From patchwork Mon Apr 6 16:41:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11475833 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0EA09912 for ; Mon, 6 Apr 2020 16:42:21 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 6C19024974 for ; Mon, 6 Apr 2020 16:42:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Et7gqyUD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C19024974 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18434-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 24280 invoked by uid 550); 6 Apr 2020 16:41:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 24186 invoked from network); 6 Apr 2020 16:41:53 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=9QG25IWAvZkbAzL22nhTW74bT1ay/PnpyS4BHMHWGZk=; b=Et7gqyUD+/vBdaTxuXGtUp/T61DuoxfIWoFaBtN3Pan+9c6mJeAvmtTBqFUxV+t/h4 LN0HQT9+KjSaqn7Mixerv+7k7S7BD4mkDsLs/o8wZMIjVa09HJA7KFSGB/TtuXU7FvlL 6uPHdyBl7z3cK9g1xF6YKJ4HL90gk6SiklDTGe+TeqWBho/vNNZIxuxtDhoiNjjP56EE VSD6bCJZy8gm1psKtCCT8FCp/6jDu2WpsQ5TdwxuxinTh/gByzaJiThF8xLLt1HhDfgN opEo0Vvbom6U7ovVNJ2IYajd7Ohq17yrtIacfoTmqzq2KcnP242dGSb7nqvNQr4W2sOL fQPQ== X-Google-DKIM-Signature: v=1; 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=MVn4+36ZaoOOY4VAueOcJ6ZHTjy0RpQrqATWdw/Z6fpgMCYTRVMSwbOLoWd7Pe/A1t IH1UJhD+q/JMVzU5fw3gejCV5HqfJAbiEHlqgGvVO712FOO2v+oc/TQYvKj1511IIrye EQXlTLc2eGYtYJwrKMF7l9BqbDRLj9SZ1jNdfbWUPXYtW6W9aiffvJJrkhEDqUlsFUHg HPoSsFFoDDfS1aGTXGYQWIgi5q7SP/U2DKzMc6FA7OEBzA6ShwMh3AOEJqm9SQPmFcVP mDGZCBGDhD+B+12s+o1c5Kb9uq88v2oEtOqABeeJdoARL+XMUYKAmQHzBftl0irndOM+ oMtw== X-Gm-Message-State: AGi0Pub5atvLngpeIql8PcW3lmiJDqPbCGBVKFdD4DOTPit3VwaW/vrv y36NtNSZYN0Hq2yzYbqBdZ4ecy4ZD8Q0toQEyh4= 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 Cc: Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sami Tolvanen 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