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Subject[tip:perf/core] perf trace: Check and discard not only 'nr' but also '__syscall_nr'
Commit-ID:  c42de706dad3f39c1f65e473a1d165ea33f8b6e8
Gitweb: http://git.kernel.org/tip/c42de706dad3f39c1f65e473a1d165ea33f8b6e8
Author: Taeung Song <treeze.taeung@gmail.com>
AuthorDate: Fri, 26 Feb 2016 22:14:25 +0900
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 29 Feb 2016 11:34:28 -0300

perf trace: Check and discard not only 'nr' but also '__syscall_nr'

Format fields of a syscall have the first variable '__syscall_nr' or
'nr' that mean the syscall number. But it isn't relevant here so drop
it.

'nr' among fields of syscall was renamed '__syscall_nr'. So add
exception handling to drop '__syscall_nr' and modify the comment for
this excpetion handling.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1456492465-5946-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 26a337f..8dc98c5 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1725,8 +1725,12 @@ static int trace__read_syscall_info(struct trace *trace, int id)

sc->args = sc->tp_format->format.fields;
sc->nr_args = sc->tp_format->format.nr_fields;
- /* drop nr field - not relevant here; does not exist on older kernels */
- if (sc->args && strcmp(sc->args->name, "nr") == 0) {
+ /*
+ * We need to check and discard the first variable '__syscall_nr'
+ * or 'nr' that mean the syscall number. It is needless here.
+ * So drop '__syscall_nr' or 'nr' field but does not exist on older kernels.
+ */
+ if (sc->args && (!strcmp(sc->args->name, "__syscall_nr") || !strcmp(sc->args->name, "nr"))) {
sc->args = sc->args->next;
--sc->nr_args;
}
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