2021-04-28 13:51:27

by Leo Yan

Subject: [PATCH v3 1/4] perf tool: Change fields type in perf_record_time_conv

C standard claims "An object declared as type _Bool is large enough to
store the values 0 and 1", bool type size can be 1 byte or larger than
1 byte. Thus it's uncertian for bool type size with different
compilers.

This patch changes the bool type in structure perf_record_time_conv to
__u8 type, and pads extra bytes for 8-byte alignment; this can give
reliable structure size.

Suggested-by: Adrian Hunter <[email protected]>
Fixes: d110162cafc8 ("perf tsc: Support cap_user_time_short for event TIME_CONV")
Signed-off-by: Leo Yan <[email protected]>
---
tools/lib/perf/include/perf/event.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index d82054225fcc..48583e441d9b 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -346,8 +346,9 @@ struct perf_record_time_conv {
__u64 time_zero;
__u64 time_cycles;
__u64 time_mask;
- bool cap_user_time_zero;
- bool cap_user_time_short;
+ __u8 cap_user_time_zero;
+ __u8 cap_user_time_short;
+ __u8 reserved[6]; /* For alignment */
};

struct perf_record_header_feature {
--
2.25.1

2021-04-28 14:54:29

by Adrian Hunter

Subject: Re: [PATCH v3 1/4] perf tool: Change fields type in perf_record_time_conv

On 28/04/21 3:09 pm, Leo Yan wrote:
> C standard claims "An object declared as type _Bool is large enough to
> store the values 0 and 1", bool type size can be 1 byte or larger than
> 1 byte. Thus it's uncertian for bool type size with different
> compilers.
>
> This patch changes the bool type in structure perf_record_time_conv to
> __u8 type, and pads extra bytes for 8-byte alignment; this can give
> reliable structure size.
>
> Suggested-by: Adrian Hunter <[email protected]>
> Fixes: d110162cafc8 ("perf tsc: Support cap_user_time_short for event TIME_CONV")
> Signed-off-by: Leo Yan <[email protected]>

Acked-by: Adrian Hunter <[email protected]>

> ---
> tools/lib/perf/include/perf/event.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
> index d82054225fcc..48583e441d9b 100644
> --- a/tools/lib/perf/include/perf/event.h
> +++ b/tools/lib/perf/include/perf/event.h
> @@ -346,8 +346,9 @@ struct perf_record_time_conv {
> __u64 time_zero;
> __u64 time_cycles;
> __u64 time_mask;
> - bool cap_user_time_zero;
> - bool cap_user_time_short;
> + __u8 cap_user_time_zero;
> + __u8 cap_user_time_short;
> + __u8 reserved[6]; /* For alignment */
> };
>
> struct perf_record_header_feature {
>