[RFC 3/4] perf tool: Introduce PERF_RECORD_KMOD_SEC_MAP

[Ravi Bangoria]

Introduce, perf tool only, synthetic event type PERF_RECORD_KMOD_SEC_MAP.
Also add stub code for it. This event will be used to save/restore kernel
module section maps to/from perf.data file. This is needed because kernel
module elfs does not contain program header table and thus there is no
easy way to find out how kernel would have loaded module sections in the
memory.

Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
---
 tools/lib/perf/Documentation/libperf.txt |  1 +
 tools/lib/perf/include/perf/event.h      | 25 ++++++++++++++++++++++++
 tools/perf/util/event.c                  |  1 +
 tools/perf/util/session.c                | 12 ++++++++++++
 tools/perf/util/tool.h                   |  3 ++-
 5 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
index a8f1a237931b..b62730b84cc5 100644
--- a/tools/lib/perf/Documentation/libperf.txt
+++ b/tools/lib/perf/Documentation/libperf.txt
@@ -211,6 +211,7 @@ SYNOPSIS
   struct perf_record_time_conv;
   struct perf_record_header_feature;
   struct perf_record_compressed;
+  struct perf_record_kmod_sec_maps;
 --
 
 DESCRIPTION
diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index ad47d7b31046..404b23b6902b 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -438,6 +438,29 @@ struct perf_record_compressed {
 	char			 data[];
 };
 
+/* Kernel module elf section maps */
+struct perf_record_kmod_sec_map {
+	struct perf_event_header header;
+	/* Machine id. Same as synthesized PERF_RECORD_MMAP */
+	__u32			 pid;
+	/* Section start ip address */
+	__u64			 start;
+	/* Section length */
+	__u64			 len;
+	/* Section page offset in kernel module elf file */
+	__u64			 pgoff;
+	/* Section name length, including '\0' */
+	__u16			 sec_name_len;
+	/* Kernel module filename(path) length, including '\0' */
+	__u16			 filename_len;
+	/*
+	 * Section name and filename stored as: "sec_name\0filename\0". i.e:
+	 * data[0]: Section name
+	 * data[sec_name_len + 1]: File name
+	 */
+	char			 data[];
+};
+
 enum perf_user_event_type { /* above any possible kernel type */
 	PERF_RECORD_USER_TYPE_START		= 64,
 	PERF_RECORD_HEADER_ATTR			= 64,
@@ -459,6 +482,7 @@ enum perf_user_event_type { /* above any possible kernel type */
 	PERF_RECORD_HEADER_FEATURE		= 80,
 	PERF_RECORD_COMPRESSED			= 81,
 	PERF_RECORD_FINISHED_INIT		= 82,
+	PERF_RECORD_KMOD_SEC_MAP		= 83,
 	PERF_RECORD_HEADER_MAX
 };
 
@@ -499,6 +523,7 @@ union perf_event {
 	struct perf_record_time_conv		time_conv;
 	struct perf_record_header_feature	feat;
 	struct perf_record_compressed		pack;
+	struct perf_record_kmod_sec_map		kmod_sec_map;
 };
 
 #endif /* __LIBPERF_EVENT_H */
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 1fa14598b916..1b03061440bc 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -77,6 +77,7 @@ static const char *perf_event__names[] = {
 	[PERF_RECORD_HEADER_FEATURE]		= "FEATURE",
 	[PERF_RECORD_COMPRESSED]		= "COMPRESSED",
 	[PERF_RECORD_FINISHED_INIT]		= "FINISHED_INIT",
+	[PERF_RECORD_KMOD_SEC_MAP]		= "KMOD_SEC_MAP",
 };
 
 const char *perf_event__name(unsigned int id)
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 7c021c6cedb9..4f5165cd58de 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -563,6 +563,8 @@ void perf_tool__fill_defaults(struct perf_tool *tool)
 		tool->compressed = perf_session__process_compressed_event;
 	if (tool->finished_init == NULL)
 		tool->finished_init = process_event_op2_stub;
+	if (tool->kmod_sec_map == NULL)
+		tool->kmod_sec_map = process_event_stub;
 }
 
 static void swap_sample_id_all(union perf_event *event, void *data)
@@ -997,6 +999,12 @@ static void perf_event__time_conv_swap(union perf_event *event,
 	}
 }
 
+static void perf_event_kmod_sec_map_swap(union perf_event *event __maybe_unused,
+					  bool sample_id_all __maybe_unused)
+{
+	/* FIXME */
+}
+
 typedef void (*perf_event__swap_op)(union perf_event *event,
 				    bool sample_id_all);
 
@@ -1035,6 +1043,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
 	[PERF_RECORD_STAT_ROUND]	  = perf_event__stat_round_swap,
 	[PERF_RECORD_EVENT_UPDATE]	  = perf_event__event_update_swap,
 	[PERF_RECORD_TIME_CONV]		  = perf_event__time_conv_swap,
+	[PERF_RECORD_KMOD_SEC_MAP]	  = perf_event_kmod_sec_map_swap,
 	[PERF_RECORD_HEADER_MAX]	  = NULL,
 };
 
@@ -1727,6 +1736,9 @@ static s64 perf_session__process_user_event(struct perf_session *session,
 		return err;
 	case PERF_RECORD_FINISHED_INIT:
 		return tool->finished_init(session, event);
+	case PERF_RECORD_KMOD_SEC_MAP:
+		/* Currently PERF_RECORD_KMOD_SEC_MAP is supported only for host */
+		return tool->kmod_sec_map(tool, event, &sample, &session->machines.host);
 	default:
 		return -EINVAL;
 	}
diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h
index c957fb849ac6..8ea7fb85c196 100644
--- a/tools/perf/util/tool.h
+++ b/tools/perf/util/tool.h
@@ -60,7 +60,8 @@ struct perf_tool {
 			unthrottle,
 			ksymbol,
 			bpf,
-			text_poke;
+			text_poke,
+			kmod_sec_map;
 
 	event_attr_op	attr;
 	event_attr_op	event_update;
-- 
2.39.0