[PATCH perf/core v13 06/15] perf buildid-cache: Scan and import user SDT events to probe cache

[Masami Hiramatsu]

From: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>

perf buildid-cache --add <binary> scans given binary and add
the SDT events to probe cache. "sdt_" prefix is appended for
all SDT providers to avoid event-name clash with other pre-defined
events. It is possible to use the cached SDT events as other cached
events, via perf probe --add "sdt_<provider>:<event>=<event>".

e.g.
  ----
  # perf buildid-cache --add /lib/libc-2.17.so
  # perf probe --cache --list | head -n 5
  /usr/lib/libc-2.17.so (a6fb821bdf53660eb2c29f778757aef294d3d392):
  sdt_libc:setjmp=setjmp
  sdt_libc:longjmp=longjmp
  sdt_libc:longjmp_target=longjmp_target
  sdt_libc:memory_heap_new=memory_heap_new
  # perf probe -x /usr/lib/libc-2.17.so \
    -a sdt_libc:memory_heap_new=memory_heap_new
  Added new event:
    sdt_libc:memory_heap_new (on memory_heap_new
   in /usr/lib/libc-2.17.so)

  You can now use it in all perf tools, such as:

          perf record -e sdt_libc:memory_heap_new -aR sleep 1

  # perf probe -l
    sdt_libc:memory_heap_new (on new_heap+183 in /usr/lib/libc-2.17.so)
  ----

Note that SDT event entries in probe-cache file is somewhat different
from normal cached events. Normal one starts with "#", but SDTs are
starting with "%".

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 Changes in v11:
  - Warn if SDT scanning/updating are failed.
 Changes in v10:
  - Update Documentation/perf-buildid-cache.txt too.
 Changes in v4:
  - Fix a bug to copy correct group name to entries.
  - Fix to consolidate same-name entries.
---
 tools/perf/Documentation/perf-buildid-cache.txt |    3 +
 tools/perf/util/build-id.c                      |   30 ++++++++++
 tools/perf/util/probe-file.c                    |   69 ++++++++++++++++++++++-
 tools/perf/util/probe-file.h                    |    2 +
 4 files changed, 101 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-buildid-cache.txt b/tools/perf/Documentation/perf-buildid-cache.txt
index dd07b55..058064d 100644
--- a/tools/perf/Documentation/perf-buildid-cache.txt
+++ b/tools/perf/Documentation/perf-buildid-cache.txt
@@ -15,6 +15,9 @@ DESCRIPTION
 This command manages the build-id cache. It can add, remove, update and purge
 files to/from the cache. In the future it should as well set upper limits for
 the space used by the cache, etc.
+This also scans the target binary for SDT (Statically Defined Tracing) and
+record it along with the buildid-cache, which will be used by perf-probe.
+For more details, see linkperf:perf-probe[1].
 
 OPTIONS
 -------
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 1c49620..e1a1640 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -17,6 +17,7 @@
 #include "tool.h"
 #include "header.h"
 #include "vdso.h"
+#include "probe-file.h"
 
 
 static bool no_buildid_cache;
@@ -532,6 +533,30 @@ int build_id_cache__list_build_ids(const char *pathname,
 	return ret;
 }
 
+#ifdef HAVE_LIBELF_SUPPORT
+static int build_id_cache__add_sdt_cache(const char *sbuild_id,
+					  const char *realname)
+{
+	struct probe_cache *cache;
+	int ret;
+
+	cache = probe_cache__new(sbuild_id);
+	if (!cache)
+		return -1;
+
+	ret = probe_cache__scan_sdt(cache, realname);
+	if (ret >= 0) {
+		pr_debug("Found %d SDTs in %s\n", ret, realname);
+		if (probe_cache__commit(cache) < 0)
+			ret = -1;
+	}
+	probe_cache__delete(cache);
+	return ret;
+}
+#else
+#define build_id_cache__add_sdt_cache(sbuild_id, realname) (0)
+#endif
+
 int build_id_cache__add_s(const char *sbuild_id, const char *name,
 			  bool is_kallsyms, bool is_vdso)
 {
@@ -589,6 +614,11 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
 
