Hi Arnaldo, Adrian,

On Mon, Jul 12, 2021 at 03:14:35PM -0300, Arnaldo Carvalho de Melo wrote:

Em Sun, Jul 11, 2021 at 06:41:04PM +0800, Leo Yan escreveu:

quoted

It's useful to know that the kernel is running in 32-bit or 64-bit
mode.  E.g. We can decide if perf tool is running in compat mode
from this info.

This patch adds a global variable "kernel_is_64_bit", it's initialized
when a session setups environment, its value is decided by checking the
architecture string.

Signed-off-by: Leo Yan <redacted>
---
 tools/perf/util/env.c | 17 ++++++++++++++++-
 tools/perf/util/env.h |  1 +
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index ebc5e9ad35db..345635a2e842 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c

@@ -11,6 +11,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+int kernel_is_64_bit;
 struct perf_env perf_env;

Why can't this be in 'struct perf_env'?

Good question.  I considered to add it in struct perf_env but finally
I used this way; the reason is this variable "kernel_is_64_bit" is only
used during recording phase for AUX ring buffer, and don't use it for
report.  So seems to me it's over complexity to add a new field and
just wander if it's necessary to save this field as new feature in the
perf header.

Combining the comment from Adrian in another email, I think it's good
to add a new field "compat_mode" in the struct perf_env, and this field
will be initialized in build-record.c.  Currently we don't need to save
this value into the perf file, if later we need to use this value for
decoding phase, then we can add a new feature item to save "compat_mode"
into the perf file's header.

If you have any different idea, please let me know.  Thanks!

Leo