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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=euAiLk7SvDA/PnGZzpLLTI9flOv+YzdznFtW1y3XFgk=; b=RlJYX4ruovIpW+BszJE7e1BFEX95TVImyBohqcQZZQkBW3kviZdSaTuNzu1wmwBrjX pknNX+VA44dQZPdKOFuCe+aEU5UWJC6Z5SMSa4Nfwzoy+2isi1h0hnLX0cPue8FxhKKo vaaAj+v7Dy+pVh/Ojf9tq+gI0/GS+4tZKnxUtXF2tc+rdFHQ5KgJ1O63imG3ctvVVCmp YdJnXnrfwfxrMKhg/wzr2COFoeo6pbpm6pq/LjTJq/Hi1J5dV1qM2LAWXv4KC00MweDH S37AWMSTg5W+knod6yjXfxeOqFxXu97U15mkomrTnUaKX9TrU+/6aIp2//EiPacpm34P N5ug== X-Gm-Message-State: APjAAAWk1Syie64/ThBpRTdG6ueAEcgxC5ZC+OdvpoCtLBTF41pAG8Ha wUI1kDJv+AW5deKW+st2D9k/5HFyhnYiioHDp+c= X-Google-Smtp-Source: APXvYqxlqJxQl5BI1MzivwW+BHpAHu+yoCC0b4OSIv8tWhwsj+eyaqOdONKRweH1H/aDrmbR0wf2esPZBfRljhjv3g8= X-Received: by 2002:ac8:3aa6:: with SMTP id x35mr39983775qte.38.1582652397221; Tue, 25 Feb 2020 09:39:57 -0800 (PST) Date: Tue, 25 Feb 2020 09:39:25 -0800 In-Reply-To: <20200225173933.74818-1-samitolvanen@google.com> Message-Id: <20200225173933.74818-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200225173933.74818-1-samitolvanen@google.com> X-Mailer: git-send-email 2.25.0.265.gbab2e86ba0-goog Subject: [PATCH v9 04/12] scs: disable when function graph tracing is enabled From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200225_093959_849472_59572A55 X-CRM114-Status: GOOD ( 12.16 ) 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 , Masahiro Yamada , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , clang-built-linux@googlegroups.com, Sami Tolvanen , 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 a67fa78c92e7..d53ade0950a5 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -535,6 +535,7 @@ 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 -- 2.25.0.265.gbab2e86ba0-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel