[PATCH v2] trace-cmd record: Fix syntax in make_pid_filter

[PATCH v2] trace-cmd record: Fix syntax in make_pid_filter

[Will Hawkins]

In older versions of the kernel, event filtering by
pid does not use the set_event_pid file. Instead,
ftrace uses a common filter (created in make_pid_filter)
to filter events based on PID.

The syntax of the filter generated by this function is
overly permissive. When filtering by pid, || is used
where && should be (in certain cases) which means that
unrelated events are captured.

Signed-off-by: Will Hawkins <hawkinsw@borlaugic.com>
---
 trace-record.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/trace-record.c b/trace-record.c
index a0b6541..741fe53 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -935,14 +935,16 @@ static char *make_pid_filter(char *curr_filter, const char *field)
 	str = filter + curr_len;
 
 	for (p = filter_pids; p; p = p->next) {
-		if (p == filter_pids)
-			orit = "";
-		else
-			orit = "||";
-		if (p->exclude)
+		if (p->exclude) {
 			match = "!=";
-		else
+			orit = "&&";
+		} else {
 			match = "==";
+			orit = "||";
+		}
+		if (p == filter_pids)
+			orit = "";
+
 		len = sprintf(str, "%s(%s%s%d)", orit, field, match, p->pid);
 		str += len;
 	}
-- 
2.7.4

Re: [PATCH v2] trace-cmd record: Fix syntax in make_pid_filter

[Will Hawkins]

Mr. Rostedt,

Just wanted to make sure there was nothing else you thought I should
modify for this patch. If there is, please let me know. I am eager to
fix anything that you think could make it better!

I hope that you had a great weekend!
Will


On Fri, Oct 13, 2017 at 2:40 PM, Will Hawkins <hawkinsw@borlaugic.com> wrote:
> In older versions of the kernel, event filtering by
> pid does not use the set_event_pid file. Instead,
> ftrace uses a common filter (created in make_pid_filter)
> to filter events based on PID.
>
> The syntax of the filter generated by this function is
> overly permissive. When filtering by pid, || is used
> where && should be (in certain cases) which means that
> unrelated events are captured.
>
> Signed-off-by: Will Hawkins <hawkinsw@borlaugic.com>
> ---
>  trace-record.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/trace-record.c b/trace-record.c
> index a0b6541..741fe53 100644
> --- a/trace-record.c
> +++ b/trace-record.c
> @@ -935,14 +935,16 @@ static char *make_pid_filter(char *curr_filter, const char *field)
>         str = filter + curr_len;
>
>         for (p = filter_pids; p; p = p->next) {
> -               if (p == filter_pids)
> -                       orit = "";
> -               else
> -                       orit = "||";
> -               if (p->exclude)
> +               if (p->exclude) {
>                         match = "!=";
> -               else
> +                       orit = "&&";
> +               } else {
>                         match = "==";
> +                       orit = "||";
> +               }
> +               if (p == filter_pids)
> +                       orit = "";
> +
>                 len = sprintf(str, "%s(%s%s%d)", orit, field, match, p->pid);
>                 str += len;
>         }
> --
> 2.7.4
>

Re: [PATCH v2] trace-cmd record: Fix syntax in make_pid_filter

[Steven Rostedt]

On Mon, 23 Oct 2017 16:41:22 -0400
Will Hawkins <hawkinsw@borlaugic.com> wrote:

> Mr. Rostedt,
> 
> Just wanted to make sure there was nothing else you thought I should
> modify for this patch. If there is, please let me know. I am eager to
> fix anything that you think could make it better!
> 

I already applied this (not sure I pushed it out yet). But forgot to
tell you that I have.

Thanks!

-- Steve