savecore: accept device names without the /dev/ prefix

dumpon has accepted device names without the prefix ever since r291207.
Since dumpon and savecore are always paired, they ought to accept the same
arguments. Prior to this change, specifying 'dumpdev="da3"' in
/etc/rc.conf, for example, would result in dumpon working just fine but
savecore complaining that "Dump device does not exist".

PR:		247618
Reviewed by:	cem, bcr
MFC after:	2 weeks
Sponsored by:	Axcient
Differential Revision:	https://reviews.freebsd.org/D25500

sbin/savecore/savecore.c

@@ -973,6 +973,44 @@ DoFile(const char *savedir, int savedirfd, const char *device)
 	close(fddev);
 }
 
+/* Prepend "/dev/" to any arguments that don't already have it */
+static char **
+devify(int argc, char **argv)
+{
+	char **devs;
+	int i, l;
+
+	devs = malloc(argc * sizeof(*argv));
+	if (devs == NULL) {
+		logmsg(LOG_ERR, "malloc(): %m");
+		exit(1);
+	}
+	for (i = 0; i < argc; i++) {
+		if (strncmp(argv[i], _PATH_DEV, sizeof(_PATH_DEV) - 1) == 0)
+			devs[i] = strdup(argv[i]);
+		else {
+			char *fullpath;
+
+			fullpath = malloc(PATH_MAX);
+			if (fullpath == NULL) {
+				logmsg(LOG_ERR, "malloc(): %m");
+				exit(1);
+			}
+			l = snprintf(fullpath, PATH_MAX, "%s%s", _PATH_DEV,
+			    argv[i]);
+			if (l < 0) {
+				logmsg(LOG_ERR, "snprintf(): %m");
+				exit(1);
+			} else if (l >= PATH_MAX) {
+				logmsg(LOG_ERR, "device name too long");
+				exit(1);
+			}
+			devs[i] = fullpath;
+		}
+	}
+	return (devs);
+}
+
 static char **
 enum_dumpdevs(int *argcp)
 {
@@ -1069,6 +1107,7 @@ main(int argc, char **argv)
 {
 	cap_rights_t rights;
 	const char *savedir;
+	char **devs;
 	int i, ch, error, savedirfd;
 
 	checkfor = compress = clear = force = keep = verbose = 0;
@@ -1132,7 +1171,9 @@ main(int argc, char **argv)
 		argv++;
 	}
 	if (argc == 0)
-		argv = enum_dumpdevs(&argc);
+		devs = enum_dumpdevs(&argc);
+	else
+		devs = devify(argc, argv);
 
 	savedirfd = open(savedir, O_RDONLY | O_DIRECTORY);
 	if (savedirfd < 0) {
@@ -1148,10 +1189,10 @@ main(int argc, char **argv)
 	}
 
 	/* Enter capability mode. */
-	init_caps(argc, argv);
+	init_caps(argc, devs);
 
 	for (i = 0; i < argc; i++)
-		DoFile(savedir, savedirfd, argv[i]);
+		DoFile(savedir, savedirfd, devs[i]);
 
 	/* Emit minimal output. */
 	if (nfound == 0) {

share/man/man5/rc.conf.5

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 23, 2020
+.Dd June 28, 2020
 .Dt RC.CONF 5
 .Os
 .Sh NAME
@@ -3469,7 +3469,9 @@ the first suitable swap device listed in
 .Pa /etc/fstab
 will be used as dump device.
 Otherwise, the value of this variable is passed as the argument to
-.Xr dumpon 8 .
+.Xr dumpon 8
+and
+.Xr savecore 8 .
 To disable crash dumps, set this variable to
 .Dq Li NO .
 .It Va dumpon_flags