bpf tools: Collect map definitions from 'maps' section

If maps are used by eBPF programs, corresponding object file(s) should
contain a section named 'map'. Which contains map definitions. This
patch copies the data of the whole section. Map data parsing should be
acted just before map loading.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-11-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 95c8d8e5c350..87f5054a9efb 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -81,6 +81,9 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 struct bpf_object {
         char license[64];
         u32 kern_version;
+        void *maps_buf;
+        size_t maps_buf_sz;
+
         /*
          * Information when doing elf related work. Only valid if fd
          * is valid.
@@ -250,6 +253,28 @@ bpf_object__init_kversion(struct bpf_object *obj,
         return 0;
 }
 
+static int
+bpf_object__init_maps(struct bpf_object *obj, void *data,
+                      size_t size)
+{
+        if (size == 0) {
+                pr_debug("%s doesn't need map definition\n",
+                         obj->path);
+                return 0;
+        }
+
+        obj->maps_buf = malloc(size);
+        if (!obj->maps_buf) {
+                pr_warning("malloc maps failed: %s\n", obj->path);
+                return -ENOMEM;
+        }
+
+        obj->maps_buf_sz = size;
+        memcpy(obj->maps_buf, data, size);
+        pr_debug("maps in %s: %ld bytes\n", obj->path, (long)size);
+        return 0;
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj)
 {
         Elf *elf = obj->efile.elf;
@@ -305,6 +330,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
                         err = bpf_object__init_kversion(obj,
                                                         data->d_buf,
                                                         data->d_size);
+                else if (strcmp(name, "maps") == 0)
+                        err = bpf_object__init_maps(obj, data->d_buf,
+                                                    data->d_size);
                 if (err)
                         goto out;
         }
@@ -382,5 +410,6 @@ void bpf_object__close(struct bpf_object *obj)
 
         bpf_object__elf_finish(obj);
 
+        zfree(&obj->maps_buf);
         free(obj);
 }