[PATCH 5/6] tools/sched_ext/include: Add libbpf version guard for assoc_struct_ops

[Tejun Heo]

Extract the inline bpf_program__assoc_struct_ops() call in SCX_OPS_LOAD()
into a __scx_ops_assoc_prog() helper and wrap it with a libbpf >= 1.7
version guard. bpf_program__assoc_struct_ops() was added in libbpf 1.7;
the guard provides a no-op fallback for older versions. Add the
<bpf/libbpf.h> include needed by the helper, and fix "assumming" typo in
a nearby comment.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 tools/sched_ext/include/scx/compat.h | 35 +++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/tools/sched_ext/include/scx/compat.h b/tools/sched_ext/include/scx/compat.h
index 9b6df13b187b..50297d4b9533 100644
--- a/tools/sched_ext/include/scx/compat.h
+++ b/tools/sched_ext/include/scx/compat.h
@@ -8,6 +8,7 @@
 #define __SCX_COMPAT_H
 
 #include <bpf/btf.h>
+#include <bpf/libbpf.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -182,6 +183,31 @@ static inline long scx_hotplug_seq(void)
 	__skel; 								\
 })
 
+/*
+ * Associate non-struct_ops BPF programs with the scheduler's struct_ops map so
+ * that scx_prog_sched() can determine which scheduler a BPF program belongs
+ * to. Requires libbpf >= 1.7.
+ */
+#if LIBBPF_MAJOR_VERSION > 1 ||							\
+	(LIBBPF_MAJOR_VERSION == 1 && LIBBPF_MINOR_VERSION >= 7)
+static inline void __scx_ops_assoc_prog(struct bpf_program *prog,
+					struct bpf_map *map,
+					const char *ops_name)
+{
+	s32 err = bpf_program__assoc_struct_ops(prog, map, NULL);
+	if (err)
+		fprintf(stderr,
+			"ERROR: Failed to associate %s with %s: %d\n",
+			bpf_program__name(prog), ops_name, err);
+}
+#else
+static inline void __scx_ops_assoc_prog(struct bpf_program *prog,
+					struct bpf_map *map,
+					const char *ops_name)
+{
+}
+#endif
+
 #define SCX_OPS_LOAD(__skel, __ops_name, __scx_name, __uei_name) ({		\
 	struct bpf_program *__prog;						\
 	UEI_SET_SIZE(__skel, __ops_name, __uei_name);				\
@@ -189,18 +215,15 @@ static inline long scx_hotplug_seq(void)
 	bpf_object__for_each_program(__prog, (__skel)->obj) {			\
 		if (bpf_program__type(__prog) == BPF_PROG_TYPE_STRUCT_OPS)	\
 			continue;						\
-		s32 err = bpf_program__assoc_struct_ops(__prog,			\
-					(__skel)->maps.__ops_name, NULL);	\
-		if (err)							\
-			fprintf(stderr, "ERROR: Failed to associate %s with %s: %d\n", \
-				bpf_program__name(__prog), #__ops_name, err);	\
+		__scx_ops_assoc_prog(__prog, (__skel)->maps.__ops_name,		\
+				     #__ops_name);				\
 	}									\
 })
 
 /*
  * New versions of bpftool now emit additional link placeholders for BPF maps,
  * and set up BPF skeleton in such a way that libbpf will auto-attach BPF maps
- * automatically, assumming libbpf is recent enough (v1.5+). Old libbpf will do
+ * automatically, assuming libbpf is recent enough (v1.5+). Old libbpf will do
  * nothing with those links and won't attempt to auto-attach maps.
  *
  * To maintain compatibility with older libbpf while avoiding trying to attach
-- 
2.53.0