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Date: Mon, 20 Apr 2015 18:23:14 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: David Ahern <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>,
He Kuang <hekuang@...wei.com>, Ingo Molnar <mingo@...nel.org>,
Jeremie Galarneau <jgalar@...icios.com>,
Namhyung Kim <namhyung@...nel.org>,
Paul Mackerras <paulus@...ba.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Tom Zanussi <tzanussi@...il.com>,
Wang Nan <wangnan0@...wei.com>,
lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] perf data: Fix signess of value
Em Sat, Apr 18, 2015 at 05:50:20PM +0200, Jiri Olsa escreveu:
> From: Wang Nan <wangnan0@...wei.com>
>
> When converting int values, perf first extractes it to a ulonglong, then
> feeds it to babeltrace as a signed value. For negative 32 bit values
> (for example, return values of failed syscalls), the extracted data
> should be something like 0xfffffffe (-2). It becomes a large int64
> value. Babeltrace denies to insert it with
> bt_ctf_field_signed_integer_set_value() because it is larger than
> 0x7fffffff, the largest positive value a signed 32 bit int can be.
There is no such word "signess", it is "signedness", fixing this up.
Humm, it seems there is such a word indeed:
http://www.urbandictionary.com/define.php?term=Signess
But I bet this is the one we want:
http://en.wikipedia.org/wiki/Signedness
Right? :-)
- Arnaldo
> This patch introduces adjust_signess(), which fills high bits of
> ulonglong with 1 if the value is negative.
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Link: http://lkml.kernel.org/n/tip-bq2fguw8pm8s5rr741mmgias@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
> tools/perf/util/data-convert-bt.c | 64 +++++++++++++++++++++++++++++++--------
> 1 file changed, 52 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
> index 8eda4ed628e7..977cc3f98d8f 100644
> --- a/tools/perf/util/data-convert-bt.c
> +++ b/tools/perf/util/data-convert-bt.c
> @@ -166,6 +166,43 @@ get_tracepoint_field_type(struct ctf_writer *cw, struct format_field *field)
> return cw->data.u32;
> }
>
> +static unsigned long long adjust_signess(unsigned long long value_int, int size)
> +{
> + unsigned long long value_mask;
> +
> + /*
> + * value_mask = (1 << (size * 8 - 1)) - 1.
> + * Directly set value_mask for code readers.
> + */
> + switch (size) {
> + case 1:
> + value_mask = 0x7fULL;
> + break;
> + case 2:
> + value_mask = 0x7fffULL;
> + break;
> + case 4:
> + value_mask = 0x7fffffffULL;
> + break;
> + case 8:
> + /*
> + * For 64 bit value, return it self. There is no need
> + * to fill high bit.
> + */
> + /* Fall through */
> + default:
> + /* BUG! */
> + return value_int;
> + }
> +
> + /* If it is a positive value, don't adjust. */
> + if ((value_int & (~0ULL - value_mask)) == 0)
> + return value_int;
> +
> + /* Fill upper part of value_int with 1 to make it a negative long long. */
> + return (value_int & value_mask) | ~value_mask;
> +}
> +
> static int add_tracepoint_field_value(struct ctf_writer *cw,
> struct bt_ctf_event_class *event_class,
> struct bt_ctf_event *event,
> @@ -177,7 +214,6 @@ static int add_tracepoint_field_value(struct ctf_writer *cw,
> struct bt_ctf_field *field;
> const char *name = fmtf->name;
> void *data = sample->raw_data;
> - unsigned long long value_int;
> unsigned long flags = fmtf->flags;
> unsigned int n_items;
> unsigned int i;
> @@ -222,11 +258,6 @@ static int add_tracepoint_field_value(struct ctf_writer *cw,
> type = get_tracepoint_field_type(cw, fmtf);
>
> for (i = 0; i < n_items; i++) {
> - if (!(flags & FIELD_IS_STRING))
> - value_int = pevent_read_number(
> - fmtf->event->pevent,
> - data + offset + i * len, len);
> -
> if (flags & FIELD_IS_ARRAY)
> field = bt_ctf_field_array_get_field(array_field, i);
> else
> @@ -240,12 +271,21 @@ static int add_tracepoint_field_value(struct ctf_writer *cw,
> if (flags & FIELD_IS_STRING)
> ret = bt_ctf_field_string_set_value(field,
> data + offset + i * len);
> - else if (!(flags & FIELD_IS_SIGNED))
> - ret = bt_ctf_field_unsigned_integer_set_value(
> - field, value_int);
> - else
> - ret = bt_ctf_field_signed_integer_set_value(
> - field, value_int);
> + else {
> + unsigned long long value_int;
> +
> + value_int = pevent_read_number(
> + fmtf->event->pevent,
> + data + offset + i * len, len);
> +
> + if (!(flags & FIELD_IS_SIGNED))
> + ret = bt_ctf_field_unsigned_integer_set_value(
> + field, value_int);
> + else
> + ret = bt_ctf_field_signed_integer_set_value(
> + field, adjust_signess(value_int, len));
> + }
> +
> if (ret) {
> pr_err("failed to set file value %s\n", name);
> goto err_put_field;
> --
> 1.9.3
--
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