[tip:perf/core] perf probe: Add supported for type casting by the running kernel

[tip-bot for Masami Hiramatsu <tipbot@zytor.com>]

Commit-ID:  180b20616ce57e93eb692170c793be94c456b1e2
Gitweb:     http://git.kernel.org/tip/180b20616ce57e93eb692170c793be94c456b1e2
Author:     Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Thu, 18 Aug 2016 17:58:31 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 23 Aug 2016 17:03:31 -0300

perf probe: Add supported for type casting by the running kernel

Add a checking routine what types are supported by the running kernel by
finding the pattern in <debugfs>/tracing/README.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Naohiro Aota <naohiro.aota@hgst.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/147151071172.12957.3340095690753291085.stgit@devbox
[ 'enum probe_type' has no negative entries, so ends up as 'unsigned', remove '< 0'
   test to fix the build on at least centos:5, debian:7 & ubuntu:12.04.5 ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-file.c   | 57 ++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/probe-file.h   | 10 ++++++++
 tools/perf/util/probe-finder.c |  1 +
 3 files changed, 68 insertions(+)

diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 9c3b9ed..697ef66 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -877,3 +877,60 @@ int probe_cache__show_all_caches(struct strfilter *filter)
 
 	return 0;
 }
+
+static struct {
+	const char *pattern;
+	bool	avail;
+	bool	checked;
+} probe_type_table[] = {
+#define DEFINE_TYPE(idx, pat, def_avail)	\
+	[idx] = {.pattern = pat, .avail = (def_avail)}
+	DEFINE_TYPE(PROBE_TYPE_U, "* u8/16/32/64,*", true),
+	DEFINE_TYPE(PROBE_TYPE_S, "* s8/16/32/64,*", true),
+	DEFINE_TYPE(PROBE_TYPE_X, "* x8/16/32/64,*", false),
+	DEFINE_TYPE(PROBE_TYPE_STRING, "* string,*", true),
+	DEFINE_TYPE(PROBE_TYPE_BITFIELD,
+		    "* b<bit-width>@<bit-offset>/<container-size>", true),
+};
+
+bool probe_type_is_available(enum probe_type type)
+{
+	FILE *fp;
+	char *buf = NULL;
+	size_t len = 0;
+	bool target_line = false;
+	bool ret = probe_type_table[type].avail;
+
+	if (type >= PROBE_TYPE_END)
+		return false;
+	/* We don't have to check the type which supported by default */
+	if (ret || probe_type_table[type].checked)
+		return ret;
+
+	if (asprintf(&buf, "%s/README", tracing_path) < 0)
+		return ret;
+
+	fp = fopen(buf, "r");
+	if (!fp)
+		goto end;
+
+	zfree(&buf);
+	while (getline(&buf, &len, fp) > 0 && !ret) {
+		if (!target_line) {
+			target_line = !!strstr(buf, " type: ");
+			if (!target_line)
+				continue;
+		} else if (strstr(buf, "\t          ") != buf)
+			break;
+		ret = strglobmatch(buf, probe_type_table[type].pattern);
+	}
+	/* Cache the result */
+	probe_type_table[type].checked = true;
+	probe_type_table[type].avail = ret;
+
+	fclose(fp);
+end:
+	free(buf);
+
+	return ret;
+}
diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
index 9577b5c..eba44c3 100644
--- a/tools/perf/util/probe-file.h
+++ b/tools/perf/util/probe-file.h
@@ -19,6 +19,15 @@ struct probe_cache {
 	struct list_head entries;
 };
 
+enum probe_type {
+	PROBE_TYPE_U = 0,
+	PROBE_TYPE_S,
+	PROBE_TYPE_X,
+	PROBE_TYPE_STRING,
+	PROBE_TYPE_BITFIELD,
+	PROBE_TYPE_END,
+};
+
 #define PF_FL_UPROBE	1
 #define PF_FL_RW	2
 #define for_each_probe_cache_entry(entry, pcache) \
@@ -54,6 +63,7 @@ struct probe_cache_entry *probe_cache__find(struct probe_cache *pcache,
 struct probe_cache_entry *probe_cache__find_by_name(struct probe_cache *pcache,
 					const char *group, const char *event);
 int probe_cache__show_all_caches(struct strfilter *filter);
+bool probe_type_is_available(enum probe_type type);
 #else	/* ! HAVE_LIBELF_SUPPORT */
 static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused)
 {
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5c290c6..24dbe23 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -39,6 +39,7 @@
 #include "util.h"
 #include "symbol.h"
 #include "probe-finder.h"
+#include "probe-file.h"
 
 /* Kprobe tracer basic type is up to u64 */
 #define MAX_BASIC_TYPE_BITS	64