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 CBB41C4332F for ; Mon, 3 Jan 2022 16:52:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234911AbiACQwz (ORCPT ); Mon, 3 Jan 2022 11:52:55 -0500 Received: from linux.microsoft.com ([13.77.154.182]:53278 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234899AbiACQww (ORCPT ); Mon, 3 Jan 2022 11:52:52 -0500 Received: from x64host.home (unknown [47.187.212.181]) by linux.microsoft.com (Postfix) with ESMTPSA id CD79E20B718A; Mon, 3 Jan 2022 08:52:50 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com CD79E20B718A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1641228771; bh=k0L/6HF0XSKKkYTWUToL3wE6EoMVilDa95cDIedw94E=; h=From:To:Subject:Date:In-Reply-To:References:From; b=pY92LoKgoXa2SoD4BwTeElCgeiSgs8onNLmiX4+ShFKPz7yM2gvTEcAEqQ0l2vUev R+ApgO3xM78oO3lKMxJf3x7As3Cme4PjSaXoz5DMDWmbap0kwZg3hQWfBJvp1X65mK qRB+Vtpt6MuRRyGQKed9jEI9QsDDXsxhZuaDz1B4= 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 v12 07/10] arm64: Introduce stack trace reliability checks in the unwinder Date: Mon, 3 Jan 2022 10:52:09 -0600 Message-Id: <20220103165212.9303-8-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220103165212.9303-1-madvenka@linux.microsoft.com> References: <0d0eb36f348fb5a6af6eb592c0525f6e94007328> <20220103165212.9303-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: live-patching@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 --- arch/arm64/include/asm/stacktrace.h | 3 +++ arch/arm64/kernel/stacktrace.c | 29 +++++++++++++++++++++++++++-- 2 files changed, 30 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 9d1fddc26586..47d4be69799a 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -63,6 +63,8 @@ struct stack_info { * @final_fp Pointer to the final frame. * * @failed: Unwind failed. + * + * @reliable: Stack trace is reliable. */ struct unwind_state { unsigned long fp; @@ -79,6 +81,7 @@ struct unwind_state { void *cookie; unsigned long final_fp; 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 af0949f028c9..54c3396a65c3 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,25 @@ #include #include +/* + * 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; +} + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -64,6 +83,8 @@ static void unwind_init_common(struct unwind_state *state, /* Stack trace terminates here. */ state->final_fp = (unsigned long)task_pt_regs(task)->stackframe; + + state->reliable = true; } /* @@ -202,10 +223,14 @@ static void notrace unwind_next(struct unwind_state *state) } NOKPROBE_SYMBOL(unwind_next); -static void notrace unwind(struct unwind_state *state) +static bool notrace unwind(struct unwind_state *state) { - while (unwind_continue(state)) + unwind_check_reliability(state); + while (unwind_continue(state)) { unwind_next(state); + unwind_check_reliability(state); + } + return !state->failed && state->reliable; } NOKPROBE_SYMBOL(unwind); -- 2.25.1