tools lib bpf: Add bpf_prog_{attach,detach}

Commit d8c5b17 ("samples: bpf: add userspace example for attaching
eBPF programs to cgroups") added these functions to samples/libbpf, but
during this merge all of the samples libbpf functionality is shifting to
tools/lib/bpf. Shift these functions there.

Signed-off-by: Joe Stringer <joe@ovn.org>
---
Arnaldo, this is a new patch you didn't previously review which I've
prepared due to the conflict with net-next. I figured it's better to try
to get samples/bpf properly switched over this window rather than defer the
problem and end up having to deal with another merge problem next time
around. I hope that is fine for you.

It's a simple copy/paste/delete with a minor change for sys_bpf() vs
syscall().

samples/bpf/libbpf.c

@@ -11,27 +11,6 @@
 #include <arpa/inet.h>
 #include "libbpf.h"
 
-int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type)
-{
-	union bpf_attr attr = {
-		.target_fd = target_fd,
-		.attach_bpf_fd = prog_fd,
-		.attach_type = type,
-	};
-
-	return syscall(__NR_bpf, BPF_PROG_ATTACH, &attr, sizeof(attr));
-}
-
-int bpf_prog_detach(int target_fd, enum bpf_attach_type type)
-{
-	union bpf_attr attr = {
-		.target_fd = target_fd,
-		.attach_type = type,
-	};
-
-	return syscall(__NR_bpf, BPF_PROG_DETACH, &attr, sizeof(attr));
-}
-
 int open_raw_sock(const char *name)
 {
 	struct sockaddr_ll sll;

samples/bpf/libbpf.h

@@ -6,9 +6,6 @@
 
 struct bpf_insn;
 
-int bpf_prog_attach(int prog_fd, int attachable_fd, enum bpf_attach_type type);
-int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);
-
 /* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */
 
 #define BPF_ALU64_REG(OP, DST, SRC)				\

tools/lib/bpf/bpf.c

@@ -167,3 +167,24 @@ int bpf_obj_get(const char *pathname)
 
 	return sys_bpf(BPF_OBJ_GET, &attr, sizeof(attr));
 }
+
+int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type)
+{
+	union bpf_attr attr = {
+		.target_fd = target_fd,
+		.attach_bpf_fd = prog_fd,
+		.attach_type = type,
+	};
+
+	return sys_bpf(BPF_PROG_ATTACH, &attr, sizeof(attr));
+}
+
+int bpf_prog_detach(int target_fd, enum bpf_attach_type type)
+{
+	union bpf_attr attr = {
+		.target_fd = target_fd,
+		.attach_type = type,
+	};
+
+	return sys_bpf(BPF_PROG_DETACH, &attr, sizeof(attr));
+}

tools/lib/bpf/bpf.h

@@ -41,5 +41,8 @@ int bpf_map_delete_elem(int fd, void *key);
 int bpf_map_get_next_key(int fd, void *key, void *next_key);
 int bpf_obj_pin(int fd, const char *pathname);
 int bpf_obj_get(const char *pathname);
+int bpf_prog_attach(int prog_fd, int attachable_fd, enum bpf_attach_type type);
+int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);
+
 
 #endif