linux-kernel - [PATCH v2] trace-cmd record: Fix syntax in make_pid

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Date:   Fri, 13 Oct 2017 14:40:06 -0400
From:   Will Hawkins <hawkinsw@...laugic.com>
To:     linux-kernel@...r.kernel.org, hawkinsw@...il.com,
        rostedt@...dmis.org
Cc:     Will Hawkins <hawkinsw@...laugic.com>
Subject: [PATCH v2] trace-cmd record: Fix syntax in make_pid_filter

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@...laugic.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