Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758897AbZGGV30 (ORCPT ); Tue, 7 Jul 2009 17:29:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756525AbZGGV3R (ORCPT ); Tue, 7 Jul 2009 17:29:17 -0400 Received: from mail-fx0-f218.google.com ([209.85.220.218]:58071 "EHLO mail-fx0-f218.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756052AbZGGV3Q (ORCPT ); Tue, 7 Jul 2009 17:29:16 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=QtpMfqI5gzX4aCoTn37qbO6j8SB0huxpznv3K0F1MKsjjTp6nyXvxpsCFEjrG3Gcaq Uq1vwY4aduZOLIlcA6e+qWWrYOSWtcQWeTHDNMrD2IHzZuB2XUxV42uzymDWcZmESgob /60nUk4jpcNrCJgWpNlQFhB4VA769vMc8fmHg= Date: Tue, 7 Jul 2009 23:29:12 +0200 From: Frederic Weisbecker To: Li Zefan Cc: Ingo Molnar , "K.Prasad" , Alan Stern , Steven Rostedt , LKML Subject: Re: [PATCH 2/8] ksym_tracer: Rewrite ksym_trace_filter_read() Message-ID: <20090707212910.GB7412@nowhere> 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: 2577 Lines: 84 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. > > Also reduce stack usage by about 512 bytes. > > 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; Hehe, this trace_seq type is very convenient :) > + 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); > } > - ret = simple_read_from_buffer(ubuf, count, ppos, buf, strlen(buf)); > + > + cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len); > + > mutex_unlock(&ksym_tracer_mutex); > > - return ret; > + kfree(s); > + > + return cnt; > } > > static ssize_t ksym_trace_filter_write(struct file *file, Looks good too. Ack. -- 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/