 	if (symlink(tmp, linkname) == 0)
 		err = 0;
+
+	/* Update SDT cache : error is just warned */
+	if (build_id_cache__add_sdt_cache(sbuild_id, realname) < 0)
+		pr_debug("Failed to update/scan SDT cache for %s\n", realname);
+
 out_free:
 	if (!is_kallsyms)
 		free(realname);
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 6cb6ec0..5b563b2 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -434,12 +434,15 @@ static int probe_cache__load(struct probe_cache *pcache)
 		p = strchr(buf, '\n');
 		if (p)
 			*p = '\0';
-		if (buf[0] == '#') {	/* #perf_probe_event */
+		/* #perf_probe_event or %sdt_event */
+		if (buf[0] == '#' || buf[0] == '%') {
 			entry = probe_cache_entry__new(NULL);
 			if (!entry) {
 				ret = -ENOMEM;
 				goto out;
 			}
+			if (buf[0] == '%')
+				entry->sdt = true;
 			entry->spev = strdup(buf + 1);
 			if (entry->spev)
 				ret = parse_perf_probe_command(buf + 1,
@@ -621,19 +624,79 @@ out_err:
 	return ret;
 }
 
+static unsigned long long sdt_note__get_addr(struct sdt_note *note)
+{
+	return note->bit32 ? (unsigned long long)note->addr.a32[0]
+		 : (unsigned long long)note->addr.a64[0];
+}
+
+int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
+{
+	struct probe_cache_entry *entry = NULL;
+	struct list_head sdtlist;
+	struct sdt_note *note;
+	char *buf;
+	char sdtgrp[64];
+	int ret;
+
+	INIT_LIST_HEAD(&sdtlist);
+	ret = get_sdt_note_list(&sdtlist, pathname);
+	if (ret < 0) {
+		pr_debug("Failed to get sdt note: %d\n", ret);
+		return ret;
+	}
+	list_for_each_entry(note, &sdtlist, note_list) {
+		ret = snprintf(sdtgrp, 64, "sdt_%s", note->provider);
+		if (ret < 0)
+			break;
+		/* Try to find same-name entry */
+		entry = probe_cache__find_by_name(pcache, sdtgrp, note->name);
+		if (!entry) {
+			entry = probe_cache_entry__new(NULL);
+			if (!entry) {
+				ret = -ENOMEM;
+				break;
+			}
+			entry->sdt = true;
+			ret = asprintf(&entry->spev, "%s:%s=%s", sdtgrp,
+					note->name, note->name);
+			if (ret < 0)
+				break;
+			entry->pev.event = strdup(note->name);
+			entry->pev.group = strdup(sdtgrp);
+			list_add_tail(&entry->node, &pcache->entries);
+		}
+		ret = asprintf(&buf, "p:%s/%s %s:0x%llx",
+				sdtgrp, note->name, pathname,
+				sdt_note__get_addr(note));
+		if (ret < 0)
+			break;
+		strlist__add(entry->tevlist, buf);
+		free(buf);
+		entry = NULL;
+	}
+	if (entry) {
+		list_del_init(&entry->node);
+		probe_cache_entry__delete(entry);
+	}
+	cleanup_sdt_note_list(&sdtlist);
+	return ret;
+}
+
 static int probe_cache_entry__write(struct probe_cache_entry *entry, int fd)
 {
 	struct str_node *snode;
 	struct stat st;
 	struct iovec iov[3];
+	const char *prefix = entry->sdt ? "%" : "#";
 	int ret;
 	/* Save stat for rollback */
 	ret = fstat(fd, &st);
 	if (ret < 0)
 		return ret;
 
-	pr_debug("Writing cache: #%s\n", entry->spev);
-	iov[0].iov_base = (void *)"#"; iov[0].iov_len = 1;
+	pr_debug("Writing cache: %s%s\n", prefix, entry->spev);
+	iov[0].iov_base = (void *)prefix; iov[0].iov_len = 1;
 	iov[1].iov_base = entry->spev; iov[1].iov_len = strlen(entry->spev);
 	iov[2].iov_base = (void *)"\n"; iov[2].iov_len = 1;
 	ret = writev(fd, iov, 3);
diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
index 0ed1fc5..ddf5ae2 100644
--- a/tools/perf/util/probe-file.h
+++ b/tools/perf/util/probe-file.h
@@ -8,6 +8,7 @@
 /* Cache of probe definitions */
 struct probe_cache_entry {
 	struct list_head	node;
+	bool			sdt;
 	struct perf_probe_event pev;
 	char			*spev;
 	struct strlist		*tevlist;
@@ -35,6 +36,7 @@ struct probe_cache *probe_cache__new(const char *target);
 int probe_cache__add_entry(struct probe_cache *pcache,
 			   struct perf_probe_event *pev,
 			   struct probe_trace_event *tevs, int ntevs);
+int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname);
 int probe_cache__commit(struct probe_cache *pcache);
 void probe_cache__purge(struct probe_cache *pcache);
 void probe_cache__delete(struct probe_cache *pcache);