build libelf-free minimal libbpf for device

Add a device build of libbpf that includes only code with no libelf
dependency, and which can therefore be used from framework code.

bpf.c depends on a few symbols implemented in libbpf.c, so add a new
file with stub implementations for those symbols.

Also, the local linux/compiler.h and linux/types.h clobber the bionic
versions, with the result that __user, __force and __poll_t are
undefined. Since other bionic headers expect these to be defined, this
causes most of the files under src/ to fail to compile. Add a header
under android/ to ensure these are defined, and include it via
Android.bp to minimize Android-specific changes to upstream libbpf
code.

Test: m libbpf_minimal
Bug: 203823368
Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: I326b31cac62bbd58905d25d45483cf968c00b971

1 files changed, 27 insertions, 0 deletions

diff --git a/Android.bp b/Android.bp
index ec55963..809e349 100644
--- a/Android.bp
+++ b/Android.bp
@@ -64,3 +64,30 @@ cc_library_host_static {
     ],
     compile_multilib: "64",
 }
+
+cc_library {
+    name: "libbpf_minimal",
+    native_bridge_supported: true,
+    srcs: [
+        "android/bpf_stub.c",
+        "src/bpf.c",
+        "src/libbpf_errno.c",
+        "src/netlink.c",
+        "src/nlattr.c",
+        "src/ringbuf.c",
+    ],
+    local_include_dirs: [
+        "android",
+        "include"
+    ],
+    export_include_dirs: [
+        "include/uapi"
+    ],
+    generated_headers: ["libbpf_headers"],
+    export_generated_headers: ["libbpf_headers"],
+    cflags: [
+        "-include android/android.h",
+        "-Wno-pointer-arith",
+        "-Wno-unused-parameter",
+    ],
+}