linux-kernel - [PATCH v2 1/2] tracing: support "bool" type in synthetic trace events

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Date:   Wed,  7 Oct 2020 11:44:02 -0700
From:   Axel Rasmussen <axelrasmussen@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michel Lespinasse <walken@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Chinwen Chang <chinwen.chang@...iatek.com>
Cc:     Yafang Shao <laoar.shao@...il.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v2 1/2] tracing: support "bool" type in synthetic trace events

It's common [1] to define tracepoint fields as "bool" when they contain
a true / false value. Currently, defining a synthetic event with a
"bool" field yields EINVAL. It's possible to work around this by using
e.g. u8 (assuming sizeof(bool) is 1, and bool is unsigned; if either of
these properties don't match, you get EINVAL [2]).

Supporting "bool" explicitly makes hooking this up easier and more
portable for userspace.

[1]: grep -r "bool" include/trace/events/
[2]: check_synth_field() in kernel/trace/trace_events_hist.c

Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>
---
 kernel/trace/trace_events_synth.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 742ce5f62d6d..92eb530ec287 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -187,6 +187,8 @@ static int synth_field_size(char *type)
 		size = sizeof(long);
 	else if (strcmp(type, "unsigned long") == 0)
 		size = sizeof(unsigned long);
+	else if (strcmp(type, "bool") == 0)
+		size = sizeof(bool);
 	else if (strcmp(type, "pid_t") == 0)
 		size = sizeof(pid_t);
 	else if (strcmp(type, "gfp_t") == 0)
@@ -229,6 +231,8 @@ static const char *synth_field_fmt(char *type)
 		fmt = "%ld";
 	else if (strcmp(type, "unsigned long") == 0)
 		fmt = "%lu";
+	else if (strcmp(type, "bool") == 0)
+		fmt = "%d";
 	else if (strcmp(type, "pid_t") == 0)
 		fmt = "%d";
 	else if (strcmp(type, "gfp_t") == 0)
-- 
2.28.0.806.g8561365e88-goog