[PATCH AUTOSEL 4.20 66/81] perf trace: Support multiple "vfs_getname" probes

Sasha Levin
2019-02-28T15:10:42Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

[ Upstream commit 6ab3bc240ade47a0f52bc16d97edd9accbe0024e ]

With a suitably defined "probe:vfs_getname" probe, 'perf trace' can
"beautify" its output, so syscalls like open() or openat() can print the
"filename" argument instead of just its hex address, like:

$ perf trace -e open -- touch /dev/null
[...]
0.590 ( 0.014 ms): touch/18063 open(filename: /dev/null, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3
[...]

The output without such beautifier looks like:

0.529 ( 0.011 ms): touch/18075 open(filename: 0xc78cf288, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3

However, when the vfs_getname probe expands to multiple probes and it is
not the first one that is hit, the beautifier fails, as following:

0.326 ( 0.010 ms): touch/18072 open(filename: , flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3

Fix it by hooking into all the expanded probes (inlines), now, for instance:

[root@quaco ~]# perf probe -l
probe:vfs_getname (on getname_flags:73@fs/namei.c with pathname)
probe:vfs_getname_1 (on getname_flags:73@fs/namei.c with pathname)
[root@quaco ~]# perf trace -e open* sleep 1
0.010 ( 0.005 ms): sleep/5588 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: RDONLY|CLOEXEC) = 3
0.029 ( 0.006 ms): sleep/5588 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: RDONLY|CLOEXEC) = 3
0.194 ( 0.008 ms): sleep/5588 openat(dfd: CWD, filename: /usr/lib/locale/locale-archive, flags: RDONLY|CLOEXEC) = 3
[root@quaco ~]#

Works, further verified with:

[root@quaco ~]# perf test vfs
65: Use vfs_getname probe to get syscall args filenames : Ok
66: Add vfs_getname probe to get syscall args filenames : Ok
67: Check open filename arg using perf trace + vfs_getname: Ok
[root@quaco ~]#

Reported-by: Michael Petlan <mpetlan@redhat.com>
Tested-by: Michael Petlan <mpetlan@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-mv8kolk17xla1smvmp3qabv1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/builtin-trace.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 835619476370c..c108519ddd615 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2424,19 +2424,30 @@ static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp);

static bool perf_evlist__add_vfs_getname(struct perf_evlist *evlist)
{
- struct perf_evsel *evsel = perf_evsel__newtp("probe", "vfs_getname");
+ bool found = false;
+ struct perf_evsel *evsel, *tmp;
+ struct parse_events_error err = { .idx = 0, };
+ int ret = parse_events(evlist, "probe:vfs_getname*", &err);

- if (IS_ERR(evsel))
+ if (ret)
return false;

- if (perf_evsel__field(evsel, "pathname") == NULL) {
+ evlist__for_each_entry_safe(evlist, evsel, tmp) {
+ if (!strstarts(perf_evsel__name(evsel), "probe:vfs_getname"))
+ continue;
+
+ if (perf_evsel__field(evsel, "pathname")) {
+ evsel->handler = trace__vfs_getname;
+ found = true;
+ continue;
+ }
+
+ list_del_init(&evsel->node);
+ evsel->evlist = NULL;
perf_evsel__delete(evsel);
- return false;
}

- evsel->handler = trace__vfs_getname;
- perf_evlist__add(evlist, evsel);
- return true;
+ return found;
}

static struct perf_evsel *perf_evsel__new_pgfault(u64 config)
--
2.19.1