From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753405Ab3KSQYi (ORCPT ); Tue, 19 Nov 2013 11:24:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47320 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753363Ab3KSQYh (ORCPT ); Tue, 19 Nov 2013 11:24:37 -0500 Date: Tue, 19 Nov 2013 17:25:45 +0100 From: Oleg Nesterov To: Ingo Molnar Cc: Ingo Molnar , Srikar Dronamraju , linux-kernel@vger.kernel.org Subject: [PATCH] uprobes: Document xol_area and arch_uprobe->insn/ixol Message-ID: <20131119162545.GA776@redhat.com> References: <20131109190344.GA32281@redhat.com> <20131111084149.GC12405@gmail.com> <20131111195836.GA20615@redhat.com> <20131111210327.GG18886@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131111210327.GG18886@gmail.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 11/11, Ingo Molnar wrote: > > * Oleg Nesterov wrote: > > > On 11/11, Ingo Molnar wrote: > > > > > > You guys are changing code that reads like gobbledygook to people > > > reading it for the first time. > > > > Not that I am trying to defense uprobes, but this is equally true for > > any piece of kernel code, at least to me ;) > > I'm really not suggesting to do overly much - only for some minimal blurb > like the scheduler has in most places: OK. Let me try to make a first step to improve this a little bit... How about the patch below? Srikar? Subject: [PATCH] uprobes: Document xol_area and arch_uprobe->insn/ixol Document xol_area and arch_uprobe. Signed-off-by: Oleg Nesterov --- kernel/events/uprobes.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 51a7f53..b886a5e 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -73,6 +73,17 @@ struct uprobe { struct inode *inode; /* Also hold a ref to inode */ loff_t offset; unsigned long flags; + + /* + * The generic code assumes that it has two members of unknown type + * owned by the arch-specific code: + * + * insn - copy_insn() saves the original instruction here for + * arch_uprobe_analyze_insn(). + * + * ixol - potentially modified instruction to execute out of + * line, copied to xol_area by xol_get_insn_slot(). + */ struct arch_uprobe arch; }; @@ -86,6 +97,10 @@ struct return_instance { }; /* + * Execute out of line area: anonymous executable mapping installed + * by the probed task to execute the copy of the original instruction + * mangled by set_swbp(). + * * On a breakpoint hit, thread contests for a slot. It frees the * slot after singlestep. Currently a fixed number of slots are * allocated. -- 1.5.5.1