[PATCH bpf-next v3 1/4] libbpf: Add bpf_program__add_flags() and bpf_program__clear_flags()

["Toke Høiland-Jørgensen" <toke@redhat.com>]

When changing BPF program flags, applications often need to just add or
remove a single flag, without touching the existing ones. When using the
bpf_program__set_flags() function, this requires reading the existing
flags and doing bitwise manipulations before resetting the result, which
is slightly awkward to do, and easy to forget.

Add two new convenience helpers, bpf_program__add_flags() and
bpf_program__clear_flags(), which wraps bpf_program__set_flags() in the
bitwise operations required to modify flags without clobbering the
existing ones.

Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
v3:
  - Proper API docs
  - Early return on load failure in selftest
  - Replace the two missing instances of bpf_program__set_flags() in selftests

 tools/lib/bpf/libbpf.c   | 10 ++++++++++
 tools/lib/bpf/libbpf.h   | 22 ++++++++++++++++++++++
 tools/lib/bpf/libbpf.map |  2 ++
 3 files changed, 34 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8da5181c8e8b..2c6ebce2b675 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9933,6 +9933,16 @@ int bpf_program__set_flags(struct bpf_program *prog, __u32 flags)
 	return 0;
 }
 
+int bpf_program__add_flags(struct bpf_program *prog, __u32 flags)
+{
+	return bpf_program__set_flags(prog, prog->prog_flags | flags);
+}
+
+int bpf_program__clear_flags(struct bpf_program *prog, __u32 flags)
+{
+	return bpf_program__set_flags(prog, prog->prog_flags & ~flags);
+}
+
 __u32 bpf_program__log_level(const struct bpf_program *prog)
 {
 	return prog->log_level;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index b965ad571540..48266e752223 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1011,6 +1011,28 @@ bpf_program__set_expected_attach_type(struct bpf_program *prog,
 LIBBPF_API __u32 bpf_program__flags(const struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_flags(struct bpf_program *prog, __u32 flags);
 
+/**
+ * @brief **bpf_program__add_flags()** adds one or more flags to the BPF
+ * program, preserving any existing flags.
+ *
+ * @param prog BPF program
+ * @param flags the flags to add
+ *
+ * @return 0, on success; negative error code, otherwise
+ */
+LIBBPF_API int bpf_program__add_flags(struct bpf_program *prog, __u32 flags);
+
+/**
+ * @brief **bpf_program__clear_flags()** clears one or more flags from the BPF
+ * program, preserving any other flags not explicitly cleared.
+ *
+ * @param prog BPF program
+ * @param flags the flags to clear
+ *
+ * @return 0, on success; negative error code, otherwise
+ */
+LIBBPF_API int bpf_program__clear_flags(struct bpf_program *prog, __u32 flags);
+
 /* Per-program log level and log buffer getters/setters.
  * See bpf_object_open_opts comments regarding log_level and log_buf
  * interactions.
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 08ab2ea881fb..a811a1b3a085 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -458,7 +458,9 @@ LIBBPF_1.7.0 {
 
 LIBBPF_1.8.0 {
 	global:
+		bpf_program__add_flags;
 		bpf_program__attach_tracing_multi;
+		bpf_program__clear_flags;
 		bpf_program__clone;
 		btf__find_by_name_kind_own;
 		btf__new_empty_opts;
-- 
2.55.0