[PATCH v2 4/9] tools subcmd: Add a no exec function call option

[Ian Rogers <irogers@google.com>]

Tools like perf fork tests in case they crash, but they don't want to
exec a full binary. Add an option to call a function rather than do an
exec. The child process exits with the result of the function call and
is passed the struct of the run_command, things like container_of can
then allow the child process function to determine additional
arguments.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/lib/subcmd/run-command.c | 2 ++
 tools/lib/subcmd/run-command.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/tools/lib/subcmd/run-command.c b/tools/lib/subcmd/run-command.c
index 5cdac2162532..d435eb42354b 100644
--- a/tools/lib/subcmd/run-command.c
+++ b/tools/lib/subcmd/run-command.c
@@ -122,6 +122,8 @@ int start_command(struct child_process *cmd)
 		}
 		if (cmd->preexec_cb)
 			cmd->preexec_cb();
+		if (cmd->no_exec_cmd)
+			exit(cmd->no_exec_cmd(cmd));
 		if (cmd->exec_cmd) {
 			execv_cmd(cmd->argv);
 		} else {
diff --git a/tools/lib/subcmd/run-command.h b/tools/lib/subcmd/run-command.h
index 17d969c6add3..d794138a797f 100644
--- a/tools/lib/subcmd/run-command.h
+++ b/tools/lib/subcmd/run-command.h
@@ -47,6 +47,8 @@ struct child_process {
 	unsigned exec_cmd:1; /* if this is to be external sub-command */
 	unsigned stdout_to_stderr:1;
 	void (*preexec_cb)(void);
+	 /* If set, call function in child rather than doing an exec. */
+	int (*no_exec_cmd)(struct child_process *process);
 };
 
 int start_command(struct child_process *);
-- 
2.43.0.429.g432eaa2c6b-goog