dumb workaround PR/55384 https://twitter.com/tsutsuii/status/1537079628988547073

sysinst_check-ondisk-label-even-if-DISKLABEL_NO_ONDISK_VERIFY-is-specified.diff

Index: usr.sbin/sysinst/disklabel.c
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/disklabel.c,v
retrieving revision 1.44
diff -u -p -d -r1.44 disklabel.c
--- usr.sbin/sysinst/disklabel.c	8 Aug 2021 21:50:10 -0000	1.44
+++ usr.sbin/sysinst/disklabel.c	15 Jun 2022 16:31:13 -0000
@@ -198,16 +198,7 @@ disklabel_parts_read(const char *disk, d
 	int fd;
 	char diskpath[MAXPATHLEN];
 	uint flags;
-#ifndef DISKLABEL_NO_ONDISK_VERIFY
-	bool have_raw_label = false;
-
-	/*
-	 * Verify we really have a disklabel.
-	 */
-	if (run_program(RUN_SILENT | RUN_ERROR_OK,
-	    "disklabel -r %s", disk) == 0)
-		have_raw_label = true;
-#endif
+	bool have_ondisk_label;
 
 	/* read partitions */
 
@@ -304,8 +295,52 @@ disklabel_parts_read(const char *disk, d
 	}
 	close(fd);
 
+	/*
+	 * Verify we really have a disklabel on the target disk.
+	 */
 #ifndef DISKLABEL_NO_ONDISK_VERIFY
-	if (!have_raw_label) {
+	have_ondisk_label = false;
+	if (run_program(RUN_SILENT | RUN_ERROR_OK,
+	    "disklabel -r %s", disk) == 0)
+		have_ondisk_label = true;
+#else
+	/*
+	 * disklabel(8) -r checks a native disklabel at LABELOFFSET sector,
+	 * but several ports don't have a native label and use emulated one
+	 * translated from port specific MD disk partition information.
+	 * Unfortunately, there is no MI way to check whether the disk has
+	 * a native BSD disklabel by readdisklabel(9) via DIOCGDINFO.
+	 * So check if returned label looks defaults set by readdisklabel(9).
+	 *
+	 * XXX these should be checked in MD hook functions.
+	 */
+
+	/* assume we have a label by default */
+	have_ondisk_label = true;
+
+	/* check default values on amiga */
+	if (parts->l.d_npartitions == RAW_PART + 1 &&
+	    parts->l.d_partitions[RAW_PART].p_size == 0x1fffffff &&
+	    parts->l.d_partitions[0].p_size ==
+	     parts->l.d_partitions[RAW_PART].p_size &&
+	    parts->l.d_partitions[0].p_offset == 0 &&
+	    parts->l.d_partitions[0].p_fstype == FS_BSDFFS) {
+		have_ondisk_label = false;
+	}
+
+	/* XXX maybe we should also check mac68k with Apple Partition Map */
+
+	/* check default values on x68k */
+	if (parts->l.d_npartitions == RAW_PART + 1 &&
+	    parts->l.d_partitions[0].p_size ==
+	     parts->l.d_partitions[RAW_PART].p_size &&
+	    parts->l.d_partitions[0].p_fstype == FS_UNUSED &&
+	    parts->l.d_bbsize == 0 && parts->l.d_sbsize == 0) {
+		have_ondisk_label = false;
+	}
+#endif
+
+	if (!have_ondisk_label) {
 		bool found_real_part = false;
 
 		if (parts->l.d_npartitions <= RAW_PART ||
@@ -338,7 +373,6 @@ no_valid_label:
 			return NULL;
 		}
 	}
-#endif
 
 	return &parts->dp;
 }