[RFC PATCH 09/22] perf bpf: collect map definitions.

[Wang Nan]

If maps are used by eBPF programs, corresponding object file(s) should
contain a section named 'map'. Which contains map definitions, one for
each map to describe its format. 'struct perf_bpf_map_def' is
introduced as part of protocol between perf and eBPF programs. All map
definitions are copied to obj->maps.

bpf.h is introduced for common bpf operations.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/perf/util/bpf-loader.c | 31 +++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 296fb06..bf3b793 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -65,6 +65,8 @@ static void bpf_obj_close(struct bpf_obj *obj)
 
 	if (obj->path)
 		free(obj->path);
+	if (obj->maps)
+		free(obj->maps);
 	free(obj);
 }
 
@@ -183,6 +185,32 @@ static int bpf_obj_kver_init(struct bpf_obj *obj,
 	return 0;
 }
 
+static int bpf_obj_maps_init(struct bpf_obj *obj, void *data,
+			     size_t size)
+{
+	size_t map_def_sz = sizeof(struct bpf_map_def);
+	int nr_maps = size / map_def_sz;
+
+	if (nr_maps == 0) {
+		pr_debug("bpf: %s doesn't need map definition\n",
+			 obj->path);
+		return 0;
+	}
+
+	obj->maps = malloc(nr_maps * map_def_sz);
+	if (!obj->maps) {
+		pr_err("bpf: malloc maps failed: %s\n", obj->path);
+		return -ENOMEM;
+	}
+
+	obj->nr_maps = nr_maps;
+	memcpy(obj->maps, data, nr_maps * map_def_sz);
+	pr_debug("bpf: %d map%s in %s\n", nr_maps,
+			nr_maps > 1 ? "s" : "",
+			obj->path);
+	return 0;
+}
+
 static int bpf_obj_elf_collect(struct bpf_obj *obj)
 {
 	Elf *elf = obj->elf.elf;
@@ -237,6 +265,9 @@ static int bpf_obj_elf_collect(struct bpf_obj *obj)
 		else if (strcmp(name, "version") == 0)
 			err = bpf_obj_kver_init(obj, data->d_buf,
 						data->d_size);
+		else if (strcmp(name, "maps") == 0)
+			err = bpf_obj_maps_init(obj, data->d_buf,
+						data->d_size);
 		if (err)
 			goto out;
 	}
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index e1d5c42..6c5c8d6 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -14,6 +14,7 @@
 #include "perf.h"
 #include "symbol.h"
 #include "probe-event.h"
+#include "bpf.h"
 
 int bpf__load(const char *path);
 int bpf__run(void);
@@ -25,6 +26,8 @@ struct bpf_obj {
 	bool needs_swap;
 	char license[64];
 	u32 kern_version;
+	struct bpf_map_def *maps;
+	size_t nr_maps;
 
 	/*
 	 * Information when doing elf related work. Only valid if fd
-- 
1.8.3.4

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