[PATCH bpf-next v4 5/7] libbpf: Version bpf_program__set_autoattach() ABI change

[Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>]

bpf_program__set_autoattach()'s return type changed from void to int to
let callers observe the new -EINVAL rejection for MANUAL-strategy
programs, but the symbol stayed under its original LIBBPF_1.0.0 node in
libbpf.map. Binaries already linked against the old void-returning ABI
recorded a request for exactly that symbol@version pair at link time;
without a version bump they would silently start hitting the new
rejection behavior underneath them after a libbpf upgrade.

Split the symbol via ELF symbol versioning:

  - bpf_program__set_autoattach_deprecated() keeps the original
    unconditional behavior, bound via COMPAT_VERSION() to the existing
    LIBBPF_1.0.0 node.
  - bpf_program__set_autoattach_v1_8_0() carries the new MANUAL-rejecting
    behavior, bound via DEFAULT_VERSION() to the new LIBBPF_1.8.0 node.

Old binaries keep resolving bpf_program__set_autoattach() to the old
behavior at runtime; anything linked against the current headers/map
gets the new int-returning, MANUAL-rejecting behavior. Also adds the
missing __LIBBPF_MARK_DEPRECATED_1_8 gate to libbpf_common.h (only the
1.0 gate existed) so LIBBPF_DEPRECATED_SINCE(1, 8, ...) can mark the
deprecated variant.

Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
---
 tools/lib/bpf/libbpf.c        | 9 ++++++++-
 tools/lib/bpf/libbpf.h        | 6 ++++++
 tools/lib/bpf/libbpf.map      | 2 ++
 tools/lib/bpf/libbpf_common.h | 6 ++++++
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6e7ec026d944..3e4eaeafea0e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9903,7 +9903,14 @@ bool bpf_program__autoattach(const struct bpf_program *prog)
 	return prog->autoattach;
 }
 
-int bpf_program__set_autoattach(struct bpf_program *prog, bool autoattach)
+COMPAT_VERSION(bpf_program__set_autoattach_deprecated, bpf_program__set_autoattach, LIBBPF_1.0.0)
+void bpf_program__set_autoattach_deprecated(struct bpf_program *prog, bool autoattach)
+{
+	prog->autoattach = autoattach;
+}
+
+DEFAULT_VERSION(bpf_program__set_autoattach_v1_8_0, bpf_program__set_autoattach, LIBBPF_1.8.0)
+int bpf_program__set_autoattach_v1_8_0(struct bpf_program *prog, bool autoattach)
 {
 	if (prog->load_strategy == BPF_PROG_LOAD_STRATEGY_MANUAL)
 		return libbpf_err(-EINVAL);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 5e44bcfa2ca1..8a04d81ccaeb 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -379,6 +379,12 @@ LIBBPF_API bool bpf_program__autoload(const struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_autoload(struct bpf_program *prog, bool autoload);
 LIBBPF_API bool bpf_program__autoattach(const struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_autoattach(struct bpf_program *prog, bool autoattach);
+/* this "specialization" should go away once the deprecation window for
+ * bpf_program__set_autoattach_deprecated() closes
+ */
+LIBBPF_API int bpf_program__set_autoattach_v1_8_0(struct bpf_program *prog, bool autoattach);
+LIBBPF_DEPRECATED_SINCE(1, 8, "use int-returning bpf_program__set_autoattach() instead")
+LIBBPF_API void bpf_program__set_autoattach_deprecated(struct bpf_program *prog, bool autoattach);
 
 struct bpf_insn;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 8def5474885a..999e791d9887 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -465,6 +465,8 @@ LIBBPF_1.8.0 {
 		bpf_program__clone;
 		bpf_program__load;
 		bpf_program__load_strategy;
+		bpf_program__set_autoattach;
+		bpf_program__set_autoattach_deprecated;
 		bpf_program__set_load_strategy;
 		btf__find_by_name_kind_own;
 		btf__new_empty_opts;
diff --git a/tools/lib/bpf/libbpf_common.h b/tools/lib/bpf/libbpf_common.h
index 8fe248e14eb6..12ad4f5f558f 100644
--- a/tools/lib/bpf/libbpf_common.h
+++ b/tools/lib/bpf/libbpf_common.h
@@ -36,6 +36,12 @@
 #define __LIBBPF_MARK_DEPRECATED_1_0(X)
 #endif
 
+#if __LIBBPF_CURRENT_VERSION_GEQ(1, 8)
+#define __LIBBPF_MARK_DEPRECATED_1_8(X) X
+#else
+#define __LIBBPF_MARK_DEPRECATED_1_8(X)
+#endif
+
 /* This set of internal macros allows to do "function overloading" based on
  * number of arguments provided by used in backwards-compatible way during the
  * transition to libbpf 1.0
-- 
2.34.1