From patchwork Tue Mar 30 19:09:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 12173593 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84DD8C433C1 for ; Tue, 30 Mar 2021 19:12:51 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EB39761998 for ; Tue, 30 Mar 2021 19:12:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB39761998 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Cc:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9fDy6vgT4jUpCObhWyM3VQML6VUbIcyxfB9CZcpnqPo=; b=mXGYOvVivQWN58cx7hLrBdtTz W7ae5K2uYA7g4jB3TVXfHELOLnAKnOfWdlkGxMIH7VA1zo4y4ibglRM/wowZnmkEKVvirSe1pGCnF H9a0CYwmzy2l06l4XGbmmhHbooWhDu0O8VsjgGtKevKuTnOzcMQmu+gq8FiBbCgw/00+WjttctEWJ w+yIuoMINCJvF3KbHRNvwNMOo/4miga/Ri8W+GHT8d8qrNyAyXWpe2jwP0TFB3lmQzLB69UuVHZ2s AVbWve0JZsW1Su5ABoR2yOCnOUQCM/UTW4FqMxKw0SanDTIl041IRHfhyvaA93v7IpJPJJUT75icM hTlHobJLg==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lRJlX-004gdX-QW; Tue, 30 Mar 2021 19:11:03 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lRJkd-004gZv-Mk for linux-arm-kernel@lists.infradead.org; Tue, 30 Mar 2021 19:10:14 +0000 Received: from x64host.home (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id 532E020B5680; Tue, 30 Mar 2021 12:10:03 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 532E020B5680 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1617131404; bh=Q73XCtD3h8sCsPmxTLvtfVtrZv9vCQxH/D2OWaUjTkY=; h=From:To:Subject:Date:In-Reply-To:References:From; b=TtjXtRuNrG2QkAf3llREdetY6o6aLGy9PBryQS/0Kwq1ufBPRBCdoYsJir8E7syx/ D/eob10Ojeq30xLsQx1UIKpmaQTusOLNnnvNBqWNJZsabPZyXpjFT8hjds3GymPbJu +6aWnXJ42W94iUAkPYMFtzrg/GirCsFjLxYuOdfE= From: madvenka@linux.microsoft.com To: mark.rutland@arm.com, broonie@kernel.org, jpoimboe@redhat.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v1 1/4] arm64: Implement infrastructure for stack trace reliability checks Date: Tue, 30 Mar 2021 14:09:52 -0500 Message-Id: <20210330190955.13707-2-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210330190955.13707-1-madvenka@linux.microsoft.com> References: <77bd5edeea72d44533c769b1e8c0fea7a9d7eb3a> <20210330190955.13707-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210330_201008_276687_9C84BAB5 X-CRM114-Status: GOOD ( 19.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" Implement a check_reliability() function that will contain checks for the presence of various features and conditions that can render the stack trace unreliable. Introduce the first reliability check - If a return PC encountered in a stack trace is not a valid kernel text address, the stack trace is considered unreliable. It could be some generated code. Other reliability checks will be added in the future. These checks will involve checking the return PC to see if it falls inside any special functions where the stack trace is considered unreliable. Implement the infrastructure needed for this. Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/stacktrace.h | 2 + arch/arm64/kernel/stacktrace.c | 80 +++++++++++++++++++++++++++++ 2 files changed, 82 insertions(+) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index eb29b1fe8255..684f65808394 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -59,6 +59,7 @@ struct stackframe { #ifdef CONFIG_FUNCTION_GRAPH_TRACER int graph; #endif + bool reliable; }; extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame); @@ -169,6 +170,7 @@ static inline void start_backtrace(struct stackframe *frame, bitmap_zero(frame->stacks_done, __NR_STACK_TYPES); frame->prev_fp = 0; frame->prev_type = STACK_TYPE_UNKNOWN; + frame->reliable = true; } #endif /* __ASM_STACKTRACE_H */ diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index ad20981dfda4..ff35b3953c39 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,84 @@ #include #include +struct function_range { + unsigned long start; + unsigned long end; +}; + +/* + * Special functions where the stack trace is unreliable. + */ +static struct function_range special_functions[] = { + { 0, 0 } +}; + +static bool is_reliable_function(unsigned long pc) +{ + static bool inited = false; + struct function_range *func; + + if (!inited) { + static char sym[KSYM_NAME_LEN]; + unsigned long size, offset; + + for (func = special_functions; func->start; func++) { + if (kallsyms_lookup(func->start, &size, &offset, + NULL, sym)) { + func->start -= offset; + func->end = func->start + size; + } else { + /* + * This is just a label. So, we only need to + * consider that particular location. So, size + * is the size of one Aarch64 instruction. + */ + func->end = func->start + 4; + } + } + inited = true; + } + + for (func = special_functions; func->start; func++) { + if (pc >= func->start && pc < func->end) + return false; + } + return true; +} + +/* + * Check for the presence of features and conditions that render the stack + * trace unreliable. + * + * Once all such cases have been addressed, this function can aid live + * patching (and this comment can be removed). + */ +static void check_reliability(struct stackframe *frame) +{ + /* + * If the stack trace has already been marked unreliable, just return. + */ + if (!frame->reliable) + return; + + /* + * First, make sure that the return address is a proper kernel text + * address. A NULL or invalid return address probably means there's + * some generated code which __kernel_text_address() doesn't know + * about. Mark the stack trace as not reliable. + */ + if (!__kernel_text_address(frame->pc)) { + frame->reliable = false; + return; + } + + /* + * Check the reliability of the return PC's function. + */ + if (!is_reliable_function(frame->pc)) + frame->reliable = false; +} + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -108,6 +186,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) frame->pc = ptrauth_strip_insn_pac(frame->pc); + check_reliability(frame); + return 0; } NOKPROBE_SYMBOL(unwind_frame);