From a17b2361ce87dfbf3d5e3df72c4d77d0df1d35eb Mon Sep 17 00:00:00 2001
From: krw <krw@openbsd.org>
Date: Mon, 24 Apr 2023 14:06:01 +0000
Subject: [PATCH] Add '-s' option to simply display the number of bytes
 available for the rdroot filesystem in the specified kernel.

No behaviour change to existing uses of rdsetroot.

Improved option handling & ok kn@
---
 usr.sbin/rdsetroot/rdsetroot.8 | 10 ++++++++--
 usr.sbin/rdsetroot/rdsetroot.c | 21 +++++++++++++++++----
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/usr.sbin/rdsetroot/rdsetroot.8 b/usr.sbin/rdsetroot/rdsetroot.8
index 9ec02988dff..0457b1b4d24 100644
--- a/usr.sbin/rdsetroot/rdsetroot.8
+++ b/usr.sbin/rdsetroot/rdsetroot.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: rdsetroot.8,v 1.3 2023/01/20 17:15:22 kn Exp $
+.\"	$OpenBSD: rdsetroot.8,v 1.4 2023/04/24 14:06:01 krw Exp $
 .\"
 .\" Copyright (c) 2019 Theo de Raadt
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: January 20 2023 $
+.Dd $Mdocdate: April 24 2023 $
 .Dt RDSETROOT 8
 .Os
 .Sh NAME
@@ -22,6 +22,9 @@
 .Nd insert disk image into RAMDISK kernel
 .Sh SYNOPSIS
 .Nm rdsetroot
+.Fl s
+.Ar kernel
+.Nm rdsetroot
 .Op Fl dx
 .Ar kernel
 .Op Ar disk.fs
@@ -41,6 +44,9 @@ The options are as follows:
 .Bl -tag -width Ds
 .It Fl d
 Debug.
+.It Fl s
+Print the size in bytes of the reserved space in the RAMDISK kernel.
+No insertion or extraction is attempted.
 .It Fl x
 Rather than inserting, extract the
 .Ar disk.fs
diff --git a/usr.sbin/rdsetroot/rdsetroot.c b/usr.sbin/rdsetroot/rdsetroot.c
index fc2e7e0940d..bbb8701fb66 100644
--- a/usr.sbin/rdsetroot/rdsetroot.c
+++ b/usr.sbin/rdsetroot/rdsetroot.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: rdsetroot.c,v 1.4 2023/01/20 17:15:22 kn Exp $ */
+/* $OpenBSD: rdsetroot.c,v 1.5 2023/04/24 14:06:01 krw Exp $ */
 
 /*
  * Copyright (c) 2019 Sunil Nimmagadda <sunil@openbsd.org>
@@ -47,13 +47,16 @@ main(int argc, char **argv)
 	size_t		 shstrndx, mmap_size;
 	uint64_t	 rd_root_size_off, rd_root_image_off;
 	uint32_t	*ip;
-	int		 ch, debug = 0, fsfd, kfd, n, xflag = 0;
+	int		 ch, debug = 0, fsfd, kfd, n, sflag = 0, xflag = 0;
 
-	while ((ch = getopt(argc, argv, "dx")) != -1) {
+	while ((ch = getopt(argc, argv, "dsx")) != -1) {
 		switch (ch) {
 		case 'd':
 			debug = 1;
 			break;
+		case 's':
+			sflag = 1;
+			break;
 		case 'x':
 			xflag = 1;
 			break;
@@ -64,6 +67,9 @@ main(int argc, char **argv)
 	argc -= optind;
 	argv += optind;
 
+	if (sflag && (debug || xflag || argc > 1))
+		usage();
+
 	if (argc == 1)
 		kernel = argv[0];
 	else if (argc == 2) {
@@ -161,6 +167,11 @@ main(int argc, char **argv)
 	 */
 	ip = (uint32_t *) (dataseg + rd_root_size_off);
 	rd_root_size_val = *ip;
+	if (sflag) {
+		fprintf(stdout, "%llu\n", (unsigned long long)rd_root_size_val);
+		goto done;
+	}
+
 	if (debug) {
 		fprintf(stderr, "rd_root_size  val: 0x%llx (%lld blocks)\n",
 		    (unsigned long long)rd_root_size_val,
@@ -196,6 +207,7 @@ main(int argc, char **argv)
 	if (debug)
 		fprintf(stderr, "...copied %d bytes\n", n);
 
+ done:
 	elf_end(e);
 	return 0;
 }
@@ -294,6 +306,7 @@ usage(void)
 {
 	extern char *__progname;
 
-	fprintf(stderr, "usage: %s [-dx] kernel [disk.fs]\n", __progname);
+	fprintf(stderr, "usage: %s -s kernel\n", __progname);
+	fprintf(stderr, "       %s [-dx] kernel [disk.fs]\n", __progname);
 	exit(1);
 }
-- 
2.20.1