[PATCH net-next] bpf/tracing: fix kernel/events/core.c compilation error

[Yonghong Song <yhs@fb.com>]

Commit f371b304f12e ("bpf/tracing: allow user space to
query prog array on the same tp") introduced a perf
ioctl command to query prog array attached to the
same perf tracepoint. The commit introduced a
compilation error when either CONFIG_BPF_SYSCALL or
CONFIG_EVENT_TRACING is not defined:
  kernel/events/core.o: In function `perf_ioctl':
  core.c:(.text+0x98c4): undefined reference to `bpf_event_query_prog_array'

This patch fixed this error.

Fixes: f371b304f12e ("bpf/tracing: allow user space to query prog array on the same tp")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 include/linux/bpf.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 93e15b9..8dbbfd7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -254,7 +254,6 @@ typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
 
 u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy);
-int bpf_event_query_prog_array(struct perf_event *event, void __user *info);
 
 int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 			  union bpf_attr __user *uattr);
@@ -558,6 +557,15 @@ static inline int sock_map_prog(struct bpf_map *map,
 }
 #endif
 
+#if defined(CONFIG_EVENT_TRACING) && defined(CONFIG_BPF_SYSCALL)
+int bpf_event_query_prog_array(struct perf_event *event, void __user *info);
+#else
+static inline int bpf_event_query_prog_array(struct perf_event *event, void __user *info)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 /* verifier prototypes for helper functions called from eBPF programs */
 extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
 extern const struct bpf_func_proto bpf_map_update_elem_proto;
-- 
2.9.5