function graph tracing is enabled From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200416_091300_990529_1D98A2D2 X-CRM114-Status: GOOD ( 11.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , Masami Hiramatsu , Sami Tolvanen , clang-built-linux@googlegroups.com, Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 SCS when the graph tracer is enabled. With SCS the return address is taken from the shadow stack and the value in the frame record has no effect. The mcount based graph tracer hooks returns by modifying frame records on the (regular) stack, and thus is not compatible. The patchable-function-entry graph tracer used for DYNAMIC_FTRACE_WITH_REGS modifies the LR before it is saved to the shadow stack, and is compatible. Modifying the mcount based graph tracer to work with SCS would require a mechanism to determine the corresponding slot on the shadow stack (and to pass this through the ftrace infrastructure), and we expect that everyone will eventually move to the patchable-function-entry based graph tracer anyway, so for now let's disable SCS when the mcount-based graph tracer is enabled. SCS and patchable-function-entry are both supported from LLVM 10.x. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Reviewed-by: Mark Rutland --- arch/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/Kconfig b/arch/Kconfig index 691a552c2cc3..c53cb9025ad2 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -542,6 +542,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK config SHADOW_CALL_STACK bool "Clang Shadow Call Stack" + depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER depends on ARCH_SUPPORTS_SHADOW_CALL_STACK help This option enables Clang's Shadow Call Stack, which uses a -- 2.26.1.301.g55bc3eb7cb9-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel