[RFC PATCH v4 16/29] bpf tools: Create eBPF maps defined in an object file

[Wang Nan]

This patch creates maps based on 'map' section in object file using
bpf_create_map(), and store the fds into an array in
'struct bpf_object'. Since the byte order of the object may differ
from the host, swap map definition before processing.

This is the first patch in 'loading' phase. Previous patches parse ELF
object file and create needed data structure, but doesn't play with
kernel. They belong to 'opening' phase.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/lib/bpf/libbpf.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h |  4 +++
 2 files changed, 88 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3a7ff7d..fe4d282 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -21,6 +21,7 @@
 #include <gelf.h>
 
 #include "libbpf.h"
+#include "bpf.h"
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
@@ -108,6 +109,7 @@ struct bpf_object {
 
 	struct bpf_program *programs;
 	size_t nr_programs;
+	int *maps_fds;
 
 	/*
 	 * Information when doing elf related work. Only valid if fd
@@ -534,6 +536,57 @@ bpf_program__collect_reloc(struct bpf_program *prog,
 	return 0;
 }
 
+static int
+bpf_object__create_maps(struct bpf_object *obj)
+{
+	unsigned int i;
+	size_t nr_maps;
+	int *pfd;
+
+	nr_maps = obj->maps_buf_sz / sizeof(struct bpf_map_def);
+	if (!obj->maps_buf || !nr_maps) {
+		pr_debug("don't need create maps for %s\n",
+			 obj->path);
+		return 0;
+	}
+
+	obj->maps_fds = malloc(sizeof(int) * nr_maps);
+	if (!obj->maps_fds) {
+		pr_warning("realloc perf_bpf_maps_fds failed\n");
+		return -ENOMEM;
+	}
+
+	/* fill all fd with -1 */
+	memset(obj->maps_fds, 0xff, sizeof(int) * nr_maps);
+	
+	pfd = obj->maps_fds;
+	for (i = 0; i < nr_maps; i++) {
+		struct bpf_map_def def;
+
+		def = *(struct bpf_map_def *)(obj->maps_buf +
+				i * sizeof(struct bpf_map_def));
+
+		*pfd = bpf_create_map(def.type,
+				      def.key_size,
+				      def.value_size,
+				      def.max_entries);
+		if (*pfd < 0) {
+			size_t j;
+			int err = *pfd;
+
+			pr_warning("failed to create map: %s\n",
+				   strerror(errno));
+			for (j = 0; j < i; j++)
+				zclose(obj->maps_fds[j]);
+			zfree(&obj->maps_fds);
+			return err;
+		}
+		pr_debug("create map: fd=%d\n", *pfd);
+		pfd ++;
+	}
+	return 0;
+}
+
 static int bpf_object__collect_reloc(struct bpf_object *obj)
 {
 	int i, err;
@@ -619,6 +672,36 @@ out:
 	return NULL;
 }
 
+int bpf_object__unload(struct bpf_object *obj)
+{
+	size_t i;
+	size_t sz = sizeof(struct bpf_map_def);
+
+	if (!obj)
+		return -EINVAL;
+
+	for (i = 0; i < obj->maps_buf_sz; i += sz)
+		zclose(obj->maps_fds[i]);
+	zfree(&obj->maps_fds);
+
+	return 0;
+}
+
+int bpf_object__load(struct bpf_object *obj)
+{
+	if (!obj)
+		return -EINVAL;
+
+	if (bpf_object__create_maps(obj))
+		goto out;
+
+	return 0;
+out:
+	bpf_object__unload(obj);
+	pr_warning("failed to load object '%s'\n", obj->path);
+	return -EINVAL;
+}
+
 void bpf_object__close(struct bpf_object *obj)
 {
 	size_t i;
@@ -627,6 +710,7 @@ void bpf_object__close(struct bpf_object *obj)
 		return;
 
 	bpf_object__elf_finish(obj);
+	bpf_object__unload(obj);
 
 	zfree(&obj->maps_buf);
 
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 73f796f..716e6df 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -20,6 +20,10 @@ struct bpf_object;
 struct bpf_object *bpf_object__open(const char *path);
 void bpf_object__close(struct bpf_object *object);
 
+/* Load/unload object into/from kernel */
+int bpf_object__load(struct bpf_object *obj);
+int bpf_object__unload(struct bpf_object *obj);
+
 /*
  * We don't need __attribute__((packed)) now since it is
  * unnecessary for 'bpf_map_def' because they are all aligned.
-- 
1.8.3.4

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