[PATCH V2 03/10] perf script: Add option to list dlfilters

Adrian Hunter
2021-06-27T13:18:15Z

Add option --list-dlfilters to list dlfilters in the current directory or
the exec-path e.g. ~/libexec/perf-core/dlfilters. Use with option -v (must
come before option --list-dlfilters) to show long descriptions.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/Documentation/perf-dlfilter.txt | 4 +
tools/perf/Documentation/perf-script.txt | 4 +
tools/perf/builtin-script.c | 2 +
tools/perf/util/dlfilter.c | 117 ++++++++++++++++++++-
tools/perf/util/dlfilter.h | 2 +
tools/perf/util/perf_dlfilter.h | 6 ++
6 files changed, 134 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-dlfilter.txt b/tools/perf/Documentation/perf-dlfilter.txt
index aef1c32babd1..8bc219f3eb83 100644
--- a/tools/perf/Documentation/perf-dlfilter.txt
+++ b/tools/perf/Documentation/perf-dlfilter.txt
@@ -37,6 +37,7 @@ int start(void **data, void *ctx);
int stop(void *data, void *ctx);
int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx);
int filter_event_early(void *data, const struct perf_dlfilter_sample *sample, void *ctx);
+const char *filter_description(const char **long_description);
----

If implemented, 'start' will be called at the beginning, before any
@@ -59,6 +60,9 @@ error code. 'data' is set by 'start'. 'ctx' is needed for calls to
'filter_event_early' is the same as 'filter_event' except it is called before
internal filtering.

+If implemented, 'filter_description' should return a one-line description
+of the filter, and optionally a longer description.
+
The perf_dlfilter_sample structure
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
index 2306c81b606b..d2705d6b9874 100644
--- a/tools/perf/Documentation/perf-script.txt
+++ b/tools/perf/Documentation/perf-script.txt
@@ -102,6 +102,10 @@ OPTIONS
Filter sample events using the given shared object file.
Refer linkperf:perf-dlfilter[1]

+--list-dlfilters=::
+ Display a list of available dlfilters. Use with option -v (must come
+ before option --list-dlfilters) to show long descriptions.
+
-a::
Force system-wide collection. Scripts run without a <command>
normally use -a by default, while scripts run with a <command>
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index e47affe674a5..4ffba1dbc55d 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -3631,6 +3631,8 @@ int cmd_script(int argc, const char **argv)
"show latency attributes (irqs/preemption disabled, etc)"),
OPT_CALLBACK_NOOPT('l', "list", NULL, NULL, "list available scripts",
list_available_scripts),
+ OPT_CALLBACK_NOOPT(0, "list-dlfilters", NULL, NULL, "list available dlfilters",
+ list_available_dlfilters),
OPT_CALLBACK('s', "script", NULL, "name",
"script file name (lang:script name, script name, or *)",
parse_scriptname),
diff --git a/tools/perf/util/dlfilter.c b/tools/perf/util/dlfilter.c
index e93c49c07999..288a2b57378c 100644
--- a/tools/perf/util/dlfilter.c
+++ b/tools/perf/util/dlfilter.c
@@ -6,6 +6,8 @@
#include <dlfcn.h>
#include <stdlib.h>
#include <string.h>
+#include <dirent.h>
+#include <subcmd/exec-cmd.h>
#include <linux/zalloc.h>
#include <linux/build_bug.h>

@@ -136,6 +138,35 @@ static const struct perf_dlfilter_fns perf_dlfilter_fns = {
.resolve_addr = dlfilter__resolve_addr,
};

+static char *find_dlfilter(const char *file)
+{
+ char path[PATH_MAX];
+ char *exec_path;
+
+ if (strchr(file, '/'))
+ goto out;
+
+ if (!access(file, R_OK)) {
+ /*
+ * Prepend "./" so that dlopen will find the file in the
+ * current directory.
+ */
+ snprintf(path, sizeof(path), "./%s", file);
+ file = path;
+ goto out;
+ }
+
+ exec_path = get_argv_exec_path();
+ if (!exec_path)
+ goto out;
+ snprintf(path, sizeof(path), "%s/dlfilters/%s", exec_path, file);
+ free(exec_path);
+ if (!access(path, R_OK))
+ file = path;
+out:
+ return strdup(file);
+}
+
#define CHECK_FLAG(x) BUILD_BUG_ON((u64)PERF_DLFILTER_FLAG_ ## x != (u64)PERF_IP_FLAG_ ## x)

