[PATCH] tracing user_events: Simplify user_event_parse_field() parsing

[PATCH] tracing user_events: Simplify user_event_parse_field() parsing

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Instead of having a bunch of if statements with:

       len = str_has_prefix(field, "__data_loc unsigned ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__data_loc ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__rel_loc unsigned ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__rel_loc ");
       if (len)
               goto skip_next;

	goto parse;

 skip_next:

Consolidate it into a negative check and jump to parse if all the
str_has_prefix() calls fail. If one succeeds, it will just continue with
len equal to the proper string:

       if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
           !(len = str_has_prefix(field, "__data_loc ")) &&
           !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
           !(len = str_has_prefix(field, "__rel_loc "))) {
               goto parse;
       }

 skip_next:

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_user.c | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 9365ce407426..ce0c5f1ded48 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1175,23 +1175,13 @@ static int user_event_parse_field(char *field, struct user_event *user,
 		goto skip_next;
 	}
 
-	len = str_has_prefix(field, "__data_loc unsigned ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__data_loc ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__rel_loc unsigned ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__rel_loc ");
-	if (len)
-		goto skip_next;
+	if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
+	    !(len = str_has_prefix(field, "__data_loc ")) &&
+	    !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
+	    !(len = str_has_prefix(field, "__rel_loc "))) {
+		goto parse;
+	}
 
-	goto parse;
 skip_next:
 	type = field;
 	field = strpbrk(field + len, " ");
-- 
2.43.0

Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

[Beau Belgrave]

On Mon, Jan 08, 2024 at 01:37:23PM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> Instead of having a bunch of if statements with:
> 
>        len = str_has_prefix(field, "__data_loc unsigned ");
>        if (len)
>                goto skip_next;
> 
>        len = str_has_prefix(field, "__data_loc ");
>        if (len)
>                goto skip_next;
> 
>        len = str_has_prefix(field, "__rel_loc unsigned ");
>        if (len)
>                goto skip_next;
> 
>        len = str_has_prefix(field, "__rel_loc ");
>        if (len)
>                goto skip_next;
> 
> 	goto parse;
> 
>  skip_next:
> 
> Consolidate it into a negative check and jump to parse if all the
> str_has_prefix() calls fail. If one succeeds, it will just continue with
> len equal to the proper string:
> 
>        if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
>            !(len = str_has_prefix(field, "__data_loc ")) &&
>            !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
>            !(len = str_has_prefix(field, "__rel_loc "))) {
>                goto parse;
>        }
> 
>  skip_next:
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/trace_events_user.c | 22 ++++++----------------
>  1 file changed, 6 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 9365ce407426..ce0c5f1ded48 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1175,23 +1175,13 @@ static int user_event_parse_field(char *field, struct user_event *user,
>  		goto skip_next;
>  	}
>  
> -	len = str_has_prefix(field, "__data_loc unsigned ");
> -	if (len)
> -		goto skip_next;
> -
> -	len = str_has_prefix(field, "__data_loc ");
> -	if (len)
> -		goto skip_next;
> -
> -	len = str_has_prefix(field, "__rel_loc unsigned ");
> -	if (len)
> -		goto skip_next;
> -
> -	len = str_has_prefix(field, "__rel_loc ");
> -	if (len)
> -		goto skip_next;
> +	if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> +	    !(len = str_has_prefix(field, "__data_loc ")) &&
> +	    !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> +	    !(len = str_has_prefix(field, "__rel_loc "))) {
> +		goto parse;
> +	}

This now triggers a checkpatch error:
ERROR: do not use assignment in if condition
#1184: FILE: kernel/trace/trace_events_user.c:1184:
+       if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&

I personally prefer to keep these files fully checkpatch clean.
However, I did test these changes under the self-tests and it passed.

Do they bug you that much? :)

Thanks,
-Beau

>  
> -	goto parse;
>  skip_next:
>  	type = field;
>  	field = strpbrk(field + len, " ");
> -- 
> 2.43.0

Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

[Steven Rostedt]

On Mon, 8 Jan 2024 21:47:44 +0000
Beau Belgrave <beaub@linux.microsoft.com> wrote:

> > -	len = str_has_prefix(field, "__rel_loc ");
> > -	if (len)
> > -		goto skip_next;
> > +	if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> > +	    !(len = str_has_prefix(field, "__data_loc ")) &&
> > +	    !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> > +	    !(len = str_has_prefix(field, "__rel_loc "))) {
> > +		goto parse;
> > +	}  
> 
> This now triggers a checkpatch error:
> ERROR: do not use assignment in if condition

What a horrible message.

> #1184: FILE: kernel/trace/trace_events_user.c:1184:
> +       if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> 
> I personally prefer to keep these files fully checkpatch clean.

I've stopped using checkpatch years ago because I disagreed with so much it :-p
  (Including this message)

> However, I did test these changes under the self-tests and it passed.
> 
> Do they bug you that much? :)

No big deal if you prefer the other way. I was just doing an audit of
str_has_prefix() to see what code could be cleaned up that uses it, and I
found this code.

If you prefer to limit your code to "checkpatch clean", I'll leave it alone.

-- Steve

Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

[Steven Rostedt]

On Mon, 8 Jan 2024 17:13:12 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 8 Jan 2024 21:47:44 +0000
> Beau Belgrave <beaub@linux.microsoft.com> wrote:
> 
> > > -	len = str_has_prefix(field, "__rel_loc ");
> > > -	if (len)
> > > -		goto skip_next;
> > > +	if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> > > +	    !(len = str_has_prefix(field, "__data_loc ")) &&
> > > +	    !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> > > +	    !(len = str_has_prefix(field, "__rel_loc "))) {
> > > +		goto parse;
> > > +	}    
> > 
> > This now triggers a checkpatch error:
> > ERROR: do not use assignment in if condition  
> 
> What a horrible message.
> 
> > #1184: FILE: kernel/trace/trace_events_user.c:1184:
> > +       if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> > 
> > I personally prefer to keep these files fully checkpatch clean.  
> 
> I've stopped using checkpatch years ago because I disagreed with so much it :-p
>   (Including this message)

Note that checkpatch is a guideline and not a rule. The general rule is, if
the code looks worse when applying the checkpatch rule, don't do it.

- Steve