Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932512AbWIVOIn (ORCPT ); Fri, 22 Sep 2006 10:08:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932513AbWIVOIn (ORCPT ); Fri, 22 Sep 2006 10:08:43 -0400 Received: from tomts40.bellnexxia.net ([209.226.175.97]:3065 "EHLO tomts40-srv.bellnexxia.net") by vger.kernel.org with ESMTP id S932512AbWIVOIm (ORCPT ); Fri, 22 Sep 2006 10:08:42 -0400 Date: Fri, 22 Sep 2006 10:03:29 -0400 From: Mathieu Desnoyers To: Ingo Molnar Cc: Martin Bligh , "Frank Ch. Eigler" , Masami Hiramatsu , prasanna@in.ibm.com, Andrew Morton , Paul Mundt , linux-kernel , Jes Sorensen , Tom Zanussi , Richard J Moore , Michel Dagenais , Christoph Hellwig , Greg Kroah-Hartman , Thomas Gleixner , William Cohen , ltt-dev@shafik.org, systemtap@sources.redhat.com, Alan Cox Subject: Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management) Message-ID: <20060922140329.GA20839@Krystal> References: <20060921160009.GA30115@Krystal> <20060921160656.GA24774@elte.hu> <20060921214248.GA10097@Krystal> <20060922064955.GA4167@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20060922064955.GA4167@elte.hu> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.4.32-grsec (i686) X-Uptime: 10:00:53 up 30 days, 11:09, 4 users, load average: 0.26, 0.87, 1.07 User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2013 Lines: 64 * Ingo Molnar (mingo@elte.hu) wrote: > > * Mathieu Desnoyers wrote: > > > > "As an example, LTTng traces the page fault handler, when kprobes > > > just can't instrument it." > > > > > > but tracing a raw pagefault at the arch level is a bad idea anyway, > > > we want to trace __handle_mm_fault(). That way you can avoid having > > > to modify every architecture's pagefault handler ... > > > > Then you lose the ability to trace in-kernel minor page faults. > > that's wrong, minor pagefaults go through __handle_mm_fault() just as > much. > Hi Ingo, On a 2.6.17 kernel tree : In do_page_fault() if (unlikely(address >= TASK_SIZE)) { if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0) return; In vmalloc_fault() static inline int vmalloc_fault(unsigned long address) { unsigned long pgd_paddr; pmd_t *pmd_k; pte_t *pte_k; /* * Synchronize this task's top level page-table * with the 'reference' page table. * * Do _not_ use "current" here. We might be inside * an interrupt in the middle of a task switch.. */ pgd_paddr = read_cr3(); pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); if (!pmd_k) return -1; pte_k = pte_offset_kernel(pmd_k, address); if (!pte_present(*pte_k)) return -1; return 0; } It seems like a shortcut path that will never call __handle_mm_fault. This path is precisely used to handle vmalloc faults. Mathieu OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/