From patchwork Fri Oct 15 02:58:46 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: 12559791 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61942C433EF for ; Fri, 15 Oct 2021 03:04:45 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 1AB1C60F70 for ; Fri, 15 Oct 2021 03:04:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1AB1C60F70 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=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; 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=SOq1lTR1RS6Yll5tqifujr6OsAjxH2sXN7NdDEDOMNo=; b=bhyOopXhIq0L78 uA30yRFm6CUv3YrXjHeG3B658V/0SA8vqtZ9+XR4yyW6Hd288RbI6f+GXC6m9QsbbIO2FwMgCvjhA 1EKnxkXdikx1mg6WG57EsAyEJf1/+kIeauTa9tQKZKVfqWQrzsxBWuj+JbzWtqsNnkvnQn15S3d4b swl9u1wIDO/adiDE37Wq2LsVgxKOTpyjLf5Kz6SfGe5KTibnhgdZaGuxKNBDu7xAZUYggyoUCNmcr 3f4EKE+ISqRDLMrC993DYWfFfhdUUISZFa6qphVO8tMGCKCV8mo6jTeQ31DEK5ggp3JLkdxwDJqb3 weAjhgwSP8ep869FL2oQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mbDUy-005E5Z-2q; Fri, 15 Oct 2021 03:03:09 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mbDRC-005CPJ-3D for linux-arm-kernel@lists.infradead.org; Fri, 15 Oct 2021 02:59:15 +0000 Received: from x64host.home (unknown [47.187.212.181]) by linux.microsoft.com (Postfix) with ESMTPSA id 17D0320B9D20; Thu, 14 Oct 2021 19:59:13 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 17D0320B9D20 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1634266753; bh=LkJybEj9FMuSQymj/zVROIuX/DLBwHm7LAFTUmAbltw=; h=From:To:Subject:Date:In-Reply-To:References:From; b=fiU+VTmlZc3oj8fNbn/VLSXOafDgTgM2g3gjFOVMBgLoGMcF5WazypfITO5sleyHT m/y2RZd/AGZJ+ZQg0qAOzNkS30600q8rJfSkHniScrPfTvC36yiOnj82qKU9+XFaiT IEHTjde1HsUcUWHrfK89UrMl3TQXgO95Qouo0EE0= From: madvenka@linux.microsoft.com To: mark.rutland@arm.com, broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [PATCH v10 10/11] arm64: Introduce stack trace reliability checks in the unwinder Date: Thu, 14 Oct 2021 21:58:46 -0500 Message-Id: <20211015025847.17694-11-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211015025847.17694-1-madvenka@linux.microsoft.com> References: <20211015025847.17694-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211014_195914_222492_1740A57A X-CRM114-Status: GOOD ( 21.62 ) 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" There are some kernel features and conditions that make a stack trace unreliable. Callers may require the unwinder to detect these cases. E.g., livepatch. Introduce a new function called unwind_check_reliability() that will detect these cases and set a flag in the stack frame. Call unwind_check_reliability() for every frame, that is, in unwind_start() and unwind_next(). Introduce the first reliability check in unwind_check_reliability() - If a return PC is not a valid kernel text address, consider the stack trace unreliable. It could be some generated code. Other reliability checks will be added in the future. Let unwind() return a boolean to indicate if the stack trace is reliable. Introduce arch_stack_walk_reliable() for ARM64. This works like arch_stack_walk() except that it returns -EINVAL if the stack trace is not reliable. Until all the reliability checks are in place, arch_stack_walk_reliable() may not be used by livepatch. But it may be used by debug and test code. Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/stacktrace.h | 3 ++ arch/arm64/kernel/stacktrace.c | 48 ++++++++++++++++++++++++++++- 2 files changed, 50 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index ba2180c7d5cd..ce0710fa3037 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -51,6 +51,8 @@ struct stack_info { * replacement lr value in the ftrace graph stack. * * @failed: Unwind failed. + * + * @reliable: Stack trace is reliable. */ struct stackframe { unsigned long fp; @@ -62,6 +64,7 @@ struct stackframe { int graph; #endif bool failed; + bool reliable; }; extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 8e9e6f38c975..142f08ae515f 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,22 @@ #include #include +/* + * Check the stack frame for conditions that make further unwinding unreliable. + */ +static void notrace unwind_check_reliability(struct stackframe *frame) +{ + /* + * If the PC is not a known kernel text address, then we cannot + * be sure that a subsequent unwind will be reliable, as we + * don't know that the code follows our unwind requirements. + */ + if (!__kernel_text_address(frame->pc)) + frame->reliable = false; +} + +NOKPROBE_SYMBOL(unwind_check_reliability); + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -55,6 +71,8 @@ static void notrace unwind_start(struct stackframe *frame, unsigned long fp, frame->prev_fp = 0; frame->prev_type = STACK_TYPE_UNKNOWN; frame->failed = false; + frame->reliable = true; + unwind_check_reliability(frame); } NOKPROBE_SYMBOL(unwind_start); @@ -138,6 +156,7 @@ static void notrace unwind_next(struct task_struct *tsk, #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ frame->pc = ptrauth_strip_insn_pac(frame->pc); + unwind_check_reliability(frame); } NOKPROBE_SYMBOL(unwind_next); @@ -167,7 +186,7 @@ static bool notrace unwind_continue(struct task_struct *task, NOKPROBE_SYMBOL(unwind_continue); -static void notrace unwind(struct task_struct *tsk, +static bool notrace unwind(struct task_struct *tsk, unsigned long fp, unsigned long pc, bool (*fn)(void *, unsigned long), void *data) @@ -177,6 +196,7 @@ static void notrace unwind(struct task_struct *tsk, unwind_start(&frame, fp, pc); while (unwind_continue(tsk, &frame, fn, data)) unwind_next(tsk, &frame); + return frame.reliable; } NOKPROBE_SYMBOL(unwind); @@ -238,4 +258,30 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, } +/* + * arch_stack_walk_reliable() may not be used for livepatch until all of + * the reliability checks are in place in unwind_consume(). However, + * debug and test code can choose to use it even if all the checks are not + * in place. + */ +noinline int notrace arch_stack_walk_reliable(stack_trace_consume_fn consume_fn, + void *cookie, + struct task_struct *task) +{ + unsigned long fp, pc; + + if (task == current) { + /* Skip arch_stack_walk_reliable() in the stack trace. */ + fp = (unsigned long)__builtin_frame_address(1); + pc = (unsigned long)__builtin_return_address(0); + } else { + /* Caller guarantees that the task is not running. */ + fp = thread_saved_fp(task); + pc = thread_saved_pc(task); + } + if (unwind(task, fp, pc, consume_fn, cookie)) + return 0; + return -EINVAL; +} + #endif