Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756167Ab2HNObV (ORCPT ); Tue, 14 Aug 2012 10:31:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19841 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752817Ab2HNObT (ORCPT ); Tue, 14 Aug 2012 10:31:19 -0400 Date: Tue, 14 Aug 2012 16:27:36 +0200 From: Oleg Nesterov To: Sebastian Andrzej Siewior Cc: Ananth N Mavinakayanahalli , linux-kernel@vger.kernel.org, x86@kernel.org, Peter Zijlstra , Arnaldo Carvalho de Melo , Roland McGrath , Srikar Dronamraju , stan_shebs@mentor.com Subject: Re: [PATCH v2 2/5] x86/uprobes: implement x86 specific arch_uprobe_*_step Message-ID: <20120814142736.GA8123@redhat.com> References: <1344355952-2382-1-git-send-email-bigeasy@linutronix.de> <1344355952-2382-3-git-send-email-bigeasy@linutronix.de> <20120808125709.GA4504@redhat.com> <50226700.9000606@linutronix.de> <20120808145345.GA8171@redhat.com> <20120809044356.GA3163@in.ibm.com> <20120809170953.GA27835@linutronix.de> <20120813132443.GB5269@redhat.com> <502A0C43.2000906@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <502A0C43.2000906@linutronix.de> 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 Content-Length: 1933 Lines: 63 On 08/14, Sebastian Andrzej Siewior wrote: > > On 08/13/2012 03:24 PM, Oleg Nesterov wrote: >> >> this patch still adds restore_flags into arch_uprobe_task. > > Yes, but OOPS. Yes, we need a new member in ->utask now to record the state of TIF_SINGLESTEP (X86_EFLAGS_TF actually). I meant that, since the patch still uses TIF_SINGLESTEP, arch_uprobe_disable_step() can check it but somehow I forgot that since arch_uprobe_enable_step() still does user_enable_single_step() TIF_SINGLESTEP is always set. >>> static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn) >>> { >>> - bool fix_ip = true, fix_call = false; /* defaults */ >>> + bool fix_ip = true, fix_call = false, fix_tf = false; /* defaults */ >>> int reg; >>> >>> insn_get_opcode(insn); /* should be a nop */ >>> >>> switch (OPCODE1(insn)) { >>> + case 0x9d: >>> + /* popf */ >>> + fix_tf = true; >>> + break; >>> case 0xc3: /* ret/lret */ >>> case 0xcb: >>> case 0xc2: >>> @@ -277,6 +284,8 @@ static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn) >>> auprobe->fixups |= UPROBE_FIX_IP; >>> if (fix_call) >>> auprobe->fixups |= UPROBE_FIX_CALL; >>> + if (fix_tf) >>> + auprobe->fixups |= UPROBE_TF_CHANGES; >>> } >> >> I won't insist, but do we really need fix_tf? "case 0x9d" could simply >> add UPROBE_TF_CHANGES. > > if it is not 0x9d (in most cases) we need to decide on per-process > basis (not per-breakpoint) whether the task has gdb watching it or not. Yes, yes, I see, thanks. But this doesn't explain why do we need to add the new variable, fix_tf. case 0x9d: auprobe->fixups |= UPROBE_TF_CHANGES; break; seems enough. Oleg. -- 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/