2020-10-07 18:46:03

by Axel Rasmussen

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 <[email protected]>
---
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

2020-10-08 07:29:36

by Michel Lespinasse

Subject: Re: [PATCH v2 1/2] tracing: support "bool" type in synthetic trace events

On Wed, Oct 7, 2020 at 11:44 AM Axel Rasmussen <[email protected]> wrote:
> 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.

Acked-by: Michel Lespinasse <[email protected]>

Looks fine to me, but you really want to get Steven's opinion over mine here :)