[RFC PATCH v3 25/37] bpf tools: Introduce accessors for struct bpf_program

Wang Nan
2015-05-17T11:01:34Z

This patch introduces accessors for user of libbpf to retrive section
name and fd of a opened/loaded eBPF program. 'struct bpf_prog_handler'
is used for that purpose. Accessors of programs section name and file
descriptor are provided. Set/get private data are also impelmented.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
tools/lib/bpf/libbpf.c | 137 +++++++++++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 25 +++++++++
2 files changed, 162 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e8ef78e..d770adc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -79,6 +79,20 @@ void libbpf_set_print(int (*warn)(const char *format, ...),
# define LIBBPF_ELF_C_READ_MMAP ELF_C_READ
#endif

+#ifndef container_of
+# define container_of(ptr, type, member) ({ \
+ const typeof( ((type *)0)->member ) *__mptr = (ptr); \
+ (type *)( (char *)__mptr - offsetof(type,member) );})
+#endif
+
+/* Accessing of project */
+struct bpf_prog_handler {
+ struct bpf_object *obj;
+
+ void *priv;
+ bpf_prog_clear_priv_t clear_priv;
+};
+
/*
* bpf_prog should be a better name but it has been used in
* linux/filter.h.
@@ -97,6 +111,7 @@ struct bpf_program {
int nr_reloc;

int fd;
+ struct bpf_prog_handler handler;
};

struct bpf_object {
@@ -146,6 +161,12 @@ static void bpf_clear_program(struct bpf_program *prog)
if (!prog)
return;

+ if (prog->handler.clear_priv)
+ prog->handler.clear_priv(&prog->handler, prog->handler.priv);
+
+ prog->handler.priv = NULL;
+ prog->handler.clear_priv = NULL;
+
bpf_unload_program(prog);

if (prog->section_name) {
@@ -217,6 +238,7 @@ bpf_program_alloc(struct bpf_object *obj, void *data, size_t size,
prog->insns_cnt * sizeof(struct bpf_insn));
prog->idx = idx;
prog->fd = -1;
+ prog->handler.obj = obj;

return prog;
out:
@@ -941,3 +963,118 @@ void bpf_close_object(struct bpf_object *obj)
}
free(obj);
}
+
+static inline struct bpf_program *
+handler_to_prog(struct bpf_prog_handler *handler)
+{
+ struct bpf_program *prog;
+ struct bpf_object *obj;
+ size_t idx;
+
+ if (!handler)
+ goto out_warn;
+
+ obj = handler->obj;
+ prog = container_of(handler, struct bpf_program, handler);
+ idx = prog - obj->programs;
+ if (idx >= obj->nr_programs)
+ goto out_warn;
+ return &obj->programs[idx];
+
+out_warn:
+ pr_warning("invalid handler %p\n", handler);
+ return NULL;
+}
+
+struct bpf_prog_handler *
+bpf_next_prog(struct bpf_object *obj, struct bpf_prog_handler *handler)
+{
+ struct bpf_program *prog;
+ size_t idx;
+
+ if (!obj->programs)
+ return NULL;
+ /* First handler */
+ if (handler == NULL)
+ return (&obj->programs[0].handler);
+
+ if (handler->obj != obj) {
+ pr_warning("error: program handler doesn't "
+ "match object\n");
+ return NULL;
+ }
+
+ prog = handler_to_prog(handler);
+ if (!prog)
+ return NULL;
+
+ idx = (prog - obj->programs) + 1;
+ if (idx >= obj->nr_programs)
+ return NULL;
+ return &obj->programs[idx].handler;
+}
+
+int bpf_prog_set_private(struct bpf_prog_handler *handler, void *priv,
+ bpf_prog_clear_priv_t clear_priv)
+{
+ struct bpf_program *prog;
+
+ prog = handler_to_prog(handler);
+ if (!prog)
+ return -EINVAL;
+
+ if (prog->handler.priv && prog->handler.clear_priv)
+ prog->handler.clear_priv(&prog->handler, prog->handler.priv);
+
+ prog->handler.priv = priv;
+ prog->handler.clear_priv = clear_priv;
+ return 0;
+}
+
+int bpf_prog_get_private(struct bpf_prog_handler *handler, void **ppriv)
+{
+ struct bpf_program *prog;
+
+ prog = handler_to_prog(handler);
+ if (!prog || !ppriv)
+ return -EINVAL;
+
+ *ppriv = prog->handler.priv;
+ return 0;
+}
+
+int bpf_prog_get_title(struct bpf_prog_handler *handler,
+ const char **ptitle, bool dup)
+{
+ struct bpf_program *prog;
+ const char *title;
+
+ prog = handler_to_prog(handler);
+ if (!prog || !ptitle)
+ return -EINVAL;
+
+ title = prog->section_name;
+ if (dup) {
+ title = strdup(title);
+ if (!title) {
+ pr_warning("failed to strdup program title\n");
+ *ptitle = NULL;
+ return -ENOMEM;
+ }
+ }
+
+ *ptitle = title;
+ return 0;
+}
+
+int bpf_prog_get_fd(struct bpf_prog_handler *handler, int *pfd)
+{
+ struct bpf_program *prog;
+
+ prog = handler_to_prog(handler);
+ if (!prog || !pfd)
+ return -EINVAL;
+
+ *pfd = prog->fd;
+ return 0;
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index c0b290d..b451d1a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -10,6 +10,7 @@
#define __BPF_LIBBPF_H

#include <stdio.h>
+#include <stdbool.h>

void libbpf_set_print(int (*warn)(const char *format, ...),
int (*info)(const char *format, ...),
@@ -25,6 +26,30 @@ void bpf_close_object(struct bpf_object *object);
int bpf_load_object(struct bpf_object *obj);
int bpf_unload_object(struct bpf_object *obj);

+/* Accessors of bpf_program. */
+struct bpf_prog_handler;
+struct bpf_prog_handler *bpf_next_prog(struct bpf_object *obj,
+ struct bpf_prog_handler *handler);
+
+#define bpf_obj_for_each_prog(obj, pos) \
+ for ((pos) = bpf_next_prog((obj), NULL); \
+ (pos) != NULL; \
+ (pos) = bpf_next_prog((obj), (pos)))
+
+typedef void (*bpf_prog_clear_priv_t)(struct bpf_prog_handler *,
+ void *);
+
+int bpf_prog_set_private(struct bpf_prog_handler *handler, void *priv,
+ bpf_prog_clear_priv_t clear_priv);
+
+int bpf_prog_get_private(struct bpf_prog_handler *handler,
+ void **ppriv);
+
+int bpf_prog_get_title(struct bpf_prog_handler *handler,
+ const char **ptitle, bool dup);
+
+int bpf_prog_get_fd(struct bpf_prog_handler *handler, int *pfd);
+
/*
* packed attribute is unnecessary for 'bpf_map_def'.
*/
--
1.8.3.4