bpf tools: Open eBPF object file and do basic validation

This patch defines basic interface of libbpf. 'struct bpf_object' will
be the handler of each object file. Its internal structure is hide to
user. eBPF object files are compiled by LLVM as ELF format. In this
patch, libelf is used to open those files, read EHDR and do basic
validation according to e_type and e_machine.

All elf related staffs are grouped together and reside in efile field of
'struct bpf_object'. bpf_object__elf_finish() is introduced to clear it.

After all eBPF programs in an object file are loaded, related ELF
information is useless. Close the object file and free those memory.

The zfree() and zclose() functions are introduced to ensure setting NULL
pointers and negative file descriptors after resources are released.

Signed-off-by: Wang Nan <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Cc: Brendan Gregg <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: David Ahern <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kaixu Xia <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 8 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 8d1eebafa958..ec3301ceeb85 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -8,6 +8,8 @@
 #ifndef __BPF_LIBBPF_H
 #define __BPF_LIBBPF_H
 
+#include <stdio.h>
+
 /*
  * In include/linux/compiler-gcc.h, __printf is defined. However
  * it should be better if libbpf.h doesn't depend on Linux header file.
@@ -20,4 +22,10 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 		      libbpf_print_fn_t info,
 		      libbpf_print_fn_t debug);
 
+/* Hide internal to user */
+struct bpf_object;
+
+struct bpf_object *bpf_object__open(const char *path);
+void bpf_object__close(struct bpf_object *object);
+
 #endif