Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752339AbWCPKwS (ORCPT ); Thu, 16 Mar 2006 05:52:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752346AbWCPKwS (ORCPT ); Thu, 16 Mar 2006 05:52:18 -0500 Received: from e34.co.us.ibm.com ([32.97.110.152]:5779 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S1752325AbWCPKwR (ORCPT ); Thu, 16 Mar 2006 05:52:17 -0500 Date: Thu, 16 Mar 2006 16:22:36 +0530 From: Prasanna S Panchamukhi To: akpm@osdl.org, Andi Kleen , davem@davemloft.net Cc: linux-kernel@vger.kernel.org, ananth@in.ibm.com, anil.s.keshavamurthy@intel.com Subject: [1/5 PATCH] Kprobes-fix-broken-fault-handling-for-i386 Message-ID: <20060316105236.GB16392@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 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3512 Lines: 108 Hi, 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-rc6-mm1/arch/i386/kernel/kprobes.c~kprobes-i386-pagefault-handling 2006-03-16 15:57:57.000000000 +0530 +++ linux-2.6.16-rc6-mm1-prasanna/arch/i386/kernel/kprobes.c 2006-03-16 15:57:57.000000000 +0530 @@ -35,6 +35,7 @@ #include #include #include +#include void jprobe_return_end(void); @@ -544,15 +545,57 @@ 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 - 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/