Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751437AbWEIHKw (ORCPT ); Tue, 9 May 2006 03:10:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751438AbWEIHKw (ORCPT ); Tue, 9 May 2006 03:10:52 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:15318 "EHLO e36.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751437AbWEIHKv (ORCPT ); Tue, 9 May 2006 03:10:51 -0400 Date: Tue, 9 May 2006 12:39:11 +0530 From: Prasanna S Panchamukhi To: linux-kernel@vger.kernel.org, systemtap@sources.redhat.com Cc: akpm@osdl.org, Andi Kleen , davem@davemloft.net, suparna@in.ibm.com, richardj_moore@uk.ibm.com Subject: Re: [RFC] [PATCH 4/6] Kprobes: Insert probes on non-memory resident pages Message-ID: <20060509070911.GD22493@in.ibm.com> Reply-To: prasanna@in.ibm.com References: <20060509065455.GA11630@in.ibm.com> <20060509065917.GA22493@in.ibm.com> <20060509070106.GB22493@in.ibm.com> <20060509070508.GC22493@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060509070508.GC22493@in.ibm.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6204 Lines: 192 User-space probes also supports the registering of the probe points before the probed code is loaded. This clearly has advantages for catching initialization problems. This involves modifying the probed applications address_space readpage() and readpages(). Overhead of changing the address_space readpage/s() is limited to only the probed application until all probes are removed from that application. This patch provides the feature of inserting probes on pages that are not present in the memory during registration. To add readpage and readpages() hooks, two new elements are added to the uprobe_module object: struct address_space_operations *ori_a_ops; struct address_space_operations user_a_ops; When the pages are read into memory through the readpage and readpages address space operations, any associated probes are automatically inserted into those pages. These user-space probes readpage and readpages routines internally call the original readpage() and readpages() routines, and then check whether probes are to be added to these pages, inserting probes as necessary. During unregistration, care should be taken to replace the readpage and readpages hooks with the original routines if no probes remain on that application. Signed-of-by: Prasanna S Panchamukhi kernel/uprobes.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 121 insertions(+) diff -puN kernel/uprobes.c~kprobes_userspace_probes-hook-readpage kernel/uprobes.c --- linux-2.6.17-rc3-mm1/kernel/uprobes.c~kprobes_userspace_probes-hook-readpage 2006-05-09 10:08:49.000000000 +0530 +++ linux-2.6.17-rc3-mm1-prasanna/kernel/uprobes.c 2006-05-09 10:08:49.000000000 +0530 @@ -300,15 +300,134 @@ struct uprobe_module __kprobes *get_modu return NULL; } +static inline void insert_readpage_uprobe(struct page *page, + struct address_space *mapping, struct uprobe *uprobe) +{ + unsigned long page_start = page->index << PAGE_CACHE_SHIFT; + unsigned long page_end = page_start + PAGE_SIZE; + + if ((uprobe->offset >= page_start) && (uprobe->offset < page_end)) { + map_uprobe_page(page, uprobe, insert_kprobe_user); + flush_vma(mapping, page, uprobe); + } +} + +/* + * This function hooks the readpages() of all modules that have active + * probes on them. The original readpages() is called for the given + * inode/address_space to actually read the pages into the memory. + * Then all probes that are specified on these pages are inserted. + */ +static int __kprobes uprobe_readpages(struct file *file, + struct address_space *mapping, + struct list_head *pages, unsigned nr_pages) +{ + int retval = 0; + struct page *page; + struct uprobe_module *umodule; + struct uprobe *uprobe = NULL; + struct hlist_node *node; + + mutex_lock(&uprobe_mutex); + + umodule = get_module_by_inode(file->f_dentry->d_inode); + if (!umodule) { + /* + * No module associated with this file, call the + * original readpages(). + */ + retval = mapping->a_ops->readpages(file, mapping, + pages, nr_pages); + goto out; + } + + /* call original readpages() */ + retval = umodule->ori_a_ops->readpages(file, mapping, pages, nr_pages); + if (retval < 0) + goto out; + + /* + * TODO: Walk through readpages page list and get + * pages with probes instead of find_get_page(). + */ + hlist_for_each_entry(uprobe, node, &umodule->ulist_head, ulist) { + page = find_get_page(mapping, + uprobe->offset >> PAGE_CACHE_SHIFT); + if (!page) + continue; + + if (!uprobe->kp.opcode) + insert_readpage_uprobe(page, mapping, uprobe); + page_cache_release(page); + } + +out: + mutex_unlock(&uprobe_mutex); + + return retval; +} + +/* + * This function hooks the readpage() of all modules that have active + * probes on them. The original readpage() is called for the given + * inode/address_space to actually read the pages into the memory. + * Then all probes that are specified on this page are inserted. + */ +int __kprobes uprobe_readpage(struct file *file, struct page *page) +{ + int retval = 0; + struct uprobe_module *umodule; + struct uprobe *uprobe = NULL; + struct hlist_node *node; + struct address_space *mapping = file->f_dentry->d_inode->i_mapping; + + mutex_lock(&uprobe_mutex); + + umodule = get_module_by_inode(file->f_dentry->d_inode); + if (!umodule) { + /* + * No module associated with this file, call the + * original readpage(). + */ + retval = mapping->a_ops->readpage(file, page); + goto out; + } + + /* call original readpage() */ + retval = umodule->ori_a_ops->readpage(file, page); + if (retval < 0) + goto out; + + hlist_for_each_entry(uprobe, node, &umodule->ulist_head, ulist) { + if (!uprobe->kp.opcode) + insert_readpage_uprobe(page, mapping, uprobe); + } + +out: + mutex_unlock(&uprobe_mutex); + + return retval; +} + /* * Add uprobe and uprobe_module to the appropriate hash list. + * Also switches i_op to hooks into readpage and readpages(). */ static void __kprobes get_inode_ops(struct uprobe *uprobe, struct uprobe_module *umodule) { + struct address_space *as; + INIT_HLIST_HEAD(&umodule->ulist_head); hlist_add_head(&uprobe->ulist, &umodule->ulist_head); list_add(&umodule->mlist, &uprobe_module_list); + as = umodule->nd.dentry->d_inode->i_mapping; + umodule->ori_a_ops = as->a_ops; + umodule->user_a_ops = *as->a_ops; + umodule->user_a_ops.readpage = uprobe_readpage; + umodule->user_a_ops.readpages = uprobe_readpages; + as->a_ops = &umodule->user_a_ops; + } /* @@ -437,6 +556,8 @@ void __kprobes unregister_uprobe(struct hlist_del(&uprobe->ulist); if (hlist_empty(&umodule->ulist_head)) { list_del(&umodule->mlist); + umodule->nd.dentry->d_inode->i_mapping->a_ops = + umodule->ori_a_ops; write_access_to_inode(uprobe->inode); path_release(&umodule->nd); kfree(umodule); _ -- Prasanna S Panchamukhi Linux Technology Center India Software Labs, IBM Bangalore Email: prasanna@in.ibm.com Ph: 91-80-41776329 - 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/