lib/process: Add add_stderr flag to process module

For some process execution functions, we'd like to capture stderr as
well as stdout. Currently, we unconditionally redirect subprocess stderr
to the petitboot log file.

This change adds an add_stderr flag to struct process, which indicates
to the process library that we want stderr as well as stdout. If this is
specified, the subprocess' stderr is captured to stdout_buf.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

2 files changed, 5 insertions, 1 deletions

diff --git a/lib/process/process.c b/lib/process/process.c
index 1a16fb6..3c81b29 100644
--- a/lib/process/process.c
+++ b/lib/process/process.c
@@ -125,7 +125,10 @@ static void process_setup_stdout_child(struct process_info *procinfo)
 	else
 		dup2(log, STDOUT_FILENO);
 
-	dup2(log, STDERR_FILENO);
+	if (procinfo->process.keep_stdout && procinfo->process.add_stderr)
+		dup2(procinfo->stdout_pipe[1], STDERR_FILENO);
+	else
+		dup2(log, STDERR_FILENO);
 }
 
 static void process_finish_stdout(struct process_info *procinfo)
diff --git a/lib/process/process.h b/lib/process/process.h
index caeda92..ae7fe32 100644
--- a/lib/process/process.h
+++ b/lib/process/process.h
@@ -31,6 +31,7 @@ struct process {
 	const char		*path;
 	const char		**argv;
 	bool			keep_stdout;
+	bool			add_stderr;
 	process_exit_cb		exit_cb;
 	void			*data;