static int dlfilter__init(struct dlfilter *d, const char *file)
@@ -155,7 +186,7 @@ static int dlfilter__init(struct dlfilter *d, const char *file)
CHECK_FLAG(VMEXIT);

memset(d, 0, sizeof(*d));
- d->file = strdup(file);
+ d->file = find_dlfilter(file);
if (!d->file)
return -1;
return 0;
@@ -333,3 +364,87 @@ int dlfilter__do_filter_event(struct dlfilter *d,

return ret;
}
+
+static bool get_filter_desc(const char *dirname, const char *name,
+ char **desc, char **long_desc)
+{
+ char path[PATH_MAX];
+ void *handle;
+ const char *(*desc_fn)(const char **long_description);
+
+ snprintf(path, sizeof(path), "%s/%s", dirname, name);
+ handle = dlopen(path, RTLD_NOW);
+ if (!handle || !(dlsym(handle, "filter_event") || dlsym(handle, "filter_event_early")))
+ return false;
+ desc_fn = dlsym(handle, "filter_description");
+ if (desc_fn) {
+ const char *dsc;
+ const char *long_dsc;
+
+ dsc = desc_fn(&long_dsc);
+ if (dsc)
+ *desc = strdup(dsc);
+ if (long_dsc)
+ *long_desc = strdup(long_dsc);
+ }
+ dlclose(handle);
+ return true;
+}
+
+static void list_filters(const char *dirname)
+{
+ struct dirent *entry;
+ DIR *dir;
+
+ dir = opendir(dirname);
+ if (!dir)
+ return;
+
+ while ((entry = readdir(dir)) != NULL)
+ {
+ size_t n = strlen(entry->d_name);
+ char *long_desc = NULL;
+ char *desc = NULL;
+
+ if (entry->d_type == DT_DIR || n < 4 ||
+ strcmp(".so", entry->d_name + n - 3))
+ continue;
+ if (!get_filter_desc(dirname, entry->d_name, &desc, &long_desc))
+ continue;
+ printf(" %-36s %s\n", entry->d_name, desc ? desc : "");
+ if (verbose) {
+ char *p = long_desc;
+ char *line;
+
+ while ((line = strsep(&p, "\n")) != NULL)
+ printf("%39s%s\n", "", line);
+ }
+ free(long_desc);
+ free(desc);
+ }
+
+ closedir(dir);
+}
+
+int list_available_dlfilters(const struct option *opt __maybe_unused,
+ const char *s __maybe_unused,
+ int unset __maybe_unused)
+{
+ char path[PATH_MAX];
+ char *exec_path;
+
+ printf("List of available dlfilters:\n");
+
+ list_filters(".");
+
+ exec_path = get_argv_exec_path();
+ if (!exec_path)
+ goto out;
+ snprintf(path, sizeof(path), "%s/dlfilters", exec_path);
+
+ list_filters(path);
+
+ free(exec_path);
+out:
+ exit(0);
+}
diff --git a/tools/perf/util/dlfilter.h b/tools/perf/util/dlfilter.h
index a994560e563d..a1ed38da3ce6 100644
--- a/tools/perf/util/dlfilter.h
+++ b/tools/perf/util/dlfilter.h
@@ -88,4 +88,6 @@ static inline int dlfilter__filter_event_early(struct dlfilter *d,
return dlfilter__do_filter_event(d, event, sample, evsel, machine, al, addr_al, true);
}

+int list_available_dlfilters(const struct option *opt, const char *s, int unset);
+
#endif
diff --git a/tools/perf/util/perf_dlfilter.h b/tools/perf/util/perf_dlfilter.h
index f7a847fdee59..31ad4c100181 100644
--- a/tools/perf/util/perf_dlfilter.h
+++ b/tools/perf/util/perf_dlfilter.h
@@ -126,4 +126,10 @@ int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ct
*/
int filter_event_early(void *data, const struct perf_dlfilter_sample *sample, void *ctx);

+/*
+ * If implemented, return a one-line description of the filter, and optionally
+ * a longer description.
+ */
+const char *filter_description(const char **long_description);
+
#endif
--
2.17.1