From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753083AbXDCFqT (ORCPT ); Tue, 3 Apr 2007 01:46:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753077AbXDCFqT (ORCPT ); Tue, 3 Apr 2007 01:46:19 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:45523 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753083AbXDCFqR (ORCPT ); Tue, 3 Apr 2007 01:46:17 -0400 Date: Tue, 3 Apr 2007 11:19:43 +0530 From: Ananth N Mavinakayanahalli To: Andrew Morton Cc: lkml , Prasanna S Panchamukhi , Jim Keniston , Anil S Keshavamurthy , Maneesh Soni Subject: Re: [PATCH] Kprobes: Print details of kretprobe on assertion failure Message-ID: <20070403054943.GA18459@in.ibm.com> Reply-To: ananth@in.ibm.com References: <20070402092636.GA27905@in.ibm.com> <20070402141732.166f50bd.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070402141732.166f50bd.akpm@linux-foundation.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 02, 2007 at 02:17:32PM -0700, Andrew Morton wrote: > On Mon, 2 Apr 2007 14:56:36 +0530 > Ananth N Mavinakayanahalli wrote: > > > From: Ananth N Mavinakayanahalli > > > > In certain cases like when the real return address can't be found or > > when the number of tracked calls to a kretprobed function is less than > > the number of returns, we may not be able to find the correct return > > address after processing a kretprobe. Currently we just do a BUG_ON, but > > no information is provided about the actual failing kretprobe. > > > > Print out details of the kretprobe before calling BUG(). > > > > Signed-off-by: Ananth N Mavinakayanahalli > > > > --- > > arch/i386/kernel/kprobes.c | 6 +++++- > > arch/ia64/kernel/kprobes.c | 7 ++++++- > > arch/powerpc/kernel/kprobes.c | 7 ++++++- > > arch/x86_64/kernel/kprobes.c | 7 ++++++- > > 4 files changed, 23 insertions(+), 4 deletions(-) > > > > Index: linux-2.6.21-rc5/arch/i386/kernel/kprobes.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/arch/i386/kernel/kprobes.c > > +++ linux-2.6.21-rc5/arch/i386/kernel/kprobes.c > > @@ -440,7 +440,11 @@ fastcall void *__kprobes trampoline_hand > > break; > > } > > > > - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); > > + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { > > + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", > > + ri->rp, ri->rp->kp.addr); > > + BUG(); > > + } > > > > spin_unlock_irqrestore(&kretprobe_lock, flags); > > > > Index: linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/arch/ia64/kernel/kprobes.c > > +++ linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c > > @@ -444,7 +444,12 @@ int __kprobes trampoline_probe_handler(s > > break; > > } > > > > - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); > > + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { > > + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", > > + ri->rp, ri->rp->kp.addr); > > + BUG(); > > + } > > + > > regs->cr_iip = orig_ret_address; > > > > reset_current_kprobe(); > > Index: linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/arch/powerpc/kernel/kprobes.c > > +++ linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c > > @@ -293,7 +293,12 @@ int __kprobes trampoline_probe_handler(s > > break; > > } > > > > - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); > > + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { > > + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", > > + ri->rp, ri->rp->kp.addr); > > + BUG(); > > + } > > + > > regs->nip = orig_ret_address; > > > > reset_current_kprobe(); > > Index: linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/arch/x86_64/kernel/kprobes.c > > +++ linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c > > @@ -438,7 +438,12 @@ int __kprobes trampoline_probe_handler(s > > break; > > } > > > > - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); > > + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { > > + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", > > + ri->rp, ri->rp->kp.addr); > > + BUG(); > > + } > > + > > regs->rip = orig_ret_address; > > > > A lot of copying-and-pasting there. Would it be better if this assertion > was performed in a library function in kernel/kprobes.c? Indeed. Here is the updated patch... From: Ananth N Mavinakayanahalli In certain cases like when the real return address can't be found or when the number of tracked calls to a kretprobed function is less than the number of returns, we may not be able to find the correct return address after processing a kretprobe. Currently we just do a BUG_ON, but no information is provided about the actual failing kretprobe. Print out details of the kretprobe before calling BUG(). Signed-off-by: Ananth N Mavinakayanahalli --- arch/i386/kernel/kprobes.c | 3 +-- arch/ia64/kernel/kprobes.c | 3 ++- arch/powerpc/kernel/kprobes.c | 2 +- arch/x86_64/kernel/kprobes.c | 2 +- include/linux/kprobes.h | 10 ++++++++++ 5 files changed, 15 insertions(+), 5 deletions(-) Index: linux-2.6.21-rc5/arch/i386/kernel/kprobes.c =================================================================== --- linux-2.6.21-rc5.orig/arch/i386/kernel/kprobes.c +++ linux-2.6.21-rc5/arch/i386/kernel/kprobes.c @@ -440,8 +440,7 @@ fastcall void *__kprobes trampoline_hand break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); - + kretprobe_assert(ri, orig_ret_address, trampoline_address); spin_unlock_irqrestore(&kretprobe_lock, flags); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { Index: linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c =================================================================== --- linux-2.6.21-rc5.orig/arch/ia64/kernel/kprobes.c +++ linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c @@ -444,7 +444,8 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); + regs->cr_iip = orig_ret_address; reset_current_kprobe(); Index: linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c =================================================================== --- linux-2.6.21-rc5.orig/arch/powerpc/kernel/kprobes.c +++ linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c @@ -293,7 +293,7 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); regs->nip = orig_ret_address; reset_current_kprobe(); Index: linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c =================================================================== --- linux-2.6.21-rc5.orig/arch/x86_64/kernel/kprobes.c +++ linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c @@ -438,7 +438,7 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); regs->rip = orig_ret_address; reset_current_kprobe(); Index: linux-2.6.21-rc5/include/linux/kprobes.h =================================================================== --- linux-2.6.21-rc5.orig/include/linux/kprobes.h +++ linux-2.6.21-rc5/include/linux/kprobes.h @@ -158,6 +158,16 @@ struct kretprobe_instance { struct task_struct *task; }; +static inline void kretprobe_assert(struct kretprobe_instance *ri, + unsigned long orig_ret_address, unsigned long trampoline_address) +{ + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", + ri->rp, ri->rp->kp.addr); + BUG(); + } +} + extern spinlock_t kretprobe_lock; extern struct mutex kprobe_mutex; extern int arch_prepare_kprobe(struct kprobe *p);