Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261979AbVEXKaX (ORCPT ); Tue, 24 May 2005 06:30:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261799AbVEXKTU (ORCPT ); Tue, 24 May 2005 06:19:20 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:24802 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S262075AbVEXKRS (ORCPT ); Tue, 24 May 2005 06:17:18 -0400 Date: Tue, 24 May 2005 15:48:40 +0530 From: Prasanna S Panchamukhi To: akpm@osdl.org, ak@muc.de, davem@davemloft.net Cc: linux-kernel@vger.kernel.org, systemtap@sources.redhat.com Subject: Re: [PATCH 3/5] Kprobes: Temporary disarming of reentrant probe for x86_64 Message-ID: <20050524101840.GB27186@in.ibm.com> Reply-To: prasanna@in.ibm.com References: <20050524101532.GA27215@in.ibm.com> <20050524101712.GA27186@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050524101712.GA27186@in.ibm.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4655 Lines: 148 This patch includes x86_64 architecture specific changes to support temporary disarming on reentrancy of probes. Signed-of-by: Prasanna S Panchamukhi --- --- linux-2.6.12-rc4-mm2-prasanna/arch/x86_64/kernel/kprobes.c | 73 ++++++++++--- 1 files changed, 60 insertions(+), 13 deletions(-) diff -puN arch/x86_64/kernel/kprobes.c~kprobes-temporary-disarming-on-reentrancy-x86_64 arch/x86_64/kernel/kprobes.c --- linux-2.6.12-rc4-mm2/arch/x86_64/kernel/kprobes.c~kprobes-temporary-disarming-on-reentrancy-x86_64 2005-05-24 15:29:27.000000000 +0530 +++ linux-2.6.12-rc4-mm2-prasanna/arch/x86_64/kernel/kprobes.c 2005-05-24 15:29:27.000000000 +0530 @@ -43,12 +43,10 @@ static DECLARE_MUTEX(kprobe_mutex); -/* kprobe_status settings */ -#define KPROBE_HIT_ACTIVE 0x00000001 -#define KPROBE_HIT_SS 0x00000002 - static struct kprobe *current_kprobe; static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags; +static struct kprobe *kprobe_prev; +static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev; static struct pt_regs jprobe_saved_regs; static long *jprobe_saved_rsp; static kprobe_opcode_t *get_insn_slot(void); @@ -238,6 +236,31 @@ void arch_remove_kprobe(struct kprobe *p down(&kprobe_mutex); } +static inline void save_previous_kprobe(void) +{ + kprobe_prev = current_kprobe; + kprobe_status_prev = kprobe_status; + kprobe_old_rflags_prev = kprobe_old_rflags; + kprobe_saved_rflags_prev = kprobe_saved_rflags; +} + +static inline void restore_previous_kprobe(void) +{ + current_kprobe = kprobe_prev; + kprobe_status = kprobe_status_prev; + kprobe_old_rflags = kprobe_old_rflags_prev; + kprobe_saved_rflags = kprobe_saved_rflags_prev; +} + +static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs) +{ + current_kprobe = p; + kprobe_saved_rflags = kprobe_old_rflags + = (regs->eflags & (TF_MASK | IF_MASK)); + if (is_IF_modifier(p->ainsn.insn)) + kprobe_saved_rflags &= ~IF_MASK; +} + static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs) { regs->eflags |= TF_MASK; @@ -273,10 +296,30 @@ int kprobe_handler(struct pt_regs *regs) regs->eflags |= kprobe_saved_rflags; unlock_kprobes(); goto no_kprobe; + } else if (kprobe_status == KPROBE_HIT_SSDONE) { + /* TODO: Provide re-entrancy from + * post_kprobes_handler() and avoid exception + * stack corruption while single-stepping on + * the instruction of the new probe. + */ + arch_disarm_kprobe(p); + regs->rip = (unsigned long)p->addr; + ret = 1; + } else { + /* We have reentered the kprobe_handler(), since + * another probe was hit while within the + * handler. We here save the original kprobe + * variables and just single step on instruction + * of the new probe without calling any user + * handlers. + */ + save_previous_kprobe(); + set_current_kprobe(p, regs); + p->nmissed++; + prepare_singlestep(p, regs); + kprobe_status = KPROBE_REENTER; + return 1; } - arch_disarm_kprobe(p); - regs->rip = (unsigned long)p->addr; - ret = 1; } else { p = current_kprobe; if (p->break_handler && p->break_handler(p, regs)) { @@ -306,11 +349,7 @@ int kprobe_handler(struct pt_regs *regs) } kprobe_status = KPROBE_HIT_ACTIVE; - current_kprobe = p; - kprobe_saved_rflags = kprobe_old_rflags - = (regs->eflags & (TF_MASK | IF_MASK)); - if (is_IF_modifier(p->ainsn.insn)) - kprobe_saved_rflags &= ~IF_MASK; + set_current_kprobe(p, regs); if (p->pre_handler && p->pre_handler(p, regs)) /* handler has already set things up, so skip ss setup */ @@ -411,13 +450,21 @@ int post_kprobe_handler(struct pt_regs * if (!kprobe_running()) return 0; - if (current_kprobe->post_handler) + if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) { + kprobe_status = KPROBE_HIT_SSDONE; current_kprobe->post_handler(current_kprobe, regs, 0); + } resume_execution(current_kprobe, regs); regs->eflags |= kprobe_saved_rflags; + /*Restore back the original saved kprobes variables and continue. */ + if (kprobe_status == KPROBE_REENTER) { + restore_previous_kprobe(); + goto out; + } unlock_kprobes(); +out: preempt_enable_no_resched(); /* _ -- Prasanna S Panchamukhi Linux Technology Center India Software Labs, IBM Bangalore Ph: 91-80-25044636 - 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/