linux-kernel - Re: [PATCH] tracing: FTRACE_ITER

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Date:	Wed, 19 Aug 2009 09:18:43 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: FTRACE_ITER_CONT handling fix

On Tue, Aug 18, 2009 at 09:01:08PM -0400, Steven Rostedt wrote:
> 
> On Tue, 11 Aug 2009, Jiri Olsa wrote:
> 
> > Hi,
> > 
> > if one filter item (for set_ftrace_filter and set_ftrace_notrace) is being 
> > setup by more than 1 consecutive writes (FTRACE_ITER_CONT flag), it won't
> > be handled corretly.
> > 
> > I used following program to test/verify:
> > 
> > [snip]
> > #include <stdio.h>
> > #include <sys/types.h>
> > #include <sys/stat.h>
> > #include <fcntl.h>
> > #include <string.h>
> > 
> > int main(int argc, char **argv)
> > {
> >         int fd, i;
> >         char *file = argv[1];
> > 
> >         if (-1 == (fd = open(file, O_WRONLY))) {
> >                 perror("open failed");
> >                 return -1;
> >         }
> > 
> >         for(i = 0; i < (argc - 2); i++) {
> >                 int len = strlen(argv[2+i]);
> >                 int cnt, off = 0;
> > 
> >                 while(len) {
> >                         cnt = write(fd, argv[2+i] + off, len);
> >                         len -= cnt;
> >                         off += cnt;
> >                 }
> >         }
> > 
> >         close(fd);
> >         return 0;
> > }
> > [snip]
> 
> BTW, you did not need to make such a test, just doing:
> 
>  # echo sys_open | dd of=set_ftrace_filter bs=2
> 
> works as well.
> 

cool :) thanks

jirka

> 
> > 
> > before change:
> > sh-4.0# echo > ./set_ftrace_filter 
> > sh-4.0# /test ./set_ftrace_filter "sys" "_open "
> > sh-4.0# cat ./set_ftrace_filter 
> > #### all functions enabled ####
> > sh-4.0# 
> > 
> > after change:
> > sh-4.0# echo > ./set_ftrace_notrace   
> > sh-4.0# test ./set_ftrace_notrace "sys" "_open "
> > sh-4.0# cat ./set_ftrace_notrace 
> > sys_open
> > sh-4.0# 
> > 
> > wbr,
> > jirka
> > 
> > 
> > Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> 
> Thanks, applied!
> 
> -- Steve
> 
> > 
> > ---
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 0948634..da0757a 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -2233,7 +2233,11 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
> >  	read++;
> >  	cnt--;
> >  
> > -	if (!(iter->flags & ~FTRACE_ITER_CONT)) {
> > +	/*
> > +	 * If the parser haven't finished with the last write,
> > +	 * continue reading the user input without skipping spaces.
> > +	 */
> > +	if (!(iter->flags & FTRACE_ITER_CONT)) {
> >  		/* skip white space */
> >  		while (cnt && isspace(ch)) {
> >  			ret = get_user(ch, ubuf++);
> > @@ -2243,8 +2247,9 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
> >  			cnt--;
> >  		}
> >  
> > +		/* only spaces were written */
> >  		if (isspace(ch)) {
> > -			file->f_pos += read;
> > +			*ppos += read;
> >  			ret = read;
> >  			goto out;
> >  		}
> > @@ -2273,12 +2278,12 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
> >  		if (ret)
> >  			goto out;
> >  		iter->buffer_idx = 0;
> > -	} else
> > +	} else {
> >  		iter->flags |= FTRACE_ITER_CONT;
> > +		iter->buffer[iter->buffer_idx++] = ch;
> > +	}
> >  
> > -
> > -	file->f_pos += read;
> > -
> > +	*ppos += read;
> >  	ret = read;
> >   out:
> >  	mutex_unlock(&ftrace_regex_lock);
> > 
--
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