Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763032AbYBFMxx (ORCPT ); Wed, 6 Feb 2008 07:53:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762517AbYBFMxn (ORCPT ); Wed, 6 Feb 2008 07:53:43 -0500 Received: from mx1.redhat.com ([66.187.233.31]:51775 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762033AbYBFMxm (ORCPT ); Wed, 6 Feb 2008 07:53:42 -0500 Message-ID: <47A9AD63.6060200@redhat.com> Date: Wed, 06 Feb 2008 07:51:47 -0500 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: "Luck, Tony" CC: Ananth N Mavinakayanahalli , Jim Keniston , "Li, Shaohua" , LKML , ia64 , systemtap-ml Subject: Re: [RFC][PATCH] kprobes: kprobe-booster for ia64 References: <47A8E995.1090400@redhat.com> <1FE6DD409037234FAB833C420AA843EC84804C@orsmsx424.amr.corp.intel.com> In-Reply-To: <1FE6DD409037234FAB833C420AA843EC84804C@orsmsx424.amr.corp.intel.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1702 Lines: 49 Hello Tony, Thank you for review. Luck, Tony wrote: > +/* Insert a long branch code */ > +static void __kprobes set_brl_inst(void *from, void *to) > +{ > + s64 rel = ((s64) to - (s64) from) >> 4; > + bundle_t *brl; > + brl = (bundle_t *) ((u64) from & ~0xf); > + brl->quad0.template = 0x05; /* [MLX](stop) */ > + brl->quad0.slot0 = NOP_M_INST; /* nop.m 0x0 */ > + brl->quad0.slot1_p0 = ((rel >> 20) & 0x7fffffffff) << 2; > + brl->quad1.slot1_p1 = (((rel >> 20) & 0x7fffffffff) << 2) >> (64 - 46); > + /* brl.cond.sptk.many.clr rel<<4 (qp=0) */ > + brl->quad1.slot2 = BRL_INST(rel >> 59, rel & 0xfffff); > +} > > Is this function operating directly on the instruction bundle in the > kernel code? If so, the bundle will contain some "interesting" > intermediate values as each of the "brl->xxx = yyy;" are processed. > If another cpu should try to execute this bundle while the modifications > are in progress, then the results will be not what you want. No, this function writes brl on kprobe's instruction buffer (kprobe.ainsn.insn->bundle[1]) when preparing the kprobe. So, other cpu never execute it, and we don't need to write it atomically. > On cpu models that support st16 you could construct the brl instruction > and use a single st16 to update the whole bundle atomically. > > -Tony Thank you again, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@redhat.com -- 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/