From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755773Ab3KLTTc (ORCPT ); Tue, 12 Nov 2013 14:19:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:8442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752852Ab3KLTTa (ORCPT ); Tue, 12 Nov 2013 14:19:30 -0500 Date: Tue, 12 Nov 2013 20:20:38 +0100 From: Oleg Nesterov To: Srikar Dronamraju Cc: Ananth N Mavinakayanahalli , Ingo Molnar , Masami Hiramatsu , Namhyung Kim , Steven Rostedt , linux-kernel@vger.kernel.org Subject: [PATCH v2] uprobes: Add uprobe_task->dup_work/dup_addr Message-ID: <20131112192038.GA7748@redhat.com> References: <20131108190003.GA12755@redhat.com> <20131111071151.GA2559@linux.vnet.ibm.com> <20131111165543.GA12233@redhat.com> <20131112174302.GH2559@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131112174302.GH2559@linux.vnet.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/12, Srikar Dronamraju wrote: > > Okay, moving to arch_uprobe_task is fine. I probably got confused by > "First of all it is not really needed," OK, this doesn't look good, I agree. Please see v2 below, I tried to improve the changelog. > > OK. How about dup_xol_work/dup_xol_vaddr ? > > Yes fine with me. Done. I added your ack optimistically, please let me know if you think I should change something else. Oleg. --- Subject: [PATCH] uprobes: Add uprobe_task->dup_xol_work/dup_xol_addr uprobe_task->vaddr is a bit strange. The generic code uses it only to pass the additional argument to arch_uprobe_pre_xol(), and since it is always equal to instruction_pointer() this looks even more strange. And both utask->vaddr and and utask->autask have the same scope, they only have the meaning when the task executes the probed insn out-of-line, so it is safe to reuse both in UTASK_RUNNING state. This all means that logically ->vaddr belongs to arch_uprobe_task and we should probably move it there, arch_uprobe_pre_xol() can record instruction_pointer() itself. OTOH, it is also used by uprobe_copy_process() and dup_xol_work() for another purpose, this doesn't look clean and doesn't allow to move this member into arch_uprobe_task. This patch adds the union with 2 anonymous structs into uprobe_task. The first struct is autask + vaddr, this way we "almost" move vaddr into autask. The second struct has 2 new members for uprobe_copy_process() paths: ->dup_xol_addr which can be used instead ->vaddr, and ->dup_xol_work which can be used to avoid kmalloc() and simplify the code. Note that this union will likely have another member(s), we need something like "private_data_for_handlers" so that the tracing handlers could use it to communicate with call_fetch() methods. Signed-off-by: Oleg Nesterov Reviewed-by: Masami Hiramatsu Acked-by: Srikar Dronamraju --- include/linux/uprobes.h | 21 ++++++++++++++++----- kernel/events/uprobes.c | 16 ++++------------ 2 files changed, 20 insertions(+), 17 deletions(-) diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index 319eae7..2225542 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -26,6 +26,7 @@ #include #include +#include struct vm_area_struct; struct mm_struct; @@ -72,14 +73,24 @@ enum uprobe_task_state { */ struct uprobe_task { enum uprobe_task_state state; - struct arch_uprobe_task autask; - struct return_instance *return_instances; - unsigned int depth; - struct uprobe *active_uprobe; + union { + struct { + struct arch_uprobe_task autask; + unsigned long vaddr; + }; + + struct { + struct callback_head dup_xol_work; + unsigned long dup_xol_addr; + }; + }; + struct uprobe *active_uprobe; unsigned long xol_vaddr; - unsigned long vaddr; + + struct return_instance *return_instances; + unsigned int depth; }; /* diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 24b7d6c..df4ef09 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1403,12 +1403,10 @@ static void uprobe_warn(struct task_struct *t, const char *msg) static void dup_xol_work(struct callback_head *work) { - kfree(work); - if (current->flags & PF_EXITING) return; - if (!__create_xol_area(current->utask->vaddr)) + if (!__create_xol_area(current->utask->dup_xol_addr)) uprobe_warn(current, "dup xol area"); } @@ -1419,7 +1417,6 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags) { struct uprobe_task *utask = current->utask; struct mm_struct *mm = current->mm; - struct callback_head *work; struct xol_area *area; t->utask = NULL; @@ -1441,14 +1438,9 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags) if (mm == t->mm) return; - /* TODO: move it into the union in uprobe_task */ - work = kmalloc(sizeof(*work), GFP_KERNEL); - if (!work) - return uprobe_warn(t, "dup xol area"); - - t->utask->vaddr = area->vaddr; - init_task_work(work, dup_xol_work); - task_work_add(t, work, true); + t->utask->dup_xol_addr = area->vaddr; + init_task_work(&t->utask->dup_xol_work, dup_xol_work); + task_work_add(t, &t->utask->dup_xol_work, true); } /* -- 1.5.5.1