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

[Wang Nan]

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@xxxxxxxxxx>
---
 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

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