According to the documentation, when building a kernel with the C=2
parameter, all source files should be checked. But this does not happen
for the kernel/bpf/ directory.

$ touch kernel/bpf/core.o
$ make C=2 CHECK=true kernel/bpf/core.o

Outputs:

  CHECK   scripts/mod/empty.c
  CALL    scripts/checksyscalls.sh
  DESCEND objtool
  INSTALL libsubcmd_headers
  CC      kernel/bpf/core.o

As can be seen the compilation is done, but CHECK is not executed. This
happens because kernel/bpf/Makefile has defined its own rule for
compilation and forgotten the macro that does the check.

There is no need to duplicate the build code, and this rule can be
removed to use generic rules.

Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 kernel/bpf/Makefile       | 6 ------
 kernel/bpf/btf_iter.c     | 2 ++
 kernel/bpf/btf_relocate.c | 2 ++
 kernel/bpf/relo_core.c    | 2 ++
 4 files changed, 6 insertions(+), 6 deletions(-)
 create mode 100644 kernel/bpf/btf_iter.c
 create mode 100644 kernel/bpf/btf_relocate.c
 create mode 100644 kernel/bpf/relo_core.c

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 0291eef9ce92..9b9c151b5c82 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -52,9 +52,3 @@ obj-$(CONFIG_BPF_PRELOAD) += preload/
 obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
 obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o
-
-# Some source files are common to libbpf.
-vpath %.c $(srctree)/kernel/bpf:$(srctree)/tools/lib/bpf
-
-$(obj)/%.o: %.c FORCE
-	$(call if_changed_rule,cc_o_c)
diff --git a/kernel/bpf/btf_iter.c b/kernel/bpf/btf_iter.c
new file mode 100644
index 000000000000..0e2c66a52df9
--- /dev/null
+++ b/kernel/bpf/btf_iter.c
@@ -0,0 +1,2 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#include "../../tools/lib/bpf/btf_iter.c"
diff --git a/kernel/bpf/btf_relocate.c b/kernel/bpf/btf_relocate.c
new file mode 100644
index 000000000000..c12ccbf66507
--- /dev/null
+++ b/kernel/bpf/btf_relocate.c
@@ -0,0 +1,2 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#include "../../tools/lib/bpf/btf_relocate.c"
diff --git a/kernel/bpf/relo_core.c b/kernel/bpf/relo_core.c
new file mode 100644
index 000000000000..aa822c9fcfde
--- /dev/null
+++ b/kernel/bpf/relo_core.c
@@ -0,0 +1,2 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#include "../../tools/lib/bpf/relo_core.c"
-- 
2.46.0