Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751643AbZGKFyj (ORCPT ); Sat, 11 Jul 2009 01:54:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751388AbZGKFyb (ORCPT ); Sat, 11 Jul 2009 01:54:31 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:39666 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751314AbZGKFyb (ORCPT ); Sat, 11 Jul 2009 01:54:31 -0400 Date: Sat, 11 Jul 2009 11:24:18 +0530 From: "K.Prasad" To: Li Zefan Cc: Ingo Molnar , Alan Stern , Frederic Weisbecker , Steven Rostedt , LKML Subject: Re: [PATCH 2/8] ksym_tracer: Rewrite ksym_trace_filter_read() Message-ID: <20090711055418.GA7686@in.ibm.com> Reply-To: prasad@linux.vnet.ibm.com References: <4A52E291.1020408@cn.fujitsu.com> <4A52E2B4.6030706@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A52E2B4.6030706@cn.fujitsu.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 Content-Length: 2578 Lines: 77 On Tue, Jul 07, 2009 at 01:52:52PM +0800, Li Zefan wrote: > Reading ksym_trace_filter gave me some arbitrary characters, > when it should show nothing. It's because buf is not initialized > when there's no filter. > I started noticing this behaviour recently. A simple char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX] = "\0"; solves the problem. > Also reduce stack usage by about 512 bytes. > The stack usage would be much lesser on other architectures with fewer breakpoint registers (like PPC64), and should really be an issue. > Signed-off-by: Li Zefan > --- > kernel/trace/trace_ksym.c | 29 ++++++++++++++++++----------- > 1 files changed, 18 insertions(+), 11 deletions(-) > > diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c > index 085ff05..b6710d3 100644 > --- a/kernel/trace/trace_ksym.c > +++ b/kernel/trace/trace_ksym.c > @@ -35,7 +35,6 @@ > #define KSYM_TRACER_MAX HBP_NUM > > #define KSYM_TRACER_OP_LEN 3 /* rw- */ > -#define KSYM_FILTER_ENTRY_LEN (KSYM_NAME_LEN + KSYM_TRACER_OP_LEN + 1) > > struct trace_ksym { > struct hw_breakpoint *ksym_hbp; > @@ -230,25 +229,33 @@ static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf, > { > struct trace_ksym *entry; > struct hlist_node *node; > - char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX]; > - ssize_t ret, cnt = 0; > + struct trace_seq *s; > + ssize_t cnt = 0; > + int ret; > + > + s = kmalloc(sizeof(*s), GFP_KERNEL); > + if (!s) > + return -ENOMEM; > + trace_seq_init(s); > > mutex_lock(&ksym_tracer_mutex); > > hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) { > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, "%s:", > - entry->ksym_hbp->info.name); > + ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name); > if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE) > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, > - "-w-\n"); > + ret = trace_seq_puts(s, "-w-\n"); > else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW) > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, > - "rw-\n"); > + ret = trace_seq_puts(s, "rw-\n"); > + WARN_ON_ONCE(!ret); Given that this change uses the tracer defined functions and a seq-file implementation, the patch is welcome. Thanks, K.Prasad -- 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/