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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=9QG25IWAvZkbAzL22nhTW74bT1ay/PnpyS4BHMHWGZk=; b=UQIc0vzZoMyMoXQp7xEGjHyGknkc9fEEAWum5qseDPWezEGk1tIc+yARLybeL75+5A 53VnYarnTpGKZ37sY/6DUrboTHncM1xU2LIZlFcmrzw4upho+cWUATdgsfonqjrwT4lY /kR4kEUu3exSGnOghvFTrB7NYyMhf0/gULgs+lWVIXGZAjmdTKG9jQ0H12OD7ibw4ex8 6TTyLYkKKL+zMbQ0S0L/1I8VkYfAlMCdYuxq39vA7shULEs839O5IUw5IoMFIICcT3m+ JRozLq/eNjZ1HvchQ1e5bTyk6u33dGTMV6uENMz86aTPCpL6GWRU2PQNTU3S14drrf1X 8GZA== X-Gm-Message-State: AGi0Pua8axM4/+Hl9mXPJmiSaLeDyaHVWB0lx7BRSjZoOU+IC/i1ykJW qpP2neZjVhEJql5G3q5aC8kWS+cD6ZKR0ssNZFE= X-Google-Smtp-Source: APiQypKOUCwdutCrbx5jsB7oXvfPBtLmcNStpAuGEoVRC2rwC/xHSN2ipZVV7C3tJFoLyJ5tV7qmBNnr17/luexyr1s= X-Received: by 2002:a17:90a:1b4f:: with SMTP id q73mr169352pjq.188.1586191301528; Mon, 06 Apr 2020 09:41:41 -0700 (PDT) Date: Mon, 6 Apr 2020 09:41:13 -0700 In-Reply-To: <20200406164121.154322-1-samitolvanen@google.com> Message-Id: <20200406164121.154322-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200406164121.154322-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.0.292.g33ef6b2f38-goog Subject: [PATCH v10 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-20200406_094143_456239_9F389405 X-CRM114-Status: GOOD ( 11.51 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:54a listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender 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 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.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