libbpf: support building bpftool

Make changes necessary for bpftool to successfully build against libbpf
- Grant visibility
- Include hashmap.h and nlattr.h in libbpf_headers
- Remove #if 0 block around references to __NR_bpf in
  skel_internal.h. This is no longer necessary now that we've added
  __NR_bpf to our glibc headers, and the affected functions are needed
  for building bpftool.

Test: m bpftool
Test: m libbpf pahole libbpf_bcc
Bug: 203823368
Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: If39f0989e162e0a7eac65e339b40ebda25211e2d

2 files changed, 3 insertions, 4 deletions

diff --git a/Android.bp b/Android.bp
index 75ca2ba..8ef21c7 100644
--- a/Android.bp
+++ b/Android.bp
@@ -45,10 +45,12 @@ genrule {
         "bpf/bpf_helpers.h",
         "bpf/bpf_tracing.h",
         "bpf/btf.h",
+        "bpf/hashmap.h",
         "bpf/libbpf_common.h",
         "bpf/libbpf.h",
         "bpf/libbpf_legacy.h",
         "bpf/libbpf_version.h",
+        "bpf/nlattr.h",
         "bpf/skel_internal.h",
         "bpf/xsk.h",
     ],
@@ -82,6 +84,7 @@ cc_library_static {
         "libz",
     ],
     visibility: [
+        "//external/bpftool",
         "//external/dwarves",
         "//external/stg",
     ],
diff --git a/src/skel_internal.h b/src/skel_internal.h
index 2761970..dcd3336 100644
--- a/src/skel_internal.h
+++ b/src/skel_internal.h
@@ -57,9 +57,6 @@ struct bpf_load_and_run_opts {
 	const char *errstr;
 };
 
-// ANDROID: Since the glibc stub we have does not know about __NR_bpf, this
-// fails to compile. For now, just do not provide this functionality.
-#if 0
 static inline int skel_sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
 			  unsigned int size)
 {
@@ -199,6 +196,5 @@ out:
 		close(prog_fd);
 	return err;
 }
-#endif
 
 #endif