tools lib bpf: Add bpf_prog_{attach,detach}

Commit d8c5b17f2bc0 ("samples: bpf: add userspace example for attaching
eBPF programs to cgroups") added these functions to samples/libbpf, but
during this merge all of the samples libbpf functionality is shifting to
tools/lib/bpf. Shift these functions there.

Committer notes:

Use bzero + attr.FIELD = value instead of 'attr = { .FIELD = value, just
like the other wrapper calls to sys_bpf with bpf_attr to make this build
in older toolchais, such as the ones in CentOS 5 and 6.

Signed-off-by: Joe Stringer <joe@ovn.org>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-au2zvtsh55vqeo3v3uw7jr4c@git.kernel.org
Link: https://github.com/joestringer/linux/commit/353e6f298c3d0a92fa8bfa61ff898c5050261a12.patch
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index d0afb26c2e0f..3ddb58a36d3c 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -167,3 +167,26 @@ int bpf_obj_get(const char *pathname)
 
         return sys_bpf(BPF_OBJ_GET, &attr, sizeof(attr));
 }
+
+int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type)
+{
+        union bpf_attr attr;
+
+        bzero(&attr, sizeof(attr));
+        attr.target_fd     = target_fd;
+        attr.attach_bpf_fd = prog_fd;
+        attr.attach_type   = type;
+
+        return sys_bpf(BPF_PROG_ATTACH, &attr, sizeof(attr));
+}
+
+int bpf_prog_detach(int target_fd, enum bpf_attach_type type)
+{
+        union bpf_attr attr;
+
+        bzero(&attr, sizeof(attr));
+        attr.target_fd   = target_fd;
+        attr.attach_type = type;
+
+        return sys_bpf(BPF_PROG_DETACH, &attr, sizeof(attr));
+}