[RFC PATCH v4 22/29] bpf tools: Link all bpf objects onto a list

[Wang Nan]

To prevent caller from creating additional structures to hold
pointers of 'struct bpf_object', this patch link all such
structures onto a list (hidden to user). bpf_object__for_each() is
introduced to allow users iterate over each objects.
bpf_object__for_each() is safe even user close the object during
iteration.

Signed-off-by: Wang Nan <wangn...@huawei.com>
---
 tools/lib/bpf/libbpf.c | 32 ++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h |  7 +++++++
 2 files changed, 39 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e5084fe..e2b41b7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -17,6 +17,7 @@
 #include <asm/unistd.h>
 #include <linux/kernel.h>
 #include <linux/bpf.h>
+#include <linux/list.h>
 #include <libelf.h>
 #include <gelf.h>
 
@@ -107,6 +108,8 @@ struct bpf_program {
        bpf_program_clear_priv_t clear_priv;
 };
 
+static LIST_HEAD(bpf_objects_list);
+
 struct bpf_object {
        char license[64];
        u32 kern_version;
@@ -132,6 +135,12 @@ struct bpf_object {
                } *reloc;
                int nr_reloc;
        } efile;
+       /*
+        * All loaded bpf_object is linked in a list, which is
+        * hidden to caller. bpf_objects__<func> handlers deal with
+        * all objects.
+        */
+       struct list_head list;
        char path[];
 };
 #define obj_elf_valid(o)       ((o)->efile.fd >= 0)
@@ -236,6 +245,9 @@ static struct bpf_object *bpf_object__new(const char *path)
 
        strcpy(obj->path, path);
        obj->efile.fd = -1;
+
+       INIT_LIST_HEAD(&obj->list);
+       list_add(&obj->list, &bpf_objects_list);
        return obj;
 }
 
@@ -853,6 +865,7 @@ void bpf_object__close(struct bpf_object *obj)
                bpf_program__clear(&obj->programs[i]);
        zfree(&obj->programs);
 
+       list_del(&obj->list);
        free(obj);
 }
 
@@ -865,6 +878,25 @@ int bpf_object__get_prog_cnt(struct bpf_object *obj, 
size_t *pcnt)
        return 0;
 }
 
+struct bpf_object *
+bpf_object__next(struct bpf_object *prev)
+{
+       struct bpf_object *next;
+
+       if (!prev)
+               next = list_first_entry(&bpf_objects_list,
+                                       struct bpf_object,
+                                       list);
+       else
+               next = list_next_entry(prev, list);
+
+       /* Empty list is noticed here so don't need checking on entry. */
+       if (&next->list == &bpf_objects_list)
+               return NULL;
+
+       return next;
+}
+
 struct bpf_program *
 bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
 {
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 84c83d4..fa271ec 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -28,6 +28,13 @@ int bpf_object__unload(struct bpf_object *obj);
 /* Accessors of bpf_object */
 int bpf_object__get_prog_cnt(struct bpf_object *obj, size_t *pcnt);
 
+struct bpf_object *bpf_object__next(struct bpf_object *prev);
+#define bpf_object__for_each(pos, tmp)                 \
+       for ((pos) = bpf_object__next(NULL),            \
+               (tmp) = bpf_object__next(pos);          \
+            (pos) != NULL;                             \
+            (pos) = (tmp), (tmp) = bpf_object__next(tmp))
+
 /* Accessors of bpf_program. */
 struct bpf_program;
 struct bpf_program *bpf_program__next(struct bpf_program *prog,
-- 
1.8.3.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/