From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932198AbWFNGYO (ORCPT ); Wed, 14 Jun 2006 02:24:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751200AbWFNGYO (ORCPT ); Wed, 14 Jun 2006 02:24:14 -0400 Received: from public.id2-vpn.continvity.gns.novell.com ([195.33.99.129]:18693 "EHLO emea1-mh.id2.novell.com") by vger.kernel.org with ESMTP id S932198AbWFNGYN convert rfc822-to-8bit (ORCPT ); Wed, 14 Jun 2006 02:24:13 -0400 Message-Id: <448FC7C0.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 7.0.1 Date: Wed, 14 Jun 2006 08:24:32 +0200 From: "Jan Beulich" To: "Eric Sandeen" Cc: "Andreas Kleen" , , Subject: Re: [discuss] [PATCH 1/2] (resend) x86_64 stack overflow debugging References: <20060613194322.D0CDC10CC671@attica.americas.sgi.com> In-Reply-To: <20060613194322.D0CDC10CC671@attica.americas.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Are you certain you will ever see this trigger? Assembly code switches to the special interrupt handling stack prior to calling do_IRQ(), so I can't see how you would ever find yourself on the process stack in stack_overflow_check(). Jan >>> Eric Sandeen 13.06.06 21:43 >>> Take two, now without spurious whitespace :( Applies to git & 2.6.17-rc6 CONFIG_DEBUG_STACKOVERFLOW existed for x86_64 in 2.4, but seems to have gone AWOL in 2.6. I've pretty much just copied this over from the 2.4 code, with appropriate tweaks for the 2.6 kernel, plus a bugfix. I'd personally rather see it printed out the way other arches do it, i.e. bytes-remaining-until-overflow, rather than having to do the subtraction yourself. Also, only 128 bytes remaining seems awfully late to issue a warning. But I'll start here :) Thanks, -Eric Signed-off-by: Eric Sandeen Index: linux/arch/x86_64/Kconfig.debug =================================================================== --- linux.orig/arch/x86_64/Kconfig.debug 2006-03-19 23:53:29.000000000 -0600 +++ linux/arch/x86_64/Kconfig.debug 2006-06-13 08:54:36.923001750 -0500 @@ -35,6 +35,13 @@ Add a simple leak tracer to the IOMMU code. This is useful when you are debugging a buggy device driver that leaks IOMMU mappings. +config DEBUG_STACKOVERFLOW + bool "Check for stack overflows" + depends on DEBUG_KERNEL + help + This option will cause messages to be printed if free stack space + drops below a certain limit. + #config X86_REMOTE_DEBUG # bool "kgdb debugging stub" Index: linux/arch/x86_64/kernel/irq.c =================================================================== --- linux.orig/arch/x86_64/kernel/irq.c 2006-06-09 16:14:55.991440250 -0500 +++ linux/arch/x86_64/kernel/irq.c 2006-06-13 08:55:22.485849250 -0500 @@ -26,6 +26,30 @@ #endif #endif +#ifdef CONFIG_DEBUG_STACKOVERFLOW +/* + * Probabilistic stack overflow check: + * + * Only check the stack in process context, because everything else + * runs on the big interrupt stacks. Checking reliably is too expensive, + * so we just check from interrupts. + */ +static inline void stack_overflow_check(struct pt_regs *regs) +{ + u64 curbase = (u64) current->thread_info; + static unsigned long warned = -60*HZ; + + if (regs->rsp >= curbase && regs->rsp <= curbase + THREAD_SIZE && + regs->rsp < curbase + sizeof(struct thread_info) + 128 && + time_after(jiffies, warned + 60*HZ)) { + printk("do_IRQ: %s near stack overflow (cur:%Lx,rsp:%lx)\n", + current->comm, curbase, regs->rsp); + show_stack(NULL,NULL); + warned = jiffies; + } +} +#endif + /* * Generic, controller-independent functions: */ @@ -96,7 +120,9 @@ exit_idle(); irq_enter(); - +#ifdef CONFIG_DEBUG_STACKOVERFLOW + stack_overflow_check(regs); +#endif __do_IRQ(irq, regs); irq_exit();