From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CB17C43334 for ; Fri, 17 Jun 2022 18:03:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383251AbiFQSC7 (ORCPT ); Fri, 17 Jun 2022 14:02:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1383466AbiFQSCo (ORCPT ); Fri, 17 Jun 2022 14:02:44 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 34549B51; Fri, 17 Jun 2022 11:02:34 -0700 (PDT) Received: from x64host.home (unknown [47.189.24.195]) by linux.microsoft.com (Postfix) with ESMTPSA id 3668020C3491; Fri, 17 Jun 2022 11:02:33 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 3668020C3491 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1655488954; bh=7x/ixErefSqMKfios87LlUDWmbSdZZSR+nkVTJ31BrI=; h=From:To:Subject:Date:In-Reply-To:References:From; b=cXf7jdXdbKtZQy5451TdCrx2/Y8z/Nk6gC/QmM0lY6/gWvETR+dV6Ul+Bt1qM7nhu TcWGpkqSVl8+TybBzvvRj1pNngyNe2tRUWfnfnb20QGn8nvxYVISbeazmWeExd99oS gjJbVm/KABmmrjXx7PqlyOxf5Tj0yOZjPK3HetTA= From: madvenka@linux.microsoft.com To: broonie@kernel.org, mark.rutland@arm.com, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jamorris@linux.microsoft.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v15 4/6] arm64: Introduce stack trace reliability checks in the unwinder Date: Fri, 17 Jun 2022 13:02:17 -0500 Message-Id: <20220617180219.20352-5-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220617180219.20352-1-madvenka@linux.microsoft.com> References: <20220617180219.20352-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.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 in unwind(). 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. Signed-off-by: Madhavan T. Venkataraman Reviewed-by: Mark Brown --- arch/arm64/kernel/stacktrace.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index c749129aba5a..5ef2ce217324 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,6 +44,8 @@ * @final_fp: Pointer to the final frame. * * @failed: Unwind failed. + * + * @reliable: Stack trace is reliable. */ struct unwind_state { unsigned long fp; @@ -57,6 +59,7 @@ struct unwind_state { struct task_struct *task; unsigned long final_fp; bool failed; + bool reliable; }; static void unwind_init_common(struct unwind_state *state, @@ -80,6 +83,7 @@ static void unwind_init_common(struct unwind_state *state, state->prev_fp = 0; state->prev_type = STACK_TYPE_UNKNOWN; state->failed = false; + state->reliable = true; /* Stack trace terminates here. */ state->final_fp = (unsigned long)task_pt_regs(task)->stackframe; @@ -242,11 +246,34 @@ static void notrace unwind_next(struct unwind_state *state) } NOKPROBE_SYMBOL(unwind_next); -static void notrace unwind(struct unwind_state *state, +/* + * Check the stack frame for conditions that make further unwinding unreliable. + */ +static void unwind_check_reliability(struct unwind_state *state) +{ + if (state->fp == state->final_fp) { + /* Final frame; no more unwind, no need to check reliability */ + return; + } + + /* + * 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(state->pc)) + state->reliable = false; +} + +static bool notrace unwind(struct unwind_state *state, stack_trace_consume_fn consume_entry, void *cookie) { - while (unwind_continue(state, consume_entry, cookie)) + unwind_check_reliability(state); + while (unwind_continue(state, consume_entry, cookie)) { unwind_next(state); + unwind_check_reliability(state); + } + return !state->failed && state->reliable; } NOKPROBE_SYMBOL(unwind); -- 2.25.1 From mboxrd@z Thu Jan 1 00:00:00 1970 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 43357C43334 for ; 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Fri, 17 Jun 2022 18:03:14 +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 1o2GIt-008XyK-SG for linux-arm-kernel@lists.infradead.org; Fri, 17 Jun 2022 18:02:46 +0000 Received: from x64host.home (unknown [47.189.24.195]) by linux.microsoft.com (Postfix) with ESMTPSA id 3668020C3491; Fri, 17 Jun 2022 11:02:33 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 3668020C3491 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1655488954; bh=7x/ixErefSqMKfios87LlUDWmbSdZZSR+nkVTJ31BrI=; h=From:To:Subject:Date:In-Reply-To:References:From; b=cXf7jdXdbKtZQy5451TdCrx2/Y8z/Nk6gC/QmM0lY6/gWvETR+dV6Ul+Bt1qM7nhu TcWGpkqSVl8+TybBzvvRj1pNngyNe2tRUWfnfnb20QGn8nvxYVISbeazmWeExd99oS gjJbVm/KABmmrjXx7PqlyOxf5Tj0yOZjPK3HetTA= From: madvenka@linux.microsoft.com To: broonie@kernel.org, mark.rutland@arm.com, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jamorris@linux.microsoft.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v15 4/6] arm64: Introduce stack trace reliability checks in the unwinder Date: Fri, 17 Jun 2022 13:02:17 -0500 Message-Id: <20220617180219.20352-5-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220617180219.20352-1-madvenka@linux.microsoft.com> References: <20220617180219.20352-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220617_110243_991897_AC231F13 X-CRM114-Status: GOOD ( 16.73 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 in unwind(). 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. Signed-off-by: Madhavan T. Venkataraman Reviewed-by: Mark Brown --- arch/arm64/kernel/stacktrace.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index c749129aba5a..5ef2ce217324 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,6 +44,8 @@ * @final_fp: Pointer to the final frame. * * @failed: Unwind failed. + * + * @reliable: Stack trace is reliable. */ struct unwind_state { unsigned long fp; @@ -57,6 +59,7 @@ struct unwind_state { struct task_struct *task; unsigned long final_fp; bool failed; + bool reliable; }; static void unwind_init_common(struct unwind_state *state, @@ -80,6 +83,7 @@ static void unwind_init_common(struct unwind_state *state, state->prev_fp = 0; state->prev_type = STACK_TYPE_UNKNOWN; state->failed = false; + state->reliable = true; /* Stack trace terminates here. */ state->final_fp = (unsigned long)task_pt_regs(task)->stackframe; @@ -242,11 +246,34 @@ static void notrace unwind_next(struct unwind_state *state) } NOKPROBE_SYMBOL(unwind_next); -static void notrace unwind(struct unwind_state *state, +/* + * Check the stack frame for conditions that make further unwinding unreliable. + */ +static void unwind_check_reliability(struct unwind_state *state) +{ + if (state->fp == state->final_fp) { + /* Final frame; no more unwind, no need to check reliability */ + return; + } + + /* + * 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(state->pc)) + state->reliable = false; +} + +static bool notrace unwind(struct unwind_state *state, stack_trace_consume_fn consume_entry, void *cookie) { - while (unwind_continue(state, consume_entry, cookie)) + unwind_check_reliability(state); + while (unwind_continue(state, consume_entry, cookie)) { unwind_next(state); + unwind_check_reliability(state); + } + return !state->failed && state->reliable; } NOKPROBE_SYMBOL(unwind); -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel