v4.19.13 snapshot.
diff --git a/tools/lib/subcmd/run-command.h b/tools/lib/subcmd/run-command.h
new file mode 100644
index 0000000..17d969c
--- /dev/null
+++ b/tools/lib/subcmd/run-command.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SUBCMD_RUN_COMMAND_H
+#define __SUBCMD_RUN_COMMAND_H
+
+#include <unistd.h>
+
+enum {
+ ERR_RUN_COMMAND_FORK = 10000,
+ ERR_RUN_COMMAND_EXEC,
+ ERR_RUN_COMMAND_PIPE,
+ ERR_RUN_COMMAND_WAITPID,
+ ERR_RUN_COMMAND_WAITPID_WRONG_PID,
+ ERR_RUN_COMMAND_WAITPID_SIGNAL,
+ ERR_RUN_COMMAND_WAITPID_NOEXIT,
+};
+#define IS_RUN_COMMAND_ERR(x) (-(x) >= ERR_RUN_COMMAND_FORK)
+
+struct child_process {
+ const char **argv;
+ pid_t pid;
+ /*
+ * Using .in, .out, .err:
+ * - Specify 0 for no redirections (child inherits stdin, stdout,
+ * stderr from parent).
+ * - Specify -1 to have a pipe allocated as follows:
+ * .in: returns the writable pipe end; parent writes to it,
+ * the readable pipe end becomes child's stdin
+ * .out, .err: returns the readable pipe end; parent reads from
+ * it, the writable pipe end becomes child's stdout/stderr
+ * The caller of start_command() must close the returned FDs
+ * after it has completed reading from/writing to it!
+ * - Specify > 0 to set a channel to a particular FD as follows:
+ * .in: a readable FD, becomes child's stdin
+ * .out: a writable FD, becomes child's stdout/stderr
+ * .err > 0 not supported
+ * The specified FD is closed by start_command(), even in case
+ * of errors!
+ */
+ int in;
+ int out;
+ int err;
+ const char *dir;
+ const char *const *env;
+ unsigned no_stdin:1;
+ unsigned no_stdout:1;
+ unsigned no_stderr:1;
+ unsigned exec_cmd:1; /* if this is to be external sub-command */
+ unsigned stdout_to_stderr:1;
+ void (*preexec_cb)(void);
+};
+
+int start_command(struct child_process *);
+int finish_command(struct child_process *);
+int run_command(struct child_process *);
+
+#define RUN_COMMAND_NO_STDIN 1
+#define RUN_EXEC_CMD 2 /*If this is to be external sub-command */
+#define RUN_COMMAND_STDOUT_TO_STDERR 4
+int run_command_v_opt(const char **argv, int opt);
+
+#endif /* __SUBCMD_RUN_COMMAND_H */