[PATCH bpf-next v2 10/21] bpf: Shrink CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS guard scope for bpf_tracing_multi_attach()

[Leon Hwang <leon.hwang@linux.dev>]

When adding tracing_multi link support for bpf progs, it will use the same
UAPI of the tracing_multi link for kernel functions in
bpf_tracing_multi_attach().

However, the tracing_multi link support for bpf progs does not require
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS. So, shrink its guard scope to add
new code in bpf_tracing_multi_attach() for the tracing_multi link support
for bpf progs.

To simplify the change, validate CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS only
here, because the execution path in trampoline of the tracing_multi link
support for kernel functions is already guarded with the
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS and
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS.

Meanwhile, provide a stub of bpf_trampoline_multi_detach() out of the
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS and
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS guard.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/trampoline.c  |  5 +++++
 kernel/trace/bpf_trace.c | 15 +++------------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index e57c687955fd..6e18f69a63ad 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -1867,6 +1867,11 @@ void bpf_trampoline_multi_detach(struct bpf_prog *prog,
 #undef for_each_mnode_cnt
 #undef for_each_mnode
 
+#else
+
+void bpf_trampoline_multi_detach(struct bpf_prog *prog,
+				 struct bpf_tracing_multi_link *link) {}
+
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS &&
 	  CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS &&
 	  CONFIG_BPF_SYSCALL */
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 195f78db9bda..69559158ab0b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3679,9 +3679,6 @@ __bpf_kfunc int bpf_copy_from_user_task_str_dynptr(const struct bpf_dynptr *dptr
 
 __bpf_kfunc_end_defs();
 
-#if defined(CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS) && \
-    defined(CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS)
-
 static void bpf_tracing_multi_link_release(struct bpf_link *link)
 {
 	struct bpf_tracing_multi_link *tr_link =
@@ -3858,6 +3855,9 @@ int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
 	if (attr->link_create.flags || attr->link_create.target_fd)
 		return -EINVAL;
 
+	if (!IS_ENABLED(CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS))
+		return -EOPNOTSUPP;
+
 	ids = kvmalloc_objs(*ids, cnt);
 	if (!ids)
 		return -ENOMEM;
@@ -3924,12 +3924,3 @@ int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
 	kvfree(link);
 	return err;
 }
-
-#else
-
-int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
-{
-	return -EOPNOTSUPP;
-}
-
-#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS && CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS */
-- 
2.55.0