From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8359 invoked by alias); 7 Mar 2006 13:37:04 -0000 Received: (qmail 8349 invoked by uid 22791); 7 Mar 2006 13:37:03 -0000 X-Spam-Status: No, hits=-0.8 required=5.0 tests=AWL,BAYES_00,DNS_FROM_RFC_ABUSE,SPF_SOFTFAIL X-Spam-Check-By: sourceware.org Received: from e36.co.us.ibm.com (HELO e36.co.us.ibm.com) (32.97.110.154) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 07 Mar 2006 13:37:01 +0000 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e36.co.us.ibm.com (8.12.11/8.12.11) with ESMTP id k27Dax0v001224 for ; Tue, 7 Mar 2006 08:36:59 -0500 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.12.10/NCO/VER6.8) with ESMTP id k27DdmLf186806 for ; Tue, 7 Mar 2006 06:39:48 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11/8.13.3) with ESMTP id k27Daxai016076 for ; Tue, 7 Mar 2006 06:36:59 -0700 Received: from newton.in.ibm.com ([9.124.35.47]) by d03av02.boulder.ibm.com (8.12.11/8.12.11) with ESMTP id k27DawQN015990 for ; Tue, 7 Mar 2006 06:36:59 -0700 Received: by newton.in.ibm.com (Postfix, from userid 500) id 4C049CE3; Tue, 7 Mar 2006 19:08:32 +0530 (IST) Date: Tue, 07 Mar 2006 13:37:00 -0000 From: Prasanna S Panchamukhi To: systemtap@sources.redhat.com Subject: [1/5 PATCH] Kprobes fix for broken fault handling for i386 Message-ID: <20060307133832.GA2245@in.ibm.com> Reply-To: prasanna@in.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2006-q1/txt/msg00723.txt.bz2 Hi, Below is the set of patches to fix broken fault handling for i386, x86_64, ppc64, ia64 and sparc64 architectures against 2.6.16-rc5-mm2. These patches are tested for i386 and x86_64 architectures. Could you please test it for ia64 and ppc64. Thanks Prasanna This patch provides proper kprobes fault handling, if a user-specified pre/post handlers tries to access user address space, through copy_from_user(), get_user() etc. The user-specified fault handler gets called only if the fault occurs while executing user-specified handlers. In such a case user-specified handler is allowed to fix it first, later if the user-specifed fault handler does not fix it, we try to fix it by calling fix_exception(). The user-specified handler will not be called if the fault happens when single stepping the original instruction, instead we reset the current probe and allow the system page fault handler to fix it up. Signed-off-by: Prasanna S Panchamukhi arch/i386/kernel/kprobes.c | 57 +++++++++++++++++++++++++++++++++++++++------ 1 files changed, 50 insertions(+), 7 deletions(-) diff -puN arch/i386/kernel/kprobes.c~kprobes-i386-pagefault-handling arch/i386/kernel/kprobes.c --- linux-2.6.16-rc5-mm2/arch/i386/kernel/kprobes.c~kprobes-i386-pagefault-handling 2006-03-07 11:18:14.000000000 +0530 +++ linux-2.6.16-rc5-mm2-prasanna/arch/i386/kernel/kprobes.c 2006-03-07 11:18:14.000000000 +0530 @@ -35,6 +35,7 @@ #include #include #include +#include void jprobe_return_end(void); @@ -545,15 +546,57 @@ static inline int kprobe_fault_handler(s struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - if (kcb->kprobe_status & KPROBE_HIT_SS) { - resume_execution(cur, regs, kcb); + switch(kcb->kprobe_status) { + case KPROBE_HIT_SS: + case KPROBE_REENTER: + /* + * We are here because the instruction being single + * stepped caused a page fault. We reset the current + * kprobe and the eip points back to the probe address + * and allow the page fault handler to continue as a + * normal page fault. + */ + regs->eip = (unsigned long)cur->addr; regs->eflags |= kcb->kprobe_old_eflags; - - reset_current_kprobe(); + if (kcb->kprobe_status == KPROBE_REENTER) + restore_previous_kprobe(kcb); + else + reset_current_kprobe(); preempt_enable_no_resched(); + break; + case KPROBE_HIT_ACTIVE: + case KPROBE_HIT_SSDONE: + /* + * We increment the nmissed count for accounting, + * we can also use npre/npostfault count for accouting + * these specific fault cases. + */ + kprobes_inc_nmissed_count(cur); + + /* + * We come here because instructions in the pre/post + * handler caused the page_fault, this could happen + * if handler tries to access user space by + * copy_from_user(), get_user() etc. Let the + * user-specified handler try to fix it first. + */ + if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) + return 1; + + /* + * In case the user-specified fault handler returned + * zero, try to fix up. + */ + if (fixup_exception(regs)) + return 1; + + /* + * fixup_exception() could not handle it, + * Let do_page_fault() fix it. + */ + break; + default: + break; } return 0; } _ -- Prasanna S Panchamukhi Linux Technology Center India Software Labs, IBM Bangalore Email: prasanna@in.ibm.com Ph: 91-80-51776329