[PATCH bpf-next 11/15] bpf: Add bpf_sys_close() helper.

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

From: Alexei Starovoitov <ast@xxxxxxxxxx>

Add bpf_sys_close() helper to be used by the syscall/loader program to close
intermediate FDs and other cleanup.

Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
 include/uapi/linux/bpf.h       |  7 +++++++
 kernel/bpf/syscall.c           | 14 ++++++++++++++
 tools/include/uapi/linux/bpf.h |  7 +++++++
 3 files changed, 28 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 47c4b21a51b6..2251e7894799 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4728,6 +4728,12 @@ union bpf_attr {
  * 		If btf_fd is zero look for the name in vmlinux BTF and kernel module BTFs.
  * 	Return
  * 		Return btf_id and store module's BTF FD into attach_btf_obj_fd.
+ *
+ * long bpf_sys_close(u32 fd)
+ * 	Description
+ * 		Execute close syscall for given FD.
+ * 	Return
+ * 		A syscall result.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4897,6 +4903,7 @@ union bpf_attr {
 	FN(for_each_map_elem),		\
 	FN(sys_bpf),			\
 	FN(btf_find_by_name_kind),	\
+	FN(sys_close),			\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6d4d9925c0ec..822b00908c58 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4557,6 +4557,18 @@ const struct bpf_func_proto bpf_sys_bpf_proto = {
 	.arg3_type	= ARG_CONST_SIZE,
 };
 
+BPF_CALL_1(bpf_sys_close, u32, fd)
+{
+	return close_fd(fd);
+}
+
+const struct bpf_func_proto bpf_sys_close_proto = {
+	.func		= bpf_sys_close,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -4565,6 +4577,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_sys_bpf_proto;
 	case BPF_FUNC_btf_find_by_name_kind:
 		return &bpf_btf_find_by_name_kind_proto;
+	case BPF_FUNC_sys_close:
+		return &bpf_sys_close_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 47c4b21a51b6..2251e7894799 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4728,6 +4728,12 @@ union bpf_attr {
  * 		If btf_fd is zero look for the name in vmlinux BTF and kernel module BTFs.
  * 	Return
  * 		Return btf_id and store module's BTF FD into attach_btf_obj_fd.
+ *
+ * long bpf_sys_close(u32 fd)
+ * 	Description
+ * 		Execute close syscall for given FD.
+ * 	Return
+ * 		A syscall result.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4897,6 +4903,7 @@ union bpf_attr {
 	FN(for_each_map_elem),		\
 	FN(sys_bpf),			\
 	FN(btf_find_by_name_kind),	\
+	FN(sys_close),			\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.30.2