bpf: Extend sys_bpf commands for bpf_syscall programs.

bpf_sycall programs can be used directly by the kernel modules
to load programs and create maps via kernel skeleton.
. Export bpf_sys_bpf syscall wrapper to be used in kernel skeleton.
. Export bpf_map_get to be used in kernel skeleton.
. Allow prog_run cmd for bpf_syscall programs with recursion check.
. Enable link_create and raw_tp_open cmds.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220209232001.27490-2-alexei.starovoitov@gmail.com

Author: Alexei Starovoitov

kernel/bpf/syscall.c

@@ -985,6 +985,7 @@ struct bpf_map *bpf_map_get(u32 ufd)
 
 	return map;
 }
+EXPORT_SYMBOL(bpf_map_get);
 
 struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 {
@@ -4756,23 +4757,52 @@ static bool syscall_prog_is_valid_access(int off, int size,
 	return true;
 }
 
-BPF_CALL_3(bpf_sys_bpf, int, cmd, void *, attr, u32, attr_size)
+BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
 {
+	struct bpf_prog * __maybe_unused prog;
+
 	switch (cmd) {
 	case BPF_MAP_CREATE:
 	case BPF_MAP_UPDATE_ELEM:
 	case BPF_MAP_FREEZE:
 	case BPF_PROG_LOAD:
 	case BPF_BTF_LOAD:
+	case BPF_LINK_CREATE:
+	case BPF_RAW_TRACEPOINT_OPEN:
 		break;
-	/* case BPF_PROG_TEST_RUN:
-	 * is not part of this list to prevent recursive test_run
-	 */
+#ifdef CONFIG_BPF_JIT /* __bpf_prog_enter_sleepable used by trampoline and JIT */
+	case BPF_PROG_TEST_RUN:
+		if (attr->test.data_in || attr->test.data_out ||
+		    attr->test.ctx_out || attr->test.duration ||
+		    attr->test.repeat || attr->test.flags)
+			return -EINVAL;
+
+		prog = bpf_prog_get_type(attr->test.prog_fd, BPF_PROG_TYPE_SYSCALL);
+		if (IS_ERR(prog))
+			return PTR_ERR(prog);
+
+		if (attr->test.ctx_size_in < prog->aux->max_ctx_offset ||
+		    attr->test.ctx_size_in > U16_MAX) {
+			bpf_prog_put(prog);
+			return -EINVAL;
+		}
+
+		if (!__bpf_prog_enter_sleepable(prog)) {
+			/* recursion detected */
+			bpf_prog_put(prog);
+			return -EBUSY;
+		}
+		attr->test.retval = bpf_prog_run(prog, (void *) (long) attr->test.ctx_in);
+		__bpf_prog_exit_sleepable(prog, 0 /* bpf_prog_run does runtime stats */);
+		bpf_prog_put(prog);
+		return 0;
+#endif
 	default:
 		return -EINVAL;
 	}
 	return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
 }
+EXPORT_SYMBOL(bpf_sys_bpf);
 
 static const struct bpf_func_proto bpf_sys_bpf_proto = {
 	.func		= bpf_sys_bpf,