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SubjectRe: [PATCH 10/10] perf script python: Fix string vs byte array resolving
On Mon, Jul 11, 2016 at 11:54:52AM -0400, Steven Rostedt wrote:
> On Sun, 10 Jul 2016 13:08:02 +0200
> Jiri Olsa <jolsa@kernel.org> wrote:
>
> > Jirka reported that python code returns all arrays as strings.
> > This makes impossible to get all items for byte array tracepoint
> > field containing 0x00 value item.
> >
> > Fixing this by scanning full length of the array and returning
> > it as PyByteArray object in case non printable byte is found.
> >
> > Cc: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
> > Reported-and-tested-by: Jiri Pirko <jiri@mellanox.com>
> > Link: http://lkml.kernel.org/n/tip-22f4vhhz5uytegkggy1on8u3@git.kernel.org
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > .../util/scripting-engines/trace-event-python.c | 34 ++++++++++++++++++----
> > 1 file changed, 28 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
> > index ff134700bf30..75e9790ebb96 100644
> > --- a/tools/perf/util/scripting-engines/trace-event-python.c
> > +++ b/tools/perf/util/scripting-engines/trace-event-python.c
> > @@ -386,6 +386,16 @@ exit:
> > return pylist;
> > }
> >
> > +static int is_printable_array(char *p, unsigned int len)
> > +{
> > + unsigned int i;
> > +
> > + for (i = 0; i < len; i++)
> > + if (!isprint(p[i]) && !isspace(p[i]))
> > + return 0;
>
> I believe this will return the wrong result if you pass in a string
> that has '\0' in it. Try it out:
>
> char a[] = "hello";
>
> printf("a=%s is %d\n", a, is_printable_array(a, sizeof(a)));
>
> and see what you get?

ugh, forgot the last 0 byte.. how about attached change?

I wonder it'd be less pain to present all arrays as
PyByteArray, it might be no difference for python
users anyway ;-)

thanks,
jirka


---
diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 75e9790ebb96..9f810e6c739a 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -390,11 +390,13 @@ static int is_printable_array(char *p, unsigned int len)
{
unsigned int i;

- for (i = 0; i < len; i++)
+ /* Exclude the last zero byte of string.. */
+ for (i = 0; i < len - 1; i++)
if (!isprint(p[i]) && !isspace(p[i]))
return 0;

- return 1;
+ /* ... and check its presence in the last byte. */
+ return p[i] == 0;
}

static void python_process_tracepoint(struct perf_sample *sample,
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