From patchwork Tue Nov 23 19:37:21 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: 12693497 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 9ED59C433F5 for ; Tue, 23 Nov 2021 19:39:24 +0000 (UTC) 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=q/FNc1mf9xIdtrZiJILml8vc9kirYzxAxjO/nNyedYw=; b=KeYK8XOGHKs/Fg m6AdzWFecvNLUP/8+C1dMmh8O/OsCJUQzUl0RXnCQIgZDqb9fIc8p4AZQzghe3fe7eqP7PxF+gwNW La/8S+GazAlXc/8t4rwnjUTDMVstb95qFLd5UR9Q9kPFKsEjbP4OqJekNnK17GCZgZ6Z2HvAG0s66 J9dZQYpoh6EUPhsXqR7zgGrPwxm/X7pEKTdwJ4vI2tO51yqHWueGf2jfs2ut3h28CPdUHsxZhQ6Mt q9kLAfju93+bLhB9DCWkBHc+1fBp3vCUAqg5vfnXrEKaKbyQA+XRzkxNTYT+Wd5BdPgiK56mN8S0T TbGdY5oHhlBiusQmR1Ng==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mpbc9-003KVd-JD; Tue, 23 Nov 2021 19:38:01 +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 1mpbbl-003KPl-5o for linux-arm-kernel@lists.infradead.org; Tue, 23 Nov 2021 19:37:38 +0000 Received: from x64host.home (unknown [47.187.212.181]) by linux.microsoft.com (Postfix) with ESMTPSA id E8CAD20D4D39; Tue, 23 Nov 2021 11:37:35 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com E8CAD20D4D39 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1637696256; bh=4186IGzt9P0jgk6sDPjuuzrx/GJRpOlohBw5fEU6ZnY=; h=From:To:Subject:Date:In-Reply-To:References:From; b=NH1mpd/pqVIHkZwa0kb2q2g1Eu3HnL+HMfUmRnjAxgTMIakYJdyLKv2ou5oesH8Rq 6TJfVLVB+W9m5yYguic9FbIGxz2CUfmlw9VDulannLVk4axoBFi9r6vaegNSLk4oVt DI9JiII0OOI8WkWuv4tglMKWPh7uY5A+7ny5yvdw= 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 v11 3/5] arm64: Make the unwind loop in unwind() similar to other architectures Date: Tue, 23 Nov 2021 13:37:21 -0600 Message-Id: <20211123193723.12112-4-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211123193723.12112-1-madvenka@linux.microsoft.com> References: <8b861784d85a21a9bf08598938c11aff1b1249b9> <20211123193723.12112-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211123_113737_321417_F39F3179 X-CRM114-Status: GOOD ( 20.91 ) 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" Change the loop in unwind() =========================== Change the unwind loop in unwind() to: unwind_start(&frame, fp, pc); while (unwind_continue(tsk, &frame, fn, data)) unwind_next(tsk, &frame); New function unwind_continue() ============================== Define a new function unwind_continue() that is used in the unwind loop to check for conditions that terminate a stack trace. The conditions checked are: - If the bottom of the stack has been reached, terminate. - If the consume_entry() function returns false, the caller of unwind has asked to terminate the stack trace. So, terminate. - If unwind_next() failed for some reason (like stack corruption), terminate. Do not return an error value from unwind_next() =============================================== We want to check for terminating conditions only in unwind_continue() from the unwinder loop. So, do not return an error value from unwind_next(). Simply set a flag in the stackframe and check the flag in unwind_continue(). Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/stacktrace.h | 3 ++ arch/arm64/kernel/stacktrace.c | 75 ++++++++++++++++++----------- 2 files changed, 50 insertions(+), 28 deletions(-) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 3a15d376ab36..d838586adef9 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -51,6 +51,8 @@ struct stack_info { * @kr_cur: When KRETPOLINES is selected, holds the kretprobe instance * associated with the most recently encountered replacement lr * value. + * + * @failed: Unwind failed. */ struct stackframe { unsigned long fp; @@ -61,6 +63,7 @@ struct stackframe { #ifdef CONFIG_KRETPROBES struct llist_node *kr_cur; #endif + bool failed; }; 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 918852cd2681..3b670ab1f0e9 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -54,6 +54,7 @@ static void unwind_start(struct stackframe *frame, unsigned long fp, bitmap_zero(frame->stacks_done, __NR_STACK_TYPES); frame->prev_fp = 0; frame->prev_type = STACK_TYPE_UNKNOWN; + frame->failed = false; } /* @@ -63,24 +64,26 @@ static void unwind_start(struct stackframe *frame, unsigned long fp, * records (e.g. a cycle), determined based on the location and fp value of A * and the location (but not the fp value) of B. */ -static int notrace unwind_next(struct task_struct *tsk, - struct stackframe *frame) +static void notrace unwind_next(struct task_struct *tsk, + struct stackframe *frame) { unsigned long fp = frame->fp; struct stack_info info; - /* Final frame; nothing to unwind */ - if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) - return -ENOENT; - - if (fp & 0x7) - return -EINVAL; + if (fp & 0x7) { + frame->failed = true; + return; + } - if (!on_accessible_stack(tsk, fp, 16, &info)) - return -EINVAL; + if (!on_accessible_stack(tsk, fp, 16, &info)) { + frame->failed = true; + return; + } - if (test_bit(info.type, frame->stacks_done)) - return -EINVAL; + if (test_bit(info.type, frame->stacks_done)) { + frame->failed = true; + return; + } /* * As stacks grow downward, any valid record on the same stack must be @@ -96,8 +99,10 @@ static int notrace unwind_next(struct task_struct *tsk, * stack. */ if (info.type == frame->prev_type) { - if (fp <= frame->prev_fp) - return -EINVAL; + if (fp <= frame->prev_fp) { + frame->failed = true; + return; + } } else { set_bit(frame->prev_type, frame->stacks_done); } @@ -125,8 +130,10 @@ static int notrace unwind_next(struct task_struct *tsk, */ orig_pc = ftrace_graph_ret_addr(tsk, NULL, frame->pc, (void *)frame->fp); - if (WARN_ON_ONCE(frame->pc == orig_pc)) - return -EINVAL; + if (WARN_ON_ONCE(frame->pc == orig_pc)) { + frame->failed = true; + return; + } frame->pc = orig_pc; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ @@ -134,11 +141,31 @@ static int notrace unwind_next(struct task_struct *tsk, if (is_kretprobe_trampoline(frame->pc)) frame->pc = kretprobe_find_ret_addr(tsk, (void *)frame->fp, &frame->kr_cur); #endif - - return 0; } NOKPROBE_SYMBOL(unwind_next); +static bool unwind_continue(struct task_struct *task, + struct stackframe *frame, + stack_trace_consume_fn consume_entry, void *cookie) +{ + if (frame->failed) { + /* PC is suspect. Cannot consume it. */ + return false; + } + + if (!consume_entry(cookie, frame->pc)) { + /* Caller terminated the unwind. */ + frame->failed = true; + return false; + } + + if (frame->fp == (unsigned long)task_pt_regs(task)->stackframe) { + /* Final frame; nothing to unwind */ + return false; + } + return true; +} + static void notrace unwind(struct task_struct *tsk, unsigned long fp, unsigned long pc, bool (*fn)(void *, unsigned long), void *data) @@ -146,16 +173,8 @@ static void notrace unwind(struct task_struct *tsk, struct stackframe frame; unwind_start(&frame, fp, pc); - - while (1) { - int ret; - - if (!fn(data, frame.pc)) - break; - ret = unwind_next(tsk, &frame); - if (ret < 0) - break; - } + while (unwind_continue(tsk, &frame, fn, data)) + unwind_next(tsk, &frame); } NOKPROBE_SYMBOL(unwind);