From 7e99c034f788128c7d168eaf27af9a3acaa06163 Mon Sep 17 00:00:00 2001
From: Alex Richardson <arichardson@FreeBSD.org>
Date: Wed, 20 Jan 2021 09:54:46 +0000
Subject: [PATCH] Emit uprintf() output for initproc if there is no controlling
 terminal

This patch helped me debug why /sbin/init was not being loaded after
making changes to the image activator in CheriBSD.

Reviewed By:	jhb (earlier version), kib
Differential Revision: https://reviews.freebsd.org/D28121
---
 sys/kern/subr_prf.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sys/kern/subr_prf.c b/sys/kern/subr_prf.c
index 31117c4e341..b51213a25d0 100644
--- a/sys/kern/subr_prf.c
+++ b/sys/kern/subr_prf.c
@@ -179,6 +179,14 @@ uprintf(const char *fmt, ...)
 	if (TD_IS_IDLETHREAD(td))
 		return (0);
 
+	if (td->td_proc == initproc) {
+		/* Produce output when we fail to load /sbin/init: */
+		va_start(ap, fmt);
+		retval = vprintf(fmt, ap);
+		va_end(ap);
+		return (retval);
+	}
+
 	sx_slock(&proctree_lock);
 	p = td->td_proc;
 	PROC_LOCK(p);